Effect of in ovo immobilization on development of chick hind-limb articular cartilage: An evaluation using micro-MRI measurement of delayed gadolinium uptake

A rare case of pelvic bone duplication

Iliac bone malformations are rare and result from early disturbance of the genetic and epigenetic processes that come together to form the pelvic girdle. We report the case of a 5-month-old boy found to have a duplication of the ilium and describe the likely causes of this very rare malformation.

Mechanobiology of limb musculoskeletal development

While there has been considerable progress in identifying molecular regulators of musculoskeletal development, the role of physical forces in regulating induction, differentiation, and patterning events is less well understood. Here, we highlight recent findings in this area, focusing primarily on model systems that test the mechanical regulation of skeletal and tendon development in the limb. We also discuss a few of the key signaling pathways and mechanisms that have been implicated in mechanotransduction and highlight current gaps in knowledge and opportunities for further research in the field.

High-resolution MRI analysis of breast cancer xenograft on the chick chorioallantoic membrane

The chick chorioallantoic membrane (CAM) model has been successfully used to study angiogenesis, cancer progression and its pharmacological treatment, tumor pharmacokinetics, and properties of novel nanomaterials. MRI is an attractive technique for non-invasive and longitudinal monitoring of physiological processes and tumor growth. This study proposes an age-adapted cooling regime for immobilization of the chick embryo, enabling high-resolution MRI of the embryo and the CAM tumor xenograft. 64 chick embryos were enrolled in this study. The novel immobilization and imaging protocol was optimized in 29 embryos. From d7 to d18 immobilization of the embryo up to 90 min was achieved by cooling at 4 °C pre-imaging, with cooling times adapted to age. Its application to tumor growth monitoring was evaluated in 15 embryos after xenotransplantation of human MDA-MB-231 breast cancer cells on CAM. Tumor volumes were monitored from d4 to d9 after grafting (d11 to d16 after incubation) applying a T2 -weighted multislice RARE sequence. At d9 after grafting, the tumors were collected and compared with the MRI-derived data by histology and weight measurements. Additional imaging methods comprising DWI, T2 mapping, and the bio-distribution of contrast agents were tested at d9 after grafting in 20 further embryos. With the adaptive cooling regime, motion artifacts could be completely avoided for up to 90 min scan time, enabling high-resolution in ovo imaging. Excellent anatomical details could be obtained in the embryo and tumors. Tumor volumes could be quantified over time. The results prove the feasibility of high-resolution MRI for longitudinal tumor and organ growth monitoring. The suggested method is promising for future applications such as testing tailored and/or targeted treatment strategies, longitudinal monitoring of tumor development, analysis of therapeutic efficacies of drugs, or assessment of tumor pharmacokinetics. The method provides an alternative to animal experimentation.

Acute effects of splint immobilization of the forearm on in vivo microcirculation and histomorphology of the human skin

BACKGROUND

Splint immobilization of the forearm is often performed in clinical practice. Previous studies investigated the effect of immobilization on bone, cartilage, muscle, and tendon, however, the acute effects on human skin microcirculation and histomorphology remains elusive.

METHODS

In 12 healthy, nonsmoking individuals (aged 29.7 ± 9.1 years) a randomly selected forearm was immobilized by splinting for 72 h, whereas the other forearm served as control. In vivo Reflectance-Mode Confocal-Microscopy (RMCM) was performed prior (baseline value) and postimmobilization to evaluate: quantitative blood cell flow; density of functional dermal capillaries; epidermal thickness; and granular cell size.

RESULTS

At 72h forearm immobilization, quantitative blood cell flow was significantly reduced (42.86 ± 3.68 cells/min) compared to the control blood flow (53.11 ± 3.68 cells/min, P < 0.05) and dermal capillaries indicates less functional density (5.73 ± 0.63 capillaries/mm2) compared to the controls (7.04 ± 0.81 capillaries/mm2, P < 0.05). Histometric assessment reveals significantly thinner epidermis following immobilization compared to the control site (40.02 ± 2.91 vs. 46.64±3.09 µm, P < 0.05). Granular cell size was significantly altered at 72 h splinting (730.1 ± 42.53 µm2) compared to the control cell size at 770.2 ± 38.21 µm2. Comparison of baseline values of both forearms indicate statistically insignificance (P > 0.05) for each parameter.

CONCLUSION

At 72 h splint immobilization, for the first time, significant adaptive mechanisms were evaluated on human skin microcirculation and histomorphology using in vivo RMCM. These adaptations may be considered as an incipient atrophy of the human skin. Long-term effects of immobilization including the regenerative potential should be evaluated in further RMCM studies.

Contrast enhanced computed tomography can predict the glycosaminoglycan content and biomechanical properties of articular cartilage

OBJECTIVE

An early hallmark of osteoarthritis (OA) is the progressive loss of glycosaminoglycans (GAGs), the extracellular matrix (ECM) component of articular cartilage that confers it with compressive stiffness. Our aim in this work is to establish the feasibility of using Contrast Enhanced Computed Tomography (CECT) with an anionic iodinated contrast agent - Cysto Conray II - as a minimally invasive tool to measure the changes in the GAG content as well as the compressive stiffness of articular cartilage.

METHODS

The GAG content of mated osteochondral plugs excised from bovine patello-femoral joints was progressively degraded using chondroitinase ABC. The mated plugs were then immersed in an anionic, tri-iodinated contrast agent, imaged using peripheral quantitative computed tomography (pQCT), subjected to an unconfined compressive stress relaxation test and the GAG content measured using 1,9-dimethylmethylene blue (DMMB) assay. Partial correlation analysis was performed to compare the variation in X-ray attenuation measured by pQCT to the variation in GAG content and in equilibrium compressive modulus.

RESULTS

The X-ray attenuation of cartilage exposed to an anionic, tri-iodinated, contrast agent measured by quantitative computed tomography (QCT) accounted for 83% of the variation in GAG content (r(2)=0.83, P<0.0001) and 93% of the variation in the equilibrium compressive modulus (r(2)=0.93, P<0.0001).

CONCLUSION

Using a mated osteochondral plug model to evaluate the biochemical composition and biomechanical properties of cartilage, this study demonstrates the interrelationships between X-ray attenuation, GAG content, and equilibrium compressive modulus, and that CECT can be used to monitor and quantify changes in the GAG content and biomechanical properties of articular cartilage.

Development of the fetal ilium--challenging concepts of bipedality

Macroradiographs of 30 human fetal and neonatal ilia were analysed to investigate the early pattern of trabecular bone organization prior to the influences of direct weight-bearing locomotion. Consistent and well-defined patterns of internal organization were identified within the fetal and neonatal ilium, which correspond with previously recognized regions that have been attributed directly to forces associated with bipedal locomotion. This study proposes that patterns previously attributed to weight-bearing locomotive responses are present in the earliest stages of the development of this bone. It is suggested that the rudimentary scaffold seen in the fetal and neonatal ilium could indicate a predetermined template upon which locomotive influences may be superimposed and perhaps reinforced at a later age. Alternatively, this early pattern may mimic the adult form due to the effects of in-utero limb movement activity even though it is not weight bearing. This is a preliminary study that will be supported in a further communication with three-dimensional micro-computed trabecular analysis.