Bone-forming agents in the management of osteoporosis

Amino Acid Composition of a Chum Salmon (Oncorhynchus keta) Skin Gelatin Hydrolysate and Its Antiapoptotic Effects on Etoposide-Induced Osteoblasts

A gelatin hydrolysate with a hydrolysis degree of 13.7% was generated using the skin gelatin of chum salmon (Oncorhynchus keta) and papain-catalyzed enzymatic hydrolysis. The results of analysis demonstrated that four amino acids, namely Ala, Gly, Pro, and 4-Hyp, were the most abundant in the obtained gelatin hydrolysate with measured molar percentages ranging from 7.2% to 35.4%; more importantly, the four amino acids accounted for 2/3 of the total measured amino acids. However, two amino acids, Cys and Tyr, were not detected in the generated gelatin hydrolysate. The experimental results indicated that the gelatin hydrolysate at a dose of 50 µg/mL could combat etoposide-induced apoptosis in human fetal osteoblasts (hFOB 1.19 cells), causing a decrease in the total apoptotic cells from 31.6% to 13.6% (via apoptotic prevention) or 13.3% to 11.8% (via apoptotic reversal). Meanwhile, the osteoblasts exposed to the gelatin hydrolysate showed expression changes for 157 genes (expression folds > 1.5-fold), among which JNKK, JNK1, and JNK3 were from the JNK family with a 1.5-2.7-fold downregulated expression. Furthermore, the protein expressions of JNKK, JNK1, JNK3, and Bax in the treated osteoblasts showed a 1.25-1.41 fold down-regulation, whereas JNK2 expression was not detected in the osteoblasts. It is thus suggested that gelatin hydrolysate is rich in the four amino acids and has an in vitro antiapoptotic effect on etoposide-stimulated osteoblasts via mitochondrial-mediated JNKK/JNK(1,3)/Bax downregulation.

Short-term intermittent parathyroid hormone (1-34) administration increased angiogenesis and matrix metalloproteinase 9 in femora of mature and middle-aged C57BL/6 mice

NEW FINDINGS

What is the central question of this study? We sought to assess the effects of intermittent parathyroid hormone (1-34) administration on bone angiogenesis, the redistribution of bone marrow blood vessels, and matrix metalloproteinase 9 as a function of advancing age in mice. What is the main finding and its importance? Short-term (i.e. 10 days) intermittent parathyroid hormone (1-34) administration increased the number of small (≤29-µm-diameter) bone marrow blood vessels and augmented matrix metalloproteinase 9. These changes occurred before alterations in trabecular bone. Given the rapid response in bone angiogenesis, this investigation highlights the impact of intermittent parathyroid hormone (1-34) administration on the bone vascular network.

ABSTRACT

Intermittent parathyroid hormone (PTH) administration augments bone, stimulates the production of matrix metalloproteinase 9 (Mmp9) and relocates bone marrow blood vessels closer to osteoid seams. Discrepancies exist, however, regarding bone angiogenesis. Given that Mmp9 participates in cellular homing and migration, it might aid in blood vessel relocation. We examined the influence of short-term intermittent PTH administration on angiogenesis, Mmp9 secretion and the distance between blood vessels and bone. Mature (6- to 8-month-old) and middle-aged (10- to 12-month-old) male and female C57BL/6 mice were divided into three groups: control (CON), and 5 (5dPTH) and 10 days (10dPTH) of intermittent PTH administration. Mice were given PBS (50 µl day^-1 ) or PTH(1-34) (43 µg kg^-1  day^-1 ). Frontal sections (5 µm thick) of the right distal femoral metaphysis were triple-immunolabelled to identify endothelial cells (anti-CD31), vascular smooth muscle cells (anti-αSMA) and Mmp9 (anti-Mmp9). Vascular density, Mmp9 density, area and localization, and blood vessel distance from bone were analysed. Blood vessels were analysed according to diameter: 1-29, 30-100 and 101-200 µm. Trabecular bone microarchitecture and bone static and dynamic properties were assessed. No main effects of age were observed for any variable. The density of CD31-labelled blood vessels 1-29 and 30-100 µm in diameter was higher (P < 0.05) and tended (P = 0.055) to be higher, respectively, in 10dPTH versus 5dPTH and CON. Mmp9 was augmented (P < 0.05) in 10dPTH versus the other groups. Mmp9 was closer (P < 0.05) to blood vessels 1-29 µm in diameter and furthest (P < 0.05) from bone. In conclusion, bone angiogenesis occurred by day 10 of intermittent PTH administration, coinciding with augmented Mmp9 secretion near the smallest blood vessels (1-29 µm in diameter).

