EXPRESSION OF BASEMENT-MEMBRANE TYPE-IV COLLAGEN AND TYPE-IV COLLAGENASES (MMP-2 AND MMP-9) IN HUMAN FETAL TEETH

Formation and degradation of dental basement membrane (BM) are importa nt for tooth development. Data on the expression of genes for type TV collagen (the major structural component of the BM) and type N collage nases [MMP-2 (72 kDa) and MMP-9 (92 kDa)], enzymes that degrade type I V collagen during human tooth development, are lacking. We studied exp ression of type IV collagen and the MMP-2 and MMP-9 in human fetal tee th (from the 13th to the 20th gestational weeks, covering cap stage th rough early hard tissue formation). During cap and bell stages, in sit u hybridization located transcripts for al type IV collagen chain in t he fibroblasts surrounding the enamel organ. No alpha 1 type IV collag en chain mRNA was detected in tooth germ epithelium or dental papilla. However, type TV collagen immunoreactivity was observed in BM underly ing the dental epithelium up to the appositional stage. Transcripts fo r MMP-2 were located mostly in the cells of the dental papilla and fol licle. Transient expression of MMP-2 mRNA was observed in the inner en amel epithelium of late cap/early bell-stage teeth, During early appos ition, a high level of MMP-2 was confined to secretory odontoblasts. T ranscripts for MMP-9 were detected by the sensitive reverse-transcript ion polymerase chain reaction (RT-PCR) in developing teeth. Thus, in d ental BM, alpha 1 type N collagen chain may be of mesenchymal cell ori gin. Further, MMP-2 but not MMP-9 may participate in remodeling and de gradation of BM during human tooth morphogenesis.