The effects of strength training and raloxifene on bone health in aging ovariectomized rats

The microarchitecture and chemical composition of the femur neck of senescent female rats after different physical training protocols

A sedentary lifestyle, coupled with a decrease in estrogen, impairs bone homeostasis, favoring to the development of osteopenia and osteoporosis, both recognized as risk factors for fractures. Here, we investigated the quality of the femur, particularly the femur neck region, and the ambulation performance of senescent rats subjected to three different physical training protocols during the periestropause period. Forty-eight female rats, 18 months of age, were subjected to a 120-day training period, three times a week. The rats were distributed into four groups: aerobic training (AT), strength training (ST), concurrent training (CT), or no training (NT). After the experimental period, at 21 months of age, ambulation performance and femur were analyzed using microtomography, Raman stereology, densitometry, and mechanical strength tests. The results demonstrated greater remodeling activity and improvement in resistance and bone microarchitecture in the femur neck of senescent female rats after undergoing physical training. Our verified higher intensities of bands related to collagen, phosphate, amide III, and amide I. Furthermore, the analysis of the secondary collagen structures indicated alterations in the collagen network due to the exercise, resulting in increased bone strength. Both AT and strength-based training proved beneficial, with AT showing greater adaptations in bone density and stiffness in the femur, while strength-based training greater adaptations in trabecular and cortical structure. These insights contribute to the understanding of the potential interventions for preventing osteopenia and osteoporosis, which are critical risk factors for fractures.

Effect of robotic gait training on muscle and bone characteristics in spinal cord transected rats

Osteoporosis and loss of muscle mass are secondary issues with spinal cord injury. Robotic gait training has provided evidence of increasing bone density and muscle mass, but its effect on bone strength is undetermined. The purpose of this study was to determine the effect of a 6-week robotic locomotion training program on skeletal muscle mass and bone characteristics. Twelve female Sprague-Dawley rats received a mid-thoracic spinal cord transection at 5 days old and at 3 weeks old were assigned to a Control or Trained Group. The Trained Group performed 5-min sessions on the Rat Stepper 5 days a week for 6 weeks with 90% of body weight supported. At the end of the 6 weeks, body mass was obtained and right femurs and four lower extremity muscles were harvested. Femur bone mineral density was measured with DXA and mechanical characteristics of the femur were determined via 3-point bending testing. Independent t-tests, effects sizes and percent differences were computed between the two groups (p < 0.05). The Trained Group had significantly larger normalized femur mass (p = 0.007) and normalized soleus muscle mass (p = 0.033) when compared to the Control Group. There was a medium or large effect size with the Trained Groups' femurs having larger mass, bone mineral density, rupture loads, cortical wall thickness, shaft cross sectional area, soleus mass, normalized gastrocnemius mass, and smaller shaft inner diameters compared to the Control Group. These changes may contribute to decreasing osteoporosis and fracture risk in those with spinal cord injuries.

The Role of Oxidative Stress in Multiple Exercise-Regulated Bone Homeostasis

Bone is a tissue that is active throughout the lifespan, and its physiological activities, such as growth, development, absorption, and formation, are always ongoing. All types of stimulation that occur in sports play an important role in regulating the physiological activities of bone. Here, we track the latest research progress locally and abroad, summarize the recent, relevant research results, and systematically summarize the effects of different types of exercise on bone mass, bone strength and bone metabolism. We found that different types of exercise have different effects on bone health due to their unique technical characteristics. Oxidative stress is an important mechanism mediating the exercise regulation of bone homeostasis. Excessive high-intensity exercise does not benefit bone health but induces a high level of oxidative stress in the body, which has a negative impact on bone tissue. Regular moderate exercise can improve the body's antioxidant defense ability, inhibit an excessive oxidative stress response, promote the positive balance of bone metabolism, delay age-related bone loss and deterioration of bone microstructures and have a prevention and treatment effect on osteoporosis caused by many factors. Based on the above findings, we provide evidence for the role of exercise in the prevention and treatment of bone diseases. This study provides a systematic basis for clinicians and professionals to reasonably formulate exercise prescriptions and provides exercise guidance for patients and the general public. This study also provides a reference for follow-up research.

Postmenopausal osteoporosis: Effect of moderate-intensity treadmill exercise on bone proteomics in ovariectomized rats

Objectives

This study aimed to identify the key proteins in the bone mass of ovariectomized (OVX) rats after a period of regular moderate-intensity treadmill exercise and to investigate their effects using tag mass spectrometry and quantitative proteomics with a view to improving the understanding and treatment of postmenopausal osteoporosis.

Methods

Sixty three-month-old female Sprague-Dawley tats of specific-pathogen-free grade were randomly and equally divided into a sham operation group, ovariectomized group (OVX) and ovariectomized combined exercise (OVX + EX) group, and the latter took moderate-intensity treadmill exercise for 17 weeks. After this period of time, body composition and bone density were measured using dual-energy x-ray absorptiometry, and serum bone metabolism indicators were measured using an enzyme immunoassay. In addition, the bone microstructure was examined using micro-computed tomography and scanning of the femur, and femur proteins were subject to proteomic analysis.

