title: Development of the articular cavity in the rat temporomandibular joint with special reference to the behavior of endothelial cells and macrophages.
abstract: Previous developmental studies on the temporomandibular joint (TMJ) have proposed several hypotheses on the formation of its articular cavity. However, detailed information is meager. The present study examined the formation process of the articular cavity in the rat TMJ by immunocytochemistry for CD31, RECA-1, and ED1, which are useful cellular markers for endothelial cells and monocyte/macrophage lineages, respectively. The upper articular cavity formation had begun by embryonic day 21 (E21) and was completed at postnatal day 1 (P1) in advance of the lower cavitation; the latter took place from P1 to P3. The occurrence and distribution pattern of the CD31-, RECA-1-, and ED1-positive cells differed between the upper and lower articular cavity-forming areas: the ED1-positive cells exclusively occurred in the area of the prospective upper articular cavity prior to its formation, while no ED1-positive cell appeared in the lower cavity-forming area. In contrast, the CD31- and RECA-1-positive endothelial cells were restricted to the lower cavity-forming area (never the prospective upper cavity) at E19 and diminished thereafter. Throughout the cavity formation, we failed to find any apoptotic cells in the cavity formation area, indicating no involvement of apoptosis in the cavity formation in TMJ. The present findings on the behaviors of endothelial cells and ED1-positive cells show a possibility of different mechanism in the cavity formation between the upper and lower articular cavities in the rat TMJ. The appearance of ED1-reactive cells and temporal vascularization may play crucial roles in the upper and lower articular cavity formation, respectively.
authors.affiliation: Division of Oral Anatomy, Department of Oral Biological Science, Niigata University Graduate School of Medical and Dental Sciences, Niigata, Japan. a-suzuki@dent.niigata-u.ac.jp
authors.forename: Akiko
authors.initials: A
authors.lastname: Suzuki
authors.forename: Kayoko
authors.initials: K
authors.lastname: Nozawa-Inoue
authors.forename: Nobuyuki
authors.initials: N
authors.lastname: Ikeda
authors.forename: Norio
authors.initials: N
authors.lastname: Amizuka
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Ono
authors.forename: Ritsuo
authors.initials: R
authors.lastname: Takagi
authors.forename: Takeyasu
authors.initials: T
authors.lastname: Maeda
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D017209:Apoptosis / Q000502:physiology; D015415:Biomarkers / Q000378:metabolism; D019070:Cell Lineage; D002465:Cell Movement / Q000502:physiology; D047108:Embryonic Development / Q000502:physiology*; D042783:Endothelial Cells / Q000166:cytology* / Q000378:metabolism; D005260:Female; D005865:Gestational Age; D007124:Immunoenzyme Techniques; D020287:In Situ Nick-End Labeling; D008264:Macrophages / Q000166:cytology* / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D013704:Temporomandibular Joint / Q000166:cytology / Q000196:embryology* / Q000254:growth & development*
chemical_list: D015415:Biomarkers