Dysregulated mesenchymal PDGFR-β drives kidney fibrosis. Dysregulated mesenchymal PDGFR-β drives kidney fibrosis

Kidney fibrosis is characterized by expansion and activation of platelet-derived growth factor receptor-β (PDGFR-β) positive mesenchymal cells. To study the consequences of PDGFR-ß activation, we developed a model of primary renal fibrosis using transgenic mice with PDGFR-β activation specifically in renal mesenchymal cells, driving their pathological proliferation and phenotypic switch towards myofibroblasts. This resulted in progressive mesangioproliferative glomerulonephritis, mesangial sclerosis and interstitial fibrosis with progressive anemia due to loss of erythropoietin production by fibroblasts. We used microarrays to compare wildtype animals (Foxd1_wt Pdgfrb_wt) to animals with constitutive mesenchymal PDGFR-β activation (Foxd1_mt Pdgfrb V536A) in the kidney to identify target genes of PDGFR-β signaling. Overall design: To generate mice with a renal mesenchymal cell-specific, constitutively active PDGFR-β (Foxd1_mt Pdgfrb V536A), we used mice in which one wt Pdgfrb allele was substituted by a conditional knock-in of Pdgfrb with an activating point mutation (V536A) in the juxtamembrane domain of PDGFR-β, behind a floxed STOP cassette. Expression of the mutated Receptor occurs after Cre-recombinase excision. Cre-recombinase expression occurs under the FoxD1-promoter, which is active in renal mesenchymal precursors during development. Foxd1_mt Pdgfrb V536A mice were compared to wildtype littermates Foxd1_wt Pdgfrb_wt.

肾纤维化以血小板源性生长因子受体β（platelet-derived growth factor receptor-β, PDGFR-β）阳性间充质细胞的扩增与活化为特征。为探究PDGFR-β活化的生物学后果，我们构建了原发性肾纤维化模型：该模型采用仅在肾脏间充质细胞中特异性活化PDGFR-β的转基因小鼠（transgenic mice），可诱导间充质细胞发生病理性增殖，并向肌成纤维细胞（myofibroblasts）表型转化。该模型小鼠表现为进行性系膜增生性肾小球肾炎、系膜硬化及间质纤维化，并因成纤维细胞促红细胞生成素合成缺失引发渐进性贫血。本研究通过微阵列（microarrays）技术，比较野生型小鼠（Foxd1_wt Pdgfrb_wt）与肾脏间充质细胞组成性活化PDGFR-β的小鼠（Foxd1_mt Pdgfrb V536A）的肾脏组织转录组，以筛选PDGFR-β信号通路的靶基因。整体实验设计：为构建肾脏间充质细胞特异性组成性活化PDGFR-β的小鼠（Foxd1_mt Pdgfrb V536A），我们使用如下基因工程小鼠：其一条野生型Pdgfrb等位基因被替换为携带激活点突变（V536A，位于PDGFR-β近膜结构域）的Pdgfrb条件性敲入（conditional knock-in）等位基因，该等位基因上游带有loxP侧翼终止密码子盒（floxed STOP cassette）。仅当Cre重组酶（Cre-recombinase）介导该终止盒切除后，突变受体才会得以表达。Cre重组酶的表达受FoxD1启动子调控，该启动子在发育阶段的肾脏间充质前体细胞中具有活性。本研究将Foxd1_mt Pdgfrb V536A小鼠与其野生型同窝仔鼠Foxd1_wt Pdgfrb_wt进行对照比较。