Bio

Academic Appointments


Publications

Journal Articles


  • Does transformation of microvascular endothelial cells into myofibroblasts play a key role in the etiology and pathology of fibrotic disease? MEDICAL HYPOTHESES Karasek, M. A. 2007; 68 (3): 650-655

    Abstract

    Fibrosis is a major cause of human death and disability. It has been hypothesized widely that activation of resident tissue fibroblasts is responsible for the increase in matrix protein synthesis present in fibrotic tissue. More recent studies in vitro of the physiology of human dermal microvascular endothelial cells and their transformation into spindle-shaped cells by proinflammatory cytokines may provide a new explanation for the increase in myofibroblasts in fibrotic diseases. In cell culture human dermal microvascular endothelial cells transform reversibly into 2 distinct cell phenotypes observed in the endothelium in vivo: an epithelioid phenotype present in a homeostatic microvasculature and a more spindle-shaped phenotype present in an inflammed and a reactive microvasculature. When epithelioid endothelial cell cultures are exposed to proinflammatory cytokines typically increased in fibrosis in vivo (e.g. TNF-alpha and IL-beta) for sustained periods, epithelioid dermal microvascular endothelial cells transform into a spindle-shaped morphology. Many of the transformed cells are identified as myofibroblast-like cells by electron microscopy (cytoplasmic microfilaments with attachment plaques), matrix protein synthesis (type I collagen, alpha smooth muscle actin, calponin) and by RT-PCR analysis of matrix protein mRNA. Following injury to an endothelial cell culture a similar (but reversible) transformation into myofibroblast-like cells also is induced. Drugs known to slow the clinical progression to fibrosis in vivo (e.g. phosphodiesterase inhibitors, antibodies to inflammatory cytokines) are the the same drug types capable of inhibiting endothelial cell tranformation in vitro. The in vivo and in vitro observations made on blood vessel physiology and pathology following sustained inflammation support a hypothesis that endothelial cell transformation into myofibroblast-like cells may begin to explain the increase in matrix proteins and myofibroblasts pathognomonic of fibrotic disease. The experimental and clinical evidence leading to and supporting this hypothesis is presented and discussed in this report.

    View details for DOI 10.1016/j.mehy.2006.07.053

    View details for Web of Science ID 000244232500028

    View details for PubMedID 17045756

  • Mechanisms of microvascular wound repair II. Injury induces transformation of endothelial cells into myofibroblasts and the synthesis of matrix proteins IN VITRO CELLULAR & DEVELOPMENTAL BIOLOGY-ANIMAL Chaudhuri, V., Karasek, M. A. 2006; 42 (10): 314-319

    Abstract

    Under normal growth conditions, in vitro dermal microvascular endothelial cells (HDMEC) retain an epithelioid morphology and do not synthesize matrix proteins found increased in scar tissue. When injured by a standard scratch, cells at the wound edge and within the culture transform into spindle-shaped, myofibroblast-like cells. To determine if the transformed cells synthesize matrix proteins, expression of type I collagen and alpha smooth muscle actin (alpha-SMA) was investigated by immunohistochemistry and quantitative reverse transcriptase-polymerase chain reaction (RT-PCR). Twelve hours following injury, a major upregulation in expression of alpha-SMA and type I collagen was observed both in cells proximal and distal to the wound edge. Cells with the typical morphology of myofibroblasts and displaying intracellular alpha-SMA positive fibrils were observed in HDMEC throughout the culture. In contrast, type IV collagen, a basement membrane protein, was not detected in migrating cells. Following completion of wound repair (24-36 h), type I collagen was no longer expressed and type IV collagen synthesis increased to prewound levels. Quantitative RT-PCR confirmed the changes in gene expression for both type I collagen and alpha-SMA at each time point during repair. These results demonstrate that normal skin microvascular endothelial cells retain an ability to transform into myofibroblast-like cells when injured and to synthesize matrix proteins not expressed in noninjured cells. The synthesis of matrix proteins by injured endothelial cells suggests a direct role for the endothelium in the pathology of scar formation.

