Regulation of substance P mRNA expression in human dermal microvascular endothelial cells

Vascular endothelial cells have been identified as a source of substance P (SP) which may act in an autocrine/paracrine fashion to bring about nitric oxide (NO)-dependent vasodilatation and mitogen-induced cell division or immunologic and inflammatory responses. Whilst SP is localised in and released from endothelial cells, an endothelial mRNA expression of SP has not previously been shown. In the present study, mRNA expression of SP in human dermal microvascular endothelial cells is demonstrated using in situ hybridisation techniques with enhancement procedures. Incubation of microvascular endothelial cells with nerve growth factor (NGF) under conditions of increased shear stress increases the mRNA expression and release of SP Endothelin (ET) release is also enhanced. These changes are pertinent to circulatory, events that may occur in Raynaud's phenomenon in systemic sclerosis.

Ultraviolet B-Induced Skin Angiogenesis Is Associated with a Switch in the Balance of Vascular Endothelial Growth Factor and Thrombospondin-1 Expression

We have previously shown that targeted overexpression of the endogenous angiogenesis inhibitor thrombospondin-1 (TSP-1) in the epidermis prevented chronic ultraviolet B (UVB)-induced angiogenesis and cutaneous photodamage in mice, suggesting that angiogenesis plays a critical role in the mediation of UVB effects on the skin. Nevertheless, the molecular regulation of angiogenesis factors and inhibitors by acute UVB irradiation still remains to be elucidated. We performed quantitative analyses of cutaneous vascularity and of vascular endothelial growth factor (VEGF) and TSP-1 expression after acute UVB irradiation of mouse skin. Skin vascularity in the upper dermis was greatly increased until day 8 after a single dose of UVB irradiation (200 mJ per cm2) and associated with upregulation of VEGF mRNA expression, with downregulation of TSP-1 mRNA, and with protein expression in the hyperplastic epidermis. After 13 days, skin vascularity was normalized with downregulation of VEGF mRNA expression and upregulation of TSP-1 mRNA expression to the levels observed in non-UVB-irradiated skin. In contrast, the angiogenic UVB response was prolonged in TSP-1-deficient mice. We found a pronounced induction of the TSP-1 receptor CD36 in CD31-positive vessels on day 8 after UVB irradiation, associated with vascular endothelial cell apoptosis. These results demonstrate that acute UVB irradiation leads to a shift toward a proangiogenic environment and they suggest that the balance between VEGF and TSP-1 plays a critical role in the control of angiogenesis and vascular regression induced by acute UVB irradiation.

A reappraisal of the histologic findings of pigmented pretibial patches of diabetes mellitus

BACKGROUND

Pigmented pretibial patches (PPPs) are the most common cutaneous alterations in diabetes mellitus, found in up to 50% of diabetic patients. They classically present as flat-topped, dull-red papules on the pretibial areas, later becoming hyperpigmented and atrophic. Little is known regarding the pathogenesis of these lesions, and the histopathologic findings have been regarded as non-specific.

METHODS

We investigated the clinical and pathologic attributes of a series of 12 diabetic patients with PPP in an effort to discern any specific histologic attributes compared to normal skin removed from diabetic patients with cutaneous carcinoma.

RESULTS

All cases of PPP showed hyaline microangiopathy, all patients showed extravasated erythrocytes and/or hemosiderin deposits, and 10 patients showed an appreciable number of perivascular plasma cells. The average number of plasma cells per vascular plexus was 2.2. Control specimens removed from five diabetic patients showed hyaline microangiopathy, and three showed extravasated erythrocytes and hemosiderin. One patient showed a single vascular plexus with two plasma cells, p = 0.01.

CONCLUSION

The presence of increased dermal perivascular plasma cells in the appropriate clinical context might be an important and under-recognized clue for PPP. The pathogenic significance of this finding is unknown.

