Tag Archives: tissue engineering

Job posting (post doc in tissue engineering [organ-on-a-chip]) for the Istituto Italiano di Technologia

Here’s the posting (deadline is July 19, 2015),

Istituto Italiano di Tecnologia (IIT), Genova, Italy (http://www.iit.it) is a private law Foundation, created with special Government Law no. 269 dated September 30th 2003 with the objective of promoting Italy’s technological development and higher education in science and technology. Research at IIT is carried out in highly innovative scientific fields with state-of-the-art technology.

A post-doc position to develop “Organs-on-Chips” is available in the Laboratory of Nanotechnology for Precision Medicine at IIT.

Candidates should have a PhD in Tissue Engineering or closely related fields and an excellent publication record and should be highly motivated to work in an interdisciplinary team.

The candidate will work on the development of microfluidic-based organs-on-chips.

These microchips will be used to recapitulate the microarchitecture and functions of living organs and pathological tissues such as cancer and will possibly form an accurate alternative to traditional animal testing and enable high-throughput screening of drugs and nanomedicines.

The candidate should have:

  • strong skills in tissue engineering as well as in molecular, cellular and in vivo tumor biology;
  • documented experience in primary cell culture and analysis;
  • excellent oral and written communication skills in English and the ability to work both independently and as part of a multidisciplinary team.

Interested applicants should contact directly Dr. Paolo Decuzzi ( paolo.decuzzi@iit.it) for any informal queries.

For a formal application  please send CV, list of publications with Impact Factor and names and email addresses of 2 referees to applications@iit.it

Please apply by July 19, 2015 quoting “Post doc position in Tissue Engineering” in the mail subject. [emphasis mine]

In order to comply with Italian law (art. 23 of Privacy Law of the Italian Legislative Decree n. 196/03), the candidate is kindly asked to give his/her consent to allow Istituto Italiano di Tecnologia to process his/her personal data.

We inform you that the information you provide will be solely used for the purpose of evaluating and selecting candidates in order to meet the requirements of Istituto Italiano di Tecnologia.

Your data will be processed by Istituto Italiano di Tecnologia, with its headquarters in Genoa, Via Morego 30, acting as the Data Holder, using computer and paper-based means, observing the rules on the protection of personal data, including those relating to the security of data, and they will not be communicated to thirds.

Please also note that, pursuant to art.7 of Legislative Decree 196/2003, you may exercise your rights at any time as a party concerned by contacting the Data Holder.

Istituto Italiano di Tecnologia is an Equal Opportunity Employer that actively seeks diversity in the workforce.

Don’t forget when preparing your application, should you be living on the West Coast of Canada or the US (not sure about Mexico as its coast veers east somewhat), Italy is +9 hours . This means you’d best get your application submitted by 3 pm PST on July 19, 2015.

Synthesizing nerve tissues with 3D printers and cellulose nanocrystals (CNC)

There are lots of stories about bioprinting and tissue engineering here and I think it’s time (again) for one which one has some good, detailed descriptions and, bonus, it features cellulose nanocrystals (CNC) and graphene. From a May 13, 2015 news item on Azonano,

The printer looks like a toaster oven with the front and sides removed. Its metal frame is built up around a stainless steel circle lit by an ultraviolet light. Stainless steel hydraulics and thin black tubes line the back edge, which lead to an inner, topside box made of red plastic.

In front, the metal is etched with the red Bio Bot logo. All together, the gray metal frame is small enough to fit on top of an old-fashioned school desk, but nothing about this 3D printer is old school. In fact, the tissue-printing machine is more like a sci-fi future in the flesh—and it has very real medical applications.

Researchers at Michigan Technological University hope to use this newly acquired 3D bioprinter to make synthesized nerve tissue. The key is developing the right “bioink” or printable tissue. The nanotechnology-inspired material could help regenerate damaged nerves for patients with spinal cord injuries, says Tolou Shokuhfar, an assistant professor of mechanical engineering and biomedical engineering at Michigan Tech.

Shokuhfar directs the In-Situ Nanomedicine and Nanoelectronics Laboratory at Michigan Tech, and she is an adjunct assistant professor in the Bioengineering Department and the College of Dentistry at the University of Illinois at Chicago.

In the bioprinting research, Shokuhfar collaborates with Reza Shahbazian-Yassar, the Richard and Elizabeth Henes Associate Professor in the Department of Mechanical Engineering-Engineering Mechanics at Michigan Tech. Shahbazian-Yassar’s highly interdisciplinary background on cellulose nanocrystals as biomaterials, funded by the National Science Foundation’s (NSF) Biomaterials Program, helped inspire the lab’s new 3D printing research. “Cellulose nanocrystals with extremely good mechanical properties are highly desirable for bioprinting of scaffolds that can be used for live tissues,” says Shahbazian-Yassar. [emphases mine]

A May 11, 2015 Michigan Technological University (MTU) news release by Allison Mills, which originated the news item, explains the ‘why’ of the research,

“We wanted to target a big issue,” Shokuhfar says, explaining that nerve regeneration is a particularly difficult biomedical engineering conundrum. “We are born with all the nerve cells we’ll ever have, and damaged nerves don’t heal very well.”

Other facilities are trying to address this issue as well. Many feature large, room-sized machines that have built-in cell culture hoods, incubators and refrigeration. The precision of this equipment allows them to print full organs. But innovation is more nimble at smaller scales.

“We can pursue nerve regeneration research with a simpler printer set-up,” says Shayan Shafiee, a PhD student working with Shokuhfar. He gestures to the small gray box across the lab bench.

