Aims. Deciphering the genetic relationships between major depressive disorder (MDD) and osteoarthritis (OA) may facilitate an understanding of their biological mechanisms, as well as inform more effective treatment regimens. We aim to investigate the mechanisms underlying relationships between MDD and OA in the context of common genetic variations. Methods. Linkage disequilibrium score regression was used to test the genetic correlation between MDD and OA. Polygenic analysis was performed to estimate shared genetic variations between the two diseases. Two-sample bidirectional Mendelian randomization analysis was used to investigate causal relationships between MDD and OA. Genomic loci shared between MDD and OA were identified using cross-trait meta-analysis. Fine-mapping of transcriptome-wide associations was used to prioritize putatively causal genes for the two diseases. Results. MDD has a significant genetic correlation with OA (r. g. = 0.29) and the two diseases share a considerable proportion of causal variants. Mendelian randomization analysis indicates that genetic liability to MDD has a causal effect on OA (b. xy. = 0.24) and genetic liability to OA conferred a causal effect on MDD (b. xy. = 0.20). Cross-trait meta-analyses identified 29 shared genomic loci between MDD and OA. Together with fine-mapping of transcriptome-wide association signals, our results suggest that Estrogen Receptor 1 (ESR1), SRY-Box Transcription Factor 5 (SOX5), and Glutathione Peroxidase 1 (GPX1) may have therapeutic implications for both MDD and OA. Conclusion. The study reveals substantial shared genetic liability between MDD and OA, which may confer risk for one another. Our findings provide a novel insight into phenotypic relationships between MDD and OA. Cite this article: Bone Joint Res 2022;11(1):12–22

Mice are increasingly used for fracture healing research because of the possibility to use transgenic animals to conduct research on the molecular level. Mice from both sexes can be used, however, there is no consensus in the literature if fracture healing differs between female and male mice. Therefore, the aim of the present study was to analyze the similarities and differences in endochondral fracture healing between female and male C57BL/6J mice, since this mouse strain is mainly used in bone research. For that purpose, 12-weeks-old female and male mice received a standardized femur midshaft osteotomy stabilized by an external fixator. Mice were euthanized 10 and 21 days after fracture and bone regeneration was analyzed by biomechanical testing, µCT analysis, histology, immunohistochemistry and gene expression analysis. At day 21, male mice displayed a significantly larger fracture callus than female mice accompanied by higher number of osteoclasts, higher tissue mineral density and absolute values of bone volume, whereas relative bone volume to tissue volume ratio did not differ between the groups. Biomechanical testing revealed significantly increased bending stiffness in both fractured and intact femurs from male vs. female mice, whereas relative bending stiffness of fractured femurs related to the intact femurs did not differ. 10 days after fracture, male mice display significantly more cartilage and less fibrous tissue area in the fracture callus than female mice, whereas bone area did not differ. On the molecular level, male mice displayed increased active β-catenin expression in the fracture callus, whereas estrogen receptor α (ERα) expression was reduced. In conclusion, male mice showed more prominent cartilaginous callus formation, increased mineralization and whole callus tissue formation, whereas functional outcome after fracture did not differ from female mice. This might be due either to the heavier weight of male mice or because of differences in molecular signaling pathways

