The effects of intro-oral parathyroid hormone on the healing of tooth extraction socket: an experimental study on hyperglycemic rats

Abstract Objective To investigate the effects of intro-oral injection of parathyroid hormone (PTH) on tooth extraction wound healing in hyperglycemic rats. Methodology 60 male Sprague-Dawley rats were randomly divided into the normal group (n=30) and DM group (n=30). Type 1 diabetes mellitus (DM) was induced by streptozotocin. After extracting the left first molar of all rats, each group was further divided into 3 subgroups (n=10 per subgroup), receiving the administration of intermittent PTH, continuous PTH and saline (control), respectively. The intermittent-PTH group received intra-oral injection of PTH three times per week for two weeks. A thermosensitive controlled-release hydrogel was synthesized for continuous-PTH administration. The serum chemistry was determined to evaluate the systemic condition. All animals were sacrificed after 14 days. Micro-computed tomography (Micro-CT) and histological analyses were used to evaluate the healing of extraction sockets. Results The level of serum glucose in the DM groups was significantly higher than that in the non-DM groups (p<0.05); the level of serum calcium was similar in all groups (p>0.05). Micro-CT analysis showed that the DM group had a significantly lower alveolar bone trabecular number (Tb.N) and higher trabecular separation (Tb.Sp) than the normal group (p<0.05). The histological analyses showed that no significant difference in the amount of new bone (hard tissue) formation was found between the PTH and non-PTH groups (p>0.05). Conclusions Bone formation in the extraction socket of the type 1 diabetic rats was reduced. PTH did not improve the healing of hard and soft tissues. The different PTH administration regimes (continuous vs. intermittent) had similar effect on tissue healing. These results demonstrated that the metabolic characteristics of the hyperglycemic rats produced a condition that was unable to respond to PTH treatment.

The efficacy of sustained-release chitosan microspheres containing recombinant human parathyroid hormone on MRONJ

Abstract Treatment of patients with bisphosphonate usage is a significant concern for oral surgeons because it interferes with jaw bone turnover and regeneration. In case of adverse effects manifesting related to bisphosphonate use, oral surgeons are usually treating and keep the patient's symptoms under control. In this study, we aimed to investigate a new treatment protocol for medication-related osteonecrosis of the jaw (MRONJ). This treatment protocol consisted of administering human parathyroid hormone (hPTH) loaded chitosan microspheres which were prepared by ionotropic gelation method or/and the prepared microspheres were suspended in a poloxamer gel. After in-vitro optimization studies, the efficacy of the chosen formulations was evaluated in-vivo studies. Zoledronic acid was administered daily to forty-eight adult female Sprague-Dawley rats, divided into four experimental groups, at a daily concentration of 0.11 mg/kg over three weeks to induce the MRONJ model. At the end of this period, maxillary left molar teeth were extracted. In the first group, the subjects received no treatment. In the negative control group, poloxamer hydrogel containing empty microspheres were immediately applied to the soft tissues surrounding the extraction socket. The treatment group-1 was treated with local injections of poloxamer hydrogel containing hPTH. The treatment group-2 was treated with a single local injection of poloxamer hydrogel containing hPTH-loaded chitosan microspheres. Both treatment groups received a total of 7 µg of hPTH at the end of the treatment protocol. Our study demonstrates successful attenuation of MRONJ through a local drug delivery system combined with hPTH, as opposed to previously attempted treatment strategies.

Effect of local application of alendronate and parathyroid hormone on craniofacial bone repair - a preliminary study