He opens the red box under the top side of the printer’s box. Inside the plastic casing, a large syringe holds a red jelly-like fluid. Shafiee replenishes the needle-tipped printer, pulls up his laptop and, with a hydraulic whoosh, he starts to print a tissue scaffold.

The news release expands on the theme,

At his lab bench in the nanotechnology lab at Michigan Tech, Shafiee holds up a petri dish. Inside is what looks like a red gummy candy, about the size of a half-dollar.

Here’s a video from MTU illustrating the printing process,

Back to the news release, which notes graphene could be instrumental in this research,

“This is based on fractal geometry,” Shafiee explains, pointing out the small crenulations and holes pockmarking the jelly. “These are similar to our vertebrae—the idea is to let a nerve pass through the holes.”

Making the tissue compatible with nerve cells begins long before the printer starts up. Shafiee says the first step is to synthesize a biocompatible polymer that is syrupy—but not too thick—that can be printed. That means Shafiee and Shokuhfar have to create their own materials to print with; there is no Amazon.com or even a specialty shop for bioprinting nerves.

Nerves don’t just need a biocompatible tissue to act as a carrier for the cells. Nerve function is all about electric pulses. This is where Shokuhfar’s nanotechnology research comes in: Last year, she was awarded a CAREER grant from NSF for her work using graphene in biomaterials research. [emphasis mine] “Graphene is a wonder material,” she says. “And it has very good electrical conductivity properties.”

The team is extending the application of this material for nerve cell printing. “Our work always comes back to the question, is it printable or not?” Shafiee says, adding that a successful material—a biocompatible, graphene-bound polymer—may just melt, mush or flat out fail under the pressure of printing. After all, imagine building up a substance more delicate than a soufflé using only the point of a needle. And in the nanotechnology world, a needlepoint is big, even clumsy.

Shafiee and Shokuhfar see these issues as mechanical obstacles that can be overcome.

“It’s like other 3D printers, you need a design to work from,” Shafiee says, adding that he will tweak and hone the methodology for printing nerve cells throughout his dissertation work. He is also hopeful that the material will have use beyond nerve regeneration.

This looks like a news release designed to publicize work funded at MTU by the US National Science Foundation (NSF) which is why there is no mention of published work.

One final comment regarding cellulose nanocrystals (CNC). They have also been called nanocrystalline cellulose (NCC), which you will still see but it seems CNC is emerging as the generic term. NCC has been trademarked by CelluForce, a Canadian company researching and producing CNC (or if you prefer, NCC) from forest products.

Making 3D patches for the brain

They’re not ready to start patching any brains yet but the research seems promising. From an April 1, 2015 news item on ScienceDaily,

Damage to neural tissue is typically permanent and causes lasting disability in patients, but a new approach has recently been discovered that holds incredible potential to reconstruct neural tissue at high resolution in three dimensions. Research recently published in the Journal of Neural Engineering demonstrated a method for embedding scaffolding of patterned nanofibers within three-dimensional (3D) hydrogel structures, and it was shown that neurite outgrowth from neurons in the hydrogel followed the nanofiber scaffolding by tracking directly along the nanofibers, particularly when the nanofibers were coated with a type of cell adhesion molecule called laminin. It was also shown that the coated nanofibers significantly enhanced the length of growing neurites, and that the type of hydrogel could significantly affect the extent to which the neurites tracked the nanofibers.

A March 31, 2015 Institute of Neural Regeneration & Tissue Engineering press release on EurekAlert, which originated the news item, describes the thinking underlying this research and future research plans,

“Neural stem cells hold incredible potential for restoring damaged cells in the nervous system, and 3D reconstruction of neural tissue is essential for replicating the complex anatomical structure and function of the brain and spinal cord,” said Dr. McMurtrey, author of the study and director of the research institute that led this work. “So it was thought that the combination of induced neuronal cells with micropatterned biomaterials might enable unique advantages in 3D cultures, and this research showed that not only can neuronal cells be cultured in 3D conformations, but the direction and pattern of neurite outgrowth can be guided and controlled using relatively simple combinations of structural cues and biochemical signaling factors.”

The next step will be replicating more complex structures using a patient’s own induced stem cells to reconstruct damaged or diseased sites in the nervous system. These 3D reconstructions can then be used to implant into the damaged areas of neural tissue to help reconstruct specific neuroanatomical structures and integrate with the proper neural circuitry in order to restore function. Successful restoration of function would require training of the new neural circuitry over time, but by selecting the proper neurons and forming them into native architecture, implanted neural stem cells would have a much higher chance of providing successful outcomes. The scaffolding and hydrogel materials are biocompatible and biodegradable, and the hydrogels can also help to maintain the microstructure of implanted cells and prevent them from washing away in the cerebrospinal fluid that surrounds the brain and spinal cord.

McMurtrey also noted that by making these site-specific reconstructions of neural tissue, not only can neural architecture be rebuilt, but researchers can also make models for studying disease mechanisms and developmental processes just by using skin cells that are induced into pluripotent stem cells and into neurons from patients with a variety of diseases and conditions. “The 3D constructs enable a realistic replication of the innate cellular environment and also enable study of diseased human neurons without needing to biopsy neurons from affected patients and without needing to make animal models that can fail to replicate the full array of features seen in humans,” said McMurtrey.

The ability to engineer neural tissue from stem cells and biomaterials holds great potential for regenerative medicine. The combination of stem cells, functionalized hydrogel architecture, and patterned and functionalized nanofiber scaffolding enables the formation of unique 3D tissue constructs, and these engineered constructs offer important applications in brain and spinal cord tissue that has been damaged by trauma, stroke, or degeneration. In particular, this work may one day help in the restoration of functional neuroanatomical pathways and structures at sites of spinal cord injury, traumatic brain injury, tumor resection, stroke, or neurodegenerative diseases of Parkinson’s, Huntington’s, Alzheimer’s, or amyotrophic lateral sclerosis.

