The mandibles of castrated male rhesus macaques (Macaca mulatta): The effects of orchidectomy on bone and teeth

Coming to the Caribbean: Eighty-five years of rhesus macaques (Macaca mulatta) at Cayo Santiago-A rare nonhuman primate model for the studies of adaptation, diseases, genetics, natural disasters, and resilience

The Cayo Santiago rhesus macaque colony represents one of the most important nonhuman primate resources since their introduction to the Caribbean area in 1938. The 85 years of continuing existence along with the comprehensive database of the rhesus colony and the derived skeletal collections have provided and will continue to provide a powerful tool to test hypotheses about adaptive and evolutionary mechanisms in both biology and medicine.

Biological Deciphering of the "Kidney Governing Bones" Theory in Traditional Chinese Medicine

The description of the "kidney" was entirely different from modern medicine. In traditional Chinese medicine (TCM), the kidney was a functional concept regulating water metabolism, which was closely related to the urinary system, reproductive system, nervous system, endocrine, skeleton, hearing, metabolism, immunity, etc. In particular, the kidney in TCM plays an important regulatory role in the processes of growth, development, prime, aging, and reproduction. Hence, "Kidney Governing Bone" (KGB) was a classical theory in TCM, which hypothesized that the function of the kidney was responsible for bone health. However, the related modern physiological mechanisms of this TCM theory are unclear. This present paper proposed a new understanding and explored the biological basis of the KGB theory. After searching through plenty of reported literature, we discovered that the functions of the kidney in TCM were closely associated with the hypothalamic-pituitary-gonadal (HPG) axis in modern science. The physiological mechanism of the KGB was regulated by sex hormones and their receptors. This review deciphered the connotation of the KGB theory in modern medicine and further verified the scientificity of the basic TCM theory.

Protection against Osteoarthritis Symptoms by Aerobic Exercise with a High-Protein Diet by Reducing Inflammation in a Testosterone-Deficient Animal Model

A testosterone deficiency potentially increases osteoarthritis (OA) symptoms, and dietary protein and exercise affect them. However, their efficacy and their interactions are still unclear. We hypothesized that a high-protein diet (HPD) and regular exercise modulated OA symptoms in testosterone-deficient rats, and it was examined in bilateral orchidectomized (ORX) and monoiodoacetate (MIA)-injected rats. The ORX rats were given a 30 energy percent (En%) protein (HPD) or 17.5 En% protein (CD). Both groups had 39 En% fat in the diet. Non-ORX-CD rats (sham-operation of ORX) were given the CD and no exercise (normal control). After an eight-week intervention, all rats had an injection of MIA into the left knee, and the treatments were continued for an additional four weeks. The non-ORX-CD rats showed a significant increase in body weight compared to the ORX rats, but the ORX rats had elevated fat mass. ORX exacerbated the glucose tolerance by lowering the serum insulin concentrations and increasing insulin resistance. ORX exacerbated the OA symptoms more than the non-ORX-CD. The HPD and exercise improved bone mineral density and glucose metabolism without changing serum testosterone concentrations, while only exercise increased the lean body mass and decreased fat mass, lipid peroxide, and inflammation. Exercise, but not HPD, reduced the OA symptoms, the weight distribution in the left leg, and running velocity and provided better relief than the non-ORX-CD rats. Exercise with HPD improved the histology of the knee joint in the left leg. Exercise reduced lipid peroxide contents and TNF-α and IL-1β mRNA expression in the articular cartilage, while exercise with HPD decreased MMP-3 and MMP-13 mRNA expression as much as in the non-ORX-CD group. In conclusion, moderate aerobic exercise with HPD alleviated OA symptoms and articular cartilage degradation in a similar way in the non-ORX rats with OA by alleviating inflammation and oxidative stress.

