Abstract 14

PURPOSE: There is intense interest in adipose-derived stem cells in recent years due to their importance in normal tissue homeostasis and their potential in fat grafting, stem cell therapies and tissue engineering. In parallel, the incidence of both morbid obesity and diabetes mellitus has increased worldwide but relatively little is known about how these conditions affect stem cell health and function. Recently we identified a novel mechanism through which obesity and diabetes affect health by depletion of specific subpopulations of stem cells within adipose tissue.1 Here we examine the impact of obesity and diabetes mellitus on adipose-derived stem cell health and function in humans and to what degree such impairments can be rectified through conventional therapies such as diet, exercise and bariatric surgery. METHODS: Adipose tissue samples were taken from over 100 patients during elective surgery (bariatric, post-bariatric and controls) with appropriate institutional ethics and consent. Patients were sampled serially when possible. In parallel, the effects of exercise and diet on the recruitment of stem cells and subpopulations within adipose tissue were examined in human and murine studies respectively. Blood samples were taken pre- and post-exercise in 12 patients and then again following a 4-week exercise program in half the group with the remainder forming untrained controls. The effect of diet was studied using a diet induced obesity model (60% fat in diet) with cross-over to normal chow across both short term (6 months) and long-term (18 months) periods with all experiments duplicated to confirm the results. The stromal vascular fraction of subcutaneous fat was isolated by fluorescence cytometry (CD45-CD31-CD34+), then single cell microfluidics was performed with hierarchical cluster-based analysis to examine for subpopulation changes between groups. Subpopulations where validated at a protein level by mass cytometry (CYTOF), including markers for stemness (Sox-2, Nanog, Oct 3/4) and relevant subpopulation surface markers (CD26, CD55). Subpopulations were further validated through additional cluster-based analyses including ViSNE, SPADE and CITRUS algorithms. RESULTS: Obesity and diabetes mellitus are both associated with a significant reduction in a specific mesenchymal stem cell subpopulation that is potently pro-angiogenic. Subpopulation depletion is strongly associated with impaired wound healing (p<0.05, One-way ANOVA). Despite correction of diabetic status and massive weight loss, subpopulation depletion is not reversed in post-bariatric patients (p<0.0001, ANOVA). Exercise did not increase recruitment of these stem cell subpopulations and diet was unable to restore stem cell subpopulations to pre-morbid levels. CONCLUSION: Stem cell subpopulation depletion offers a novel basis for the increased morbidity and mortality seen in morbid obesity and diabetes mellitus and for the resistance of subpopulation depletion to treatment using existing therapies (bariatric surgery, diet and exercise). These data offer a new paradigm to our understanding of stem cell health and function in obesity and diabetes mellitus, prompting the need for novel therapies to address this unmet clinical need. References: 1. Rennert RC, et al. Microfluidic single-cell transcriptional analysis rationally identifies novel surface marker profiles to enhance cell-based therapies. Nat Commun, 2016. 7:11945. M.W. Findlay: None. M. Rodrigues: None. M. Sorkin: None. S. Khong: None. R.R. Rennert: None. P. Than: None. M. Januszyk: None. C. Davis: None. E. Brett: None. R. Schier: None. P. Zimmer: None. B. Riedel: None. H. Lorenz: None. H. Rivas: None. J.M. Morton: None. G.C. Gurtner: None.