Exploring the osteoconductive effect of silanol groups by using human adipose stem cells

Current methods for bone tissue engineering are concentrated in the in vitro proliferation and osteogenic differentiation of stem cells seeded onto 3D scaffolds, as these are key elements to achieve tissue regeneration. One critical strategy in bone tissue engineering is to develop 3D environments that can provide the necessary cues for guiding cell recruitment and driving tissue regeneration by mimicking the bone microenvironment and eventually eliminate the need to seed cells previously to implantation. Silicon is known to have an influence on calcium phosphate deposition and on the differentiation of bone precursor cells^1,2. In previous work³ we demonstrated that a wet spun fiber mesh based on a blend of corn-starch with polycaprolactone (30/70 wt.%, SPCL) with silanol (Si-OH) groups sustained human adipose stem cells (hASC) proliferation and osteogenic differentiation when cultured under dynamic conditions. The present study attempts to analyze in more detail the role of Si-OH groups on the osteogenic gene expression of hASC. Thus the in vitro evaluation of SPCL with and without Si-OH groups was done with human ASCs cultured in either a-MEM or osteogenic medium for up to 21 days. Results showed that hASC readily proliferated and migrated into the interior of the wet-spun fibre mesh scaffolds, and calcium and phosphate on the cell surfaces were detected, within only 14 days of culture. Moreover, the studies in vitro indicated an enhancement of osteogenic gene expression of hASC when cultured in the presence of Si-OH groups. The present work shows that combining wet-spinning technology with a calcium silicate solution as a non-solvent allows designing scaffolds with key cues to render an osteoconductive behavior as the classic ceramic materials for bone regeneration. Additionally, these results suggests that silicon and calcium either individually or in combination may relevantly contribute to properly drive hASC towards the osteoblastic phenotype and highlight the potential of those ions in the control of cellular response such as cell differentiation and/or in stem cells recruitment upon implantation of a cell-free scaffold.

References:
1. Hoppe A., et al., Biomaterials 32: 2757–2774, 2011.
2. Beck Jr G.R., et al., Nanomedicine: Nanotechnology, Biology, and Medicine, 1–11, 2011.
3. Rodrigues A.I., et al., Acta Biomaterialia, 2012, DOI: 10.1016/j.actbio. 2012.05.025.