The Growth Proliferation, Apoptotic Prevention, and Differentiation Induction of the Gelatin Hydrolysates from Three Sources to Human Fetal Osteoblasts (hFOB 1.19 Cells)

Gelatins from the skin of bovine, porcine, and tilapia were hydrolyzed to three degrees of hydrolysis (DH) by alcalase, neutrase, and papain, respectively. These hydrolysates at 0.02⁻0.1 g/L promoted the growth of human fetal osteoblasts by 101.4⁻135.7%, while higher DH or using papain and tilapia gelatins resulted in higher proliferation. The hydrolysates from porcine and tilapia gelatins at 0.05 g/L prevented induced apoptosis (decreasing total apoptotic proportions from 28.4% or 35.2% to 10.3⁻17.5% or 16.0⁻23.6%), and had differentiation induction (increasing alkaline phosphatase activity by 126.9⁻246.7% in early differentiation stage, or enhancing osteocalcin production by 4.1⁻22.5% in later differentiation stage). These hydrolysates had a similar amino acid profile; however, tilapia gelatin hydrolysates by papain with DH 15.4% mostly displayed higher activity than others. Tilapia gelatin hydrolysate could up-regulate β-catenin, Wnt 3a, Wnt 10b, cyclin D1, and c-Myc expression at mRNA levels by 1.11⁻3.60 folds, but down-regulate GSK 3β expression by 0.98 fold. Of note, β-catenin in total cellular and nuclear protein was up-regulated by 1.14⁻1.16 folds but unchanged in cytoplasmic protein, Wnt 10b, cyclin D1, and c-Myc expression were up-regulated by 1.27⁻1.95 folds, whilst GSK 3β expression was down-regulated by 0.87 fold. Activation of Wnt/β-catenin pathway is suggested to mediate cell proliferation and differentiation.

Intermittent PTH 1-34 administration improves the marrow microenvironment and endothelium-dependent vasodilation in bone arteries of aged rats

Inflammation coincides with diminished marrow function, vasodilation of blood vessels, and bone mass. Intermittent parathyroid hormone (PTH) administration independently improves marrow and vascular function, potentially impacting bone accrual. Currently, the influence of marrow and intermittent PTH administration on aged bone blood vessels has not been examined. Vasodilation of the femoral principal nutrient artery (PNA) was assessed in the presence and absence of marrow. Furthermore, we determined the influence of PTH 1-34 on 1) endothelium-dependent vasodilation and signaling pathways [i.e., nitric oxide (NO) and prostacyclin (PGI₂)], 2) endothelium-independent vasodilation, 3) cytokine production by marrow cells, and 4) bone microarchitecture and bone static and dynamic properties. Young (4-6 mo) and old (22-24 mo) male Fischer-344 rats were treated with PTH 1-34 or a vehicle for 2 wk. In the absence and presence of marrow, femoral PNAs were given cumulative doses of acetylcholine, with and without the NO and PGI₂ blockers, and diethylamine NONOate. Marrow-derived cytokines and bone parameters in the distal femur were assessed. Exposure to marrow diminished endothelium-dependent vasodilation in young rats. Reduced bone volume and NO-mediated vasodilation occurred with old age and were partially reversed with PTH. Additionally, PTH treatment in old rats restored endothelium-dependent vasodilation in the presence of marrow and augmented IL-10, an anti-inflammatory cytokine. Endothelium-independent vasodilation was unaltered, and PTH treatment reduced osteoid surfaces in old rats. In conclusion, the marrow microenvironment reduced vascular function in young rats, and PTH treatment improved the marrow microenvironment and vasodilation with age. NEW & NOTEWORTHY This study investigated the influence of the marrow microenvironment on bone vascular function in young and old rats. An inflamed marrow microenvironment may reduce vasodilator capacity of bone blood vessels, diminishing delivery of blood flow to the skeleton. In young rats, the presence of the marrow reduced vasodilation in the femoral principal nutrient artery (PNA). However, intermittent parathyroid hormone administration (i.e., a treatment for osteoporosis) improved the marrow microenvironment and vasodilator capacity in old PNAs.

PTH coatings on titanium surfaces improved osteogenic integration by increasing expression levels of BMP-2/Runx2/Osterix

The aim of this experiment was to assemble parathyroid hormone (PTH) coatings on titanium surfaces and evaluate the effect on implant osseointegration.

