The description of pluripotent cells in adipose tissue has led to the concept that adipose tissue may provide a novel autologous source of cells with significant potential for tissue modification. Such adipose stromal cells (ASCs) can be obtained in large quantities, in the range of 108 to 109 cells, following routine liposuction of subcutaneous adipose tissue. This ready accessibility in turn has suggested the notion that they might provide for a particularly feasible and attractive form of autologous cell therapy. Work in our laboratory supported by our prior Merit Review, as well as that of others, has clearly demonstrated that ASCs can increase tissue perfusion and limit ischemic tissue damage in several circumstances, by secretion of angiogenic and anti-apoptotic factors. Recently, we have also found that ASCs are capable of stabilizing endothelial networks in vitro as well as robustly synergizing with endothelial cells (EC) to participate in the in vivo formation of new vessels. Additionally, this observation led us to hypothesize that the synergy between ASC and EC would provide a practical approach to tissue vascularization for implants or regional ischemia. Our recent findings that ASCs in culture can promote sustained secretory function of pancreatic islets, and that ASCs assemble vascular networks when co-implanted with both endothelial cells and islets, has prompted us to further evaluate the mechanisms by which these cells assemble vessels and modulate islet responses. The overall hypothesis of this proposal is thus that ASCs are uniquely accessible and expandible pluripotent cells that have the capacity to differentiate along pathways giving rise to vascular mural cells, and which can facilitate in vivo vasculogenesis and cell survival in the context of implanted islets.
The specific aims that will be pursued in order to test this hypothesis are 1.) Evaluate the mechanisms, dynamics, and key factors responsible for governing ASC-mediated vascular network formation by ECs in vitro and in vivo;2.) Evaluate the capacity of ASC or ASC subpopulations to support pancreatic islet function in vitro and in vivo by direct paracrine support;and to further preserve islet function by assembly of a chimeric human vascular network by ASC and EC in vivo;and 3.) Determine the effect of diabetes and aging on the competency of human ASCs to participate in chimeric vasculogenesis in vivo, and on the signalling function of the master angiogenic control factors, HIF-1a and HIF-1bin ASCs. This study will help to determine the extent to which ASC and EC co-transplantation can assist with tissue survival;and by using islet transplantation as a model, will permit an assessment of whether islet transplantation can be significantly augmented by ASCs and vascular networks which they can help to form. In addition, this study will clarify the potential of autologous ASC obtained from patients with diabetes to contribute to tissue survival via either paracrine effects or vascularization;and identify key molecular mechanisms underlying functional impairment of ASC in diabetes. Marked impairment in these functions would highlight the need for approaches involving either targeted modification of autologous ASC, or allogeneic ASC.
Our study will provide insight into how to use the stem cells located in fat tissue to assist in creating blood vessel structures to help provide blood supply to tissues that require it, and in particular to islets that are transplanted. Since we are working with cell preparation devices / methods that are appropriate for human use, the insights developed in this study will be directly translatable to Veterans. Specifically, we anticipate that the approaches we are studying will apply to Veterans that have problems due to poor blood flow;such as poor wound healing;and to diabetic Veterans who may be able to benefit from islet transplantation to treat or actually cure their diabetes. The findings from this study will point the way to optimized methods for transplanting islets along with cells that can assemble vascular structures;and will also determine whether cells from all patients can be used, or whether cells from younger or healthier patients must be explored, and why. Successful work to treat diabetes and diabetic vascular disease will markedly improve the effectiveness, and may indeed decrease longterm costs of healthcare in the Veterans Administration system.