Results

Compared with the rats in the OVX group, the bone metabolism indicators in the OVX + EX group decreased significantly, femur bone density increased significantly, the number of the trabeculae increased, and continuity was higher. In the OVX + EX group, 17 proteins were significantly upregulated and 33 significantly downregulated. The main gene ontology and signaling pathways enriched by the proteins were identified as the tumor necrosis factor-mediated signaling pathways. The protein-protein interaction network identified the key proteins, and the correlation analysis of these proteins and the bone parameters found histone deacetylase 8(HDAC8) and leucine-rich transmembrane and O-methyltransferase domain containing (LRTOMT) and trimethylguanosine synthase 1(TGS1) and ankyrin repeat domain 46(ANKRD46) to be the key targets of exercise in relation to postmenopausal osteoporosis.

Conclusion

Moderate-intensity treadmill exercise significantly improved the bone mass of OVX rats, and differentially expressed proteins, such as HDAC8 and LRTOMT and TGS1 and ANKRD46, could be the target of moderate-intensity treadmill exercise.

Analysis of the femoral neck from rats in the periestropause treated with oxytocin and submitted to strength training

Among the interventions used to prevent osteoporosis in female organisms, strength training (ST) and oxytocin (OT) stand out, as a promising hormone with anabolic action on bone. This study aimed to verify whether the combined action of OT and ST, compared to isolated interventions, potentiates the bone remodeling process of the femoral neck of Wistar rats during periestropause. Forty Wistar rats (18 months) with irregular estrous cycle were randomly distributed into groups: 1-Vehicle (Veh; NaCl 0.15 mol/L ip); 2-Oxytocin (Ot; 134 μg/kg/ip); 3-Strength training (St); 4-Ot + St. The animals of the 1, 2 and 4 groups received two intraperitoneal injections with an interval of 12 h every 30 days, totaling 8 injections at the end of the experimental period (18 to 21 months). The animals in the St and Ot + St groups performed ST on a ladder 3 times a week, maximal voluntary carrying capacity (MVCC) test monthly. After 120 days, the animals were euthanized; the femur was collected for analysis of biomechanical testing, densitometry, bone microtomography, Raman spectroscopy, tissue PCR, and blood for analysis of bone biomarkers, liver damage, and oxidative stress. The main effects in the Ot group were observed in the maximum load and energy in the compression testing (femoral head), and stiffness and energy in the three-points bending testing (femur diaphysis). In addition, the main effects occurred on the bone mineral density (BMD), cortical thickness (Ct.Th), number of pores (Po.N), polar moment of inertia (J), trabecular thickness (Tb.Th), and connectivity density (Conn.Dn), Bone alkaline phosphatase (Alp), Tumor necrosis factor receptor superfamily member 11b (Opg), Tumor necrosis factor ligand superfamily member 11 (Rankl) and Cathepsin K (Ctsk) expression. There was an effect in the tartrate-resistant acid phosphatase (TRAP) and alkaline phosphatase (ALP). In the St group, the main effect was observed on the energy (compression and the three-points bending), stiffness, aBMD, BMD, cortical bone area (Ct.Ar), Po.N, trabecular bone volume (BV/TV), Tb.Th and in the mineralization ratio (ѵ₁PO₄/proline), Runt-related transcription factor 2 (Runx2), Bone morphogenetic protein 2 (Bmp2), Alp, Osteopontin/secreted phosphoprotein 1 (Opn/Spp1), Opg, Tumor necrosis factor receptor superfamily member 11ª (Rank), Rankl, Ctsk expression. There was an effect in the TRAP and ALP. The interaction in the combination of therapies in the Ot + St group was verified in energy to maximum load (compression and three-points bending testing), stiffness, BMD, Ct.Th, J, Tb.Th and ѵ₁PO₄/proline. In the gene analysis there was interaction in the Runx2, Osterix/Sp7 transcription factor (Osx/Sp7), Bmp2, Alp, Osteocalcin/Bone gamma-carboxyglutamate protein (Ocn/Bglap), Opg, Rankl and Acid phosphatase 5, tartrate resistant (Trap/Acp5) expression. In addition, the combination of OT and ST resulted in a higher maximum load compared to the Veh group, with higher BV/TV than the Ot group, higher Rankl and Ctsk expression than Veh and Ot groups, and lower Po.N and lower activity of TRAP than the other groups. In oxidative stress, total antioxidant capacity (TAC) was lower. These results showed that the combination of interventions is a promising anabolic strategy for the prevention of osteoporosis in the period of periestropause, standing out from the effects of isolated interventions.

