Intermittent administration of PTH for the treatment of inflammatory bone loss does not enhance entheseal pathological new bone formation.

OBJECTIVE: To investigate the effect of intermittent parathyroid hormone (iPTH) administration on pathological new bone formation during treatment of ankylosing spondylitis-related osteoporosis. METHODS: Animal models with pathological bone formation caused by hypothetical AS pathogenesis received treatment with iPTH. We determined the effects of iPTH on bone loss and the formation of pathological new bone with micro-computed tomography (micro-CT) and histological examination. In addition, the tamoxifen-inducible conditional knockout mice (CAGGCre-ERTM; PTHflox/flox, PTH-/-) was established to delete PTH and investigate the effect of endogenous PTH on pathological new bone formation. RESULTS: iPTH treatment significantly improved trabecular bone mass in the modified collagen-induced arthritis (m-CIA) model and unbalanced mechanical loading models. Meanwhile, iPTH treatment did not enhance pathological new bone formation in all types of animal models. Endogenous PTH deficiency had no effects on pathological new bone formation in unbalanced mechanical loading models. CONCLUSION: Experimental animal models of AS treated with iPTH show improvement in trabecular bone density, but not entheseal pathological bone formation，indicating it may be a potential treatment for inflammatory bone loss does in AS.

NACA and LRP6 Are Part of a Common Genetic Pathway Necessary for Full Anabolic Response to Intermittent PTH.

PTH induces phosphorylation of the transcriptional coregulator NACA on serine 99 through Gαs and PKA. This leads to nuclear translocation of NACA and expression of the target gene Lrp6, encoding a coreceptor of the PTH receptor (PTH1R) necessary for full anabolic response to intermittent PTH (iPTH) treatment. We hypothesized that maintaining enough functional PTH1R/LRP6 coreceptor complexes at the plasma membrane through NACA-dependent Lrp6 transcription is important to ensure maximal response to iPTH. To test this model, we generated compound heterozygous mice in which one allele each of Naca and Lrp6 is inactivated in osteoblasts and osteocytes, using a knock-in strain with a Naca99 Ser-to-Ala mutation and an Lrp6 floxed strain (test genotype: Naca99S/A; Lrp6+/fl;OCN-Cre). Four-month-old females were injected with vehicle or 100 µg/kg PTH(1-34) once daily, 5 days a week for 4 weeks. Control mice showed significant increases in vertebral trabecular bone mass and biomechanical properties that were abolished in compound heterozygotes. Lrp6 expression was reduced in compound heterozygotes vs. controls. The iPTH treatment increased Alpl and Col1a1 mRNA levels in the control but not in the test group. These results confirm that NACA and LRP6 form part of a common genetic pathway that is necessary for the full anabolic effect of iPTH.

Intermittent parathyroid hormone promotes cementogenesis via ephrinB2-EPHB4 forward signaling.

Intermittent parathyroid hormone (PTH) promotes periodontal repair, but the underlying mechanisms remained unclear. Recent studies found that ephrinB2-EPHB4 forward signaling mediated the anabolic effect of PTH in bone homeostasis. Considering the similarities between cementum and bone, we aimed to examine the therapeutic effect of PTH on resorbed roots and explore the role of forward signaling in this process. In vivo experiments showed that intermittent PTH significantly accelerated the regeneration of root resorption and promoted expression of EPHB4 and ephrinB2. When the signaling was blocked, the resorption repair was also delayed. In vitro studies showed that intermittent PTH promoted the expression of EPHB4 and ephrinB2 in OCCM-30 cells. The effects of PTH on the mineralization capacity of OCCM-30 cells was mediated through the ephrinB2-EPHB4 forward signaling. These results support the premise that the anabolic effects of intermittent PTH on the regeneration of root resorption is via the ephrinB2-EPHB4 forward signaling pathway.

Impact of periprocedural subcutaneous parathyroid hormone on control of hypocalcaemia in APS-1/APECED patients undergoing invasive procedures.

