Abstract 43: Evaluation The Effect Of Brain-death Physiology And Immunosuppression On Muscle-derived Stem Cell Expansion: Study On Porcine Tissue

Abstract

Background: Muscle-derived stem cells (MDSCs) are robust mediators of tissue regeneration that have been shown, in the literature, to exhibit multipotency in murine models. We hypothesize that immunosuppression, transplant physiology, and braindeath negatively affect the stem cell-niche in vascularized composite allografts (VCA) and may affect tolerance/rejection. Our study aim was to evaluate the growth of MDSCs under these conditions in a porcine VCA model. Methods: Muscle samples were harvested from the hind-limbs of pig before and after inducing brain-death. Samples were then harvested from both the VCA of another immunosuppressed pig and from the contralateral hindlimb of the same recipient 7 days after transplantation. MDSC populations were isolated using a modified collagen-sorting preplate technique. Imaging was obtained at various time points (t=0-10 days). Images were analyzed for confluence using ImageJ, statistical analysis was performed using Mathematica. Results: Time to confluence (t = 3, 5, 7, 10 days) between pre-braindeath and post-braindeath MDSC populations was significantly different (20%, 38%, 75%, 81% vs. 7%, 17%, 31%, 39%) (p<0.01). Time to confluence (t = 2, 4, 6, 8, 10 days) between immunosuppressed recipient and allograft MDSC populations was significantly different (3%, 6%, 13%, 45%, 55% vs. 7% 11%, 39%, 53%, 71%, respectively) (p=0.02). At t=10 days, mean confluence between pre-BD and immunosuppressed recipient MDSC populations was significantly different (81% vs. 55%) (p < 0.01); similarly, mean confluence between pre-braindeath and allograft MDSC populations was also significantly different (81% vs. 71%) (p = 0.01). At t=10 days, mean confluence between post-braindeath and immunosuppressed recipient MDSC populations was significantly different (39% vs. 55%) (p<0.01). Conclusion: Brain-death and immunosuppression significantly impair MDSC expansion and mitosis based on time to confluence; however, transplantation may ameliorate the negative effects of immunosuppression by acting as a surrogate for trauma and inflammation. Brain-death physiology appears to have the greatest impact on MDSC expansion in our study. Further studies will focus on immune modulation and scaffold growth in porcine MDSC populations.