Effects of intermittent parathyroid hormone treatment on new bone formation during distraction osteogenesis in the rat mandible

Application of chemical factors for acceleration of consolidation phase of the distraction osteogenesis: a scoping review

PURPOSE

This study aimed to analyze the effect of injecting chemical factors compared to conventional distraction osteogenesis (DO) treatment on the bone formation of the distracted area of the maxillofacial region in human and animal studies.

METHOD

Electronic search was done in PubMed, Scopus, Embase, and Cochrane database for studies published until September 2021. The studies' risk of bias (ROB) was assessed using the Cochrane Collaborations and NIH quality assessment tools. Meta-analyses were performed to assess the difference in the amount of bone formation and maximal load tolerance.

RESULTS

Among a total of 58 included studies, eight studies analyzed the bone formation rate of the distracted area in human models and others in animal models. Results of the human studies showed acceptable outcomes in the case of using bone morphogenic protein-2 (BMP-2), autologous bone-platelet gel, and calcium sulfate. However, using platelet reach plasma does not increase the rate of bone formation significantly. Quantitative analyses showed that both BMP-2 (SMD = 26.57; 95% CI = 18.86 to 34.28) and neuron growth factor (NGF) (SMD = 16.19; 95% CI = 9.64 to 22.75) increase the amount of bone formation. Besides, NGF increased the amount of load tolerance significantly (SMD = 30.03; 95% CI = 19.91 to 40.16). Additionally, BMP-2 has no significant impact on the post-treatment maxillary length (SMD = 9.19; 95% CI =  - 2.35 to 20.73).

CONCLUSION

Limited number of human studies with low quality used chemical factors to enhance osteogenesis and showed acceptable results. However, more studies with higher quality are required.

The effect of intermittent parathyroid hormone on bone lengthening: current evidence to inform future effective interventions

PURPOSE

Recent studies have demonstrated the positive effects of parathyroid hormone (PTH) on bone healing, and findings support the use of PTH to accelerate bone healing following distraction osteogenesis. The goal of this review was to compile and discuss the mechanisms potentially underlying the effects of PTH on newly formed bone following a bone-lengthening procedure incorporating all relevant evidence in both animal and clinical studies.

METHODS

This review summarized all evidence from in vivo to clinical studies regarding the effects of PTH administration on a bone-lengthening model. In addition, a comprehensive evaluation of what is currently known regarding the potential mechanisms underlying the potential benefits of PTH in bone lengthening was presented. Some controversial findings regarding the optimal dosage and timing of administration of PTH in this model were also discussed.

RESULTS

The findings demonstrated that the potential mechanisms associated with the action of PTH on the acceleration of bone regeneration after distraction osteogenesis are involvement in mesenchymal cell proliferation and differentiation, endochondral bone formation, membranous bone formation, and callus remodeling.

CONCLUSIONS

In the last 20 years, a number of animal and clinical studies have indicated that there is a prospective role for PTH treatment in human bone lengthening as an anabolic agent that accelerates the mineralization and strength of the regenerated bone. Therefore, PTH treatment can be viewed as a potential treatment to increase the amount of new calcified bone and the mechanical strength of the bone in order to shorten the consolidation stage after bone lengthening.

Overview of Physical and Pharmacological Therapy in Enhancing Bone Regeneration Formation During Distraction Osteogenesis

Distraction osteogenesis (DO) is a kind of bone regeneration technology. The principle is to incise the cortical bone and apply continuous and stable distraction force to the fractured end of the cortical bone, thereby promoting the proliferation of osteoblastic cells in the tension microenvironment and stimulating new bone formation. However, the long consolidation course of DO presumably lead to several complications such as infection, fracture, scar formation, delayed union and malunion. Therefore, it is of clinical significance to reduce the long treatment duration. The current treatment strategy to promote osteogenesis in DO includes gene, growth factor, stem-cell, physical and pharmacological therapies. Among these methods, pharmacological and physical therapies are considered as safe, economical, convenience and effective. Recently, several physical and pharmacological therapies have been demonstrated with a decent ability to enhance bone regeneration during DO. In this review, we have comprehensively summarized the latest evidence for physical (Photonic, Waves, Gas, Mechanical, Electrical and Electromagnetic stimulation) and pharmacological (Bisphosphonates, Hormone, Metal compounds, Biologics, Chinese medicine, etc) therapies in DO. These evidences will bring novel and significant information for the bone healing during DO in the future.

