From Glomerular Endothelium to Podocyte Pathobiology in Preeclampsia : a Paradigm Shift

Preeclampsia is a pregnancy-specific syndrome characterized by renal dysfunction and high blood pressure. When evaluated with light microscopy, the renal lesion of preeclampsia is marked by endothelial cell swelling and the appearance of bloodless glomeruli. However, regarding the pathobiology of renal damage in preeclampsia, attention recently has shifted from the glomerular endothelial cells to the podocytes. The angiogenic imbalance in preeclampsia plays a key role in the development of both podocyte and endothelial damage in the glomerular filtration barrier. Here, we review the latest studies on the role of podocytes in the development of renal damage in preeclampsia and on podocytes as potential targets for diagnosis, treatment, and prevention of long-term complications of preeclampsia

Classical complement pathway activation in the kidneys of women with preeclampsia

A growing body of evidence suggests that complement dysregulation plays a role in the pathogenesis of preeclampsia. The kidney is one of the major organs affected in preeclampsia. Because the kidney is highly susceptible to complement activation, we hypothesized that preeclampsia is associated with renal complement activation. We performed a nationwide search for renal autopsy material in the Netherlands using a computerized database (PALGA). Renal tissue was obtained from 11 women with preeclampsia, 25 pregnant controls, and 14 nonpregnant controls with hypertension. The samples were immunostained for C4d, C1q, mannose-binding lectin, properdin, C3d, C5b-9, IgA, IgG, and IgM. Preeclampsia was significantly associated with renal C4d - a stable marker of complement activation - and the classical pathway marker C1q. In addition, the prevalence of IgM was significantly higher in the kidneys of the preeclamptic women. No other complement markers studied differed between the groups. Our findings in human samples were validated using a soluble fms-like tyrosine kinase 1 mouse model of preeclampsia. The kidneys in the soluble fms-like tyrosine kinase 1-injected mice had significantly more C4 deposits than the control mice. The association between preeclampsia and renal C4d, C1q, and IgM levels suggests that the classical complement pathway is involved in the renal injury in preeclampsia. Moreover, our finding that soluble fms-like tyrosine kinase 1-injected mice develop excess C4 deposits indicates that angiogenic dysregulation may play a role in complement activation within the kidney. We suggest that inhibiting complement activation may be beneficial for preventing the renal manifestations of preeclampsia

Association of Preeclampsia with Podocyte Turnover

BACKGROUND AND OBJECTIVES: Preeclampsia is characterized by hypertension and proteinuria, and increased shedding of podocytes into the urine is a common finding. This finding raises the question of whether preeclamptic nephropathy involves podocyte damage. This study examined podocyte-related changes in a unique sample of renal tissues obtained from women who died of preeclampsia. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS: All patients with preeclampsia who died in The Netherlands since 1990 and had available autopsy tissue were identified using a nationwide database of the Dutch Pathology Registry (PALGA). This resulted in a cohort of 11 women who died from preeclampsia. Three control groups were also identified during the same time period, and consisted of normotensive women who died during pregnancy (n=25), and nonpregnant controls either with (n=14) or without (n=13) chronic hypertension. Glomerular lesions, including podocyte numbers, podocyte proliferation, and parietal cell activation, were measured. RESULTS: Patients with preeclampsia had prominent characteristic glomerular lesions. The results showed that the number of podocytes per glomerulus did not differ significantly between the patients with preeclampsia and the control groups. However, preeclampsia was associated with a significant increase in intraglomerular cell proliferation (7.3% [SD 9.4] of the glomeruli of patients with preeclampsia had Ki-67–positive cells versus 1.6% [SD 3.3] of the glomeruli of hypertensive controls and 1.1% [SD 1.3] of nonpregnant controls; P=0.004) and activated parietal epithelial cells on a podocyte location (34% [SD 13.1] of the glomeruli of patients with preeclampsia versus 18.0% [SD 15.3] of pregnant controls, 11.9% [SD 13.2] of hypertensive controls, and 10.8% [SD 13.4] of nonpregnant controls; P=0.01). CONCLUSIONS: These findings suggest that the recently described mechanisms of podocyte replacement play a role in preeclampsia. These results provide key new insights into the pathogenesis of preeclamptic nephropathy, and they open new possibilities for developing therapeutic modalities