The extracts of osteoblast developed from adipose-derived stem cell and its role in osteogenesis

Cell-based therapy has become an achievable choice in regenerative medicines, particularly for musculoskeletal disorders. Adipose-derived stem cells (ASCs) are an outstanding resource because of their ability and functions. Nevertheless, the use of cells for treatment comes with difficulties in operation and safety. The immunological barrier is also a major limitation of cell therapy, which can lead to unexpected results. Cell-derived products, such as cell extracts, have gained a lot of attention to overcome these limitations. The goal of this study was to optimize the production of ASC-osteoblast extracts as well as their involvement in osteogenesis. The extracts were prepared using a freeze-thaw method with varying temperatures and durations. Overall, osteogenic-associated proteins and osteoinductive potential of the extracts prepared from the osteogenic-induced ASCs were assessed. Our results demonstrated that the freeze-thaw approach is practicable for cell extracts production, with minor differences in temperature and duration having no effect on protein concentration. The ASC-osteoblast extracts contain a significant level of essential specialized proteins that promote osteogenicity. Hence, the freeze-thaw method is applicable for extract preparation and ASC-osteoblast extracts may be beneficial as an optional facilitating biologics in bone anabolic treatment and bone regeneration.

Bone Health ECHO Case Report: Fractures and Hypercalcemia in a Patient with Stage 5 Chronic Kidney Disease

Bone Health ECHO (Extension for Community Healthcare Outcomes) is a virtual community of practice with the aim of enhancing global capacity to deliver best practice skeletal healthcare. The prototype program, established at the University of New Mexico, has been meeting online weekly since 2015, focusing on presentation and discussion of patient cases. These discussions commonly cover issues that are relevant to a broad range of patients, thereby serving as a force multiplier to improve the care of many patients. This is a case report from Bone Health ECHO about a patient with stage 5 chronic kidney disease, hypercalcemia, and low bone density, and the discussion that followed.

Oral Administration of Isovitexin, a Naturally Occurring Apigenin Derivative Showed Osteoanabolic Effect in Ovariectomized Mice: A Comparative Study with Teriparatide

Isovitexin (apigenin-6C-glucopyranose) is found in several food items and medicinal plants. Recently, we showed that isovitexin stimulated osteoblast differentiation through mitochondrial biogenesis and respiration that required adiponectin receptors (AdipoRs). Here, we studied whether oral isovitexin has a bone anabolic effect in vivo. At first, using a femur osteotomy model in adult mice, we compared the bone regenerative effect of isovitexin and apigenin. Whereas isovitexin-stimulated bone formation at the osteotomy site at 2.5 mg/kg and 5 mg/kg dose, apigenin had no effect. Subsequently, we tested the effect of isovitexin (5 mg/kg) in ovariectomized (OVX) osteopenic mice and observed that it restored bone mass and architecture of trabecular bones (femur metaphysis and fifth lumbar vertebra/L5) and cortical bones (femur diaphysis). Isovitexin completely restored bone strength at L5 (compressive strength) and femur (bending strength) in OVX mice. The bone anabolic effect of isovitexin was demonstrated by the increased surface referent bone formation parameters, increased expression of osteogenic genes (Runx2, bone morphogenetic protein-2 and type 1 collagen) in bones, and increased serum procollagen type 1N-terminal propeptide in OVX mice and these were on a par with teriparatide. Isovitexin inhibited bone and serum sclerostin as well as the serum type I collagen cross-linked C-telopeptide in OVX mice. Isovitexin has an oral bioavailability of 14.58%. Taken together, our data show that isovitexin had a significant oral bioavailability that translated to osteoanabolic effect equivalent to teriparatide and inhibited bone resorption, which implied a durable effect over teriparatide.