CONTEXT: The monogenic disorder autoimmune polyendocrine syndrome type 1 (APS-1) or autoimmune polyendocrinopathy-candidiasis-ectodermal dystrophy (APECED) manifests frequently with hypoparathyroidism, which requires treatment with oral supplementation with calcium and active vitamin D analogs. The majority of APS-1/APECED patients also suffer from intestinal malabsorption, which complicates the management of hypoparathyroidism and may lead to refractory severe hypocalcaemia. In such situations, reliance on intravenous calcium carries a high risk of nephrocalcinosis and renal damage. METHODS: Here, we report our experience of periprocedural subcutaneous administration of recombinant human parathyroid hormone (rhPTH 1-34) in APS-1/APECED patients. Serum calcium was measured up to five times within the 36-hour period starting the evening before the scheduled procedure and ending the morning following the procedure. RESULTS: Twenty-seven APS-1/APECED patients with hypoparathyroidism (aged 4-67 years) underwent 31 invasive gastrointestinal and/or pulmonary procedures. The patients received an average rhPTH1-34 dose of 9.6 ± 1.4 µg by subcutaneous injection. 92% of the adults and 54% of children in our cohort had evidence of nephrocalcinosis. Mean calcium levels remained stable and ranged from 2.06 to 2.17 mmol/L with minimal fluctuation. None of our patients experienced periprocedural adverse events connected with hypocalcaemia. CONCLUSION: rhPTH 1-34 is an alternative to conventional therapy in patients with APS-1/APECED and hypoparathyroidism undergoing invasive procedures. Subcutaneous PTH1-34 given directly before and after procedures resulted in well-controlled serum calcium levels maintained in the low-normal range and avoided the need for intravenous calcium which may contribute to renal calcifications and tubular damage.

Intermittent PTH Administration Increases Bone-Specific Blood Vessels and Surrounding Stromal Cells in Murine Long Bones.

To verify whether PTH acts on bone-specific blood vessels and on cells surrounding these blood vessels, 6-week-old male mice were subjected to vehicle (control group) or hPTH [1-34] (20 µg/kg/day, PTH group) injections for 2 weeks. Femoral metaphyses were used for histochemical and immunohistochemical studies. In control metaphyses, endomucin-positive blood vessels were abundant, but αSMA-reactive blood vessels were scarce. In the PTH-administered mice, the lumen of endomucin-positive blood vessels was markedly enlarged. Moreover, many αSMA-positive cells were evident near the blood vessels, and seemed to derive from those vessels. These αSMA-positive cells neighboring the blood vessels showed features of mesenchymal stromal cells, such as immunopositivity for c-kit and tissue nonspecific alkaline phosphatase (TNALP). Thus, PTH administration increased the population of perivascular/stromal cells positive for αSMA and c-kit, which were likely committed to the osteoblastic lineage. To understand the cellular events that led to increased numbers and size of bone-specific blood vessels, we performed immunohistochemical studies for PTH/PTHrP receptor and VEGF. After PTH administration, PTH/PTHrP receptor, VEGF and its receptor flk-1 were consistently identified in both osteoblasts and blood vessels (endothelial cells and surrounding perivascular cells). Our findings suggest that exogenous PTH increases the number and size of bone-specific blood vessels while fostering perivascular/stromal cells positive for αSMA/TNALP/c-kit.

Discovery of a Long-Acting Parathyroid Hormone 1-34 Analogue to Treat Hypoparathyroidism.

Hypoparathyroidism (HP) is a rare disease with clinical manifestations of hypocalcemia and hyperphosphatemia, resulting from deficient or absent parathyroid hormone (PTH) secretion. Conventional treatment for patients with HP involves extensive calcium and vitamin D supplementation. In 2015, PTH1-84 was approved by the United States Food and Drug Administration as an adjunct for HP patients who cannot be well-controlled on conventional treatment. However, PTH1-84 therapy requires a daily injection, leading to poor patient compliance. The purpose of this study was to develop a long-acting PTH1-34 analogue by increasing its affinity to albumin. Three PTH1-34 variants were generated by substituting two of the three lysine (Lys) residues with arginine, reserving a single Lys as the modification site in each sequence. A series of side chains, containing fatty acid, deoxycholic acid, or biotin groups, were synthesized to modify these PTH1-34 variants by using a solid-liquid phase synthesis approach. In vitro bioactivity and albumin affinity tests were used to screen these new PTH1-34 analogues. Finally, Lys27-AAPC was selected from 69 synthesized analogues as a candidate therapeutic compound because it retained potency and exhibited a high albumin-binding capacity. In pharmacodynamic experiments, Lys27-AAPC demonstrated enhanced and prolonged efficacy in serum calcium elevating relative to PTH1-84. Moreover, a lyophilized powder for injection containing Lys27-AAPC was developed for further testing and represented a potential long-acting HP treatment.

