- M.D., Free University of Berlin, Yale University School of Medicine
Program in Cellular & Molecular Physiology: Membrane Biology
The main focus of our research group is to understand the pathophysiology of proteinuria, the mechanism whereby the capillary wall in the renal glomerulus is altered and albumin and other molecules cross the multi-layered membrane. Proteinuria is the hallmark of acute and chronic kidney damage and its understanding is not only of pathophysiologic interest, but may also lead to novel therapeutic strategies for renal disease.
Since several cellular systems are involved in the integrity oft he capillary wall we focus both on endothelial cells (Hermann Haller) and podocytes (Mario Schiffer). The main questions with regard to the endothelium are (1) the differentiation of these cells into specialized “fenestrated” cells, (2) the expression and function of its glycocalyx layer, and (3) the secretion of cytokines, which are important for the communication between endothelium and podocytes.
We developed a novel model system for proteinuria screening in developing zebrafish larvae using transgenic fish and fluorescent plasma protein to measure proteinuria in screening assays to analyze the molecular mechanisms of capillary permeability and to identify novel therapeutic targets to prevent proteinuria.
Zebrafish are an ideal model to test gene deletion by using morpholino or antisense strategies. Recent work with the zebrafish model has extended from the study of developmental biology to a wide array of experimental studies relevant to human disease. The zebrafish is an effective model-species to examine the direct effects of gene targeting in a vertebrate, particularly in the context of kidney development.
Zebrafish development occurs rapidly from the fertilized egg to free-swimming larvae in 2.5 days and the embryos have transparent internal organ development that can be observed without dissection. The functional kidney in the zebrafish is the pronephros, a simplified organ structure with only two nephrons and the glomeruli fused at the midline, containing a full range of cell types typical of kidneys in higher vertebrates.
This zebrafish proteinuria model enables us to screen for novel genes in the pathogenesis of renal and vascular disease and identify targets for drug development. Genes of interest are knocked down in zebrafish embryos and effects are analyzed in proteinuria. To further analyze the molecular mechanisms of proteinuria we use transgenic GFP-zebrafish, cell culture, confocal microscopy and electron microscopy.
With this high throughput assay system we can examine the effects of genetic disruption on the barrier function in the pronephros. We are able to successfully screen for genes that are promising candidates in loss-of-function experiments in mice. We inject fluorescence labeled dextrans and monitor the fluorescence intensity over time in the retinal vessel area. In addition, we perform detailed analysis with electron microscopy using transgenic fish with a green fluorescent protein labeled pronephros. To further analyze novel therapeutic targets for renal disease, we are collaborating with Ron Korstanje and his lab group at the Jackson Laboratory. This collaboration allows us to use mice as a second animal model and translational tool for the development of novel therapies.
Additionally, we are especially interested in the protein kinase C (PKC) family. We have found that PKC isoforms play an important role in diabetic nephropathy, transplantation, and inflammation. We are now analyzing the role of PKC epsilon, theta, and zeta in our zebrafish model. In addition, we are studying the effects of environmental toxins on proteinuria in the zebrafish model.
Our model system together with our collaborators at the Jackson Laboratory and at Maine Medical Center and Maine Medical Center Research Institute in Portland is the basis for the reMAINE Healthy collaboration.
Program in Clinical Partnerships
This project has further spurred a larger statewide initiative called reMAINE Healthy, a new clinical research partnership between scientists at the MDI Biological Laboratory and The Jackson Laboratory, and physicians and patients at the Maine Medical Center (MMC) in Portland and Maine Medical Center Research Institute (MMCRI).
ReMAINE Healthy is a bench-to-bedside translational research program on genes and mechanisms for the early detection of chronic kidney disease and End Stage Renal Disease. This program will take laboratory discoveries in animal models and “translate” them into new clinical tools for diagnosing and preventing kidney disease in humans. The reMAINE Healthy program will use novel zebrafish models, genetic mouse models and samples from a patient cohort with chronic kidney disease for a translational research program in renal disease.
Chronic kidney disease affects 26 million adults, and over $42 billion is spent annually treating patients with this disease in the United States. It is a major diagnostic challenge, as people with early stages of the disease tend not to have any symptoms. The most common causes of chronic kidney disease are diabetes and hypertension. The aim of this collaboration is to identify novel molecules important in the pathophysiology of renal disease, which can serve as therapeutic targets or diagnostic tools to prevent chronic kidney disease.
A list of selected publications can be found here: https://mdibl.org/faculty/hermann-haller/