MicroRNA´s are regulatory sequences which influence the posttranscriptional synthesis of about 70% of protein encoding genes. In different studies, MicroRNA-146a (miR-146a) was associated with inflammatory and autoimmunological processes. In vitro it was shown, that miR-146a influences the bone metabolism by regulating differentiation of mesenchymal stem cells. The miR-146a deficient mouse starts to develop lymphoproliferative and myeloproliferative disease by 6–8 months of age. In this study, we investigate the influence of miR-146a deficiency on bone structure and stability dependent on age and gender. Material and Methods. Male and female mice of wild type (WT) and miR-146a deficient (KO) animals at the age of 2–3 and 5–7 month were analyzed Femur, Tibia and lumbar vertebra (LWK4) were dissected and used für structural analyses by microcomputer tomography (µCT). Parameters like bone volume/tissue volume, trabecular bone volume, trabecular thickness, number and separation as well as cortical thickness were determined. Biomechanical stability as load to failure testing was determined using torsional testing for the long bones and axial compression testing for the vertebra body. Statistical analysis was performed using Graph Pad Prism (Mann-Whitney-U-Test, significance: p<0.05). Results. Structural analyses of the bone structure in the long bones (femur, tibia) revealed a significant higher bone volume/tissue volume (BV/TV) and trabecular bone mass in the elder (5–7 month) miR-146a deficient female mice compared to the male group or wild type animals of either age. In the diaphysis of the femur a BV/TV of 21% was determined for the elder miR-146a deficient females compared to 9% BV/TV in the age matching WT group. These changes were due to an increase in trabecular thickness and trabecular number in this area. In contrast to that, the cortical thickness of all bones analyzed was lowered in the miR-146a deficient animals (male and female) compared to wild type. Biomechanical stability of long bones as well as the vertebra body of the older, female KO group was significantly lower compared to wild type bones. Femurs showed a maximal torque of 20Nmm compared to 34Nmm in the wild type group. The vertebra of the KO mice showed a maximal force at failure of 22N compared to 40N in the wild type group. Male groups and younger females revealed values comparable to wild type animals. Conclusion. The deficiency of miR-146a leads to an increase of trabecular bone in the long bones of female 5–7 month old mice, but to lowered biomechanical bone stability. If this is due to alterations in differentiation or proliferation of mesenchymal stem cells remains unclear and will be analyzed further. Additionally, gender relation of our observations points to the influence of female specific regulatory mechanisms like the involvement of estrogen receptor related mechanisms

Objectives

The biomembrane (induced membrane) formed around polymethylmethacrylate (PMMA) spacers has value in clinical applications for bone defect reconstruction. Few studies have evaluated its cellular, molecular or stem cell features. Our objective was to characterise induced membrane morphology, molecular features and osteogenic stem cell characteristics.

We report the presence of estrogen receptor (ER) in the ligamentum capitis femoris (LCF) and hip capsule. We took 15 LCF and hip capsule biopsies from 15 patients undergoing hip surgery for the Developmental Dysplasia of the hip (DDH) and 15 hip capsules and LCF’s from intrauterine ex fetuses. The mean age of the babies was 10.3 months (6–18 months) at the time of surgery. Total 60 specimens were grouped into two as the DDH group and the control group and each of these groups were further divided into two to generate the groups for the LCF and hip capsules. Full thickness 1 x 1 cm anterior capsule and LCF portions were taken as biopsy specimens. An immunohistochemical study using monoclonal antibody against to estrogen receptors was performed to identify estrogen target cells in the hip capsule and LCF. The positive rates of ER staining in the control group were % 1.6 ± 0.2 for the LCF and % 1.3 ± 0.2 for the hip capsule, in the DDH group positive rates of ER staining were %2.5 ± 0.3 for the LCF and % 2.0 ± 0.3 for the hip capsule. The positive rates of ER staining in LCF and hip capsule of the control group were significantly lower than that in the DDH group in both groups we found ER’s to be significantly lower in the hip capsule than in LCF. The presence of estrogen receptors in the LCF and hip capsule supports the effect of estrogen in etiology of the DDH

Background/Objective: Since estrogen receptors (ERα/ERβ) were identified in human chondrocytes, animal-and experimental studies have demonstrated the importance of continued estrogen production for the integrity of articular cartilage. However, human epidemiological support of the hypothesis has been inconclusive. The present study investigated the relationship between reduced bone mineral densities (BMD), as a surrogate parameter of endogenous estrogen status – assessed by digital x-ray radiogrammetry (DXR), and reduced minimum hip joint space width (JSW). Methods: Standardised hand radiographs of the Copenhagen Osteoarthritis Study cohort of 3.913 adults (1.470M/2.443F) with a mean age of 60 years (range, 18–92), were analysed by the X-Posure. ™. digital software v. 2.0 (Sectra-Pronosco). The system is operator independent. From 1.200 individual measurements per radiograph mean BMD was calculated. Minimum hip joint JSW was assessed in standardized, pelvic radiographs. Results: DXR-BMD decreased in both men and women after the age of 45 years, progressively more so in women. While minimum hip JSW in men remained relatively unaltered throughout life, a marked decline in female minimum hip JSW after 45 years was observed. We found moderate, but highly significant relationships between reduced BMD and reduced hip JSW in women (p < 0.001), adjusted for age and dysplastic joint incongruity. Conclusion: We believe that the present study supports the hypothetical relationship between reduced estrogen levels and hip joint space width reduction in women

