Human adipose mesenchymal stromal cells growing into PCL‐nHA electrospun scaffolds undergo hypoxia adaptive ultrastructural changes

Human Adipose‐Derived Mesenchymal Stem/Stromal Cells (hAD‐MSCs) have great potential for tissue regeneration. Since transplanted hAD‐MSCs are likely to be placed in a hypoxic environment, culturing the cells under hypoxic conditions might improve their post‐transplantation survival and regenerative performance. The combination of hAD‐MSCs and PCL‐nHA nanofibers synergically improves the contribution of both components for osteoblast differentiation. In this work, we hypothesized that this biomaterial constitutes a hypoxic environment for hAD‐MSCs. We studied the cellular re‐arrangement and the subcellular ultrastructure by Transmission Electron Microscopy (TEM) of hAD‐MSCs grown into PCL‐nHA nanofibers, and we compared them with the same cells grown in two‐dimensional cultures, over tissue culture‐treated plastic, or glass coverslips. Among the most evident changes, PCL‐nHA grown cells showed enlarged mitochondria, and accumulation of glycogen granules, consistent with a hypoxic environment. We observed a 3.5 upregulation (p = 0.0379) of Hypoxia Inducible Factor (HIF)‐1A gene expression in PCL‐nHA grown cells. This work evidences for the first time intra‐cellular changes in three‐dimensional compared to two‐dimensional cultures, which are adaptive responses of the cells to an environment more closely resembling that of the in vivo niche after transplantation, thus PCL‐nHA nanofibers are adequate for hAD‐MSCs pre‐conditioning. Graphical and Lay Summary The combination of hAD‐MSCs and PCL‐nHA nanofibers synergically improves osteoblast differentiation. This work evidences for the first time ultrastructural changes in 3D compared to 2D cultures, which are adaptive responses of the cells to an environment more closely resembling that of the in vivo niche after transplantation, thus PCL‐nHA nanofibers are adequate for hAD‐MSCs pre‐conditioning.