    View details for Web of Science ID 000243666400007

    View details for PubMedID 17316065

  • Mechanisms of microvascular wound repair I. Role of mitosis, oxygen tension, and I-kappa B IN VITRO CELLULAR & DEVELOPMENTAL BIOLOGY-ANIMAL Chaudhuri, V., Potts, B. R., Karasek, M. A. 2006; 42 (10): 308-313

    Abstract

    To better understand the mechanisms of both normal reendothelialization and neointimal hyperplasia following injury, human dermal microvascular endothelial cells (HDMEC) were isolated from neonatal foreskin and studied in an in vitro model of the microvascular endothelium. In a standard 3-mm wound of nonproliferative HDMEC cultures, reendothelialization was complete at 32 h at a 20.8% (atmospheric) O(2) level. Inhibition of mitosis by mitomycin C did not reduce reendothelialization and both actinomycin D and cycloheximide inhibited repair by 80%. To determine if signals from injured cells communicated with noninjured cells, diffusion of the dye Lucifer Yellow was followed into injured and surrounding noninjured HDMEC. Diffusion was increased into both injured and noninjured cells, indicating a role for gap junctional intercellular communication (GJIC) in HDMEC wound repair. To determine if a more physiologic O(2) tension (5%) also increased vascular repair, reendothelialization at 5% O(2) was compared to 20.8% O(2) (atmospheric) levels and found to be increased by up to 50% at 5% O(2) at 12 and 24 h postinjury. I-kappa B alpha, the inhibitory subunit of NF-kappa B (a transcription factor activated by oxidative stress), was upregulated following wounding. Retroviral transfection of I-kappa B alpha into HDMEC increased the rate of reendothelialization by 35%, supporting an inhibitory role for NF-kappa B in the control of HDMEC migration.

    View details for Web of Science ID 000243666400006

    View details for PubMedID 17316064

  • Overexpression of laminin-8 in human dermal microvascular endothelial cells promotes angiogenesis-related functions JOURNAL OF INVESTIGATIVE DERMATOLOGY Li, J., Zhou, L., Tran, H. T., Chen, Y., Nguyen, N. E., Karasek, M. A., Marinkovich, M. P. 2006; 126 (2): 432-440

    Abstract

    This study examined the effects of endogenous overexpression of laminin-8 on angiogenesis and wound healing in primary human dermal microvascular endothelial cells (HDMECs). HDMECs expressed laminin-8 and laminin-10, but no other laminins, as determined by radioimmunoprecipitation assay using a panel of antibodies to individual laminin chains. To study laminin-8 function, full-length human laminin alpha4 cDNA was retrovirally transferred to HDMEC, and specific overexpression of laminin-8 was verified by Western blot. Laminin-8 overexpression promoted endothelial cell spreading and migration in scratch assays and accelerated angiogenic tubule formation in collagen gel overlay assays. Strong inhibitory effect of beta1 integrin and weak inhibition by alphavbeta3 integrin antibodies were observed in laminin-8-stimulated cell migration, but only beta1 integrin antibodies affected tubule formation. These studies suggest that laminin-8 overexpression may prove to be a useful method to engineer HDMECs to promote angiogenesis and wound repair.

    View details for DOI 10.1038/sj.jid.5700089

    View details for Web of Science ID 000238968400028

    View details for PubMedID 16374451

  • Regulation of skin microvasculature angiogenesis, cell migration, and permeability by a specific inhibitor of PKC alpha JOURNAL OF INVESTIGATIVE DERMATOLOGY Bokhari, S. M., Zhou, L., Karasek, M. A., Paturi, S. G., Chaudhuri, V. 2006; 126 (2): 460-467

    Abstract

    Activation of protein kinase C (PKC) induces phenotypic changes in the morphology of microvascular endothelial cells that affect major functions of the microvasculature. These functions include the first stages of sprouting in angiogenesis, cell migration following wounding, and vascular permeability. The specific isoform(s) of PKC responsible for each of these changes has not been previously identified. In this study, we used two inflammatory agents, IL-1beta and phorbol myristic acetate, to activate PKC isozymes and specific inhibitors of PKCalpha (Gö6976) and PKCbeta (hispidin) to distinguish how each of these isoform(s) controls angiogenesis, wound healing, and permeability. In all cases, only inhibition of PKCalpha inhibited each of these functions when compared to the inhibition of PKCbeta. Additional analysis of the mechanism of action of Gö6976 (RT-PCR, Western blots, and immunohistochemistry) of the changes in the phosphorylated and nonphosphorylated forms of PKCalpha in the cell membrane and cytoplasm confirmed the specificity of PKCalpha inhibition by Gö6976. These studies therefore indicate a specific and a regulatory role of the PKCalpha isoform in three major endothelial cell functions that are important in the maintenance of microvascular homeostasis.

    View details for DOI 10.1038/sj.jid.5700071

    View details for Web of Science ID 000238968400031

    View details for PubMedID 16374459

  • Progress in our understanding of the biology of psoriasis CUTIS Karasek, M. A. 1999; 64 (5): 319-322

    Abstract

    This review describes the progress made in our understanding of the basic biology of psoriasis and how newer, safer clinical approaches to control the disease may result from these developments. It reveals how epidermal hyperproliferation can be permanently induced using transgenic mouse models, how the discovery of methods to generate humanized mouse monoclonal antibodies may be used to control the synthesis of autocrine and paracrine growth factors, how programmed cell death (apoptosis) is regulated in the epidermis, and how the abnormal synthesis of superantigens, cytokines, and chemokines can result in immune dysfunction and generate increased angiogenesis, inflammation, and epidermal hyperproliferation.

