Immunohistochemical study of CD44 immunopositive cells in the muscular layers of the gastrointestinal tract in adult guinea pigs and mice

Identification of CD44 as a Cell-Surface Marker for Kit Negative Interstitial Cells of Cajal in Adult Mouse Colon

Loss of Kit protein expression is proven to influence the plasticity of interstitial cells of Cajal (ICCs) and may contribute to gastrointestinal (GI) dysfunctions. The role and fate of Kit negative ICCs are unclear, and cell-specific markers for the Kit ICCs are unknown. In this study, we treated adult mice with imatinib (a Kit signaling blocker) for 8 or 16 days and investigated whether CD44 is a specific marker for the Kit negative ICCs in the adult mouse colon. We aimed at examining the protein and mRNA level of CD44 and Kit by using Western blot and real-time RT-PCR, respectively. Our results indicated that Kit expression was downregulated for both protein and mRNA levels after imatinib treatment for 8 or 16 days as compared to the vehicle-treated mice. Interestingly, CD44 expression remained unchanged throughout the treatment. Immunostaining on whole-mount preparations for Kit and CD44 showed that CD44 was exclusively co-localized with Kit in the ICCs of the vehicle-treated mouse colon. After imatinib treatment, a number of CD44+/Kit- cells with elaborated processes were observed with an evident decrease of Kit+ cell number within the muscular layers (ICC-IM) and around the myenteric nerve plexus (ICC-MY) as compared to vehicle-treated mice. After discontinuing imatinib for 16 days, Kit+ ICC-MY and ICC-IM were completely co-localized with normalization of CD44 and Kit+ cell numbers. Overall, our results identify CD44 as a cell-specific surface marker for Kit-ICCs and may be useful to understand the role and fate of Kit- ICCs in GI disorders.

Vascular Interstitial Cells in Retinal Arteriolar Annuli Are Altered During Hypertension

Purpose

It has been suggested that arteriolar annuli localized in retinal arterioles regulate retinal blood flow acting as sphincters. Here, the morphology and protein expression profile of arteriolar annuli have been analyzed under physiologic conditions in the retina of wild-type, β-actin-Egfp, and Nestin-gfp transgenic mice. Additionally, to study the effect of hypertension, the KAP transgenic mouse has been used.

Methods

Cellular architecture has been studied using digested whole mount retinas and transmission electron microscopy. The profile of protein expression has been analyzed on paraffin sections and whole mount retinas by immunofluorescence and histochemistry.

Results

The ultrastructural analysis of arteriolar annuli showed a different cell population found between endothelial and muscle cells that matched most of the morphologic criteria established to define interstitial Cajal cells. The profile of protein expression of these vascular interstitial cells (VICs) was similar to that of interstitial Cajal cells and different from the endothelial and smooth muscle cells, because they expressed β-actin, nestin, and CD44, but they did not express CD31 and α-SMA or scarcely express F-actin. Furthermore, VICs share with pericytes the expression of NG2 and platelet-derived growth factor receptor beta (PDGFR-β). The high expression of Ano1 and high activity of nicotinamide adenine dinucleotide phosphate (NADPH)-diaphorase observed in VICs was diminished during hypertensive retinopathy suggesting that these cells might play a role on the motility of arteriolar annuli and that this function is altered during hypertension.

Conclusions

A novel type of VICs has been described in the arteriolar annuli of mouse retina. Remarkably, these cells undergo important molecular modifications during hypertensive retinopathy and might thus be a therapeutic target against this disease.

Interstitial Cells of Cajal: Pathology, injury and repair

Interstitial cells of cajal (ICC) are specialised cells located within the musculature of the gastrointestinal tract (GIT). Although they form only 5% of the cells in the musculature of the GIT, they play a critical role in regulating smooth muscle function and GIT motility in coordination with the enteric nervous system. C-kit is a transmembrane glycoprotein that plays a critical role in ICC development and maturation. Physiological conditions such as ageing, as well as pathological conditions that have different disease processes, negatively affect ICC networks and function. Absent or disordered ICC networks can be associated with disorders in GIT motility. This review highlights the mechanism of ICC recovery from various types of injury which entails understanding the development of ICC and the factors affecting it. ICC transformation into malignant tumours (gastrointestinal stromal tumours) and their potential as contributors to therapeutic resistance is also discussed.

Postnatal development of interstitial cells of Cajal in mouse colon in response to Kit signal blockade with Imatinib (Glivec)

This study investigated the response of interstitial cells of Cajal (ICC) in postnatal mouse colon to treatment with Imatinib (Glivec), a potent inhibitor of Kit receptor). ICC were revealed by immunofluorescent staining on frozen cross-sections and whole-mount preparations by anti-Kit and DOG1 antibodies. Kit and p-Kit protein were also evaluated by Western blot. After administration of Imatinib for 4 days beginning at 8 days post-partum (P8), the mean density of Kit+ ICC, which were localized around the myenteric nerve plexus (ICC-MY), within smooth muscle layers (ICC-IM) and in the connective tissue beneath the serosa (ICC-SS), was dramatically decreased to about 50% when compared with controls, but those Kit+ cells located at the submucosal border of circular smooth muscle layer (ICC-SM) seemed to be unchanged in both cell number and morphology. A small number of DOG1+/Kit(-) cells appeared during Imatinib administration. However, these Kit+ ICC were not changed in mice even after 12 days of Imatinib treatment from P24. When Imatinib was discontinued, the number of ICC recovered to normal within 4 days. Our results indicate that the postnatal development of ICC in the mouse colon is Kit dependent, but ICC-SM are unlikely, and the Kit dependence of ICC development is also age-dependent.