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.

It is well documented that intermittent PGE(2) treatment increases both trabecular and cortical bone mass. However, the effects of continuous PGE(2) administration remain undocumented. The aim of the study was to investigate the effects of continuous prostaglandin E(2) (PGE(2)) on different bone sites in skeletally mature rats. Six-month-old Sprague Dawley rats were treated with PGE(2) at 1 or 3 mg/kg/d continuously via infusion pump for 21 days. Two other groups of rats received PGE(2) at the same doses by intermittent (daily) subcutaneous injections and served as positive controls. Histomorphometry was performed on cancellous bone of the proximal tibial metaphysis and cortical bone of the tibial shaft. As expected, intermittent PGE(2) treatment increased both cancellous and cortical bone mass by stimulating bone formation at the cancellous, periosteal and endocortical bone surfaces. In contrast, continuous PGE(2) treatment decreased cancellous bone mass with bone resorption exceeding bone formation. In addition, continuous PGE(2) treatment increased endocortical and intracortical bone remodeling, inducing bone loss which was partially offset by stimulating periosteal expansion. We conclude that continuous PGE(2) treatment induces overall catabolic effects on both cancellous and cortical bone envelopes, which differs from intermittent PGE(2) treatment that is anabolic. Lastly, we speculate that superior bone mass may be achieved by co-treatment of continuous PGE(2) in combination with an anti-catabolic agent.

Vitamin D receptor (VDR) ligands are therapeutic agents for the treatment of psoriasis, osteoporosis, and secondary hyperparathyroidism. VDR ligands also show immense potential as therapeutic agents for autoimmune diseases and cancers of skin, prostate, colon, and breast as well as leukemia. However, the major side effect of VDR ligands that limits their expanded use and clinical development is hypercalcemia that develops as a result of the action of these compounds mainly on intestine. In order to discover VDR ligands with less hypercalcemia liability, we sought to identify tissue-selective VDR modulators (VDRMs) that act as agonists in some cell types and lack activity in others. Here, we describe LY2108491 and LY2109866 as nonsecosteroidal VDRMs that function as potent agonists in keratinocytes, osteoblasts, and peripheral blood mononuclear cells but show poor activity in intestinal cells. Finally, these nonsecosteroidal VDRMs were less calcemic in vivo, and LY2108491 exhibited more than 270-fold improved therapeutic index over the naturally occurring VDR ligand 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3] in an in vivo preclinical surrogate model of psoriasis.

Previously we found that PGE(2) 3 mg/kg in 20-month-old male rats induced massive bone formation mainly by modeling dependent bone gain in cortical bone. It is not known whether cancellous bone will respond similarly; thus, we evaluated the effect of PGE(2) on cancellous bone of the same aged rats. Thirty-four 20-month-old Wistar male rats were given PGE(2) (3 mg/kg/day) or vehicle subcutanously for 10 and 30 days. Double fluorescent labels were injected 9 and 2 days prior to the sacrifice. Histomorphometry was performed on 1% toluidine blue stained and unstained sagittal sections of lumbar vertebral bodies. The results demonstrated that 10-day PGE(2) treatment increased osteoprogenitor cells, osteoblasts (x2-fold), osteoid (x4.5-fold), woven bone formation (0.04%), and 40% more trabecular area; it stimulated modeling (x2-fold) and remodeling-dependent (x1.5-fold) bone formation with increase of mineralization lag time (MLT, x 7.5-fold). Thirty-day treatment sustained increases in osteoblast numbers, modeling, and remodeling-dependent bone formation and further stimulated woven bone formation (6.6%), turnover (x3-fold), and trabecular area and number (x2-fold). Osteoprogenitor cells were undetectable along with 70% less osteoid area compared with 10-day treatment but still was 1.5-fold higher than aging controls. MLT returned to aging control level. It was concluded that the aged cancellous bone of 20-month-old male Wistar rat retains a capability of responding to the anabolic effect of PGE(2). Osteoblastogenesis and enhanced modeling and remodeling-dependent woven or lamellar formation contribute to this anabolic action. Bone formation differed in that the endocortical surface of cortical bone was stimulated mainly by modeling whereas both modeling and remodeling-dependent bone gain were equally stimulated at the trabecular surface of the lumbar vertebral body.

