Effects of radiation on chondrocytes in culture

Using an in vitro model, we studied the direct effects of radiation on both DNA and glycosaminoglycan (GAG) synthesis of chondrocytes. Chondrocytes from articular cartilage of 21-day-old rabbits were cultured in monolayer or in pellets with matrix as a three-dimensional tube culture. These cells were exposed to a single dose of X-rays at either 2 or 10 Gy. Following irradiation at 2 Gy, DNA synthesis in the chondrocytes was temporarily suppressed but rapidly returned to the control level, while at 10 Gy, DNA synthesis was markedly suppressed and there was no increase in cell number. On the other hand, GAG synthesis was not affected by a single dose of X-rays at either 2 or 10 Gy, nor did GAG content decrease in the three-dimensional tube cultures. These results show that radiation affects the proliferation and differentiation of chondrocytes differently, and that the synthesis of the components of cartilaginous matrix such as GAG is relatively radioresistant in contrast to DNA synthesis.