Biological activities of cells such as survival and differentiation processes are mainly maintained by a specific extracellular matrix (ECM). Hydrogels have recently been employed successfully in tissue engineering applications. In particular, scaffolds made of gelatin methacrylate-based hydrogels (GelMA) showed great potential due to their biocompatibility, biofunctionality, and low mechanical strength. The development of a hydrogel having tunable and appropriate mechanical properties as well as chemical and biological cues was the aim of this work. A synthetic and biological hybrid hydrogel was developed to mimic the biological and mechanical properties of native ECM. A combination of gelatin methacrylate and acrylamide (GelMA-AAm)-based hydrogels was studied, and it showed tunable mechanical properties upon changing the polymer concentrations. Different GelMA-AAm samples were prepared and studied by varying the concentrations of GelMA and AAm (AAm2.5% + GelMA3%, AAm5% + GelMA3%, and AAm5% + GelMA5%). The swelling behavior, biodegradability, physicochemical and mechanical properties of GelMA-AAm were also characterized. The results showed a variation of swelling capability and a tunable elasticity ranging from 4.03 to 24.98 kPa depending on polymer concentrations. Moreover, the podocyte cell morphology, cytoskeleton reorganization and differentiation were evaluated as a function of GelMA-AAm mechanical properties. We concluded that the AAm2.5% + GelMA3% hydrogel sample having an elasticity of 4.03 kPa can mimic the native kidney glomerular basement membrane (GBM) elasticity and allow podocyte cell attachment without the functionalization of the gel surface with adhesion proteins compared to synthetic hydrogels (PAAm). This work will further enhance the knowledge of the behavior of podocyte cells to understand their biological properties in both healthy and diseased states.

Photobiomodulation (PBM) has been shown to improve cell proliferation and cell migration. Many cell types have been 
investigated, with most studies using deep penetrating red light irradiation. Considering the interest of surface biostimulation 
of oral mesenchymal cells after surgical wound, the present study aimed to assess green light irradiation effects on Dental Pulp 
Stem Cells’ (DPSC) proliferation and migration. To understand the mechanisms underlying these effects, we investigated 
cytoskeleton organization and subsequent cell shape and stiffness. 
A 532-nm wavelength Nd:YAG laser (30 mW) was applied 
between 30 and 600 s on DPSC in vitro. Cell proliferation was analyzed at 24, 48, and 72 h after irradiation, by cell counting and enzymatic activity quantification (paranitrophenylphosphate phosphatase (pNPP) test). A wound healing assay was used to study 
cell migration after irradiation. Effects of PBM on cytoskeleton organization and cell shape were assessed by actin filaments 
staining. Elasticity changes after irradiation were quantified in terms of Young’s modulus measured using Atomic Force 
Microscopy (AFM) force spectroscopy. Green light significantly improved DPSC proliferation with a maximal effect obtained after 300-s irradiation (energy fluence 5 J/cm2). This irradiation had a significant impact on cell migration, improving wound 
healing after 24 h. These results were concomitant with a decrease of cells’ Young’s modulus after irradiation. This cell softening 
was explained by actin cytoskeleton reorganization, with diminution of cell circularity and more abundant pseudopodia. This 
study highlights the interest of green laser PMB for the proliferation and migration of mesenchymal stem cells, with encouraging 
results for clinical application, especially for surgical wound healing procedures.