Effects of X-ray irradiation on terminal differentiation and cartilage matrix calcification of rabbit growth plate chondrocytes in culture.
The retardation of long bone growth caused by irradiation is thought to be closely related to the impairment of growth plate function, but its mechanism remains unclear. In this study, we examined the effects of irradiation on the terminal differentiation of growth plate chondrocytes and on calcification. Chondrocytes were isolated from the growth plate of the ribs of four-week-old rabbits and inoculated at a high density on a type-I collagen-coated dish. Following logarithmic proliferation, they reached confluence (premature chondrocytes), then matured (mature chondrocytes), and became hypertrophied (hypertrophic chondrocytes). 10 Gy or less irradiation of the premature chondrocytes potently inhibited the terminal differentiation and matrix mineralization. Irradiation inhibited chondrocyte hypertrophy and suppressed alkaline phosphatase induction and the expression of type-X collagen without changing the protein composition profile of any other cell layer. Premature cells had the highest radiosensitivity. The sensitivity was decreased as the cells differentiated; the effects of irradiation on hypertrophic chondrocytes with terminal differentiation-related phenotypes were reduced. This study showed that 10 Gy or less irradiation of growth plate chondrocytes impaired terminal differentiation and mineralization. Since chondroclasts and bone marrow cells invade only to the mineralized cartilage, the induction of calcification in cartilage matrices is one of the most important steps in endochondral ossification. Therefore, it is conceivable that the damage in the growth plate induced by irradiation could account for the subsequent abnormal bone and skeletal growth.
Hiranuma
H
H
Department of Oral and Maxillofacial Radiology, Faculty of Dentistry, Osaka University, Japan.
Jikko
A
A
Iwamoto
M
M
Fuchihata
H
H
D000469:Alkaline Phosphatase / Q000378:metabolism; D000818:Animals; D000831:Animals, Newborn; D000880:Anthraquinones / Q000737:chemistry; D001854:Bone Marrow Cells; D002113:Calcification, Physiologic / Q000528:radiation effects*; D002118:Calcium / Q000378:metabolism; D002454:Cell Differentiation / Q000528:radiation effects; D002455:Cell Division / Q000528:radiation effects; D002478:Cells, Cultured; D003094:Collagen / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D004247:DNA / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D018507:Gene Expression Regulation, Developmental / Q000235:genetics / Q000528:radiation effects; D006132:Growth Plate / Q000166:cytology / Q000528:radiation effects*; D008297:Male; D011817:Rabbits; D012272:Ribs / Q000166:cytology / Q000528:radiation effects; D014965:X-Rays / Q000009:adverse effects
D000880:Anthraquinones; C010078:alizarin; D003094:Collagen; D004247:DNA; D000469:Alkaline Phosphatase; D002118:Calcium