Abaloparatide: A review of preclinical and clinical studies

Osteoporosis is a debilitating disease characterized by reduced bone mineral density and an increased risk of fractures. This review aims to provide a comprehensive overview of, and map current knowledge, obtained from preclinical and clinical studies of the osteoanabolic agent abaloparatide. PubMed and Embase were meticulously searched from inception to May 4, 2021.178 titles and abstracts were screened, and 57 full-text articles were assessed for inclusion. A total of 55 articles were included; 5 (9%) in vitro studies, 21 (38%) in vivo studies, and 29 (53%) clinical studies. Preclinical in vitro studies have demonstrated receptor conformation preferability, structural insights into the receptor-agonist complex, and proliferative effects of abaloparatide on osteoblasts. Preclinical studies have shown abaloparatide to be similarly effective to teriparatide using comparable doses in both ambulating mice and rats challenged by disuse. Other animal studies have reported that abaloparatide effectively mitigates or prevents bone loss from ovariectomy, orchiectomy, and glucocorticoids and improves fracture healing. The pivotal clinical study ACTIVE demonstrated 18 months of treatment with abaloparatide substantially increase bone mineral density and reduce fracture risk in post-menopausal women compared with placebo. The extension study ACTIVExtend highlighted that subsequent treatment with alendronate sustained the bone gained by abaloparatide treatment and the reduced fracture risk for up to two years. Post-hoc sub-group analyses have also supported the efficacy and safety of abaloparatide treatment independent of various baseline risk factors. In conclusion, mounting evidence from preclinical and clinical studies has uniformly reported that abaloparatide increases bone mineral density and reduces fracture risk.

Osteoanabolic therapy for osteoporosis in women

Therapy to activate bone formation is required to reverse and restore the damaged bone architecture found in women with postmenopausal osteoporosis. The osteoanabolic drugs include teriparatide, which has been available for several years, and abaloparatide and romosozumab, novel osteoanabolic drugs that have become available more recently. By stimulating bone formation, these drugs produce greater increases in bone mass and bone strength, and they do so more quickly compared to the commonly used anti-remodeling (also called antiresorptive) drugs such as bisphosphonates. In head-to-head trials, teriparatide and romosozumab reduce fracture risk more effectively than do oral bisphosphonates in women with osteoporosis and high fracture risk. Osteoanabolic drugs have little role in the prevention of bone loss during early menopause, but they have an important place in the treatment of women at very high risk of fracture or who remain at high fracture risk after a course of bisphosphonate therapy. Primarily because of the high cost of the drugs, these therapies are initiated by specialists rather than primary-care physicians in most countries. This review will present the evidence for efficacy and safety of these drugs so that clinicians may discern their appropriate use when caring for postmenopausal women with osteoporosis.

Role of bone-forming agents in the management of osteoporosis

Recent evidence confirms the superiority of osteoanabolic therapy compared to anti-remodeling drugs for rapid improvement in bone density and fracture risk reduction, providing strong justification for the use of these anabolic agents as the initial therapy in high-risk patients, to be followed by anti-remodeling therapy. This review will highlight the results of recent studies and define the current status of osteoanabolic therapy for osteoporosis.

A prebiotic, short-chain fructo-oligosaccharides promotes peak bone mass and maintains bone mass in ovariectomized rats by an osteogenic mechanism

In preclinical studies, fructooligosaccharide (FOS) showed beneficial skeletal effects but its effect on peak bone mass (PBM) and bone loss caused by estrogen (E2) deficiency has not been studied, and we set out to study these effects in rats. Short-chain (sc)-FOS had no effect on body weight, body composition, and energy metabolism of ovary intact (sham) and ovariectomized (OVX) rats. scFOS did not affect serum and urinary calcium and phosphorus levels, and on calcium absorption, although an increasing trend was noted in the sham group. Sham and OVX rats given scFOS had better skeletal parameters than their respective controls. scFOS treatment resulted in a higher bone anabolic response but had no effect on the catabolic parameters. scFOS increased serum levels of a short-chain fatty acid, butyrate which is known to have osteogenic effect. Our study for the first time demonstrates that in rats scFOS at the human equivalent dose enhances PBM and protects against E2 deficiency-induced bone loss by selective enhancement of new bone formation, and implicates butyrate in this process.

Extract and fraction of Cassia occidentalis L. (a synonym of Senna occidentalis) have osteogenic effect and prevent glucocorticoid-induced osteopenia

ETHNOPHARMACOLOGICAL RELEVANCE

Cassia occidentalis L., a synonym of Senna occidentalis (belongs to Caesalpiniaceae family) is an annual plant. Pursuing a lead from a folk practice prevalent since the late nineteenth century in Andhra Pradesh, a Southern state of India, of use of Cassia occidentalis leaf and stem for treating patients with fracture and bone diseases, we have not only confirmed its fracture healing activity but also demonstrated efficacy in preventing glucocorticoid-induced osteoporosis (GIO), the commonest form of medication-induced bone loss caused chiefly due to impairment of bone formation.