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).

Bone-Specific Drug Delivery for Osteoporosis and Rare Skeletal Disorders.

PURPOSE OF REVIEW: The skeletal system provides an important role to support body structure and protect organs. The complexity of its architecture and components makes it challenging to deliver the right amount of the drug into bone regions, particularly avascular cartilage lesions. In this review, we describe the recent advance of bone-targeting methods using bisphosphonates, polymeric oligopeptides, and nanoparticles on osteoporosis and rare skeletal diseases. RECENT FINDINGS: Hydroxyapatite (HA), a calcium phosphate with the formula Ca10(PO4)6(OH)2, is a primary matrix of bone mineral that includes a high concentration of positively charged calcium ion and is found only in the bone. This unique feature makes HA a general targeting moiety to the entire skeletal system. We have applied bone-targeting strategy using acidic amino acid oligopeptides into lysosomal enzymes, demonstrating the effects of bone-targeting enzyme replacement therapy and gene therapy on bone and cartilage lesions in inherited skeletal disorders. Virus or no-virus gene therapy using techniques of engineered capsid or nanomedicine has been studied preclinically for skeletal diseases. Efficient drug delivery into bone lesions remains an unmet challenge in clinical practice. Bone-targeting therapies based on gene transfer can be potential as new candidates for skeletal diseases.

Calcimimetics maintain bone turnover in uremic rats despite the concomitant decrease in parathyroid hormone concentration.

Calcimimetics decrease parathyroid hormone (PTH) secretion in patients with secondary hyperparathyroidism. The decrease in PTH should cause a reduction in bone turnover; however, the direct effect of calcimimetics on bone cells, which express the calcium-sensing receptor (CaSR), has not been defined. In this study, we evaluated the direct bone effects of CaSR activation by a calcimimetic (AMG 641) in vitro and in vivo. To create a PTH "clamp," total parathyroidectomy was performed in rats with and without uremia induced by 5/6 nephrectomy, followed by a continuous subcutaneous infusion of PTH. Animals were then treated with either the calcimimetic or vehicle. Calcimimetic administration increased osteoblast number and osteoid volume in normal rats under a PTH clamp. In uremic rats, the elevated PTH concentration led to reduced bone volume and increased bone turnover, and calcimimetic administration decreased plasma PTH. In uremic rats exposed to PTH at 6-fold the usual replacement dose, calcimimetic administration increased osteoblast number, osteoid surface, and bone formation. A 9-fold higher dose of PTH caused an increase in bone turnover that was not altered by the administration of calcimimetic. In an osteosarcoma cell line, the calcimimetic induced Erk1/2 phosphorylation and the expression of osteoblast genes. The addition of a calcilytic resulted in the opposite effect. Moreover, the calcimimetic promoted the osteogenic differentiation and mineralization of human bone marrow mesenchymal stem cells in vitro. Thus, calcimimetic administration has a direct anabolic effect on bone that counteracts the decrease in PTH levels.

Sequential Treatment with Eldecalcitol After PTH Improves Bone Mechanical Properties of Lumbar Spine and Femur in Aged Ovariectomized Rats.

