Microgel microenvironment primes adipose-derived stem cells towards an NP cells-like phenotype.

Cell therapy of the degenerated intervertebral disc is limited by the lack of appropriate cell sources, thus new strategies for the differentiation of stem cells towards a nucleus pulposus (NP)-like phenotype need investigation. In the current study, it is hypothesized that spherical niche-like structures composed of type II collagen and hyaluronan (HA) mimic the NP microenvironment and promote the differentiation of adipose-derived stem cells (ADSCs) towards an NP-like phenotype. ADSCs are embedded in microgels of different concentrations of collagen II/HA. Cells' response to the different environments is studied by characterizing differences in cells' viability, morphology, and gene expression. After 21 days of culture, ADSCs maintain ± 80% viability in all the conditions tested. Moreover, microgels with higher concentration of collagen are stable and maintain cells in a rounder shape. In presence of differentiation media, cells are able to differentiate in all the conditions tested, but in a more pronounced manner in the microgel with a higher concentration of collagen. By tuning microgels' properties, it is possible to influence ADSCs' phenotype and ability to differentiate. Indeed, when cultured in high concentrations of collagen, ADSCs expresses high levels of collagen II, aggrecan, SOX9, and low levels of collagen I.