Synthetic niche substrates engineered via two-photon laser polymerization for the expansion of human mesenchymal stromal cells.

The present study reports on the development of an innovative culture substrate, micro-fabricated by two-photon laser polymerization (2PP) in a hybrid organic-inorganic photoresin. It was previously demonstrated that this substrate is able to guide spontaneous homing and colonization of mesenchymal stromal cells by the presence of synthetic microniches. Here, the number of niches covering the culture substrate was increased up to 10% of the total surface. Human bone marrow-derived mesenchymal stromal cells were expanded for 3 weeks and then their proliferation, clonogenic capacity and bilineage differentiation potential towards the osteogenic and adipogenic lineage were evaluated, both by colorimetric assays and by real-time polymerase chain reaction. Compared with cells cultured on glass substrates, cells expanded on 2PP substrates showed a greater colony diameter, which is an index of clonogenic potential. Following medium conditioning on 2PP-cultured cells, the expression of RUNX2 and BSP genes, as well as PPAR-gamma, was significantly greater than that measured on glass controls. Thus, human cells expanded on the synthetic niche substrate maintained their proliferative potential, clonogenic capacity and bilineage differentiation potential more effectively than cells expanded on glass substrates and in some aspects were comparable to non-expanded cells. © 2016 The Authors Journal of Tissue Engineering and Regenerative Medicine Published by John Wiley & Sons Ltd.