Cyclosporine A (CsA) is associated with posttransplantation bone disease. Immunosuppressant drugs such as sirolimus (SRL), which are more potent and less deleterious than CsA, are being developed. Previous experiments have shown that SRL although immunosuppressive, is relatively bone sparing. The use of low doses of CsA and SRL in combination has displayed in vivo synergism, This study was initiated to examine the effect of low-dose CsA and SRL on bone metabolism, thereby hopefully providing a bone sparing immunosuppressive regimen for transplant recipients. One hundred and nineteen rats were divided into groups: basal, vehicle, CsA high dose, CsA low dose, SRL low dose, and combination low-dose CsA and SRL, The basal group was killed on day 0 for histomorphometry, The experimental groups were weighed and bled on days 0, 28, 56, and 84 and were killed on day 84 for histomorphometry. Serial assays for blood urea nitrogen (BUN), creatinine, and osteocalcin were performed. Osteocalcin was raised on days 28 and 56 in the high dose CsA group. Histomorphometry showed osteopenia with high-dose CsA, Low-dose CsA was relatively bone sparing, while low-dose SRL and combined low-dose CsA did not cause bone loss. In conclusion, the synergistic combination of low-dose CsA and SRL has the potential of providing both bone sparing and immunosuppressive benefits.

Previous reports showed that bone mass and architecture only partially recovered by remobilization (RM) after immobilization (IM)-induced osteopenia, and that parathyroid hormone (PTH) had an anabolic effect on the skeleton. The aim of this study was to determine whether low doses of PTH could restore IM-induced cortical bone loss and whether a combination of PTH plus loading (RM) treatment would be more effective than the PTH in unloaded (IM) limbs. One hundred and sixty 6-month-old rats were divided into aging and IM groups. The right hindlimb of the rat was immobilized by elastic bandage for 18 weeks, and then groups of rats were either kept IM or RM and treated with 30 microgram or 80 microgram of hPTH(1-38)/kg/day for 2, 10, and 20 weeks. Fluorescent-labeled, undecalcified cross-sections of right tibial shafts were studied. We found that RM for 20 weeks after 18 weeks of IM only partially recovered IM-induced muscle weight loss and PTH had no effect on muscle weight in either IM or RM limbs; that RM for 20 weeks after 18 weeks of IM partially restored some minimal cortical width by stimulating periosteal and endocortical bone formation and decreasing endocortical resorption; that PTH treatment of IM limbs completely restored IM-induced cortical bone loss and added extra bone by stimulating bone formation indices on all bone surfaces and depressing bone resorption on endocortical surface; that PTH treatment of RM limbs produced similar anabolic effects as in IM limbs with 30 microgram/kg/day dose but the 80 microgram/kg/day dose-treated limbs had a higher periosteal bone formation rate, which created a larger cross-sectional area, more cortical bone area, and a thicker cortex than the same dose treated IM limbs; and that PTH 80 microgram/kg/day treatment produced more anabolic effect than the 30 microgram/kg/day in both IM and RM limbs. We concluded that reloading the hindlimb by RM after long-term IM could not recover the cortical bone mass. PTH at employed doses was able to completely restore IM-induced cortical bone loss, and this effect was independent of mechanical stimulation. However, when PTH was combined with mechanical loading (RM), a synergistic anabolic effect on periosteal bone formation occurred which increased the cross sectional area that can increase bone strength.

To investigate whether the aminopeptidase B and leucine aminopeptidase inhibitor bestatin, the chymase inhibitor chymostatin, the calpain inhibitor E-64 and the neub-al sedne protease inhibitor leupeptin affect the angiotensin converting enzyme (ACE) activity in T-lymphecytes.ACE-activity in homogenates of T-lymphecytes or in intact T-lymphocytes in suspension was measured by determing fluonmetncally histidyl-leucine, formed from the conversion of hippurylhistidyl-leucine, coupled with o-phtaldialdehyde.The effect of various concentrations (10-~ -10 .3M) of the angiotensin-converting enzyme inhibitors lisinopril and captopdl and of the venous protease inhibitors on ACE-activity was studied.Lisinopril and captopnl concentration-dependently reduce the ACEactivity in homogenates of T-lymphocytes.Lisinopdl exhibit a more pronounced inhibition of ACE in T-tymphocytes than captopdl.Chymostatin and E-64 have no effect on the ACE-activity in T-tymphocytes, while leupeptin dose-dependently inhibits its activity.Bestatin on the contrary increases dose-dependently the ACE-activity in hornoganates of T-

