Identification of a vibration regime favorable for bone healing and muscle in estrogen-deficient rats.

Numerous whole-body vibration (WBV) devices of various forces are available on the market, although their influence on the musculoskeletal system is not yet understood. The effect of different WBVs on bone healing and muscle function was evaluated in rats ovariectomized at 3 months of age. 2 months after ovariectomy, bilateral metaphyseal tibia osteotomy and T-plate osteosynthesis were performed. Rats were divided into groups: intact, OVX, and OVX exposed to vertical WBVs of 35, 50, 70, or 90 Hz (experiment 1) or horizontal WBVs of 30, 50, 70, or 90 Hz (experiment 2) 5 days after osteotomy (0.5 mm, 15 min/day for 30 days). The tibia and gastrocnemius and soleus muscles were collected. Vertical vibrations (>35 Hz) improved cortical and callus densities, enlarged callus area and width, suppressed the tartrate-resistant acid phosphatase gene, enhanced citrate synthase activity, accelerated osteotomy bridging (35 and 50 Hz), upregulated the osteocalcin (Oc) gene (70 Hz), and increased relative muscle weight (50 Hz). Horizontal vibrations reduced cortical width (<90 Hz) and callus density (30 Hz), enhanced alkaline phosphatase (Alp) gene expression (50 Hz), decreased the size of oxidative fibers (35 and 70 Hz), and increased capillary density (70, 90 Hz). Biomechanical data; serum Oc, Alp, and creatine kinase activities; body weight; and food intake did not change after WBVs. Vertical WBVs of 35 and 50 Hz produced more favorable results than the higher frequencies. Horizontal WBV showed no positive or negative effects. Further studies are needed to elucidate the effects of WBV on different physiological systems, and precautions must be taken when implementing WBV in the treatment of patients.

Musculoskeletal response to whole-body vibration during fracture healing in intact and ovariectomized rats.

This study investigated the effect of vibration on bone healing and muscle in intact and ovariectomized rats. Thirty ovariectomized (at 3 months of age) and 30 intact 5-month old female Sprague-Dawley rats underwent bilateral metaphyseal osteotomy of tibia. Five days later, half of the ovariectomized and of the intact rats were exposed to whole-body vertical vibration (90 Hz, 0.5 mm, 4 x g acceleration) for 15 min twice a day during 30 days. The other animals did not undergo vibration. After decapitation of rats, one tibia was used for computed tomographic, biomechanical, and histological analyses; the other was used for gene expression analyses of alkaline phosphatase (Alp), osteocalcin (Oc), tartrate-resistant acid phosphatase 1, and insulinlike growth factor 1. Serum Alp and Oc were measured. Mitochondrial activity, fiber area and distribution, and capillary densities were analyzed in M. gastrocnemius and M. longissimus. We found that vibration had no effect on body weight and food intake, but it improved cortical and callus densities (97 vs. 99%, 72 vs. 81%), trabecular structure (9 vs. 14 trabecular nodes), blood supply (1.7 vs. 2.1 capillaries/fiber), and oxidative metabolism (17 vs. 23 pmol O(2)/s/mg) in ovariectomized rats. Vibration generally increased muscle fiber size. Tibia biomechanical properties were diminished after vibration. Oc gene expression was higher in vibrated rats. Serum Alp was increased in ovariectomized rats. In ovariectomized rats, vibration resulted in an earlier bridging; in intact rats, callus bridging occurred later after vibration. The chosen vibration regimen (90 Hz, 0.5 mm, 4 x g acceleration, 15 min twice a day) was effective in improving musculoskeletal tissues in ovariectomized rats but was not optimal for fracture healing.

Whole body vibration during fracture healing intensifies the effects of estradiol and raloxifene in estrogen-deficient rats.

