On longitudinal bone growth, short stature, and related matters: insights about cartilage physiology from the Utah paradigm

Proteomic Identification of Plasma Components in Tachypleus tridentatus and Their Effects on the Longitudinal Bone Growth Rate in Rats

Tachypleus tridentatus (T. tridentatus) is a marine animal and traditional Chinese medicine. T. tridentatus plasma is a valuable resource for important medical and health-based functions. In this experiment, in order to evaluate the effect and mechanism of T. tridentatus plasma with respect to the promotion of bone tissue growth in rats, the processes of ultrafiltration and mass spectrometry were first used to separate and identify the components of T. tridentatus plasma. Then, a comparison of the effects of the T. tridentatus plasma samples, which each possessed different molecular weights, regarding the growth of the long bones of rats was conducted. Finally, transcriptomics, proteomics, and bioinformatics were all used to analyze the biological functions and related signaling pathways of the T. tridentatus plasma in order to promote rat bone growth. The results showed that the contents of amino acid residues in peptides are related to the growth promotion that was contained in the 10-30 kDa plasma group. Moreover, the T. tridentatus plasma samples were found to be higher in this respect than those in the whole plasma group. In addition, the 10-30 kDa plasma group could significantly promote bone growth activity in rats. The proteomic analysis showed that the proteins that were differentially expressed in the 10-30 kDa plasma group were mainly enriched in the PI3K-AKT signal pathway. Our study suggested that the T. tridentatus plasma possesses promising potential for the purposes of clinical use, whereby it can serve the role of a growth-promoting agent.

Longitudinal Bone Growth Stimulating Effect of Allium macrostemon in Adolescent Female Rats

Allium macrostemon (AM) may affect bone growth by regulating bone formation and resorption. To examine the effect of AM on bone growth, 48 rats were divided into four administration groups in which either distilled water, AM (100 and 300 mg/kg), or recombinant human growth hormone (rhGH; 20 μg/kg) was administered for 10 days. On day 9, all animals were intraperitoneally injected with tetracycline hydrochloride (20 mg/kg), and 48 h after the injection, the rats were sacrificed. Their tibial sections were photographed to measure bone growth. Antigen-specific immunohistochemistry was performed to detect insulin-like growth factor-1 (IGF-1) and bone morphogenetic protein-2 (BMP-2). The food intake of the AM 100 mg/kg group was higher; however, the food intake of the AM 300 mg/kg group was less than that of the control group. The rhGH and AM 100 mg/kg groups showed greater rates of bone growth (359.0 ± 23.7 and 373.1 ± 28.0 μm/day, respectively) compared with the control group. IGF-1 and BMP-2 in the AM and rhGH groups were highly expressed. Indigestion at higher doses of AM led to nonsignificant bone growth in spite of increased IGF-1 and BMP-2 expression. Therefore, a suitable amount of AM could increase bone growth.

Analysis of the functional muscle-bone unit of the forearm in patients with phenylketonuria by peripheral quantitative computed tomography

Bone disease in patients with phenylketonuria (PKU) is incompletely characterized. We therefore analyzed, in a cross-sectional study radius macroscopic bone architecture and forearm muscle size by peripheral quantitative computed tomography (pQCT) and muscle strength by hand dynamometry in a large cohort (n = 56) of adolescent and adult patients with PKU aged 26.0 ± 8.9 (range, 11.8-41.5) years. Data were compared with a reference population (n = 700) from the DONALD study using identical methodology. We observed a significant reduction of cortical thickness (z-score -1.01 ± 0.79), Strength-Strain Index (SSI) (z-score -0.81 ± 1.03), and total bone mineral density (BMD) of the distal radius (z-score -1.05 ± 1.00). Mean muscle cross-sectional area (z-score -0.98 ± 1.19) and muscle grip force (z-score -0.64 ± 1.26) were also significantly reduced, indicating an impaired muscular system as part of the clinical phenotype of PKU. SSI positively correlated (r = 0.53, P < 0.001) with the corresponding muscle cross-sectional area in the reference population; however, the regression line slope in PKU patients was less steep (P < 0.001), indicating that bone strength is not adequately adapted to muscle force. In conclusion, the radial bone in PKU patients is characterized by reduced bone strength in relation to muscular force, decreased cortical thickness, and impaired total BMD at the metaphyseal site. These alterations indicate a mixed bone defect in PKU, both of which are due to primary alterations of bone metabolism and to secondary alterations in response to neuromuscular abnormalities.

