Abstract 10.55 PLATELET-RICH PLASMA VS. FETAL BOVINE SERUM IN ENGINEERING OF AXIALLY-VASCULARIZED OSTEOGENIC GRAFTS FROM HUMAN ADIPOSE-DERIVED CELLS TO TREAT AVASCULAR NECROSIS OF BONE

Abstract

INTRODUCTION: Avascular necrosis of bone (AVN) leads to sclerosis and collapse of bone and joints. Engineered, axially vascularized, human adipose-derived stromal vascular fraction (SVF) cell based osteogenic constructs have been shown to revitalize necrotic bone of clinically-relevant size in a challenging rat model of AVN. To reduce regulatory difficulties towards clinical translation, fetal bovine serum (FBS) was substituted by thrombin-activated platelet-rich plasma (tPRP). METHODS: SVF cells from 5 lipoaspirate were isolated and cultured onto porous hydroxyapatite scaffolds within a perfusion-based bioreactor system for 5 days. The medium was supplemented either with 10% FBS or 10% tPRP. The resulting constructs were inserted into devitalized bone cylinders mimicking AVN-affected bone. A ligated vascular bundle was inserted upon subcutaneous implantation of constructs in nude rats. After 1 and 8 weeks, vascularization and bone formation were analyzed. RESULTS: After 1 week, neither maximal distance of vessels from the bundle nor vascular density was significantly different. However, FBS cultured grafts revealed significantly more human vessel (hCD34) and osteoclasts compared to tPRP cultured grafts. Overall macrophages and M2 macrophages were not different between FBS and tPRP cultured grafts. After 8 weeks in vivo, 3/5 samples from FBS culture and 1/5 sample from tPRP culture showed bone formation. Roughly 40% of the osteocytes were of human origin (36% from FBS and 42% from tPRP culture). DISCUSSION: Despite promising results in literature, replacement of FBS by tPRP resulted in a reduced capacity of bone formation in our series. Further studies are necessary to analyze and improve the low bone formation capacity, possibly caused by the heterogeneity of the SVF donors and tPRP samples.