    View details for Web of Science ID 000083777500006

    View details for PubMedID 10582156

  • Interleukin-1 induces major phenotypic changes in human skin microvascular endothelial cells JOURNAL OF CELLULAR PHYSIOLOGY Romero, L. I., Zhang, D. N., Herron, G. S., Karasek, M. A. 1997; 173 (1): 84-92

    Abstract

    To determine the role of the pleiotropic cytokine interleukin-1 (IL-1) on the activation of endothelial cells during inflammation and angiogenesis, pure populations of human dermal microvascular endothelial cells (HDMEC) were obtained by immunoaffinity purification using Ulex europaeus agglutinin-1 and platelet endothelial cell adhesion molecule-1 (PECAM-1) antibody. Exposure of HDMEC to IL-1beta induced morphologic and physiologic changes characterized by 1) phenotypic modulation of endothelial cells from epithelioid to spindle-shaped cells accompanied by reorganization of vimentin filaments; 2) gradual decrease to a complete absence of the endothelial cell markers von Willebrand factor (vWf) and PECAM-1; and 3) increased capability to form tubule-like structures when overlaid with collagen gels. The IL-1 effect on cell morphology, growth, and decrease of endothelial cell antigens was potentiated by basic fibroblast growth factor (bFGF). Similar results were observed in mitotically arrested gamma-irradiated cells demonstrating that the spindle-shaped cells observed after IL-1 stimulation were derived from epithelioid endothelial cells and that DNA synthesis was not required to effect these changes. Immunostaining with an antibody specific for human fibroblasts was negative and further confirmed the endothelial cell origin of the spindle-shaped cells. These data demonstrate that IL-1 can induce phenotypic changes in HDMEC from epithelioid to spindle-shaped, mesenchymal-like cells, that these cells are more susceptible to stimulation by bFGF, and that they lose biochemical and functional properties characteristic of epithelioid HDMEC.

    View details for Web of Science ID A1997XY74500010

    View details for PubMedID 9326452

  • Interleukin-10 induces E-selectin on small and large blood vessel endothelial cells JOURNAL OF EXPERIMENTAL MEDICINE Vora, M., Romero, L. I., Karasek, M. A. 1996; 184 (3): 821-829

    Abstract

    In vitro, expression of E-selectin is largely restricted to endothelial cells activated by inflammatory cytokines. Under activated conditions, cytokines such as interleukin (IL) 10, released by keratinocytes in large quantities, may also increase the expression of E-selectin on the dermal microvasculature. The aim of the present study was to investigate the expression of E-selectin on cultured human dermal microvascular endothelial cells (HDMEC) isolated from neonatal foreskins when exposed to IL-10. Expression of E-selectin was determined by immunofluorescence microscopy, FACS analysis, an HL-60 cell-binding assay, and quantitative polymerase chain reaction (PCR) analysis. For comparison with large blood vessel cells, the expression of E-selectin on human umbilical vein endothelial cells (HUVEC) was also determined in parallel by FACS and reverse transcriptase-PCR analysis under identical conditions. These studies demonstrate that IL-10 induces the expression of E-selectin on both HDMEC and HUVEC and that the level of expression of HDMEC is comparable with that induced by IL-1 beta and tumor necrosis factor-alpha. When HL-60 cells are incubated with HDMEC pretreated with IL-10, a consistent increase in adherence of HL-60 to endothelial cells is observed. This adherence was found to be mediated by L-selectin. PCR analysis and the quantification of E-selectin cDNA by a novel, highly sensitive and specific PCR-immunoassay demonstrate the induction of E-selectin mRNA at the transcriptional level. The induction of the expression of E-selectin by IL-10 on HDMEC may provide additional insights into the pathogenic mechanism of neutrophil accumulation at the site of inflammation in inflammatory skin diseases.

