Engineering new bone via a minimally invasive route using human bone marrow derived stromal cell aggregates, micro ceramic particles and human platelet rich plasma gel

There is a rise in the popularity of arthroscopic procedures in orthopedics. However, the majority of cell based bone tissue engineered constructs rely on solid pre-formed scaffolding materials, which require large incisions and extensive dissections for placement at the defect site. Thus, they are not suitable for minimally invasive techniques. The aim of this study was to develop a clinically relevant, easily moldable, bone tissue engineered construct (TEC), amenable to minimally invasive techniques, using human mesenchymal stromal cells (hMSC) and calcium phosphate micro particles in combination with an in-situ forming platelet rich plasma (PRP) gel obtained from human platelets. Most conventional TECs rely on seeding and culturing single cell suspensions of hMSCs on scaffolds. However, for generating TECs amenable to the minimally invasive approach, it was essential to aggregate the hMSCs in vitro prior to seeding them on the scaffolds as unaggregated MSCs did not generate any bone. 24 hours of in vitro aggregation was determined to be optimal for maintaining cell viability in vitro and bone formation in vivo. Moreover, no statistically significant difference was observed in the amount of bone formed when the TECs were implanted via an open approach or a minimally invasive route. TECs generated using MSCs from three different human donors generated new bone through the minimally invasive route in a reproducible manner, suggesting that these TECs could be a viable alternative to pre-formed scaffolds employed through an open surgery for treating bone defects.