AIM OF THE STUDY

In the present work, the effects of extract and fraction of leaf and stem of Cassia occidentalis was investigated in fracture healing and GIO models of rat. The study also aimed to identify osteogenic compounds from this plant.

MATERIALS AND METHODS

Ethanolic extracts from leaf and stem of Cassia occidentalis were prepared and their efficacy tested in rat femur osteotomy (fracture healing) model. Subsequently, a butanolic fraction was prepared and osteogenic efficacy compared with the ethanolic extract, and upon finding the former to be more potent, its osteogenic effect was studied in details in GIO model. Chemical finger-printing and isolation of ten pure compounds were done to assess their osteogenic effect in rat primary osteoblast cultures.

RESULTS

Ethanolic extract of stem was more effective than the leaf extract in enhancing bone regeneration at the site of osteotomy. Further, butanolic fraction of the ethanolic extract of stem was more effective than the later in bone regeneration at the femur osteotomy site and in preventing bone loss in GIO model. The mechanism of skeletal preservation involved stimulation of new bone formation and inhibition of bone resorption. As many as six osteogenic compounds were isolated out of which apigenin-6C-glucopyranoside was most effective in vitro.

CONCLUSION

Our study found that a standardized extract of an ethanolic extract and its butanolic fraction from the stem of Cassia occidentalis has osteogenic as well as anti-resorptive effects, resulting in the protection against glucocorticoid-induced bone loss. Our results contribute towards validation of the traditional use of Cassia occidentalis in fracture healing and also suggest its beneficial use in GIO for which clinical trials are warranted.

The osteogenic effect of liraglutide involves enhanced mitochondrial biogenesis in osteoblasts

Liraglutide (Lira), a long-acting glucagon-like peptide 1 receptor (GLP1R) agonist reduces glycosylated hemoglobin in type 2 diabetes mellitus patients. Lira is reported to have bone conserving effect in ovariectomized (OVX) rats. Here, we investigated the osteoanabolic effect of Lira and studied the underlying mechanism. In established osteopenic OVX rats, Lira completely restored bone mass and strength comparable to parathyroid hormone (PTH 1-34). Body mass index normalized bone mineral density of Lira was higher than PTH. The serum levels of osteogenic surrogate pro-collagen type 1 N-terminal pro-peptide (P1NP) and surface referent bone formation parameters were comparable between Lira and PTH. GLP1R, adiponectin receptor 1 (AdipoR1) and peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC1α) levels in bones were downregulated in the OVX group but restored in the Lira group whereas PTH had no effect. In cultured osteoblasts, Lira time-dependently increased GLP1R, AdipoR1 and PGC1α expression. In osteoblasts, Lira rapidly phosphorylated AMP-dependent protein kinase (AMPK), the cellular energy sensor. Exendin 3, a selective GLP1R antagonist and PKA inhibitor H89 blocked Lira-induced increases in osteoblast differentiation, and expression levels of AdipoR1 and PGC1α. Furthermore, H89 inhibited Lira-induced phosphorylation of AMPK and dorsomorphin, an AMPK inhibitor blocked the Lira-induced increases in osteoblast differentiation and AdipoR1 and PGC1α levels. Lira increased mitochondrial number, respiratory proteins and respiration in osteoblasts in vitro and in vivo, and blocking mitochondrial respiration mitigated Lira-induced osteoblast differentiation. Taken together, our data show that Lira has a strong osteoanabolic effect which involves upregulation of mitochondrial function.

