Introduction
The aim of this symposium was to give an overview on novel approaches to gather functional and structural information on microvessels and their constituting vascular cells.
Presentations
The first three presentations focussed on experimental settings ranging from isolated cardiac myocytes ( M. Egger, Berne, Swiss) to tumors (P. Vajkoczy, Berlin, Germany) and the brain (S. Charpak, Paris, France). Then, the final presentation by G. Ambrosio (Perugia. Italy) translated the general theme into the clinical arena by discussing non invasive imaging modalities.
In his presentation on ‘Two-photon imaging of capillary blood flow in vivo’ S. Charpak (Paris, France) demonstrated the impressive options of these technique to obtain functional information on blood vessel behaviour in their native environment. Using intravital microscopy of the olfactory bulb, he investigated the vascular responses to changes in neuronal activity.
In a layer several hundred microns below the tissue surface, he could show that capillary flow is indeed tightly coupled to the local neuronal activity an1d calcium levels. This technique opens new possibilities to investigate complex interactions of critical functional elements on a tissue level.
M. Egger (Berne, Swiss) ’Local signalling in cardiac cells revealed by two-photon excitation’, presented a study on isolated myocytes. The two-photon approach is characterized by a minimal volume (about 1 cubic micron) of fluorescence excitation. This offers the possibility to release active compounds in very well defined local regions of the cell. To this end, the compound is applied in a ‘caged’ and inactive form, i.e. enclosed in a complex molecular envelope, the ‘cage’. A strong light pulse can then destroy the cage and deliver the drug at the desired time and location.
In his studies, M. Egger investigated the effects of substances interfering with calcium release and intracellular signalling. The presentation ‘Direct visualization of angiogenic sprouting’, P Vajkoczy (Berlin, Germany) focussed on the possibilities of intravital microscopy to combine information on structural features of the microcirculation and their dynamic changes in time with quantitative functional and molecular measurement (‘in vivo immuno-histochemistry’).
It is a specific advantage of the use of chronic intravital models (e.g. the skinfold chamber and the cranial window) to repeatedly investigate parameters and their development. Furthermore, the skinfold chamber allow the implantation and investigation of a number of interesting tissues.
In the final talk ‘New modes of non-invasive imaging of microcirculatory function in patients’, G Ambrosio (Perugia, Italy) compared the different opportunities to translate the investigation of microcirculatory parameters into the clinical practise. He demonstrated that microcirculatory phenomena are indeed clinically relevant and can be assessed by approaches like MRI, PET, SPECT and ECHO.