Androgen receptors and experimental bone loss - an in vivo and in vitro study

Sex effects on gingival transcriptomic patterns during initiation, progression, and resolution of periodontitis

BACKGROUND

The prevalence and severity of periodontitis demonstrates altered population distribution with age, sex, and race and ethnicity. While males exhibit greater frequency of disease, particularly with aging, the underlying basis for this observation remains obscure.

OBJECTIVE

This study used a nonhuman primate (Macaca mulatta) model of experimental ligature-induced periodontitis in adult animals to evaluate gingival transcriptomic differences stratified based upon sex of the animal.

METHODS

The 18 animals represented humans ages 40-80 years, with gingival tissue samples obtained at baseline, 0.5 months (initiation), 1 and 3 months (progression), and at 5 months that were 60 days after ligature removal for clinical disease resolution. Microarray analysis was used to quantify gene expression profiles in the gingival tissues.

RESULTS

The results demonstrated clear gene expression differences in healthy (baseline) tissues between the sexes, with elevations in females associated with immune responses and elevation in males related to tissue structural genes. With disease initiation, fewer genes differed between the sexes, while these differences were significantly increased in progressing disease and resolution, particularly in male animals. Overexpressed biological processes showed tissue structural/functional genes at initiation, with host response pathways altered during disease progression. Resolution samples generally demonstrated biological processes of cellular metabolism that differed from baseline healthy samples.

CONCLUSION

The transcriptomic findings support sex as a biological variable in periodontitis using a nonhuman primate model of experimental periodontitis.

Testosterone replacement relieves ligature-induced periodontitis by mitigating inflammation, increasing pro-resolving markers and promoting angiogenesis in rats: A preclinical study

OBJECTIVES

This study aimed to evaluate the inflammatory profile as well as the resolution of inflammation in a ligature-induced periodontal inflammation in rats with depletion and/or supraphysiological testosterone replacement.

DESIGN

Sixty male rats (Holtzman) were used in the present study. Study groups were created as following: (1) Sham (no testicle removal); (2) Orchiectomy (OCX), 3) OCX + Testosterone (OCX + T); (4) Sham + Ligature (SH + L); (5) OCX+L; and 6) OCX + T + L. The surgeries were performed on day 1, and testosterone was administered weekly since day 1. On day 15, a cotton ligature was placed around the lower first molars and maintained for 15 days. Morphological changes in periodontal tissues were determined by histopathological analysis. Immunohistochemistry (factor VIII) and immunoenzymatic assay were performed to evaluate angiogenesis process and (pro- and anti-) inflammatory markers, respectively.

RESULTS

Ligature promoted a marked inflammatory gingival infiltrate and bone loss (P < 0.05). Supraphysiological testosterone treatment increased the percentage of blood vessels, extracellular matrix and fibroblasts in the presence and absence of periodontal inflammation (P < 0.05). A high dose of testosterone increased factor VIII+ blood vessels and IL-10 expression in inflamed gingival tissue, while PGE₂, LXA₄ and MPO were reduced as a result of supraphysiological testosterone administration (P < 0.05).

CONCLUSIONS

These results, in our experimental model, suggest that supraphysiological testosterone treatment stimulated gingival tissue repair during ligature-induced periodontitis, and it seems to be related to an anti-inflammatory and pro-resolutive mechanism resulting by the modulatory effect on PGE₂ and IL-10 related to an enhanced angiogenesis.

Association of sex steroid hormones and new bone formation rate after iliac onlay grafting: a prospective clinical pilot study

Purpose

The present prospective study evaluates the association between new bone formation rate in the iliac onlay graft and sex steroid hormone serum levels.

Methods

A total of 15 partially or completely edentulous postmenopausal females and 9 males with less than 5 mm height of the remaining alveolar bone underwent iliac onlay grafting followed by dental implant placement using a two-stage approach. Sex hormone binding globulin and 17β-estradiol serum levels were investigated by electrochemiluminescence immunoassay, while total testosterone level was analyzed using radioimmunoassay. At the time of implant placement, 12 weeks after grafting, bone biopsies were obtained and analyzed histomorphometrically. Statistical analysis was performed using linear mixed models.

