title: Oxygen tension regulates the osteogenic, chondrogenic and endochondral phenotype of bone marrow derived mesenchymal stem cells.
abstract: The local oxygen tension is a key regulator of the fate of mesenchymal stem cells (MSCs). The objective of this study was to investigate the effect of a low oxygen tension during expansion and differentiation on the proliferation kinetics as well as the subsequent osteogenic and chondrogenic potential of MSCs. We first hypothesised that expansion in a low oxygen tension (5% pO(2)) would improve both the subsequent osteogenic and chondrogenic potential of MSCs compared to expansion in a normoxic environment (20% pO(2)). Furthermore, we hypothesised that chondrogenic differentiation in a low oxygen environment would suppress hypertrophy of MSCs cultured in both pellets and hydrogels used in tissue engineering strategies. MSCs expanded at 5% pO(2) proliferated faster forming larger colonies, resulting in higher cell yields. Expansion at 5% pO(2) also enhanced subsequent osteogenesis of MSCs, whereas differentiation at 5% pO(2) was found to be a more potent promoter of chondrogenesis than expansion at 5% pO(2). Greater collagen accumulation, and more intense staining for collagen types I and X, was observed in pellets maintained at 20% pO(2) compared to 5% pO(2). Both pellets and hydrogels stained more intensely for type II collagen when undergoing chondrogenesis in a low oxygen environment. Differentiation at 5% pO(2) also appeared to inhibit hypertrophy in both pellets and hydrogels, as demonstrated by reduced collagen type X and Alizarin Red staining and alkaline phosphatase activity. This study demonstrates that the local oxygen environment can be manipulated in vitro to either stabilise a chondrogenic phenotype for use in cartilage repair therapies or to promote hypertrophy of cartilaginous grafts for endochondral bone repair strategies.
authors.affiliation: Trinity Centre for Bioengineering, School of Engineering, Trinity College Dublin, Dublin 2, Ireland.
authors.forename: Eamon J
authors.initials: EJ
authors.lastname: Sheehy
authors.forename: Conor T
authors.initials: CT
authors.lastname: Buckley
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Kelly
mesh_terms: D000818:Animals; D001854:Bone Marrow Cells / Q000166:cytology; D018929:Cell Culture Techniques; D002454:Cell Differentiation; D049109:Cell Proliferation; D020219:Chondrogenesis; D006025:Glycosaminoglycans; D059630:Mesenchymal Stem Cells / Q000502:physiology*; D010012:Osteogenesis; D010100:Oxygen; D010313:Partial Pressure; D013552:Swine; D023822:Tissue Engineering / Q000379:methods*
chemical_list: D006025:Glycosaminoglycans; C020341:glucosaminoglycans; D010100:Oxygen