    View details for Web of Science ID A1996VG86800004

    View details for PubMedID 9064342

  • Differential activation of protein kinase C isozymes by phorbol ester and collagen in human skin microvascular endothelial cells JOURNAL OF INVESTIGATIVE DERMATOLOGY Zhou, L. Y., Disatnik, M. H., Herron, G. S., Rosen, D. M., Karasek, M. A. 1996; 107 (2): 248-252

    Abstract

    Human dermal microvascular endothelial cells participate in activities including inflammation, wound healing, and angiogenesis (neovascularization). Two stages of angiogenesis can be mimicked in vitro by two models of cultured foreskin human dermal microvascular endothelial cells: the differentiation of epithelioid endothelial cells to spindle-shaped mesenchymal-like cells induced by phorbol ester treatment; and the formation of vascular channels induced by exposing the luminal surface of endothelial cell monolayers to type I collagen gels. The mechanisms underlying these two processes, however, are largely unknown. Protein kinase C isozymes, which are activated by phorbol esters, are important mediators in the angiogenic process. In the current work, we identified the protein kinase C isozymes present in human dermal microvascular endothelial cells and determined which of the isozymes are activated in response to phorbol ester or to collagen treatments. Using western blot analysis, we found that microvascular endothelial cells contain at least six protein kinase C isozymes (alpha, beta, delta, epsilon, zeta, eta). Immunocytochemical studies demonstrated that the isozymes are located in distinct cellular compartments and that following treatment with phorbol 12-myristate 13-acetate or with a collagen gel overlay, most isozymes (protein kinase C alpha, beta1, betaII, delta, epsilon, eta) translocated to different parts of the cell. Moreover, for two of these isozymes (betaII and eta), the localization differs after phorbol 12-myristate 13-acetate treatment as compared with collagen treatment. These results demonstrate that agents that mimic two stages in the angiogenic process in vitro initiate diverse changes in the subcellular localization of specific protein kinase C isozymes and suggest a role for different isozymes in this process.

    View details for Web of Science ID A1996UY64200019

    View details for PubMedID 8757771

  • A METHOD FOR THE ISOLATION AND SERIAL PROPAGATION OF KERATINOCYTES, ENDOTHELIAL-CELLS, AND FIBROBLASTS FROM A SINGLE PUNCH BIOPSY OF HUMAN SKIN IN VITRO CELLULAR & DEVELOPMENTAL BIOLOGY-ANIMAL Normand, J., Karasek, M. A. 1995; 31 (6): 447-455

    Abstract

    When multiple types of cells from normal and diseased human skin are required, techniques to isolate cells from small skin biopsies would facilitate experimental studies. The purpose of this investigation was to develop a method for the isolation and propagation of three major cell types (keratinocytes, microvascular endothelial cells, and fibroblasts) from a 4-mm punch biopsy of human skin. To isolate and propagate keratinocytes from a punch biopsy, the epidermis was separated from the dermis by treatment with dispase. Keratinocytes were dissociated from the epidermis by trypsin and plated on a collagen-coated tissue culture petri dish. A combination of two commercial media (Serum-Free Medium and Medium 154) provided optimal growth conditions. To isolate and propagate microvascular endothelial cells from the dermis, cells were released following dispase incubation and plated on a gelatin-coated tissue culture dish. Supplementation of a standard growth medium with a medium conditioned by mouse 3T3 cells was required for the establishment and growth of these cells. Epithelioid endothelial cells were separated from spindle-shaped endothelial cells and from dendritic cells by selective attachment to Ulex europeus agglutinin I-coated paramagnetic beads. To establish fibroblasts, dermal explants depleted of keratinocytes and endothelial cells were attached to plastic by centrifugation, and fibroblasts were obtained by explant culture and grown in Dulbecco's modified Eagle's medium (DMEM) containing fetal bovine serum (FBS). Using these isolation methods and growth conditions, two confluent T-75 flasks of keratinocytes, one confluent T-25 flask of purified endothelial cells, and one confluent T-25 flask of fibroblasts could be routinely obtained from a 4-mm punch biopsy of human skin.(ABSTRACT TRUNCATED AT 250 WORDS)

    View details for Web of Science ID A1995RG48300011

    View details for PubMedID 8589888

  • ANTIGEN PRESENTATION BY HUMAN DERMAL MICROVASCULAR ENDOTHELIAL-CELLS - IMMUNOREGULATORY EFFECT OF IFN-GAMMA AND IL-10 JOURNAL OF IMMUNOLOGY Vora, M., Yssel, H., deVries, J. E., Karasek, M. A. 1994; 152 (12): 5734-5741

