Influence of growth hormone on the mandibular condylar cartilage of rats

Reliability of salivary biomarkers as skeletal maturity indicators: A systematic review

OBJECTIVE

To assess the reliability of different salivary biomarkers as skeletal maturity indicators when compared with other methods of skeletal maturity assessment.

METHODS

A comprehensive search was conducted on three electronic databases: PUBMED, Google scholar and Cochrane library for the articles published from 2000 to July 2021. Assessment of skeletal age on the basis of levels of different salivary biomarkers at different pubertal stages was considered as the primary outcome. Electronic search, data collection and risk of bias assessment were performed by two authors with conflict resolution by the third author.

RESULTS

Total 158 articles were retrieved after screening of titles, abstracts and full texts of all articles, of which 15 articles were selected for qualitative synthesis. All these studies were cross-sectional in design. These studies compared the levels of different salivary biomarkers as Alkaline Phosphatase (ALP), Insulin-like Growth Factor - I (IGF-I), Insulin-like Growth Factor Binding Protein-3 (IGFBP-3), Cortisol, Indian Hedgehog (IHH) protein and Dehydroepiandrosterone sulphate (DHEAS) with other methods of skeletal age estimation. Out of these six biomarkers salivary IGF-1 is a reliable indicator for skeletal maturity assessment.

CONCLUSION

The current evidence suggests that salivary biomarkers can be used as an adjunct for growth prediction during orthodontic treatment planning along with other methods of skeletal maturation assessment. Still there is need for further research with longitudinal studies in this field.

Effects of growth hormone and functional appliance on mandibular growth in an adolescent rat model

OBJECTIVES

To investigate the individual and synergistic effects of growth hormone (GH) and functional appliance (FA) on mandibular growth in an adolescent rat model.

MATERIALS AND METHODS

Forty adolescent (6-week-old) female Wistar rats were randomly divided into four groups (10 rats in each group). The control group received a sham treatment (intra-abdominal injection of phosphate-buffered saline), the GH group received an intra-abdominal injection of recombinant human growth hormone, the FA group was treated with a mandibular advancement device, and the GH+FA group received both the GH and FA treatments. The amount of mandibular growth in each group was measured quantitatively using cone-bean computed tomography. The growth of condylar cartilage and expression of matrix metalloproteinases-1 and -13 (MMP-1 and MMP-13) and type II and X collagen (Col II and Col X) were assessed using histological staining and immunostaining techniques.

RESULTS

After 4 weeks, there was significant mandibular growth in the FA group compared with the control group ( P < .05). The GH+FA group had significantly greater mandibular length, thickness of condylar cartilage, and expression of MMP-1, MMP-13, Col II, and Col X in the cartilage than the other groups ( P < .05). The GH+FA group and GH group had significantly greater weight than the FA and control groups ( P < .05).

CONCLUSIONS

The FA as well as GH+FA stimulated mandibular growth in adolescent rats.

Fixed-functional appliance treatment combined with growth hormone therapy

The purpose of this study was to illustrate the effects of growth hormone (GH) therapy and fixed functional appliance treatment in a 13-year-old Class II malocclusion patient without GH deficiency. GH has been shown to effectively increase endochondral growth and induce a more prognathic skeletal pattern. Although a major concern in Class II retrognathic patients is chin deficiency, long-term studies have shown that the mandibular growth enhancement effects of functional appliances are clinically insignificant. This case report demonstrates that the mandible grew significantly during fixed functional appliance treatment combined with GH therapy, with stable results during 2 years 11 months of retention. More studies are needed to evaluate GH therapy as a supplement in Class II treatment.

Growth Hormone and Craniofacial Tissues. An update

Growth hormone is an important regulator of bone homeostasis. In childhood, it determines the longitudinal bone growth, skeletal maturation, and acquisition of bone mass. In adulthood, it is necessary to maintain bone mass throughout life. Although an association between craniofacial and somatic development has been clearly established, craniofacial growth involves complex interactions of genes, hormones and environment. Moreover, as an anabolic hormone seems to have an important role in the regulation of bone remodeling, muscle enhancement and tooth development. In this paper the influence of growth hormone on oral tissues is reviewed.

