A New Method for Morphometric Analysis of Tissue Distribution of Mobile Cells in Relation to Immobile Tissue Structures

The distribution of cells in stained tissue sections provides information that may be analyzed by means of morphometric computation. We developed an algorithm for automated analysis for the purpose of answering questions pertaining to the relative densities of wandering cells in the vicinity of comparatively immobile tissue structures such as vessels or tumors. As an example, we present the analysis of distribution of CD56-positive cells and of CXCR3-positive cells (relative densities of peri-vascular versus non-vascular cell populations) in relation to the endothelium of capillaries and venules of human parietal decidua tissue of first trimester pregnancy. In addition, the distibution of CD56-positive cells (mostly uterine NK cells) in relation to spiral arteries is analyzed. The image analysis is based on microphotographs of two-color immunohistological stainings. Discrete distances (10–50 µm) from the fixed structures were chosen for the purpose of definining the extent of neighborhood areas. For the sake of better comparison of cell distributions at different overall cell densities a model of random distribution of “cells” in relation to neighborhood areas and rest decidua of a specific sample was built. In the chosen instances, we found increased perivascular density of CD56-positive cells and of CXCR3-positive cells. In contrast, no accumulation of CD56-positive cells was found in the neighborhood of spiral arteries

Keratins in the human trophoblast

Besides microfilaments and microtubules, intermediate filaments are major components of the cytoskeleton. In epithelial cells intermediate filaments are formed by heterodimers of specific keratins, whose expression pattern highly depends on the type of epithelium and differentiation degree of the cell. During the process of blastocyst implantation and subsequent development of the human placenta a very specialized epithelium appears at the feto-maternal interface. Arising from the trophectoderm of the blastocyst, the epithelium-like layer surrounding the early embryoblast, different trophoblast subtypes differentiate. They either develop into polar cells fulfilling real epithelial functions, or apolar tumor-like cells invading the maternal uterine wall to adapt the maternal tissue to progressing pregnancy. Thus, the whole trophoblast population, with all its subtypes, can be considered as an epithelial compartment and hence expresses keratin filaments. However, differentiation of trophoblast into different phenotypes may be linked to remodeling of the cytoskeletal composition, depending on spatiotemporal requirements of the respective cells. Here, we focus on the keratin composition of different trophoblast subtypes, how these keratins are used in trophoblast research and what is k

Metalloprotease Dependent Release of Placenta Derived Fractalkine

The chemokine fractalkine is considered as unique since it exists both as membrane-bound adhesion molecule and as shed soluble chemoattractant. Here the hypothesis was tested whether placental fractalkine can be shed and released into the maternal circulation. Immunohistochemical staining of human first trimester and term placenta sections localized fractalkine at the apical microvillous plasma membrane of the syncytiotrophoblast. Gene expression analysis revealed abundant upregulation in placental fractalkine at term, compared to first trimester. Fractalkine expression and release were detected in the trophoblast cell line BeWo, in primary term trophoblasts and placental explants. Incubation of BeWo cells and placental explants with metalloprotease inhibitor Batimastat inhibited the release of soluble fractalkine and at the same time increased the membrane-bound form. These results demonstrate that human placenta is a source for fractalkine, which is expressed in the syncytiotrophoblast and can be released into the maternal circulation by constitutive metalloprotease dependent shedding. Increased expression and release of placental fractalkine may contribute to low grade systemic inflammatory responses in third trimester of normal pregnancy. Aberrant placental metalloprotease activity may not only affect the release of placenta derived fractalkine but may at the same time affect the abundance of the membrane-bound form of the chemokine

Vascular endothelial expression of indoleamine 2,3-dioxygenase 1 forms a positive gradient towards the feto-maternal interface.

We describe the distribution of indoleamine 2,3-dioxygenase 1 (IDO1) in vascular endothelium of human first-trimester and term placenta. Expression of IDO1 protein on the fetal side of the interface extended from almost exclusively sub-trophoblastic capillaries in first-trimester placenta to a nearly general presence on villous vascular endothelia at term, including also most bigger vessels such as villous arteries and veins of stem villi and vessels of the chorionic plate. Umbilical cord vessels were generally negative for IDO1 protein. In the fetal part of the placenta positivity for IDO1 was restricted to vascular endothelium, which did not co-express HLA-DR. This finding paralleled detectability of IDO1 mRNA in first trimester and term tissue and a high increase in the kynurenine to tryptophan ratio in chorionic villous tissue from first trimester to term placenta. Endothelial cells isolated from the chorionic plate of term placenta expressed IDO1 mRNA in contrast to endothelial cells originating from human umbilical vein, iliac vein or aorta. In first trimester decidua we found endothelium of arteries rather than veins expressing IDO1, which was complementory to expression of HLA-DR. An estimation of IDO activity on the basis of the ratio of kynurenine and tryptophan in blood taken from vessels of the chorionic plate of term placenta indicated far higher values than those found in the peripheral blood of adults. Thus, a gradient of vascular endothelial IDO1 expression is present at both sides of the feto-maternal interface

Results of analysis of samples.

<p>(a) Relative density of CXCR3⁺ cells in neighborhood of capillaries and venules. (b) Relative density of CD56⁺ cells in neighborhood of capillaries and venules. (c) Relative density of CD56⁺ cells in neighborhood of spiral arteries. The data are individually normalized in relation to density in residual decidua = 1. (y axis, log scale.)</p

Segmentation of the fixed structure.

<p>The color image (a) is segmented by relative RGB color planes (b, c). Some morphological operations (scrapping of small objects, closing) yield the blue stained area A_B (d).</p

Definition of the endothelial neighborhood by morphological dilation.

<p>The segmented image of the endothelium (a) is morphologically dilated (b). (Here a neighborhood width of 30 µm is chosen.) The dilated image A_B + N (c) subtracted with the blue stained endothelial area A_B (d) yields the endothelial neighborhood area A_N (e). The total specimen area A_T (f) subtracted by the dilated area A_B + N (g) yields the residual decidua area A_D (h). A_N: Neighborhood area, A_D: Area of residual decidua, A_B: Area of endothelium, A_T: Area of total specimen.</p