Comparison of parathyroid hormone and strontium ranelate in combination with whole-body vibration in a rat model of osteoporosis

Strontium ranelate enriched Ruminococcus albus in the gut microbiome of Sprague-Dawley rats with postmenopausal osteoporosis

BACKGROUND

Gut microbiome is critical to our human health and is related to postmenopausal osteoporosis (PMO). Strontium ranelate (SrR) is an anti-osteoporosis oral drug that can promote osteoblast formation and inhibit osteoclast formation. However, the effect of SrR on gut microbiome has been rarely studied. Therefore, we investigated the effect of oral SrR on gut microbiome and metabolic profiles.

RESULTS

In this study, we used ovariectomized (OVX) Sprague-Dawley rats to construct a PMO model and applied oral SrR for 6 weeks. The relative abundance of intestinal microbiome was investigated by 16S rRNA metagenomic sequencing. Ultra-high-performance liquid chromatography-mass spectrometry (UHPLC-MS) was used to analyze changes in metabolites of intestinal contents. Results demonstrated that 6-week oral SrR alleviated osteoporosis and significantly changed the composition of the gut microbiome and metabolic profiles of OVX rats. Ruminococcus, Akkermansia and Oscillospira were significantly enriched in the gut of OVX rats after 6-week oral SrR. Especially, the species R. albus showed the greatest importance by a random forest classifier between OVX and OVX_Sr group. The enrichment of R. albus in the gut was positively correlated with bone mineral density and the accumulation of lycopene and glutaric acid, which also significantly elevated after oral SrR.

CONCLUSIONS

We discovered that oral SrR can improve bone health while stimulate the accumulation of gut microbe R. albus and metabolites (lycopene and glutaric acid). The results suggested possible connections between oral SrR and the gut-bone axis, which may provide new insight into the treatment/prevention of osteoporosis.

Preventive effect of teriparatide on medication-related osteonecrosis of the jaw in rats

This study aimed to investigate the preventive effect of teriparatide (TPD) administration on medication-related osteonecrosis of the jaw (MRONJ) before tooth extraction due to periodontal lesions in bilaterally ovariectomized female rats treated with zoledronic acid. Thirty skeletally mature Sprague-Dawley rats were randomly divided into three groups: control (CONT, n = 10), zoledronic acid (ZA, n = 10), and zoledronic acid and teriparatide (ZA-TPD, n = 10). The rats were sacrificed 8 weeks after tooth extraction. Micro-computed tomography analysis of the tibia showed that bone mineral density was highest in the CONT, followed by that in the ZA and ZA-TPD groups (CONT/ZA, p = 0.009; CONT/ZA-TPD, p < 0.001; ZA/ZA-TPD, p < 0.001). In the trabecular bone analysis of the extraction site, significant differences in specific bone surface (CONT/ZA, p = 0.010; CONT/ZA-TPD, p = 0.007; ZA/ZA-TPD, p = 0.002) and trabecular thickness (CONT/ZA-TPD, p = 0.002; ZA/ZA-TPD, p = 0.002) were observed. Histological analyses of the extraction sites revealed characteristic MRONJ lesions in the ZA group. Osteonecrosis, inflammatory cells, and sequestrum were less frequently observed in the ZA-TPD group than in the ZA group. In conclusion, TPD administration before tooth extraction helped reduce the occurrence of MRONJ in rats treated with zoledronic acid, confirming its preventative effects.

