A simple rocker-induced mechanical stimulus upregulates mineralization by human osteoprogenitor cells in fibrous scaffolds.

Biodegradable electrospun polycaprolactone (PCL) scaffolds can be used to support bone-forming cells and could fill a thin bony defect, such as in cleft palate. Oscillatory fluid flow (OFF) has been shown to stimulate bone production in human progenitor cells in monolayer culture. The aim of this study was to examine whether bone matrix production by primary human mesenchymal stem cells from bone marrow (hBMSC) or jaw periosteal tissue (HJP) could be stimulated using OFF supplied by a standard see-saw rocker. This was investigated for cells in 2D culture and within electrospun PCL scaffolds. From day 4 of culture onwards, samples were rocked at 45 cycles/min for 1 hour per day, 5 days per week (rocking group). Cell viability, calcium deposition, collagen production, alkaline phosphatase activity and vascular endothelial growth factor (VEGF) secretion were evaluated to assess the ability of the cells to undergo bone differentiation and induce vascularisation. Both cell types produced more mineralized tissue when subjected to rocking and supplemented with dexamethasone. Mesenchymal progenitors (hESMP) and hBMSC in 3D scaffolds up-regulated mineral deposition after rocking culture as assessed by micro-computed tomography (μCT) and alizarin red staining. Interestingly, VEGF secretion which has previously been shown to be mechanically sensitive was not altered by rocking in this system and was inhibited by dexamethasone. Rocker culture may be a cost effective, simple pre-treatment for bone tissue engineering for small defects such as cleft palate.