Tag Archives: Jie Zhu

Using CRISPR to reverse retinosa pigmentosa (eye disease)

Years ago I worked as a publicist for the BC (British Columbia) Motorcycle Federation’s Ride for Sight; they were raising funds for research into retinitis pigmentosa (RP). I hadn’t thought about that in years but it all came back when I saw this April 21, 2017 news item on ScienceDaily,

Using the gene-editing tool CRISPR/Cas9, researchers at University of California San Diego [UCSD] School of Medicine and Shiley Eye Institute at UC San Diego Health, with colleagues in China, have reprogrammed mutated rod photoreceptors to become functioning cone photoreceptors, reversing cellular degeneration and restoring visual function in two mouse models of retinitis pigmentosa.

Caption: This is a confocal micrograph of mouse retina depicting optic fiber layer. Credit: Image courtesy of National Center for Microscopy and Imaging Research, UC San Diego.

An April 21, 2017 UCSD news release by Scott LaFee (also on EurekAlert), which originated the news item, delves further into retinitis pigmentosa and this CRISPR research,

Retinitis pigmentosa (RP) is a group of inherited vision disorders caused by numerous mutations in more than 60 genes. The mutations affect the eyes’ photoreceptors, specialized cells in the retina that sense and convert light images into electrical signals sent to the brain. There are two types: rod cells that function for night vision and peripheral vision, and cone cells that provide central vision (visual acuity) and discern color. The human retina typically contains 120 million rod cells and 6 million cone cells.

In RP, which affects approximately 100,000 Americans and 1 in 4,000 persons worldwide, rod-specific genetic mutations cause rod photoreceptor cells to dysfunction and degenerate over time. Initial symptoms are loss of peripheral and night vision, followed by diminished visual acuity and color perception as cone cells also begin to fail and die. There is no treatment for RP. The eventual result may be legal blindness.

In their published research, a team led by senior author Kang Zhang, MD, PhD, chief of ophthalmic genetics, founding director of the Institute for Genomic Medicine and co-director of biomaterials and tissue engineering at the Institute of Engineering in Medicine, both at UC San Diego School of Medicine, used CRISPR/Cas9 to deactivate a master switch gene called Nrl and a downstream transcription factor called Nr2e3.

CRISPR, which stands for Clustered Regularly Interspaced Short Palindromic Repeats, allows researchers to target specific stretches of genetic code and edit DNA at precise locations, modifying select gene functions. Deactivating either Nrl or Nr2e3 reprogrammed rod cells to become cone cells.

“Cone cells are less vulnerable to the genetic mutations that cause RP,” said Zhang. “Our strategy was to use gene therapy to make the underlying mutations irrelevant, resulting in the preservation of tissue and vision.”

The scientists tested their approach in two different mouse models of RP. In both cases, they found an abundance of reprogrammed cone cells and preserved cellular architecture in the retinas. Electroretinography testing of rod and cone receptors in live mice show improved function.

Zhang said a recent independent study led by Zhijian Wu, PhD, at National Eye Institute, part of the National Institutes of Health, also reached similar conclusions.

The researchers used adeno-associated virus (AAV) to perform the gene therapy, which they said should help advance their work to human clinical trials quicker. “AAV is a common cold virus and has been used in many successful gene therapy treatments with a relatively good safely profile,” said Zhang. “Human clinical trials could be planned soon after completion of preclinical study. There is no treatment for RP so the need is great and pressing. In addition, our approach of reprogramming mutation-sensitive cells to mutation-resistant cells may have broader application to other human diseases, including cancer.”

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

Gene and mutation independent therapy via CRISPR-Cas9 mediated cellular reprogramming in rod photoreceptors by Jie Zhu, Chang Ming, Xin Fu, Yaou Duan, Duc Anh Hoang, Jeffrey Rutgard, Runze Zhang, Wenqiu Wang, Rui Hou, Daniel Zhang, Edward Zhang, Charlotte Zhang, Xiaoke Hao, Wenjun Xiong, and Kang Zhang. Cell Research advance online publication 21 April 2017; doi: 10.1038/cr.2017.57

This paper (it’s in the form of a letter to the editor) is open access.

3D printed biomimetic blood vessel networks

An artificial blood vessel network that could lead the way to regenerating biologically-based blood vessel networks has been printed in 3D at the University of California at San Diego (UCSD) according to a March 2, 2017 news item on ScienceDaily,

Nanoengineers at the University of California San Diego have 3D printed a lifelike, functional blood vessel network that could pave the way toward artificial organs and regenerative therapies.