Here’s a link to and a citation for the paper,

Patterned and functionalized nanofiber scaffolds in three-dimensional hydrogel constructs enhance neurite outgrowth and directional control by Richard McMurtrey (Journal of Neural Engineering Volume 11 Number 6) 2014 J. J. Neural Eng. 11 066009 doi:10.1088/1741-2560/11/6/066009

This paper is open access.

A little unusually for me, here’s the abstract for the paper,

Objective. Neural tissue engineering holds incredible potential to restore functional capabilities to damaged neural tissue. It was hypothesized that patterned and functionalized nanofiber scaffolds could control neurite direction and enhance neurite outgrowth. Approach. A method of creating aligned electrospun nanofibers was implemented and fiber characteristics were analyzed using environmental scanning electron microscopy. Nanofibers were composed of polycaprolactone (PCL) polymer, PCL mixed with gelatin, or PCL with a laminin coating. Three-dimensional hydrogels were then integrated with embedded aligned nanofibers to support neuronal cell cultures. Microscopic images were captured at high-resolution in single and multi-focal planes with eGFP-expressing neuronal SH-SY5Y cells in a fluorescent channel and nanofiber scaffolding in another channel. Neuronal morphology and neurite tracking of nanofibers were then analyzed in detail. Main results. Aligned nanofibers were shown to enable significant control over the direction of neurite outgrowth in both two-dimensional (2D) and three-dimensional (3D) neuronal cultures. Laminin-functionalized nanofibers in 3D hyaluronic acid (HA) hydrogels enabled significant alignment of neurites with nanofibers, enabled significant neurite tracking of nanofibers, and significantly increased the distance over which neurites could extend. Specifically, the average length of neurites per cell in 3D HA constructs with laminin-functionalized nanofibers increased by 66% compared to the same laminin fibers on 2D laminin surfaces, increased by 59% compared to 2D laminin-coated surface without fibers, and increased by 1052% compared to HA constructs without fibers. Laminin functionalization of fibers also doubled average neurite length over plain PCL fibers in the same 3D HA constructs. In addition, neurites also demonstrated tracking directly along the fibers, with 66% of neurite lengths directly tracking laminin-coated fibers in 3D HA constructs, which was a 65% relative increase in neurite tracking compared to plain PCL fibers in the same 3D HA constructs and a 213% relative increase over laminin-coated fibers on 2D laminin-coated surfaces. Significance. This work demonstrates the ability to create unique 3D neural tissue constructs using a combined system of hydrogel and nanofiber scaffolding. Importantly, patterned and biofunctionalized nanofiber scaffolds that can control direction and increase length of neurite outgrowth in three-dimensions hold much potential for neural tissue engineering. This approach offers advancements in the development of implantable neural tissue constructs that enable control of neural development and reproduction of neuroanatomical pathways, with the ultimate goal being the achievement of functional neural regeneration.

I have a few comments, this work was performed in vitro and I imagine it will be several years before it is attempted in human clinical trials. As well, the ethics issues raised by this work are interesting. While the doctors are talking about repairs to injured tissues, it’s only a matter of time until someone tries to improve on the brain or human enhancement. After all, modern plastic surgery was developed as a form of repair for soldiers and others who were disfigured. These days, much of the practice is concerned with preserving youth or enhancing someone’s looks. Not altogether coincidentally, I wrote about the second volume of a report from the US Presidential Bioethics Commission in my April 2, 2015 post titled: Gray Matters volume 2: Integrative Approaches for Neuroscience, Ethics, and Society issued March 2015 by US Presidential Bioethics Commission.

Finally, you can find out more about the Institute of Neural Regeneration & Tissue Engineering here.

Engineering a small intestine

Researchers at the Children’s Hospital Los Angeles (CHLA) have successfully engineered small intestines that appear to be functional when transplanted into mice according to a Jan. 8, 2015 news item on ScienceDaily,

A new study by researchers at Children’s Hospital Los Angeles has shown that tissue-engineered small intestine grown from human cells replicates key aspects of a functioning human intestine. The tissue-engineered small intestine they developed contains important elements of the mucosal lining and support structures, including the ability to absorb sugars, and even tiny or ultra-structural components like cellular connections.

A Jan. 8, 2015 Children’s Hospital Los Angeles news release (also on EurekAlert), which originated the news item, describes the problems the researchers were addressing,

Tissue-engineered small intestine (TESI) grows from stem cells contained in the intestine and offers a promising treatment for short bowel syndrome (SBS), a major cause of intestinal failure, particularly in premature babies and newborns with congenital intestinal anomalies.  TESI may one day offer a therapeutic alternative to the current standard treatment, which is intestinal transplantation, and could potentially solve its largest challenges – donor shortage and the need for lifelong immunosuppression.

Grikscheit [Tracy C. Grikscheit, MD, a principal investigator in The Saban Research Institute of CHLA and its Developmental Biology and Regenerative Medicine program]  aims to help her most vulnerable young patients, including babies who are born prematurely and develop a devastating disease called necrotizing enterocolitis (NEC), where life-threatening intestinal damage requires removal of large portions of the small intestine. Without enough intestinal length, the babies are dependent on intravenous feeding, which is costly and may cause liver damage.  NEC and other contributors to intestinal failure occur in 24.5 out of 100,000 live births, and the incidence of SBS is increasing.  Nearly a third of patients die within five years.