    Abstract

    Human dermal microvascular endothelial cells (HDMEC) play a central role in many aspects of the inflammatory and immune reactions in skin. HDMEC display a phenotypic diversity ranging from cells with an epithelioid morphology to those that show both morphologic and biochemical characteristics of macrophages. Here it is shown that HDMEC possess the capability to both process and present Ags. T lymphocyte clones specific for peptide p94-104, which are derived from the protein of group I allergen of Dermatophagoides pteronyssinus, a major house dust mite allergen, and restricted by HLADR11, proliferated specifically to stimulation with the group I allergen of D. pteronyssinus and with peptide p94-104 presented by HDMEC. Preincubation for 48 h with IFN-gamma enhanced the expression of class II MHC Ags on HDMEC, which in turn increased the capacity of HDMEC to present Ag. When HDMEC were primed with Ag in the presence of IL-10, a 75% inhibition of Ag-specific T cell proliferation was observed. IL-10 also inhibited T cell proliferation induced by IFN-gamma-stimulated HDMEC. These findings demonstrate that HDMEC possess the ability to process and present Ag to CD4+ T cells and that these reactions are stimulated by IFN-gamma and inhibited by IL-10. The reduced Ag-presenting capacity of HDMEC mediated by IL-10 is not associated with a down-regulation of class II MHC expression. No significant reduction of HLA-DR expression was detected either at the protein or gene level when HDMEC were incubated with IFN-gamma and IL-10 as compared with incubation with IFN-gamma alone. The profound down-regulatory effect of IL-10 on Ag presentation may provide a new pharmacologic approach to control inflammatory responses in skin.

    View details for Web of Science ID A1994NQ73200014

    View details for PubMedID 8207203

  • RETINOIDS UP-REGULATE PHAGOCYTOSIS BY HUMAN DERMAL MICROVASCULAR ENDOTHELIAL-CELLS JOURNAL OF CELLULAR PHYSIOLOGY Vora, M., Karasek, M. A. 1994; 159 (3): 450-456

    Abstract

    Animals fed a diet deficient in vitamin A show severe physiological changes that often result in death. At the cellular level, retinoids have been shown to induce differentiation of cells derived from a wide spectrum of tissues, including the vasculature. To understand further the mechanisms for these events, we studied the effects of 13-cis-retinoic acid, all-trans-retinoic acid, all-trans-retinol, and all-trans-retinol acetate on human dermal microvascular endothelial cells (HDMEC). Concentrations of retinoids in the physiological range from 0 to 1 microM were used in our experiments. These concentrations were nontoxic to HDMEC. Here we report that in addition to the known effect of retinoids on keratinocytes and sebacytes, retinoids induced morphological and functional changes in HDMEC that gave these cells macrophage like characteristics. 13-Cis-retinoic acid and all-trans-RA induced HDMEC to phagocytize and to increase the production of hydrogen peroxide and superoxide anion. These two retinoids also changed the morphology of endothelial cells from typical small compact cuboidal epithelioid cells to cells with larger cytoplasm and indistinct cell membranes. The retinoid-stimulated HDMEC deposited increased amounts of extracellular matrix. All-trans-retinol and all-trans-retinol acetate did not significantly affect HDMEC in all parameters tested. The induction of these properties provides a new model with which to study how retinoids regulate gene expression using a normal, nontransformed cell line.

    View details for Web of Science ID A1994NM39900008

    View details for PubMedID 8188762

  • ORIGIN OF SPINDLE-SHAPED CELLS IN KAPOSI-SARCOMA LYMPHOLOGY Karasek, M. A. 1994; 27 (1): 41-44

    Abstract

    Adult skin microvascular endothelial cells derived from new born foreskin were grown and maintained in tissue culture with and without dibutyryl cyclic AMP (DC-AMP) and isobutyl methyl xanthine (IMX). Whereas in the presence of DC-AMP and IMX, the cells showed the typical cobblestone appearance of endothelium, in the absence of these agents the cultured cells permanently converted to a spindle-shaped configuration. Because this phenomenon of transdifferentiation also occurs in the presence of specific cytokines, the profile of which is notoriously altered in acquired immunodeficiency syndrome (AIDS), the findings support the concept that in Kaposi sarcoma the spindle-shaped cells derive from dysfunction in the microvascular environment.

    View details for Web of Science ID A1994NE55100005

    View details for PubMedID 7516025

  • Modification of proto-oncogene expression by phorbol esters in human dermal microvascular endothelial cells. Cellular and molecular biology MANSBRIDGE, J. N., GRYMES, R. A., Karasek, M. A. 1992; 38 (7): 791-798

    Abstract

    Following activation with the inflammatory mediator phorbol myristate acetate (PMA), human microvascular endothelial cells (DMEC) is olated from the human dermis (DMEC) rapidly and dramatically convert from a classical epithelioid morphology to a spindle-shaped configuration. This is accompanied by changes in the organization of gap junctions and the vimentin and actin cytoskeletons. This report describes the sequential changes in the expression of four proto-oncogenes, c-fos, c-myc, c-sis and H-ras in DMEC following PMA exposure. The synthesis of c-fos mRNA was transiently induced by PMA from a basal concentration below the limit of detection to a maximum at 60 min., declining to the unstimulated level within 2 hrs. Synthesis of c-myc mRNA declined continuously and reached 37% of control levels over 16 hrs. Expression of c-sis which encodes for the B chain of platelet-derived growth factor, also declined to 34% of the control value over 16 hrs. There was no change in the synthesis of H-ras mRNA nor of beta-actin mRNA which was used as a control. The expression of c-myc in normal DMEC was compared to a human dermal microvascular cell line transformed by SV-40 (TREND). The TREND cell line maintains a permanent spindle-shaped configuration under all growth conditions and multiplies faster than DMEC. In contrast to the non-transformed cell cultures, expression of c-myc in TREND cells was induced by PMA.(ABSTRACT TRUNCATED AT 250 WORDS)