Results

Grafting procedure was successfully performed in all patients. The mean new bone formation rate was 32.5% (116 samples). In men the mean new bone formation rate (38.1%) was significantly higher (p < 0.01) than in women (27.6%). Independent of gender 17β-estradiol and testosterone were positively associated to overall new bone formation rate, albeit a significant influence was only seen for 17β-estradiol in men (p = 0.020). Sex hormone binding globulin had no influence on new bone formation rate (p = 0.897). There was no significant association between new bone formation rate and age (p = 0.353) or new bone formation rate and body mass index (p = 0.248).

Conclusion

Positive association of 17ß-estradiol as well as testosterone with new bone formation rate after iliac onlay grafting indicates a role of sex steroid hormones in alveolar bone regeneration, although the observed influence was only significant for 17ß-estradiol in men.

Graphical Abstract

Osteoporosis and Alveolar Bone Health in Periodontitis Niche: A Predisposing Factors-Centered Review

Periodontitis is a periodontal inflammatory condition that results from disrupted periodontal host-microbe homeostasis, manifested by the destruction of tooth-supporting structures, especially inflammatory alveolar bone loss. Osteoporosis is characterized by systemic deterioration of bone mass and microarchitecture. The roles of many systemic factors have been identified in the pathogenesis of osteoporosis, including endocrine change, metabolic disorders, health-impaired behaviors and mental stress. The prevalence rate of osteoporotic fracture is in sustained elevation in the past decades. Recent studies suggest that individuals with concomitant osteoporosis are more vulnerable to periodontal impairment. Current reviews of worse periodontal status in the context of osteoporosis are limited, mainly centering on the impacts of menopausal and diabetic osteoporosis on periodontitis. Herein, this review article makes an effort to provide a comprehensive view of the relationship between osteoporosis and periodontitis, with a focus on clarifying how those risk factors in osteoporotic populations modify the alveolar bone homeostasis in the periodontitis niche.

Supraphysiological testosterone supplementation improves granulation tissue maturation through angiogenesis in the early phase of a cutaneous wound healing model in rats

OBJECTIVE

The aim of this study was to evaluate the effects of both testosterone depletion and supraphysiological testosterone supplementation in the early phase of an animal cutaneous wound healing model in comparison with the physiological hormonal condition.

MATERIAL AND METHODS

Forty rats were distributed into the following four groups: Control, Orchiectomy (OCX), Durateston (Dura) and OCX+Dura. On day 1, the testicles were removed (OCX group) and the rats (Dura group) received a supraphysiological dose (250 mg/kg) of exogenous testosterone weekly. After 15 days a full-thickness excisional skin wound was created in all animals, which was healed by the second intention for 7 days. On day 22, the rats were euthanatized and the wounds were harvested for histopathological evaluation, immunohistochemistry analyses and multiplex immunoassay. One-way ANOVA and post-hoc Tukey tests were performed.

RESULTS

It was found that the supraphysiological testosterone level increased extracellular matrix deposition, promoted higher blood vessel formation and reduced wound contraction (p < 0.05). Additionally, it also stimulated PCNA-positive fibroblasts and KGF-positive cells (p < 0.05), while orchiectomy reduced the expression of IL-6 and TNF-α and increased VEGF and PDGF (p < 0.05) .

CONCLUSION

In conclusion, the results provide evidence that supraphysiological testosterone supplementation plays a positive role in the early phase of cutaneous wound healing, thus improving granulation tissue maturation through the enhancement of angiogenesis.

Recent Advances in Osteoclast Biological Behavior

With the progress of the aging population, bone-related diseases such as osteoporosis and osteoarthritis have become urgent problems. Recent studies have demonstrated the importance of osteoclasts in bone homeostasis, implying these will be an important mediator in the treatment of bone-related diseases. Up to now, several reviews have been performed on part of osteoclast biological behaviors such as differentiation, function, or apoptosis. However, few reviews have shown the complete osteoclast biology and research advances in recent years. Therefore, in this review, we focus on the origin, differentiation, apoptosis, behavior changes and coupling signals with osteoblasts, providing a simple but comprehensive overview of osteoclasts for subsequent studies.