The news release goes on to describe precursor work from 2011 before describing the latest research,

CHLA scientists had previously shown that TESI could be generated from human small intestine donor tissue implanted into immunocompromised mice. However, in those initial studies – published in July 2011 in the biomedical journal Tissue Engineering, Part A – only basic components of the intestine were identified. For clinical relevance, it remained necessary to more fully investigate intact components of function such as the ability to form a healthy barrier while still absorbing nutrition or specific mechanisms of electrolyte exchange.

The new study determined that mouse TESI is highly similar to the TESI derived from human cells, and that both contain important building blocks such as the stem and progenitor cells that will continue to regenerate the intestine as a living tissue replacement. And these cells are found within the engineered tissue in specific locations and in close proximity to other specialized cells that are known to be necessary in healthy human intestine for a fully functioning organ.

“We have shown that we can grow tissue-engineered small intestine that is more complex than other stem cell or progenitor cell models that are currently used to study intestinal regeneration and disease, and proven it to be fully functional as it develops from human cells,” said Grikscheit. “Demonstrating the functional capacity of this tissue-engineered intestine is a necessary milestone on our path toward one day helping patients with intestinal failure.”

If I read this rightly, the researchers engineered more complex intestinal tissues, than those in the 2011 study, in two separate processes where they grew mouse and human small intestinal tissue and successfully implanted both types of tissue into mice. The results showed that these more complex tissue-engineered small intestines (TESIs), human or mouse, resembled each other functionally within the mice tested.

Here’s a link to and a citation for the paper,

Human and Mouse Tissue-Engineered Small Intestine Both Demonstrate Digestive And Absorptive Function by Christa Nicole Grant, Garcia Mojica Salvador, Frederic G Sala, Jeffrey Ryan Hill, Daniel E Levin, Allison L Speer, Erik R Barthel, Hiroyuki Shimada, Nicholas C. Zachos, and Tracy C. Grikscheit. American Journal of Physiology – Gastrointestinal and Liver Physiology Published 8 January 2015Vol. no. , DOI: 10.1152/ajpgi.00111.2014

This paper is behind a paywall.

Remotely controlling bone regeneration with metallic nanoparticles

A Nov. 24, 2014 news item on ScienceDaily heralds some bone regeneration research which was published back in Sept. 2014,

Researchers in bone tissue regeneration believe they have made a significant breakthrough for sufferers of bone trauma, disease or defects such as osteoporosis.

Medical researchers from Keele University and Nottingham University have found that magnetic nanoparticles coated with targeting proteins can stimulate stem cells to regenerate bone. Researchers were also able to deliver the cells directly to the injured area, remotely controlling the nanoparticles to generate mechanical forces and maintain the regeneration process through staged releases of a protein growth stimulant.

A Nov. 17, 2014 Keele University (UK) press release, which originated the news item, describes the issues the researchers are addressing and their research approach,

The current method for repairing bone that can’t heal itself is through a graft taken from the patient. Unfortunately, this can be a painful, invasive procedure, and when the area that needs repair is too large or the patient has a skeletal disorder such as there can sometimes be a lack of healthy bone for grafting.

For this reason, spurring the growth of new bone through injected stem cells is an area of great interest to medical researchers. Much progress has been made, but a major hurdle remains – finding an appropriate means to stimulate the differentiation of the stem cells so they become the quality of bone tissue needed in a quantity large enough to treat patients effectively.

James Henstock, Ph.D. led the Biotechnology and Biological Sciences Research Council (BBSRC)-funded study, alongside Alicia El Haj, Ph.D., and colleagues at Keele University’s Institute for Science and Technology in Medicine, as well as Kevin Shakesheff, Ph.D., from the University of Nottingham’s School of Pharmacy.

James Henstock said: “Injectable therapies for regenerative medicine show great potential as a minimally invasive route for introducing therapeutic stem cells, drug delivery vehicles and biomaterials efficiently to wound sites.”

“In our investigation we coated magnetic nanoparticles with specific targeting proteins then controlled them remotely with an external magnetic field to simulate exercise. We wanted to learn how this might affect the injected stem cells and their ability to restore functional bone.”

The team of researchers conducted their test using two models: chicken foetal femurs and tissue-engineered collagen hydrogels. In both instances the results showed an increase in bone formation and density without causing any mechanical stress to the construct or surrounding tissue.

“This work demonstrates that providing the appropriate mechanical cues in conjunction with controlled release of growth factors to these injectable cell therapies can have a significant impact on improving bone growth. It also could potentially improve tissue engineering approaches for translational medicine” Dr. Henstock said.

Here’s a link to and a citation for the published paper,

Remotely Activated Mechanotransduction via Magnetic Nanoparticles Promotes Mineralization Synergistically With Bone Morphogenetic Protein 2: Applications for Injectable Cell Therapy by James R. Henstock, Michael Rotherham, Hassan Rashidi, Kevin M. Shakesheff, and Alicia J. El Haja. Stem Cells Trans Med September 2014 sctm.2014-0017  (First Published Online September 22, 2014 doi: 10.5966/sctm.2014-0017)

This paper is open access but you do need to sign up for a free registration for access to the website.

Cartilage; the ‘official tissue’ of tissue engineering

What is this fascination with cartilage? For the second time this week (see yesterday’s [April 30, 2014] posting: Replacement cartilage grown on laboratory chip)  there’s a news item about a team, this time from Columbia University School of Engineering and Applied Sciences (aka Columbia Engineering), growing cartilage. From an April 30, 2014 news item on ScienceDaily,

Researchers at Columbia Engineering announced today that they have successfully grown fully functional human cartilage in vitro from human stem cells derived from bone marrow tissue. Their study, which demonstrates new ways to better mimic the enormous complexity of tissue development, regeneration, and disease, is published in the April 28 Early Online edition of Proceedings of the National Academy of Sciences (PNAS).

