title: Complement proteins are present in developing endochondral bone and may mediate cartilage cell death and vascularization.
abstract: Normal endochondral bone formation follows a temporal sequence: immature or resting chondrocytes move away from the resting zone, proliferate, flatten, become arranged into columns, and finally become hypertrophic, disintegrate, and are replaced by bone. The mechanisms that guide this process are incompletely understood, but they include programmed cell death, a stage important in development and some disease processes. Using immunofluorescence we have studied the distribution of various complement proteins to examine the hypothesis that this sequence of events, particularly cell disintegration and matrix dissolution, are complement mediated. The results of these studies show that complement proteins C3 and Factor B are distributed uniformly in the resting and proliferating zones. Properdin is localized in the resting and hypertrophic zone but not in the proliferating zone. Complement proteins C5 and C9 are localized exclusively in the hypertrophic zones. This anatomically segregated pattern of distribution suggests that complement proteins may be important in cartilage-bone transformation and that the alternate pathway is involved.
authors.affiliation: Division of Surgical Research, Children's Hospital Los Angeles, University of Southern California 90027, USA.
authors.forename: J A
authors.initials: JA
authors.lastname: Andrades
authors.forename: M E
authors.initials: ME
authors.lastname: Nimni
authors.forename: J
authors.initials: J
authors.lastname: Becerra
authors.forename: R
authors.initials: R
authors.lastname: Eisenstein
authors.forename: M
authors.initials: M
authors.lastname: Davis
authors.forename: N
authors.initials: N
authors.lastname: Sorgente
mesh_terms: D000818:Animals; D015415:Biomarkers; D001846:Bone Development / Q000502:physiology*; D002356:Cartilage / Q000098:blood supply / Q000737:chemistry* / Q000166:cytology*; D016923:Cell Death / Q000502:physiology; D003176:Complement C3 / Q000032:analysis / Q000502:physiology; D003182:Complement C5 / Q000032:analysis / Q000502:physiology; D003186:Complement C9 / Q000032:analysis / Q000502:physiology; D011415:Complement Factor B / Q000032:analysis / Q000502:physiology; D003165:Complement System Proteins / Q000032:analysis / Q000502:physiology*; D005269:Femur / Q000098:blood supply / Q000737:chemistry / Q000196:embryology; D005333:Fetus / Q000737:chemistry; D005455:Fluorescent Antibody Technique; D011414:Properdin / Q000032:analysis / Q000502:physiology; D051381:Rats; D011916:Rats, Inbred F344; D013977:Tibia / Q000098:blood supply / Q000737:chemistry / Q000196:embryology
chemical_list: D015415:Biomarkers; D003176:Complement C3; D003182:Complement C5; D003186:Complement C9; D011414:Properdin; D003165:Complement System Proteins; D011415:Complement Factor B