Hyaluronan induces a mitochondrial functional switch in fast-proliferating human mesenchymal stem cells.

Stem cells exhibit an ability to undergo continuous proliferation and differentiate into diverse cell types that makes them a powerful tool in clinic applications, thus underscoring the importance of studying the biological mechanisms responsible for self-renewal. Unfortunately,during long-term cultivation, stem cells may spontaneously lose their proliferation and differentiation potential. Hyaluronan is a nonsulfated glycosaminoglycan component of the extracellular matrix that consists of repeating disaccharides of glucuronic acid and N-acetylglucosamine. Its viscous physical property enables it to function in tissue lubrication and homeostasis and coregulate cellular adhesion, migration, proliferation, and differentiation. Hyaluronan is a key component of the stem cell niche, as demonstrated by its abundance in stem cell surroundings. We have previously demonstrated that hyaluronan supplementation in vitro extends the proliferation and differentiation potential of mesenchymal stem cells (1). Murineadipose derived mesenchymal stem cells cultured in coated hyaluronan (CHA) or medium supplemented hyaluronan (SHA) exhibit enhanced osteogenic potential and a reduced senescent population compared to the control (2).Similarly, culture of PDMSCs in CHA resulted in a delay in differentiation induction with an increased percentage of cells positive for MSC and pluripotent markers CD105,CD90, OCT-3/4, NANOG, and SSEA-4 (3). When PDMSCs were pretreated for a long period in CHA and then transferred onto normal tissue culture surface, enhanced osteogenic and chondrogenic potential was observed compared with the nontreatment group (1). These results suggest that hyaluronan-coated surfaces induce PMDSCs into a resting/quiescent state that preserved their stemness properties. Other recent reports have confirmed the ability of hyaluronan to promote adipogenic and chondrogenic differentiation and induce senescence delay (4). Previous studies have demonstrated a crucial function of hyaluronan on stem cell metabolism (5, 6). Mitochondria play a crucial role in the maintenance of self-renewal and differentiation of stem cells (7), and their function is improved by hyaluronan (8). We have recently reported for the first time that hyaluronan-coated surfaces reduced stem cell proliferation and upregulated mitochondrial biogenesis, which favored efficient mitochondrial function (3). The regulatory effect on stem cell proliferation depends on hyaluronan molecular weight, the concentration used, cell surface receptor signaling, and stem cell types (9, 10). Different hyaluronan supplementation methods (coated vs. medium supplemented) may cause distinct metabolic proliferative behaviors in stem cells. Hyaluronan supplementation in minute amounts on the culture medium induced an increase in proliferation in murine adipose-derived mesenchymal stem cells (mADSC) (2). Other reports have experimentally demonstrated the acceleration of stem cell proliferation by hyaluronan (10, 11). However, whether hyaluronan supplemented in the medium exerts changes in mitochondrial function to increase the cell proliferation rate remains unknown. In this study, we aimed to examine the effects that medium supplemented hyaluronan versus coated hyaluronan exert on mitochondrial function during hyaluronan-induced changes in stem cell proliferation. Understanding the influence of a biomaterial supplementation method in stem cells is pivotal during cell therapy, as it may affect its tissue regeneration mechanism