“We’ve been able — for the first time — to generate fully functional human cartilage from mesenchymal stem cells by mimicking in vitro the developmental process of mesenchymal condensation,” says Gordana Vunjak-Novakovic, who led the study and is the Mikati Foundation Professor of Biomedical Engineering at Columbia Engineering and professor of medical sciences. “This could have clinical impact, as this cartilage can be used to repair a cartilage defect, or in combination with bone in a composite graft grown in lab for more complex tissue reconstruction.”

An April 30, 2014 Columbia Engineering news release by Holly Evans, which originated the news item, provides some insight into the issues associated with tissue engineering and cartilage,

For more than 20 years, researchers have unofficially called cartilage the “official tissue of tissue engineering,” Vunjak-Novakovic observes. [emphasis mine] Many groups studied cartilage as an apparently simple tissue: one single cell type, no blood vessels or nerves, a tissue built for bearing loads while protecting bone ends in the joints. While there has been great success in engineering pieces of cartilage using young animal cells, no one has, until now, been able to reproduce these results using adult human stem cells from bone marrow or fat, the most practical stem cell source. Vunjak-Novakovic’s team succeeded in growing cartilage with physiologic architecture and strength by radically changing the tissue-engineering approach.

The general approach to cartilage tissue engineering has been to place cells into a hydrogel and culture them in the presence of nutrients and growth factors and sometimes also mechanical loading. But using this technique with adult human stem cells has invariably produced mechanically weak cartilage. So Vunjak-Novakovic and her team, who have had a longstanding interest in skeletal tissue engineering, wondered if a method resembling the normal development of the skeleton could lead to a higher quality of cartilage.

(I love the combination of “unofficially” with “official.”) Getting back to the cartilage research, the news release goes on to describe a new technique for engineering cartilage,

Sarindr Bhumiratana, postdoctoral fellow in Vunjak-Novakovic’s Laboratory for Stem Cells and Tissue Engineering, came up with a new approach: inducing the mesenchymal stem cells to undergo a condensation stage as they do in the body before starting to make cartilage. He discovered that this simple but major departure from how things were usually being done resulted in a quality of human cartilage not seen before.

Gerard Ateshian, Andrew Walz Professor of Mechanical Engineering, professor of biomedical engineering, and chair of the Department of Mechanical Engineering, and his PhD student, Sevan Oungoulian, helped perform measurements showing that the lubricative property and compressive strength—the two important functional properties—of the tissue-engineered cartilage approached those of native cartilage. The researchers then used their method to regenerate large pieces of anatomically shaped and mechanically strong cartilage over the bone, and to repair defects in cartilage.

“Our whole approach to tissue engineering is biomimetic in nature, which means that our engineering designs are defined by biological principles,” Vunjak-Novakovic notes. “This approach has been effective in improving the quality of many engineered tissues—from bone to heart. Still, we were really surprised to see that our cartilage, grown by mimicking some aspects of biological development, was as strong as ‘normal’ human cartilage.”

The team plans next to test whether the engineered cartilage tissue maintains its structure and long-term function when implanted into a defect.

Here’s a link to and a citation for the research paper,

Large, stratified, and mechanically functional human cartilage grown in vitro by mesenchymal condensation by Sarindr Bhumiratana, Ryan E. Eton, Sevan R. Oungoulian, Leo Q. Wan, Gerard A. Ateshian, and Gordana Vunjak-Novakovic. Proceedings of the National Academy of Sciences, 2014; DOI: 10.1073/pnas.1324050111

This paper is behind a paywall.

I have an observation about both this and the other cartilage story (Replacement cartilage grown on laboratory chip) featured here. It looks to me as if these two areas of research could be complementary. The ‘laboratory chip’ story is about a new way to use 3D printing to produce cartilage more quickly where this Columbia Engineering story is about better mimicking processes in the body to engineer stronger, more resilient cartilage. Taken separately or together cartilage tissue engineering has had an exciting week.

Replacement cartilage grown on laboratory chip

Most of us don’t think too much about cartilage (soft, flexible connective tissue found in the body) unless it’s damaged in which case it’s importance becomes immediately apparent. There is no substitute for cartilage although scientists are working on that problem and it seems that one team may have made a significant breakthrough according to an April 27, 2014 news item on ScienceDaily,

In a significant step toward reducing the heavy toll of osteoarthritis around the world, scientists have created the first example of living human cartilage grown on a laboratory chip. The researchers ultimately aim to use their innovative 3-D printing approach to create replacement cartilage for patients with osteoarthritis or soldiers with battlefield injuries.

“Osteoarthritis has a severe impact on quality of life, and there is an urgent need to understand the origin of the disease and develop effective treatments” said Rocky Tuan, Ph.D., director of the Center for Cellular and Molecular Engineering at the University of Pittsburgh School of Medicine, member of the American Association of Anatomists and the study’s senior investigator. “We hope that the methods we’re developing will really make a difference, both in the study of the disease and, ultimately, in treatments for people with cartilage degeneration or joint injuries.”

Osteoarthritis is marked by a gradual disintegration of cartilage, a flexible tissue that provides padding where bones come together in a joint. Causing severe pain and loss of mobility in joints such as knees and fingers, osteoarthritis is one of the leading causes of physical disability in the United States. It is estimated that up to 1 in 2 Americans will develop some form of the disease in their lifetime.

