Adipose-derived stem cells (ASCs) represent a promising cell source in the field of tissue engineering and regenerative medicine. Due to the wide availability and multipotent ability of ASCs to differentiate into tissues such as bone, cartilage, muscle, and adipose, ASCs may serve a wide variety of regenerative medicine applications. Accordingly, ASCs have been utilized in studies addressing osteoarthritis, diabetes mellitus, heart disease, and soft tissue regeneration and reconstruction after mastectomy and facial trauma. Traditional, static, two-dimensional cell culture of ASCs do not allow for mature adipocyte differentiation or long-term maintenance of adipocytes in vitro. In order to study metabolic diseases, such as type II diabetes mellitus, a three-dimensional scaffold for in vitro adipocyte maintenance is necessary.
In collaboration with the Bioreactor Laboratory at the McGowan Institute for Regenerative Medicine, our laboratory has developed the use of a hollow fiber-based bioreactor for three-dimensional, dynamic perfusion of ASCs and adipose tissue formation ex vivo, creating a stable system in which long-term culture of adipocytes is possible, providing a model useful for potential drug discovery and tissue engineering applications, specifically those addressing type II diabetes mellitus. The studies presented in this dissertation aim to assess metabolic activity and differentiation of ASCs from patients with or without type II diabetes in the bioreactor system; engineer a long-term culture environment relevant to physiological type II diabetic and non-diabetic conditions ex vivo; optimize tissue growth homogeneity; enhance adipogenesis within the bioreactor culture with the use of a decellularized adipose extracellular matrix (ECM) hydrogel.
ASCs derived from patients with type II diabetes at time of isolation were found to behave metabolically similar and appear architecturally comparable to those derived from patients without type II diabetes mellitus when differentiated and maintained as adipocytes in the bioreactor system. When cultured at a physiologically relevant glucose level matching that of healthy patients or patients with type II diabetes, ASCs were able to proliferate, differentiate into adipocytes, and be maintained within the bioreactor system for at least one week. A decellularized adipose ECM hydrogel was established and applied to the bioreactor cultures; however, due to technical challenges, no firm conclusions can be made.
The microenvironment by which ASCs are surrounded is critical for cell differentiation and growth. Engineering and control of such microenvironment is possible within the hollow fiber-based, three-dimensional, dynamic perfusion bioreactor culture system, proving to be a promising model for potential drug discovery and therapeutics. Future directions include further evaluation of ASC differentiation and adipocyte metabolism within type II diabetic environments, application of established decellularized adipose ECM hydrogels to wound healing treatments and adipose graft volume retention.