Lower limb alignment in children: reference values based on a full-length standing radiograph

BACKGROUND

A full-length standing anteroposterior radiograph of the entire lower extremity has become the standard imaging modality for assessing lower limb alignment. Although reference values of frontal plane deformity parameters based on adult subjects have been established, such values may not be applicable to the pediatric population. The purpose of our study was to establish the reference values of frontal plane alignment and joint orientation angles in children based on a standing full-length radiograph.

METHODS

A database at a single institution was searched for patients who were aged between 1 and 18 years at the time of undergoing a standing full-length radiograph of the lower extremities. Radiographic analysis of lower extremities without any abnormalities was performed by a single observer. Mechanical axis deviation, lateral distal femoral angle (LDFA), medial proximal tibial angle (MPTA), tibiofemoral angle, joint line convergence angle, and mechanical axis station were calculated at yearly intervals. The data were summarized using descriptive statistics, and simple regression analysis was performed to determine the relationship between the patients' age and the magnitude of LDFA and MPTA.

RESULTS

A total of 354 unaffected lower extremities in 253 children were analyzed. Between the ages of 1 and 2 years, the tendency for varus alignment of the lower limb was related to the varus orientation of the distal femur with a mean LDFA of 95 degrees (95% confidence interval [CI], 93-97 degrees). By the age of 3 years, the limb alignment changed to valgus related to a combination of decreasing varus orientation of the distal femur and a mild increase in valgus orientation of the proximal tibia with the mean MPTA changing from 89 degrees (95% CI, 88-90 degrees) to 91 degrees (95% CI, 90-92 degrees). After the age of 7 years, all joint orientation angles were noted to be within the range of reference values that are available for the adult population. Despite changes in limb alignment with growth, the mean mechanical axis of the lower extremity remained within the central half of the knee joint in children older than 1 year of age.

CONCLUSIONS

The change in alignment of the lower limb from 1 to 4 years of life from varus to valgus is primarily related to a progressive decrease in varus orientation of the distal femur. In children younger than 7 years old, age-specific reference values for joint orientation angles of the lower extremity should be used instead of values derived from adult subjects.

Analysis of the functional muscle-bone unit of the forearm in pediatric renal transplant recipients

BACKGROUND

Renal transplantation in children and adolescents is associated with various skeletal complications. The incidence of spontaneous fractures appears to be increased, but the reasons for this are not entirely clear. Our objective was therefore to evaluate macroscopic bone architecture, mass, and strength by peripheral quantitative computed tomography (pQCT), a method that is not influenced by size-related artifacts. In addition, we investigated the muscle-bone relationship in these patients because under physiologic conditions bone strength continually adapts to increasing mechanical loads, that is, muscle force.

METHODS

In 55 patients (41 males) aged 15.8 +/- 4.1 years, we evaluated in a cross-sectional study 4.9 +/- 3.6 years after renal grafting bone mass, density, geometry, and strength of the radius, as well as forearm muscle size and strength, using pQCT at the proximal and distal radius, radiography of the second metacarpal shaft and hand dynamometry. Data were compared to a large cohort (N= 350) of healthy children.

RESULTS

Muscle mass and force were adequate for body size in pediatric renal transplant recipients. However, the radial bone was characterized by an inadequately thin cortex in relation to muscular force, as shown by a reduced height-adjusted cortical thickness both at the proximal (-0.83 +/- 1.12 SDS) and distal radius (-0.52 +/- 1.69 SDS), the metacarpal shaft (-0.54 +/- 1.35 SDS), and by a reduced relative cortical area (-0.90 +/- 1.13 SDS), while the mineralization of trabecular bone was unaltered. As a consequence of cortical thinning, the Strength-Strain Index that reflects the combined strength of trabecular and cortical bone was reduced in these patients.

CONCLUSION

While bone mineral density of the forearm is not decreased in pediatric renal transplant recipients, bone strength in relation to muscular force is reduced. This alteration may contribute to the increased propensity for fractures in these patients.

MAP kinases in chondrocyte differentiation

The majority of the vertebrate skeleton develops through the process of endochondral ossification and involves successive steps of chondrogenesis, chondrocyte proliferation, and hypertrophic chondrocyte differentiation. Interruption of this program through gene mutations and hormonal or environmental factors contributes to numerous diseases, including growth disorders and chondrodysplasias. While a large number of growth factors and hormones have been implicated in the regulation of chondrocyte biology, relatively little is known about the intracellular signaling pathways involved. Recent data provide novel insights into the mechanisms governing acquisition of new phenotypes within the chondrogenic program and suggest multiple pivotal roles for members of the mitogen-activated protein kinase family and their downstream targets in cartilage development. These data are summarized and discussed here.