TGF-β and BMP signaling in osteoblast,skeletal development,and bone formation,homeostasis and disease

INTRODUCTIONThe transforming growth factor-β （TGF-β） superfamily com- prises TGF-βs, Activin, bone morphogenetic proteins （BMPs） and other related proteins. TGF-β superfamily members act through a heteromeric receptor complex,, comprised of type I and type II receptors at the cell surface that transduce intracellular signals via Smad complex or mitogen-activated protein kinase （MAPK） cascade.

Association of Estrogen Receptor-α Gene PvuII Polymorphisms with the Effect of Calcium Supplementation on Skeletal Development in Chinese Pubertal Girls

Objective To investigate the association of estrogen receptor alpha （ER-c0 PvulI polymorphisms with the effect of calcium supplementation on bone development in Chinese pubertal girls, and to study the importance of calcium supplementation by maximizing the peak bone mass at their pubertal stage for bone development and osteoporosis prevention and the role of estrogen in regulating bone mass. Methods Ninety-four pubertal girls were recruited in the study and divided into two groups and three sub-groups according to the ER-α PvulI polymorphisms. One year before and after calcium supplementation, bone mineral density （BMD） was measured by DEXA, while BGP, BAP, TRACP5b, and 25-OH-VitD3, as well as estrogen were detected by ELISA. Analysis of covariance was used to examine the effect of ER-ct polymorphisms on bone development. Results The absolute increase and percentage change of BGP were significantly higher in the supplemented group than in the control group （P〈0.05）. In the intervened group, The increase and percentage change of the total body and radio distal 1/3 BMD were higher in PP than in PP genotype （P〈0.05）, and the increase of BAP in Pp was also higher than PP in the same group （P〈0.05）. Conclusion PP genotype shows a better response to calcium supplementation than the other Pvull polymorphisms.

Dynamic Expression of MicroRNA-127 During Porcine Prenatal and Postnatal Skeletal Muscle Development

MicroRNAs （miRNAs）, evolutionarily conserved non-coding RNAs in length 21-24 bp, play a critical role in skeletal muscle development. In this study, to explore the function of mircoRNA-127 in porcine skeletal muscle development, eight tissue samples from adult pigs and longissimus muscle samples at 26 developmental stages were collected from Tongcheng and Landrace pigs. The spatial-temporal expression proifles of miRNA-127 were carried out using step-loop quantitative real-time PCR （stem-loop RT-PCR）. To explore the molecular functions of miRNA-127, we predicted its target genes and performed functional annotation using bioinformatics methods. Results suggested that miRNA-127 was abundantly expressed in heart, ovary, uterus and spleen tissues and was weakly expressed in liver, lung, kidney and small intestine in both Tongcheng and Landrace pigs. And miRNA-127 showed signiifcant expression differences in heart, ovary, spleen and uterus tissues between these two breeds. miRNA-127 basically kept at a relatively stable high level in middle and later embryonic stages and a low expression level in early embryonic stages and postnatal stages, but the expression levels of miRNA-127 were higher in Tongcheng pigs than in Landrace at most developmental stages. miRNA-127 potentially regulated 240 candidate genes. Results of Gene Ontology and KEGG pathway analysis indicated that these genes could be involved in many molecular functions and mechanisms, such as regulation of the force of heart contraction, regulation of transcription, regulation of T cell differentiation, MAPK signaling pathway and GnRH signaling pathway. Many signiifcantly enriched GO terms and KEGG pathways were related to skeletal muscle development. This study will be helpful to understand the biological function for miRNA-127 and identify candidate gene associated with meat production traits in pigs.

Fibroblast growth factor(FGF)signaling in development and skeletal diseases

Fibroblast growth factors(FGF)and their receptors serve many functions in both the developing and adult organism.Humans contain 18 FGF ligands and four FGF receptors(FGFR).FGF ligands are polypeptide growth factors that regulate several developmental processes including cellular proliferation,differentiation,and migration,morphogenesis,and patterning.FGF-FGFR signaling is also critical to the developing axial and craniofacial skeleton.In particular,the signaling cascade has been implicated in intramembranous ossification of cranial bones as well as cranial suture homeostasis.In the adult,FGFs and FGFRs are crucial for tissue repair.FGF signaling generally follows one of three transduction pathways:RAS/MAP kinase,PI3/AKT,or PLCg.Each pathway likely regulates specific cellular behaviors.Inappropriate expression of FGF and improper activation of FGFRs are associated with various pathologic conditions,unregulated cell growth,and tumorigenesis.Additionally,aberrant signaling has been implicated in many skeletal abnormalities including achondroplasia and craniosynostosis.The biology and mechanisms of the FGF family have been the subject of significant research over the past 30 years.Recently,work has focused on the therapeutic targeting and potential of FGF ligands and their associated receptors.The majority of FGF-related therapy is aimed at age-related disorders.Increased understanding of FGF signaling and biology may reveal additional therapeutic roles,both in utero and postnatally.This review discusses the role of FGF signaling in general physiologic and pathologic embryogenesis and further explores it within the context of skeletal development.

