In VivoFunctional Evaluation of Tissue-Engineered Vascular Grafts Fabricated Using Human Adipose-Derived Stem Cells from High Cardiovascular Risk Populations

Abstract

Many preclinical evaluations of autologous small-diameter tissue-engineered vascular grafts (TEVGs) utilize cells from healthy humans or animals. However, these models hold minimal relevance for clinical translation, as the main targeted demographic is patients at high cardiovascular risk such as individuals with diabetes mellitus or the elderly. Stem cells such as adipose-derived mesenchymal stem cells (AD-MSCs) represent a clinically ideal cell type for TEVGs, as these can be easily and plentifully harvested and offer regenerative potential. To understand whether AD-MSCs sourced from diabetic and elderly donors are as effective as those from young nondiabetics (i.e., healthy) in the context of TEVG therapy, we implanted TEVGs constructed with human AD-MSCs from each donor type as an aortic interposition graft in a rat model. The key failure mechanism observed was thrombosis, and this was most prevalent in grafts using cells from diabetic patients. The remainder of the TEVGs was able to generate robust vascular-like tissue consisting of smooth muscle cells, endothelial cells, collagen, and elastin. We further investigated a potential mechanism for the thrombotic failure of AD-MSCs from diabetic donors; we found that these cells have a diminished potential to promote fibrinolysis compared to those from healthy donors. Together, this study served as proof of concept for the development of a TEVG based on human AD-MSCs, illustrated the importance of testing cells from realistic patient populations, and highlighted one possible mechanistic explanation as to the observed thrombotic failure of our diabetic AD-MSC-based TEVGs.

Evaluation of the stromal vascular fraction of adipose tissue as the basis for a stem cell-based tissue-engineered vascular graft

“…These cells will be referred to in this manuscript as SVF. For this study, a cultured AD-MSC control was established from each SVF donor by passage expanding a portion of the SVF four times 9, 15 . Using this procedure, SVF was available for graft fabrication within a matter of hours whereas AD-MSCs took upwards of 4 weeks.…”

“…Using this procedure, SVF was available for graft fabrication within a matter of hours whereas AD-MSCs took upwards of 4 weeks. Cell culture was performed in 75-cm 2 tissue culture flasks (Corning) under defined culture media 9, 15 and was replenished every 2-3 days. To passage expand cells, Trypsin-EDTA (#25200-056; Gibco) was utilized.…”

“…Briefly, a porous inner layer was created via thermally induced phase separation, which was then coated with an external mechanical sheath via electrospinning. This scaffold has already shown efficacy in the TEVG context using multiple cell types 1, 4, 9, 23 .…”

“…This is likely attributed to a number of practical rate-limiting barriers still present which hinder the clinical translation of TEVGs, such as appropriate testing of patient-specific cells (e.g. clinically appropriate demographics) 9 , lack of feasible and consistent modes of manufacture to appropriate sizes, the need for culture expansion of cells to a suitable number, and lengthy fabrication time 10 . While the first two of these concerns have been validated in recent years 3, 9 , the necessity of in vitro culture and lengthy fabrication times which are employed by many TEVG designs 3 are still major concerns.…”

“…clinically appropriate demographics) 9 , lack of feasible and consistent modes of manufacture to appropriate sizes, the need for culture expansion of cells to a suitable number, and lengthy fabrication time 10 . While the first two of these concerns have been validated in recent years 3, 9 , the necessity of in vitro culture and lengthy fabrication times which are employed by many TEVG designs 3 are still major concerns. Specific concerns for clinical application include excess waiting time for the patient, significant costs (such as cell culture reagents and personnel), and potential cellular transformation or contamination.…”