Abstract. The elucidation of the underlying molecular mechanisms regulating the osteogenic differentiation of bone marrow-derived mesenchymal stem cells (BMSCs) is of great importance in improving the treatment of bone-associated diseases. MicroRNAs (miRNAs) have been proven to regulate the osteogenic differentiation of BMSCs. The present study investigated the role of miR-217 in the osteogenic differentiation of rat BMSCs. It was observed that miR-217 expression levels were downregulated during the process of osteogenic differentiation. Subsequently, a dual-luciferase reporter gene assay demonstrated that miR-217 targets a putative binding site in the 3'-untranslated region of the runt related transcription factor 2 (Runx2) gene, which is a key transcription factor for osteogenesis. It was then demonstrated that overexpression of miR-217 attenuated the osteogenesis of BMSCs and downregulated the expression of Runx2, whereas inhibition of miR-217 promoted osteoblastic differentiation and upregulated Runx2 expression. Furthermore, the extracellular signal-regulated kinase (ERK) and p38 mitogen-activated protein kinase (p38 MAPK) signaling pathways were investigated during osteogenic induction, and the data indicated that miR-217 may exert a negative effect on the osteogenic differentiation of BMSCs through alteration of ERK and p38 MAPK phosphorylation. The present study therefore concluded that miR-217 functions as a negative regulator of BMSC osteogenic differentiation via the inhibition of Runx2 expression, and the underlying molecular mechanisms may partially be attributed to mediation by the ERK and p38 MAPK signaling pathways.

ObjectiveThis review aimed to summarize recent progress on syndromic dentin defects, promoting a better understanding of systemic diseases with dentin malformations, the molecules involved, and related mechanisms.Subjects and MethodsReferences on genetic diseases with dentin malformations were obtained from various sources, including PubMed, OMIM, NCBI, and other websites. The clinical phenotypes and genetic backgrounds of these diseases were then summarized, analyzed, and compared.ResultsOver 10 systemic diseases, including osteogenesis imperfecta, hypophosphatemic rickets, vitamin D‐dependent rickets, familial tumoral calcinosis, Ehlers‐Danlos syndrome, Schimke immuno‐osseous dysplasia, hypophosphatasia, Elsahy‐Waters syndrome, Singleton‐Merten syndrome, odontochondrodysplasia, and microcephalic osteodysplastic primordial dwarfism type II were examined. Most of these are bone disorders, and their pathogenic genes may regulate both dentin and bone development, involving extracellular matrix, cell differentiation, and metabolism of calcium, phosphorus, and vitamin D. The phenotypes of these syndromic dentin defects various with the involved genes, part of them are similar to dentinogenesis imperfecta or dentin dysplasia, while others only present one or two types of dentin abnormalities such as discoloration, irregular enlarged or obliterated pulp and canal, or root malformation.ConclusionSome specific dentin defects associated with systemic diseases may serve as important phenotypes for dentists to diagnose. Furthermore, mechanistic studies on syndromic dentin defects may provide valuable insights into isolated dentin defects and general dentin development or mineralization.

Osteoporosis (OP) characterizes a decrease in bone density and bone mass which leads to brittle fractures and serious damages to individuals. In recent years, various researches have proved that miRNAs act pivotally in the onset of bone-related diseases. In our research, we probed into the impact of miR-181a-5P on viability, differentiation, as well as apoptosis of human bone marrow mesenchymal stem cells (hBMSCs). Our study reported that overexpressing miR-181a-5p considerably reduced the cell growth, whereas the miR-181a-5p inhibition showed opposite results. Furthermore, the hBMSCs apoptosis percentage was visually elevated or minimized after overexpressing or silencing miR-181a-5p, respectively. Our data also indicated that miR-181a-5p overexpression significantly inhibited ALP activity, and level of OPN, Runx2 and OCN at mRNA and protein level, whereas miR-181a-5p inhibition presented opposite results. In addition, based on luciferase reporter assay, sirtuin 1 (Sirt1) was confirmed as the target of miR-181a-5p in hBMSCs. Finally, Sirt1 overexpression significantly inhibited the impact of miR-181a-5p mimic on apoptosis and inhibited differentiation, while silencing Sirt1 eliminated the inhibitory effects of miR-181a-5p on apoptosis and promoted differentiation via PI3K/AKT pathway. In conclusion, this work revealed that miR-181a-5p could regulate hBMSCs apoptosis as well as differentiation via regulating Sirt1/PI3K/AKT signaling pathway.

Dysfunction of pancreatic -cells is a fundamental feature in the pathogenesis of type 2 diabetes. As insulin receptor signaling occurs via protein tyrosine kinase (PTK), we investigated the role of PTK activity in the etiology of -cell dysfunction by inhibiting PTK activity in primary cultured mouse pancreatic -cells and oscillations. Semiquantitative PCR analysis revealed decreased expression of K ATP and L-type Ca 2+ channel mRNA in genistein-treated islets. PTK inhibition also significantly reduced the rapid component of secretory vesicle exocytosis, as indicated by membrane capacitance measurements, and this is likely to be due to the reduced Ca 2+ current amplitude in these cells. These results illustrate that compromised PTK activity contributes to pancreatic -cell dysfunction and may be involved in the etiology of type 2 diabetes.

In an effort to bolster our understanding of regulation of bone formation in the context of osteoporosis, we screened out differentially expressed genes in osteoporosis patients with high and low bone mineral density by bioinformatics analysis. PIK3R1 is increasingly being nominated as a pivotal mediator in the differentiation of osteoblasts and osteoclasts that is closely related to bone formation. However, the specific mechanisms underlying the way that PIK3R1 affects bone metabolism are not fully elucidated. We intended to examine the potential mechanism by which PIK3R1 regulates osteoblast differentiation. Enrichment analysis was therefore carried out for differentially expressed genes. We noted that the estrogen signaling pathway, TNF signaling pathway, and osteoclast differentiation were markedly associated with ossification, and they displayed enrichment in PIK3R1. Based on western blot, qRT-PCR, and differentiation analysis in vitro, we found that upregulation of PIK3R1 enhanced osteoblastic differentiation, as evidenced by increased levels of investigated osteoblast-related genes as well as activities of ALP and ARS, while it notably decreased levels of investigated osteoclast-related genes. On the contrary, downregulation of PIK3R1 decreased levels of osteoblast-related genes and increased levels of osteoclast-related genes. Besides, in vitro experiments revealed that PIK3R1 facilitated proliferation and repressed apoptosis of osteoblasts but had an opposite impact on osteoclasts. In summary, PIK3R1 exhibits an osteoprotective effect via regulating osteoblast differentiation, which can be represented as a promising therapeutic target for osteoporosis.