[Identification of differentially expressed genes in rats and preliminary analysis in regression of vascular calcification].

Objective: To investigate the differentially expressed genes in rat in the process of regression of vascular calcification by using the suppression subtractive hybridization (SSH).

Methods: 24 SD male rats which aged 6 weeks and specific pathogen free grade were selected and randomly divided into 3 groups (n = 8): control group, calcification group and regression group respectively. Vascular calcification model (vitamin D3 plus nicotine, VDN) were made from rats in calcification group and regression group, and rats in control group were intragastric administered with normal saline and lavaged with peanut oil. Rats were bred for 8 weeks in calcification group and control group, while rats in regression group were fed for 16 weeks. All rats were killed to measure concentration of calcium in the arterial tissue and examine the pathological lesion changes. Subtractive hybridization among vascular cDNA sequences from calcification group and regression group were established. The cDNA fragments which expressed higher or lower in regression group than those in calcification group were isolated. Differentially expressed genes with cDNA fragment were inserted into PMD18-T plasmid vector and transformed competent DH-5alpha, cDNA libraries of differentially expressed gene between calcification group and regression group were then constructed. Recombinant vectors were analyzed by colony PCR, positive genes were randomly selected for sequencing and analyzed by BLAST. 4 genes were randomly selected for RT-PCR certification combined with semi-quantitative analysis of DNA bands.

Results: VDN model of rats were successfully constructed. Concentration of tissue calcium in calcification group (15.34 mg/g +/- 2.51 mg/g) was significantly increased compared to that in control group (5.20 mg/g +/- 0.75 mg/g, P < 0.001), while in comparison with calcification group (15.34 mg/g +/- 2.51 mg/g), calcium in regression group was relatively lower (12.73 mg/g +/- 1.89 mg/g, P < 0.05). 28 up-regulated genes and 22 down-regulated genes were gained through sequencing and BLAST analysis among positive clones. RT-PCR validation indicated that 4 genes such as prdx3 and Ank2 had increasedly expressed in regression group than those in calcification group, the average fold change was 1.7.

Conclusion: Rat vascular calcification tissue had characteristic of active regression. Genes in relation to pyrophosphoric acid synthesis, glutamate signal peptides, anti-oxidant and ant-apoptosis were up-regulated, at the same time many genes related to ossification and oxidation activity were down-regulated in the process of calcification regression. Increased expression of calcification suppressor genes accompanying decreased expression of calcification promoting genes might be the intrinsic mechanisms which initiated the active regression of calcified tissues.