Parathyroid hormone (PTH) analogs have a powerful anabolic effect on bone and are used in the treatment of patients with severe osteoporosis. However, there are limitations to how long they can be safely administered. Withdrawal of PTH results in the cancelation of its effects, necessitating subsequent treatment to maintain the bone quantity and quality. This study assessed the effects of Eldecalcitol (ELD), an active vitamin D3 derivative, after PTH in estrogen-deficient osteoporotic rats. Six-month-old female rats were ovariectomized, and PTH administration was started 7 weeks later. After 4 weeks of PTH treatment, the animals were divided into three groups and either continued to receive PTH (PTH-PTH), or were switched to ELD (PTH-ELD) or vehicle (PTH-Veh) for an additional 4 weeks. In the femur, increased BMD by 4 weeks treatment of PTH was significantly reduced in PTH-Veh but not in PTH-PTH and PTH-ELD. The same tendency was observed in the lumbar vertebrae. MicroCT imaging and histomorphometry analysis revealed that the favorable bone structure changes by PTH administration were also maintained in the femurs and tibias of the PTH-PTH and PTH-ELD groups. Increased bone strength by 4-week treatment of PTH in lumber also maintained in PTH-ELD. Furthermore, minimodeling was observed in the PTH-ELD group. These results demonstrate that treatment with ELD sequentially following PTH prevented the bone quantity and strength reduction that accompanies PTH withdrawal in estrogen-deficient rats.

Single-dose local administration of parathyroid hormone (1-34, PTH) with ß-tricalcium phosphate/collagen (ß-TCP/COL) enhances bone defect healing in ovariectomized rats.

Parathyroid hormone (1-34, PTH) combined ß-tricalcium phosphate (ß-TCP) achieves stable bone regeneration without cell transplantation in previous studies. Recently, with the development of tissue engineering slow release technology, PTH used locally to promote bone defect healing become possible. This study by virtue of collagen with a combination of drugs and has a slow release properties, and investigated bone regeneration by ß-TCP/collagen (ß-TCP/COL) with the single local administration of PTH. After the creation of a rodent critical-sized femoral metaphyseal bone defect, ß-TCP/COL was prepared by mixing sieved granules of ß-TCP and atelocollagen for medical use, then ß-TCP/COL with dripped PTH solution (1.0 µg) was implanted into the defect of OVX rats until death at 4 and 8 weeks. The defected area in distal femurs of rats was harvested for evaluation by histology, micro-CT, and biomechanics. The results of our study show that single-dose local administration of PTH combined local usage of ß-TCP/COL can increase the healing of defects in OVX rats. Furthermore, treatments with single-dose local administration of PTH and ß-TCP/COL showed a stronger effect on accelerating the local bone formation than ß-TCP/COL used alone. The results from our study demonstrate that combination of single-dose local administration of PTH and ß-TCP/COL had an additive effect on local bone formation in osteoporosis rats.

Effects of Intermittent Parathyroid Hormone 1-34 Administration on Circulating Mesenchymal Stem Cells in Postmenopausal Osteoporotic Women.

BACKGROUND Intermittent parathyroid hormone (PTH) 1-34 administration stimulates osteogenesis and increases bone marrow mesenchymal stem cell (MSC) density; however, its effect on the circulating MSCs is unknown. This study aimed to examine the effect of intermittent PTH 1-34 administration on circulating MSCs in the peripheral blood of postmenopausal osteoporotic women. MATERIAL AND METHODS Fifty-four postmenopausal osteoporotic women at high risk of fracture were enrolled and administered either teriparatide (PTH 1-34) or alendronate for 12 months. Whole blood samples were obtained at baseline, 1, 3, 6, and 12 months after initiation of treatment. Flow cytometry analyses were performed to identify circulating MSCs (CD73+, CD90+, CD105+, CD34-, and CD45-). Serum markers of bone formation, bone resorption, as well as bone mineral density (BMD) were serially measured. Circulating MSCs were isolated from peripheral blood of teriparatide treated women and cultured in osteogenic medium to examine their osteogenic differentiation potential. RESULTS Teriparatide treatment increased circulating MSCs to 141±96% (P<0.001) by month 1, persisting until month 12; this increase was positively associated with increases in bone formation and bone resorption biomarkers (at month 6) and spine BMD (at month 12). Furthermore, intermittent PTH 1-34 administration promoted in vitro osteogenic differentiation of circulating MSCs, evident from increased alkaline phosphatase (ALP) activity, ALP-expressing cell density, calcium deposition, and Runx-2, OSX, COL 1a1, and osteocalcin mRNA upregulation. CONCLUSIONS Intermittent PTH 1-34 administration increased circulating MSC density in women with postmenopausal osteoporosis and enhanced in vitro osteogenic differentiation potential of these cells.