Although some treatments can help relieve arthritis symptoms, there is no cure. Many patients with severe arthritis ultimately require a joint replacement.

An April 27,2014 Experimental Biology (EB) 2014 news release provides more insight,

Tuan said artificial cartilage built using a patient’s own stem cells could offer enormous therapeutic potential. “Ideally we would like to be able to regenerate this tissue so people can avoid having to get a joint replacement, which is a pretty drastic procedure and is unfortunately something that some patients have to go through multiple times,” said Tuan.

In addition to offering relief for people with osteoarthritis, Tuan said replacement cartilage could also be a game-changer for people with debilitating joint injuries, such as soldiers with battlefield injuries. “We really want these technologies to help wounded warriors return to service or pursue a meaningful post-combat life,” said Tuan, who co-directs the Armed Forces Institute of Regenerative Medicine, a national consortium focused on developing regenerative therapies for injured soldiers. “We are on a mission.”

Creating artificial cartilage requires three main elements: stem cells, biological factors to make the cells grow into cartilage, and a scaffold to give the tissue its shape. Tuan’s 3-D printing approach achieves all three by extruding thin layers of stem cells embedded in a solution that retains its shape and provides growth factors. “We essentially speed up the development process by giving the cells everything they need, while creating a scaffold to give the tissue the exact shape and structure that we want,” said Tuan.

The ultimate vision is to give doctors a tool they can thread through a catheter to print new cartilage right where it’s needed in the patient’s body. Although other researchers have experimented with 3-D printing approaches for cartilage, Tuan’s method represents a significant step forward because it uses visible light, while others have required UV light, which can be harmful to living cells.

In another significant step, Tuan has successfully used the 3-D printing method to produce the first “tissue-on-a-chip” replica of the bone-cartilage interface. Housing 96 blocks of living human tissue 4 millimeters across by 8 millimeters deep, the chip could serve as a test-bed for researchers to learn about how osteoarthritis develops and develop new drugs. “With more testing, I think we’ll be able to use our platform to simulate osteoarthritis, which would be extremely useful since scientists really know very little about how the disease develops,” said Tuan.

As a next step, the team is working to combine their 3-D printing method with a nanofiber spinning technique they developed previously. They hope combining the two methods will provide a more robust scaffold and allow them to create artificial cartilage that even more closely resembles natural cartilage.

Rocky Tuan presented the research during the Experimental Biology 2014 meeting on Sunday, April 27 [2014].

I haven’t been able to find any papers published on this work but you can find Rocky Tuan’s faculty page (along with a list of publications) here and you may have more luck with the EB 2014 conference website than I did.

Mesenchymal condensation (a process embryos use to begin forming a variety of organs, including teeth, cartilage, bone, muscle, tendon, and kidney) for complex 3D tissue engineering

It seems that there are three strategies for creating complex 3D tissues and until now scientists have used only two of the three. From a March 5, 2014 news item on ScienceDaily,

A bit of pressure from a new shrinking, sponge-like gel is all it takes to turn transplanted unspecialized cells into cells that lay down minerals and begin to form teeth.

The bioinspired gel material could one day help repair or replace damaged organs, such as teeth and bone, and possibly other organs as well, scientists from the Wyss Institute for Biologically Inspired Engineering at Harvard University, Harvard School of Engineering and Applied Sciences (SEAS), and Boston Children’s Hospital report recently in Advanced Materials.

“Tissue engineers have long raised the idea of using synthetic materials to mimic the inductive power of the embryo,” said Don Ingber, M.D., Ph.D., Founding Director of the Wyss Institute, …, Professor of Bioengineering at SEAS, and senior author of the study. “We’re excited about this work because it shows that it really is possible.”

The March 5, 2014 Wyss Institute news release, which originated the news item, delves into the nature of the research,

Embryonic tissues have the power to drive cells and tissues to specialize and form organs. To do that, they employ biomolecules called growth factors to stimulate growth; gene-activating chemicals that cause the cells to specialize, and mechanical forces that modulate cell responses to these other factors.

But so far tissue engineers who want to build organs in the laboratory have employed only two of the three strategies — growth factors and gene-activating chemicals. Perhaps as a result, they have not yet succeeded in producing complex three-dimensional tissues.

A few years ago, Ingber and Tadanori Mammoto, M.D., Ph.D., Instructor in Surgery at Boston Children’s Hospital and Harvard Medical School, investigated a process called mesenchymal condensation that embryos use to begin forming a variety of organs, including teeth, cartilage, bone, muscle, tendon, and kidney.

In mesenchymal condensation, two adjacent tissue layers — loosely packed connective-tissue cells called mesenchyme and sheet-like tissue called an epithelium that covers it — exchange biochemical signals. This exchange causes the mesenchymal cells to squeeze themselves tightly into a small knot directly below where the new organ will form.

Here’s a video from the Wyss Institute illustrating the squeezing process,

When the temperature rises to just below body temperature, this biocompatible gel shrinks dramatically within minutes, bringing tooth-precursor cells (green) closer together. Credit: Basma Hashmi

Getting back to the research (from the news release),

By examining tissues isolated from the jaws of embryonic mice, Mammoto and Ingber showed that when the compressed mesenchymal cells turn on genes that stimulate them to generate whole teeth composed of mineralized tissues, including dentin and enamel.

Inspired by this embryonic induction mechanism, Ingber and Basma Hashmi, a Ph.D. candidate at SEAS who is the lead author of the current paper, set out to develop a way to engineer artificial teeth by creating a tissue-friendly material that accomplishes the same goal. Specifically, they wanted a porous sponge-like gel that could be impregnated with mesenchymal cells, then, when implanted into the body, induced to shrink in 3D to physically compact the cells inside it.