Anatomical Variations of the Mandibular Symphysis in a Normal Occlusion Population Using Cone-Beam Computed Tomography

This study aimed to assess the anatomical variations of the mandibular symphysis in a normal occlusion population using cone-beam computed tomography (CBCT). This retrospective cross-sectional study evaluated 200 CBCT scans of patients aged ≥17 with class I occlusion, 1-3 mm overbite and overjet, and <3 mm crowding. The CBCT scans were obtained with NewTom 3G scanner with the exposure settings of 110 kVp, 1.2 mA, 5.4 s time, and six-inch field of view and saved in NNT Viewer. The anterior loop length, labial bone thickness, mandibular bone height at the symphysis, and cortical bone thickness at the right and left canine teeth and central and lateral incisors were measured and compared between males and females and different age groups using one-way ANOVA. The intra- and inter-observer agreements for all landmarks were ICC >0.9 (excellent). The mean length of the anterior loop in females was significantly greater than that in males (P=0.02). Different age groups had significant differences in cortical bone width at the site of the left canine (P=0.03) and vertical bone height at the site of the right central incisor (P=0.05). The majority of parameters related to the mandibular symphysis were greater in normal occlusion males than females. Preoperative CBCT assessment of the mandibular symphysis can greatly help in diagnosis and treatment planning as well as bone harvesting from this area.

Conceptual Design and Prototyping for a Primate Health History Knowledge Model

Primate models are important for understanding human conditions, especially in studies of ageing, pathology, adaptation, and evolution. However, how to integrate data from multiple disciplines and render them compatible with each other for datamining and in-depth study is always challenging. In a long-term project, we have started a collaborative research endeavor to examine the health history of a free-ranging rhesus macaque colony at Cayo Santiago, and build a knowledge model for anthropological and biomedical/translational studies of the effects of environment and genetics on bone development, aging, and pathologies. This paper discusses the conceptual design as well as the prototyping of this model and related graphical user interfaces, and how these will help future scientific queries and studies.

Effects of estrogen deficiency during puberty on maxillary and mandibular growth and associated gene expression - an μCT study on rats

BACKGROUND

Estrogen is a well-known and important hormone involved in skeletal homeostasis, which regulates genes involved in bone biology. Some studies support that estrogen is important for craniofacial growth and development. Therefore this in vivo animal study aimed to investigate, whether and in which way low estrogen levels in the prepubertal period affect craniofacial development in the postpubertal stage and to quantify the gene expression of RANK, RANKL and OPG in cranial growth sites in ovariectomized estrogen-deficient rats during puberty.

METHODS

Control (sham-operated, n = 18) and ovariectomy (OVX, n = 18) surgeries were performed on 21-days-old female Wistar rats. Animals euthanized at an age of 45 days (pubertal stage) were used for gene expression analyses (n = 6 per group) and immunohistochemistry of RANK, RANKL and OPG. Animals euthanized at 63 days of age (post-pubertal stage) were used for craniofacial two-dimensional and three-dimensional craniofacial measurements using μCT imaging (n = 12 per group).

RESULTS

In the μCT analysis of the mandible and maxilla many statistically significant differences between sham-operated and OVX groups were observed, such as increased maxillary and mandibular bone length in OVX animals (p < 0.05). Condylar volume was also significantly different between groups (p < 0.05). The sham-operated group showed a higher level of RANK expression in the midpalatal suture (p = 0.036) and the RANKL:OPG ratio levels were higher in the OVX group (p = 0.015).

CONCLUSIONS

Our results suggest that estrogen deficiency during the prepubertal period is associated with alterations in the maxillary and mandibular bone length and condylar growth.

