Letter to the Editor concerning “Altered chondrocyte apoptosis status in developmental hip dysplasia in rabbits”

BACKGROUND Developmental dysplasia of the hip (DDH) is an important factor leading to early adult osteoarthritis. Chondrocyte apoptosis has been proven to be an important factor causing osteoarthritis. AIMS The current study aims to explore whether a rabbit model of developmental dysplasia of the hip through cast immobilization in the legs results in chondrocyte apoptosis. STUDY DESIGN Animal experimentation. METHODS Thirty-two New Zealand white rabbits were divided in three groups with cast plaster-induced dislocation at 2, 4 and 6 weeks. The contralateral hip joint was utilized as a control group. Ten rabbits in each group were sacrificed, and hip specimens were obtained. Bcl-2/Bax, cleaved caspase-3 and cleaved caspase-8 expression were examined by western blot analysis. Chondrocyte apoptosis was analyzed through transmission electron microscopy (TEM) and TUNEL analysis. All experiments were repeated at least three times. RESULTS In the experimental group, Bcl-2/Bax, cleaved caspase-3 and cleaved caspase-8 expression were significantly altered. The Bcl-2/Bax ratio decreased with time (all p<0.01), whereas levels of cleaved caspase-3 (p<0.01 and p<0.05) and cleaved caspase-8 (all p<0.05) gradually increased. Chondrocyte apoptosis was observed through transmission electron microscopy (TEM) and TUNEL analysis (p<0.05 at 4 weeks and p<0.01 at 6 weeks). CONCLUSION Prolonged immobilization of rabbit hip caused chondrocyte apoptosis. Reduction of the hip joint may protect chondrocytes from apoptosis, thus preventing secondary osteoarthritis.