A C-Met chemical inhibitor promotes fracture healing through interacting with osteogenic differentiation via the mTORC1 pathway

Rapamycin does not alter bone microarchitecture or material properties quality in young-adult and aged female C57BL/6 mice

Advancing age is the strongest risk factor for osteoporosis and skeletal fragility. Rapamycin is an FDA-approved immunosuppressant that inhibits the mechanistic target of rapamycin (mTOR) complex, extends lifespan, and protects against aging-related diseases in multiple species; however, the impact of rapamycin on skeletal tissue is incompletely understood. We evaluated the effects of a short-term, low-dosage, interval rapamycin treatment on bone microarchitecture and strength in young-adult (3 mo old) and aged female (20 mo old) C57BL/6 mice. Rapamycin (2 mg/kg body mass) was administered via intraperitoneal injection 1×/5 d for a duration of 8 wk; this treatment regimen has been shown to induce geroprotective effects while minimizing the side effects associated with higher rapamycin dosages and/or more frequent or prolonged delivery schedules. Aged femurs exhibited lower cancellous bone mineral density, volume, trabecular connectivity density and number, higher trabecular thickness and spacing, and lower cortical thickness compared to young-adult mice. Rapamycin had no impact on assessed microCT parameters. Flexural testing of the femur revealed that both yield strength and ultimate strength were lower in aged mice compared to young-adult mice. There were no effects of rapamycin on these or other measures of bone biomechanics. Age, but not rapamycin, altered local and global measures of bone turnover. These data demonstrate that short-term, low-dosage interval rapamycin treatment does not negatively or positively impact the skeleton of young-adult and aged mice.

Signature of circulating small non-coding RNAs during early fracture healing in mice

Fracture healing is a complex process with multiple overlapping metabolic and differentiation phases. Small non-coding RNAs are involved in the regulation of fracture healing and their presence in circulation is under current interest due to their obvious value as potential biomarkers. Circulating microRNAs (miRNAs) have been characterized to some extent but the current knowledge on tRNA-derived small RNA fragments (tsRNAs) is relatively scarce, especially in circulation.

In this study, the spectrum of circulating miRNAs and tsRNAs was analysed by next generation sequencing to show their differential expression during fracture healing in vivo. Analysed tsRNA fragments included stress-induced translation interfering tRNA fragments (tiRNAs or tRNA halves) and internal tRNA fragments (i-tRF), within the size range of 28–36 bp. To unveil the expression of these non-coding RNAs, genome-wide analysis was performed on two months old C57BL/6 mice on days 1, 5, 7, 10, and 14 (D1, D5, D7, D10, and D14) after a closed tibial fracture.

Valine isoacceptor tRNA-derived Val-AAC 5′end and Val-CAC 5′end fragments were the major types of 5′end tiRNAs in circulation, comprising about 65 % of the total counts. Their expression was not affected by fracture. After a fracture, the levels of two 5′end tiRNAs Lys-TTT 5′ and Lys-CTT 5′ were decreased and His-GTG 5′ was increased through D1-D14. The level of miR-451a was decreased on the first post-fracture day (D1), whereas miR-328-3p, miR-133a-3p, miR-375-3p, miR-423-5p, and miR-150-5p were increased post-fracture. These data provide evidence on how fracture healing could provoke systemic metabolic effects and further pinpoint the potential of small non-coding RNAs as biomarkers for tissue regeneration.

The role of Bacillus acidophilus in osteoporosis and its roles in proliferation and differentiation

Background

Osteoporosis is one of the most closely related diseases associated with the elderly. In recent years, the studies found that gut microbiota can cause osteoporosis. We evaluated the role of Bacillus acidophilus in osteoporosis and its roles in proliferation and differentiation.

Methods

We selected 5 healthy people and 10 osteoporosis patients and analyzed their level of 25‐hydroxyvitamin D and procollagen type I N‐terminal peptide (PINP), the characteristic of gut microbiota. The effect of lactobacillus acidophilus and Lactobacillus rhamnosus supernatant and butanoic acids on proliferation, differentiation, and maturity of osteoblasts MC3T3‐E1 and osteoclasts RAW 264.7 cells and the activity of alkaline phosphatase, concentration of osteocalcin, and the expression of RUNX2, RANK, NFATc1, cathepsin K, DC‐STAMP, OSCAR, WNT2, and CTNNB1 were measured in the above cell lines.

Results

The diversity of gut microbiota in osteoporosis patients is decreased and imbalanced with lower abundance of lactobacillus and butyric acid bacteria; meanwhile, 25‐hydroxyvitamin D and PINP of osteoporosis patient were significantly lower than the normal group. The proliferation, differentiation, and maturity of MC3T3‐E1 cells were stimulated; the activity of alkaline phosphatase, concentration of osteocalcin, and the expression of RUNX2, NFATc1, cathepsin K, DC‐STAMP, OSCAR, WNT2, and CTNNB1 were improved by supernatant of lactobacillus acidophilus, Lactobacillus rhamnosus and butanoic acids; however, the proliferation, differentiation, maturity, and the expression of RANK, NFATc1, cathepsin K, DC‐STAMP, OSCAR, WNT2, and CTNNB1 in RAW 264.7 cells were suppressed.

Conclusions

The lactobacillus acidophilus and Lactobacillus rhamnosus supernatant could stimulate the proliferation, differentiation, and maturation of osteoblasts; the production of butyric acid may be the potential mechanism.