Prenatal murine skeletogenesis partially recovers from absent skeletal muscle as development progresses

Skeletal muscle contractions are critical for normal skeletal growth and morphogenesis but it is unclear how the detrimental effects of absent muscle on the bones and joints change over time. Joint shape and cavitation as well as rudiment length and mineralisation were assessed in multiple rudiments at two developmental stages [Theiler stage (TS)24 and TS27] in the splotch-delayed "muscle-less limb" mouse model and littermate controls. Chondrocyte morphology was quantified in 3D in the distal humerus at the same stages. As development progressed, the effects of absent muscle on all parameters except for cavitation become less severe. All major joints in muscle-less limbs were abnormally shaped at TS24, while, by TS27, most muscle-less limb joint shapes were normal or nearly normal. In contrast, any joints that were fused at TS24 did not cavitate by TS27. At TS24, chondrocytes in the distal humerus were significantly smaller in the muscle-less limbs than in controls, while by TS27, chondrocyte volume was similar between the two groups, offering a cell-level mechanism for the partial recovery in shape of muscle-less limbs. Mineralisation showed the most pronounced changes over gestation. At TS24, all muscle-less rudiments studied had less mineralisation than the controls, while at TS27, muscle-less limb rudiments had mineralisation extents equivalent to controls. In conclusion, the effects of muscle absence on prenatal murine skeletogenesis reduced in severity over gestation. Understanding how mammalian bones and joints continue to develop in an environment with abnormal fetal movements provides insights into conditions including hip dysplasia and arthrogryposis.

Muscular loading affects the 3D structure of both the mineralized rudiment and growth plate at early stages of bone formation

Fetal immobilization affects skeletal development and can lead to severe malformations. Still, how mechanical load affects embryonic bone formation is not fully elucidated. This study combines mechanobiology, image analysis and developmental biology, to investigate the structural effects of muscular loading on embryonic long bones. We present a novel approach involving a semi-automatic workflow, to study the spatial and temporal evolutions of both hard and soft tissues in 3D without any contrast agent at micrometrical resolution. Using high-resolution phase-contrast-enhanced X-ray synchrotron microtomography, we compare the humeri of Splotch-delayed embryonic mice lacking skeletal muscles with healthy littermates. The effects of skeletal muscles on bone formation was studied from the first stages of mineral deposition (Theiler Stages 23 and 24) to just before birth (Theiler Stage 27). The results show that muscle activity affects both growth plate and mineralized regions, especially during early embryonic development. When skeletal muscles were absent, there was reduced mineralization, altered tuberosity size and location, and, at early embryonic stages, decreased chondrocyte density, size and elongation compared to littermate controls. The proposed workflow enhances our understanding of mechanobiology of early bone formation and could be implemented for the study of other complex biological tissues.

Multiscale Characterization of Embryonic Long Bone Mineralization in Mice

Long bone mineralization occurs through endochondral ossification, where a cartilage template mineralizes into bone-like tissue with a hierarchical organization from the whole bone-scale down to sub-nano scale. Whereas this process has been extensively studied at the larger length scales, it remains unexplored at some of the smaller length scales. In this study, the changes in morphology, composition, and structure during embryonic mineralization of murine humeri are investigated using a range of high-resolution synchrotron-based imaging techniques at several length scales. With micro- and nanometer spatial resolution, the deposition of elements and the shaping of mineral platelets are followed. Rapid mineralization of the humeri occurs over approximately four days, where mineral to matrix ratio and calcium content in the most mineralized zone reach adult values shortly before birth. Interestingly, zinc is consistently found to be localized at the sites of ongoing new mineralization. The mineral platelets in the most recently mineralized regions are thicker, longer, narrower, and less aligned compared to those further into the mineralized region. In summary, this study demonstrates a specific spatial distribution of zinc, with highest concentration where new mineral is being deposited and that the newly formed mineral platelets undergo slight reshaping and reorganization during embryonic development.