Milk kefir therapy improves the skeletal response to resistance exercise in rats submitted to glucocorticoid-induced osteoporosis

Glucocorticoid-induced osteoporosis (GIO) has emerged as a challenge after long-term glucocorticoids (GCs) administration. Exercise has been an important non-pharmacological option, while medications modulate bone remodeling despite adverse effects. In this way, milk Kefir (MK) therapy stands out as a safe alternative to improve bone metabolism. Our study aimed to investigate the effect of MK associated to resistance exercise on bone loss in rats with GIO. For this, sixty male Wistar rats were divided into 2 groups: normal (N) and subjected to GIO, which was subdivided into 4 groups: control (C), milk kefir therapy (K), Exercise (Ex), and Exercise+K (ExK). GIO was induced by dexamethasone (7 mg/kg - i.m.; 1×/wk, 5 wk). MK was administered daily (1×/day; 0.7 ml/animal) and the climb exercise with load was performed 3×/wk; both for 16 wk. Femur was collected for assessment of bone microarchitecture, quality and metabolism. GIO markedly reduced trabecular bone volume density (BV/TV) (-35 %), trabecular thickness (Tb.Th) (-33 %), mineral content of femur (-26 %) as well as bone collagen content (-56 %). Bone strength and its biomechanical properties given by flexural strength (-81 %), fracture load (-80 %), and the number of osteocytes (-84 %) were lowered after GIO. GCs reduced osteoblast number and function while increased osteoclast number, altering bone remodeling (p < 0.05). On the other hand, ExK significantly improved bone microarchitecture and quality, marked by fractal dimension increase (+38 %), cortical volume (+34 %), BV/TV (+34 %), Tb.Th (+33 %), mineral content and collagen maturity, while reduced the space between trabecula (-34 %). The Ex and ExK increased the number of osteocytes (p < 0.05) and they were able to reverse the lower osteoblast number. Both treatments used alone significantly enhanced bone biomechanical properties, but the ExK showed a more significant improvement. ExK ameliorated bone strength and biomechanics (p < 0.05) and stimulated bone formation and modulated bone remodeling (p < 0.05). MK and exercise administered isolated or in association increased the percentage of collagen bone filling after GIO (p < 0.05), but only ExK improved collagen maturity. Our results showed that MK associated to resistance exercise enhanced bone microarchitecture, quality and metabolism, being therefore an interesting tool to improve skeletal response during GIO.

Locally Applied Repositioned Hormones for Oral Bone and Periodontal Tissue Engineering: A Narrative Review

Bone and periodontium are tissues that have a unique capacity to repair from harm. However, replacing or regrowing missing tissues is not always effective, and it becomes more difficult as the defect grows larger. Because of aging and the increased prevalence of debilitating disorders such as diabetes, there is a considerable increase in demand for orthopedic and periodontal surgical operations, and successful techniques for tissue regeneration are still required. Even with significant limitations, such as quantity and the need for a donor area, autogenous bone grafts remain the best solution. Topical administration methods integrate osteoconductive biomaterial and osteoinductive chemicals as hormones as alternative options. This is a promising method for removing the need for autogenous bone transplantation. Furthermore, despite enormous investigation, there is currently no single approach that can reproduce all the physiologic activities of autogenous bone transplants. The localized bioengineering technique uses biomaterials to administer different hormones to capitalize on the host’s regeneration capacity and capability, as well as resemble intrinsic therapy. The current study adds to the comprehension of the principle of hormone redirection and its local administration in both bone and periodontal tissue engineering.

Alleviative Effects of Exercise on Bone Remodeling in Fluorosis Mice

Fluorine is widely present in nature in the form of fluoride. Prolonged high-dose fluoride exposure can cause skeletal fluorosis, resulting in osteosclerosis, osteoporosis or osteomalacia. It has been proved that exercise is one of the important factors affecting the health of the bone and promoting bone formation. To investigate the effects of exercise on bone remodeling in fluorosis mice, 120 male 3-week-old ICR mice were randomly divided into four groups: control group (C), exercise group (E), fluoride group (F), fluoride plus exercise group (F + E). After 8-week physical exercise and/or fluoride exposure, we evaluated the content of fluorine, the histopathological structure and microstructure of femur, bone metabolism biochemical indexes and oxidative stress related parameters, and the mRNA and protein levels of genes in BMP-2/Smads and OPG/RANKL/RANK signaling pathways. Our results showed that 100 mg/L NaF exposure increased the accumulation of fluoride in bone, altered histology of bone, and enhanced the activities of ALP and TRACP. Meanwhile, excessive fluoride induced oxidative stress in bone tissue by increasing the content of ROS and MDA, and decreasing the activities of antioxidant enzymes. In addition, the results of qRT-PCR suggested that NaF significantly increased the mRNA expression of BMP-2, Smad-5, Col IA1, Col IA2, OPG, RANKL and RANK, as well as the elevated proteins of OPG, RANKL and RANK. However, these fluoride-induced changes were alleviated after moderate exercise. Taken together, these findings indicated that moderate exercise decreased the toxicity of fluoride by reducing the accumulation of fluorine in the body to relieve the bone damage caused by fluorosis.

