RESEARCH PROJECTS

Gene Networks in Diabetic Microangiopathy

The damage of blood capillaries is a significant contribution to morbidity and mortality in the course of

the disease diabetes mellitus. The morphological hallmark of affected capillaries is thickening of the

basement membrane, an amorphous substance underlying the endothelial cells. Decades of research,

including single gene analysis, have so far failed to elucidate the molecular basis of this diabetic

microangiopathy. We think that a focus on genetic subnetworks could be a potential improvement in

understanding the condition

We have screen for differentially regulated genes between blood microvascular endothelial cells (BEC) from

normal and diabetic patients using Affymetrix U133 chips and identified 559 genes characteristic for diabetic

capillaries.

From resulting functional gene clusters we now estimate hypothetical gene networks. Selected genes of these 

networks are transiently overexpressed/repressed in immortalized HUVECs. In around 50 experiments we

update the network structure in an iterative way. The specific question is: Is it possible to convert the normal

network into the diabetic state and vice versa by manipulative expression of specific genes? With this

strategy we hope to narrow down the gene space relevant for diabetic microangiopathy.

Gene candidates are then analyzed on a single gene basis both functionally and diagnostically.

Our research is accompanied by a cooperation with social scientists, who opimize the informed consent

procedure with tissue donors.

The Ex Vivo Transcriptome of Endothelial Cells

Understanding endothelial pathology requires detailed knowledge about endothelial physiology. As a

satellite to the diabetic network project we study the transcriptomes of endothelial cells in normal

individuals. We use the fact that the transmembrane mucoprotein podoplanin is expressed specifically

on lymphatic vascular endothelial cells (LECs), but not on blood vascular endothelial cells (BECs). By a

triple immunolabeling protocol (CD31, CD45 and podoplanin) we isolated BECs and LECs with high

purity (>98.5%) directly ex vivo without any cell culture expansion step, using FACSorting. We linearly

amplified RNA in order to discriminate BEC and LEC transcriptomes by DNA chip analysis.

We have also compared ex vivo and in vitro cultured BECs and LECs and found dramatic

artefacts introduced by cell culture. (see publication in Physiological Genomics)

Lymphovascular Heterogeneity

We have consistently noticed that there exist several subpopulations of LECs in and ex vivo. We have isolated

these subpoulations and performed a shot-gun DNA chip analysis in order to characterize their transcriptomes.

We currently work on the funtional relevance of the gene sets.

Partners:    Departments of Plastic and Reconstructive Surgery, Rheumatology, Ophthalmology, ENT and

                 Dermatology, Complex Systems Research Group

                 Alitalo Lab (University of Helsinki)

Sponsors:   FWF, WWTF, MUV, bm:bwk