Introduction: Adolescent idiopathic scoliosis (AIS) is the most common form of scoliosis, which appears to be caused by a melatonin signalling dysfunction proved recently in osteoblasts. This pathology occurs and progresses during the time of pre-puberty and puberty growth. This period is known to be under the hormonal control and coincides with many biological changes related to the secretion of estrogens, of which estradiol (E2) is the most active. The female prevalence of AIS disease is clearly evident. Indeed, in Quebec the spine deformities considered clinically significant (at least 11° of deformity) are found in a girl:boy ratio of approximately 2:1 for reduced scoliosis, and this ratio increases to 10:1 for scoliosis of more than 30o of deformation. However, the reason for this female prevalence as well as the role of estrogens and estrogen receptors in AIS is not clear despite the fact that these hormones are known for their impact on bone and bone growth, including the spine. The purpose of the present study was to investigate the role of E2 on the responsiveness of the AIS cells to the melatonin, to determine the expression of estrogens receptors (ERα and ERβ) in AIS tissues and to clarify the impact of estrogen receptor gene polymorphisms in the pathogenesis of AIS. Methodology: The effects of oestrogen on the AIS osteoblasts (n=10) response to the melatonin was determined by measuring the reduction of forskolin-induced cAMP accumulation. The forskolin treated osteoblasts were incubated in the presence of increasing amounts of melatonin (10–11 to 10-5 M) with or without physiological concentrations (10-10 M) of 17-β-estradiol for 16 hours, and the intracellular cAMP measured by radio-immunoassay using Biotrak Kit. Using RT-PCR, we determined ERα and ERβ mRNA expression in osteoblasts from AIS patients (n=14). Polymorphisms of the first intron of the ERα gene, which contains the XbaI and PvuII polymorphisms, were investigated by PCR following digestion with restriction enzyme and using the genomic DNA from lymphocytes isolated from scoliotic patients (n=33). Using the restriction enzymes XbaI and PvuII, the allelic variants XX, Xx, xx, PP, Pp, and pp were identified in 33 AIS patients (uppercase letters represent absence, and lowercase letters represent presence of restriction sites). Results: The intracellular level of cAMP was significantly increased (p< 0.01) in the presence of a physiological concentration of 17-β-estradiol (10-10 M) when compared to the level observed in the presence of melatonin alone (10-9 M) (melatonin + estradiol: 109.46 ± 20.07; melatonin 76.09 ± 12.32 (mean ± SD)). As previously described by Dr Moreau’s team, the same pattern (three type of response to melatonin) takes place in the presence of 17-β-estradiol. We observed the loss of ERβ gene expression in 8/ 14 AIS patients contrasting with ERα gene expression that was found in all AIS patients. The XbaI and PvuII polymorphisms were found in 70% (23/33) and 80% (26/33) of the cases respectively. Of the 33 cases, 21 presented both digestion sites, 24 presented PvuII digestion site (6 homozygote, 18 heterozygote) and 23 (8 homozygote, 15 heterozygote) presented XbaI digestion site. The allelic variants were found as follows: XX: n=8, Xx: n=15, xx: n=8, PP: n=6, Pp: n=18 and pp: n=6. Classified by their location in the spine, seven right thoracic, one left thoracic, one right thoracolumbar, three left thoracolumbar and nine right thoracic-left lumbar were found among the patients presenting PvuII positive polymorphism. Among the patients with XbaI positive polymorphism, six right thoracic, one left thoracic, one right thoracolumbar, three left thoracolumbar and eight right thoracic left lumbar were found. Conclusion: These results show the antagonistic effects of the 17-β-estradiol on AIS osteoblasts response to the melatonin. Thus estrogens interference with melatonin signalling activity would act as a triggering or aggravating factor in the pathogenesis of AIS. At the molecular level, it is possible that estrogens attenuate the response of AIS cells to melatonin through the desensitization of melatonin receptors. The loss of ERβ expression in a significant number of AIS patients appears to be important for the change of the ERα/ERβ receptors ratio that consequently may perhaps alter estrogens signalling pathways. The XbaI and PvuII polymorphisms are present in a significant number of AIS patients but this was not dependant of the curve pattern. These results clearly support the interplays and crosstalk between estrogens and melatonin signalling pathways in AIS aetiopathogenesis. Supported by the Fondation Yves Cotrel, Institut de France