    View details for PubMedID 1472905

  • HISTAMINE-MODULATED TRANSDIFFERENTIATION OF DERMAL MICROVASCULAR ENDOTHELIAL-CELLS EXPERIMENTAL CELL RESEARCH LIPTON, B. H., Bensch, K. G., Karasek, M. A. 1992; 199 (2): 279-291

    Abstract

    Homeostatic and inflammatory functions of skin microvessels are tightly regulated by vasoactive amines. Following stimulation with histamine, dermal microvascular endothelial cells (MEC) undergo a rapid change in phenotype (transdifferentiation) and subsequently exhibit an enhanced rate of growth. To elucidate mechanisms regulating MEC transdifferentiation, this study investigated the functional relationships among vimentin, Ca2+, and protein kinase C (PKC) in histamine-modulated dermal MEC in vitro. Distribution of vimentin and PKC in foreskin-derived MEC cultivated in a modified Iscove's medium was assessed with immunocytochemistry. Calcium ion kinetics in histamine-treated MEC were analyzed using the Ca2+ probe Fluo-3 in conjunction with interactive laser cytometry. Histamine, acting through H-1 receptors, produces a rapid (less than 100 ms) and differential elevation of free calcium in each of three cytological compartments defined by the vimentin cytoskeleton in epithelial MEC. A distinctive compartmentalized and nonuniform distribution of PKC precisely coincides with that observed for free-Ca2+ released in response to histamine. The studies reveal that histamine modulation of the MEC phenotype is associated with a rapid patterned reorganization of the vimentin skeleton. It is hypothesized that histamine induces vimentin post-translational modifications by activating a spatially localized interaction among cytoplasmic free Ca2+, PKC, and the vimentin matrix. The results further suggest that vimentin, in addition to its structural role, may participate in signal transduction and gene regulation processes in effecting MEC transdifferentiation.

    View details for Web of Science ID A1992HJ65900014

    View details for PubMedID 1544369

  • MECHANISMS OF ANGIOGENESIS IN NORMAL AND DISEASED SKIN INTERNATIONAL JOURNAL OF DERMATOLOGY Karasek, M. A. 1991; 30 (12): 831-836

    View details for Web of Science ID A1991GR82400001

    View details for PubMedID 1726168

  • MICROVESSEL ENDOTHELIAL-CELL TRANSDIFFERENTIATION - PHENOTYPIC CHARACTERIZATION DIFFERENTIATION LIPTON, B. H., Bensch, K. G., Karasek, M. A. 1991; 46 (2): 117-133

    Abstract

    Human dermal microvessel endothelial cells (MEC) have two basic functions: maintenance of tissue homeostasis and facilitation of inflammatory responses. The former requires that the endothelium expresses traits of an epithelium, while inflammatory reactions are associated with intimal disruption. Acute inflammation transiently alters endothelium, whereas chronic inflammation may result in vessel reorganization and MEC mesenchymalization. Foreskin MEC in vitro undergo a similar epithelial-mesenchymal modulation. In the presence of cAMP, cultivated dermal MEC exhibit the structural and functional characteristics of an epithelium. MEC grown in cAMP-deficient medium initially have a "transitional" configuration and are subsequently transformed into mesenchymal cells. If cAMP is replaced by histamine, MEC maintain a stable intermediate transitional configuration. Transitional MEC refed cAMP-supplemented medium revert to an epithelial phenotype, whereas parallel cultures fed cAMP-deficient medium are transformed into mesenchymal cells. Phenotypic modulation can be induced without cell division and thus provides a unique example of direct transdifferentiation. Our data furthermore suggest that this transdifferentiation results in the acquisition of properties usually attributed to cells of the reticuloendothelial system.

    View details for Web of Science ID A1991FH02200006

    View details for PubMedID 1648522

  • NEW DEVELOPMENTS IN OUR UNDERSTANDING OF THE BIOLOGY OF PSORIASIS CUTIS Karasek, M. A. 1990; 46 (4): 307-310

    Abstract

    Increased keratinocyte proliferation and inflammation are two hallmarks of psoriasis. In this paper new developments in skin biology and biochemistry that help us to understand these two features of the disease are discussed. Methods to control proliferation and inflammation based on these scientific developments are presented.