Current osteoporosis therapies aim to delay bone destruction and have additional anabolic effects. While they have demonstrated some positive effects on bone healing, more progress is needed in this area. This study used the well-known osteoporotic agents estrogen (E) and raloxifene (R) in conjunction with biomechanical whole body vibration (WBV) at a frequency of 70 Hz twice daily for six weeks to stimulate bone healing. Eighty-four 3-month old female Sprague-Dawley rats (12 per group) were bilaterally ovariectomized to develop osteopenia within eight weeks. Osteotomy of the metaphyseal tibiae was performed and fracture healing was then studied using mechanical tests, histomorphometry, computed tomography (µCT), and gene analysis. We found that E and R improved the structure of osteopenic bones as did WBV alone, although significant levels for WBV were seldom reached. Combination treatments significantly enhanced stiffness (R+WBV; p<0.05), endosteal bone (R+WBV; p<0.01), and trabecular density (E+WBV; p<0.05, R+WBV; p<0.05). In addition, the expression of osteoclast-specific Trap was significantly reduced after treatment with E, R, or their combination with WBV (p<0.01). The effects were additive and not inhibitory, leading us to conclude that the combined applications of WBV with E or R may improve the healing of osteopenic bones. The therapies studied are all currently approved for human use, suggesting ready applicability to clinical practice. To better understand the effects of WBV on osteopenic bones, the ideal vibration regime will require further study.

Influence of intermittent administration of parathyroid hormone on muscle tissue and bone healing in orchiectomized rats or controls.

Influence of human parathyroid hormone (hPTH 1-34) on muscle and bone healing was studied in either orchiectomized (Orx at 8 months of age) or sham-operated male rats. Eleven-month-old Sprague-Dawley rats underwent bilateral transverse metaphyseal osteotomy of tibia and were divided into four groups (n=12): 1) sham-vehicle, 2) sham group-PTH everyday, 3) Orx-vehicle, 4) Orx-PTH everyday, and 5) Orx-PTH every other day. PTH dosage was 40  µg/kg body weight. After 5 weeks, fiber cross-sectional area, capillary density, and enzyme activity (lactate dehydrogenase, citrate synthase, and complex I) were measured in soleus (MS), gastrocnemius (MG), and longissimus (ML) muscles; tibiae were analyzed by computed tomographical, histological, and gene expression analyses. The effect of PTH in all rats was increased serum osteocalcin, cortical and callus densities and callus area. In sham rats capillary density was increased in limb muscles (MS: 1.3-1.7, MG: 1.2-1.4 capillaries/fiber), and rate of osseous bridging of osteotomy was enhanced (67-100%). In Orx rats serum creatine kinase was decreased (6670-2847 U/l), and bone genes (Igf-1, osteoprotegerin, and receptor activator of nuclear factor kB ligand) were up-regulated. Cross-sectional area, enzyme activity, food intake, weight of body, visceral organs, adipose tissue, MG, and MS were not affected by PTH. PTH had a favorable effect on muscle capillary density and improved bone healing being more effective in sham rats and having no adverse systemic effect. The effect was less if PTH was applied every other day. The findings may show up trends for therapeutic treatment of male patients.

Impact of 4-methylbenzylidene camphor, daidzein, and estrogen on intact and osteotomized bone in osteopenic rats.

The study investigated the influence of 4-methylbenzylidene camphor (4-MBC), daidzein, and estradiol-17ß-benzoate (E(2)) on either intact or osteotomized cancellous bone in ovariectomized (Ovx) rats. Three-month old Ovx rats were fed with soy-free (SF) diet over 8 weeks; thereafter, bilateral transverse metaphyseal osteotomy of tibia was performed and rats were divided into groups: rats fed with SF diet and SF diet supplemented with 4-MBC (200 mg), daidzein (50 mg), or E(2) (0.4 mg) per kilogram body weight. After 5 or 10 weeks, computed tomographical, biomechanical, histological, and ashing analyses were performed in lumbar spine and tibia of 12 rats from each group. 4-MBC and E(2) improved bone parameters in lumbar spine and tibia, were not favorable for osteotomy healing, and decreased serum osteocalcin level. However, daidzein improved bone parameters to a lesser extent and facilitated osteotomy healing. For lumbar spine, the bone mineral density was 338±9, 346±5, 361±6, and 360±5 mg/cm(3) in SF, daidzein, 4-MBC, and E(2), respectively, after 10 weeks. For tibia, the yield load was 98±5, 114±3, 90±2, and 52±4 N in SF, daidzein, 4-MBC, and E(2), respectively, after 10 weeks. Serum daidzein was 54±6 ng/ml in daidzein group and equol was not detected. Alp and Igf1 genes were down-regulated in callus after daidzein and E(2) compared with 4-MBC (week 5). The response of bone tissue and serum markers of bone metabolism could be ordered: daidzein<4-MBC

Effect of human parathyroid hormone hPTH (1-34) applied at different regimes on fracture healing and muscle in ovariectomized and healthy rats.