Demineralization-remineralization dynamics in teeth and bone

Biomineralization is a dynamic, complex, lifelong process by which living organisms control precipitations of inorganic nanocrystals within organic matrices to form unique hybrid biological tissues, for example, enamel, dentin, cementum, and bone. Understanding the process of mineral deposition is important for the development of treatments for mineralization-related diseases and also for the innovation and development of scaffolds. This review provides a thorough overview of the up-to-date information on the theories describing the possible mechanisms and the factors implicated as agonists and antagonists of mineralization. Then, the role of calcium and phosphate ions in the maintenance of teeth and bone health is described. Throughout the life, teeth and bone are at risk of demineralization, with particular emphasis on teeth, due to their anatomical arrangement and location. Teeth are exposed to food, drink, and the microbiota of the mouth; therefore, they have developed a high resistance to localized demineralization that is unmatched by bone. The mechanisms by which demineralization-remineralization process occurs in both teeth and bone and the new therapies/technologies that reverse demineralization or boost remineralization are also scrupulously discussed. Technologies discussed include composites with nano- and micron-sized inorganic minerals that can mimic mechanical properties of the tooth and bone in addition to promoting more natural repair of surrounding tissues. Turning these new technologies to products and practices would improve health care worldwide.

Teriparatide use during an economic crisis: baseline data from the Greek cohort of the Extended Forsteo Observational Study (ExFOS)

BACKGROUND

The Extended Forsteo Observational Study (ExFOS) is a multinational, non-interventional, prospective, observational study that aims to provide real-life data on patients with osteoporosis treated with teriparatide for up to 24 months. It includes the new indications of osteoporosis in men and glucocorticoid-induced osteoporosis (GIOP). We describe the Greek subpopulation enrolled in this study and compare it with a similar cohort from the previous European Forsteo Observational Study (EFOS).

METHODS

Baseline data were collected from the Greek cohort of ExFOS. Data included demographic characteristics, medical and osteoporosis history, disease status, prior use of medications, back pain and quality of life.

RESULTS

Baseline data for 439 patients, enrolled at 31 sites, indicated the majority of patients were females (92.3%), elderly [mean (standard deviation; SD) age 70.1 (9.8) years] and slightly overweight [mean (SD) body mass index 26.7 (4.3) kg/m(2)], with very low bone mineral density (mean T-score <-3 in lumbar spine or total hip) and at least one previous fracture (55.1% of patients). Of the 439 patients, 19.8% were osteoporosis treatment naïve, 88.4% had experienced back pain during the previous 12 months, 68.1% had experienced back pain at least fairly often during the previous month and 50.9% reported moderate to severe limitation of activities due to back pain, with a mean (SD) of 4.2 (7.7) days spent in bed because of back pain during the previous month. Most baseline characteristics were numerically similar between the female ExFOS and EFOS cohorts; however, the rate of enrolment was faster in ExFOS (by approximately 45%) and a history of fracture was recorded in 53.8% of female patients in ExFOS versus 74.5% in EFOS.

CONCLUSIONS

Greek patients prescribed teriparatide in ExFOS had severe osteoporosis with a high risk of fractures and back pain. Female patients shared similarities with EFOS counterparts, reflecting a constant prescribing profile for use of teriparatide, although a noticeable difference in fracture history between the two study cohorts may indicate a change towards prescribing in less severely affected patients. The economic crisis in Greece did not appear to affect patient enrolment. Data are interpreted in the context of an observational setting.

Vasodilation to PTH (1-84) in bone arteries is dependent upon the vascular endothelium and is mediated partially via VEGF signaling

BACKGROUND

Intermittent PTH administration directly stimulates osteoblasts; however, mechanisms of bone accrual that are independent of the direct actions on osteoblasts may be under-appreciated. Our aims were to decipher (1) whether PTH 1-84 augments vasodilation of the femoral principal nutrient artery (PNA), (2) whether 15 days of intermittent PTH 1-84 augments endothelium-dependent and/or -independent vasodilation of the femoral PNA, and (3) the signaling mechanisms involved.