Engraftment of a vascularized human skin equivalent

Clinical performance of currently available human skin equivalents is limited by failure to develop perfusion. To address this problem we have developed a method of endothelial cell transplantation that promotes vascularization of human skin equivalents in vivo. Enhancement of vascularization by Bcl-2 overexpression was demonstrated by seeding human acellular dermis grafts with human umbilical vein endothelial cells (HUVEC) transduced with the survival gene Bcl-2 or an EGFP control transgene, and subcutaneous implantation in immunodeficient mice (n=18). After 1 month the grafts with Bcl-2-transduced cells contained a significantly greater density of perfused HUVEC-lined microvessels (55.0/mm3) than controls (25.4/mm3,P=0.026). Vascularized skin equivalents were then constructed by sequentially seeding the apical and basal surfaces of acellular dermis with cultured human keratinocytes and Bcl-2-transduced HUVEC, respectively. Two weeks after orthotopic implantation onto mice, 75% of grafts (n=16) displayed both a differentiated human epidermis and perfusion through HUVEC-lined microvessels. These vessels, which showed evidence of progressive maturation, accelerated the rate of graft vascularization. Successful transplantation of such vascularized human skin equivalents should enhance clinical utility, especially in recipients with impaired angiogenesis.

A clinical model of dermal wound angiogenesis

Full-thickness dermal biopsies were performed in healthy volunteers to establish the range of angiogenic responses in wound healing in a normal population. Four-millimeter punch biopsies were made in the forearms of 15 healthy volunteers. Each wound was evaluated microscopically 4-5 times per week for 2 weeks. A semiquantitative wound scoring system to evaluate the neovasculature at the wound periphery was investigated. A vascular score was calculated for each wound at each observation. Two independent observers analyzed the microscopic wound images using the scoring system. At the end of the 14-day period, repeat biopsies were performed on some of the volunteers, and the granulation tissue was stained with anti-CD31. The Kaplan-Meier method was used to estimate the distribution of the time to reach predetermined target average vascular scores. A mixed-effects regression model indicated that time, age, and observer were predictors for the average vascular score outcome. The pattern and time course for wound neovascularization was highly reproducible in this group of healthy volunteers, and the assay was feasible and well tolerated. This wound angiogenesis model may be useful for monitoring the effects of antiangiogenic agents on normal wound neovascularization.

Vascular expression of matrix metalloproteinase-13 (collagenase-3) in basal cell carcinoma

Matrix metalloproteinase-13 (MMP-13; collagenase-3) was detected in the vasculature from 17 of 20 human basal cell carcinomas as assessed by immunohistology immediately after surgery. In contrast, MMP-1 (interstitial collagenase) was detected in the vasculature of only two of the same specimens. MMP-13 reactivity was also observed in the capillaries of normal human skin taken from the wound margin. Human dermal microvascular endothelial cells as well as human umbilical vein endothelial cells were isolated in culture and examined for MMP-13 expression. By reverse transcription-polymerase chain reaction and Southern blotting, an MMP-13 transcript was detected in unstimulated endothelial cells. The transcript was upregulated in cells treated with 50 nM phorbol myristate acetate (PMA). Western blotting demonstrated the presence of an anti-MMP-13 - immunoreactive protein in culture fluid from both cell sources. Immunoreactivity was stronger in culture fluid from cells treated with interleukin-1alpha (IL-1alpha) than in culture fluid from control cells. Tumor necrosis factor-alpha (TNF-alpha) and PMA also upregulated MMP-13 expression but these agents were not as effective as IL-1alpha. Additionally, reactivity was greater in culture fluid from endothelial cells grown on three-dimensional lattices of polymerized type I collagen than on dried collagen films. These data indicate that endothelial cells in the skin are a source of MMP-13 and that enzyme expression is upregulated under conditions that promote endothelial cell growth and vascular differentiation.

Cutis marmorata telangiectatica congenita with hemangiomatous histopathologic features

Cutis marmorata telangiectatica congenita (CMTC) is a congenital cutaneous vascular malformation that is diagnosed on the typical clinical findings of persistent cutis marmorata, telangiectasia, phlebectasia, occasional ulceration and atrophy, and tendency for clinical improvement. Histopathologic findings seldom have been reported. We report a case of CMTC with atypical histopathologic findings of proliferation of vasculature in addition to dilated capillaries in the dermis. We have reviewed all cases of CMTC with histopathologic findings published in the English-language literature. The most common and prominent finding was dilation of capillaries and veins in the dermis (13/15 cases). Two cases, including our own, demonstrated proliferation of vascular channels. The implications of vascular proliferation on the clinical course of CMTC are unclear.