Physiological testosterone replacement effects on male aged rats with orchiectomy-induced osteoporosis in advanced stage: a tomographic and biomechanical pilot study

Aim: This study aimed to evaluate the effect of physiological testosterone replacement on male aged rats with orchiectomy-induced osteoporosis in advanced stage.Methods: Thirty male rats (Rattus norvegicus albinus, Holtzman lineage) were randomly distributed into 3 groups (n = 10): 1-sham, 2-orchiectomy (OCX), 3-OCX + testosterone replacement (OCX + T). On day 0, a sham or orchiectomy surgery was performed according to the groups. Thirty and sixty days after surgeries, the animals from OCX + T group received testosterone intramuscularly, and the rats in all groups were euthanized on day 77. The femurs were removed for micro-CT scanning and biomechanical test.Results: Orchiectomy resulted in a marked trabecular bone damage (p < 0.05), which was not reversed with testosterone treatment (OCX + T group). The femoral strength was lower in orchiectomized animals (p < 0.05), while the bone strength in OCX + T group was similar to that observed in the sham animals (p > 0.05) and correlated to this parameter the deformation of rupture was smaller in OCX + T group.Conclusion: In conclusion, testosterone depletion induced by orchiectomy established an osteoporotic environment, mainly affecting the trabecular bone. Moreover, even though testosterone treatment did not enhance these variables, the hormonal replacement improved the femoral fracture strength and promoted beneficial effects on the biomechanical parameters compromised by castration in femoral bone.

Lower androgen levels promote abnormal cartilage development in female patients with adolescent idiopathic scoliosis

Background

Adolescent idiopathic scoliosis (AIS) is a disease characterized by changes in the three-dimensional structure of the spine. Studies have shown that the development of AIS might be associated with genetic, biomechanics, endocrine factors and abnormal bone or cartilage development.

Methods

Blood samples collected from 301 female patients (161 females with AIS and 140 females without AIS) were used for genotyping. Forty-eight serum samples from 161 females with AIS and 40 serum samples from 140 females without AIS were subjected to enzyme-linked immunosorbent assays (ELISAs). We also evaluated 32 facet joints (18 females with AIS and 14 females without AIS from the 301 female patients) using immunohistochemistry, Western blotting, and isolation of human primary chondrocytes, among other methods. We treated the AIS primary chondrocytes with dihydrotestosterone (DHT) to verify the relationship among androgen, the androgen receptor (AR), and its downstream pathway proteins.

Results

The serum androgen level in the AIS group was significantly decreased (1.94±0.09 vs. 2.284±0.103) compared with that in the non-AIS (control) group. The single nucleotide polymorphism genotyping results showed that the mutation rates of rs6259 between the AIS and control groups were significantly different (G/G genotype: 48.4% vs. 42.1%, G/A genotype: 40.4% vs. 35.7%, P<0.05). The levels of interleukin (IL)-6 and metalloproteinase (MMP)-13 were increased in the cartilage of AIS patients, and these patients also exhibited decreased AR levels. The cell experiment results showed that androgen reduced the degree of abnormal cartilage development in female AIS patients through the AR/IL-6/signal transducer and activator of transcription 3 (STAT3) signaling pathway.

Conclusions

Our study provides a new perspective on the pathogenesis of AIS and indicates that decreased androgen levels in female AIS patients play a potential role in the development of AIS via the AR/IL-6/STAT3 signaling pathway.

Mandibular-related bone metabolism in orchiectomized rats treated with sex hormones

OBJECTIVE

This study aimed to compare the impact of testosterone and estrogen replacement therapy on mandibular bone density and bone-related markers.

