Ultrastructural localization of alpha-L-fucose, factor VIII related antigen and vimentin in endothelial cells of human skin blood vessels using the low temperature embedding technique with Lowicryl K4M

Morphological Changes in Lipodermatosclerosis and Venous Ulcers: Light Microscopy, Immunohistochemistry and Electron Microscopy

Objectives:

To demonstrate morphological changes in lipodermatosclerosis (LDS) and venous ulcers by histology, immunohistochemistry, electron microscopy and immunoelectron microscopy.

Design:

Single patient group study in patients with trophic skin changes in chronic venous insufficiency.

Setting:

Department of Dermatology, Medical University of Lübeck.

Patients:

Ten patients with venous leg ulcers.

Interventions:

Biopsies were taken from areas of LDS and compared with clinically normal-appearing skin of the affected leg and with ulcer tissue.

Main outcome measures:

Comparison of the morphological features on light and electron microscopy.

Results:

Superficial dermis. Histologically, the ulcer tissue and LDS skin show dilated tortuous vessels in a glomerulus-like arrangement in the superficial parts of the dermis. Ultrastructurally, the superficial vessels are surrounded by a cuff, which contains amorphous and basal membrane material and is most pronounced in LDS. Immunofluorescence studies reveal ill-defined perivascular staining after incubation with antibodies against fibrin(ogen), laminin and type IV collagen. The exact ultrastructural localization of type IV collagen within the perivascular cuff is observed by immunoelectron microscopy. Deep dermis. In deeper parts of the dermis, the vessels of both ulcer tissue and LDS are surrounded by cellular cuffs with pericytes, fibroblasts and compact collagen bundles.

Conclusions:

We suggest that the severe morphological changes in LDS and ulcer tissue play an important role in the pathogenesis of venous ulceration.

Spindle Cell Hemangioma and Epithelioid Hemangioendothelioma Arising in an Area of Lymphedema

We report the case of a 73-year-old female patient with a multifocal vascular tumor that we regard as composite hemangioendothelioma (CHE). The lesions developed in an area of lymphedema. CHEs are rare vascular tumors in which various types of hemangioendothelioma are combined in 1 lesion. In the present case, separate tumors with histologic features of spindle cell hemangioma and features resembling epithelioid hemangioendothelioma were clustered in 1 anatomic region.

Update on immunoelectron microscopy in diagnostic dermatopathology and cutaneous biology

Immunoelectron microscopy for diagnostic dermatopathology is hardly ever necessary. Immunoelectron microscopy, however, is very helpful in the work-up of interesting cases, for the study of genetic and autoimmune bullous diseases and for basic science studies, particularly in conjunction with molecular biology techniques. It is also very helpful for investigators requiring double labeling.

Phenotype of normal cutaneous microvasculature. Immunoelectron microscopic observations with emphasis on the differences between blood vessels and lymphatics

The lymphatic system has been poorly characterized in comparison to the blood vessels. We investigated the expression of microvasculature markers in cutaneous lymphatics and blood microvessels in normal skin. Scrotal skin was chosen because of its high density of both types of microvessels. A pre-embedding peroxidase-conjugated immunoelectron microscopy technique was used, allowing both the visualization of the lymph and blood vessels and their immunohistochemical staining. The markers studied included endothelial antigens (recognized by PAL-E, EN-4, and von Willebrand factor/factor VIII-related antigen), structural molecules of the vascular wall (alpha-smooth muscle actin, heparan sulfate proteoglycan, collagen type IV), and adhesion molecules (endothelial leukocyte adhesion molecule-1 [E-selectin], intercellular adhesion molecule-1 [ICAM-1], platelet endothelial adhesion molecule-1 [PECAM-1], vascular cell adhesion molecule-1 [VCAM-1]). It is shown that lymphatics of normal skin are phenotypically different from blood microvasculature, only weakly expressing endothelial markers (EN-4+, von Willebrand factor/factor VIII-related antigen +/-, PAL-E-), mural markers (alpha-smooth muscle actin-, heparan sulfate proteoglycan-, collagen type IV+) and do not express the studied adhesion molecules except PE-CAM-1 (E-selectin-, ICAM-1-, PECAM-1+, VCAM-1-). The results were substantiated by a double-labeling immunoelectron microscopic technique, which facilitates detection and assessment of microvascular segments. By this technique, collagen type IV, recognized by a peroxidase-labeled 2nd antibody, stains the basal lamina by a linear pattern, whereas a second optional epitope is visualized as grains by a silver-enhanced ultra-small gold-conjugated antibody. Our study shows that not only morphology but also antigenic phenotype of lymphatics differs significantly from blood vessels.

New applications of electron microscopy techniques in dermatopathology

The application of immunostaining techniques to electron microscopy specimens has led to a renewal of interest in electron microscopy in biological research in general, as well as in dermatopathology. Refinements in the preparative procedures have made easier the immunolocalization of antigens both in chemically-fixed and frozen unfixed tissues, embedded in plastic and sectioned. Application of these methods has led to the demonstration of the bullous pemphigoid antigen inside basal keratinocytes. HMB-45 antigen has been found to be present in premelanosomes. Recently, Factor XIIIa has been localized not only in dermal dendrocytes but also in endothelial cells and mast cells.

Techniques in immuno-electron microscopy. I. Cryosubstitution

Normal skin was cryoprotected by submerging it in a mixture of 30% dimethylformamide (DMF) in PBS or RPMI. Subsequently it was frozen in liquid propane gas. Cryosubstitution was carried out at -90 degrees C by using methanol to which uranyl acetate or osmium tetroxide were added. The tissue was embedded in either Lowicryl K4M at -40 degrees C or in Epon at +60 degrees C. The tissue was evaluated by its overall preservation of ultrastructural details and by its labeling intensity after incubation with either anti-desmoglein or anti-type VII collagen monoclonal antibodies. The mixture of DMF and PBS caused an electron-dense precipitate within the cell. The overall morphology was better in Epon-embedded material than in K4M-embedded material. However, the labeling was best in K4M material. Regardless of whether the tissue was embedded in Epon or K4M, the addition of osmium tetroxide markedly reduced the degree of labeling.

Crystalloid inclusion bodies of the endothelial cells in human fetal skin blood vessels and human umbilical cord vessels: a possible relationship to Weibel-Palade bodies?

Crystalloid inclusion bodies (CIB) of the endothelial cells (EC) were investigated in blood vessels of human fetal skin and the umbilical cord by electron- and immunoelectron microscopy. They were found in up to 15% of the investigated EC in various types of vessels. Their sizes ranged from 0.2 microns to 0.6 microns in the largest diameter. Most frequently we observed a laminated pattern of the crystalloid structure with a regular periodicity of dark and light bands. Additionally a honeycomblike pattern was also seen. Measurement of the CIB laminated structure revealed similar dimensions to Weibel-Palade bodies (WPB). In EC of all vessel types we found numerous WPB differing in electron density, shape and size from those of WPB found in adult blood vessels. WPB were found much less frequently in EC with CIB, suggesting that CIB is a precursor of WPB. After incubation with monoclonal antibody against von Willebrand factor (vWf) both WPB and large organelles were labeled. Because of their shape and size the labeled large organelles seemed to represent inadequately preserved CIB. After incubation with anti-lysozyme only the large organelles were labeled. A possible relationship of CIB to WPB is thus suggested. The presence of lysosomal enzymes such as lysozyme suggest that CIB are lysosomal organelle and participate in the uptake of vWf. The crystalloid pattern of CIB may represent an accumulation of a highly condensed form of vWf.