Expression of claudin-5 in dermal vascular endothelia

Claudins and occludin are integral membrane proteins at tight junctions (TJs). We examined subcellular localization of claudin-5 and occludin in dermal vascular endothelia. Immunofluorescence staining showed that claudin-5 was expressed at the cell-cell border of dermal vascular endothelia in mouse skin. However, in some dermal vessels, claudin-5 expression was markedly decreased or absent in amount by double-immunofluorescence stainings with PECAM-1 and PAL-E. In contrast, occludin was not detected in dermal vessels. Freeze-fracture and immunoreplica electron microscopy on primary-cultured human dermal endothelial cells showed that claudin-5 was localized at tight junctions. These findings confirmed that TJs in dermal vascular endothelial cells are composed of claudin-5.

Measurement of protein metabolism in epidermis and dermis

We found that, in the rabbit ear, the dermal protein contains 75.5% of cutaneous phenylalanine and 97.9% of cutaneous proline; the remaining 24.5% of phenylalanine and 2.1% of proline are in the epidermal protein. This finding led us to develop two novel models that use phenylalanine and proline tracers and the rabbit ear to quantify protein kinetics in the epidermis and dermis. The four-pool model calculates the absolute rates of protein kinetics and amino acid transport, and the two-pool model calculates the apparent rates of protein kinetics that are reflected in the blood. The results showed that both epidermis and dermis maintained their protein mass in the postabsorptive state. The rate of epidermal protein synthesis was 93.4 +/- 37.6 mg x 100 g(-1) x h(-1), which was 10-fold greater than that of the dermal protein (9.3 +/- 5.8 mg x 100 g(-1) x h(-1)). These synthetic rates were in agreement with those measured simultaneously by the tracer incorporation method. Comparison of the four-pool and two-pool models indicated that intracellular cycling of amino acids accounted for 75 and 90% of protein kinetics in the dermis and epidermis, respectively. We conclude that, in the skin, efficient reutilization of amino acids from proteolysis for synthesis enables the maintenance of protein mass in the postabsorptive state.

Ultrastructural changes elicited by a non-ablative wrinkle reduction laser

BACKGROUND AND OBJECTIVES

Cosmeceuticals, chemical peels and collagen injections are used to rejuvenate skin, but none of these methods is effective or permanent. Recently, laser resurfacing has been found to be effective, but the incidence of side effects is relatively high. Two years ago, the non-ablative wrinkle reduction laser (N-Lite, ICN Photonics, UK) was developed, and there have been several reports about its clinical effectiveness. In this study, we have investigated ultrastructural changes elicited by exposure to the N-Lite laser.

STUDY DESIGN/MATERIALS AND METHODS

Eight adult volunteers were recruited for this study. They were treated with the N-Lite laser and 3-mm skin punch biopsies were obtained 3 hours, 1 day, 3 days, 1 week, 2 weeks, 4 weeks and 5 weeks after the laser exposure. These specimens were examined by electron microscopy.

RESULTS

Three hours after the laser therapy, the capillaries showed endothelial cell edema with hemostasis and marked edema was observed around them. Neutrophils, monocytes and mast cells were observed in the extravascular dermis. These acute dermal inflammatory changes were observed until 1 week after the laser treatment. Two weeks after the laser treatment, the capillaries showed an almost normal structure, and dermal edema was not observed around them. New elastic fibers and collagen fibers had increased around the capillaries. Four weeks after the laser treatment, interstitial fibrosis was observed around the capillaries.

CONCLUSIONS

N-Lite laser irradiation leads to interstitial fibrosis, especially around the capillaries, 4 weeks after the laser irradiation.

