Expansion of human bone marrow stromal cells on poly-(dl-lactide-co-glycolide) (PDLLGA) hollow fibres designed for use in skeletal tissue engineering

Strategies to expand human bone marrow stromal cells (HBMSC) for bone tissue engineering are a key to revolutionising the processes involved in three-dimensional skeletal tissue reconstruction. To facilitate this process we believe the use of biodegradable porous poly(dl-lactide-co-glycolide) (PDLLGA) hollow fibres as a scaffold used in combination with HBMSC to initiate natural bone repair and regeneration offers a potential solution. In this study, the biocompatibility of 75:25 PDLLGA fibres with HBMSC and the capacity of a PDLLGA fibre-associated HBMSC-monolayer to establish an osteogenic phenotype in vivo was examined. A high proportion of HBMSC survived when expanded on PDLLGA fibres for 6 days, with only 10% of the propidium iodide (pI)-labelled population represented in the sub-G1 DNA peak on analysis by flow cytometry. Tracking carboxy-fluorescein diacetate, succinimidyl ester (CFSE)-labelled HBMSC by flow cytometry indicated that HBMSC attachment to the PDLLGA fibres does not interfere with their rate of proliferation. Furthermore, in response to osteogenic stimuli, HBMSC expanded on PDLLGA fibres can differentiate, as expected, along the osteogenic lineage with associated alkaline phosphatase activity. Following implantation into SCID mice, osteogenic-conditioned PDLLGA fibre–HBMSC graft resulted in type I collagen deposition and associated bone mineralisation and osteoid formation, as evidenced by immunohistochemistry and histology. These studies provide evidence that porous PDLLGA hollow fibre–HBMSC graft is an innovative biomaterial that offers new approaches to mesenchymal cell expansion, which could be utilised as a scaffold for skeletal tissue generation.