Characterisation of Priming Mechanisms for Bone Engineering at the Cellular and Molecular Level

Fractures of the long bones are the most common large organ trauma worldwide. In about 5% of all cases the broken bone fails to heal, resulting in a so-called non-union defect. These can be caused by a lack of potent skeletal progenitor cells at the defect site. Currently, there is no reliable treatment strategy available for these patients. Therefore, tissue engineering (TE) represents a promising approach. However, current expansion protocols for TE involve the use of (bovine) serum-containing media for its proliferative effects. This directly impairs clinical applicability since in addition to being xenogeneic, bovine serum is well known for its batch-to-batch variability.

To circumvent this issue our lab has recently developed a serum-free in vitro priming protocol based on a chemically defined medium (CDM) which enhances the progenitor potential of in vitro expanded human periosteum-derived cells (hPDCs). The use of a serum-free medium provides multiple advantages over serum-containing media, including batch-to-batch consistency, biological uniformity and the absence of foreign agents. Furthermore, the current formulation of the CDM is free of growth factors and is thus highly suitable for the controlled culture of progenitor cells and the investigation of ongoing cellular and molecular processes.

In this project, a developmental engineering approach will be combined with highly advanced next-generation sequencing technologies to determine the effects of serum-free priming and the culture environment on the cellular state of hPDCs. The fracture callus will be characterised as a reference map to serve as a benchmark for biological relevance of identified cell states. In a final step, we aim to use these extensive datasets to find which ligands are essential to maintain hPDC osteochondral progenitor potential in culture and formulate a serum-free medium for their expansion.