Hyperactivity of fibroblasts cultured from psoriatic skin: I. Faster proliferation and effect of serum withdrawal

The mechano-chemical circuit in fibroblasts and dendritic cells drives basal cell proliferation in psoriasis

Psoriasis is an intractable immune-mediated disorder that disrupts the skin barrier. While studies have dissected the mechanism by which immune cells directly regulate epidermal cell proliferation, the involvement of dermal fibroblasts in the progression of psoriasis remains unclear. Here, we identified that signals from dendritic cells (DCs) that migrate to the dermal-epidermal junction region enhance dermal stiffness by increasing extracellular matrix (ECM) expression, which further promotes basal epidermal cell hyperproliferation. We analyzed cell-cell interactions and observed stronger interactions between DCs and fibroblasts than between DCs and epidermal cells. Using single-cell RNA (scRNA) sequencing, spatial transcriptomics, immunostaining, and stiffness measurement, we found that DC-secreted LGALS9 can be received by CD44+ dermal fibroblasts, leading to increased ECM expression that creates a stiffer dermal environment. By employing mouse psoriasis and skin organoid models, we discovered a mechano-chemical signaling pathway that originates from DCs, extends to dermal fibroblasts, and ultimately enhances basal cell proliferation in psoriatic skin.

Structural cell heterogeneity underlies the differential contribution of IL-17A, IL-17F and IL-23 to joint versus skin chronic inflammation

The current therapeutic strategy used in immune-mediated inflammatory diseases (IMIDs) primarily targets immune cells or associated-pathways. However, recent evidence suggests that the microenvironment modulates immune cell development and responses. During inflammation, structural cells acquire a pathogenetic phenotype and the interactions with immune cells are often greatly modified. Understanding the importance of these tissue-specific interactions may allow to explain why some biologics are effective in some IMIDs but not in others. The differential effects of interleukin (IL)-17 A, IL-17F and IL-23 in joint versus skin inflammation depends on structural cell heterogeneity. In addition, the sometimes opposite effects of immune/structural cell interactions on the production of these cytokines illustrate the importance of these cells in chronic inflammation, using the examples of rheumatoid arthritis, psoriasis and spondyloarthritis. This review describes these concepts, shows their interests through clinical observations, and finally discusses strategies to optimize therapeutic strategies.

New insight into the role of fibroblasts in the epithelial immune microenvironment in the single-cell era

The skin is exposed to environmental challenges and contains heterogeneous cell populations such as epithelial cells, stromal cells, and skin-resident immune cells. As the most abundant type of stromal cells, fibroblasts have been historically considered silent observers in the immune responses of the cutaneous epithelial immune microenvironment (EIME), with little research conducted on their heterogeneity and immune-related functions. Single-cell RNA sequencing (scRNA-seq) and spatial transcriptomics (ST) have overcome the limitations of bulk RNA sequencing and help recognize the functional and spatial heterogeneity of fibroblasts, as well as their crosstalk with other types of cells in the cutaneous EIME. Recently, emerging single-cell sequencing data have demonstrated that fibroblasts notably participate in the immune responses of the EIME and impact the initiation and progression of inflammatory skin diseases. Here, we summarize the latest advances in the role of fibroblasts in the cutaneous EIME of inflammatory skin diseases and discuss the distinct functions and molecular mechanisms of activated fibroblasts in fibrotic skin diseases and non-fibrotic inflammatory skin diseases. This review help unveil the multiple roles of fibroblasts in the cutaneous EIME and offer new promising therapeutic strategies for the management of inflammatory skin diseases by targeting fibroblasts or the fibroblast-centered EIME.