Objective. Despite the current revolution in molecular medicine that has benefitted the treatment of certain diseases (Ross 2002), idiopathic scoliosis has resisted attempts to understand the molecular basis of its curve development. Lowe et al (2002) in a longitudinal study of 55 AIS patients concluded that platelet calmodulin levels correlate closely with curve progression and stabilization by bracing or spine fusion. They suggest that the platelet is a “minimuscle” with a protein contractile system (actin and myosin) similar to that of skeletal muscle. Using Lowe’s data we found that percentage platelet calmodulin change correlates significantly with percentage Cobb angle change (ANOVA, p=0.0003, n=54) that led us to suggest a platelet/skeletal hypothesis to account for their findings as part of a cascade concept for the pathogenesis of AIS. Hypothesis. The human immature vertebral body is unusual among mammals in lacking epiphyses. This may explain why an axial load transmitted directly from the intervertebral disc deforms mature vertebral body end-plates as an axial inward bulge (Brinckmann et al 1983). In immature normal vertebral bodies vascular “lakes” (resembling bunches of grapes) have been found adjacent to the disc growth plates in subjects aged 9 to 13 years of age (Mineiro 1965). These “lakes” may provide a susceptibility to platelet activation from vascular stasis and shear stresses. In addition to their role in hemostasis platelets contain many growth factors including TGF-βs in α-granules that are secreted at a fracture site (Bolander 1992). TGF-βs are found in human neonatal rib growth plates (Horner et al 1998) but, like estrogen receptors, have not yet been sought in human intervertebral disc growth plates. We hypothesize that in the presence of a small scoliosis curve (from unknown causes ?spine, rib, muscle, or nervous system) platelets, as they circulate through vessels in eccentrically-loaded and deforming immature vertebral bodies particularly about the curve apex in the presence of a basic defect, are activated also by repeated axial inward bulges of disc growth plates causing mechanical micro-insults with endothelial cell desquamation and the formation of a calcium-cadmodulin complex. The latter is associated with platelet contraction (shape change) and the secretion from α-granules of various growth factors including angiogenic regulators (platelet release reaction, Hartwig 2003, Reed 2002, Rendu and Brohard-Bohn 2002). These growth factors abet the hormone-driven growth of the already mechanically-compromised disc growth plates and induce anterior spinal overgrowth and curve progression. The basic defect in AIS could be 1) a platelet, endothelial, or subendothelial anomaly, defect, or functional (?hormonal) disorder, and 2) one or more genetic polymorphisms that involve platelet receptors (Afshar-Kharghan and Bray 2002) and putative estrogen receptors in vertebral disc growth plates (Inoue et al 2002ab). The predilection of progressive AIS for girls may be related to the cyclical platelet functions in women associated with normal uterine function (Jones et al 1983, Pansini et al 1986, Tarantino et al 1994, Faraday et 1997). Curve laterality is determined by factors that initiate curve progression. Low plasma melatonin of progressive AIS may act both by a reduced antagonism to calmodulin (Lowe 2000, Dubousset and Machida 2001) and facilitating platelet aggregation with secretion of growth factors from α-granules. Conclusions. The platelet/skeletal hypothesis for progressive AIS and the cascade concept suggests much new research. The hypothesis has genetic, diagnostic, prognostic and potential therapeutic implications. It raises questions about the possibility of changes in platelet calmodulin levels in other progressive and resolving deformities that occur in the immature and adult skeleton