The technology to form simple cell type-specific spheroids can be further refined by generating vascular organoids from suspended EC and VSMC. During aggregation, they spontaneously organize within 24 to 48 hours to from 3D vascular organoids composed of a surface EC monolayer that covers a core of VSMC, thus representing an “inverted vessel wall”. 

Analyzing EC-VSMC communication in vascular organoids

Vascular organoids allow the investigation of EC-VSMC communication and can be generated by most types of human EC and VSMC, which both develop a higher level of differentiation and quiescence as compared to 2D as well as simple 3D cell culture conditions. 

_{Formation of vascular organoids generated from HUVECs and umbilical artery smooth muscle cells (HUASMC) (A). Self-organization of suspended GFP-expressing ECs (top images, arrows: HUVEC) and VSMC (top images, arrowheads: HUASMC) were recorded by time lapse imaging. The endothelial cell marker CD31 was detected in organoids that formed after 48 hours by immunofluorescence in combination with confocal imaging showing the cobblestone morphology of the EC monolayer on the surface (A, middle left image) and the core of CD31-negative VSMCs in the organoid center (A, middle right image). EC surface layer (bottom, left image). CD31 staining of cross sections of vascular organoids (B) generated from combinations of aortic smooth muscle cells (HAoSMC), HUASMC and umbilical artery endothelial cells (HUAEC), umbilical vein endothelial cells (HUVEC), aortic endothelial cells (HAoEC), sphenous vein endothelial cells (HSoVEC), dermal miccrovascular endothelial cells (HDMEC).} 

We use this technology to study cholesterol-induced formation of VSMC foam cells - a process that drives the formation arteriosclerotic plaques in human arteries. To this end, vascular organoids are generated from HUVEC and HUASMC as well as HAoEC and HAoSMC and exposed to either cholesterol or oxLDL (see figure). This simple organoid-based model allows us to identify conditions, which promote or protect from foam cell formation in a vessel wall sorrogate - studies, which are often performed by using genetically altered mice. 

_{Formation of VSMC foam cells in VSMC spheroids and HUVEC/HUASMC vascular organoids. VSMC spheroids and vascular organoids were exposed to oxLDL or cholesterol. Both EC and VSMC accumulate lipids/cholesterol in their cytosol as evidenced by a lipid-specific fluorescence staining. Quantification of the VSMC-associated fluorescence indicated that the presence of endothelial cells limits the accumulation of lipids in VSMC.}

 

Contact:

Prof. Thomas Korff, Abteilung Herz- und Kreislaufphysiologie 

E-Mail: korff(at)physiologie.uni-heidelberg.de