Retinoic acid regulates commitment of undifferentiated mesenchymal stem cells into osteoblasts and adipocytes.

Evidence indicates that the balance between osteoblastogenesis and adipogenesis of mesenchymal stem cells (MSCs) is regulated by several hormones, growth factors, and their downstream signaling cascades. Previous studies suggest that retinoic acid (RA) plays a role in osteoblastogenesis and adipogenesis. However, it is unknown whether RA regulates commitment of MSCs into osteoblasts and adipocytes. In this study, we investigated the role of RA in differentiation of MSCs using the C3H10T1/2 cell line. RA stimulated activity and expression of alkaline phosphatase (ALP) and upregulated activity of the ALP gene promoter. The effects of RA were further enhanced by bone morphogenetic protein 2 (BMP2) and resultant Smad signaling. Furthermore, overexpression of Runx2 and Msx2, critical transcription factors for bone formation and BMP2-dependent osteoblastogenesis, enhanced RA-dependent ALP activity. In view of these findings, RA likely stimulates osteoblast differentiation through the BMP2-Smad-Runx2/Msx2 pathway. In contrast, RA markedly inhibited BMP2-induced adipocyte differentiation, suppressing expression of peroxisome proliferator-activated receptor-γ (PPARγ), CCAAT/enhancer-binding protein (C/EBP)α and C/EBPδ, and inhibiting adipogenic function of C/EBPß, C/EBPδ, and PPARγ. In conclusion, our data suggest that RA regulates commitment of MSCs into osteoblasts and adipocytes by controlling transcriptional regulators.

[Candida adherence and biofilm formation on oral surfaces].

Candida albicans is the most common fungal opportunistic pathogen in humans. The AIDS epidemic, improved life-sustaining therapy, and aggressive anticancer therapy have contributed to a rise in the number of severely immunocompromised patients. This has led to an increase in oral and systemic fungal infection. Several factors, such as adherence, persistence, dimorphism, germ tube formation, and/or contact sensing, phenotypic switching, interference with the host defense system, synergism with bacteria, and the production of hydrolases or other metabolites, have been proposed to be virulence factors of this fungus. Among these virulence factors, adherence and persistence are thought to be the most important, since the colonization and subsequent biofilm formation of oral surfaces may serve as a reservoir for disseminated infections, such as aspiration pneumonia and gastrointestinal infection. In the review, we summarized the factors involved in the Candida albicans biofilm formation.