TM9SF4 is a novel regulator in lineage commitment of bone marrow mesenchymal stem cells to either osteoblasts or adipocytes

Background Osteoporosis is a common bone disease in elderly population caused by imbalanced bone formation and bone resorption. Mesenchymal stem cells (MSCs) are responsible for maintaining this bone homeostasis. The phenotype of transmembrane 9 superfamily 4 (TM9SF4) knockout mice suggests a relationship between TM9SF4 proteins and bone homeostasis. But the effect of TM9SF4 in osteology has never been reported. In the present study, we investigated the function of TM9SF4 in MSC differentiation commitment, as well as its role in osteoporosis. Methods Primary bone marrow MSCs, isolated from TM9SF4 wildtype (TM9SF4+/+) and knockout (TM9SF4−/−) mice, were induced to differentiate into osteoblasts or adipocytes, respectively. The osteogenesis was examined by qRT-PCR detection of osteogenic markers, ALP staining and Alizarin Red S staining. The adipogenesis was tested by qRT-PCR quantification of adipogenic markers and Oil Red O staining. The cytoskeletal organization of MSCs was observed under confocal microscope. The osteoporotic model was induced by ovariectomy in TM9SF4+/+ and TM9SF4−/− mice, followed by Toluidine blue and H&E staining to assess lipid accumulation in trabecular bones, as well as micro-computed tomography scanning and immunohistochemistry staining for bone mass density assessment. The experiments on signaling pathways were conducted using qRT-PCR, Western blot and Alizarin Red S staining. Results We determined the role of TM9SF4 in MSC differentiation and found that TM9SF4−/− MSCs had higher potential to differentiate into osteoblasts and lower capability into adipocytes, without affecting osteoclastogenesis in vitro. In ovariectomy-induced osteoporotic model, TM9SF4−/− mice retained higher bone mass and less lipid accumulation in trabecular bones, indicating an important role of TM9SF4 in the regulation of osteoporosis. Mechanistically, TM9SF4-depleted cells showed elongated actin fibers, which may act through mTORC2/Akt/β-catenin pathway to promote their commitment into osteoblasts. Furthermore, TM9SF4-depleted cells showed higher activity of canonical Wnt pathway, suggesting the participation of Wnt/β-catenin during TM9SF4-regulated osteogenesis. Conclusions Our study demonstrates TM9SF4 as a novel regulator for MSC lineage commitment. Depletion of TM9SF4 preferentially drives MSCs into osteoblasts instead of adipocytes. Furthermore, TM9SF4−/− mice show delayed bone loss and reduced lipid accumulation during ovariectomy-induced osteoporosis. Our results indicate TM9SF4 as a promising target for the future clinical osteoporotic treatment.

Recurrent Atraumatic Pelvic Fractures in a Patient With Cushing’s Disease - Is DEXA Scan Really Useful to Predict the Future Fracture Risk?