METHODS

Experiment 1: Femoral PNAs from male Wistar rats were exposed to cumulative doses of PTH 1-84 with and without an anti-vascular endothelial growth factor antibody and/or the endothelial NO synthase inhibitor l-NAME. Experiment 2: Male Wistar rats were administered PTH and/or the anti-VEGF antibody for 2 weeks. Subsequently, endothelium-dependent vasodilation to acetylcholine and endothelium-independent vasodilation to sodium nitroprusside were assessed. In addition, endothelium-dependent signaling pathways were analyzed by use of l-NAME and/or and the cyclooxygenase inhibitor indomethacin.

RESULTS

Cumulative doses of PTH 1-84 induced vasodilation of the femoral PNA, which was reduced by 38% and 87% with the anti-VEGF antibody and l-NAME, respectively. Secondly, 2 weeks of intermittent PTH 1-84 administration doubled trabecular bone volume, augmented bone formation parameters and reduced osteoclast activity. In addition, PTH enhanced endothelium-dependent vasodilation via up-regulation of NO. Co-administration of the anti-VEGF antibody (1) inhibited the PTH-induced increase in bone volume and remodeling parameters and (2) blunted the augmented vasodilator responsiveness of the PNA. Finally, endothelium-dependent vasodilation in PTH-treated rats was highly correlated with trabecular bone volume.

CONCLUSION

As hypothesized, PTH enhanced endothelium-dependent vasodilation of the femoral PNA via augmented NO production and was mediated partially through VEGF signaling. Further, vasodilation to PTH appears independent of vascular smooth muscle cell participation. More importantly, the strong association between vasodilation and bone volume suggests that bone arteriolar function is critical for PTH-induced bone anabolism.

Teriparatide - Indications beyond osteoporosis

Osteoporosis is a condition of impaired bone strength that results in an increased risk of fracture. The current and most popular pharmacological options for the treatment of osteoporosis include antiresorptive therapy, in particular, oral bisphosphonates (alendronate, risedronate, ibandronate). Anabolic agents like teriparatide have widened our therapeutic options. They act by directly stimulating bone formation and improving bone mass quantity and quality. Two forms of recombinant human parathyroid hormone (PTH) are available : full-length PTH (PTH 1-84; approved in the EU only) and the 1-34 N-terminal active fragment of PTH (teriparatide, US FDA approved). This review aims to discuss the benefits of teriparatide beyond the currently licensed indications like fracture healing, dental stability, osteonecrosis of jaw, hypoparathyroidism, and hypocalcemia.

Sequential therapy in the treatment of osteoporosis

OBJECTIVE

To review the clinical data in the sequential use of antiresorptive and anabolic agents for the treatment of osteoporosis.

METHODS

The US National Library of Medicine was used to obtain the relevant information on osteoporosis management involving antiresorptive and anabolic bone agents.

RESULTS

Antiresorptive and anabolic therapies are the two main types of medications approved for osteoporosis treatment. The efficacy of these agents in fracture risk reduction is well established. Many patients with osteoporosis are first treated with an antiresorptive agent, most commonly a bisphosphonate. Osteoporotic patients who fail to respond to antiresorptive therapy or patients with severe osteoporosis may require anabolic therapy at some point during their disease. Recombinant human parathyroid hormone (PTH) is an anabolic agent with proven benefits on bone strength. Sequential therapy using PTH after antiresorptive agents has been found beneficial for bone health. Recent research suggests that the speed and magnitude of PTH effect can differ, depending on the previous antiresorptive therapy. Upon PTH cessation, subsequent antiresorptive therapy may help maintain or increase gains in bone mass.

CONCLUSIONS

Although further research is needed to determine the long-term significance of prior antiresorptive therapies and their differing effects on fracture risk reduction with subsequent PTH therapy, patients with severe osteoporosis should be considered for this treatment option, regardless of prior osteoporosis treatment.

The use of PTH in the treatment of osteoporosis

Anabolic drugs have recently widened therapeutic options in osteoporosis treatment, as they influence processes associated with bone formation to a greater extent and earlier than bone reabsortion. They positively affect a number of skeletal properties besides bone density, as intermittent administration of parathyroid hormone (PTH) results in an increase in the number and activity of osteoblasts leading to an increase in bone mass and improvement in skeletal architecture at both the trabecular and cortical bone. Human recombinant parathyroid hormone (hrPTH 1-84) and human recombinant PTH peptide 1-34 (teriparatide) belong to this group. The objective of this paper is to review PTH actions, benefits and adverse effects, action on biochemical markers, combination therapy with antiresorptive agents, impact of antiresorptive therapy prior to anabolic treatment, sequential treatment, and effect on glucocorticoid-induced osteoporosis.