Mechanosensitive protein polycystin-1 promotes periosteal stem/progenitor cells osteochondral differentiation in fracture healing.

Background: Mechanical forces are indispensable for bone healing, disruption of which is recognized as a contributing cause to nonunion or delayed union. However, the underlying mechanism of mechanical regulation of fracture healing is elusive. Methods: We used the lineage-tracing mouse model, conditional knockout depletion mouse model, hindlimb unloading model and single-cell RNA sequencing to analyze the crucial roles of mechanosensitive protein polycystin-1 (PC1, Pkd1) promotes periosteal stem/progenitor cells (PSPCs) osteochondral differentiation in fracture healing. Results: Our results showed that cathepsin (Ctsk)-positive PSPCs are fracture-responsive and mechanosensitive and can differentiate into osteoblasts and chondrocytes during fracture repair. We found that polycystin-1 declines markedly in PSPCs with mechanical unloading while increasing in response to mechanical stimulus. Mice with conditional depletion of Pkd1 in Ctsk+ PSPCs show impaired osteochondrogenesis, reduced cortical bone formation, delayed fracture healing, and diminished responsiveness to mechanical unloading. Mechanistically, PC1 facilitates nuclear translocation of transcriptional coactivator TAZ via PC1 C-terminal tail cleavage, enhancing osteochondral differentiation potential of PSPCs. Pharmacological intervention of the PC1-TAZ axis and promotion of TAZ nuclear translocation using Zinc01442821 enhances fracture healing and alleviates delayed union or nonunion induced by mechanical unloading. Conclusion: Our study reveals that Ctsk+ PSPCs within the callus can sense mechanical forces through the PC1-TAZ axis, targeting which represents great therapeutic potential for delayed fracture union or nonunion.

Exosomes derived from mesenchymal stem cells in diabetes and diabetic complications.

Diabetes, a group of metabolic disorders, constitutes an important global health problem. Diabetes and its complications place a heavy financial strain on both patients and the global healthcare establishment. The lack of effective treatments contributes to this pessimistic situation and negative outlook. Exosomes released from mesenchymal stromal cells (MSCs) have emerged as the most likely new breakthrough and advancement in treating of diabetes and diabetes-associated complication due to its capacity of intercellular communication, modulating the local microenvironment, and regulating cellular processes. In the present review, we briefly outlined the properties of MSCs-derived exosomes, provided a thorough summary of their biological functions and potential uses in diabetes and its related complications.

Age-related secretion of grancalcin by macrophages induces skeletal stem/progenitor cell senescence during fracture healing.

Skeletal stem/progenitor cell (SSPC) senescence is a major cause of decreased bone regenerative potential with aging, but the causes of SSPC senescence remain unclear. In this study, we revealed that macrophages in calluses secrete prosenescent factors, including grancalcin (GCA), during aging, which triggers SSPC senescence and impairs fracture healing. Local injection of human rGCA in young mice induced SSPC senescence and delayed fracture repair. Genetic deletion of Gca in monocytes/macrophages was sufficient to rejuvenate fracture repair in aged mice and alleviate SSPC senescence. Mechanistically, GCA binds to the plexin-B2 receptor and activates Arg2-mediated mitochondrial dysfunction, resulting in cellular senescence. Depletion of Plxnb2 in SSPCs impaired fracture healing. Administration of GCA-neutralizing antibody enhanced fracture healing in aged mice. Thus, our study revealed that senescent macrophages within calluses secrete GCA to trigger SSPC secondary senescence, and GCA neutralization represents a promising therapy for nonunion or delayed union in elderly individuals.

miR-188-3p targets skeletal endothelium coupling of angiogenesis and osteogenesis during ageing.

A specific bone capillary subtype, namely type H vessels, with high expression of CD31 and endomucin, was shown to couple angiogenesis and osteogenesis recently. The number of type H vessels in bone tissue declines with age, and the underlying mechanism for this reduction is unclear. Here, we report that microRNA-188-3p (miR-188-3p) involves this process. miRNA-188-3p expression is upregulated in skeletal endothelium and negatively regulates the formation of type H vessels during ageing. Mice with depletion of miR-188 showed an alleviated age-related decline in type H vessels. In contrast, endothelial-specific overexpression of miR-188-3p reduced the number of type H vessels, leading to decreased bone mass and delayed bone regeneration. Mechanistically, we found that miR-188 inhibits type H vessel formation by directly targeting integrin ß3 in endothelial cells. Our findings indicate that miR-188-3p is a key regulator of type H vessel formation and may be a potential therapeutic target for preventing bone loss and accelerating bone regeneration.

miR-134 inhibits osteosarcoma cell invasion and metastasis through targeting MMP1 and MMP3 in vitro and in vivo.

miR-134 has been shown to be associated with angiogenesis and the progression of osteosarcoma. This study further assessed the effects of miR-134 expression on osteosarcoma cell migration, invasion, and metastasis in vitro and in a nude mouse xenograft model, exploring the underlying molecular events. Luciferase reporter assays revealed that miR-134 directly targets the 3'-UTRs of MMP1 and MMP3 to reduce their expression in osteosarcoma cells. In conclusion, overexpression of miR-134 suppresses osteosarcoma cell invasion and metastasis through the inhibition of MMP1 and MMP3 expression. We propose miR-134 as an attractive novel therapeutic target for the treatment of osteosarcoma.

5-HTT, BMPR2, EDN1, ENG, KCNA5 gene polymorphisms and susceptibility to pulmonary arterial hypertension: A meta-analysis.

BACKGROUND: The influence of 5-HTT, BMPR2, EDN1, ENG, KCNA5 genes polymorphisms on susceptibility of pulmonary arterial hypertension remains uncertain. This meta-analysis is conducted for further study. METHODS: We conducted a literature search on PubMed and ISI web of science databases for searching relevant articles until November 2017. Pooled odds ratios (ORs) with 95% confidence intervals (CIs) were calculated. A total of 17 articles with 2631 PAH subjects and 5139 controls were included in the final meta-analysis. Statistical software Stata13.0 was used for data-analysis. RESULTS: A significant relationship was found between the 5-HTT L/S polymorphism and PAH in all the genetic models [LL vs. SS: OR = 1.60, 95% CI, 1.11-2.32; LS vs. SS: OR = 1.55, 95% CI, 1.10-2.21; (LS + LL) vs. SS: OR = 1.56, 95% CI, 1.13-2.17; L vs. S: OR = 1.32, 95% CI, 1.08-1.62]. There were also associations of the SERT L/S polymorphism with IPAH and PAH in COPD [IPAH L/S: OR = 1.26, 95% CI, 1.01-1.57; PAH in COPD L/S: OR = 1.42, 95% CI, 1.04-1.94]. In addition, the results showed a statistically significant association between EDN1 rs5370 polymorphism and the risk of PAH in all the genetic models [TT vs. GG: OR = 3.32, 95% CI, 1.30-8.51; TG vs. GG: OR = 2.68, 95% CI, 1.54-4.66; (TG + TT) vs. GG: OR = 2.82, 95% CI, 1.69-4.71; T vs. G: OR = 2.43, 95% CI, 1.60-3.68]. However, the significant association was not found between BMPR2 rs1061157, KCNA5 rs10744676, ENG rs3739817 polymorphisms and the risk of PAH (all p > 0.05). CONCLUSIONS: 5-HTT L/S polymorphism and END1 rs5370 polymorphism were correlated with significantly increased risk of PAH. Moreover, L allele in 5-HTT gene increased susceptibility to IPAH and PAH in COPD.