Abstract 72: Subselected Adipocyte Progenitor Niche Cells Show Superior Incorporation and Function in a Mouse Model

Abstract

PURPOSE: Previous work from our group has reported that human fat elaborates vascular sprouts when placed in angiogenic media. These vascular sprouts constitute a unique niche for specific cells (Adipocyte Progenitor Niche Cells =APNC) which, when then subjected to adipogenic media, differentiate into adipocytes. This study shows that these subselected adipocytes have superior fat cell function when grafted into a mouse host, as assessed by functional and biochemical parameters that report degree of differentiation and vascularization (levels of human adiponectin in mouse serum and human and mouse PLIN1 and CDH5 mRNA levels in graft). METHODS: Fat excised from a human panniculectomy specimen, was embedded to obtain vascular sprouts. APNCs were extracted, plated and at confluence exposed to control vehicle (APNC_control) or adipogenic cocktail (insulin, dexamethosome and IBMX) for three days (APNC_differentated). After 10 days cells were injected subcutaneously into the flanks of NOD mice. The following groups were compared: 1) APNC_differentated, 2) lipoaspirate from the same specimen, 3) APNC_control and 4) ADSCs prepared from the stromovascular fraction. Grafts were assayed for volume by micro-CT, and functional integration by human serum adiponectin. In addition, immunohistochemistry and RT-PCR for both human and mouse cadherin5 (CDH5, endothelium) and perilipin 1 (PLIN1, adipose) were performed on grafts, and compared to human and mouse adipose tissue samples. RESULTS: Grafts formed from APNC_differentiated produced higher levels of adiponectin per unit volume compared to grafts formed from liposuctioned tissue. Grafts formed from APNC_differentiated were vascularized by host vessels to the same extent as endogenous mouse fat, and contained the same levels of perilipin as human fat. APNC_control, but not ADSCs were able to differentiate in-vivo to a lesser degree, as assessed by detection of human adiponectin in mouse serum. CONCLUSIONS: APNCs may represent more elegant way to retrieve the balanced niche of cells needed for adipocyte tissue engineering. In this pilot work, we show that APNCs produce a superior graft in terms of host incorporation and adipocyte function. Although processing time is an issue, if these cells prove to be more effective than other cells extracted from fat tissue, then they could be used to improve fat graft survival and/or deliver tissue regenerative stimuli in altered wound states. Further work will look to compare APNC_differentiated and APNC_control to the function of SVF and ADSC isolates (important control groups which are already used to ‘supercharge fat grafts) after they have been differentiated through the same media exchanges as APNC_differentiated.