Aqueous Extracts of Morus alba Root Bark and Cornus officinalis Fruit Protect against Osteoarthritis Symptoms in Testosterone-Deficient and Osteoarthritis-Induced Rats

Water extracts of both Morus alba L. root bark (MBW) and Cornus officinalis Siebold and Zucc fruit (CFW) have traditionally been used to promote men's health in the elderly in Asia. We determined that the 12-week consumption of MBW and CFW could alleviate testosterone-deficiency syndrome and osteoarthritis (OA) symptoms in testosterone-deficient rats, and the action mechanisms were explored. Rats with bilateral orchiectomy (ORX) were fed a 45% fat diet containing either 0.5% MBW (ORX-MBW), 0.5% CFW(ORX-CFW), or 0.5% dextrin (ORX-CON). Sham-operated rats also received 0.5% dextrin (Non-ORX-CON). After 8 weeks of treatment, all rats had an injection of monoiodoacetate (MIA) into the left knee, and they continued the same diet for the additional 4 weeks. ORX-CFW and ORX-MBW partially prevented the reduction of serum testosterone concentrations and decreased insulin resistance, compared to the ORX-CON. ORX-CFW and ORX-MBW protected against the reduction of bone mineral density (BMD) and lean body mass (LBM) compared to the ORX-CON. The limping and edema scores were lower in the order of the ORX-CON, ORX-CRF = ORX-MBW, and Non-ORX-CON (p < 0.05). The scores for pain behaviors, measured by weight-distribution on the OA leg and maximum running velocity on a treadmill, significantly decreased in the same order as limping scores. ORX-MBW protected against the increased expression of matrix metalloproteinase (MMP)-3 and MMP-13 and reduced the production of inflammatory markers such as TNF-α and IL-1β, by MIA in the articular cartilage, compared to the ORX-CON (p < 0.05). The cartilage damage near the tidemark of the knee and proteoglycan loss was significantly less in ORX-MBW than ORX-CON. In conclusion, MBW, possibly CFW, could be effective alternative therapeutic agents for preventing osteoarthritis in testosterone-deficient elderly men.

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.

Sex hormone replacement therapy in periodontology-A systematic review

OBJECTIVE

To analyse whether sex hormone replacement therapy (HRT) improves periodontal parameters and dental implants osseointegration in humans.

MATERIALS AND METHODS

Electronic databases and hand searches were performed from June to August 2018 in SciELO, LILACS and PubMed/MEDLINE. Human observational and interventional studies that evaluated the following parameters were included: clinical attachment loss (CAL), probing pocket depth (PPD), bleeding on probing (BOP), radiographic bone loss (RBL) or osseointegration.

RESULTS

Initial search retrieved 1,282 non-duplicated articles. Fifteen studies were selected after inclusion criteria were applied. All studies were performed in postmenopausal women. Mean differences for PPD reduction ranged from 0.02 to 0.2 mm in HRT-positive patients; mean CAL gain -0.18 to 0.54 mm; mean RBL reduction -0.87 to 0.15 mm; and mean BOP reduction 9%-30.3%. Failure rate of dental implants increased -5.5% to 11.21% when HRT was used.

CONCLUSIONS

Very low but consistent evidence suggests a reduction in BOP and no impact on RBL in postmenopausal women receiving HRT. There are inconsistent reports that suggest that HRT in postmenopausal women: (a) improves or does not impact PPD reduction and CAL gain; and (b) does not impact or increase implant loss. In summary, there is no evidence to support HRT prescription for either men or women for periodontal/implant placement purposes.

Odontogenic abscesses in rhesus macaques (Macaca mulatta) of Cayo Santiago

OBJECTIVES

Odontogenic abscesses are one of the most common dental diseases causing maxillofacial skeletal lesions. They affect the individual's ability to maintain the dental structures necessary to obtain adequate nutrition for survival and reproduction. In this study, the prevalence and pattern of odontogenic abscesses in relation to age, sex, matriline, and living periods were investigated in adult rhesus macaque skeletons of the free-ranging colony on Cayo Santiago, Puerto Rico.

MATERIALS AND METHODS

The skulls used for this study were from the skeletons of 752 adult rhesus macaques, aged 8-31 years, and born between 1951 and 2000. They came from 66 matrilines ranging from 1 to 88 individuals. Fistulae or skeletal lesions caused by odontogenic abscesses drainage, carious lesions, tooth fractures, tooth loss, and alveolar resorption were evaluated visually.