    View details for Web of Science ID A1990EC01900004

    View details for PubMedID 2261788

  • CYCLIC ADENOSINE-MONOPHOSPHATE LEVELS AND THE FUNCTION OF SKIN MICROVASCULAR ENDOTHELIAL-CELLS JOURNAL OF CELLULAR PHYSIOLOGY Tuder, R. M., Karasek, M. A., Bensch, K. G. 1990; 142 (2): 272-283

    Abstract

    The maintenance of the normal epithelioid morphology of human dermal microvascular endothelial cells (MEC) grown in vitro depends strongly on the presence of factors that increase intracellular levels of cyclic AMP. Complete removal of dibutyryl cAMP and isobutylmethylxanthine (IMX) from the growth medium results in a progressive transition from an epithelioid to a spindle-shaped cell line. This transition cannot be reversed by the readdition of dibutyryl cAMP and IMX to the growth medium or by addition of agonists that increase cAMP levels. Spindle-shaped MEC lose the ability to express Factor VIII rAG and DR antigens and to bind peripheral blood mononuclear leukocyte (PBML). Ultrastructural analyses of transitional cells and spindle-shaped cells show decreased numbers of Weibel-Palade bodies in transitional cells and their complete absence in spindle-shaped cells. Interferon-gamma alters several functional properties of both epithelioid and spindle-shaped cells. In the absence of dibutyryl cAMP it accelerates the transition from epithelial to spindle-shaped cells, whereas in the presence of cyclic AMP interferon-gamma increases the binding of PBMLs to both epithelioid and spindle-shaped MEC and the endocytic activity of the endothelial cells. These results suggest that cyclic AMP is an important second messenger in the maintenance of several key functions of microvascular endothelial cells. Factors that influence the levels of this messenger in vivo can be expected to influence the angiogenic and immunologic functions of the microvasculature.

    View details for Web of Science ID A1990CP03800008

    View details for PubMedID 1689317

  • Microvascular endothelial cell culture. journal of investigative dermatology Karasek, M. A. 1989; 93 (2): 33S-38S

    Abstract

    Microvascular endothelial cells play a central role in inflammation, tumor metastasis, and wound healing. Methods to study these processes in vitro using cells isolated from adult skin, from the inner and the outer segments of the neontal foreskin, and from experimental animals are reviewed. A new modified Iscove's medium supplemented with 2% pre-partum maternal serum, dibutyryl cyclic AMP, isobutyl methylxanthine, thymidine, and hypoxanthine is described. This modified medium supports growth of both adult and neonatal endothelial cells up to seven passages with retention of cytologic markers closely identified with endothelial cells (Weibel-Palade bodies, Factor VIII-associated antigen). Several functions associated with the microvasculature in situ are expressed by microvascular endothelial cells in cell culture. Such functions include the formation of a basement membrane, angiogenesis, intercelluar gap formation in response to vasoactive agents, and the attachment and migration of lymphocytes through endothelial monolayers.

    View details for PubMedID 2666521

  • PREFERENTIAL BINDING OF MONOCYTES AND LEU-2 + LYMPHOCYTES-T TO INTERFERON-GAMMA TREATED CULTURED SKIN ENDOTHELIAL-CELLS AND KERATINOCYTES ARCHIVES OF DERMATOLOGICAL RESEARCH Nickoloff, B. J., REUSCH, M. K., Bensch, K., Karasek, M. A. 1988; 280 (4): 235-245

    Abstract

    Recombinant gamma interferon (r-IFN-gamma) increases the adherence of peripheral blood mononuclear leukocytes (PBMLs) to cultured keratinocytes and cutaneous microvascular endothelial cells (MECs). To determine which specific type of PBMLs bound to these r-IFN-gamma treated cells, we performed immunophenotyping on the adherent PBMLs. The adherent PBMLs were detached from the r-IFN-gamma treated keratinocytes and MECs by adding EDTA, and collected by cytocentrifugation, followed by immunocytochemical staining using a panel of monoclonal antibodies. Our results reveal that the relative adherent population of PBMLs was composed of approximately 60%-70% monocytes and 18%-24% Leu 2+ T lymphocytes (T-cytotoxic/suppressor) which preferentially bound to r-IFN-gamma treated keratinocytes and MECs. There was some lesser binding by Leu 3 + lymphocytes (T-helper/inducer); approximately 8%, and no binding of B lymphocytes. Since r-IFN-gamma also induced HLA-DR expression in keratinocytes and MECs, these in vitro data suggest that r-IFN-gamma may play an important role in the immunobiology of diverse skin diseases such as graft vs host disease, lichen planus, and other inflammatory dermatoses, because the keratinocytes express HLA-DR and the predominant T-cell subset in the epidermis is Leu 2 + (over the Leu 3 + T cell) in all of these conditions. These results represent a direct attempt to explain in situ immunophenotypic mononuclear leukocyte subset distribution patterns by using r-IFN-gamma and purified cultured cells such as keratinocytes and MECs. We propose that IFN-gamma, by both increasing the adherence of PBMLs, and promoting selective binding of monocytes and Leu 2 + T lymphocytes to both keratinocytes and MECs, may be important in regulating PBML localization and recirculation in the skin.