Raloxifene inhibits the overexpression of TGF-β1 in cartilage and regulates the metabolism of subchondral bone in rats with osteoporotic osteoarthritis

Overexpression of transforming growth factor-beta 1 (TGF-β1) and subchondral bone remodelling play key roles in osteoarthritis (OA). Raloxifene (RAL) reduces the serum level of TGF-β1 in postmenopausal women. However, the effect of RAL on TGF-β1 expression in articular cartilage is still unclear. Therefore, we aimed to investigate the protective effect of RAL on osteoporotic osteoarthritis via affecting TGF-β1 expression in cartilage and the metabolism of subchondral bone. Osteoporotic osteoarthritis was induced by a combination of anterior cruciate transection (ACLT) and ovariectomy (OVX). Rats were divided into five groups (n = 12): The sham group, the ACLT group, the OVX group, the ACLT + OVX group, and the RAL group (ACLT + OVX + RAL, 6.25 mg/kg/day for 12 weeks). Assessment was performed by histomorphology, microcomputed tomography (micro-CT) scan, immunohistochemistry, and tartrate-resistant acid phosphatase (TRAP) staining. We found that severe cartilage degeneration was shown in the ACLT + OVX group. The histomorphological scores, the levels of TGF-β1, and its related catabolic enzymes and osteoclasts numbers in the ACLT + OVX group were higher than those in other groups (p < 0.05). Furthermore, structure model index (SMI) and trabecular spacing (Tb.Sp) were decreased (p < 0.05), while bone mineral density (BMD), bone volume fraction (BV/TV), and trabecular number (Tb.N) were increased by RAL compared with the ACLT + OVX group (p < 0.05). Our findings demonstrated that RAL in clinical doses retards the development of osteoporotic osteoarthritis by inhibiting the overexpression of TGF-β1 in cartilage and regulating the metabolism of subchondral bone. These results provide support for RAL in the expansion of clinical indication for prevention and treatment in postmenopausal osteoarthritis.

Therapeutic potential of annatto tocotrienol with self-emulsifying drug delivery system in a rat model of postmenopausal bone loss

Tocotrienol has been shown to prevent bone loss in animal models of postmenopausal osteoporosis, but the low oral bioavailability might limit its use. A self-emulsifying drug delivery system (SEDDS) could increase the bioavailability of tocotrienol. However, evidence of this system in improving the skeletal effects of tocotrienol is scanty. This study aims to evaluate the therapeutic efficacy of annatto tocotrienol with SEDDS in a rat model of postmenopausal bone loss. Ten-month-old female Sprague Dawley rats were randomized into six groups. The baseline group was euthanatized at the onset of the study. Four other groups underwent ovariectomy to induce estrogen deficiency. The sham underwent similar surgery procedure, but their ovaries were retained. Eight weeks after surgery, the ovariectomized rats received one of the four different regimens orally daily: (a) SEDDS, (b) annatto tocotrienol [60 mg/kg body weight (b.w.)] without SEDDS, (c) annatto-tocotrienol (60 mg/kg b.w.) with SEDDS, (d) raloxifene (1 mg/kg b.w.). After eight weeks of treatment, blood was collected for the measurement of delta-tocotrienol level and oxidative stress markers. The rats were euthanized and their bones were harvested for the evaluation of the bone microstructure, calcium content and strength. Circulating delta-tocotrienol level was significantly higher in rats receiving annatto tocotrienol with SEDDS compared to the group receiving unformulated annatto-tocotrienol (p < 0.05). Treatment with unformulated or SEDDS-formulated annatto tocotrienol improved cortical bone thickness, preserved bone calcium content, increased bone biomechanical strength and increased antioxidant enzyme activities compared with the ovariectomized group (p < 0.05). Only SEDDS-formulated annatto tocotrienol improved trabecular microstructure, bone stiffness and lowered malondialdehyde level (p < 0.05 vs the ovariectomized group). The improvement caused by annatto tocotrienol was comparable to raloxifene. In conclusion, SEDDS improves the bioavailability and skeletal therapeutic effects of annatto tocotrienol in a rat model of postmenopausal bone loss. This formulation should be tested in a human clinical trial to validate its efficacy.

Recent Advances of Osterix Transcription Factor in Osteoblast Differentiation and Bone Formation

With increasing life expectations, more and more patients suffer from fractures either induced by intensive sports or other bone-related diseases. The balance between osteoblast-mediated bone formation and osteoclast-mediated bone resorption is the basis for maintaining bone health. Osterix (Osx) has long been known to be an essential transcription factor for the osteoblast differentiation and bone mineralization. Emerging evidence suggests that Osx not only plays an important role in intramembranous bone formation, but also affects endochondral ossification by participating in the terminal cartilage differentiation. Given its essentiality in skeletal development and bone formation, Osx has become a new research hotspot in recent years. In this review, we focus on the progress of Osx's function and its regulation in osteoblast differentiation and bone mass. And the potential role of Osx in developing new therapeutic strategies for osteolytic diseases was discussed.

Oxytocin and bone quality in the femoral neck of rats in periestropause

The objective of this study is to identify whether oxytocin (OT) contributes to the reduction of osteopenia in the femoral neck of rats in periestropause. Animals in irregular estrous cycles received two NaCl injections (0.15 mol/L) or OT (134 μg/kg) over a 12-h interval, and after thirty-five days without treatments, the biological sample collection was performed. The oxytocin group (Ot) demonstrated the highest enzymatic activity of alkaline phosphatase (p = 0.0138), lowest enzymatic activity of tartrate-resistant acid phosphatase (p = 0.0045), higher percentage of compact bone (p = 0.0359), cortical expression of runt-related transcription factor 2 (p = 0.0101), osterix (p = 0.0101), bone morphogenetic protein-2/4 (p = 0.0101) and periostin (p = 0.0455). Furthermore, the mineral-to-matrix ratio (ν₁PO₄/Proline) was higher and type-B carbonate substitution (CO₃/ν₁PO₄) was lower (p = 0.0008 and 0.0303) in Ot group. The Ot showed higher areal bone mineral density (p = 0.0050), cortical bone area (p = 0.0416), polar moment of inertia, maximum, minimum (p = 0.0480, 0.0480, 0.0035), bone volume fraction (p = 0.0166), connectivity density (p < 0.0001), maximal load (p = 0.0003) and bone stiffness (p = 0.0145). In Ot percentage of cortical pores (p = 0.0102) and trabecular number (p = 0.0088) was lower. The results evidence action of OT in the reduction of osteopenia, suggesting that it is a promising anabolic strategy for the prevention of primary osteoporosis during the periestropause period.