Effects of growth hormone and ultrasound on mandibular growth in rats: MicroCT and toxicity analyses

It has been shown by previous studies that mandibular growth can be enhanced by the systemic administration of recombinant growth hormone (rGH) and/or local application of therapeutic low intensity pulsed ultrasound (LIPUS). The purpose of this study was to determine if local injection of rGH and application of LIPUS to the temporomandibular joint (TMJ) would synergistically enhance mandibular growth. In an animal study, the effect of rGH, LIPUS, and combination of rGH and LIPUS on male Sprague-Dawley rats was observed. Mandibular growth was evaluated by measuring total hemimandibular and condylar bone volume and bone surface area as well as condylar bone mineral density (BMD) after 21 days on dissected rats' mandibles using micro-computed tomography (MicroCT). The expression of c-jun mRNA extracted from the liver of each of these rats was also quantified by real-time polymerase chain reaction to evaluate possible systemic effect of local rGH administration. Significant growth stimulation was observed in the mandibular and condylar bone of the animals treated with rGH, LIPUS, and rGH/LIPUS combined when compared with the control group. Bone volume, surface area, condylar bone mineral density, and c-jun expression were also compared between the treatment groups and the control in the liver. The results suggest that mandibular growth may be enhanced by injection of rGH or LIPUS application. The current study although showed synergetic effect of rGH and LIPUS application in increasing mandibular condylar head length, there was no significant changes in mandibular bone volume using both treatments together when compared to the two individual treatments. Moreover, combined rGH and LIPUS decreased condylar bone mineral density than each treatment separately. Future research could be directed to investigate the effects of different rGH doses and/or different LIPUS exposures parameters on lower jaw growth.

Growth hormone therapy and craniofacial bones: a comprehensive review

Growth hormone (GH) has significant effects on linear bone growth, bone mass and bone metabolism. The primary role of GH supplementation in children with GH deficiency, those born small for gestational age or with other types of disorders in somatic development is to increase linear growth. However, GH therapy seems to elicit varying responses in the craniofacial region. Whereas the effects of GH administration on somatic development are well documented, comparatively little is known of its effects on the craniofacial region. The purpose of this review was to search the literature and compile results from both animal and human studies related to the impact of GH on craniofacial growth.

Interplay of mechanical loading and growth factors in the mandibular condyle

The mandibular condyle is an important growth site in the developing mandible. The growth of the condyle is known to be highly adaptable to functional factors. This property is exploited in orthodontics for the treatment of class II malocclusions and mandibular asymmetries. However, there is an ongoing debate on the efficacy of functional appliances. The comparison of experimental studies is complicated by the lack of detailed analyses of the load distribution within the condyle. In spite of this, there is a large body of evidence showing that mechanical manipulation of the condyle induces metabolic changes, and changes in the expression of growth factors and other signalling molecules. This review aims to give an overview of the role of growth factors in the condyle with special emphasis on their responsiveness to mechanical perturbation.

Mandibular appliance modulates condylar growth through integrins

Functional orthopedic therapy corrects growth discrepancies between the maxilla and mandible, possibly through postural changes in the musculature and modulation of the mandibular condylar cartilage growth. Using Wistar rats, we tested the hypothesis that chondrocytes respond to forces generated by a mandibular propulsor appliance by changes in gene expression, and that integrins are important mediators in this response. Immunohistochemical analyses demonstrated that the use of the appliance for different periods of time modulated the expression of fibronectin, alpha5 and alphav integrin subunits, as well as cell proliferation in the cartilage. In vitro, cyclic distension of condylar cartilage-derived cells increased fibronectin mRNA, as well as Insulin-like Growth Factor-I and II mRNA and cell proliferation. A peptide containing the Arginine-Glycine-Asparagine sequence (RGD), the main cell-binding sequence in fibronectin, blocked almost all these effects, confirming that force itself modulates the growth of the rat condylar cartilage, and that RGD-binding integrins participate in mechanotransduction.

A longitudinal study of craniofacial growth in idiopathic short stature and growth hormone-deficient boys treated with growth hormone

The aim of this prospective, longitudinal, controlled study is to describe the long-term safety and efficacy of growth hormone (GH) administration on craniofacial morphology in boys with short stature. Forty-six boys, who started GH treatment at the Department of Paediatrics Göteborg Paediatric Growth Research Centre, were consecutively included in the study. Twenty-five boys were classified as growth hormone-deficient (GHD) and 21 as idiopathic short stature (ISS). The patients were injected with 33 (n=31) or 67 (n=15) microg GH/kg body weight/day. The mean age at the start of treatment was 11.8 years [standard deviation (SD) 1.7]. To assess craniofacial growth, standard lateral cephalometric radiographs were obtained at the start of GH treatment, annually during 4 years, and at the end of GH treatment or when growth was less than 1 cm/year. The mean follow-up period was 6.4 years (SD 1.4). Growth changes were compared with boys from a semi-longitudinal reference group of 130 healthy subjects, 7-21 years of age. t-tests for independent and paired samples and multiple regression analysis were applied. Age- and gender-specific standard deviation scores for the cephalometric variables were calculated. Repeated measures analysis of variance was used to identify significant covariates over time, such as low/high GH dose and GHD/ISS and orthodontic treatment. During the study period, eight (out of 40) boys were treated with fixed orthodontic appliances, three with functional appliances (activators), and three with other appliances (plates and lingual arches). During GH treatment period, an overall enhancement in growth of the facial skeleton was observed in boys with short stature. The changes induced by GH yielded a more prognathic growth pattern, a more anterior position of the jaws in relation to the cranial base, and increased anterior rotation of the mandible. The mandibular corpus length and anterior face height of the GH-treated boys were greater at the end of the study compared with the boys in the reference group. No differences in growth response were noted either between the GHD and ISS boys or between those treated with either 33 (low dose) or 67 (high dose) microg GH/kg body weight/day. The only change that remained significantly correlated with orthodontic treatment was the alteration in mandibular ramus height, showing a larger change in the boys who had not undergone orthodontic therapy. The findings of this study demonstrate that GH treatment has a favourable influence on the craniofacial growth pattern of boys with short stature without acromegalic features.