DESIGN

Forty male adult rats were randomly allocated to 4 experimental groups (n = 10/group): Sham (Control); Orchiectomy; Orchiectomy plus testosterone replacement; and orchiectomy plus estradiol replacement. Twenty-four days after orchiectomy, the hemi-mandibles were collected and processed for analysis of microhardness in cortical and trabecular bone, radiographic bone density and histomorphometric evaluation. Serum was collected for the analysis of calcium, phosphorus, alkaline phosphatase and magnesium.

RESULTS

The orchiectomy group had the lowest mandibular bone density (p < 0.01) and also their serum levels of alkaline phosphatase were higher than all other experimental groups (p < 0.001). Estradiol replacement significantly reduced microhardness when compared to orchiectomy in cortical bone (p < 0.05). Both testosterone and estrogen replacement reverted orchiectomy impact on this parameter (p < 0.01); and decreased alkaline phosphatase to levels comparable to the Sham-Control group. The effect of estrogen was more pronounced than testosterone, and a statistically significant difference was observed between Sham-Control and testosterone replacement (p < 0.05) but not between Sham-Control and estradiol replacement groups.

CONCLUSION

Our findings demonstrated that both estradiol and testosterone replacement therapies play a role in mandibular bone metabolism, but suggest different pathways.

Periodontal clinical status, microbial profile, and expression of interleukin-1β in men under androgenic anabolic steroids abuse

OBJECTIVES

Androgenic anabolic steroids (AAS) abuse is a serious health problem associated to several systemic complications. Here, we evaluated the periodontal clinical status, microbial profile, and expression of total protein (TP) and interleukin (IL)-1β in men using AAS.

MATERIALS AND METHODS

Men using AAS were recruited (case group) and matched for age with men who had never used AAS (control group) but also performed physical activities. Plaque index (PI), marginal bleeding (MB), probing depth (PD), clinical attachment level (CAL), and bleeding on probing (BoP) were evaluated. Crevicular fluid and subgingival biofilm were collected from healthy and diseased sites (PD ≥ 4 mm with CAL ≥ 1 mm and BoP) and evaluated for TP, IL-1β, and proportions of 40 bacterial species.

RESULTS

Thirty patients were included (n = 15/group). AAS consumers had significantly higher mean PD and higher percentage of diseased sites; sites with PD ≥ 4 mm or with CAL ≥ 1 mm than non-consumers. Also, AAS users showed a more dysbiotic biofilm containing lower proportions of host-compatible species and higher proportions of pathogens. IL-1β expression was statistically higher in diseased than in healthy sites only in the control group. A statistically positive correlation was detected between periodontal pathogens and IL-1β expression. The number of AAS cycles was positively associated with higher percentages of periodontal pathogens, but not with IL-1β or total protein concentrations.

CONCLUSIONS

AAS intake can worsen clinical and immunological periodontal conditions and the biofilm composition in healthy sites.

CLINICAL RELEVANCE

Dental care professionals should perform full mouth periodontal screening and schedule regular follow-up appointments for patients under AAS use.

Sexual Dimorphism in Osteoclasts

Osteoclasts are the principal mediators of bone resorption. They form through the fusion of mononuclear precursor cells under the principal influence of the cytokines macrophage colony stimulating factor (M-CSF, aka CSF-1) and receptor activator of NF-κB ligand (RANKL, aka TNFSF11). Sexual dimorphism in the development of the skeleton and in the incidence of skeletal diseases is well described. In general, females, at any given age, have a lower bone mass than males. The reasons for the differences in the bone mass of the skeleton between women and men at various ages, and the incidence of certain metabolic bone diseases, are multitude, and include the actions of sex steroids, genetics, age, environment and behavior. All of these influence the rate that osteoclasts form, resorb and die, and frequently produce different effects in females and males. Hence, a variety of factors are responsible for the sexual dimorphism of the skeleton and the activity of osteoclasts in bone. This review will provide an overview of what is currently known about these factors and their effects on osteoclasts.

Evaluation of Risk Factors for External Root Resorption and Dental Caries of Second Molars Associated With Impacted Third Molars

PURPOSE

Impacted third molars (M3s) may lead to external root resorption (ERR) and dental caries (DC) in the adjacent second molars (M2s). The aim of this study was to identify the risk factors for ERR and DC in M2s associated with impacted M3s.