Interferons (IFN) are a group of related glycoproteins. IFN-γ, in vitro, has been shown to inhibit resorption; however, an in vivo experiment showed that it had the opposite effect, resulting in bone loss that was comparable to that caused by cyclosporine A. IFN-α has numerous clinical applications but is used most extensively in the treatment of chronic hepatitis B and chronic hepatitis C. Research into the effects of IFN-α on bone mineral metabolism has been very sparse, and the majority of studies reflect in vitro models. Like IFN-γ, there exists discordance between in vitro and in vivo studies on IFN-α. Both in vivo and in vitro studies demonstrate that IFN-α decreases bone resorption, whereas osteoblasts may or may not be affected in vivo. This study was designed to provide information on the in vivo effects of IFN-α in the rat model, because we feel that, given its widespread clinical use, this is an extremely important issue. Rats were given low dose IFN-α (1.6 × 106 IU/m2), intermediate dose IFN-α (5.35 × 106 IU/m2), and high dose IFN-α (30 × 106 IU/m2) three times per week for 28 days. Serum osteocalcin (bone gla protein, or BGP) and parathyroid hormone (PTH) were measured serially and, after double labeling, the bones were examined histomorphometrically. IFN-α did not alter any of the histomorphometric parameters measured and did not affect PTH. However, it produced a disparate BGP response. Low dose IFN-α resulted in a statistically significant increase in serum BGP on days 14 and 28, whereas intermediate and high doses of IFN-α did not. Overall, these results provide no evidence of a deleterious effect of IFN-α on bone metabolism and confirm the limited clinical study.

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 ≥ 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.

To study the anti-resorptive effects of zoledronate and pamidronate on growing long bones we have performed a histomorphometric analysis of the three regions of the proximal tibial cancellous bone of bone formed before, during, and after drug treatment. Male rats (190-220 g) were treated subcutaneously for 10 days with zoledronate (0.028-2.8 microg/kg) or pamidronate (3.7-370 microg/kg) and sacrificed 5 days later. To delineate the three regions of cancellous bone, and for dynamic bone histomorphometry, calcein and demeclocycline were injected at various times. Both bisphosphonates caused a dose-dependent suppression of cancellous bone turnover and resorption to produce an increase in cancellous bone, but zoledronate was 100 times more potent than pamidronate. The increase in the bone amount and connectivity was more pronounced in the bone formed during treatment where transient bone resorption and normal bone formation led to a positive bone balance. In the bone formed before treatment, inhibition of bone resorption associated with reduced bone formation produced a net gain in amount of bone. Although both bone regions showed a positive bone balance, more bone accumulated in the bone formed during treatment probably because its trabecular bone surface was three times greater. In the primary spongiosa formed after treatment, a moderate increase in the bone amount and connectivity was observed only at the highest dose of both bisphosphonates. The bone formed before, during, and after treatment with bisphosphonates responds differently due to differences in bone architecture, rates of modeling and remodeling, and period of drug exposure.

Diseases such as periodontitis and osteoporosis are expected to rise tremendously by 2050. Bone formation and remodeling are complex processes that are disturbed in a variety of diseases influenced by various hormones.This study aimed to review and present the roles of various hormones that regulate bone remodeling of the craniofacial complex.A literature search was conducted on PubMed and Google Scholar for studies related to hormones and jawbone. Search strategies included the combinations (“name of hormone” + “dental term”) of the following terms: “hormones”, “oxytocin”, “estrogen”, “adiponectin”, “parathyroid hormone”, “testosterone”, “insulin”, “angiotensin”, “cortisol”, and “erythropoietin”, combined with a dental term “jaw bone”, “alveolar bone”, “dental implant”, “jaw + bone regeneration, healing or repair”, “dentistry”, “periodontitis”, “dry socket”, “osteoporosis” or “alveolitis”. The papers were screened according to the inclusion criteria from January 1, 2000 to March 31, 2021 in English. Publications included reviews, book chapters, and original research papers; in vitro studies, in vivo animal, or human studies, including clinical studies, and meta-analyses.Bone formation and remodeling is a complex continuous process involving many hormones. Bone volume reduction following tooth extractions and bone diseases, such as periodontitis and osteoporosis, cause serious problems and require a great understanding of the process.Hormones are with us all the time, shape our development and regulate homeostasis. Newly discovered effects of hormones influencing bone healing open the possibilities of using hormones as therapeutics to combat bone-related diseases.