Hydroxyapatite nanorods loaded with parathyroid hormone (PTH) synergistically enhance the net formative effect of PTH anabolic therapy.

Parathyroid hormone (PTH) has been a major contributor to the anabolic therapy for osteoporosis, but its delivery to bone without losing activity and avoiding adverse local effects remain a challenge. Being the natural component of bone, use of hydroxyapatite for this purpose brings a major breakthrough in synergistic anabolism. This study focuses on synthesis, characterization and evaluation of in vitro and in vivo efficacy of PTH (1-34) adsorbed hydroxyapatite nanocarrier for synergistic enhancement in the anabolic activity of PTH for bone regeneration. The negative zeta potential of this nanocarrier facilitated its affinity to the Ca2+ rich bone tissue and solubilization at low pH enhanced specific delivery of PTH to the resorption pits in osteoporotic bone. In this process, PTH retained its anabolic effect and at the same time an increase in bone mineral content indicated enhancement of the net formative effect of the PTH anabolic therapy.

Interaction among Calcium Diet Content, PTH (1-34) Treatment and Balance of Bone Homeostasis in Rat Model: The Trabecular Bone as Keystone.

The present study is the second step (concerning normal diet restoration) of the our previous study (concerning the calcium-free diet) to determine whether normal diet restoration, with/without concomitant PTH (1-34) administration, can influence amounts and deposition sites of the total bone mass. Histomorphometric evaluations and immunohistochemical analysis for Sclerostin expression were conducted on the vertebral bodies and femurs in the rat model. The final goals are (i) to define timing and manners of bone mass changes when calcium is restored to the diet, (ii) to analyze the different involvement of the two bony architectures having different metabolism (i.e., trabecular versus cortical bone), and (iii) to verify the eventual role of PTH (1-34) administration. Results evidenced the greater involvement of the trabecular bone with respect to the cortical bone, in response to different levels of calcium content in the diet, and the effect of PTH, mostly in the recovery of trabecular bony architecture. The main findings emerged from the present study are (i) the importance of the interplay between mineral homeostasis and skeletal homeostasis in modulating and guiding bone's response to dietary/metabolic alterations and (ii) the evidence that the more involved bony architecture is the trabecular bone, the most susceptible to the dynamical balance of the two homeostases.

Differences in accelerated tooth movement promoted by recombinant human parathyroid hormone after mandibular ramus osteotomy.

INTRODUCTION: This study investigated the effects of different doses of parathyroid hormone (PTH) on orthodontic tooth movement after mandibular ramus osteotomy and the associated dose-response relationship. METHODS: One-hundred twenty rabbits were divided into 2 experimental groups (A and B) and 2 control groups (control group and negative control group). An experimental model of mandibular ramus osteotomy with installation of an orthodontic tooth movement device was established in groups A and B and the control group. After surgery, groups A and B received intermittent subcutaneous injections of PTH, 20 and 40 µg/kg, respectively, and the control group received injections of normal saline solution. The negative control group underwent installation of the orthodontic tooth movement device without mandibular ramus osteotomy and received normal saline solution after surgery. Changes in expression of RANKL and RUNX2 in the periodontal tissues of the first molars were evaluated by means of immunohistochemical analysis and quantitative fluorescence polymerase chain reaction. RESULTS: Movement of the first molars was more rapid in group B than in group A in the 21 days after surgery. Significantly higher RANKL mRNA levels and lower RUNX2 mRNA levels were detected on the compression side of the periodontal tissues in groups A and B than in the control groups. There was a significant difference in RANKL and RUNX2 expression levels between group B and the control groups at all time points. CONCLUSIONS: Mandibular ramus osteotomy combined with high-dose PTH can increase catabolism on the compressed periodontal tissues, thereby accelerating remodeling of periodontal bone and promoting orthodontic tooth movement after surgery.