Effect of Mechanical Stimuli and Zoledronic Acid on the Femoral Bone Morphology in Rats with Obesity and Limited Mobility

Our study aimed to compare the impact of zoledronic acid and whole-body vibration (WBV) as a non-pharmacological method of treatment for early obesity/immobility-related osteoporosis in male rat models. In total, 36 male Wistar rats were assigned to the following groups: obese control with immobility (Control, n = 12) and two experimental groups (n = 12 each), including obese and immobile rats subjected to whole-body vibration with an acceleration level of 3 m/s² g (obesity and immobility + WBV) and obese and immobile rats that received an intramuscular injection of zoledronic acid at a dose of 0.025 mg/kg (obesity and immobility + ZOL). After the 8th and 16th week of treatment, n = 6 rats from each group were euthanized and isolated femora were subjected to a histological examination of bone, and analysis of the expression of osteoprotegerin (OPG) and the receptor activator of nuclear factor kappa-B ligand (RANKL) involved in bone turnover and the amount of thin collagen fibers (PSR stain). The obtained results showed that short-term vibrotherapy (up to 8 weeks) can lead to improvement in bone remodeling in rat models with obesity and limited mobility.

Effects of whole-body vibration at different periods on lumbar vertebrae in female rats

The current study aimed to investigate the effects of whole-body vibration (WBV) before and after ovariectomy on lumbar vertebrae, and to observe whether the positive effects of WBV before and after ovariectomy on lumbar vertebrae in rats could be maintained after vibration stopped. Three-month-old female rats were divided into four groups (n = 45/group): control (CON), ovariectomy (OVA), WBV before ovariectomy (WBV-BO), and WBV after ovariectomy (WBV-AO) groups. For 1-8 weeks, WBV-BO group was subjected to vertical WBV. At the 9th week, the rats in WBV-BO, WBV-AO, and OVA groups were ovariectomized. During 11-18 weeks, WBV-AO group was subjected to vibration. For 19-26 weeks, no intervention was done for rats. The lumbar vertebrae were examined by Micro-CT, compressive test, creep test, and microindentation test. At the 8th week, the displacement of the L1-L2 annulus fibrosus in WBV-BO group was 18% smaller compared with CON group (p<0.05). At the 18th week, the elastic modulus of the L5 vertebral body in WBV-BO and WBV-AO groups was 53% and 57% higher than that in CON group, respectively (p<0.05); the displacement of the L1-L2 annulus fibrosus in WBV-BO group was 25% smaller than those in the other groups (p<0.05). At the 26th week, there was no significant difference in the displacement of the L1-L2 annulus fibrosus between WBV-BO group and other groups (p>0.05); the elastic modulus of the L5 vertebral body had no significant difference between WBV-AO group and CON group (p>0.05). Our results demonstrated that WBV before ovariectomy effectively prevented disc degeneration with significant effects up to 8 weeks after ovariectomy. The vertebral mechanical properties could be significantly improved by WBV after ovariectomy, but the residual effect did not maintain after WBV stopped.

Enhanced Bone Formation in Osteoporotic Mice by a Novel Transplant Combined with Adipose-derived Stem Cells and Platelet-rich Fibrin Releasates

Osteoporotic fracture is the main complication of osteoporosis (OP) and accounts for millions of injuries annually. Local intervention by intra-marrow injection has been a good option for preventing osteoporotic bone loss when the osteoporotic femoral fracture has been treated. In this study, tail vein transplantations were examined to evaluate the cell-based therapeutic approach for treating OP with adipose-derived stem cells (ADSCs) and platelet-rich fibrin releasates (PRFr) in an ovariectomized (OVX) mice model. Thirty-six 12-wk-old female ICR mice were randomly divided into six groups: untreated control; sham-operated; OVX-control; OVX-ADSCs; OVX-PRFr; and OVX-ADSCs+PRFr. Starting 8 wk after ovariectomy, the OVX mice received tail vein injections once each week for four consecutive weeks, then were evaluated radiographically and histopathologically 8 wk after the first injection. We also assessed changes to bone trabeculae in the proximal tibial growth plate. In OVX mice treated with ADSCs or PRFr alone, or with a combination of ADSCs and PRFr, the trabecular bone mineral density (BMD), bone volume ratios (BV/TV), and numbers (Tb.N) in the proximal tibia areas were significantly higher than that in the OVX-control group. Significant differences between OVX-treated mice and OVX controls were found for trabecular separation, but not for trabecular thickness. These results indicate that ADSCs or PRFr treatment enhances bone microarchitecture in OP. The treatment of bone loss of OVX mice with ADSCs+PRFr induced greater bone consolidation with bone tissue production (P < 0.01) when compared to the others. Thus, we conclude that the transplantation of ADSCs combined with PRFr might provide an alternative strategy for the treatment of various bone disorders in OP with an unlimited source of cells and releasates.