MATERIALS AND METHODS

We implemented a cross-sectional study and enrolled a sample composed of patients with M3s and M2s present and cone-beam computed tomography (CBCT) scans available for review. If there was contact between the M2 and the adjacent M3 and the border of radiolucency was more distinct, the case was considered ERR. Apart from that, the case was considered DC. Potential predictor variables were defined as age, gender, tooth location, M2-M3 contact, root development in M3, M3 inclination, M3 impaction type, and M3 follicular diameter. Outcomes of the study were DC and ERR in M2s. CBCT was used to detect the presence of DC and ERR in M2s.

RESULTS

A total of 250 eligible images of M3s in the upper and lower jaws of 167 patients were included. The mean age of the patients with CBCT images available was 26.08 ± 4 years (range, 18 to 40), and 43.6% of the patients were men. Factors associated with a significantly increased frequency of ERR in M2s included maxillary location, presence of M2-M3 contact, and mesioangular inclination (P < .005). DC in M2s was significantly more likely to occur in those with absence of contact between M2 and M3 (P < .005).

CONCLUSIONS

The results of this study showed an increased risk of ERR to be associated with maxillary molars, mesioangular inclination, and presence of M2-M3 contact. The variable associated with an increased risk of DC was the absence of M2-M3 contact.

Testosterone supplementation, glucocorticoid milieu and bone homeostasis in the ageing male

Male ageing is entwined with a continuous fall in free testosterone levels, which contributes to the pathogenesis of bone loss. Glucocorticoid excess, either dependent on the ageing process or iatrogenically induced, was found to additionally impair the bone structure and metabolism. Cautious testosterone supplementation in this respect may positively affect the glucocorticoid milieu and bone homeostasis, while testosterone-induced changes in the glucocorticoid output could serve as a determinant of bone-related therapeutic outcome. Namely, bone mineral content/density, the parameters of trabecular bone structure as well as bone strength are enhanced, serum calcitonin levels tend to increase, while serum osteocalcin, serum parathyroid hormone and urinary calcium decrease, all upon testosterone administration to the ageing male. In parallel, testosterone application decreases glucocorticoid secretion in the animal models of male ageing, while clinical data in this field are still inconsistent. Importantly, a physiological link exists between testosterone-induced changes in glucocorticoid levels and the tendency of bone status improvement in the ageing male. We believe that the assessment of circulating adrenocorticotropic hormone concentrations together with glucocorticoid levels, reflecting the hypothalamic-pituitary-adrenal axis feedback loop operativeness during testosterone supplementation, represents a well-balanced bone-related therapeutic update.

"Low Testosterone Levels in Body Fluids Are Associated With Chronic Periodontitis"

There is a debate over the association between low testosterone levels in body fluids and the occurrence of chronic periodontitis (CP). The aim of the present systematic review was to assess whether low testosterone levels in body fluids reflect CP. In order to identify studies relevant to the focus question: “Is there a relationship between low testosterone levels in body fluids and CP?” an electronic search without time or language restrictions was conducted up to June 2016 in indexed databases using different keywords: periodontitis, chronic periodontitis, periodontal diseases, testosterone, and gonadal steroid hormones. A total of eight studies were included in the present systematic review. The number of study participants ranged from 24 to 1,838 male individuals with ages ranging from 15 to 95 years. Seven studies measured testosterone levels in serum, two studies in saliva, and one study in gingiva. Four studies reported a negative association between serum testosterone levels and CP. Two studies reported a positive association between decreased testosterone levels in serum and CP. Increased levels of salivary testosterone among patients with CP were reported in one study; whereas one study reported no significant difference in the concentration of salivary testosterone between patients with and without CP. One study identified significant increase in the metabolism of testosterone in the gingiva of patients with CP. Within the limits of the evidence available, the relationship between low testosterone levels and CP remains debatable and further longitudinal studies and control trials are needed.