In vivo and in vitro effects of PTH1-34 on osteogenic and adipogenic differentiation of human bone marrow-derived mesenchymal stem cells through regulating microRNA-155.

This study aimed to investigate the effect of parathyroid hormone (PTH1-34) on osteogenic and adipogenic differentiation of hBMSCs by the regulation of miR-155. A total of 36 adult volunteers were selected in this study. Effects of PTH1-34 on the proliferation of hBMSCs and miR-155 expression were investigated using a MTT assay. The hBMSCs were divided into blank, PTH1-34, miR-155 mimic, miR-155 mimic negative control (NC), miR-155 inhibitor, miR-155 inhibitor NC, PTH1-34 + miR-155 mimic, PTH1-34 + miR-155 inhibitor, and NPS R-568 groups. Postmenopausal osteoporosis (PMOP) mouse models were established by ovariectomy (OVX) and divided into ten groups. The RT-qPCR and Western blotting assay were carried out to detect the expression of osteogenesis/adipogenic-related genes and miR-155, and osteogenesis/adipogenic-related proteins. PTH1-34 could promote hBMSCs proliferation and inhibit miR-155 expression in a dose-dependent manner. Compared with the blank control group, expressions of Runx2, and BSP was up-regulated in the PTH1-34 and miR-155 inhibitor groups, while expressions of miR-155, PPAR-γ, lipoprotein lipase (LPL), fatty acid binding protein 4 (Fabp4), adiponectin, and CCAAT/enhancer binding protein α (C/EBPα) were down-regulated. In the in vivo experiment, compared with the OVX group, the BMD and expressions of Runx2 and BSP was up-regulated in the PTH1-34, miR-155 inhibitor, and PTH1-34 + miR-155 inhibitor groups, while expressions of PPAR-γ, LPL, Fabp4, adiponectin, and C/EBPα were down-regulated. The miR-155 mimic and NPS R-568 groups followed opposite trends. PTH1-34 could promote the osteogenic differentiation and inhibits adipogenic differentiation of hBMSCs through down-regulating miR-155 in PMOP mice.

Intermittent PTH administration improves alveolar bone formation in type 1 diabetic rats with periodontitis.

BACKGROUND: Periodontitis is an infectious disease that manifests as alveolar bone loss surrounding the roots of teeth. Diabetes aggravates periodontitis-induced alveolar bone loss via suppression of bone formation. Intermittent parathyroid hormone (PTH) administration displays an anabolic effect on bone. In this study, we investigated the effect of intermittent PTH administration on alveolar bone loss in type 1 diabetic rats with periodontitis. METHODS: Rats were divided into control (C), periodontitis (P), periodontitis treated with PTH (P + PTH), diabetes with periodontitis (DP), and diabetes with periodontitis treated with PTH (DP + PTH) groups. To induce type 1 diabetes, rats were injected with streptozotocin and periodontitis was induced bilaterally by applying ligatures to the mandibular first molars for 30 days. During the experimental period, the P + PTH and DP + PTH groups were subcutaneously injected with PTH (40 µg/kg) three times per week, whereas the C, P, and DP groups were injected with citrate buffer. To observe the mineralization of the alveolar bone, the DP and DP + PTH groups were injected with calcein on days 10 and 27, and with alizarin red on day 20. Thirty days after ligation, histological findings and fluorescence labeling were analyzed in the furcations of the mandibular first molars. Sclerostin-positive osteocytes were assessed by immunohistochemical analyses. RESULTS: The DP groups had smaller areas of alveolar bone than the other groups, and the DP + PTH group had a larger alveolar bone area than the DP group. The DP group had less osteoid formation than the C group, whereas the DP + PTH had greater osteoid formation than the DP group. Fluorescence labeling results revealed that the DP + PTH group had more mineral deposition on the alveolar bone than the DP group. The DP + PTH group exhibited lower percentage of sclerostin-positive osteocytes in alveolar bone than the DP group. CONCLUSIONS: Intermittent PTH administration diminishes alveolar bone loss and sclerostin expression in osteocytes, but increases osteoid formation and mineralization, suggesting that intermittent PTH administration attenuates diabetes-aggravated alveolar bone loss by the induction of bone formation. PTH-induced bone formation may be related to the regulation of osteocytic sclerostin expression in type 1 diabetic rats with periodontitis.