Notch signaling in primary endothelial cells

The Notch family of cell-surface receptors has been proposed to regulate cell-fate decisions by modulating the ability of each cell to respond to environmental cues. In vertebrates, gain-of-function and loss-of-function studies have demonstrated a requirement for Notch signaling for proper patterning of the vasculature during embryogenesis. To examine the molecular mechanisms by which Notch regulates vascular development, we analyzed changes in gene expression in response to Notch signaling. Notch signal transduction and function were assessed in primary human endothelial cells isolated from the dermal microvasculature of neonates, HMVECd. We demonstrate that HMVECd cells express a heterodimeric form of endogenous Notch4 on their cell surface. Using an in vitro coculture assay, we found that Delta4 can function as a ligand for Notch4 in HMVECd cells. Moreover, ectopic expression of an activated allele of Notch4 upregulated the expression of Delta4, suggesting that there may be a regulatory loop between Notch4 and its ligand, Delta4. Notch4 activation also induced the expression of the transcriptional repressors, HES1, HERP1, and HERP2, as well as ephrinB2, an angiogenic factor proposed to be involved in arterial/venous endothelial cell specification.

Mouse model for hereditary hemorrhagic telangiectasia has a generalized vascular abnormality

BACKGROUND

Mutations in endoglin or activin like kinase-1, both involved in the endothelial transforming growth factor-beta signaling pathway, cause the autosomal dominant bleeding disorder hereditary hemorrhagic telangiectasia. We and others have reported mouse models for this disease that share the characteristic phenotype of dilated vessels and sporadic hemorrhage. The reasons for the variable phenotype in hereditary hemorrhagic telangiectasia are not understood.

METHODS AND RESULTS

After a detailed immunohistochemical analysis of 129/Ola mice, which are heterozygous for a targeted deletion in the endoglin gene, we observed intrinsic abnormalities in the vascular walls throughout the cutaneous vasculature. Postcapillary venules were dilated, and up to 70% of the vascular wall had no smooth muscle cells. The supporting layers of collagens and elastin were irregular, with thin areas, adding to the fragility of these vessels. A variable hemorrhagic phenotype was observed in which local bleeding is associated not only with fragile vessels but also with regions of inflammation.

CONCLUSIONS

These findings have relevance to our understanding of the molecular basis of vascular integrity in a wide range of diseases.

The role of stratum corneum and dermal microvascular perfusion in penetration and tissue levels of water-soluble drugs investigated by microdialysis

BACKGROUND

Hydrophilic drugs are poorly absorbed when applied topically, due to low partitioning through the lipid matrix of the stratum corneum. Cutaneous blood flow rapidly clears the absorbed drug, which may result in low tissue levels. This is of importance for topically applied drugs whose site of action is within the epidermis or dermis. Dermal drug levels can be measured using cutaneous microdialysis, which is a means of continuously sampling substances from the dermal extracellular fluid.

OBJECTIVES

To measure the contribution of stratum corneum barrier and microvascular perfusion in determining dermal tissue levels of hydrophilic drugs (aciclovir and penciclovir) in vivo.

METHODS

Studies were performed using microdialysis of the volar surface of the forearm of healthy volunteers (n = 55) over a 5-h collection period. Stratum corneum was removed by tape stripping, and barrier disruption quantified by measurement of transepidermal water loss (TEWL); dermal microvascular perfusion was modulated by inclusion of noradrenaline in the microdialysis perfusate.

RESULTS

With intact skin and normal cutaneous blood flow the concentration of penciclovir recovered was below assay threshold (0.05 ng x mL(-1). With noradrenaline-induced local vasoconstriction, the area under the curve of drug absorbed through normal skin (+/- SEM) was 13.3 +/- 2.9 ng mL(-1) h(0-5) for penciclovir and 27.6 +/- 10.6 ng mL(-1) h(0-5) for aciclovir. Removal of the stratum corneum (to glistening) by tape stripping increased penciclovir absorption by 1300-fold and aciclovir absorption by 440-fold, confirming the stratum corneum as the major barrier to hydrophilic drug absorption. Sequential barrier disruption by tape stripping gave a close correlation between penciclovir concentration absorbed per hour and barrier disruption measured by TEWL (r2 = 0.9283). There was a 15.6-fold difference in the recovery of penciclovir through barrier-deficient skin with and without cutaneous blood flow. There was no relationship between fibre depth and amount of drug dialysed, which suggests free movement of antiviral drug on reaching the aqueous environment of the dermis.

CONCLUSIONS

This study defines for the first time the relationship between the degree of mechanical barrier impairment and drug absorption at the same anatomical site in humans, and the role of blood flow in drug clearance in vivo.