Conditioned medium from mesenchymal stem cells improves condylar resorption induced by mandibular distraction osteogenesis in a rat model

Condylar resorption (CR) after surgical orthognathic treatment is defined as dysfunctional remodeling of the temporomandibular joint manifested by morphological changes with decreased condylar head volume that cause occlusal and esthetic changes. Although both conservative and surgical treatment strategies have been employed for the treatment of CR, effective procedures have not been established till date. In this study, the effects of MSC-CM on CR were investigated. Bone marrow-derived MSCs of rats (rMSCs) were cultured until 80% confluent, cultured in serum-free conditioned medium for 48 h; the collected medium was defined as MSC-CM. Osteogenesis, chondrogenesis, and angiogenesis-related gene expression in rMSCs cultured with MSC-CM was evaluated by quantitative real-time polymerase chain reaction. A rat CR model was used for animal studies, in which CR occurred after mandibular distraction osteogenesis for 10 days. MSC-CM was injected via the tail vein and quantitative and qualitative evaluations were performed by micro-computed tomography (micro-CT) and histology.

MSC-CM enhanced osteogenesis-, chondrogenesis-, and angiogenesis-related gene expression in rMSCs. Micro-CT showed CR in control groups; however, it was observed to be improved in the MSC-CM group. Histologically, an enlarged cartilage layer was seen in the MSC-CM group, while cartilage layers had almost thinned or disappeared in control groups. These results indicate that MSC-CM improved CR.

Skeletal Stem Cell-Schwann Cell Circuitry in Mandibular Repair

Regenerative paradigms exhibit nerve dependency, including regeneration of the mouse digit tip and salamander limb. Denervation impairs regeneration and produces morphological aberrancy in these contexts, but the direct effect of innervation on the stem and progenitor cells enacting these processes is unknown. We devised a model to examine nerve dependency of the mouse skeletal stem cell (mSSC), the progenitor responsible for skeletal development and repair. We show that after inferior alveolar denervation, mandibular bone repair is compromised because of functional defects in mSSCs. We present mSSC reliance on paracrine factors secreted by Schwann cells as the underlying mechanism, with partial rescue of the denervated phenotype by Schwann cell transplantation and by Schwann-derived growth factors. This work sheds light on the nerve dependency of mSSCs and has implications for clinical treatment of mandibular defects.

Intermittent parathyroid hormone 1-34 induces oxidation and deterioration of mineral and collagen quality in newly formed mandibular bone

Intermittent parathyroid hormone (PTH) administration is known to promote bone healing after surgical procedures. However, the mechanism and influence of PTH on the mineral and collagen quality of the jaw are not well understood. Most studies have focused on analyzing the bone density and microstructure of the mandible, and have insufficiently investigated its mineral and collagen quality. Oxidative stress activates osteoclasts, produces advanced glycation end products, and worsens mineral and collagen quality. We hypothesized that PTH induces oxidation and affects the mineral and collagen quality of newly formed mandibular bone. To test this, we examined the mineral and collagen quality of newly formed mandibular bone in rats administered PTH, and analyzed serum after intermittent PTH administration to examine the degree of oxidation. PTH administration reduced mineralization and worsened mineral and collagen quality in newly formed bone. In addition, total anti-oxidant capacity in serum was significantly decreased and the oxidative-INDEX was increased among PTH-treated compared to vehicle-treated rats, indicating serum oxidation. In conclusion, intermittent administration of PTH reduced mineral and collagen quality in newly formed mandibular bone. This effect may have been induced by oxidation.

The effect of bone mass and architecture on mandibular condyle after mandibular distraction

OBJECTIVE

Mandibular distraction surgery is a critical treatment for jaw deformity. However, abnormal mandibular condylar bone resorption is often seen as complication after surgery. Our previous study using a rat mandibular distraction model suggested that overloading leads to mandibular condylar resorption. Host factors are also believed to influence the resorption. To understand the relationship between host factors and resorption, we investigated the effect of changing bone mass and architecture on the mandibular condyle using FK506.

STUDY DESIGN

FK506, an immunosuppressant, was used to compromise bone mass and architecture in this study. Animals were divided into 4 groups: distraction surgery (Dist), FK506 administration (FK), distraction surgery with FK506 administration (FK + Dist), and no surgery or FK506 administration (Cont).

RESULTS

The FK group showed reduced bone mass and impaired bone architecture. The Dist group exhibited abnormal bone resorption on the surface of the condyles, which was slightly exacerbated in the FK + Dist group. Bone defect length decreased over time as a result of bone apposition in the Dist group. However, in the FK + Dist group, the bone defect length remained the same.

CONCLUSIONS

These results suggest that bone mass and architecture strongly affect the tolerance to the overloading and adaptation with bone apposition in condylar resorption site.

An Examination of Differences in the New Bone Formation Promoted by Different Doses of Recombinant Human Parathyroid Hormone during Mandibular Distraction Osteogenesis

BACKGROUND

The administration of different doses of parathyroid hormone to promote mandibular distraction osteogenesis remains unclear. The objective of the present study was to examine the effects of recombinant human parathyroid hormone on new bone formation during mandibular distraction osteogenesis and to investigate the dose-effect relationship associated with this phenomenon.