Prostaglandin E2 enhances transforming growth factor-beta 1 and TGF-beta receptors synthesis: an in vivo and in vitro study

The aims of this study were to determine how Prostaglandin E2 (PGE2) locally applied affected the immunodistribution of latent transforming growth factor-beta 1 (TGF-beta1), and how the eicosanoid modified TGF-beta1 release and TGF-beta receptors gene expression in cultured osteoblasts. PGE2 locally delivered on the rat mandible at doses of 0.1 and 0.05 mg/day, but not 0.025 mg/day, over 20 days significantly increased latent TGF-beta1 immunodistribution (P<0.001), comparing with a placebo-treated group. Cultured osteoblasts stimulated with 10(-5) or 10(-7)M PGE2 significantly varied the level of activated TGF-beta1 released into supernatants at different experimental periods compared with negative and positive controls. TGF-beta receptor type I gene expression was significantly increased in osteoblasts (P<0.01) after 10 days of treatment with 10(-5) and 10(-7)M PGE2, whereas 10(-3) M PGE2 produced the opposite effect. It is concluded that PGE2 may stimulate bone deposition by affecting TGF-beta pathway. This effect on the pathway appears to be dose-dependent.

Local application of prostaglandin E2 reduces trap, calcitonin receptor and metalloproteinase-2 immunoreactivity in the rat periodontium

It has been shown that prostaglandin E2 (PGE2) locally released adjacent to the mandible over a 20-day period increases alveolar bone area, in part, due to a reduction in the percentage of eroded surface. To determine the effect of PGE2 on alveolar bone resorption, left mandibles from 24 Lewis rats were treated over a 20-day period with a local application of PGE2 (0.1, 0.05 or 0.025 mg/day) or placebo. The right side served as the non-treated matched control. Tissue sections were stained for tartrate resistant acid phosphatase (TRAP) calcitonin receptor (CTR) and metalloproteinase-2 (MMP-2). Matched samples were analysed by Wilcoxon matched pairs test and, a non-parametric one-way analysis of variance compared groups of treatment. Those tissues treated with PGE2 at doses of 0.1 and 0.05 mg/day showed significantly reduced numbers of TRAP and CTR-positive multinucleated cells compared with matched controls (p<0.005), as well as significantly reduced numbers of TRAP- and CTR-positive multinucleated cells when compared with the placebo-treated group (p<0.001). The number of periodontal ligament cells expressing MMP-2 was also significantly reduced in tissues treated with the two higher doses of PGE2 (p<0.001) comparing with both matched controls and the placebo-treated group. Following a 20-day period, locally released PGE2 at doses of 0.1 and 0.05 mg/day appears to affect alveolar bone resorption in the periodontium of rats, as the number of multinucleated cells expressing TRAP and CTR are significantly reduced. Furthermore, the same doses of PGE2 also significantly reduced the expression of MMP-2 by the periodontal cells.

Influence of growth hormone on the craniofacial complex of transgenic mice

Growth hormone (GH) secretion affects bone and cartilage physiology. This study investigated the effect of GH on the size of the craniofacial structures and their angular relationship. Three different models of mice with a genetically altered GH axis were used: GH excess (giant), dwarf GH antagonist (dwarf-Ant), and dwarf GH receptor knockout (dwarf-KO) mice. Each model was compared with the corresponding wild type (Wt). Five craniofacial distances were analysed: craniofacial length, upper face height, mandibular anterior height, mandibular ramus length, and mandibular corpus length. In addition, upper and lower incisor lengths and four angular relationships, nasal bone with cranial base, maxillary plane with cranial base, mandibular plane with cranial base, and the angle of the mandible, were determined. Data were analysed by one-way ANOVA. Craniofacial length, upper face height and mandibular corpus length were significantly increased in the giant mice and significantly reduced in the dwarf mice. Mandibular anterior height and mandibular ramus length were significantly affected in the dwarf-KO mice but not in the giant mice. The length of both the upper and lower incisors was significantly increased and reduced in the giant and dwarf-KO mice, respectively. In addition, the angle of the mandible was significantly increased in the giant mice and significantly reduced in the dwarf mice. It is concluded that GH plays a major role in the growth and development of the craniofacial complex by directly and indirectly modulating the size and the angular relationships of the craniofacial structures, including the incisor teeth.