Abstract This study aimed to evaluate the effect of two methods of local application of alendronate and parathyroid hormone (PTH) on bone repair and the systemic implications. A critically sized defect (5 mm) was created in the cranial region of twenty-five male Wistar rats, and the bone removed was particulated, and grafted back to the defect with different treatments. The animals were randomly divided into five groups: A1- bone graft immersion in alendronate solution (3 mg/kg) for 5 minutes; P1- bone graft immersion in PTH solution (20 µg); A2- weekly local applications of alendronate 1 mg/kg; P2- weekly local applications of PTH (20 µg); C- no drugs were used. The animals were euthanized 60 days after surgery. Cranial bone blocks were removed for histological, histomorphometric, and immunohistochemical analyses. MMP-2 and MMP-9 were used for immunolabeling. The kidneys, liver, and brain were also removed from all the rats for histological analysis. The data were submitted for statistical analysis with a level of significance of 0.05 (One-way ANOVA). The group C and group P2 presented a higher quantity of viable bone particles than the remaining groups. Groups A1, A2, and P1 presented with fewer viable bone particles than the control group, with a predominance of non-mineralized connective tissue. The histomorphometric analysis revealed no differences in relative bone area or MMP-2 or MMP-9 immunolabeling between the groups (p>0.05). Group A2 showed presence of fat in the liver consistent with hepatic steatosis. Changes in brain tissue were observed in groups A1 and P1.

Resumo Este estudo visou avaliar o efeito de dois métodos de aplicação local de alendronato e de paratormônio (PTH) no reparo ósseo e avaliar as implicações sistêmicas. Um defeito de tamanho crítico (5 mm) foi criado na calota craniana de vinte e cinco ratos Wistar machos, e o osso removido foi particulado e enxertado de volta no defeito com diferentes tratamentos. Os animais foram divididos aleatoriamente em cinco grupos: A1: imersão do enxerto ósseo em solução de alendronato (3 mg/kg) durante 5 min; P1- imersão do osso em solução de PTH (20 μg); A2- aplicações locais semanais de alendronato 1 mg/kg; P2- aplicações locais semanais de PTH 20 μg; C: não foram utilizados medicamentos. Os animais foram eutanasiados 60 dias após a cirurgia. Foram removidos os blocos ósseos envolvendo a região do defeito para realização das análises histológica, histomorfométrica e imuno-histoquímica. MMP2 e MMP9 foram as imunomarcações utilizadas. Os rins, fígado e cérebro também foram removidos de todos os ratos para análise histológica. Os dados foram submetidos à análise estatística com um nível de significância de 0,05 (One-way ANOVA). A análise histológica revelou que o grupo C e o grupo P2 apresentaram maior quantidade de partículas ósseas viáveis do que as apresentadas pelos demais grupos. Os grupos A1, A2 e P1 apresentaram menos partículas ósseas viáveis em comparação com o grupo controle com predominância de tecido conjuntivo não mineralizado. A análise histomorfométrica não revelou diferenças entres os grupos na área óssea relativa ou em MMP2 e MMP9 (p>0,05). O grupo A2 mostrou presença de gordura no fígado consistente com esteatose hepática. Alterações no tecido cerebral foram observadas nos grupos A1 e P1.

Modulation of in vitro osteoclast activity mediated by different doses of parathyroid hormone / Modulación in vitro de la actividad osteoclástica mediada por diferentes dosis de hormona paratiroidea

Bone remodeling is a process regulated by the interaction between cells and various molecules such as parathyroid hormone (PTH). The aim of the study was to evaluate the effect of different doses of PTH on osteoclast activity in a culture model of bone organs. Six-day-old male C57BL/6 mice (n=14) were euthanized and the calvariae were dissected and sectioned in the middle, keeping the periosteal and endosteal. The bone fragments were divided into three groups: Group I (control - without adding PTH), Group II (addition of 3 nM PTH) and Group III (30 nM PTH), all cultured in aMEM for up to 72 h osteoclast activity was evaluated by biochemical quantification of calcium released in the culture medium at intervals of 24, 48, and 72 h and by histomorphometric analysis of bone resorption lacunae at 72 h our results show that group II exhibited significantly higher values of calcium levels in the medium compared to group I (p<0.05) in all intervals, also being higher for group III at 24 hours (p<0.05). Group II promoted a greater demineralization area (22068 ± 2193 mm2) than those found in group I (2084 ± 38 mm2) and group III (8952 ± 246 mm2), with statistically significant difference (p<0.001) among all groups. We concluded that in culture model of bone organs PTH promotes higher bone resorption when administered in lower doses.

