D. Leguellec et al., LOCALIZATION OF THE EXPRESSION OF TYPE-I, TYPE-II AND TYPE-III COLLAGEN GENES IN HUMAN NORMAL AND HYPOCHONDROGENESIS CARTILAGE CANALS, Histochemical Journal, 26(9), 1994, pp. 695-704
The expression of type I, II and III collagens genes was examined in h
uman normal and hypochondrogenesis cartilage canals employing electrop
horetic analysis, immunohistochemistry and in sih hybridization techni
ques. In normal cartilage, collagens type I and III were present in pe
richondrium, in the connective tissue surrounding the vessels of carti
lage canals and in the dense fibrous tissue. However, types I and III
procollagen mRNAs were detected only in fibroblasts of the perichondri
um and of the canals, but not in the polymorphic cells. Type II collag
en was present in the cartilage matrix and in the dense fibrous tissue
, in good accordance with the localization of type II procollagen mRNA
s detected in the chondrocytes and in the polymorphic cells. These dat
a suggest that there are no transitional cells expressing type I, II a
nd III collagen genes and that polymorphic cells are of chondrocytic o
rigin. In the case of hypochondrogenesis, type II collagen was less ab
undant than in normal cartilage, whereas the corresponding mRNA level
was equivalent. That suggests that a postranscriptional regulation of
this protein is involved in the decrease of type II collagen productio
n. Type I collagen, unexpectedly detected in the cartilage matrix, was
synthesized by chondrocytes and polymorphic cells, suggesting a repla
cement of type II by type I collagen. The canal hypertrophy observed i
n this pathological case could thus be due to a modification in the re
gulation of the growth of cartilage canals caused by a defective carti
lage matrix.