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

1.肾小球细胞表达酪氨酸激酶基因的鉴定与鉴定本研究利用简并引物，从分离的肾小球、培养的肾小球系膜细胞和培养的肾小球内皮细胞制备的信使RNA中，用RT-PCR方法分离和鉴定了酪氨酸激酶基因。对PCR扩增的cDNA进行序列分析，分离出24个酪氨酸激酶。除了已知的7种酪氨酸激酶的表达外，我们还首次发现了15种酪氨酸激酶：tyro-1、tyro-4、tyro-6、Hyk、Ptk-3、Ryk、Tie、YES、Lyn、tec、JAK1、JAK2、JAK3、c-ABL和Flk在肾组织中的结构性表达；2.Flt-1在肾小球系膜细胞中表达的功能我们发现，Flt-1是一种内皮细胞特异性的血管内皮生长因子受体型酪氨酸激酶，在肾小球系膜细胞中表达。我们进一步研究了在PDGF刺激下培养的系膜细胞中它的基因表达，并伴随着VEGFF的上调。这些数据表明，VEGF/Flt-1系统可能参与了细胞因子诱导的系膜细胞增殖。3.新生儿胸腺切除减少了易患IgA肾病的ddy小鼠肾脏的IgA沉积。为了阐明T细胞在ddy小鼠肾脏系膜IgA沉积中的作用，我们研究了新生去胸腺ddy小鼠的IgA沉积。尽管切除胸腺的小鼠发生了与典型的IgAN非常相似的肾脏损害，但它们的系膜IgA沉积程度明显低于对照组假手术小鼠。与对照组相比，胸腺切除组小鼠的脾T细胞百分率和有丝分裂反应量均显著降低。结果表明，胸腺来源的T细胞或其产物决定了ddy小鼠肾脏中IgA的沉积量。

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.