Effect of pre-treatment of strength training and raloxifene in periestropause on bone healing

BACKGROUND

There is evidence that strength training (ST) and raloxifene (Ral) treatment during periestropause promotes better bone quality. We wanted to determine whether the skeletal benefits of ST or Ral treatment, performed during periestropause, would persist after fracture. Therefore, the present study aimed to analyze the influence of pre-treatment with ST and administration of Ral during periestropause on bone healing after total unilateral osteotomy.

METHODS

Senescent female Wistar rats between 18 and 21 months of age, performed ST on a ladder three times per week, were administered Ral by gavage (2.3 mg/kg/day), or an association of both. After 120 days, the treatments were interrupted, and a total osteotomy was performed on the left tibia in all animals. They were euthanized 1 and 8 weeks post-osteotomy.

RESULTS

The administration of Ral during periestropause worsened the biochemical and oxidative profile, decreased gene expression of markers related to bone resorption and remodeling, which negatively affected the physicochemical properties; this lead to changes in the bone callus microarchitecture and mass, as well as a decrease in callus resistance to torsional deformation, resulting in lower tissue quality during bone healing. In contrast, ST performed prior to the osteotomy resulted in better bone healing, improvement of the biochemical and oxidative profile, alteration of the genetic profile in favor of bone formation and resorption, as well as the physic-ochemical properties of the callus. These changes led to better microarchitecture and bone mass and increased callus resistance to torsional deformation, confirming its beneficial effect on the quality of bone tissue, providing acceleration of bone consolidation. The combination of therapies at this exercise intensity and drug dosage showed a negative interaction, where the negative effect of Ral overcame the positive effect of ST, leading to decreased tissue quality in the bone healing process.

CONCLUSIONS

This study indicates that in addition to excellent non-pharmacological therapy and action in the prevention of osteoporosis, ST performed during the aging period may increase bone quality at the onset of healing and provide improved bone consolidation. Furthermore, the anti-osteoclastogenic effect of Ral shown in this model delayed the bone repair process, resulting in considerable clinical concern.

Effects of bazedoxifene and low-intensity aerobic exercise on bone and fat parameters in ovariectomized rats

INTRODUCTION

Postmenopausal osteoporosis and dyslipidemia are well-known skeletal and metabolic changes in middle-aged women. We investigated the effects of combined treatments with a selective estrogen receptor modulator (SERM) and exercise on bone and fat parameters in ovariectomized (OVX) rats.

MATERIALS AND METHODS

Sixteen-week-old female Sprague-Dawley rats underwent bilateral ovariectomy, and rats were randomized to BZA (bazedoxifene at 0.3 mg/kg/day), Exe (treadmill exercise at 12-15 m/min, 60 min/day, 5 days/week), Comb (BZA and Exe), and Cont (control treated with vehicle and no exercise) groups 8 weeks after ovariectomy. After 4 or 8 weeks of treatment, bone mineral density (BMD) of the total femur and lumbar spine and whole-body percentage fat mass were determined by dual-energy X-ray absorptiometry, and mechanical testing of the femoral shaft, and bone and fat histomorphometric analyses of the proximal tibia were performed.

RESULTS

Treadmill exercise had decreased bone marrow adipocytes from 4 weeks of treatment and whole-body percentage fat mass at 8 weeks. BZA increased BMD at the lumbar spine and decreased the whole-body percentage fat mass from 4 weeks and bone marrow adipocytes at 8 weeks. Combination therapy increased BMD for the lumbar spine and decreased bone marrow adipocytes and whole-body percentage fat mass from 4 weeks.

CONCLUSION

Combination therapy with BZA and exercise appears effective to improve bone and fat parameters in OVX rats.

Raloxifene retards cartilage degradation and improves subchondral bone micro-architecture in ovariectomized rats with patella baja-induced - patellofemoral joint osteoarthritis

OBJECTIVE

Abnormal remodeling of subchondral bone (SB) induced by estrogen deficiency has been shown to be involved in osteoarthritis (OA). Raloxifene (RAL) is commonly used to treat postmenopausal osteoporosis (OP). However, little is known about its effects on OA combined with estrogen deficiency. This study was performed to evaluate the efficacy of RAL on patella baja-induced patellofemoral joint OA (PFJOA) in an ovariectomized rat model.