Long-Term Parathyroid Hormone 1-34 Replacement Therapy in Children with Hypoparathyroidism.

OBJECTIVE: To determine whether multiple daily injections of parathyroid hormone (PTH) 1-34 are safe and effective as long-term therapy for children with hypoparathyroidism. STUDY DESIGN: Linear growth, bone accrual, renal function, and mineral homeostasis were studied in a long-term observational study of PTH 1-34 injection therapy in 14 children. METHODS: Subjects were 14 children with hypoparathyroidism attributable to autoimmune polyglandular syndrome type 1 (N = 5, ages 7-12 years) or calcium receptor mutation (N = 9, ages 7-16 years). Mean daily PTH 1-34 dose was 0.75 ± 0.15 µg/kg/day. Treatment duration was 6.9 ± 3.1 years (range 1.5-10 years). Patients were evaluated semiannually at the National Institutes of Health Clinical Center. RESULTS: Mean height velocity and lumbar spine, whole body, and femoral neck bone accretion velocities were normal throughout the study. In the first 2 years, distal one-third radius bone accrual velocity was reduced compared with normal children (P < .003). Serum alkaline phosphatase correlated with PTH 1-34 dose (P < .006) and remained normal (235.3 ± 104.8 [SD] U/L, N: 51-332 U/L). Mean serum and 24-hour urine calcium levels were 2.05 ± 0.11 mmol/L (N: 2.05-2.5 mmol/L) and 6.93 ± 1.3 mmol/24 hour (N: 1.25-7.5 mmol/24 hour), respectively-with fewer high urine calcium levels vs baseline during calcitriol and calcium treatment (P < .001). Nephrocalcinosis progressed in 5 of 12 subjects who had repeated renal imaging although renal function remained normal. CONCLUSIONS: Twice-daily or thrice-daily subcutaneous PTH 1-34 injections provided safe and effective replacement therapy for up to 10 years in children with hypoparathyroidism because of autoimmune polyglandular syndrome type 1 or calcium receptor mutation.

Optimal dosing and delivery of parathyroid hormone and its analogues for osteoporosis and hypoparathyroidism - translating the pharmacology.

In primary hyperparathyroidism (PHPT), bone loss results from the resorptive effects of excess parathyroid hormone (PTH). Under physiological conditions, PTH has actions that are more targeted to homeostasis and to bone accrual. The predominant action of PTH, either catabolic, anabolic or homeostatic, can be understood in molecular and pharmacokinetic terms. When administered intermittently, PTH increases bone mass, but when present continuously and in excess (e.g. PHPT), bone loss ensues. This dual effect of PTH depends not only on the dosing regimen, continuous or intermittent, but also on how the PTH molecule interacts with various states of its receptor (PTH/PTHrP receptor) influencing downstream signalling pathways differentially. Altering the amino-terminal end of PTH or PTHrP could emphasize the state of the receptor that is linked to an osteoanabolic outcome. This concept led to the development of a PTHrP analogue that interacts preferentially with the transiently linked state of the receptor, emphasizing an osteoanabolic effect. However, designing PTH or PTHrP analogues with prolonged state of binding to the receptor would be expected to be linked to a homeostatic action associated with the tonic secretory state of the parathyroid glands that is advantageous in treating hypoparathyroidism. Ideally, further development of a drug delivery system that mimics the physiological tonic, circadian, and pulsatile profile of PTH would be optimal. This review discusses basic, translational and clinical studies that may well lead to newer approaches to the treatment of osteoporosis as well as to different PTH molecules that could become more advantageous in treating hypoparathyroidism.