Endogenous Glucocorticoids and Bone

While the adverse effects of glucocorticoids on bone are well described, positive effects of glucocorticoids on the differentiation of osteoblasts are also observed. These paradoxical effects of glucocorticoids are dose dependent. At both physiologicaland supraphysiological levels of glucocorticoids, osteoblasts and osteocytes are the major glucocorticoid target cells. However, the response of the osteoblasts to each of these is quite distinct. At physiology levels, glucocorticoids direct mesenchymal progenitor cells to differentiate towards osteoblasts and thus increase bone formation in a positive way. In contrast with ageing, the excess production of glucocorticoids, at both systemic and intracellular levels, appear to impact on osteoblast and osteocytes in a negative way in a similar fashion to that seen with therapeutic glucocorticoids. This review will focus on therole of glucocorticoids in normal bone physiology, with particular emphasis on the mechanism by which endogenous glucocorticoids impact on bone and its constituent cells.

The genetic regulation of skeletal muscle development:insights from chicken studies

Skeletal muscle development is a complex multi-process trait regulated by various genetic factors.The chicken embryo is an ideal model system for studying skeletal muscle development. However, only a small proportion of the genetic factors affecting skeletal muscle development have been identified in chicken. The aim of this review is to summarize recent knowledge about the genetic factors involved in the regulation of skeletal muscle development in the chicken, such as gene polymorphisms, epigenetic modification, noncoding RNAs and transcription factors, which can influence skeletal muscle development at the genome, epigenome,transcriptome and proteome levels. Research on the regulation of skeletal muscle development in chicken is not yet comprehensive and most of the candidate genes and single nucleotide polymorphisms related to chicken muscle growth remain to be verified in experimental studies. In addition, the data derived from transcriptome sequencing and genome-wide association studies still require further investigation and analysis and comprehensive studies on the regulation of chicken skeletal muscle development will continue as a major research focus.

Function and regulation of muscle stem cells in skeletal muscle development and regeneration:a narrative review

Skeletal muscle plays an essential role in generating the mechanical force necessary to support the movement of our body and daily exercise. Compared with cardiac and smooth muscle, in mammals, skeletal muscle exhibits remarkable regenerative capacity in response to damage. Muscle stem cells, also known as satellite cells, directly contribute to regeneration. Here, we review primary and secondary myogenesis processes with a focus on muscle stem cells, as well as the function and regulation of muscle stem cells in adult muscle regeneration in mammals.

Filamin B:The next hotspot in skeletal research?

Filamin B （FLNB） is a large dimeric actin-binding protein which crosslinks actin cytoskeleton filaments into a dynamic structure. Lip to present, pathogenic mutations in FLNB are solely found to cause skeletal deformities, indicating the important role of FLNB in skeletal development. FLNB-related disorders are classified as spondylocarpotarsal synostosis （SCT）, Larsen syndrome （LS）, atelosteogenesis （AO）, boomerang dysplasia （BD）, and isolated congenital talipes equinovarus, presenting with scoliosis, short- limbed dwarfism, clubfoot, joint dislocation and other unique skeletal abnormalities. Several mecha- nisms of FLNB mutations causing skeletal malformations have been proposed, including delay of ossi- fication in long bone growth plate, reduction of bone mineral density （BMD）, dysregulation of muscle differentiation, ossification of intervertebral disc （IVD）, disturbance of proliferation, differentiation and apoptosis in chondrocytes, impairment of angiogenesis, and hypomotility of osteoblast, chondrocyte and fibroblast. Interventions on FLNB-related diseases require prenatal surveillance by sonography, gene testing in high-risk carriers, and proper orthosis or orthopedic surgeries to correct malformations including scoliosis, cervical spine instability, large joint dislocation, and clubfoot. Gene and cell therapies for FLNB-related diseases are also promising but require further studies.

Research on Treatment of Female ldiopathic Precocious Puberty withCombined Traditional Chinese Medicine and Megestrol Acetate

Objective: To find effective therapeutic approach for treating true idiopathic precocious puberty suitable to our national condition and different from gonadotrophin releasing hormone analogue. Methods: One hundred and six girls with idiopathic precocious puberty were divided into 3 groups. The 51 girls in the TCMWM group were treated with Chinese herbal medicine combined with megestrol acetate (MA), 35 girls in the MA group treated with megestrol acetate alone, and 20 girls were taken as control group and given no treatment at all. Luteinizing hormone releasing hormone (LHRH) stimulating test were performed before and after treatment, and the size of the uterus and ovary, linear growth rate, X-ray bone age measurement and final height prediction were also observed simultaneously. Results: After treated with TCM-WM for 2.7 years in average,the luteinizing hormone (LH) peak value of LHRH stimulating test was reduced from 48. 5 ± 5. 2 IU/L to 12.2 ± 1. 3 IU/L, size of uterus and ovary decreased, secondary sexual characteristics regressed, the bone age difference/chronological age difference value (ΔBA/ΔCA) reduced from 1. 35 ± 0. 09 to 0. 65 ± 0. 05 and predictive final height increased from 153. 3 ± 0. 5 cm to 158. 5 ± 0. 6 cm. Conclusion: TCM-WM therapy could not only modulate the function of hypothalamic-pituitary-ovarian axis and the development of internal genitalia, but also could decelerate skeletal growth, delay skeletal maturation, and thereby prevent premature epiphyseal fusion and increase the final height of patients.