Intermittent treatments of prostaglandin E2 plus risedronate and prostaglandin E2 alone are equally anabolic on tibial shaft of ovariectomized rats

Chios Mastic Gum Consumption Has a Protective Effect on Ovariectomy-Induced Bone Loss in Rats

The purpose of this study was to examine the potential effect of Chios Mastic Gum (CMG) consumption on bone mineral density (BMD) and strength of ovariectomized rats. CMG is a known resin used from ancient times for its beneficial biological properties. Thirty mature female Wistar rats were randomized into three equal groups: sham-operated (control), ovariectomized (OVX), and ovariectomized and administered CMG per os (OVX+CMG). BMD of the total tibia, proximal tibia, and the 6th lumbar vertebra were measured at baseline and at 3 and 6 months post ovariectomy. Bone strength was assessed with three-point-bending (3pb) of the right femur. At 3 and 6 months, BMD values of the OVX+CMG group were significantly higher for the anatomical cites evaluated than those of the OVX group. Femoral thickness assessed via 3pb had intermediate values in the treated group compared to the other groups. Cytology of vaginal smears and uterine weight of the OVX+CMG group were consistent with estrogen depletion. Gastrocnemius muscle and intraperitoneal fat ratios to body weight (BW) of the OVX+CMG group did not significantly differ from the control group. Daily consumption CMG had a protective effect on BMD of the total and proximal tibia and the 6th lumbar vertebra of the rats, without causing undesirable effects on the vaginal epithelium and uterus. The 3pb results also demonstrated a favorable effect on the thickness of rat femurs. In addition, CMG was beneficial for both the muscular system and the intraperitoneal fat/BW ratio of the rats.

Lipid-nucleic acid nanoparticles of novel ionizable lipids for systemic BMP-9 gene delivery to bone-marrow mesenchymal stem cells for osteoinduction

Rational design of novel ionizable lipids for development of lipid-nucleic acid nanoparticles (LNP) is required for safe and effective systemic gene delivery for osteoporosis. LNPs require suitable characteristics for intravenous administration and effective accumulation in bone marrow for enhanced transfection. Hence, lipids with C18 tail and ionizable headgroup (Boc-His-ODA/BHODA and His-ODA/HODA) were synthesized and characterized physicochemically. LNPs were prepared with bone morphogenetic protein-9 gene (BHODA-LNP, HODA-LNP, and bone-homing peptide targeted HODA-LNP - HODA-LNPT). Thorough physicochemical (electrolyte stability, DNase I and serum stability) and biological (hemolysis, ROS induction, cytotoxicity and transfection) characterization was carried out followed by acute toxicity studies and therapeutic performance studies in ovariectomized rat model. Lipids with pH dependent ionization were successfully synthesized. LNPs thereof were ∼100 nm size with stability against electrolytes, DNase I and serum and exhibited low hemolytic potential demonstrating suitability for intravenous administration. LNPs exhibited minimal cytotoxicity, non-significant ROS induction and high transfection. In vivo studies demonstrated safety and improved bone regeneration in OVX rats with HODA-LNPT showing significantly better performance. Synthesized ionizable lipids offer safe and effective alternative for preparation of LNPs for gene delivery. Targeted BMP-9 LNP show potential for systemic osteoporosis treatment.

Continuous PGE2 leads to net bone loss while intermittent PGE2 leads to net bone gain in lumbar vertebral bodies of adult female rats

The present study examined the effects of continuous and intermittent PGE2 administration on the cancellous and cortical bone of lumbar vertebral bodies (LVB) in female rats. Six-month-old Sprague-Dawley female rats were divided into 6 groups with 2 control groups and 1 or 3 mg PGE2/kg given either continuously or intermittently for 21 days. Histomorphometric analyses were performed on the cancellous and cortical bone of the fourth and fifth LVBs. Continuous PGE2 exposure led to bone catabolism while intermittent administration led to bone anabolism. Both routes of administration stimulated bone remodeling, but the continuous PGE2 stimulated more than the intermittent route to expose more basic multicellular units (BMUs) to the negative bone balance. The continuous PGE2 caused cancellous bone loss by stimulating bone resorption greater than formation (i.e., negative bone balance) and shortening the formation period. It caused more cortical bone loss than gain, the magnitude of the negative endocortical bone balance and increased intracortical porosity bone loss was greater than for periosteal bone gain. The anabolic effects of intermittent PGE2 resulted from cancellous bone gain by positive bone balance from stimulated bone formation and shortened resorption period; while cortical bone gain occurred from endocortical bone gain exceeding the decrease in periosteal bone and increased intracortical bone loss. Lastly, a scheme to take advantage of the marked PGE2 stimulation of lumbar periosteal apposition in strengthening bone by converting it to an anabolic agent was proposed.