BACKGROUND:The skeletal impact of estrogen deficiency on subjects with hypertension has not been studied previously. In this study, we examined the skeletal characteristics of female spontaneously hypertensive rats (SHR) and their normotensive genetic control Wistar-Kyoto rat (WKY). We aimed to reveal: 1) the skeletal characters of female SHR, and 2) the response of SHR to ovariectomy (ovx) when compared to WKY and other strains.METHODS:Undecalcified double-fluorescent labeled cancellous (proximal tibial metaphysis, PTM) and cortical (tibial shaft, TX) bones from 23-weeks-old, and from rats 2 and 8 weeks post-ovx were studied.RESULTS:The SHR showed lower body weight, higher heart rate, and higher blood pressure than the WKY. Female SHR possessed more percent cancellous bone, less net cortical bone, smaller tissue area, and thinner cortex than WKY. Furthermore, SHR exhibited an age-related cancellous (-18%) and cortical (-7%) bone loss associated with a decrease in the longitudinal growth rate and bone balance and a decrease in periosteal bone formation in cortical bone. In contrast, the WKY maintained most of these parameters unchanged at their 23-week-old levels. Ovariectomy induced earlier and greater cancellous bone loss in the SHR than in the WKY, with greater increases in bone turnover rate, eroded surface, activation frequency, and a decrease in the ratio of labeled to eroded perimeter in PTM at 2 weeks postsurgery. However, the two groups exhibited no differences in bone loss at 8 weeks after ovx in PTM and TX.CONCLUSIONS:Spontaneously hypertensive rats were highly sensitive to estrogen deficiency. This might have clinical relevance to those postmenopausal women who suffer from hypertension, in that they may be more susceptible to osteopenia. If so, preventive measures should be initiated sooner than otherwise.

Skeletal effects of moexipril, an angiotensin-converting enzyme (ACE) inhibitor, and hydrochlorothiazide (HCTZ), a thiazide diuretic, were studied in ovariectomized (OVX) spontaneously hypertensive rats (SHR). Moexipril (10 mg/kg per day), HCTZ (10 mg/kg per day), alone or in combination, as well as 17 alpha-estradiol (30 micrograms/kg per day) were given to OVX SHR immediately after surgery and studied for short- and long-term effects (14 and 56 days respectively). All drugs were given orally. Histomorphometric data on the secondary spongiosa of proximal tibial metaphyses (cancellous bone) and tibiofibular junctions of tibial shafts (cortical bone) were analyzed. Ovariectomy induced cancellous bone loss in SHR by inducing negative bone balance. Estrogen prevented ovariectomy-induced cancellous bone loss in the SHR by reducing bone turnover and partially suppressing the coupling of bone formation to resorption on the endocortical surface. HCTZ reduced blood pressure after 1 week of treatment, yet this effect was no lower than that seen in controls after 3 weeks of treatment. Two weeks of HCTZ transiently prevented ovariectomy-induced increases in bone turnover rate and eroded surface. This delayed ovariectomy induced trabecular bone loss in the proximal tibial metaphysis, but had no effect on the tibial shaft. Like HCTZ, moexipril also reduced blood pressure after the first week of treatment but it had no apparent effect on either the proximal tibial metaphysis or the tibial shaft. A combination of moexipril and HCTZ exhibited a much more potent hypotensive effect and had the same effect on bone mass and dynamic end-points as HCTZ alone. Our data indicate that (1) HCTZ treatment has some transient beneficial effects on both antihypertension and osteoprotection in hypertensive osteopenic rats, (2) the combination of moexipril with HCTZ improved the antihypertensive effect but did not potentiate or hamper the osteoprotective effect of HCTZ, and (3) the skeletal effect of estrogen is not impacted by the hypertensive state. These findings are relevant for the use of ACE inhibitor and thiazide diuretics, alone or in combination, in antihypertensive therapy in postmenopausal women.