La remodelación ósea es un proceso regulado por la interacción entre las células y varias moléculas como la hormona paratiroidea (PTH). El objetivo de este estudio fue evaluar el efecto de diferentes dosis de PTH sobre la actividad de los osteoclastos en un modelo de cultivo de órganos óseos. Se sacrificaron ratones C57BL/6 machos, de 6 días de edad (n = 14), y se disecaron y seccionaron las calvarias, manteniendo el periostio y endostio. Los fragmentos óseos se dividieron en tres grupos: Grupo I (control - sin adición de PTH), Grupo II (adición de 3 mM de PTH) y Grupo III (30 nM de PTH), todos cultivados en aMEM hasta 72 horas. La actividad de los osteoclastos se evaluó mediante la cuantificación bioquímica de calcio liberado en medio de cultivo, a intervalos de 24, 48 y 72 horas, y por análisis histomorfométrico de las lagunas de resorción ósea a las 72 horas. Nuestros resultados muestran que el grupo II exhibió valores significativamente más altos de calcio en el medio, comparado con el grupo I (p <0.05) en todos los intervalos, siendo también más alto para el grupo III a las 24 horas (p <0.05). El grupo II promovió una mayor área de desmineralización (22068 ± 2193 mm2) que los encontrados en el grupo I (2084 ± 38 mm2) y en el grupo III (8952 ± 246 mm2), con diferencia estadísticamente significativa (p <0,001) entre todos los grupos. Concluimos que en el modelo de cultivo de órganos óseos la PTH promueve una mayor resorción ósea cuando se administra en dosis más bajas.

The N- and C-terminal domains of parathyroid hormone-related protein affect differently the osteogenic and adipogenic potential of human mesenchymal stem cells

Parathyroid hormone-related protein (PTHrP) is synthesized by diverse tissues, and its processing produces several fragments, each with apparently distinct autocrine and paracrine bioactivities. In bone, PTHrP appears to modulate bone formation in part through promoting osteoblast differentiation. The putative effect of PTH-like and PTH-unrelated fragments of PTHrP on human mesenchymal stem cell (MSCs) is not well known. Human MSCs were treated with PTHrP (1-36) or PTHrP (107-139) or both (each at 10 nM) in osteogenic or adipogenic medium, from the start or after 6 days of exposure to the corresponding medium, and the expression of several osteoblastogenic and adipogenic markers was analyzed. PTHrP (1-36) inhibited adipogenesis in MSCs and favoured the expression of osteogenic early markers. The opposite was observed with treatment of MSCs with PTHrP (107-139). Moreover, inhibition of the adipogenic differentiation by PTHrP (1-36) prevailed in the presence of PTHrP (107-139). The PTH/PTHrP type 1 receptor (PTH1R) gene expression was maximum in the earlier and later stages of osteogenesis and adipogenesis, respectively. While PTHrP (107-139) did not modify the PTH1R overexpression during adipogenesis, PTHrP (1-36) did inhibit it; an effect which was partially affected by PTHrP (7-34), a PTH1R antagonist, at 1 microM. These findings demonstrate that both PTHrP domains can exert varying effects on human MSCs differentiation. PTHrP (107-139) showed a tendency to favor adipogenesis, while PTHrP (1-36) induced a mild osteogenic effect in these cells, and inhibited their adipocytic commitment. This further supports the potential anabolic action of the latter peptide in humans.

Parathyroid hormone accelerates decompensation following left ventricular hypertrophy

Parathyroid hormone (PTH) treatment was previously shown to improve cardiac function after myocardial infarction by enhancing neovascularization and cell survival. In this study, pressure overload-induced left ventricular hypertrophy (LVH) was induced in mice by transverse aortic banding (TAB) for 2 weeks. We subsequently evaluated the effects of a 2-week treatment with PTH or saline on compensated LVH. After another 4 weeks, the hearts of the mice were analyzed by echocardiography, histology, and molecular biology. Echocardiography showed that hearts of the PTH-treated mice have more severe failing phenotypes than the saline-treated mice following TAB with a greater reduction in fractional shortening and left ventricular posterior wall thickness and with a greater increase in left ventricular internal dimension. Increases in the heart weight to body weight ratio and lung weight to body weight ratio following TAB were significantly exacerbated in PTH-treated mice compared to saline-treated mice. Molecular markers for heart failure, fibrosis, and angiogenesis were also altered in accordance with more severe heart failure in the PTH-treated mice compared to the saline-treated mice following TAB. In addition, the PTH-treated hearts were manifested with increased fibrosis accompanied by an enhanced SMAD2 phosphorylation. These data suggest that the PTH treatment may accelerate the process of decompensation of LV, leading to heart failure.