DESIGN

Patellar ligament shortening (PLS) and ovariectomy (OVX) were performed simultaneously in 3-month-old female Sprague-Dawley rats, which were treated with RAL (10 mg/kg/day) or vehicle at 72 h postoperatively for 10 weeks. PFJOA was assessed by immunohistochemistry (IHC), real-time polymerase chain reaction (PCR), tartrate-resistant acid phosphatase (TRAP) staining, enzyme-linked immunosorbent assay (ELISA), micro-computed tomography (μCT), histomorphology and behavioral analyses.

RESULTS

X-ray examinations showed that patella baja was successfully established by PLS. Histomorphological analysis revealed that PFJOA was significantly exacerbated by OVX and markedly alleviated by RAL. Moreover, RAL improved cartilage metabolism by decreasing MMP-13, ADAMTS-4, and caspase-3 and increasing Col-II and aggrecan at both the protein and mRNA levels. Furthermore, RAL markedly improved bone mass and SB microarchitecture and reduced osteoclast numbers and the serum osteocalcin and CTX-I levels. Although RAL showed a trend toward reducing pain sensitivity based on mechanical allodynia testing, this result was not statistically significant.

CONCLUSION

These findings demonstrate that RAL treatment retards PFJOA progression in an ovariectomized rat model, suggesting that it may be a potential candidate for amelioration of the progression of PFJOA accompanied by postmenopausal OP.

Effects of leukocyte- and platelet-rich fibrin associated or not with bovine bone graft on the healing of bone defects in rats with osteoporosis induced by ovariectomy

OBJECTIVE

To evaluate the healing of critical size defects (CSDs) in calvaria of rats with osteoporosis induced by ovariectomy and treated with leukocyte- and platelet-rich fibrin (L-PRF) associated or not with bovine bone graft (XENO).

MATERIAL AND METHODS

A total of 32 rats underwent a bilateral ovariectomy procedure. After 3 months, one 5 mm in diameter CSD was created in the middle of the calvaria of each animal. In group C, defect was filled with blood clot only. In PRF, XENO, and PRF-XENO groups, defects were filled with 0.1 ml of L-PRF, 0.1 ml of XENO, and a mixture of 0.1 ml of L-PRF plus 0.1 ml of XENO, respectively. L-PRF compressed clots were used to cover the defects in PRF and PRF-XENO groups. Animals were submitted to euthanasia at 30 postoperative days. Histomorphometric, microtomographic, and immunohistochemical analyses were performed.

RESULTS

PRF-XENO group presented greater amount of neoformed bone (NB) when compared with XENO group, as well as higher expression of vascular endothelial growth factor (VEGF), osteocalcin (OCN), and bone morphogenetic protein (BMP-2/4) (p < .05). PRF group presented increased amount of NB and higher expression of VEGF, OCN, BMP-2/4, and Runt-related transcription factor 2 (RUNX-2) when compared with group C (p < .05).

CONCLUSIONS

(a) The isolated use of L-PRF clot can improve bone neoformation in CSDs in rats with osteoporosis induced by ovariectomy, but seems to lead to decreased amount of bone neoformation when compared to the isolated use of XENO; (b) L-PRF potentiates the healing of XENO in rats with osteoporosis induced by ovariectomy.

Effect of a bisphosphonate and selective estrogen receptor modulator on bone remodeling in streptozotocin-induced diabetes and ovariectomized rat model

BACKGROUND CONTEXT

Diabetes and menopause can cause severe osteoporosis. In general, menopause and diabetes can lead to an imbalance in bone turnover, which results in secondary osteoporosis. However, the efficacy of antiresorptive drugs against this form of osteoporosis has not been extensively evaluated.

OBJECTIVE

The aim of this study was to determine the changes in vertebral bone remodeling when postmenopausal osteoporosis is accompanied by diabetes and to compare the efficacy of bisphosphonates and selective estrogen-receptor modulators (SERMs) against these outcomes.

STUDY DESIGN

Streptozotocin-induced diabetic, ovariectomized Sprague-Dawley rats were used as the disease model. Alendronate and raloxifene were used as the bisphosphonate and SERM, respectively.

METHODS

We divided 62 female rats into five groups: (1) control (n=14), (2) DM (diabetes) (n=12), (3) DM+OVX (diabetes+ovariectomy) (n=12), (4) DM+OVX+A (diabetes+ovariectomy+alendronate) (n=12), and (5) DM+OVX+R (diabetes+ovariectomy+raloxifene) (n=12). Serum biochemical markers of bone turnover, including osteocalcin and the C-telopeptide of type I collagen (CTX-1), were analyzed. We measured histomorphometric parameters of the fourth lumbar vertebrae using microcomputed tomography. Mechanical strength was evaluated by a compression test.

RESULTS

In the DM and DM+OVX group, only the levels of osteocalcin significantly decreased compared with those of the control group at 8 weeks after OVX. At 12 weeks, the serum CTX-1 levels in the DM+OVX+A and DM+OVX+R groups were significantly lower than those of the DM+OVX group, but there were no changes in the levels of osteocalcin. Bone mineral density and mechanical strength were higher in the DM+OVX+A and DM+OVX+R groups than in the DM and DM+OVX groups (p<.05).