Adiponectin signaling and its role in bone metabolism

Adiponectin, the most prevalent adipo-cytokine in plasma plays critical metabolic and anti-inflammatory roles is fast emerging as an important molecular target for the treatment of metabolic disorders. Adiponectin action is critical in multiple organs including cardio-vascular system, muscle, liver, adipose tissue, brain and bone. Adiponectin signaling in bone has been a topic of active investigation lately. Human association studies and multiple mice models of gene deletion/modification failed to define a clear cause and effect of adiponectin signaling in bone. The most plausible reason could be the multimeric forms of adiponectin that display differential binding to receptors (adipoR1 and adipoR2) with cell-specific receptor variants in bone. Discovery of small molecule agonist of adipoR1 suggested a salutary role of this receptor in bone metabolism. The downstream signaling of adipoR1 in osteoblasts involves stimulation of oxidative phosphorylation leading to increased differentiation via the likely suppression of wnt inhibitor, sclerostin. On the other hand, the inflammation modulatory effect of adiponectin signaling suppresses the RANKL (receptor activator of nuclear factor κ-B ligand) - to - OPG (osteprotegerin) ratio in osteoblasts leading to the suppression of osteoclastogenic response. This review will discuss the adiponectin signaling and its role in skeletal homeostasis and critically assess whether adipoR1 could be a therapeutic target for the treatment of metabolic bone diseases.

Targeted inhibition of sclerostin for post-menopausal osteoporosis therapy: A critical assessment of the mechanism of action

Promising news in the treatment of osteoporosis is that sequestering sclerostin from circulation with antibodies stimulates robust bone formation. Pre-clinical studies on rodents and monkeys have confirmed that treatment with anti-sclerostin monoclonal antibody (Scl-Ab) increases bone mass, improves bone strength and enhances fracture repair. Clinical trials show that bone gain (anabolic effect) is transient and are primarily at central (spine and hips) than peripheral (wrist) sites. Interestingly Scl-Ab also inhibited bone resorption. Thus Scl-Ab is being regarded as the pharmacologic agent with dual properties - stimulating bone formation and decreasing bone resorption. Sclerostin neutralization transiently increases bone formation markers in post-menopausal women and like parathyroid hormone (PTH) activates osteoblasts and lining cells resulting in bone anabolic effect. However, unlike PTH, sclerostin antibody also decreases bone resorption (anti-catabolic). Although, the U.S. Food and Drug Administration have accepted the Biologics License Application for one of the monoclonal antibodies against sclerostin (romosozumab) for review, many questions remain before romosozumab can be introduced as a skeletal anabolic agent to clinical practice. For example, neutralizing sclerostin alters calcium homeostasis and increases PTH. In addition, sclerostin depletion in preclinical studies has been reported to severely compromises B cell depletion in bone marrow. We have reviewed the currently available evidences that support the use of sclerostin antibody in treating osteoporosis and compare its efficacy and mechanism of action with the currently available anabolic drug, human PTH.

Globular adiponectin reverses osteo-sarcopenia and altered body composition in ovariectomized rats

Adiponectin regulates various metabolic processes including glucose flux, lipid breakdown and insulin response. We recently reported that adiponectin receptor1 (adipoR1) activation by a small molecule reverses osteopenia in leptin receptor deficient db/db (diabetic) mice. However, the role of adiponectin in bone metabolism under the setting of post-menopausal (estrogen-deficiency) osteopenia and associated metabolic derangements has not been studied. Here, we studied the therapeutic effect of the globular form of adiponectin (gAd), which is predominantly an adipoR1 agonist, in aged ovariectomized (OVX) rats and compared it with standard-of-care anti-osteoporosis drugs. In OVX rats with established osteopenia, gAd completely restored BMD and load bearing capacity and improved bone quality. Skeletal effects of gAd were comparable to PTH (osteoanabolic) but better than alendronate (anti-catabolic). Both osteoanabolic and anti-catabolic mechanisms led to the anti-osteoporosis effect of gAd. In cultured osteoblasts and bones, gAd increased a) adipoR1 and peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC1α) expression to promote mitochondrial respiration, which likely fueled osteoblast differentiation, b) suppressed sclerostin (a wnt antagonist) in a sirtuin1-dependent manner and c) decreased receptor-activator of nuclear factor κB ligand (RANKL) to achieve its anti-catabolic effect. The OVX-induced sarcopenia and insulin resistance were also improved by gAd. We conclude that gAd has therapeutic efficacy in estrogen deficiency-induced osteoporosis, sarcopenia and insulin resistance and hold metabolic disease modifying potential in postmenopausal women.

Novel Therapies for Postmenopausal Osteoporosis

Recently discovered mechanisms have assisted in developing new therapies for osteoporosis. New classes of drugs have been developed for the treatment of postmenopausal osteoporosis. Although there have been numerous advances over the past 2 decades, the search for newer therapies continues.