Over the past few years, mesenchymal stem (or stromal) cells (MSCs) have garnered enormous interest due to their therapeutic value especially for their multilineage differentiation potential leading to regenerative medicine applications. MSCs undergo physiological changes upon in vitro expansion resulting in expression of different receptors, thereby inducing high variabilities in therapeutic efficacy. Therefore, understanding the biochemical cues that influence the native local signals on differentiation or proliferation of these cells is very important. There have been several reports that in vitro culture of MSCs in low oxygen gradient (or hypoxic conditions) upregulates the stemness markers and promotes cell proliferation in an undifferentiated state, as hypoxia mimics the conditions the progenitor cells experience within the tissue. However, different studies report different oxygen gradients and culture conditions causing ambiguity in their interpretation of the results. In this progress report, it is aimed to summarize recent studies in the field with specific focus on conflicting results reported during the application of hypoxic conditions for improving the proliferation or differentiation of MSCs. Further, it is tried to decipher the factors that can affect characteristics of MSC under hypoxia and suggest a few techniques that could be combined with hypoxic cell culture to better recapitulate the MSC tissue niche.

Circulating nucleic acids,s uch as short interfering RNA( siRNA), regulate many biological processes;h owever, the mechanism by whichthese molecules enter the cell is poorly understood. The role of extracellular-matrix-derived polymers in binding siRNAs and trafficking them across the plasma membrane is reported. Thermal melting, dynamic light scattering, scanning electron microscopy, and computational analysis indicate that hyaluronic acid can stabilizesiRNAvia hydrogen bonding and Vand er Waals interactions.T his stabilization facilitated HA size-and concentration-dependent gene silencing in aCD44-positive human osteosarcoma cell line (MG-63) and in human mesenchymal stromal cells (hMSCs). This native HA-based siRNAtransfection represents the first report on an anionic,n on-viral delivery method that resulted in approximately 60 %gene knockdowninboth cell types tested, which correlated with ar eduction in translation levels.

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We present here a new insight into the chemical reactivity and bioactivity of dopamine (DA) and gallic acid (GA) and their hyaluronic acid (HA) conjugates. Our data suggest that HA-GA...