Making and shaping endochondral and intramembranous bones

Abstract

Skeletal elements have a diverse range of shapes and sizes specialized to their various roles including protecting internal organs, locomotion, feeding, hearing, and vocalization. The precise positioning, size, and shape of skeletal elements is therefore critical for their function. During embryonic development, bone forms by endochondral or intramembranous ossification and can arise from the paraxial and lateral plate mesoderm or neural crest. This review describes inductive mechanisms to position and pattern bones within the developing embryo, compares and contrasts the intrinsic vs extrinsic mechanisms of endochondral and intramembranous skeletal development, and details known cellular processes that precisely determine skeletal shape and size. Key cellular mechanisms are employed at distinct stages of ossification, many of which occur in response to mechanical cues (eg, joint formation) or preempting future load‐bearing requirements. Rapid shape changes occur during cellular condensation and template establishment. Specialized cellular behaviors, such as chondrocyte hypertrophy in endochondral bone and secondary cartilage on intramembranous bones, also dramatically change template shape. Once ossification is complete, bone shape undergoes functional adaptation through (re)modeling. We also highlight how alterations in these cellular processes contribute to evolutionary change and how differences in the embryonic origin of bones can influence postnatal bone repair.

Allogeneic vs. autologous mesenchymal stem/stromal cells in their medication practice

“…MSCs, as the precursors of osteoblasts, have the potential of osteogenesis and chondrogenesis and, consequently, such cells can contribute to bone remodeling. Osteoclasts are derived from the haematopoietic lineage [ 132 , 134 ], likely to initially arise from the yolk sac [ 135 ]. Dysregulation of bone homeostasis has been linked to age-related bone loss, especially in postmenopausal women [ 133 , 134 , 136 ], potentially leading to osteoporosis.…”

“…Dysregulation of bone homeostasis has been linked to age-related bone loss, especially in postmenopausal women [ 133 , 134 , 136 ], potentially leading to osteoporosis. During skeletal development, bone formation appears to be in two distinct processes: intramembranous and endochondral ossification involved complex multiple signaling pathways [ 134 , 135 , 137 ]. Intramembranous ossification occurs via direct osteoblast differentiation in the absence of a cartilage structure while endochondral ossification is involved in the formation of cartilage tissue and subsequent replacement of this cartilage with mineralized bone [ 134 , 135 , 137 , 138 ].…”

“…During skeletal development, bone formation appears to be in two distinct processes: intramembranous and endochondral ossification involved complex multiple signaling pathways [ 134 , 135 , 137 ]. Intramembranous ossification occurs via direct osteoblast differentiation in the absence of a cartilage structure while endochondral ossification is involved in the formation of cartilage tissue and subsequent replacement of this cartilage with mineralized bone [ 134 , 135 , 137 , 138 ]. The vascular invasion by different mechanisms during intramembranous and endochondral ossification has been documented by multiple studies [ 139 – 141 ].…”

The periosteum: a simple tissue with many faces, with special reference to the antler-lineage periostea

“…From a histological perspective, the healing of a cranial neural crest-derived skeletal element is no different from healing in a mesoderm-derived element. Both can contribute to both endochondral and intramembranous bones [ 64 ]. The PDCs, however, have ‘positional memory’, which influences how the cells behave when grafted into ectopic locations.…”

BMP signaling and skeletal development in fibrodysplasia ossificans progressiva (FOP)

“…Figure 2: Altered hindlimb digit patterning due to mutations in the BMP signaling pathway.Schematic drawings illustrate key features of human (A-D) and mouse (E-H) digits. (A)The typical arrangement of human feet includes five digits(1)(2)(3)(4)(5). The first digit only has three primary ossification centers (POCs; white), which give rise to one metatarsal (mt) and two phalanges (p1 and p2), whereas digits 2-5 have a metatarsal and three phalanges each (p1-p3).…”