Biomaterials that promote cell-cell interactions enhance the paracrine function of MSCs.

Mesenchymal stromal cells (MSCs) secrete paracrine factors that play crucial roles during tissue regeneration. Whether this paracrine function is influenced by the properties of biomaterials in general, and those used for cell delivery in particular, largely remains unexplored. Here, we investigated if three-dimensional culture in distinct microenvironments - nanoporous hydrogels (mean pore size ∼5 nm) and macroporous scaffolds (mean pore size ∼120 μm) - affects the secretion pattern of MSCs, and consequently leads to differential paracrine effects on target progenitor cells such as myoblasts. We report that compared to MSCs encapsulated in hydrogels, scaffold seeded MSCs show an enhanced secretion profile and exert beneficial paracrine effects on various myoblast functions including migration and proliferation. Additionally, we show that the heightened paracrine effects of scaffold seeded cells can in part be attributed to N-cadherin mediated cell-cell interactions during culture. In hydrogels, this physical interaction between cells is prevented by the encapsulating matrix. Functionally blocking N-cadherin negatively affected the secretion profile and paracrine effects of MSCs on myoblasts, with stronger effects observed for scaffold seeded compared to hydrogel encapsulated cells. Together, these findings demonstrate that the therapeutic potency of MSCs can be enhanced by biomaterials that promote cell-cell interactions.