Introduction

Endochondral ossification (EO) is the process of bone development via a cartilage template. It involves multiple stages, including chondrogenesis, mineralisation and angiogenesis. Importantly, how cartilage mineralisation affects angiogenesis during EO is not fully understood. Here we aimed to develop a new in vitro co-culture model to recapitulate and study the interaction between mineralised cartilage generated from human mesenchymal stromal cells (hMSCs) and microvascular networks.

Harnessing the potential of mesenchymal stem cell (MSC) mediated endochondral ossification for the repair of large bone defects represents a promising avenue of investigation as an alternative option to autologous bone transplantation. To date, it has been shown that undifferentiated MSCs are somewhat immune-privileged. In order to induce bone formation from MSCs by endochondral ossification it is usually necessary to first differentiate these cells chondrogenically. However, the status of differentiated cells is less clear than that of undifferentiated MSCs. Furthermore, the fate of implanted bone forming constructs in an allogeneic setting is not known. The potential to use allogeneic MSCs for large bone defect repair would offer opportunities to researchers to develop new therapies using more potent MSC sources and in a more readily available manner with regard to the patient. I will present our research investigating the interactions between chondrogenically primed MSCs and immune cell subsets, namely T cells and dendritic cells. Furthermore, I will discuss the ability of human paediatric MSCs to form bone in the in vivo allogeneic setting.