Intermittent parathyroid hormone treatment can promote linear growth in the ovariectomized growing rat

To compare the effect of intermittent parathyroid hormone (PTH) treatment with that of estrogen treatment on epiphyseal growth in ovariectomized rats, 46 Sprague-Dawley female rats aged 9-10 weeks (about 200-220 g) were either ovariectomized or sham operated. From 6 weeks after ovariectomy (ovx), rats were daily injected with subcutaneous human recombinant PTH (1-84)-dosed 30 micrograms/kg (the low dose PTH-treated group) or 300 micrograms/kg (the high dose PTH-treated group), 17 beta-estradiol (the 17 beta-estradiol-treated group, 30 micrograms/kg) or vehicle (the ovx-alone group), 5 times a week for 4 weeks. The decalcified sections of the distal femoral epiphyseal plate were analyzed on light microscopy after H&E stain, and the lengths of the zones of proliferation, maturing and hypertrophic chondrocytes were measured. The length of the growth plate, the zone of proliferation and the zone of hypertrophic chondrocyte in the ovx-alone group were significantly shorter than those of the sham-operated group. The treatment of 17 beta-estradiol speeded up the differentiation of cells from proliferating chondrocytes to maturing and hypertrophic chondrocytes even though the length of the growth plate was comparable to that of the sham-operated group. Both low and high dose PTH treatments increased the length of the growth plate, and those lengths were comparable to that of the sham-operated group. The fractions of proliferating, maturing and hypertrophic zone in the low dose PTH-treated group were also comparable to those of the sham-operated group. However, high dose PTH treatment slowed down the differentiation of cells from proliferating chondrocytes to maturing and hypertrophic chondrocytes to a greater extent, and therefore the fraction of proliferating chondrocytes of the high dose PTH-treated group was larger than that of the low dose PTH-treated group (73.8 +/- 1.8 Vs 63.3 +/- 1.3%, p < 0.005). From these results, we showed that intermittent PTH treatment could promote linear growth in the ovariectomized growing rat. We propose that PTH may be an alternative drug candidate for promoting linear growth of long bones without the risk for early closure of the growth plate.

Funçäo paratiroidiana no hipertiroidismo: implicaçöes no metabolismo ósseo e efeito do tratamento / Parathyroid function in hyperthyroidism: implications for bone metabolism and treatment effects of the treatment

Objetivo do estudo: avaliar a perda de massa óssea que acontece no hipertiroidismo através de densitometria e estudar a participaçäo do paratormônio (PTH) na gênese dessa osteopenia. Tipo de estudo: estudo prospectivo de pacientes com hipertiroidismo, antes e após tratamento. Local: Disciplina de Endocrinologia da Escola Paulista de Medicina, Säo Paulo, SP. pacientes: foram analisados 14 pacientes ambulatoriais com quadro clínico e laboratorial de bócio difuso tóxico (doença de Basedow-Graves). Seis desses pacientes foram reestudados após tratamento, estando em eutiroidismo há pelo menos seis meses. Intervençöes: avaliamos a densidade óssea de vértebras lombares por atenuaçäo de fótons (153Gd). Estudamos a secreçäo de PTH (PTH aminoterminal por radioimunoensaio altamente sensível) através da resposta ao teste de estímulo pela hipocalcemia induzida por EDTA, comparando esses resultados com os obtidos em um grupo controle de dez indivíduos normais. Medidas e resultados: a densitometria óssea foi significantemente maior (p < 0,001) após tratamento (1,300 ñ 0,79 gCa/cm2) do que em tirotoxicose (1,229 ñ 0,091gCa/cm2). A queda de Ca avaliada através de sua constante de decremento foi significantemente menor (p < 0,001) nos hipertiróideos (-0,698 x 10**3 ñ0,12 x 10**5) do que en indivíduos normais (-1,486 x 10**3ñ 9,33 x 10**5), regularizando-se após terapêutica. A queda de Ca foi suficiente para provocar elevaçäo dos níveis de PTH, que atingiram um platô de resposta máxima. O incremento máximo de PTH nos pacientes em tirotoxicose (2,34 ñ 0,45pmol) foi significantemente menor (p < 0,01) do que nos controles normais (7,51 ñ 0,40). Após seis meses de eutiroidismo, a resposta secretória de PTH normalizou-se. Conclusöes: o aumento da densidade óssea nos pacientes hipertiróideos, após tratamento, demonstra que esses pacientes haviam sofrido algum grau de osteopenia durante a fase de tirotoxicose. A menor reserva hormonal paratiroidiana no hipertiroidismo sugere que as alteraçöes ósseas encontradas nesses pacientes sejam devidas principalmente à açäo direta dos próprios hormônios tiroidianos. Essas alteraçöes säo reversíveis após seis meses de eutiroidismo