VEGFR-2-specific ligand VEGF-E induces non-edematous hyper-vascularization in mice

VEGF family members play important roles in angiogenesis and vascular permeability. VEGF-A-transgenic mice showed an increased vascularization with edema due to hyper-vascular permeability and subcutaneous hemorrhage as side effects. VEGF-A binds and activates two receptors, VEGFR-1 (Flt-1) and VEGFR-2 (KDR/Flk-1). To dissect the signals of these two receptors, we generated transgenic mice overexpressing either the VEGFR-2-specific ligand VEGF-E(NZ-7) or VEGFR-1-specific ligand PlGF-II under the control of the Keratin-14 promoter. VEGF-E-mice showed a significant increase in vascularization (about 10-fold compared to control mice) in subcutaneous tissues, whereas PlGF-mice showed only a 2-3-fold increase. Interestingly, VEGF-E-mice did not show any clear edematous lesions or hemorrhagic spots on the skin. Microscopically, VEGF-E-induced capillary networks have a well organized structure with the recruitment of pericytes. These results indicate that VEGF-E is a new angiogenic agent with less side effects for clinical usage.

[Local application of bFGF and sucralfate during continuous tissue expansion]

OBJECTIVE

To investigate the effect of local application of bFGF and sucralfate during continuous tissue expansion (CTE).

METHODS

CTE combined with local administration of bFGF and sucralfate was used in twelve patients with scar and nasal tip defects. Twenty three expanders were placed in the subcutaneous pockets through intralesion short incisions. Continuous expansion began at 1-3 days after expander implantation. The histomorphological changes and epidermal cell proliferation were observed. The clinical results were investigated.

RESULTS

The average inflation time was 8.9 days. The average interval of the two operations was 13.5 days. The average hospitalization was 28.4 days. The average immediate stretch-back rate of the expanded skin was 25.7%. The clinical results were satisfactory without any complications. Histological examinations showed that the epidermal, granular and spinous layer became thicker. The basal cells increased significantly. The dermis thinned slightly and the collagen fibers became thicker. The elastic fiber regenerated significantly. Fibroblast and capillary density increased obviously. The immunohistochemistry analysis showed that the proliferation of epidemic basal cells was significant postoperatively.

CONCLUSION

Local application of exogenous bFGF and sucralfate during CTE was feasible in patients. It could accelerate tissue expansion and improve the quality of expanded skin flap.

In vivo tolerance assessment of skin after insertion of subcutaneous and cutaneous microdialysis probes in the rat

The purpose of the study was to evaluate the trauma induced by insertion of the linear microdialysis probe in the subcutaneous and dermal tissue in the rat and to check if the microdialysis probe insertion affects transdermal drug delivery. Non-invasive bioengineering methods (TEWL, Laser Doppler Velocimeter, Chromameter) as well as histology were combined to characterize these effects. The results showed that the dermal and subcutaneous insertion of microdialysis probes did not change skin permeability, blood flow and color, confirming the safety of this technique. The probe depth did not influence the trauma. No significant physical damage after probe insertion was noticed. Thus, the present work validates the use of microdialysis in dermatopharmacokinetics studies after topical or systemic drug delivery.

[Diffuse dermal angiomatosis]

Diffuse dermal angiomatosis (DDA) is a benign, acquired vascular proliferation characterized by painful, poorly circumscribed, livid-erythematous plaques with frequent central ulceration. The clinical features are reminiscent of reactive angioendotheliomatosis or embolia cutis medicamentosa. Histologically, a dense diffuse network of regular capillary vessels throughout the dermis is seen. Endothelial atypia, atypical mitoses or signs of vasculitis are missing. A 43-year-old woman developed a bizarre brownish-livid rapidly growing lesion of DDA 8 centimeters above a surgical scar, shortly after removal of 20 kilograms of fatty tissue from the lower abdominal wall. DDA regressed spontaneously within 12 weeks, and has not recurred over 4 years of follow-up.

[The applied anatomy of axial subdermal vascular network skin flap and its application in the management of deep burn wound]

OBJECTIVE

To explore the anatomical basis and clinical application of axial subdermal vascular network skin flap (ASVNF) in the management of deep burn wounds.

