This study addresses the cartilage defects resulting from injuries or from wear-and-tear that can eventually degenerate to osteoarthritis. This is a significant problem that impacts millions and costs in excess of $65B per annum in the US alone. Addressing this indication successfully holds potential for halting the progression of cartilage damage before it destroys the entire joint. We have shown that articular cartilage can be engineered with properties on par with native tissues using chondrocytes. Also, skin derived stem cells can be used to engineer new cartilage with significant mechanical integrity. Combining these findings, the new cellular therapy that this proposal seeks to develop is an autologous skin cell-derived combination product for articular cartilage repair. Three aims are proposed to advance this autologous, adult stem cell-based method: First, protocols shown to be efficacious in cartilage tissue engineering will be applied to skin-derived stem cells and show safety in the mouse model. Then, using a preclinical model, the desired biological response, toxicology, and durability will be verified. Finally, short-term safety and efficacy of cartilage repair will be examined in a different preclinical model. Successful completion of this DCF project will allow the start of preclinical studies in the sheep that demonstrate long-term safety and efficacy, as specified by the FDA.
Arthritis is the leading cause of disability in the US, affecting over 46 million Americans. Of these, over 5 million Californians are affected by this debilitating disease, with roughly 3 million that are women and over 2 million that are men. Additionally, Californian youth is also included in the estimated 30 million children who participate in organized sports activities, whose yearly costs for injuries have been projected to be $1.8 billion. For young patients with knee injuries, 75% exhibit superficial (grade I–II) and 25% exhibit deep (grade III–IV) cartilage lesions. Young patients not only need to retain mobility for many years in life but also new, tissue-sparing techniques. This proposal seeks to develop an autologous, adult stem cell-based therapy that addresses grade II-IV cartilage lesions. The source of these cells will be the skin, using minimally invasive procedures. The development of such a therapy would expand the clinical options available to Californians. The assembled team of academics, orthopaedic surgeons, and veterinary surgeons are based in the [REDACTED]. The refinement of this research will not only benefit [REDACTED] in terms of increasing competitiveness for NIH funding, but it will also allow for Californian companies to license the technology and therefore benefit economically.
Cartilage degeneration resulting from injuries or wear-and-tear leads to osteoarthritis, which impacts millions and costs in excess of $65B per annum. No long-term solutions exist for cartilage degeneration, but cellular therapies hold promise toward replacing degenerated cartilage with healthy tissue. This Development Candidate Feasibility Award is a first step toward the overall goal of developing a cell-based cartilage repair therapy using stem cells derived from the skin. The therapy would consist of using a skin biopsy to harvest dermis-isolated, adult stem cells (DIAS cells), which will undergo processing to yield neocartilage. This neocartilage will then be implanted into the patient’s joint to restore or improve mobility.
Work during this progress report period has been divided into project preparation and scientific progress. Project preparation includes setting up facilities and approvals for work with human DIAS cells, identifying sources and acquiring human skin for DIAS cell isolation, and hiring and training personnel. Scientific progress includes a publication on co-cultures using stem cells, work on culturing larger numbers of cells using low oxygen tension, comparing stem cells from human skin of different anatomical locations, and gaining an understanding of the niches where skin stem cells may reside.
The project now has a consistent source of human dermis tissue from which stem cells can be isolated. This includes skin containing hair follicles and also skin without follicles. Spherical culture of human skin-derived stem cells has been performed. It was found that directing stem cells into cells that make cartilaginous matrix can be more efficacious if done under low oxygen tension. Since much of the prior work on directing stem cells from the skin to form neocartilage has been done using animal-derived stem cells, in the next project period neocartilage will be formed using human stem cells instead. Technologies developed using animal models can thus be translated toward human use.
Resulting from injuries or wear-and-tear that leads to osteoarthritis, cartilage degeneration is a problem that costs in excess of $65B per annum. Toward developing a long-term solution for this vexing problem, cellular therapies hold the promise of replacing degenerated cartilage with healthy tissue. This Development Candidate Feasibility Award is a first step toward the overall goal of developing a cell-based cartilage repair therapy using stem cells derived from the skin. The therapy would begin with a biopsy of the patient’s own skin to harvest dermis isolated, adult stem cells (DIAS cells), which will undergo processing to yield neocartilage. This neocartilage will then be implanted into the patient’s joint to restore or improve mobility.
During this progress report period, a major milestone has been completed. Previously, DIAS cells have been isolated from various animal models, including sheep, goat, and rabbit. Comparing animal skin and human skin showed notable differences, including morphology, response to enzymatic digestion, and the rate at which cells attach to tissue culture plastic. As a result, protocols that successfully yielded DIAS cells using animal models could not be directly applied to isolating DIAS cells from human skin. During the first six months of this reporting period, human DIAS cells were isolated and used to engineer neocartilage. Characterizing the human DIAS cell population showed that cells shared similar characteristics with stem and progenitor cells previously identified by other groups as originating from various niches of the skin. Neocartilage constructs formed using human DIAS cells were found to contain twice as much glycosaminoglycans and three times more collagen; these are cartilage extracellular matrix component important in imparting mechanical function to the tissue. Neocartilage constructs generated from human DIAS cells also contained five times higher compressive modulus and close to twice the tensile modulus of constructs generated using sheep DIAS cells. The completion of this important milestone allowed for progression to the next milestones of this award.
Milestone 2 of this award consists of examining safety of the engineered constructs in a small animal model. For the scaling-up of constructs to be used in an athymic mouse study, an experiment was conducted to finalize our protocol for generating human DIAS cell constructs, using what have been learned both from Milestone 1 and also from literature sources. Three methods for generating neocartilage constructs were examined. While the resultant constructs did not differ in mechanical properties, one method nonetheless yielded constructs of more uniform size and greater cell and glycosaminoglycan content.
For milestones 3 and 4, the originally proposed studies were to implant autologous neocartilage constructs in intermediate and large animal studies to examine efficacy of repair. To improve the translational potential of this project, CIRM has requested that neocartilage constructs of human origin be used instead. To ensure that the implanted constructs are not rejected, progress during this reporting period also includes identifying methods to immunosuppress intermediate and large animal models.
To summarize, progress during this reporting period includes the completion of Milestone 1 and work toward all other milestones of this award. Additionally, two papers have been published thus far to disseminate scientific findings to the public.