Researchers have generated functional hepatocytes from human stem cells, transplanted them into mice with acute liver injury, and shown the ability of these stem-cell derived human liver cells to function normally and increase survival of the treated animals. This promising advance in the development of cell-based therapies to treat liver failure resulting from injury or disease relied on the development of scalable, reproducible methods to produce stem cell-derived hepatocytes in bioreactors, as described in an article in Stem Cells and Development.
Massoud Vosough and coauthors demonstrate a large-scale, integrated manufacturing strategy for generating functional hepatocytes in a single suspension culture grown in a scalable stirred bioreactor. In the article “Generation of Functional Hepatocyte-Like Cells from Human Pluripotent Stem Cells in a Scalable Suspension Culture” the authors describe the method used for scale-up, differentiation of the pluripotent stem cells into liver cells, and characterization and purification of the hepatocytes based on their physiological properties and the expression of liver cell biomarkers.
David C. Hay, MRC Centre for Regenerative Medicine, University of Edinburgh, U.K., comments on the importance of Vosough et al.’s contribution to the scientific literature in his editorial in Stem Cells and Development entitled “Rapid and Scalable Human Stem Cell Differentiation: Now in 3D.” The researchers “developed a system for mass manufacture of stem cell derived hepatocytes in numbers that would be useful for clinical application,” creating possibilities for future “immune matched cell based therapies,” says Hay. Such approaches could be used to correct mutated genes in stem cell populations prior to differentiation and transplantation, he adds.
“The elephant in the room for stem cell therapy rarely even acknowledged let alone addressed in the literature is that of scalable production of cells for translational application,” says Editor-in-Chief Graham C. Parker, PhD, research professor, Carman and Ann Adams Department of Pediatrics, Wayne State University School of Medicine. “Baharvand’s groups’ landmark publication not only demonstrates but exquisitely describes the methodology required to scale up stem cell populations for clinical application with a rigor to satisfy necessary manufacturing standards.”
Researchers from the UCLA Department of Obstetrics and Gynecology have isolated a new population of primitive, stress-resistant human pluripotent stem cells easily derived from fat tissue that are able to differentiate into virtually every cell type in the human body without genetic modification.
The cells, called Multi-lineage Stress-Enduring (Muse-AT) stem cells from fat, or adipose, tissue, were discovered by “scientific accident” when a piece of equipment failed in the lab, killing all the stem cells in the experiment except for the Muse-AT cells. The research team further discovered that not only are Muse-AT cells able to survive severe stress, they may even be activated by it, said study senior author Gregorio Chazenbalk, an associate researcher with UCLA Obstetrics and Gynecology.
These pluripotent cells, isolated from fat tissue removed during liposuction, expressed many embryonic stem cell markers and were able to differentiate into muscle, bone, fat, cardiac, neuronal and liver cells. An examination of their genetic characteristics confirmed their specialized functions, as well as their capacity to regenerate tissue when transplanted back into the body following their “awakening.”
“This population of cells lies dormant in the fat tissue until it is subjected to very harsh conditions. These cells can survive in conditions in which usually only cancer cells can live,” Chazenbalk said. “Upon further investigation and clinical trials, these cells could prove a revolutionary treatment option for numerous diseases, including heart disease, stroke and for tissue damage and neural regeneration.”
The results of the two-year study are published June 5, 2013 in the peer-reviewed journal PLOS ONE.
Purifying and isolating Muse-AT cells does not require the use of a cell sorter or other specialized, high-tech devices. They are able to grow either in suspension, forming cell spheres, or as adherent cells, forming cell aggregates very similar to human embryonic stem cell-derived embryoid bodies.
“We have been able to isolate these cells using a simple and efficient method that takes about six hours from the time the fat tissue is harvested,” Chazenbalk said. “This research offers a new and exciting source of fat stem cells with pluripotent characteristics, as well as a new method for quickly isolating them. These cells also appear to be more primitive than the average fat stem cells, making them potentially superior sources for regenerative medicine.”
Currently, embryonic stem cells and induced pluripotent stem cells – skin cells turned into embryonic-like cells – are the two main sources of pluripotent cells. However, both types can exhibit an uncontrolled capacity for differentiation and proliferation, leading to the formation of unwanted teratoma, or tumors. Little progress has been made in resolving that defect, Chazenbalk said.
Muse cells originally were discovered by a research group at Tokohu University in Japan and were derived from bone marrow and skin, rather than fat. That research group showed that Muse cells did not produce teratomas in animal models. Further research on the Muse-AT cells isolated at UCLA will need to be done to determine whether that cell population avoids production of teratomas.
In addition to providing a potential source of cells for regenerative medicine, Chazenbalk said the Muse-AT cells may provide a better understanding of cancer cells, the only other cells known to display such stress resistance.
Going forward, Chazenbalk and his team will use Muse-AT cells in animal models to regenerate damaged or dysfunctional tissue to determine how efficiently they grow and perform in the body and to gauge their potential for future clinical use.
“Because lipoaspiration is a safe and non-invasive procedure and Muse-AT cell isolation requires a simple yet highly efficient purification technique, Muse-AT cells could provide an ideal source of pluripotent-like stem cells,” the study states. “Muse-AT cells have the potential to make a critical impact on the field of regenerative medicine.”