Skeletal stem cell and bone implant interactions are enhanced by LASER titanium modification

Abstract

Purpose: To evaluate the osteo-regenerative potential of Titanium (Ti) modified by Light Amplification by Stimulated Emission of Radiation (LASER) beam (Yb-YAG) upon culture with human Skeletal Stem Cells (hSSCs1). Methods: Human skeletal cell populations were isolated from the bone marrow of haematologically normal patients undergoing primary total hip replacement following appropriate consent. STRO-1+ hSSC1 function was examined for 10 days across four groups using Ti discs: i) machined Ti surface group in basal media (Mb2), ii) machined Ti surface group in osteogenic media (Mo3), iii) LASER-modified Ti group in basal media (Lb4) and, iv) LASER-modified Ti group in osteogenic media (Lo5). Molecular analysis and qRT-PCR as well as functional analysis including biochemistry (DNA, Alkaline Phosphatase (ALP6) specific activity), live/dead immunostaining (Cell Tracker Green (CTG7)/Ethidium Homodimer-1 (EH-18)), and fluorescence staining (for vinculin and phalloidin) were undertaken. Inverted, confocal and Scanning Electron Microscopy (SEM) approaches were used to characterise cell adherence, proliferation, and phenotype. Results: Enhanced cell spreading and morphological rearrangement, including focal adhesions were observed following culture of hSSCs1 on LASER surfaces in both basal and osteogenic conditions. Biochemical analysis demonstrated enhanced ALP6 specific activity on the hSSCs1-seeded on LASER-modified surface in basal culture media. Molecular analysis demonstrated enhanced ALP6 and osteopontin expression on titanium LASER treated surfaces in basal conditions. SEM, inverted microscopy and confocal laser scanning microscopy confirmed extensive proliferation and migration of human bone marrow stromal cells on all surfaces evaluated. Conclusions: LASER-modified Ti surfaces modify the behaviour of hSSCs.1 In particular, SSC1 adhesion, osteogenic gene expression, cell morphology and cytoskeleton structure were affected. The current studies show Ti LASER modification can enhance the osseointegration between Ti and skeletal cells, with important implications for orthopaedic application.