Effects of Abnormal Muscle Forces on Prenatal Joint Morphogenesis in Mice

Fetal movements are essential for normal development of the human skeleton. When fetal movements are reduced or restricted, infants are at higher risk of developmental dysplasia of the hip and arthrogryposis (multiple joint contractures). Joint shape abnormalities have been reported in mouse models with abnormal or absent musculature, but the effects on joint shape in such models have not been quantified or characterized in detail. In this study, embryonic mouse forelimbs and hindlimbs at a single developmental stage (Theiler Stage 23) with normal, reduced, or absent muscle were imaged in three-dimensions. Skeletal rudiments were virtually segmented and rigid image registration was used to reliably align rudiments with each other, enabling repeatable assessment and measurement of joint shape differences between normal, reduced-muscle and absent-muscle groups. We demonstrate qualitatively and quantitatively that joint shapes are differentially affected by a lack of, or reduction in, skeletal muscle, with the elbow joint being the most affected of the major limb joints. Surprisingly, the effects of reduced muscle were often more pronounced than those of absent skeletal muscle, indicating a complex relationship between muscle mass and joint morphogenesis. These findings have relevance for human developmental disorders of the skeleton in which abnormal fetal movements are implicated, particularly developmental dysplasia of the hip and arthrogryposis. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:2287-2296, 2019.

Prenatal growth map of the mouse knee joint by means of deformable registration technique

Joint morphogenesis is the process during which distinct and functional joint shapes emerge during pre- and post-natal joint development. In this study, a repeatable semi-automatic protocol capable of providing a 3D realistic developmental map of the prenatal mouse knee joint was designed by combining Optical Projection Tomography imaging (OPT) and a deformable registration algorithm (Sheffield Image Registration toolkit, ShIRT). Eleven left limbs of healthy murine embryos were scanned with OPT (voxel size: 14.63μm) at two different stages of development: Theiler stage (TS) 23 (approximately 14.5 embryonic days) and 24 (approximately 15.5 embryonic days). One TS23 limb was used to evaluate the precision of the displacement predictions for this specific case. The remaining limbs were then used to estimate Developmental Tibia and Femur Maps. Acceptable uncertainties of the displacement predictions computed from repeated images were found for both epiphyses (between 1.3μm and 1.4μm for the proximal tibia and between 0.7μm and 1.0μm for the femur, along all directions). The protocol was found to be reproducible with maximum Modified Housdorff Distance (MHD) differences equal to 1.9 μm and 1.5 μm for the tibial and femoral epiphyses respectively. The effect of the initial shape of the rudiment affected the developmental maps with MHD of 21.7 μm and 21.9 μm for the tibial and femoral epiphyses respectively, which correspond to 1.4 and 1.5 times the voxel size. To conclude, this study proposes a repeatable semi-automatic protocol capable of providing mean 3D realistic developmental map of a developing rudiment allowing researchers to study how growth and adaptation are directed by biological and mechanobiological factors.

Bacillus Calmette-Guérin therapy for high-risk superficial bladder cancer

Twelve consecutive patients with carcinoma in situ (CIS) and 17 with T1G3 transitional cell cancer of the bladder were given intravesical Bacillus Calmette-Guérin (BCG) therapy after transurethral resection of all visible lesions. BCG (150 mg in 50 ml normal saline) was given once weekly for 12 weeks and then once monthly for 6 months. The median follow-up was 2.5 years in the CIS group and 3 years in the T1G3 group, with cystoscopy, cytology and random biopsies performed every 3 months. Two of the 12 CIS tumours relapsed, with stage progression (T2G3). Of the 17 T1G3 transitional cell cancers, two relapsed with Ta-1, G1-2 and four progressed to T2-3G3 requiring cystectomy (3) or irradiation (1). One of these four patients died of metastatic disease. BCG therapy thus was effective in preventing progression CIS, but less useful for such purpose in T1G3 transitional cell tumours, for which it cannot be recommended as standard treatment.

Diagnostic and therapeutic dilemmas in nontraumatic spontaneous perirenal hemorrhage

We report on 8 patients who presented with acute abdominal pain, palpable mass and a rapid decrease in hemoglobin. Intravenous pyelogram, ultrasound and computed tomography had been performed but the underlying cause of the perirenal hematoma couldn't be detected. Surgical exploration was decided and 6 total and 2 partial nephrectomies were performed. The pathological report revealed 4 adenocarcinomas and 4 angiomyolipomas. The possibility of spontaneous rupture of the kidney in the evaluation of cases of acute abdomen is particularly stressed.