Aim: 

The morphology of mouse mesenteric artery (MMA) and the characteristics of interstitial cells (ICs) discovered in the wall of this blood vessel were studied.

Methods: 

Experiments were performed on segments of MMA after removal of fat and connective tissue and on freshly isolated single cells. MMA segments, after staining with DAPI and/or anti-kit antibodies, and single cells, after loading with the fluorescent Ca²⁺-sensitive indicator fluo-4AM, were examined using a laser scanning confocal microscopy. Gene expression was detected by RT-PCR technique.

Results: 

RT-PCR analysis of MMA tissue showed apart from the housekeeping gene b-actin, expression of mRNA for c-kit, the marker of ICs of Cajal. Z-scans of MMA segments fixed and stained with DAPI revealed at least three different cell types in the vessel wall. Besides an internal monolayer of endothelial cells, and circular smooth muscle cells in the media, some cells staining with c-kit antibodies were found in adventitia. This was confirmed by staining of living pressurized MMA segments. Enzymatic dispersion of MMA revealed a population (5-7%) of ICs among numerous smooth muscle cells (SMCs). ICs had brighter fluorescence than SMCs, but no local or global calcium transients were seen, which are typical for SMCs at room temperature. Also ICs, in contrast to SMCs, did not contract in response to activation of receptors, depolarisation or mechanical disruption. However they responded with an increase in [Ca²⁺]_i.

Conclusion: 

Our results demonstrate the presense of novel ICs in the adventitia of MMA; their role is as yet unknown.

This work is supported by The Wellcome Trust (042293 and 074724)