Bone Development

Abstract

Early development of the vertebrate skeleton depends on genes that pattern the distribution and proliferation of cells from cranial neural crest, sclerotomes, and lateral plate mesoderm into mesenchymal condensations at sites of future skeletal elements. Within these condensations, cells differentiate to chondrocytes or osteoblasts and form cartilages and bones under the control of various transcription factors. In most of the skeleton, organogenesis results in cartilage models of future bones; in these models cartilage is replaced by bone by the process of endochondral ossification. Lastly, through a controlled process of bone growth and remodeling the final skeleton is shaped and molded. Significant and exciting insights into all aspects of vertebrate skeletal development have been obtained through molecular and genetic studies of animal models and humans with inherited disorders of skeletal morphogenesis, organogenesis, and growth.

Compromised trabecular microarchitecture and lower finite element estimates of radius and tibia bone strength in adults with turner syndrome: A cross-sectional study using high-resolution–pQCT

“…(44) Speculatively, this disorganization may preferentially exert effects on the bone inside, thereby compromising trabecular architecture rather than on the perichondral bone formation that creates a collar of cortical bone. (45) Still, effects on cortical bone were observed in our study, as cortical porosity was lower at both skeletal sites in TS patients compared to controls. Whether this arises during growth or is related to subsequent bone remodeling remains unclear.…”

Growth defect in Grg5 null mice is associated with reduced Ihh signaling in growth plates

“…During embryogenesis, elements in the endochondral skeleton are first patterned as cartilage models (anlagen) by differentiation of chondrocytes within mesenchymal condensations (Erlebacher and Derynck, 1996;Olsen et al, 2000). The anlagen grow and are ossified by a process in which bone and bone marrow replaces cartilage.…”

Indian hedgehog: Its roles and regulation in endochondral bone development

“…Long bones of the limbs as well as the ribs develop by the alternative process known as endochondral ossification. This process involves the formation of a cartilage primodrium and growth plate, where chondrocytes initially undergo proliferation and a series of differentiation steps secreting a cartilage template that is eventually replaced by bone [Olsen et al, 2000].…”

“…Mature chondrocytes express collagen type II and Sox9, and as they reach the prehypertrophic stage, they express PTH/PTHrP receptors (PPR) and Indian hedgehog (Ihh). When they become hypertrophic chondrocytes, the cells express type X collagen and vascular endothelial growth factor (VEGF) [Olsen et al, 2000].…”

“…Coordination of the growth and differentiation of chondrocytes within the growth plate are synchronized with those of the surrounding perichondrium that directly differentiates into osteoblasts (perichondrial bone formation), forming initially the periosteum and later the cortical bone. Perichondrial development, chondrocyte proliferation as well as differentiation all affect bone development, and they must be carefully coordinated by multiple local and systemic factors [Olsen et al, 2000]. This review focuses on the role of one of these factors, Indian hedgehog, in skeletal development.…”