Apr 6, 2000

Transient chondrogenic phase in the intramembranous pathway during normal skeletal development

Journal of Bone and Mineral Research : the Official Journal of the American Society for Bone and Mineral Research
H D NahT Kirsch


Calvarial and facial bones form by intramembranous ossification, in which bone cells arise directly from mesenchyme without an intermediate cartilage anlage. However, a number of studies have reported the emergence of chondrocytes from in vitro calvarial cell or organ cultures and the expression of type II collagen, a cartilage-characteristic marker, in developing calvarial bones. Based on these findings we hypothesized that a covert chondrogenic phase may be an integral part of the normal intramembranous pathway. To test this hypothesis, we analyzed the temporal and spatial expression patterns of cartilage characteristic genes in normal membranous bones from chick embryos at various developmental stages (days 12, 15 and 19). Northern and RNAse protection analyses revealed that embryonic frontal bones expressed not only the type I collagen gene but also a subset of cartilage characteristic genes, types IIA and XI collagen and aggrecan, thus resembling a phenotype of prechondrogenic-condensing mesenchyme. The expression of cartilage-characteristic genes decreased with the progression of bone maturation. Immunohistochemical analyses of developing embryonic chick heads indicated that type II collagen and aggrecan were produced by ...Continue Reading

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Mentioned in this Paper

Biochemical Pathway
Intramembranous Bone Formation
Tissue Membrane
Organ Culture Techniques
Bone Structure of Face
ACAN gene
Alkaline Phosphatase

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