Spontaneous Spheroids of hUC-MSCs Regulate Osteogenic Differentiation for Enhancing Osteogenesis

Stem cells play a critical role in the regeneration process by proliferating and differentiating to form new bone tissue. However, stem cells tend to lose their stemness and pluripotency during <i>in vitro</i> expansion, resulting in reduced bone regeneration capacity after osteogenic induction. Our aim is to enhance the osteogenic impact of human umbilical cord-derived mesenchymal stromal cells (hUC-MSCs) through spontaneous spheroid <i>in vitro</i>. The pluripotency and osteogenesis-related genes up-regulated in hUC-MSCs can be enhanced in spontaneous spheroids <i>in vitro</i>. For <i>in vivo</i> testing, spontaneous spheroids were transplanted into mice using beta-tricalcium phosphate as a scaffold. Transplant samples were stained using hematoxylin and eosin (HE), immunohistochemistry, and TRAP staining. The samples showed new bone formation, upregulated SP7 and OCN expression, and more vigorous bone metabolism in the Sph-OI group than the other groups. However, new bone formation was mainly immature bone. Overall, our findings demonstrate that hUC-MSC spheroids possess remarkable pluripotency, with the spontaneous spheroids formed following osteogenic induction exhibiting enhanced osteogenic differentiation potential and bone regeneration capacity. However, optimizing the osteogenic differentiation process and elucidating the underlying mechanisms of bone regeneration are critical scientific issues that urgently need to be addressed to enable its application in bone regeneration.