Three experiments were conducted to investigate the effect of intermittent administration of parathyroid hormone (PTH) (1-34) applied at different regimes on fracture healing and muscle in healthy and ovariectomized (Ovx at 3 months of age) rats. Five-month old rats underwent bilateral transverse metaphyseal osteotomy of tibia and were divided into groups (12 rats each). In Exp 1, Ovx rats were either treated with PTH (7x/w, 1-35d), with oral estradiol-17beta-benzoate (0.4 mg/kg BW, 1-35d) or untreated. In Exp. 2, there were 3 groups: healthy untreated or treated with PTH (5x/w, 1-35d or 7-35d). In Exp. 3, there were 7 groups: healthy, Ovx, "healthy PTH 5x/w 7-35d", "Ovx PTH 5x/w 7-35d, 14-35d or 14-28d", "Ovx PTH every other day 7-35d". Single dosage of PTH was 40 microg/kg BW. After 35 days of healing one tibia was analyzed by computed tomographical, biomechanical, histological analyses. The other tibia was used in analyses of Alp, Oc, Trap 1, Igf-1, Rankl, Opg genes (Exp.2, 3). Serum Oc and Alp were measured. Body, uterus weight was recorded. M. gastrocnemius was analyzed for weight (Exp. 2), fiber size and mitochondrial respiratory activity (MRA) (Exp.3). Estrogen enhanced uterus weight, prevented body increase, however, did not improve bone healing in Ovx rats (Exp. 1). PTH administration from days 1 and 7 improved bone parameters in all rats regardless of the application frequency (7, 5x/w or every other day) (Exp. 1, stiffness Ovx: 118+13 N/mm, Ovx PTH: 250+/-20 N/mm) being more effective in healthy rats (Exp. 3, stiffness improvement Healthy: 59 to 174 N/mm, Ovx: 52 to 98 N/mm). Serum Oc level was elevated in PTH treated rats. Application from day 14 proved to be less effective (Exp. 3). PTH had no effect (P>0.05) on body, uterus and muscle weight, muscle fiber size, MRA and expression of bone markers. PTH promoted bone healing in Ovx and healthy rats, when it is applied during early stage of healing without having any adverse systemic effect. In perspective, PTH may represent a treatment for enhancement of fracture healing. The findings need to be confirmed by follow-up studies on other animals.

Short-term effects of parathyroid hormone on rat lumbar vertebrae.

STUDY DESIGN: This study is an experimental study in the rat osteopenia model. OBJECTIVE: The aim of this study was to evaluate the short-term effects of daily application of parathyroid hormone (PTH) on bone quality and quantity using a new biomechanical compression test for intact rat lumbar vertebrae. SUMMARY OF BACKGROUND DATA: Because of their high clinical relevance, trabecular content and thick cortical shell vertebrae are of high interest for osteoporosis research. Biomechanical stability depends on both trabecular and cortical bone. Anabolic effects on bone after long-term application of PTH have already been proven. METHODS: After an intraindividual comparison (n = 20), the capability of a new test to identify biomechanical properties of the mature rat model was assessed. In the following, 33 three-month-old rats were ovariectomized. After 10 weeks, the animals were divided into 3 groups. The control group (C) received no additional food supplementation. The other groups received hormone treatment with either estradiol (E) or PTH for another 5 weeks. The effects on bone biomechanical properties and bone microstructure were analyzed. RESULTS: After establishing the new biomechanical test for intact rat lumbar vertebrae, PTH-treated (yield stress: 2.95 N/mm, elastic limit: 2.39 N/mm) and then E-treated (yield stress: 2.13 N/mm, elastic limit: 1.68 N/mm) animals showed superior biomechanical results. Compression strength was significantly improved in these rats in comparison to the control group rats (yield stress: 1.86 N/mm, elastic limit: 1.38 N/mm). In the microradiographic evaluation, PTH significantly improved the morphologic results to produce thicker trabeculae. E led to a more densely branched trabecular network, which was not as important as trabecular thickness for bone stability. CONCLUSION: After a short-term application, PTH is superior to E in recreating bone biomechanical propertiesand lumbar vertebral microstructure in advanced osteoporosis. The cortical shell and trabecular thickness are primarily responsible for the biomechanical strength of vertebrae.