The new research, led by nanoengineering professor Shaochen Chen, addresses one of the biggest challenges in tissue engineering: creating lifelike tissues and organs with functioning vasculature — networks of blood vessels that can transport blood, nutrients, waste and other biological materials — and do so safely when implanted inside the body.

A March 2, 2017 UCSD news release (also on EurekAlert), which originated the news item, explains why this is an important development,

Researchers from other labs have used different 3D printing technologies to create artificial blood vessels. But existing technologies are slow, costly and mainly produce simple structures, such as a single blood vessel — a tube, basically. These blood vessels also are not capable of integrating with the body’s own vascular system.

“Almost all tissues and organs need blood vessels to survive and work properly. This is a big bottleneck in making organ transplants, which are in high demand but in short supply,” said Chen, who leads the Nanobiomaterials, Bioprinting, and Tissue Engineering Lab at UC San Diego. “3D bioprinting organs can help bridge this gap, and our lab has taken a big step toward that goal.”

Chen’s lab has 3D printed a vasculature network that can safely integrate with the body’s own network to circulate blood. These blood vessels branch out into many series of smaller vessels, similar to the blood vessel structures found in the body. The work was published in Biomaterials.

Chen’s team developed an innovative bioprinting technology, using their own homemade 3D printers, to rapidly produce intricate 3D microstructures that mimic the sophisticated designs and functions of biological tissues. Chen’s lab has used this technology in the past to create liver tissue and microscopic fish that can swim in the body to detect and remove toxins.

Researchers first create a 3D model of the biological structure on a computer. The computer then transfers 2D snapshots of the model to millions of microscopic-sized mirrors, which are each digitally controlled to project patterns of UV light in the form of these snapshots. The UV patterns are shined onto a solution containing live cells and light-sensitive polymers that solidify upon exposure to UV light. The structure is rapidly printed one layer at a time, in a continuous fashion, creating a 3D solid polymer scaffold encapsulating live cells that will grow and become biological tissue.

“We can directly print detailed microvasculature structures in extremely high resolution. Other 3D printing technologies produce the equivalent of ‘pixelated’ structures in comparison and usually require sacrificial materials and additional steps to create the vessels,” said Wei Zhu, a postdoctoral scholar in Chen’s lab and a lead researcher on the project.

And this entire process takes just a few seconds — a vast improvement over competing bioprinting methods, which normally take hours just to print simple structures. The process also uses materials that are inexpensive and biocompatible.

Chen’s team used medical imaging to create a digital pattern of a blood vessel network found in the body. Using their technology, they printed a structure containing endothelial cells, which are cells that form the inner lining of blood vessels.

The entire structure fits onto a small area measuring 4 millimeters × 5 millimeters, 600 micrometers thick (as thick as a stack containing 12 strands of human hair).

Researchers cultured several structures in vitro for one day, then grafted the resulting tissues into skin wounds of mice. After two weeks, the researchers examined the implants and found that they had successfully grown into and merged with the host blood vessel network, allowing blood to circulate normally.

Chen noted that the implanted blood vessels are not yet capable of other functions, such as transporting nutrients and waste. “We still have a lot of work to do to improve these materials. This is a promising step toward the future of tissue regeneration and repair,” he said.

Moving forward, Chen and his team are working on building patient-specific tissues using human induced pluripotent stem cells, which would prevent transplants from being attacked by a patient’s immune system. And since these cells are derived from a patient’s skin cells, researchers won’t need to extract any cells from inside the body to build new tissue. The team’s ultimate goal is to move their work to clinical trials. “It will take at least several years before we reach that goal,” Chen said.

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

Direct 3D bioprinting of prevascularized tissue constructs with complex microarchitecture by Wei Zhu, Xin Qu, Jie Zhu, Xuanyi Ma, Sherrina Patel, Justin Liu, Pengrui Wang, Cheuk Sun Edwin Lai, Maling Gou, Yang Xu, Kang Zhang, Shaochen Chen. Biomaterials 124 (April 2017) 106-15 http://dx.doi.org/10.1016/j.biomaterials.2017.01.042

This paper is behind a paywall.

There is also an open access copy here on the university website but I cannot confirm that it is identical to the version in the journal.