2020 Volume 48 Issue 1 Pages 15-30
Individuals exhibiting dwarfism with shortened limbs appeared in a colony of Sprague-Dawley rat strains maintained at the Institute for Animal Experimentation, St. Marianna University Graduate School of Medicine. Rats with dwarfism were identified as having insufficient calcification during bone growth due to endochondral ossification and named “cartilage calcification insufficient (CCI) rats.” The expression of FGF18 mRNA in CCI rat growth plates was significantly higher than that in normal rats, whereas the expression of Ihh, osteopontin, osteocalcin, bone-type alkaline phosphatase (BAP) and dentin matrix protein-1 mRNA was significantly lower. From these results, it has been speculated that the increased expression of FGF18 in the growth plate suppressed Ihh expression, causing suppression of the expression of the calcification factors osteocalcin and BAP and resulting in calcification failure, which potentially might have contributed to abnormalities in endochondral ossification in CCI rats. Based on these facts, CCI rats are expected to be useful disease model animals for studying bone system diseases exhibiting short-limbed dwarfism, such as achondrogenesis and hypochondrosis. Furthermore, cartilage and bone formation involves a large number of bioactive factors, so CCI rats exhibiting insufficient cartilage calcification in the cartilage growth plate are considered to be useful experimental animals for elucidating the factors involved in cartilage and bone formation and the mechanisms thereof.
