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Quantitative analysis of small intestinal microcirculation in the mouse
S Massberg1, S Eisenmenger, G Enders
1Ludwig-Maximilians University, Institute for Surgical Research, Klinikum Grosshadern, Munich, Germany. massberg@icf.med.uni-muenchen.de
Abstract:
Impairment of intestinal nutritive perfusion and accumulation of inflammatory cells in the intestinal microvasculature are well-known sequelae of mesenteric ischemia/reperfusion, sepsis, and shock. However, the molecular mechanisms underlying these alterations are still not fully understood. The mouse is particularly suitable for the study of these mechanisms since in this species the involvement of, for example, adhesion receptors or pro-/anti-adhesive mediators can be selectively investigated by the use of monoclonal antibodies or gene-targeted strains. The aim of our present study was, therefore, to establish a model to investigate the microcirculation in the mouse small intestine. Under anesthesia by inhalation of isoflurane-N2O, Balb/c mice (n = 16) were laparotomized, and a segment of the jejunum was exteriorized for intrvital fluorescence microscopy. Using FITC-dextran (MW 150,000) as a plasma marker, functional capillary density (FCD) of both the intestinal mucosa and muscle layer was analyzed. Nutritive perfusion was homogeneous in both compartments with values for FCD of 512 +/- 15 cm-1 in mucosa and 226 +/- 21 cm-1 in the muscle layer. No significant changes were observed throughout the observation period of 2 h (FCD values at the end of the observation period: 524 +/- 31 cm-1 and 207 +/- 7 cm-1 in mucosa and muscle, respectively). Besides capillary perfusion, leukocyte-endothelial cell interaction was analyzed in postcapillary venules of the intestinal submucosa using rhodamine-6G as an in vivo leukocyte stain. Under physiological conditions only a few white blood cells were found rolling along or firmly adherent to the microvascular endothelium (number of rolling leukocytes 1 +/- 0.2 cells/mm per second; number of adherent leukocytes: 18 +/- 7 cells/mm2). In a separate group rhodamine-6G-labeled syngeneic platelets were infused to analyze platelet-endothelial cell interactions quantitatively in vivo. Platelets rolled along or attached to the endothelium in a manner similar to leukocytes. However, in contrast to leukocytes the interactions were not restricted to venules, but were also observed in small arterioles. The newly established model allows for the visualization and quantitative assessment of both nutritive perfusion and platelet/leukocytendothelial cell interactions within the distinct layers of the mouse small intestine. Using this model in combination with gene-targeted mice or monoclonal antibodies it is possible to investigate the molecular mechanisms of intestinal inflammation reactions.
Insights
Researchers developed a new mouse model to study intestinal microcirculation, assessing capillary perfusion and cell interactions in the small intestine. This model aids in understanding inflammation mechanisms.
Area of Science:
- Physiology
- Microcirculation Research
- Inflammation Studies
Background:
- Intestinal microvascular dysfunction and inflammation are key in conditions like sepsis and shock.
- The precise molecular mechanisms driving these changes remain incompletely understood.
- Mice offer a versatile platform for investigating these mechanisms using genetic and antibody-based approaches.
Purpose of the Study:
- To establish a novel experimental model for investigating microcirculation in the mouse small intestine.
- To quantitatively assess nutritive perfusion and leukocyte-endothelial cell interactions in vivo.
- To provide a foundation for future studies on the molecular basis of intestinal inflammation.
Main Methods:
- Development of an in vivo fluorescence microscopy model in anesthetized Balb/c mice.
- Analysis of functional capillary density (FCD) in the jejunal mucosa and muscle layers using FITC-dextran.
- Quantification of leukocyte and platelet-endothelial cell interactions in postcapillary venules and arterioles using rhodamine-6G.
Main Results:
- Established baseline values for nutritive perfusion in the intestinal mucosa (512 cm-1) and muscle layer (226 cm-1).
- Demonstrated stable perfusion over a 2-hour observation period.
- Quantified physiological levels of rolling and adherent leukocytes and platelets in the microvasculature.
Conclusions:
- The newly developed mouse model enables simultaneous visualization and quantification of intestinal microcirculation parameters.
- This model is suitable for investigating the roles of specific molecules in intestinal inflammation using genetic or antibody-based manipulations.
- It provides a valuable tool for advancing the understanding of inflammatory processes in the gut.