Therapeutic Potential of Anti-Midkine Therapy in Progressive Renal Diseases

为了阐明中期因子(MK)作为预防进展性肾脏疾病的候选分子靶点的潜力，进行了以下实验：(1)MK反义寡核苷酸(ODN)在几种肾脏损伤动物模型中的抑制作用，如肾缺血再灌注损伤，(2)MCP-1和MIP-2在体外培养的肾小球系膜细胞和肾小管上皮细胞中表达的信号通路。(3)DNA末端分析MK刺激后上调或下调的基因的表达谱。结果(1)静脉注射MK反义寡核苷酸后，MK反义寡核苷酸优先整合到肾脏近端小管，并显著抑制近端小管MK的表达。在STZ诱导的DM模型中，肾小球MK的表达增加，MK基因敲除小鼠肾小球硬化程度明显减轻，说明MK参与了糖尿病肾硬化的过程。进一步研究表明，MK通过激活PKCb和Ark，促进肾小球巨噬细胞内流，参与肾小球硬化的形成。(3)DM患者尿MK排泄量与DM肾病病理分期密切相关，提示MK作为肾脏疾病分子靶点的候选具有重要的临床应用价值。MK及其受体(LRP和megalin)的信号通路对于抗MK治疗的临床应用具有重要意义。

The following experiments have been performed in order to clarify the potential of midkine(MK) as a candidate of molecular target for the prevention of progressive renal diseases.(1)The inhibitory effects of MK antisense oligodeoxinucleotide(ODN) "in vivo" in sevelal animal models of renal injuries, such as ischemic renal reperfusion injury, cysplatin nephropathy and STZ induced DM model.(2)The signal pathway of MK-dependent expression of MCP-1 and MIP-2 in cultured mesangial cells and renal tubular epithelial cells.(3)The profile of the genes which are up-regulated or down-regulated after stimulation with MK by DNA tip analysis.RESULTS(1)Intravenous injection of MK antisense-ODN preferentially incorporated in the proximal tubules in the kidney, and significantly inhibited the expression of MK in the proximal tubules. Furthermore, MK antisense-ODN successfully inhibited the process of progressive renal injuries in ischemic renal reperfusion injury, and cysplatin nephropathy.(2)In STZ induced DM model, expression of MK in glomeruli was increased The level of glomerular sclerosis which was prominent in wild type mice was much less in MK knockout mice, showing that MK involves in the process of diabetic nephrosclerosis. Further studies showed that MK contributes to the glomerular sclerosis by activation of PKCb and ARK, and by enhancement of macrophage influx in glomeruli.(3)The urinary excretion of MK in DM patients was well correlated with the pathological stage of DM nephropathy.These results strongly suggest the prominent potential of MK as a candidate of molecular target for the prevention of progressive renal diseases. The signal pathway through MK and its receptors (LRP and Megalin) would be important for the clinical application of anti-MK therapy.