Effect and timing of parathyroid hormone analog administration for preventing medication-related osteonecrosis of the jaws in a murine model

The aim of this study was to investigate the effect and timing of recombinant human parathyroid hormone analog (PTH) administration for preventing medication-related osteonecrosis of the jaws (MRONJ) using a murine model. After standardized MRONJ induction using zoledronic acid and dexamethasone injections, 48 female Sprague-Dawley rats were divided into four groups according to the timing of PTH administration before or after dental extraction. Rats were euthanized 3 weeks after dental extraction, followed by clinical and histologic analyses. No clinical improvements were observed in the preoperative and postoperative PTH groups, compared to controls (p = 0.638 and 0.496, respectively). However, on histological analysis, the number of empty lacunae reduced significantly, and the number of blood vessels increased in the preoperative PTH group (p = 0.004 and 0.002, respectively). The postoperative PTH group did not show significant differences for empty lacunae and blood vessels compared to controls (p = 0.075 and 0.194, respectively). The reduction in the empty lacunae and the increase in the blood vessels in the preoperative PTH group were significant compared to other groups, suggesting more viable bone tissue in this group. In perspective, preoperative PTH use may represent a better prophylactic regimen for preventing the occurrence of MRONJ after traumatic dental or surgical procedures, especially in patients with a history of long-term bisphosphonate administration or at high risk of developing MRONJ. However, the findings should be proven in further studies on other animals followed by clinical trials.

Does Physical Exercise Always Improve Bone Quality in Rats?

For decades, the osteogenic effect from different physical activities on bone in rodents remained uncertain. This literature review presents for the first time the effects on five exercise models (treadmill running, wheel running, swimming, resistance training and vibration modes) in three different experimental rat groups (males, females, osteopenic) on bone quality. The bone parameters presented are bone mineral density, micro-architectural and mechanical properties, and osteoblast/osteocyte and osteoclast parameters. This review shows that physical activities have a positive effect (65% of the results) on bone status, but we clearly observed a difference amongst the different protocols. Even if treadmill running is the most used protocol, the resistance training constitutes the first exercise model in term of osteogenic effects (87% of the whole results obtained on this model). The less osteogenic model is the vibration mode procedure (31%). It clearly appears that the gender plays a role on the bone response to swimming and wheel running exercises. Besides, we did not observe negative results in the osteopenic population with impact training, wheel running and vibration activities. Moreover, about osteoblast/osteocyte parameters, we conclude that high impact and resistance exercise (such jumps and tower climbing) seems to increase bone formation more than running or aerobic exercise. Among the different protocols, literature has shown that the treadmill running procedure mainly induces osteogenic effects on the viability of the osteocyte lineage in both males and females or ovariectomized rats; running in voluntary wheels contributes to a negative effect on bone metabolism in older male models; whole-body vertical vibration is not an osteogenic exercise in female and ovariectomized rats; whereas swimming provides controversial results in female models. For osteoclast parameters only, running in a voluntary wheel for old males, the treadmill running program at high intensity in ovariectomized rats, and the swimming program in a specific ovariectomy condition have detrimental consequences.

Mechanical Vibration Associated With Intermittent PTH Improves Bone Microarchitecture in Ovariectomized Rats

INTRODUCTION

Intermittent 1-34 parathyroid hormone (iPTH) administration, a bone-forming treatment, is widely used as a therapy for severe osteoporosis. It can only be used for a maximum of 24 mo and must be followed by an antiresorptive drug to retain the new formed tissue. Mechanical load, in the form of low-intensity and high-frequency vibration, has received considerable attention due to its ability to prevent bone loss.