RESULTS

Seventy-two specimens (9.57%) had odontogenic abscesses of varying severity. Males had a significantly higher prevalence than females. The prevalence of odontogenic abscesses in several matrilines was significantly higher than in the population as a whole. Animals born between 1950 and 1965 tended to have a higher prevalence of odontogenic abscesses than those born in later periods.

DISCUSSION

These results suggest that oral pathologies, such as dental and periodontal abscesses in rhesus macaques are fairly common, which may indicate familial effects interwoven with ecological and social factors. The closeness of the rhesus and human genomes allows insights to understand of the epidemiology of these diseases in the human population. Further assessment of the role played by environmental and familial factors on rhesus oral health and disease are warranted.

Quantitation of Mandibular Symphysis Bone as Source of Bone Grafting: Description in Class I and Class III Skeletal Conditions

The aim of this study was to quantify the cortical and cancellous bone in the mandibular symphysis and relate it to the teeth and to the skeletal class. A descriptive study was conducted using cone beam computerized tomography (CBCT). Class I and class III subjects were included, defined according to dental occlusion and cephalogram results. Linear measurements were taken on the CBCT of the mandibular canines, lateral incisors, and central incisors, where the analysis was related to the axial and apical axes considering the bone in relation to the dental area. With previous definitions, an observer took 2 measurements of the height of the mandibular symphysis, cortical bone of the buccal and lower region, and thickness of cancellous bone at different levels; the correlation coefficient between the first and second measurement was 0.99 and presented P = .001. The results were analyzed with analysis of variance and Tukey's honest significant difference test, with P < .05 being statistically significant. The symphysis height was significantly greater in class III subjects. The cortical bone was an average 1.67 ± 0.44 mm in vertical distance in the skeletal class I group and 1.74 ± 0.47 mm in the class III group. The cancellous bone had an average width of 5.03 ± 1.94 mm in the skeletal class I group and 4.74 ± 2.05 mm in the class III group. It was observed that cancellous bone was significantly thicker at the incisor level than at the canine level. There were anatomical differences between skeletal class I and class III subjects, although the clinical significance may be questionable. With the values from these analyses, it may be concluded that there are no significant differences in quantitation of the cortical and cancellous bone in the anterior mandibular symphysis.

Androgen Receptor Involvement in Rat Amelogenesis: An Additional Way for Endocrine-Disrupting Chemicals to Affect Enamel Synthesis

Endocrine-disrupting chemicals (EDCs) that interfere with the steroid axis can affect amelogenesis, leading to enamel hypomineralization similar to that of molar incisor hypomineralization, a recently described enamel disease. We investigated the sex steroid receptors that may mediate the effects of EDCs during rat amelogenesis. The expression of androgen receptor (AR), estrogen receptor (ER)-α, and progesterone receptor was dependent on the stage of ameloblast differentiation, whereas ERβ remained undetectable. AR was the only receptor selectively expressed in ameloblasts involved in final enamel mineralization. AR nuclear translocation and induction of androgen-responsive element-containing promoter activity upon T treatment, demonstrated ameloblast responsiveness to androgens. T regulated the expression of genes involved in enamel mineralization such as KLK4, amelotin, SLC26A4, and SLC5A8 but not the expression of genes encoding matrix proteins, which determine enamel thickness. Vinclozolin and to a lesser extent bisphenol A, two antiandrogenic EDCs that cause enamel defects, counteracted the actions of T. In conclusion, we show, for the first time, the following: 1) ameloblasts express AR; 2) the androgen signaling pathway is involved in the enamel mineralization process; and 3) EDCs with antiandrogenic effects inhibit AR activity and preferentially affect amelogenesis in male rats. Their action, through the AR pathway, may specifically and irreversibly affect enamel, potentially leading to the use of dental defects as a biomarker of exposure to environmental pollutants. These results are consistent with the steroid hormones affecting ameloblasts, raising the issue of the hormonal influence on amelogenesis and possible sexual dimorphism in enamel quality.

"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.