Background: Cushing’s disease may present with a variety of clinical features, including osteoporosis and fracture. Due to the inhibitory effects of cortisol on osteoblastic activity and enhancing effects on osteoclastic activity, these patients are more prone to have osteoporotic fractures. We report a case of ACTH dependent Cushing’s disease presenting with recurrent atraumatic pelvic fractures in a woman despite normal bone mineral density for her age. Clinical Case: A 56 year-old-woman was referred to the endocrinology department for suspected Cushing’s syndrome following a recent atraumatic fracture of right pubic ramus. She had a history of weight gain and easy fatigue. On examination, she had subtle changes suggestive of Cushing’s syndrome, including mild truncal obesity, minimal bruising and moon face. She had been taking hormone replacement therapy for 3 years for the post-menopausal symptoms. Her bone mineral density was normal for her age on a recent DEXA scan [femoral neck T score: -0.9, Z score: 0.1, lumbar spine (L1-L4) T score: -1.2, Z score: -0.1]. Her vitamin D, serum calcium and parathyroid hormone levels were normal. Her 24-hour urinary cortisol was 688 nmol/day (reference range: <200 nmol/day), low dose dexamethasone suppression cortisol 525 nmol/L (reference range: <50 nmol/day), ACTH 96 ng/L (reference range: <50 ng/L), indicating ACTH dependent Cushing syndrome. MRI pituitary showed 7 mm right sided hypoenhancing area suggestive of a pituitary microadenoma. CT neck, thorax, abdomen and pelvis did not show any source of ectopic ACTH secretion but did show generalised osteopenia, with old fractures of the ribs and left ilium. She was referred for trans-sphenoidal resection of pituitary tumour. While awaiting pituitary surgery she was treated with metyrapone: at this time she suffered a further atraumatic fracture of the left pubic ramus. Conclusion: Glucocorticoid excess predominantly affects trabecular bones (pelvis, ribs, lumbar spine) as compared to cortical bones. Due to micro-architectural changes, reduction in bone strength is disproportionately greater than would be expected from BMD measured by DEXA. Clinicians should be aware that recurrent fracture of trabecular bones may indicate Cushing’s disease even though other clinical features of cortisol excess are minimal or absent.

High Biofidelity 3D Biomodel Reconstruction from Soft and Hard Tissues (Knee), FEM, and 3D Printing: A Three-Dimensional Methodological Proposal

The modelling of biological structures has allowed great advances in Engineering, Biology, and Medicine. In turn, these advances are seen from the design of footwear and sports accessories, to the design of prostheses, accessories and rehabilitation treatments. The reproduction of the various tissues has gone through an important evolution thanks to the development of computer systems and programs. However, knowledge of the medical-biological and engineering areas continues to be required, and it involves a considerable investment of time and resources. The resulting biomodels still require great precision. The present work shows a methodology that allows to optimize computational resources and reduce elaboration time of biomodels. Through this methodology, it is possible to generate a biomodel of high biofidelity of a human knee. This biomodel is constituted by hard tissues (cortical and trabecular bones) and soft tissues (ligaments and meniscus) resulting in the modelling of the lower third of the femur, the tibial plateaus, the anterior cruciate ligament, posterior cruciate ligament, external lateral ligament, interior lateral ligaments, and the meniscus. With this model and methodology, it is possible to perform numerical analyses that will provide results very similar to those of real life. As, the methodology allows to assign the mechanical properties to each tissue and the anatomical structure.

Microwave Bone Imaging: A Preliminary Investigation on Numerical Bone Phantoms for Bone Health Monitoring

Microwave tomography (MWT) can be used as an alternative modality for monitoring human bone health. Studies have found a significant dielectric contrast between healthy and diseased human trabecular bones. A set of diverse bone phantoms were developed based on single-pole Debye parameters of osteoporotic and osteoarthritis human trabecular bones. The bone phantoms were designed as a two-layered circular structure, where the outer layer mimics the dielectric properties of the cortical bone and the inner layer mimics the dielectric properties of the trabecular bone. The electromagnetic (EM) inverse scattering problem was solved using a distorted Born iterative method (DBIM). A compressed sensing-based linear inversion approach referred to as iterative method with adaptive thresholding for compressed sensing (IMATCS) has been employed for solving the underdetermined set of linear equations at each DBIM iteration. To overcome the challenges posed by the ill-posedness of the EM inverse scattering problem, the L2-based regularization approach was adopted in the amalgamation of the IMATCS approach. The simulation results showed that osteoporotic and osteoarthritis bones can be differentiated based on the reconstructed dielectric properties even for low values of the signal-to-noise ratio. These results show that the adopted approach can be used to monitor bone health based on the reconstructed dielectric properties.