AIM

To investigate the ability of whole body mechanical vibration (MV) to potentiate the anabolic effects of iPTH and to inhibit bone resorption following discontinuation of iPTH treatment in estrogen-deficient rats.

METHODOLOGY

Fifty-four 6-month-old female Wistar rats were ovariectomized (OVX) or sham-operated. After 5 mo, they were divided into 7 groups: Sham - non-OVX; Control - OVX, vehicle for 60 d; MV - OVX, submitted to MV for 60 d; PTH60d - OVX, injected with iPTH for 60 d; PTH+MV - OVX, injected with iPTH combined with MV for 60 d; PTH30d - OVX, injected with iPTH for 30 d, and untreated for 30 d; PTH30d/MV30d - OVX, injected with iPTH for 30 d, followed by MV for 30 d. Bone mineral density (BMD) and body composition (lean mass and fat) were evaluated at OVX (T0), the beginning (T1), and at the end (T2) of treatments by dual X-ray absorptiometry (DXA). Femurs were processed for histomorphometry (bone volume - BV/TV and cortical thickness - Ct.Th) and tibias for biomechanical test.

RESULTS

Body composition and BMD were similar among the groups at T0. In T2, MV presented higher fat than other groups (except PTH60d) and PTH30d/MV30d showed greater lean mass than Control. At T1, Sham presented the highest BMD, but between T1 vs T2 there was an increase in all iPTH-treated groups. At T2, BMD was higher in PTH60d and PTH+MV than in the Control and MV groups. The highest BV/TV was observed in the PTH+MV group, followed by PTH60d. Cortical thickness was increased in PTH60d and PTH+MV compared to Sham. Vibration applied post-iPTH (PTH30d/MV30d) improved the force at failure in tibias when compared to Sham and Control groups.

CONCLUSION

MV potentiated iPTH anabolic effects in cancellous bone; however, MV was unable to maintain bone mass after stopping iPTH in ovariectomized rats.

The combined effect of Parathyroid hormone (1-34) and whole-body Vibration exercise in the treatment of postmenopausal OSteoporosis (PaVOS study): a randomized controlled trial

Treatment effects of combining teriparatide and whole-body vibration exercise (WBV) vs teriparatide alone in twelve months were compared using bone mineral density (BMD), bone microarchitecture, and bone turnover markers. We found an increased effect in lumbar spine BMD by adding WBV to teriparatide in postmenopausal osteoporotic women.

INTRODUCTION

The parathyroid hormone (PTH) analogue teriparatide is an effective but expensive anabolic treatment for osteoporosis. Whole-body vibration exercise (WBV) has been found to stimulate muscle and bone strength in some studies. Animal data demonstrate a beneficial effect on bone when combining PTH with mechanical loading. The aim of this study was to investigate if combining WBV exercise and teriparatide treatment gives additional beneficial effects on bone compared to teriparatide alone in postmenopausal women with osteoporosis.

METHODS

The PaVOS study is a randomized controlled trial where postmenopausal osteoporotic women starting teriparatide 20 μg/day were randomized to WBV + teriparatide or teriparatide alone. WBV consisted of three sessions a week (12 min, including 1:1 ratio of exercise:rest). Bone mineral density (BMD) and bone microarchitecture, bone turnover markers, and sclerostin measurements were obtained. Data were analyzed using a linear mixed regression model with adjustment for baseline values or robust cluster regression in an intention-to-treat (ITT) analysis.

RESULTS

Thirty-five women were randomized (17 in teriparatide + WBV group and 18 in teriparatide group). At 12 months, both groups increased significantly in BMD at the lumbar spine. The teriparatide + WBV group increased by (mean ± SD) 8.90% ± 5.47 and the teriparatide group by 6.65% ± 5.51. The adjusted treatment effect of adding WBV to teriparatide was statistically significant at 2.95% [95% CI = 0.14-5.77; P = 0.040]. Markers of bone turnover increased significantly in both groups at three and six months with no significant difference between groups. No other treatment effects were observed in hip BMD, bone microarchitecture parameters, or sclerostin levels in either group.