    View details for Web of Science ID A1988P027800008

    View details for PubMedID 2466443

  • EFFECT OF NEUROPEPTIDES PRESENT IN SKIN ON THE PROLIFERATION OF HUMAN PERIPHERAL-BLOOD MONONUCLEAR-CELLS AND T-CELLS ARCHIVES OF DERMATOLOGICAL RESEARCH REUSCH, M. K., Karasek, M. A., Nickoloff, B. J. 1988; 280 (5): 279-281

    Abstract

    The release of neuropeptides, such as substance P (SP) and somatostatin (SOM), from primary sensory nerve fibers has been implicated in the modulation of local immune responses in surface tissues, such as the skin, the pulmonary airways, and the gastrointestinal mucosa. We have investigated the influence of six neuropeptides substance P (SP), somatostatin (SOM), substance K (SK), vasoactive intestinal peptide (VIP), bombesin (BOM), and adrenocorticotropic hormone (ACTH) on the proliferation of resting and partially stimulated human peripheral blood mononuclear leukocytes (PBMLs) and T lymphocytes. Neuropeptides in concentrations from 10(-7) to 10(-12) M were added to either resting or partially stimulated cells [interleukin-2 (IL-2), concanavalin A (Con A), and phytohemagglutinin (PHA)]. Cellular proliferation was assessed by incorporation of 3H-thymidine after 72 h. With the exception of SP, no significant effect of any of these neuropeptides on 3H-thymidine incorporation was found. In resting cells, 10(-9) MSP elicits an 80...maximal increase of 3H-thymidine incorporation, whereas no statistically significant effect on partially stimulated leukocytes was found. These results contradict a previous report on a significant mitogenic effect of SP on partially stimulated T cells. Considering the very minimal effect of SP on resting cells and, particularly, the absence of an effect on partially stimulated cells, we would question a significant modulatory role for SP and the five other neuropeptides in the proliferation of immunocompetent cells in skin.

    View details for Web of Science ID A1988P501600004

    View details for PubMedID 2460035

  • LEUKOTRIENE-B4 ENHANCES ADHERENCE OF HUMAN POLYMORPHONUCLEAR LEUKOCYTES TO DERMAL MICROVASCULAR ENDOTHELIAL-CELLS INVITRO ARCHIVES OF DERMATOLOGICAL RESEARCH REUSCH, M. K., FULLERTON, S. H., Nickoloff, B. J., Glinski, W., Karasek, M. A. 1988; 280 (4): 194-197

    Abstract

    Adherence of polymorphonuclear leukocytes (PMNs) to endothelial cells (ECs) is a crucial step in the diapedesis of inflammatory cells to the site of inflammation. We have demonstrated that leukotriene B4 (LTB4), a metabolite of the arachidonic acid cascade, and N-formyl-L-methionyl-L-leucyl-L-phenylalanine (FMLP) significantly enhance the binding of human PMNs to selected populations of human dermal microvascular endothelial cells (MECs) in vitro. MECs were isolated from the vascular-rich portion of foreskins of newborns. MECs were grown in Iscove's modified Dulbecco's media with 2% prepartum serum and 8% newborn calf serum on 1% gelatin-coated plastic dishes. PMNs isolated from five human donors were added to the culture dishes for varying time intervals (usually 30 min) in the presence and absence of the chemotactic stimuli LTB4 and FMLP. Addition of PMNs to MECs in the absence of chemotactic stimuli results in "baseline" binding to the MEC monolayer. About one in every 150 ECs binds more than five PMNs. These selected ECs are randomly distributed throughout the monolayer. LTB4 from 10(-10) to 10(-7) M increases the number of MECs which selectively bind PMNs by 260% at 10(-7) M. FMLP also increases adherence in qualitatively and quantitatively similar fashion. These data support a role for LTB4 in the mediation of adherence of neutrophils to dermal MECs. In contrast to other endothelial cells from the large blood vessels, such as from umbilical veins or calf thoracic aortae, PMNs bind only to selected MECs in culture, even when stimulated with LTB4 or FMLP.(ABSTRACT TRUNCATED AT 250 WORDS)

    View details for Web of Science ID A1988P027800002

    View details for PubMedID 2852927

Stanford Medicine Resources: