Polymorphism in rs2229783 of the Alpha 1(XI(4)

KBD was diagnosed according to the national diagnostic criteria of China (WS/T 207-2010). Patients with clinical symptoms, radiographic changes, or other osteochondropathies were excluded. A healthy control was defined as no KBD and no primary or secondary OA. A total of 274 KBD patients and 249 age- (53.37 ± 10.79 ± 17.85 years,t= 1.27,P> 0.05) and sex-matched (male/female, 125//125,χ2= 0.91,P> 0.05) controls were collected from KBD-endemic areas of the Linyou and Yongshou Counties of Shaanxi Province. In addition, the 274 KBD patients were classified as clinical stages I, II, and III, which comprised 57.66% (158/274), 31.02% (85/274), and 11.32% (31/274) of the total, respectively. Fresh blood (5 mL) was collected from each subject.

Knee articular cartilage was collected from 22 KBD patients and 21 healthy controls. The KBD patients, consisting of 10 males and 12 females with an average age of 51.00 ± 8.30 (32-66) years, underwent knee debridement or arthroplasty at a hospital. The healthy control subjects, consisting of 11 males and 10 females with an average age of 48.23 ± 7.65 (33-61) years, had no history of osteochondropathy, but they had undergone amputation because of traffic accidents. No significant differences were observed between KBD and control group in age (t= 1.13,P> 0.05) and sex (χ2= 0.21,P> 0.05). None of the KBD patients or controls were diagnosed with bone or cartilage genetic diseases or RA.

The study was performed in accordance with the Declaration of Helsinki and approved by the Human Ethics Committee of Xi’an Jiaotong University, China. Written informed consent was also obtained from the subjects or their relatives.

Based on the available information on SNPs inCOL11A1 that are considered predisposing factors in osteochondropathy[7-8], 22 SNPs were selected from the NCBI SNP and HapMap database and evaluated in this study. The selected SNPs were required to have a minor allele frequency (MAF) ≥ 5%. Genomic DNA was extracted from the peripheral blood of the 274 KBD patients and 249 healthy controls using a blood DNA extraction kit (TIANGEN, Beijing, China). Genotyping was performed using the Sequenom MassARRAY system. Primers were designed using Sequenom SNP Assay Design software version 3.0 for iPLEX reactions. The protocol and reaction conditions were as outlined by the manufacturer. Data management and analysis were conducted by Sequenom Typer 4.0 Software (

Following collection, the cartilage tissues were immediately ?xed in 4% (w/v) paraformaldehyde, washed in phosphate-buffered saline (PBS), decalcified, embedded in paraffin, and cut into 5-8-μm-thick slices for immunohistochemistry and hematoxylin and eosin (HE) staining. Immunochemical identification was performed using the streptavidin-peroxidase (SP) method. Briefly, after deparaffinization, endogenous peroxidase was blocked with 3% H2O2for 15 min, after which the slides were washed with PBS. The slides were then predigested using a digestive complex followed by rinsing with PBS. After blocking using 10% normal goat serum, the sections were incubated with a primary antibody recognizing COL11A at a 1:100 dilution (polyclonal rabbit anti-COL11A, Bioss Co, Beijing, China) or with PBS as a negative control, at 4 °C overnight. Next, the sections were incubated with 1:200 biotinylated goat anti-rabbit IgG (ZSGB-Bio Co, Beijing, China) at 37 °C for 20 min, followed by incubation with horseradish peroxidase-labeled streptavidin solution at 37 °C for 15 min. Color development was continued for 5 min at room temperature using diaminobenzidine followed by rinsing with distilled water. Counterstaining was performed with hematoxylin. The positive cells were counted at 40× magnification in six randomly selected fields; an average of six fields was observed for each tissue. A comparison of the positive rate of COL11A-stained cells between the two groups showed that the percentage of stained cells in the KBD group was 18.53% ± 8.41%, significantly lower than that of 26.58% ± 11.47% in the controls (t= 2.637,P< 0.05).

The Hardy-Weinberg equilibrium (HWE) of each SNP was tested by the goodness-of-?tχ2test to compare the expected and observed genotype frequencies in the control group; SNPs withP> 0.05 were considered to be in HWE. An unconditional logistic regression analysis model was used to evaluate the relationships between different genotypes and disease risk [odds ratios(OR), 95% confidence intervals (95%CI)] adjusted by age and gender[9]. To account for multiple testing, a Bonferroni correction was applied, and a significant association was defined atP< 0.002 (0.05/22)[9].

A case-control comparison of both genotype and allele frequencies for the 22 SNPs is presented in Table 1. All tested SNPs were in HWE (P= ). When the allele frequencies were compared between the KBD patients and controls, a significantχ2value was detected for rs (P= 0.006). The distribution frequencies of rs genotypes was significantly different between the two groups (P =0.0003). However, the significant association of allele frequency of rs did not persist following Bonferroni correction (P> 0.002).

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