To develop such a material, Ingber and Hashmi teamed up with researchers led by Joanna Aizenberg, Ph.D., a Wyss Institute Core Faculty member who leads the Institute’s Adaptive Materials Technologies platform. Aizenberg is the Amy Smith Berylson Professor of Materials Science at SEAS and Professor of Chemistry and Chemical Biology at Harvard University.

They chemically modified a special gel-forming polymer called PNIPAAm that scientists have used to deliver drugs to the body’s tissues. PNIPAAm gels have an unusual property: they contract abruptly when they warm.

But they do this at a lukewarm temperature, whereas the researchers wanted them to shrink specifically at 37°C — body temperature — so that they’d squeeze their contents as soon as they were injected into the body. Hashmi worked with Lauren Zarzar, Ph.D., a former SEAS graduate student who’s now a postdoctoral associate at Massachusetts Institute of Technology, for more than a year, modifying PNIPAAm and testing the resulting materials. Ultimately, they developed a polymer that forms a tissue-friendly gel with two key properties: cells stick to it, and it compresses abruptly when warmed to body temperature.

As an initial test, Hashmi implanted mesenchymal cells in the gel and warmed it in the lab. Sure enough, when the temperature reached 37°C, the gel shrank within 15 minutes, causing the cells inside the gel to round up, shrink, and pack tightly together.

“The reason that’s cool is that the cells are alive,” Hashmi said. “Usually when this happens, cells are dead or dying.”

Not only were they alive — they activated three genes that drive tooth formation.

To see if the shrinking gel also worked its magic in the body, Hashmi worked with Mammoto to load mesenchymal cells into the gel, then implant the gel beneath the mouse kidney capsule — a tissue that is well supplied with blood and often used for transplantation experiments.

The implanted cells not only expressed tooth-development genes — they laid down calcium and minerals, just as mesenchymal cells do in the body as they begin to form teeth.

“They were in full-throttle tooth-development mode,” Hashmi said.

The researchers have future plans (from the news release),

In the embryo, mesenchymal cells can’t build teeth alone — they need to be combined with cells that form the epithelium. In the future, the scientists plan to test whether the shrinking gel can stimulate both tissues to generate an entire functional tooth.

Here’s a link to and a citation for the paper about the successful attempt to stimulate mesenchymal cells into the beginnings of tooth formation,

Developmentally-Inspired Shrink-Wrap Polymers for Mechanical Induction of Tissue Differentiation by Basma Hashmi, Lauren D. Zarzar, Tadanori Mammoto, Akiko Mammoto, Amanda Jiang, Joanna Aizenberg, and Donald E. Ingber. Advanced Materials Article first published online: 18 FEB 2014 DOI: 10.1002/adma.201304995

© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

This paper is behind a paywall.

Assembly-line 3-D tissue engineering

It looks as if the researchers at Singapore’s Institute of Bioengineering and Nanotechnology (IBN), have developed a template for producing complex tissues such as those in liver and in fat, from an Aug. 20, 2013 news item on ScienceDaily,

Researchers at the Institute of Bioengineering and Nanotechnology (IBN) have developed a simple method of organizing cells and their microenvironments in hydrogel fibers. Their unique technology provides a feasible template for assembling complex structures, such as liver and fat tissues, as described in their recent publication in Nature Communications.

According to IBN Executive Director Professor Jackie Y. Ying, “Our tissue engineering approach gives researchers great control and flexibility over the arrangement of individual cell types, making it possible to engineer prevascularized tissue constructs easily. This innovation brings us a step closer toward developing viable tissue or organ replacements.”

The Aug. 19, 2013 A*STAR’s (Singapore’s Agency for Science and Technology Research) IBN  press release, which originated the news item, offers a detailed explanation of how this discovery could make tissue and organ replacements much easier,

IBN Team Leader and Principal Research Scientist, Dr Andrew Wan, elaborated, “Critical to the success of an implant is its ability to rapidly integrate with the patient’s circulatory system. This is essential for the survival of cells within the implant, as it would ensure timely access to oxygen and essential nutrients, as well as the removal of metabolic waste products. Integration would also facilitate signaling between the cells and blood vessels, which is important for tissue development.”

Tissues designed with pre-formed vascular networks are known to promote rapid vascular integration with the host. Generally, prevascularization has been achieved by seeding or encapsulating endothelial cells, which line the interior surfaces of blood vessels, with other cell types. In many of these approaches, the eventual distribution of vessels within a thick structure is reliant on in vitro cellular infiltration and self-organization of the cell mixture. These are slow processes, often leading to a non-uniform network of vessels within the tissue. As vascular self-assembly requires a large concentration of endothelial cells, this method also severely restricts the number of other cells that may be co-cultured.

Alternatively, scientists have attempted to direct the distribution of newly formed vessels via three-dimensional (3D) co-patterning of endothelial cells with other cell types in a hydrogel. This approach allows large concentrations of endothelial cells to be positioned in specific regions within the tissue, leaving the rest of the construct available for other cell types. The hydrogel also acts as a reservoir of nutrients for the encapsulated cells. However, co-patterning multiple cell types within a hydrogel is not easy. Conventional techniques, such as micromolding and organ printing, are limited by slow cell assembly, large volumes of cell suspension, complicated multi-step processes and expensive instruments. These factors also make it difficult to scale up the production of implantable 3D cell-patterned constructs. To date, these approaches have been unsuccessful in achieving vascularization and mass transport through thick engineered tissues.