Rickets in white-eared opossums (Didelphis albiventris)

ABSTRACT: Two young opossums were necropsied and diagnosed with rickets. This study aims to describe the clinical-pathological aspects of rickets in Didelphis albiventris. Macroscopically, the opossums presented kyphosis and scoliosis, lateral deviation of the limbs in varus, locomotion difficulty, and enlargement with softening of costochondral junctions (rickety rosary). Samples of bones and joints were processed for hematoxylin and eosin staining and Masson’s trichrome. Microscopically, we observed thickening of the epiphyseal plate, characterized by irregular and multifocal proliferation of serialized and hypertrophic cartilage zones, which formed circular groups of large, dysplastic chondrocytes towards the spongy zone, often surrounded by non-mineralized osteoid tissue. In the cortical bone, there were pale eosinophilic zones around the Havers channels consistent with non-mineralized osteoid. The staining of Masson’s trichrome evidenced the accumulation of osteoid tissue in cortical and trabecular bones. It is possible that a mixed cause of absorption deficiency of vitamin D3 associated with an unbalanced Ca:P diet based on lactose-free milk and fruits may have triggered the disease.

SIMULATION OF THE MECHANICAL STIMULATION EFFECT ON THE PEN JUNCTION BETWEEN BONE AND PELVIC BASED ON FINITE ELEMENT METHODS

Bone remodeling process influenced by cells osteoblast and osteoclast. The remodeling of cortical and trabecular influenced by mechanical stimuli. In this study, cortical and trabecular bones of 25 years old humans were observed, and the result was the cortical bone has the average Young’s modulo 17.9 MPa with the Poisson’s ratio of 0.4. Trabecular bone has the average Young’s modulo of 13 MPa and the Poisson’s ratio of 0.5. The metal orthopedic bone screw, which has used in this research simulation, was is a Titanium screw. The screw has Young’s modulo of 110 GPa and the Poisson’s ratio of 0.29. The results of the simulation of femoral bone elasticity limit with standing activity at the age of 25 were found in the left femur of 112.9416 MPa and the right femur of 115.5134 MPa. The limit of elasticity of the femur due to walking was found in the left femur of 115.2166 MPa with an accuracy of 94.11% and the right femur of 117.6692 MPa.

MiR-128 inhibits the osteogenic differentiation in osteoporosis by down-regulating SIRT6 expression

Background: MicroRNAs (miRNAs) are involved in the regulation of osteogenic differentiation and chondrification in vivo. The purpose of the present study was to explore the potential mechanism of miR-128 in osteoporosis (OP). Methods: Quantitative real-time PCR (qRT-PCR) was used to determine the expression of miR-128 in femoral neck trabecular bones of OP patients (n=40) and non-OP patients (n=40). C2C12 cells were transfected with miR-128 mimic or inhibitor to determine the effect of miR-128 on osteoblastic differentiation of C2C12 cells. Bioinformatics and luciferase reporter genes were used to determine the molecular mechanism of miR-128 in osteoblastic differentiation of C2C12 cells. Results: The qRT-PCR results showed that the expression level of miR-128 in bone samples of OP patients was significantly higher than that of non-OP patients, while miR-128 was significantly down-regulated during the osteogenic differentiation of C2C12 cells. In addition, the results showed that overexpression of miR-128 significantly inhibited the mRNA and protein expression levels of osteocalcin (OC), alkaline phosphatase (ALP) and collagen I type-α1 (COL1A1) in C2C12 cells, while miR-128 inhibitor could reverse this effect. Bioinformatics analysis and dual-luciferase reporter assay found that silencing information regulatory protein 6 (SIRT6) was a direct target of miR-128. The qRT-PCR and Western Blot results found that miR-128 significantly down-regulated the mRNA and protein expressions of SIRT6. Furthermore, silencing SIRT6 significantly inhibited the promoting effect of the miR-128 inhibitor on the expression of osteoblast markers. Conclusion: The above results confirmed that miR-128 inhibited osteoblast differentiation in OP by down-regulating SIRT6 expression, thus accelerating the development of OP.