Abstract
The temporomandibular joint (TMJ) is a multicomponent organ including the condyle, mandibular fossa, articular disc and clefts, and surrounding tissues. In the present study, we reported the chronology of TMJ development and associated tissue-marker expression in C57BL/6 mice. Wild-type mice of embryonic day 12.5 (E12.5) through postnatal day 7 were examined by histochemistry (HE, metachromasia by toluidine blue), enzyme-histochemistry for alkaline and acid phosphatases (ALP and TRAP) and immunohistochemistry for BrdU and type II collagen. The results confirmed that: 1) the condylar blastema was first designated as a troop of ALP-positive cells at E13.5, and some of those cells also displayed BrdU incorporation, 2) after differentiation of the blastema, condylar morphogenesis progressed from the anterior to the posterior direction, while the mandibular fossa of discrete origin developed inversely, and 3) development of the articular disk and superior/inferior clefts appeared to link intimately with the articular function. Histomorphometric analysis, in conjunction with BrdU administration, further revealed that condylar growth during development can be divided into three stages: the initial slow growth due to cell proliferation by E13.5, the second rapid growth between E14.5 and E17.5 due to production of extracellular matrices instead of acceleration of cell proliferation, and the last functional adaptation after birth that progresses at a steady growth rate coupled with systemic body growth. The current observation also supported the spatial linkage of the condylar blastema with a group of the mesenchymal cell population that is involved in mandibular bone development. Further analysis in conjunction with three-dimensional reconstruction of ALP-positive cell condensation is required to clarify the origin and spatio-temporal development of condylar blastema in detail.
Published Version
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