CONCLUSIONS

Even if postmenopausal osteoporosis is accompanied by diabetes in this animal model, both alendronate and raloxifene seem to show antiresorptive effects, decreased bone turnover rates, and improved bone mechanical strength. Therefore, alendronate and raloxifene are effective in the treatment of osteoporosis even for bone loss caused by DM and postmenopausal osteoporosis.

Oxytocin effects on osteoblastic differentiation of Bone Marrow Mesenchymal Stem Cells from adult and aging female Wistar rats

Recently, it has been suggested that oxytocin (OT) might play a role in the control of bone remodeling and in bone health of young and adult females. The purpose of this study was to evaluate the effect of osteogenic medium (OM) plus OT (OM + OT; 100 nmol/L) on osteoblastic differentiation of bone marrow mesenchymal stem cells (BMMSCs) from cyclic adult (12 months old) and acyclic aging (24 months old) female Wistar rats. After 14 days, OM + OT increased the oxytocin and oxytocin receptor in the BMMSCs from animals of both age groups relative to OM controls. Alkaline phosphatase activity was higher in the OM + OT than OM group in BMMSCs from 24-month-old female rats. OM + OT improved osteogenic differentiation, observed by anticipated mineralization and increased gene expression of bone morphogenetic protein 2, bone sialoprotein, osteopontin and osteocalcin in both aged relative to OM controls. These findings suggest a role for OT as an adjuvant to induce osteoblastic differentiation of BMMSCs from aged female rat.

A SERM increasing the expression of the osteoblastogenesis and mineralization-related proteins and improving quality of bone tissue in an experimental model of osteoporosis

Raloxifene is an antiresorptive drug, selective estrogen receptor modulator (SERM) used in the treatment of osteoporosis. Objective To evaluate proteins related to bone repair at the peri-implant bone in a rat model of osteoporosis treated with raloxifene. Material and Methods 72 rats were divided into three groups: SHAM (healthy animals), OVX (ovariectomized animals), and RLX (ovariectomized animals treated with raloxifene). Raloxifene was administered by gavage (1 mg/kg/day). Tibial implantation was performed 30 days after ovariectomy, and animals were euthanized at 14, 42, and 60 days postoperatively. Samples were collected and analyzed by immunohistochemical reactions, molecular analysis, and microtomographic parameters. Results RLX showed intense staining of all investigated proteins at both time points except for RUNX2. These results were similar to SHAM and opposite to OVX, showing mild staining. The PCR gene expression of OC and ALP values for RLX (P<0.05) followed by SHAM and OVX groups. For BSP data, the highest expression was observed in the RLX groups and the lowest expression was observed in the OVX groups (P<0.05). For RUNX2 data, RLX and SHAM groups showed greater values compared to OVX (P<0.05). At 60 days postoperatively, microtomography parameters, related to closed porosity, showed higher values for (Po.N), (Po.V), and (Po) in RLX and SHAM groups, whereas OVX groups showed lower results (P<0.05); (BV) values (P=0.009); regarding total porosity (Po.tot), RLX group had statistically significant lower values than OVX and SHAM groups (P=0.009). Regarding the open porosity (Po.V and Po), the SHAM group presented the highest values, followed by OVX and RLX groups (P<0.05). The Structural Model Index (SMI), RLX group showed a value closer to zero than SHAM group (P<0.05). Conclusions Raloxifene had a positive effect on the expression of osteoblastogenesis/mineralization-related proteins and on micro-CT parameters related to peri-implant bone healing.

Effects of strength training and raloxifene on femoral neck metabolism and microarchitecture of aging female Wistar rats

The aim of this study was to prevent female osteoporosis using strength training (ST), raloxifene (Ral) or a combination of ST plus Ral during the natural female aging process, specifically in the periestropause period. For a total of 120 days, aging female Wistar rats at 18-21 months of age performed ST on a ladder three times per week, and Ral was administered daily by gavage (1 mg/kg/day). Bone microarchitecture, areal bone mineral density, bone strength of the femoral neck, immunohistochemistry, osteoclast and osteoblast surface were assessed. We found that the treatments modulate the bone remodeling cycle in different ways. Both ST and Ral treatment resulted in improved bone microarchitecture in the femoral neck of rats in late periestropause. However, only ST improved cortical microarchitecture and bone strength in the femoral neck. Thus, we suggest that performing ST during the late period of periestropause is a valid intervention to prevent age-associated osteoporosis in females.

The effects of downhill and uphill exercise training on osteogenesis-related factors in ovariectomy-induced bone loss

PURPOSE

Recent evidence suggests that regular exercise training plays a decisive role in maintaining homeostasis and promoting muscle and skeletal formation. However, the effect of downhill exercise training on osteogenesis-related factors is not well understood.

METHODS

Thus, we investigated the effect of uphill and downhill training on ovariectomy (OVX)-induced bone loss. After ovary removal, the exercise method performed included uphill (16 m/min, +15°) and downhill training (16 m/min, -15°) for 60 min/day and 5 days/week, respectively, for 8 weeks.