Bone degeneration and recovery after early and late bisphosphonate treatment of ovariectomized wistar rats assessed by in vivo micro-computed tomography

Bisphosphonates are antiresorptive drugs commonly used to treat osteoporosis. It is not clear, however, what the influence of the time point of treatment is. Recently developed in vivo micro-computed tomographic (CT) scanners offer the possibility to study such effects on bone microstructure in rats. The aim of this study was to determine the influence of early and late zoledronic acid treatment on bone in ovariectomized rats, using in vivo micro-CT. Twenty-nine female Wistar rats were divided into the following groups: ovariectomy (OVX, n = 5), OVX and zoledronic acid (ZOL) at week 0 (n = 8), OVX and ZOL at week 8 (n = 7), and sham (n = 9). CT scans were made of the proximal tibia at weeks 0, 2, 4, 8, 12, and 16; and bone structural parameters were determined in the metaphysis. Two fluorescent labels were administered to calculate dynamic histomorphometric parameters. At week 16, all groups were significantly different from each other in bone volume fraction (BV/TV), connectivity density, and trabecular number (Tb.N), except for the early ZOL and control groups which were not significantly different for any structural parameter. After ZOL treatment at week 8, BV/TV, structure model index, Tb.N, and trabecular thickness significantly improved in the late ZOL group. The OVX and ZOL groups showed, respectively, higher and lower bone formation rates than the control group. Early ZOL treatment inhibited all bone microstructural changes seen after OVX. Late ZOL treatment significantly improved bone microstructure, although the structure did not recover to original levels. Early ZOL treatment resulted in a significantly better microstructure than late treatment. However, late treatment was still significantly better than no treatment.

Intermittent on/off prostaglandin E2 and risedronate are equally anabolic as daily PGE2 alone treatment in cortical bone of ovariectomized rats

In this study, we evaluated the rat cortical bone changes after a two-cycle, 60-day each (ON/OFF/ON/OFF) treatment with either prostaglandin E2 (OVX/c-PGE2) alone or in combination with risedronate (OVX/c-PGE2+Ris), in comparison with daily treatment with PGE2 for 240 days (OVX/PGE2-240d) in ovariectomized (OVX) rats. At the end of the study, we found that: (1) the overall effectiveness of the treatment on bone mass in the tibial shaft indicates the following ranking: OVX/PGE2-240d = OVX/c-PGE2+Ris > OVX/c-PGE2 > OVX/c-Ris > or = OVX = aging; (2) the same bone mass and architecture were produced in the OVX/PGE2-240d and the OVX/c-PGE2+Ris groups, but the histomorphometric profiles differed in that the former exhibited a higher bone turnover and index of resorption; (3) OVX/c-PGE2+Ris treatment prevented endocortical bone loss and minimized trabecular bone loss during the OFF periods; and (4) the OVX/c-PGE2 alone treatment resulted in the accumulation of less total bone than OVX/PGE2-240d and OVX/c-PGE2+Ris because it could not maintain most of the new subendocortical and marrow trabecular bone generated earlier. In summary, both continuous daily PGE2 and two cycles ON/OFF combined PGE2 and Ris treatments result in more bone mass than two cycles ON/OFF PGE2 alone and Ris alone in estrogen-deficient rats. This study showed that the anabolic effects of PGE2 can be induced and maintained either by continuous administration or by cyclical PGE2+Ris.

Prostaglandin E2 (PGE2) and risedronate was superior to PGE2 alone in maintaining newly added bone in the cortical bone site after withdrawal in older intact rats

The objects of this study were (1) to determine the effects of risedronate (Ris) and prostaglandin E2 (PGE2) alone and in combination, on tibial diaphyses of older intact female rats; and (2) to observe the fate of any extra bone if formed after withdrawal of the treatment. Nine-month-old female Sprague-Dawley rats were treated with 6 mg of PGE2/kg/day, 1 or 5 micrograms of Ris/kg twice a week, or 6 mg of PGE2/kg/day plus 1 or 5 micrograms of Ris/kg twice a week for the first 60 days and followed by vehicle injections for another 60 days. Cross-sections of double fluorescent labeled, undecalcified tibial diaphyses proximal to the tibiofibular junction were processed for histomorphometry. We found that: (1) neither the 1 microgram nor the 5 micrograms of Ris treatment in the 60-day on/60-day off group showed any histomorphometric differences from age-related controls; (2) while the 60 days of PGE2 treatment added extra cortical bone (6%) on the tibial shaft (due to stimulation of periosteal, endocortical, and marrow trabecular bone formation), the new endocortical and most of the new marrow trabecular bone were lost when treatment was withdrawn; however, the new periosteal bone remained; (3) PGE2 with Ris added the same amount of new bone to tibial diaphysis as did PGE2 alone and upon withdrawal, new marrow trabecular bone was lost but new periosteal and endocortical bones were preserved in PGE2 + 1 microgram of Ris on/off group. In contrast, all the new bone was maintained in the PGE2 + 5 micrograms of Ris on/off group; (4) PGE2 + Ris cotreatment failed to block the increase in cortical bone porosity induced by PGE2; and (5) in the PGE2 alone and PGE2 + 1 microgram of Ris on/off groups bone turnover was higher than that in the PGE2 + 5 micrograms of Ris on/off group. These results indicate that on/off treatment with PGE2 and Ris is superior to PGE2 alone in that it forms the same amount of new bone during treatment, but preserves more cortical bone during withdrawal. Depression of bone resorption and turnover were the tissue mechanisms responsible for this protection.