Tag Archives: mesenchymal stem cells

Questioning or rewriting a ‘central’ dogma of biology?

Answering the question in the head, this December 12, 2023 news item on phys.org calls into question the principle behind how medicines based on antibodies work,

Today, medicines based on antibodies—proteins that fight infection and disease—are prescribed for everything from cancer to COVID-19 to high cholesterol. The antibody drugs are supplied by genetically-engineered cells that function as tiny protein-producing factories in the laboratory.

Meanwhile, researchers have been targeting cancer, injuries to internal organs and a host of other ailments with new strategies in which similarly engineered cells are implanted directly into patients.

These biotechnology applications rely on the principle that altering a cell’s DNA to produce more of the genetic instructions for making a given protein will cause the cell to release more of that protein.

A new UCLA [University of California at Los Angeles] study suggests that—at least in one type of stem cell—the principle doesn’t necessarily hold true.

A December 11, 2023 UCLA news release, which originated the news item, delves further into the topic but first the key points are noted, Note: Links have been removed,

Key takeaways

  • Mesenchymal stem cells, found in bone marrow, secrete therapeutic proteins that could potentially help regenerate damaged tissue.
  • A UCLA study examining these cells challenges the conventional understanding of which genetic instructions prompt the release of these therapeutic proteins.
  • The findings could help advance both regenerative medicine research and the laboratory production of biologic treatments already in use.

The researchers examined mesenchymal stem cells, which reside in bone marrow and can self-renew or develop into bone, fat or muscle cells. Mesenchymal cells secrete a protein growth factor called VEGF-A, which plays a role in regenerating blood vessels and which scientists believe may have the potential to repair damage from heart attacks, kidney injuries, arterial disease in limbs and other conditions.

When the researchers compared the amount of VEGF-A that each mesenchymal cell released with the expression of genes in the same cell that code for VEGF-A, the results were surprising: Gene expression correlated only weakly with the actual secretion of the growth factor.  

The scientists identified other genes better correlating with growth factor secretion, including one that codes for a protein found on the surface of some stem cells. Isolating stem cells with that protein on their surface, the team cultivated a population that secreted VEGF-A prolifically and kept doing so days later.

The findings, published today [December 11, 2023] in Nature Nanotechnology, suggest that a fundamental assumption in biology and biotechnology may be up for reconsideration, said co-corresponding author Dino Di Carlo, the Armond and Elena Hairapetian Professor of Engineering and Medicine at the UCLA Samueli School of Engineering.

“The central dogma has been, you have instructions in the DNA, they’re transcribed to RNA, and then the RNA is translated into protein,” said Di Carlo, who is also a member of UCLA’s California NanoSystems Institute and Eli and Edythe Broad Center of Regenerative Medicine and Stem Cell Research. “Based on this, many scientists assumed that if you had more RNA, you’d have more protein, and then more protein released from the cell. We questioned that assumption.

“It seems we can’t assume that if a gene is expressed at higher levels, there will be higher secretion of the corresponding protein. We found a clear example where that doesn’t happen, and it opens up a lot of new questions.”

The results could help make the manufacturing of antibody-based treatments more efficient and define new cellular treatments that would be more effective. Knowing the right genetic switches to flip could enable the engineering or selection of extraordinarily productive cells for making or delivering therapies.

The UCLA study was conducted using standard lab equipment augmented with a technology invented by Di Carlo and his colleagues: nanovials, microscopic bowl-shaped hydrogel containers, each of which captures a single cell and its secretions. Leveraging a new nanovial-enabled analytic method, the scientists were able to connect the amount of VEGF-A released by each one of 10,000 mesenchymal stem cells to an atlas mapping tens of thousands of genes expressed by that same cell.

“The ability to link protein secretion to gene expression on the single-cell level holds great promise for the fields of life science research and therapeutic development,” said Kathrin Plath, a UCLA professor of biological chemistry, a member of the Broad Stem Cell Research Center and a co-corresponding author of the study. “Without it, we couldn’t have arrived at the unexpected results we found in this study. Now we have an exciting opportunity to learn new things about the mechanisms underpinning the basic processes of life and use what we learn to advance human health.”

While activation of the genetic instructions for VEGF-A displayed little correlation with release of the protein, the researchers identified a cluster of 153 genes with strong links to VEGF-A secretion. Many of them are known for their function in blood vessel development and wound healing; for others, their function is currently unknown.

One of the top matches encodes a cell-surface protein, IL13RA2, whose purpose is poorly understood. Its exterior location made it simpler for the scientists to use it as a marker and separate those cells from the others. Cells with IL13RA2 showed 30% more VEGF-A secretion than cells that lacked the marker.

In a similar experiment, the researchers kept the separated cells in culture for six days. At the end of that time, cells with the marker secreted 60% more VEGF-A compared to cells without it.

Although therapies based on mesenchymal stem cells have shown promise in laboratory studies, clinical trials with human participants have shown many of these new options to be safe but not effective. The ability to sort for high VEGF-A secreters using IL13RA2 may help turn that tide.

“Identifying a subpopulation that produces more, and markers associated with that population, means you can separate them out very easily,” Di Carlo said. “A very pure population of cells that’s going to produce high levels of your therapeutic protein should make a better therapy.”

Nanovials are available commercially from Partillion Bioscience, a company co-founded by Di Carlo that started up at the CNSI’s on-campus incubator, Magnify.

The first author of the study is Shreya Udani, who earned a doctorate from UCLA in 2023. Other co-authors, all affiliated with UCLA, are staff scientist Justin Langerman; Doyeon Koo, who earned a doctorate in 2023; graduate students Sevana Baghdasarian and Citradewi Soemardy; undergraduate Brian Cheng; Simran Kang, who earned a bachelor’s degree in 2023; and Joseph de Rutte, who earned a doctorate in 2020 and is a co-founder and CEO of Partillion.

The study was supported by the National Institutes of Health and a Stem Cell Nanomedicine Planning Award funded jointly by the CNSI and the Broad Stem Cell Research Center.

Researcher Dino Di Carlo describes his work,

Nanovials, a technology created by UCLA’s Dino Di Carlo and his colleagues, allowed researchers to capture single mesenchymal cells and their secretions. Withouth these vials, which are smaller than the width of a human hair, “we couldn’t have arrived at the unexpected results we found in this study,” said UCLA’s Kathrin Plath.

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

Associating growth factor secretions and transcriptomes of single cells in nanovials using SEC-seq by Shreya Udani, Justin Langerman, Doyeon Koo, Sevana Baghdasarian, Brian Cheng, Simran Kang, Citradewi Soemardy, Joseph de Rutte, Kathrin Plath & Dino Di Carlo. Nature Nanotechnology (2023) DOI: https://doi.org/10.1038/s41565-023-01560-7 Published: 11 December 2023

This paper is behind a paywall.

As for the two companies mentioned in the news release, you find Partillion Bioscience here and Magnify at CNSI here.

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.