RESULTS

Our results showed that both uphill and downhill training significantly decreased the body weight, total cholesterol, and creatine kinase (CK) levels in the context of OVX-induced bone loss. On the contrary, levels of an osteogenesis indicator, osteocalcin and alkaline phosphatase were elevated. Consequently, the uphill and downhill training reduced OVX- induced bone loss in the distal femoral metaphysis. Likewise, the bone microstructure in OVX-induced bone loss was enhanced upon training. In particular, the inhibition of RANKL-induced osteoclast formation and osteoclast-specific gene expression improved upon downhill training compared to uphill training.

CONCLUSION

These results suggest that the uphill and downhill exercise types appeared to positively affect the expression of osteogenesis-related factors along with bone density and microstructure. Particularly, the downhill training has more beneficial effects on the maintenance of homeostasis during bone formation.

Sustained raloxifene release from hyaluronan-alendronate-functionalized titanium nanotube arrays capable of enhancing osseointegration in osteoporotic rabbits

To enhance the localized bone remodeling at titanium-based implants under osteoporotic conditions, TiO₂ nanotube arrays (TNT) were used as nanoreserviors for raloxifene (Ral) and then covered with the hybrid multilayered coating of chitosan and alendronate grafted hyaluronic acid (HA-Aln) via a spin-assisted layer-by-layer technique. The fabrication of this system (TNT/Ral/LBL-Aln) was characterized by field emission scanning electron microscopy (SEM), atomic force microscope (AFM) and X-ray photoelectron spectroscopy (XPS), respectively. The release test showed that the composited multilayers onto Ral-loaded TiO₂ nanotube substrate (TNT/Ral) could prevent the burst release of Ral from TiO₂ nanotube arrays and maintain stable Ral concentration at the implant site even after 192h. The TNT/Ral/LBL-Aln system demonstrated higher alkaline phosphatase (ALP) activity, mineralization capability in osteoblasts as well as lower tartrate-resistant acid phosphatase (TRAP) activity in osteoclasts compared to both bare TiO₂ nanotube and TNT/Ral substrate, respectively. Moreover, the in vivo tests of micro-CT, histological staining and push-out testing showed that TNT/Ral/LBL-Aln implant could efficiently enhance the formation of new bone around the implant and promote bone binding in osteoporotic rabbits. The study indicated the potential application of TNT/Ral/LBL-Aln system for bone remodeling under osteoporotic condition.

Effects of strength training on osteogenic differentiation and bone strength in aging female Wistar rats

The effects of strength training (ST) on the mechanical bone strength and osteogenic differentiation of bone marrow mesenchymal stromal cells (BMSCs) from adult, aged and exercised aged rats were determined. The exercised aged animals displayed higher values of areal bone mineral density, compression test, alkaline phosphatase activity (ALP) and biological mineralization, while oil red O staining for adipocytes was lower. ST increased gene expression of runt-related transcription factor 2 (Runx2), osterix (Osx) as well as bone matrix protein expression, and reduced expression of peroxisome proliferator-activated receptor gamma (Pparγ). The production of pro-inflammatory cytokine tumor necrosis factor alpha (TNF-α) was lower in BMSCs of the aged exercised group. The ST practice was able to improve the bone mechanical properties in aged female rats, increasing the potential for osteogenic differentiation of BMSCs, reducing the adipogenic differentiation and pro-inflammatory cytokine level. In summary, the data achieved in this study showed that strength training triggers physiological responses that result in changes in the bone microenvironment and bring benefits to biomechanical parameters of bone tissue, which could reduce the risk of fractures during senescent.

Strength training prior to muscle injury potentiates low-level laser therapy (LLLT)-induced muscle regeneration

We evaluated whether strength training (ST) performed prior to skeletal muscle cryolesion would act as a preconditioning, improving skeletal muscle regeneration and responsiveness to low-level laser therapy (LLLT). Wistar rats were randomly assigned into non-exercised (NE), NE plus muscle lesion (NE + LE), NE + LE plus LLLT (NE + LE + LLLT), strength training (ST), ST + LE, and ST + LE + LLLT. The animals performed 10 weeks of ST (climbing ladder; 3× week; 80% overload). Forty-eight hours after the last ST session, tibialis anterior (TA) cryolesion was induced and LLLT (InGaAlP, 660 nm, 0.035 W, 4.9 J/cm²/point, 3 points, spot light 0.028 cm², 14 J/cm²) initiated and conducted daily for 14 consecutive days. The difference between intergroups was assessed using Student's t test and intragroups by two-way analysis of variance. Cryolesion induced massive muscle degeneration associated with inflammatory infiltrate. Prior ST improved skeletal regeneration 14-days after cryolesion and potentiated the regenerative response to LLLT. Cryolesion induced increased TNF-α levels in both NE + LE and ST + LE groups. Both isolated ST and LLLT reduced TNF-α to control group levels; however, prior ST potentiated LLLT response. Both isolated ST and LLLT increased IL-10 levels with no additional effect. In contrast, increased TA IL-6 levels were restricted to ST and ST + LE + LLLT groups. TA myogenin mRNA levels were not changed by neither prior ST or ST + LLLT. Both prior ST and LLLT therapies increased MyoD mRNA levels and, interestingly, combined therapies potentiated this response. Myf5 mRNA levels were increased only in ST groups. Taken together, our data provides evidences for prior ST potentiating LLLT efficacy in promoting skeletal muscle regeneration.