METHODS

A total of 45 rabbits were used to establish the mandibular distraction osteogenesis model. The rabbits were divided into a control group (that received a subcutaneous injection of 1 ml of saline every other day) and experimental groups A, B, C, and D (that received subcutaneous injections of 10, 20, 30, and 40 μg/kg of recombinant human parathyroid hormone, respectively, every other day). On days 1, 7, and 14 of the consolidation period after the distraction had been completed, new bone in the distraction region was examined through histomorphometric investigation and bone mineral density testing.

RESULTS

On days 1, 7, and 14 of the fixation period, the number of osteoblasts, trabecular bone area, and bone mineral density were greater in each experimental group than in the control group. On day 1 of the consolidation period, group C featured the highest average number of osteoblasts. On day 14 of the consolidation period, group C exhibited the highest bone mineral densities and largest trabecular bone areas.

CONCLUSIONS

Intermittent subcutaneous injections of recombinant human parathyroid hormone can promote new bone formation during mandibular distraction osteogenesis. Different doses of recombinant human parathyroid hormone promoted mandibular distraction osteogenesis to differing extents.

Intermittent parathyroid hormone administration improves periodontal healing in rats

BACKGROUND

Intermittent administration of parathyroid hormone (PTH) promotes new bone formation in patients with osteoporosis and bone fractures. It was shown previously that PTH also reduces periodontitis-related bone loss. The aim of this study is to evaluate the effect of treatment with PTH on periodontal healing in rats.

METHODS

Fenestration defects were created at the buccal surface of the distal root of the mandibular first molars, and both periodontal ligament (PDL) and cementum were removed. Animals were then assigned to two groups (eight animals per group): group 1: control, placebo administration; and group 2: test, human PTH (hPTH) 1-34 administration at a concentration of 40 μg/kg. For both groups, the animals were injected every 2 days, and the animals were sacrificed at 14 and 21 days after surgery. Specimens were harvested and processed for routine decalcified histologic sections. The following parameters were assessed: 1) remaining bone defect extension (RBDE); 2) newly formed bone density (NFBD); 3) total callus area (TCA); 4) osteoclast number (ON) in the callus region; and 5) newly formed dental cementum-like tissue (NFC). Birefringence of root PDL reattachment was also evaluated.

RESULTS

Birefringence analysis showed root PDL reattachment for both groups 21 days after treatment. Intermittent hPTH 1-34 administration decreased RBDE (P <0.01) and increased NFBD (P <0.01), TCA (P <0.01), area of NFC (P <0.01), and ON in the callus region (P <0.01).

CONCLUSION

Within the limits of the present study, intermittent administration of hPTH 1-34 led to an enhanced periodontal healing process compared with non-treated animals.

Comparative genomic analysis and evolution of family-B G protein-coupled receptors from six model insect species

Family-B G protein-coupled receptors (GPCR-Bs) play vital roles in many biological processes, including growth, development and reproduction. However, the evolution and function of GPCR-Bs have been poorly understood in insects. We have identified 87 GPCR-Bs from six model insect species, 20 from Tribolium castaneum, 9 from Apis mellifera, 11 from Bombyx mori, 9 from Acyrthosiphon pisum, 14 from Anopheles gambiae and 24 from Drosophila melanogaster. 22 of them were reported in this study for the first time. Phylogenetic analysis revealed that there are three kinds of evolutionary patterns that occurred among GPCR-Bs during insect evolution: one-to-one orthologous relationships, species-specific expansion and episodic duplication or loss in certain insect lineages. A striking finding was the discovery of a parathyroid hormone receptor like gene (pthrl) in invertebrates, which was independently duplicated in vertebrates and invertebrates, whereas this gene was lost at least twice during insect evolution. These results indicate that PTHRL is possibly divergent in the functions between mammals and insects. The information of family-B GPCRs in nondrosophiline insects has been established, and will promote the further study on the function of these GPCRs and deorphanization of them. On the other hand, this study provides us with multiple function of GPCR-Bs in differential organisms, which will be also the potential attacking targets for new pesticides and drugs.

Parathyroid hormone applications in the craniofacial skeleton

Parathyroid hormone (PTH) is known for its ability to 'build' bone, with research in this area centered on its use as an osteoporosis therapeutic. Recent interest has developed regarding its potential for regenerative applications such as fracture healing and osseous defects of the oral cavity. Many years of investigation using murine gene-targeted models substantiate a role for signaling at the PTH/PTH-related protein (PTHrP) receptor (PPR) in intramembranous bone formation in the craniofacial region as well as in tooth development. Pre-clinical studies clearly support a positive role of intermittent PTH administration in craniofacial bones and in fracture healing and implant integration. A few human clinical studies have shown favorable responses with teriparatide (the biologically active fragment of PTH) administration. Favorable outcomes have emerged with teriparatide administration in patients with osteonecrosis of the jaw (ONJ). New delivery strategies are in development to optimize targeted application of PTH and to help maximize local approaches. The promising host-modulating potential of PTH requires more information to further its effectiveness for craniofacial regeneration and osseous wound-healing, including a better delineation of cellular targets, temporal effects of PTH action, and improved approaches for local/targeted delivery of PTH.