Effects of parathyroid hormone on urinary acidification in the rat

To evaluate the effects of parathyroid hormone (PTH) on urinary acidification parameters, thyroparathyroidectomy was performed in normal (TPTX) and in calcium-supplemented rats (TPTX+Ca2**). Both groups were supplemented with thyroxin. Glomerular filtration rate (GFR) fell from 7.79 ñ 0.33 in the control group (C) to 4.88 ñ 0.26 ml min**-1Kg**-1 in TPTX, while net acid excretion fell from 5.65 ñ 0.22 in C to 3.76 ñ 0.26 µmol min**1Kg in TPTX. Kinetic dat of urinary acidification obtained by microperfusion techniques in proximal tubules showed that the half-time of acidification (t/2) rose from 4.75 ñ 0.24 s in C to 8.97 ñ 0.64s in TPTX and persisted elevated in TPTx +Ca**2+ (7.40 ñ 0.43s); in the latter group, stationary pH was not significantly different from that of the control group. Bicarbonate reabsorption (J**HCO3) fell from 2.18 ñ 0.15 in C to 0.823 ñ 0.082 in TPTX and was 1.53 ñ 0.073 nmol s**-1 cm**-2 in TPTX+Ca**2+. These suggest that normal pH gradients depend on normal calcium levels, but acidification half-times are dependent on PTH, which also contributes keeping glomerular hemodynamics and acidification rates at normal levels

Endocrine regulation of calcium and phosphate in rat eye lens and its significance in cataract formation.

Parathyroid hormone (PTH), calcitonin (CT)and calciferol (Vit. D3) operate synchronously to maintain a balance between calcium and phosphate levels in serum. An aberration of specific steps in the homeostatic process results in hypo/hyper phosphatemia. These aberrations may eventually lead to several diseased states. PTH and Vit. D3 induced hypercalcemia can, however, be significantly inhibited by calcitonin (CT). These findings have been correlated with the levels of calcium and phosphate obtained from human senile cataractous lenses of cortical and nuclear types. The comparison of the results indicate that amongst these three hormones PTH is most vulnerable in leading towards conditions for possible cataract formation in rat lens.

The effect of alkalosis on the glucose-mediated insulin release by the rat

Efecto de la alcalosis sobre la secreción de insulina en la rata. Las ratas intactas que reciben una dosis de bicarbonato de sodio por vía gástrica entran en alcalosis por un período de tres horas durante el cual tienen bajos niveles plasmáticos de fosfato y calcio iónico y elevada excreción urinaria de cAMP, "clearance" de fosfato e incorporación de calcio del líquido extracelular al tejido pancreático, todos efectos conocidos del aumento de secreción de hormona paratiroidea (PTH). La secreción total de insulina en las dos horas siguientes a la estimulación con glucosa se halló significativamente aumentada en los animales alcalóticos intactos, respecto de sus controles simultáneos. La respuesta de las ratas alcalóticas paratiroidectomizadas, en cambio, sugirió agotamiento o inhibición de la secreción de insulina. Se propone la hipótesis de que la PTH, al aumentar la permeabilidad de las células beta del páncreas al calcio, compensa el efecto adverso, para la secreción de insulina, de la reducción de la concentración de calcio ionizado en el líquido extracelular que se observa en alcalosis