LABORATORY AND ANIMAL STUDIES

PPARg2 Expression in Osteonecrosis of the Femoral Head
JS Chang1, JH Park1, HC Shon1, JH Kim2
1Department of Orthopaedic Surgery, Ulsan University, Asan Medical center, Seoul, Korea, and 2Asan Institute for Life Science, Ulsan, Korea

Hyperlipidemia is related to hypercoagulability and hypofibrinolysis, which may cause a tendency to intravascular thrombosis and result in Osteonecrosis (ON). Recently PPARs were confirmed to induce adipocyte differentiation, and fatty acids were identified as the transcriptional effectors for PPARs, and may cause the hyperlipidemia and fatty marrow. And this study was aimed to identify whether the adipocytic differentiation was increased in the bone marrow of the osteonecrosis.

Firstly, we've analyzed lipid profile (cholesterol, Triglyceride, LDL, and free fatty acid) of the patients with osteonecrosis of the femoral head. Among 89 cases of Osteonecrosis, increased free fatty acid (above 580mg%) was the most frequent finding (40.8%), and Triglyceride was the next (29.6%). Cholesterol was increased only in 9.0%. And the PPARg2 expression was checked whether the mesenchymal stem cells differentiate toward adipocytes rather than osteogenic cells. RT-PCRs were done from the bone marrow stroma cells obtained during THA from 11 patients of osteonecrosis and control 9 patients. 7cases (63.6%) of Osteonecrosis and 4cases (44.4%) in control express PPARg2.

As not all of alcoholics and steroid users develop osteonecrosis, genetic differences which may relate to susceptibility to the osteonecrosis, and we studied polymorphism of PPARg2 gene for 34 osteonecrosis patients and 76 controls. And Pro/Ala(C/G) polymorphism was found in 7 cases (20.6%) of ON and 4 cases (5.3%) of control group, and Ala/Ala (G/G) polymorphism was found only 1 case in control group. And numbers of the patients with elevated triglyceride among osteonecrosis were much higher (71.4%) in polymorphism(C/G) than osteonecrosis (21.5%) without polymorphism.
In conclusion, hyperlipidemia and higher expression of the PPARg2 were found in ON, and Pro/Ala PPARg2 polymorphism was more common in ON.