Arthritis is the result of degeneration of cartilage (the tissue lining the joints) and leads to pain and limitation of function. Arthritis and other rheumatic diseases are among the most common of all health conditions and are the number one cause of disability in the United States. The annual economic impact of arthritis in the U.S. is estimated at over $65 billion, representing more than 2% of the gross domestic product. The prevalence of arthritic conditions is also expected to increase as the population increases and ages in the coming decades. Current treatment options for osteoarthritis include pain relief and joint replacement surgery. Stem cells have tremendous potential for treating disease and replacing or regenerating the diseased tissue. This grant proposal will generate results that will be valuable in weighing options for using stems cells. Research is ongoing in the causes of aging in the stems cells and how cell replacement might effectively treat the causes of osteoarthritis. The first aim of our study will be to induce stem cells to produce cartilage-like tissue. We propose to identify the differences in the type and quantity of cartilage tissue produced by embryonic stem cells and adult stem cells obtained from healthy and arthritic donors. These experiments will help us understand how stem cells age and whether stem cell function changes with disease. These results will be very valuable in identifying the potential for treatment using stem cells from different sources and donors. The second aim of our study is to determine whether implanting stem cells in a cartilage defect in normal cartilage produces the same result as implanting in arthritic cartilage. Since arthritic cartilage produces biochemical factors different from normal cartilage we expect the stem cell response to change. We will find out if the change in response is beneficial or detrimental to the production of new cartilage tissue. In addition, we will study the effect of stem cells on arthritic cartilage. It has been suggested that stem cells fight disease and repair tissues in the body. If this is true we anticipate that stem cells implanted in arthritic cartilage may also treat the arthritis in addition to producing tissue to heal the defect in the cartilage. An approach that heals cartilage defects as well as treats the underlying arthritis would be very valuable. If our research is successful this could lead to new ways to treat cartilage with or without stem cells. Treating cartilage degeneration would have a positive impact on the large numbers of patients who suffer from arthritis as well as in reducing the economic burden created by arthritis.
Statement of Benefit to California:
California has been at the forefront of biomedical research for more than 40 years and is internationally recognized as the biotechnology capital of the world. The recent debate over the moral and ethical issues of stem cell research have slowed the progress of scientific discoveries in this field. The CIRM is a unique institute that fosters ethical stem cell research in California. If successful the CIRM may serve as a role model for similar programs in other states or countries. This grant proposal falls under the mission statement of the CIRM of funding innovative and untested research. The SEED proposal will generate preliminary yet novel results in the treatment of cartilage degeneration and osteoarthritis and extend the potential use of tissue engineered products from stem cells. At a minimum new insights in the role of stem cell as anti-arthritic agents will be gained. If successful, this will reinforce the role of the CIRM and help maintain the leading position of California at the cutting edge of biomedical research.
SYNOPSIS: In this proposal the investigators wish to compare chondrocytes generated from hESC, hMSC and articular cartilage; and monitor the effect of explant of ESC derived cells in different microenvironments, ie normal aged and arthritic environments. ESCs to be used have been generated by Dr Snyder under defined conditions. SIGNIFICANCE AND INNOVATION: Although studies in which ESCs are evaluated for differentiation towards specific lineages are important from a developmental biology standpoint, the clinical use of ESCs as a source of cells for tissue regeneration will likely be more needed for certain cell types / tissues than others. As MSCs can generate chondrocytes readily, it remains to be determined whether ESCs will ever serve as a cell population from which to generate chondrocytes. This would only be the case if studies demonstrate significant superiority of ESCs over MSCs in the generation of chondrocytes. Hence, the importance of the work proposed here lays in the comparative nature of the studies. The proposed approaches are based on knowledge of factors that govern chondrocyte differentiation, but are not particularly innovative. This proposal outlines a sophisticated approach to comparing the chondrogenic potential of hES cells, comparing them to other stem cell populations with known chondrogenic potential. It also utilizes a novel culture substrate, human osteochondral disks, to evaluate the behavior of stem cells in the environment where they would be implanted clinically. The specific aims of the proposal are (1) to identify differences in chondrogenic potential between hES cells, adult marrow-derived MSC, and adult articular cartilage chondrocytes and (2) Monitor chondrogenic patterns after implantation of hESC in normal, aged, or arthritic cartilage explants Not much work has been done with HES cell differentiation into chondrocytes, so the work is innovative in that regard. The approach using actual human osteochondral disks to study the behavior of the stem cells in a physiologically relevant environment is particularly nice. STRENGTHS: The investigators proposing the studies have a longstanding interest and expertise in cartilage differentiation. The strengths are also in the fact that comparative studies will be done using two adult sources of cells and ESCs, and that the influence of age and disease from the donors of the two adult stem cell sources will be determined. An other strength is the model to be used, namely osteochondral explants from different patients (young, old and arthritic patients) to assess whether the environment affects the stem cell derived chondrocytes, and whether addition of "ÿoung" chondrocytes to these explants can modify the arthritic process that is occurring. Although the PI does not state it in exactly this way, the strength of the proposal is the use of actual human cartilage as a substrate for transplantation of hES cells, since these kinds of experiments are exactly the intermediate experiments needed before rational stem cell therapies can be translated. The discussion of the differentiation shows a firm grasp of the molecular biology related to the project, and the experience of the PI with 3-D structures and other stem cells increases the likelihood of success. The PI is well funded and all the equipment and procedures are in place to aid in the project. WEAKNESSES: It is unclear what the endpoints are for the studies proposed in aim 2. The possibility that ES-derived cells will form teraotmas is not addressed nor or methods proposed to attempt to purify the cartilage cells or precursors to avoid such a problem. No methods are proposed to enhance mesoderm and mesenchyme generation of ESCs, which wil be needed to efficiently generate chondrocytes devoid of other cell types. Page 6: The look at cytokines as a major end-point of analysis is a little puzzling since presumably there will not many be immune cells in the preparations. Perhaps this should be re-thought with a focus more on pertinent receptors (TLR4 for example). Since the submission of this proposal, several studies have appeared in the literature about chondrocyte differentiation from HES cells, and these should be consulted. DISCUSSION: A question for this application is why use hESC to study cartilage and bone formation? The issue is whether it is worthwhile (given expense, etc.) to pursue ESCs over other sources of cartilage and bone. A strength of this proposal lies in the "in-between" comparative experiments where the influence of donor age and disease states will be assessed. Reviewer 2 liked that the applicant considered that local environment might have toxic effect on chrondrogenesis. The therapeutic potential of this work was questioned since extant sources of cartilage seem to work well.