METHODS

Twelve samples of skin and subcutaneous tissue of lower extremities from adult cadavers were anatomically observed. The course, branching and the architecture of the subdermal vascular network (SVN) in the superficial facia and the ultra-thin area of the anterolateral femoral and saphenous axial subdermal vascular network skin flaps were intensively studied. The wounds in twenty-six patients with deep burn injury in the limbs were repaired with ASVNF.

RESULTS

The circular thinning method was employed in the preparation of anterolateral femoral ASVNF whose blood supply was provided by the musculocutaneous perforators. And the "U" shaped ultra-thin method was employed in the preparation of saphenous ASVNF, whose blood supply was directly provided by skin vessels. The flaps in these 26 patients survived very well in terms of the flap color, texture, contour and function after followed-up for 0.5 approximately 2.5 year.

CONCLUSION

Thinning methods for different kinds of ASVNF should be individualized. ASVNF might be an optimal choice in the management of deep burn wounds due to its obvious advantages.

The level of IgA antibodies to human umbilical vein endothelial cells can be enhanced by TNF-alpha treatment in children with Henoch-Schönlein purpura

Anti-endothelial cell antibodies (AECA) have been found to play an important role in many vascular disorders. In order to determine the presence of AECA in children with Henoch-Schönlein purpura (HSP), and to elucidate the pathogenic and clinical value of their measurement in this disease, AECA were detected by immunofluorescence staining and a human umbilical vein endothelial cell (HUVEC)-based enzyme-linked immunosorbent assay (ELISA) in 20 children with HSP, 10 children with juvenile rheumatoid arthritis (JRA) without vasculitis and 10 normal healthy children. Antibodies against another endothelial cells, human dermal microvascular endothelial cells (HMVEC-d) were also detected by cell-based ELISA. In some experiments, we compared the binding activity of antibodies to HUVEC with and without tumour necrosis factor-alpha (TNF-alpha) or interleukin-1 (IL-1) pretreatment. Patients with acute onset of HSP had higher serum levels of IgA antibodies, both against HUVEC and against HMVEC-d, than healthy controls (P = 0.001, P = 0.008, respectively). Forty-five per cent of patients had positive IgA AECA to HUVEC, and 35% had positive IgA AECA to HMVEC-d. The titres of IgA antibodies to HUVEC paralleled the disease activity. After TNF-alpha treatment, the values of IgA AECA to HUVEC in HSP patients were significantly increased (P = 0.02). For IgG and IgM AECA, there was no difference between HSP patients and controls (P = 0.51, P = 0.91). Ten JRA children without vasculitis had no detectable IgG, IgM or IgA AECA activity. The results of this study showed that children with HSP had IgA AECA, which were enhanced by TNF-alpha treatment. Although the role of these antibodies is not clear, IgA AECA provide another immunological clue for the understanding of HSP.

Failure of Ibuprofen to prevent progressive dermal ischemia after burning in guinea pigs

OBJECTIVE

It is controversial whether the use of prostaglandin inhibitors could prevent progressive dermal ischemia in the postburn stasis zone. This study evaluated the effect of Ibuprofen on preventing postburn dermal ischemia using an animal model of India ink perfusion and skin transparent preparation techniques.

METHODS

The closely clipped backs of the guinea pigs were bathed in 75 degrees C water for 10s. Ibuprofen-treated groups were fed intragastrically with Ibuprofen (12.5mg/kg) every 6h. All animals were perfused with 70% India ink via a cervical artery cannula at 16 kPa constant pressure at 0, 8, 16, 24h postburn. Skin transparent preparations were made, and 6-keto-PGF(1 alpha) and T x B(2) levels in skin tissue were assessed.

RESULTS

India ink filling rates in skin capillary plexuses decreased gradually with postburn time elapsing (P<0.01). 6-keto-PGF(1 alpha) and T x B(2) levels in two groups increased. The increase of T x B(2) was dominant, which was related to postburn dermal ischemia (r=0.742, P<0.01). Though levels of 6-keto-PGF(1 alpha) and T x B(2) decreased in Ibuprofen-treated groups, India ink filling rates showed no significant difference between controls and experimental groups (P>0.05). The results were also confirmed by observation of skin transparent preparations.

CONCLUSION

This study suggests that Ibuprofen has no preventive effect on progressive dermal ischemia after burning.

