Effects of substrate stiffness on adipogenic and osteogenic differentiation of human mesenchymal stem cells

• Studied two primary lineages, i.e., adipogenic and osteogenic, modulating bone marrow
• Mimicking in vivo biochemical and biomechanical properties for stem cell fate
• Engineering artificial niche useful for bone marrow regeneration
• Developing technologies for bone and adipose tissue regeneration

Substrate mechanical properties, in addition to biochemical signals, have been shown to modulate cell phenotype. In this study, we inspected the effects of substrate stiffness on human mesenchymal stem cells (hMSCs) derived from adult human bone marrow differentiation into adipogenic and osteogenic cells. A chemically modified extracellular matrix derived and highly biocompatible hydrogel, based on thiol functionalized hyaluronic acid (HA-SH) and thiol functionalized recombinant human gelatin (Gtn-SH), which can be crosslinked by poly (ethylene glycol) tetra-acrylate (PEGTA), was used as a model system. The stiffness of the hydrogel was controlled by adjusting the crosslinking density. Human bone marrow MSCs were cultured on the hydrogels with different stiffness under adipogenic and osteogenic conditions. Oil Red O staining and F-actin staining were applied to assess the change of cell morphologies under adipogenic and osteogenic differentiation, respectively. Gene expression of cells was determined with reverse transcription polymerase chain reaction (RT-PCR) as a function of hydrogel stiffness. Results support the hypothesis that adipogenic and osteogenic differentiation of hMSCs are inclined to occur on substrate with stiffness similar to their in vivo microenvironments.