Molecular mechanisms on the mesangial cell activation by IgA nephropathy-associated antigens.

1.肾小球细胞中酪氨酸激酶表达的鉴定和特征我们从分离的肾小球、培养的系膜细胞和培养的肾小球内皮细胞中提取信使RNA，用简并引物通过RT-PCR分离并鉴定酪氨酸激酶基因。PCR扩增的cDNA序列分析导致24个酪氨酸激酶的分离。我们首次发现了15种酪氨酸激酶在肾小球中的组成性表达，它们是：tyro-1、tyro-4、tyro-6、hyk、Ptk-3、Ryk、tie、yes、lyn、tec、Jak 1、Jak 2、Jak 3、c-abl和flk，以及先前已知的7种酪氨酸激酶在肾脏中的表达; IGFR、Trk B、PDGFR、Flt-1、Flk-1、bFGFR和Ufo. 2. Flt-1在肾小球系膜细胞中表达的功能研究我们进一步研究了PDGF刺激时VEGF在系膜细胞中的表达，这些数据提示VEGF/Flt-1系统可能参与了姜黄素诱导的系膜细胞增殖。3.新生胸腺切除减少了IgA肾病易感ddY小鼠肾脏中的IgA沉积。我们研究了切除胸腺的ddY小鼠的IgA沉积。虽然胸腺切除小鼠的肾脏病变非常相似，典型的IgAN，其肾小球系膜IgA沉积的程度显着比对照假手术小鼠温和。与对照组相比，胸腺切除小鼠脾脏T细胞百分比和促有丝分裂反应的幅度均显著降低。结果表明，胸腺衍生的T细胞或其产物决定ddY小鼠肾脏中IgA沉积的量。

1. Identification and characterization of tyrosine kinases expressed in glomerular cells.We isolated and identified the tyrosine kinase genes by RT-PCR with degenerate primers from messenger RNA prepared from isolated glomeruli, cultured mesangial cells and cultured glomerular endthelial cells. Sequence analysis of PCR-amplified cDNAs resulted in the isolation of 24 tyrosine kinases. We showed for the first time the constitutive expression of 15 tyrosine kinases ; tyro-1, tyro-4, tyro-6, hyk, Ptk-3, Ryk, tie, yes, lyn, tec, Jak1, Jak2, Jak3, c-abl, and flk, in renal glomeruliin addition to the previously known renal expressions of 7 tyrosine kinases ; IGFR,Trk B,PDGFR,Flt-1, Flk-1, bFGFR,and Ufo.2.Functional role of Flt-1 expressed in glomerular mesangial cells.We showed that, Flt-1, an endothelial cell-specific receptor-type tyrosine kinase for vascular endotherial growth factor (VEGF), is expressed in renal mesangial cells. We further investigated its gene expression in cultured mesangial cells upon the stimulation of PDGF with the concomitant up-regulation of VEGF.These data suggest the possible involvement of VEGF/Flt-1 system in cytokine-induced mesangial cell proliferations.3.Neonatal thymectomy diminished renal IgA deposition in IgA nephropathy-prone ddY mice.To clarify the role of T cells on mesangial IgA deposition in the kidney of ddY mice, we investigated the IgA deposition in neonatally thymectomized ddY mice. Although the thymectomized mice developed a renal lesion closely resembling that typical of IgAN,the extent of their mesangial IgA deposition was significantly milder than in control sham-operated mice. The percentage of splenic T cells and the magnitude of mitogenic responses both decreased markedly in thymectomized compared with control mice. The results suggest that thymus-derived T cells or their products determine the amount of IgA deposition in the kidney of ddY mice.