Association of vitamin D receptor gene polymorphisms with end-stage renal disease and the development of high-turnover renal osteodystrophy in a Chinese population

Two single nucleotide polymorphisms (SNPs; TaqI and ApaI) in the vitamin D receptor (VDR) gene have been identified as risk factors for the progression of end-stage renal disease (ESRD). The purpose of our study was to confirm the reported association of these two SNPs with ESRD risk and progression of renal osteodystrophy in a Chinese Han population. A total of 452 ESRD patients and 904 matched-pair controls (based on age, gender, and body mass index) were included. Identification of VDR gene polymorphisms was performed using the polymerase chain reaction-restriction fragment length polymorphism method with TaqI and ApaI restriction enzymes. There was no association of the TaqI polymorphism with ESRD risk. However, significant associations were seen between ApaI (rs7975232) polymorphism and ESRD risk in the heterozygote model (AC/ AA; P = 0.002; OR = 1.4, 95%CI = 1.14-1.83), homozygote model (CC/AA; P = 0.007; OR = 1.8, 95%CI = 1.17-2.85) genotypes for rs7975232, allelic model (P < 0.001; OR = 1.4, 95%CI = 1.15-1.64), dominant model (P = 0.001; OR = 1.5, 95%CI = 1.19-1.87), and recessive model (P = 0.046; OR = 0.6, 95%CI = 0.42-1.00) between cases and healthy controls Moreover, we found a significant correlation between the genotype and allele distribution of ApaI and intact parathyroid hormone (iPTH) levels, where allele C carriers have increased iPTH levels. The ApaI polymorphism in the VDR gene appears to be a susceptibility locus for ESRD in Chinese individuals, and allele C carriers may have an increased risk of high-turnover renal osteodystrophy.

Effects of lipopolysaccharides stimulated Kupffer cells on activation of rat hepatic stellate cells

AIM: To study the effects of Kupffer cell-conditioned medium (KCCM) derived from lipopolysaccharide (LPS) treatment on proliferation of rat hepatic stellate cells (HSC).

METHODS: HSC and Kupffer cells were isolated from the liver of Wistar rats by in situ perfusion with pronase and collagenase and density gradient centrifugation with Nycodenz and cultured. KCCM was prepared and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) colorimetric assay was used to detect HSC proliferation. The content of type IV collagen and laminin secreted by HSC in the HSC-conditioned medium was determined by radioimmunoassay. TGF-β₁ production in the KCCM was detected by enzyme-linked immunosorbent assay (ELISA).

RESULTS: HSC and Kupffer cells isolated had high purity. One microgram per mililiter LPS-activated KCCM and unstimulated KCCM could significantly promote HSC proliferation [0.132 ± 0.005 and 0.123 ± 0.008 vs control group (0.100 ± 0.003), P < 0.01], and there was a difference between them (P < 0.05). Ten microgram per mililiter LPS-activated KCCM (0.106 ± 0.010) was unable to promote HSC proliferation (P > 0.05). Adding anti-TGF-β₁ antibodies could suppress the proliferation promoted by unstimulated KCCM and LPS (1 μg/ml)-activated KCCM (0.109 ± 0.009 vs 0.123 ± 0.008, 0.115 ± 0.008 vs 0.132 ± 0.005, P < 0.01). LPS (1 μg/ml or 10 μg/ml) could not promote HSC proliferation immediately (0.096 ± 0.003 and 0.101 ± 0.004 vs 0.100 ± 0.003, P > 0.05). There was a parallel behavior between HSC proliferation and increased ECM level. One microgram per mililiter LPS-activated KCCM contained a larger amount of TGF-β₁ than unstimulated KCCM.

CONCLUSION: The technique for isolation of HSC and Kupffer cells described here is simple and reliable. KCCM stimulated by LPS may promote HSC proliferation and collagen accumulation, which are associated with hepatic fibrogenesis.