Human bone marrow derived stem cell differentiation on 3D printed bioactive glass scaffolds

Bioactive glass particles have previously been found to stimulate new bone growth in vivo and have a long clinical track record. The effect of bioactive glasses on human bone marrow derived stromal cells (hBMSCs) has not been clearly ascertained previously. Recently, 3D printed scaffolds of the ICIE16 glass composition (49.46 mol% SiO₂, 36.6 mol% CaO, 6.6 mol% Na₂O, 6.6 mol% K₂O, 1.07 mol% P₂O₅) were found to produce high quality bone ingrowth in vivo in a rabbit model. This composition was chosen because it can be sintered into scaffolds without crystallisation. Here, we cultured hBMSCs on the 3D printed ICIE16 scaffolds to determine whether the scaffolds can support cell growth and osteogenic differentiation in vitro, with and without the presence of osteogenic supplements. This was compared to a control of culture media containing dissolution products of the bioactive glass scaffold. Our hypothesis was that the cells cultured on the scaffolds would undergo more osteogenic differentiation than cells cultured in media containing only the dissolution ions of the scaffolds, even without osteogenic supplements. hBMSCs cultured on ICIE16 scaffolds significantly increased expression of osteogenic differentiation and matrix formation markers, including Runx 2, Col1a1, Osteopontin, Osteocalcin and Alkaline Phosphatase, in comparison to monolayer cultures in basal conditions with bioactive glass dissolution products, at all time points up to 6 weeks. Six weeks was chosen as it is the time scale for bone fracture healing. The presence of osteogenic supplements appeared to have synergetic effects with 3D scaffolds, especially during early stages of osteogenic differentiation (week 2 and 4). By week 6, there was no significant difference in the expression of osteogenic markers by hBMSCs cultured on ICE16 scaffolds with and without osteogenic supplements. These findings support our hypothesis and highlight that the 3D structure and the dissolution of ICIE16 bioactive glass ionic products both independently influence osteogenic differentiation of hBMSCs.