Hydrogel microenvironment contributes to chemical-induced differentiation of mesenchymal stem cells: single-cell infrared microspectroscopy characterization.

Stem cell microenvironment plays vital roles in directing cell proliferation and differentiation. Due to the tiny biochemical changes in the early stage of stem cell development, technical challenges to characterize the potential effects of environmental signals remain. In this work, we have introduced synchrotron radiation-based Fourier transform infrared microspectroscopy to evaluate the synergistic effects of physical and chemical factors on stem cell differentiation at the single-cell level. By using principal component analysis and cell-cell Euclidean distance calculation, the phenotypic heterogeneity changes during stem cell osteogenesis induced by lithium chloride or Wnt5a protein loaded in the polyvinyl alcohol (PVA) hydrogel were characterized in detail. The results demonstrated that PVA hydrogel could lead to the distinct effects between low-concentration lithium and wnt5a on human mesenchymal stem cells, suggesting a vital role of niche signals in Wnt pathway. These findings highlight the importance of microenvironment to the chemical-induced effects on stem cell differentiation and also provide a label-free, noninvasive method to sensitively identify the niche function in stem cell biology.