Tightening of endothelial cell contacts: a physiologic response to cocultures with smooth-muscle-like 10T1/2 cells

Tightening of endothelial cell-to-cell contacts is an important event at the end of angiogenesis in order to achieve controlled transfer of solutes between the blood stream and solid tissues. We found that tightening of endothelial cell-to-cell contacts and the formation of a permeability barrier can be induced in vitro by dibutyryl cAMP and hydrocortisone. This process is accompanied by increased junctional localization and cytoskeletal association of the adherens junctional plakoglobin and the tight junction associated proteins ZO-1, ZO-2, and occludin. Based on these findings, we proceeded to investigate whether smooth-muscle-like mesenchymal cells would influence endothelial junctional differentiation. For this purpose, human umbilical chord vein endothelial cells and murine smooth-muscle-like 10T1/2 cells were cocultivated and compared with their respective monocultures. Immunofluorescence on cells and Western blot analyses were performed for marker proteins of adherens and tight junctions. Functional permeability assays were performed for the tracer molecule biotin-dextran. The results indicated that 10T1/2 cells induced the tightening of endothelial cell-to-cell contacts. Plakoglobin, ZO-1, ZO-2, and occludin showed increased junctional localization when 10T1/2 cells were present. Cocultures also displayed a significantly higher permeability barrier for the tracer molecule biotin-dextran. In conclusion, mural cells such as smooth muscle cells and pericytes may be important for stabilizing endothelial cell-to-cell contacts and may influence vessel-type specific differences of the endothelial phenotype.

Angiogenesis induction and regression in human surgical wounds

Angiogenesis in human wound healing is not well characterized, with only sparse information available regarding the maturation and fate of vessels formed as a consequence of human tissue repair. Therefore, this study aimed to establish the temporal profile of angiogenesis in human dermal wounds. Punch biopsies were obtained under local anesthesia from 45 patients following breast surgery. Scars were predominantly between 2 and 52 weeks after surgery but in five patients were > 52 weeks. Control samples were taken from breast skin peroperatively (n = 24). Quantification of vascular density was performed using the Chalkley grid, following antibody staining for platelet endothelial cell adhesion molecule. Vascular patterns, wound cellularity and morphology were also determined. Cumulative microvessel density was increased in all samples when compared to controls (p < 0.05). This was greatest 2 to 24 weeks following surgery 17 (15-21) median (range), decreased thereafter, but remained elevated compared to controls even in the mature scars > 52 weeks. Control tissue showed an ordered morphological arrangement of dermal structures, collagen, and elastic fibers. However, wounding resulted in marked structural distortion for up to 15 weeks. In conclusion, this study shows for the first time the prolonged persistence of both microvessels and cellularity (fibroblastic cells), in addition to structural distortion in human dermal wounds, which is in contrast to previous in vitro and in vivo studies.

Multinucleate cell angiohistiocytoma: a fibrohistiocytic proliferation with increased mast cell numbers and vascular hyperplasia

BACKGROUND

Multinucleate cell angiohistiocytoma (MCAH) is an uncommon lesion clinically characterized by multiple papules usually located on the face and acral regions of elderly women. Histopathologically, MCAH is characterized by dermal vascular hyperplasia associated with increased number of factor XIIIa-positive fibrohistiocytic cells and multinucleate cells with scalloped borders.

METHODS

We report the clinical, histopathological and immunohistochemical features of three cases of MCAH, with ulstrastructural study in one of them. The patients were a woman and two men of 56, 40 and 70 years of age, respectively. They all had multiple dull-red papules, which had appeared over several years and were located on the face, the trunk and the dorsa of the hands, respectively.

RESULTS

The reticular dermis presented a fibrohistiocytic proliferation of factor XIIIa-positive cells, with abundant bizarre multinucleate cells and vascular hyperplasia. Increased mast cell numbers were seen in all cases, often in apposition to multinucleate cells.

CONCLUSION

Histopathological differential diagnosis of MCAH includes mainly angiofibromas and dermatofibromas, even though vascular hyperplasia can be prominent and has led to many authors to classify MCAH among vascular tumors. Bizarre multinucleate cells can be found in reactive, neoplastic and inflammatory lesions in many sites of the body, and mast cells can play a role in their morphogenesis.