CONCLUSION

Twelve months of WBV and teriparatide had a significant clinically relevant treatment effect in lumbar spine BMD compared to teriparatide alone in postmenopausal osteoporotic women. ClinicalTrials.gov :(NCT02563353).

Effect of alendronate or 8-prenylnaringenin applied as a single therapy or in combination with vibration on muscle structure and bone healing in ovariectomized rats

Bisphosphonate alendronate (ALN), phytoestrogen 8-prenylnaringenin (8-PN) and the whole body vibration exert a favorable effect on osteoporotic bone. However, the impact of these treatments and the combination of pharmacological therapies with biomechanical stimulation on muscle and bone has not yet been explored in detail. The effect of ALN and 8-PN and their combination with the vibration (Vib) on skeletal muscle and bone healing was investigated in ovariectomized (Ovx) rats.

Three-month old rats were Ovx (n = 78), or left intact (Non-Ovx; n = 12). Five weeks after Ovx, all rats were treated according to the group assignment (n = 12/13): 1) Non-Ovx; 2) Ovx; 3) Ovx + Vib; 4) Ovx + ALN; 5) Ovx + ALN + Vib; 6): Ovx + 8-PN; 7) Ovx + 8-PN + Vib. Treatments with ALN (0.58 mg/kg BW, in food), 8-PN (1.77 mg/kg BW, daily s.c. injections) and/or with vertical vibration (0.5 mm, 35 Hz, 1 g, 15 min, 2×/day, 5×/week) were conducted for ten weeks. Nine weeks after Ovx, all rats underwent bilateral tibia osteotomy with plate osteosynthesis and were sacrificed six weeks later.

Vibration increased fiber size and capillary density in muscle, enlarged callus area and width, and decreased callus density in tibia, and elevated alkaline phosphatase in serum. ALN and ALN + Vib enhanced capillarization and lactate dehydrogenase activity in muscle. In tibia, ALN slowed bone healing, ALN + Vib increased callus width and density, enhanced callus formation rate and expression of osteogenic genes. 8-PN and 8-PN + Vib decreased fiber size and increased capillary density in muscle; callus density and cortical width were reduced in tibia. Vibration worsened 8-PN effect on bone healing decreasing the callus width and area.

Our data suggest that Vib, ALN, 8-PN, or 8-PN + Vib do not appear to aid bone healing. ALN + Vib improved bone healing; however application is questionable since single treatments impaired bone healing. Muscle responds to the anti-osteoporosis treatments and should be included in the evaluation of the drugs.

•

Vibration (Vib) was beneficial for muscle structure, it tended to interfere with early bone healing.

•

Alendronate (ALN) enhanced capillary density and metabolism in muscle, slowed bone healing.

•

8-Prenylnaringenin (8-PN) had favorable effects on muscle, for bone healing it was disadvantageous.

•

8PN + Vib further worsened 8-PN effect on bone, ALN + Vib improved bone healing.

•

Muscles respond to anti-osteoporosis treatments, their analysis should be included in the evaluation of drugs.

Effects of RANKL Knockdown by Virus-like Particle-Mediated RNAi in a Rat Model of Osteoporosis

Rebalancing of the RANKL/OPG system seems to be an effective treatment strategy in postmenopausal osteoporosis. Here, we evaluate the knockdown of RANKL by in-vivo-delivered siRNA in a rat model of osteoporosis. Virus-like-particles (VLPs) derived from polyoma JC virus were used for delivering RANKL siRNA in ovariectomized (OVX) rats. 48 rats were ovariectomized and treated with either 17β-estradiol (E2), VLPs containing RANKL siRNA (siRANKL), or VLPs containing non-cognate siRNA (siCtrl). All OVX groups were subdivided into the prophylaxis group (PG) and the therapy group (TG). The PG received treatment directly after being OVX for 10 weeks. The TG received treatment 5 weeks after being OVX for 5 weeks. Rats were sacrificed 10 weeks after being OVX. Bone and blood samples were analyzed. E2 and siRANKL showed a significant knockdown of RANKL mRNA. A protein knockdown was observed with E2 and siRANKL in the TG but not in the PG. No distinct improvements in biomechanical and morphological properties of the bones were observed after siRANKL treatment. In the PG, E2 protected the bone structure. We demonstrated successful mRNA and protein knockdown by VLP-mediated RNAi in vivo. Knockdown of membranous RANKL did not result in significant improvements of bone properties in this model of early-stage postmenopausal osteoporosis.

