A genetic association study between growth differentiation factor 5 ( GDF 5 ) polymorphism and knee osteoarthritis in Thai population
Authors: Tulyapruek Tawonsawatruk (corresponding author) ; Theeraroj Changthong ; Sarinee Pingsuthiwong ; Objoon Trachoo ; Thanyachai Sura ; Wiwat Wajanavisit 
It is widely believed that osteoarthritis develops from an imbalance between anabolic and catabolic processes or homeostasis of cartilage metabolism [1, 2]. The etiology of this disease is related to genetic association . Recently, several studies have demonstrated the polymorphism in many genes which might be related to the pathogenesis of osteoarthritis [4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14]. Growth Differentiation Factor 5 or GDF5 gene regulates the expression of the GDF5 protein which is closely related to BMP and is a member of TGF-beta superfamily . It has a role in regulation of the chondrogenesis and the defect in this gene might be correlated to the abnormal joint development . It has been reported in animal study that GDF5 knockout mice develops knee joint anomaly . Moreover, it has been shown that he polymorphism in GDF5 gene is related with low expression of the GDF5 protein in knee joint .
The large scale analysis has shown that the association of this polymorphism (rs143383 ) in promoter area might be a risk factor of the osteoarthritis . In addition, studies of this genetic variant in China and Japan have shown the association of T allele and knee OA . However, there is a report from Greece which had an inconsistent result and found no an association . The genetic susceptibility of the disease in different ethnic cannot be applied to others because each ethnic has a different genetic background. There is a gap of information about this polymorphism in Thai population, therefore the objective of this study is to determine the association of the SNP rs143383 in GDF5 gene and knee OA in Thai population.
Patients and Methods
Our study was approved by the Ethics Committee of the Faculty of Medicine, Ramathibodi Hospital, Mahidol University, Bangkok, Thailand. All patients recruited in the study were Thai by nationality and had ancestors settled in Thailand for at least three generations. In total, 90 patients with knee OA who underwent total knee arthroplasty (TKA) and 103 patients without knee OA were enrolled from Department of Orthopedics, Ramathibodi Hospital. Informed consent was performed after the purpose of the research project and it had been clearly explained to the patients. The diagnosis of knee OA was based on the American College of Rheumatology criteria . Both OA and control groups were interviewed to obtain demographic data and all of established risk factors. Thereafter, standard weight-bearing antero-posterior and lateral view of knee radiographs were taken to confirm the diagnosis of OA by Kellgren and Lawrence scores (KL scores) .
PCR-RFLP for BsiEI restriction site was used for SNP in GDF-5 identification
Firstly, 5 ml peripheral blood sample was collected from patient using ethylenediamine tetraacetic acid as an anticoagulant and processed for SNP analysis. Genomic DNA was extracted from buffy coat leukocytes using the standard phenol-chloroform method. PCR...
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