To overcome these limitations, IBN researchers have used interfacial polyelectrolyte complexation (IPC) fiber assembly, a unique cell patterning technology patented by IBN, to produce cell-laden hydrogel fibers under aqueous conditions at room temperature. Unlike other methods, IBN’s novel technique allows researchers to incorporate different cell types separately into different fibers, and these cell-laden fibers may then be assembled into more complex constructs with hierarchical tissue structures. In addition, IBN researchers are able to tailor the microenvironment for each cell type for optimal functionality by incorporating the appropriate factors, e.g. proteins, into the fibers. Using IPC fiber assembly, the researchers have engineered an endothelial vessel network, as well as cell-patterned fat and liver tissue constructs, which have successfully integrated with the host circulatory system in a mouse model and produced vascularized tissues.

Here’s a citation for and link to the published paper,

Patterned prevascularised tissue constructs by assembly of polyelectrolyte hydrogel fibres by Meng Fatt Leong,    Jerry K. C. Toh, Chan Du, Karthikeyan Narayanan, Hong Fang Lu, Tze Chiun Lim, Andrew C. A. Wan, & Jackie Y. Ying. Nature Communications 4, Article number: 2353 doi:10.1038/ncomms3353 Published 19 August 2013

This article is behind a paywall although you can preview it with ReadingCube access.

A ‘glass jaw’ might turn out to be a good thing

I don’t know if the phrase ‘glass jaw’ is used much any more but it was a term for someone who couldn’t ‘take’ a punch to the jaw (i.e., the person was instantly rendered unconscious or helplessly groggy). If scientists at Missouri University of Science and Technology (Missouri S&T)  have their way, the phrase ‘glass jaw’ will have a new meaning as per the July 26, 2012 news item on ScienceDaily,

Researchers at Missouri University of Science and Technology have developed a type of glass implant that could one day be used to repair injured bones in the arms, legs and other areas of the body that are most subject to the stresses of weight.

This marks the first time researchers have shown a glass implant strong enough to bear weight can also integrate with bone and promote bone growth, says lead researcher Dr. Mohamed N. Rahaman, professor of materials science and engineering at Missouri S&T.

The July 26, 2013 Missouri S&T news release by Andrew Careaga, which originated the news item, describes the work leading to this latest research,

In previous work, the Missouri S&T researchers developed a glass implant strong enough to handle the weight and pressure of repetitive movement, such as walking or lifting. In their most recent study, published in the journal Acta Biomaterialia, the research team reported that the glass implant, in the form of a porous scaffolding, also integrates with bone and promotes bone growth.

This combination of strength and bone growth opens new possibilities for bone repair, says Rahaman, who also directs Missouri S&T’s Center for Biomedical Science and Engineering, where the research was conducted.

The news release then goes on to describe one of the problems with using synthetic materials for bone repair and explains how this latest research addresses the issue,

Conventional approaches to structural bone repair involve either the use of a porous metal, which does not reliably heal bone, or a bone allograft from a cadaver. Both approaches are costly and carry risks, Rahaman says. He thinks the type of glass implant developed in his center could provide a more feasible approach for repairing injured bones. The glass is bioactive, which means that it reacts when implanted in living tissue and convert to a bone-like material.

In their latest research, Rahaman and his colleagues implanted bioactive glass scaffolds into sections of the calvarial bones (skullcaps) of laboratory rats, then examined how well the glass integrated with the surrounding bone and how quickly new bone grew into the scaffold. The scaffolds are manufactured in Rahaman’s lab through a process known as robocasting – a computer-controlled technique to manufacture materials from ceramic slurries, layer by layer – to ensure uniform structure for the porous material.

In previous studies by the Missouri S&T researchers, porous scaffolds of the silicate glass, known as 13-93, were found to have the same strength properties as cortical bone. Cortical bones are those outer bones of the body that bear the most weight and undergo the most repetitive stress. They include the long bones of the arms and legs.

But what Rahaman and his colleagues didn’t know was how well the silicate 13-93 bioactive glass scaffolds would integrate with bone or how quickly bone would grow into the scaffolding.

“You can have the strongest material in the world, but it also must encourage bone growth in a reasonable amount of time,” says Rahaman. He considers three to six months to be a reasonable time frame for completely regenerating an injured bone into one strong enough to bear weight.

In their studies, the S&T researchers found that the bioactive glass scaffolds bonded quickly to bone and promoted a significant amount of new bone growth within six weeks.

While the skullcap is not a load-bearing bone, it is primarily a cortical bone. The purpose of this research was to demonstrate how well this type of glass scaffolding – already shown to be strong – would interact with cortical bone.

Rahaman and his fellow researchers in the Center for Biomedical Science and Engineering are now experimenting with true load-bearing bones. They are now testing the silicate 13-93 implants in the femurs (leg bones) of laboratory rats.

In the future, Rahaman plans to experiment with modified glass scaffolds to see how well they enhance certain attributes within bone. For instance, doping the glass with copper should promote the growth of blood vessels or capillaries within the new bone, while doping the glass with silver will give it antibacterial properties.

It’s exciting work but they are years from human clinical trials. Still, for those who want to explore further, here’s a link to and a citation for the published paper,

Enhanced bone regeneration in rat calvarial defects implanted with surface-modified and BMP-loaded bioactive glass (13-93) scaffolds by Xin Liua, Mohamed N. Rahaman, Yongxing Liu, B. Sonny Bal, and Lynda F. Bonewald. Acta Biomaterialia, July 2013 issue (Volume 9, Issue 7)  http://dx.doi.org/10.1016/j.actbio.2013.03.039

This paper is behind a paywall.