Effect of Strontium Ranelate on the Muscle and Vertebrae of Ovariectomized Rats

Osteoporosis is often accompanied by sarcopenia. The effect of strontium ranelate (SR) on muscle tissue has not been investigated sufficiently. In this study, the effect of different SR treatments on muscle was studied. Additionally, the lumbar vertebrae were analyzed. Three-month-old female rats were divided into five groups (n = 12): Group 1: untreated (NON-OVX); Group 2: ovariectomized and left untreated (OVX); Group 3: SR after OVX until the study ended (13 weeks, SR prophylaxis and therapy = pr+th); Group 4: OVX and SR for 8 weeks (SR prophylaxis = pr); Group 5: SR for 5 weeks from the 8 week after OVX (SR therapy = SR th). SR was applied in food (630 mg/kg body weight). The size of muscle fibers, capillary density, metabolic enzymes, and mRNA expression were assessed in soleus, gastrocnemius, and longissimus muscles. The vertebral bodies underwent micro-CT, biomechanical, and ashing analyses. In general, SR did not alter the muscle histological parameters. The changes in fiber size and capillary ratio were related to the body weight. Myostatin mRNA was decreased in Sr pr+th; protein expression was not changed. SR th led to increase in mRNA expression of vascular endothelial growth factor (Vegf-B). In lumbar spine, SR pr+th enhanced biomechanical properties, bone mineral density, trabecular area, density, and thickness and cortical density. The reduced calcium/phosphate ratio in the SR pr+th group indicates the replacement of calcium by strontium ions. SR has no adverse effects on muscle tissue and it shows a favorable time-dependent effect on vertebrae. A functional analysis of muscles could verify these findings.

The Effect of Vibration Treatments Combined with Teriparatide or Strontium Ranelate on Bone Healing and Muscle in Ovariectomized Rats

The aim of the present study was to study the effect of combined therapy of teriparatide (PTH) or strontium ranelate (SR) with whole-body vibration (WBV) on bone healing and muscle properties in an osteopenic rat model. Seventy-two rats (3 months old) were bilaterally ovariectomized (Ovx), and 12 rats were left intact (Non-Ovx). After 8 weeks, bilateral transverse osteotomy was performed at the tibia metaphysis in all rats. Thereafter, Ovx rats were divided into six groups (n = 12): (1) Ovx-no treatment, (2) Ovx + vibration (Vib), (3) SR, (4) SR + Vib, (5) PTH, and (6) PTH + Vib. PTH (40 μg/kg BW sc. 5×/week) and SR (613 mg/kg BW in food daily) were applied on the day of ovariectomy, vibration treatments 5 days later (vertical, 70 Hz, 0.5 mm, 2×/day for 15 min) for up to 6 weeks. In the WBV + SR group, the callus density, trabecular number, and Alp and Oc gene expression were decreased compared to SR alone. In the WBV + PTH group, the cortical and callus widths, biomechanical properties, Opg gene expression, and Opg/Rankl ratio were increased; the cortical and callus densities were decreased compared to PTH alone. A case of non-bridging was found in both vibrated groups. Vibration alone did not change the bone parameters; PTH possessed a stronger effect than SR therapy. In muscles, combined therapies improved the fiber size of Ovx rats. WBV could be applied alone or in combination with anti-osteoporosis drug therapy to improve muscle tissue. However, in patients with fractures, anti-osteoporosis treatments and the application of vibration could have an adverse effect on bone healing.