The p300/CBP Inhibitor A485 Normalizes Psoriatic Fibroblast Gene Expression In Vitro and Reduces Psoriasis-Like Skin Inflammation In Vivo

Psoriasis is a chronic inflammatory skin disease that often recurs at the same locations, indicating potential epigenetic changes in lesional skin cells. In this study, we discovered that fibroblasts isolated from psoriatic skin lesions retain an abnormal phenotype even after several passages in culture. Transcriptomic profiling revealed the upregulation of several genes, including the extra domain A splice variant of fibronectin and ITGA4 in psoriatic fibroblasts. A phenotypic library screening of small-molecule epigenetic modifier drugs revealed that selective CBP/p300 inhibitors were able to rescue the psoriatic fibroblast phenotype, reducing the expression levels of extra domain A splice variant of fibronectin and ITGA4. In the imiquimod-induced mouse model of psoriasis-like skin inflammation, systemic treatment with A485, a potent CBP/p300 blocker, significantly reduced skin inflammation, immune cell recruitment, and inflammatory cytokine production. Our findings indicate that epigenetic reprogramming might represent a new approach for the treatment and/or prevention of relapses of psoriasis.

Importance of lymphocyte-stromal cell interactions in autoimmune and inflammatory rheumatic diseases

Interactions between lymphocytes and stromal cells have an important role in immune cell development and responses. During inflammation, stromal cells contribute to inflammation, from induction to chronicity or resolution, through direct cell interactions and through the secretion of pro-inflammatory and anti-inflammatory mediators. Stromal cells are imprinted with tissue-specific phenotypes and contribute to site-specific lymphocyte recruitment. During chronic inflammation, the modified pro-inflammatory microenvironment leads to changes in the stromal cells, which acquire a pathogenic phenotype. At the site of inflammation, infiltrating B cells and T cells interact with stromal cells. These interactions induce a plasma cell-like phenotype in B cells and T cells, associated with secretion of immunoglobulins and inflammatory cytokines, respectively. B cells and T cells also influence the stromal cells, inducing cell proliferation, molecular changes and cytokine production. This positive feedback loop contributes to disease chronicity. This Review describes the importance of these cell interactions in chronic inflammation, with a focus on human disease, using three selected autoimmune and inflammatory diseases: rheumatoid arthritis, psoriatic arthritis (and psoriasis) and systemic lupus erythematosus. Understanding the importance and disease specificity of these interactions could provide new therapeutic options.

Promoter Methylation Leads to Decreased ZFP36 Expression and Deregulated NLRP3 Inflammasome Activation in Psoriatic Fibroblasts

The mRNA-destabilizing protein tristetraprolin (TTP), encoded by the ZFP36 gene, is known to be able to end inflammatory responses by directly targeting and destabilizing mRNAs encoding pro-inflammatory cytokines. We analyzed its role in psoriasis, a disease characterized by chronic inflammation. We observed that TTP is downregulated in fibroblasts deriving from psoriasis patients compared to those deriving from healthy individuals and that psoriatic fibroblasts exhibit abnormal inflammasome activity compared to their physiological counterpart. This phenomenon depends on TTP downregulation. In fact, following restoration, TTP is capable of directly targeting for degradation NLRP3 mRNA, thereby drastically decreasing inflammasome activation. Moreover, we provide evidence that ZFP36 undergoes methylation in psoriasis, by virtue of the presence of long stretches of CpG dinucleotides both in the promoter and the coding region. Besides confirming that a perturbation of TTP expression might underlie the pathogenesis of psoriasis, we suggest that deregulated inflammasome activity might play a role in the disease alongside deregulated cytokine expression.

Interleukin-17 Drives Interstitial Entrapment of Tissue Lipoproteins in Experimental Psoriasis

Lipoproteins trapped in arteries drive atherosclerosis. Extravascular low-density lipoprotein undergoes receptor uptake, whereas high-density lipoprotein (HDL) interacts with cells to acquire cholesterol and then recirculates to plasma. We developed photoactivatable apoA-I to understand how HDL passage through tissue is regulated. We focused on skin and arteries of healthy mice versus those with psoriasis, which carries cardiovascular risk in man. Our findings suggest that psoriasis-affected skin lesions program interleukin-17-producing T cells in draining lymph nodes to home to distal skin and later to arteries. There, these cells mediate thickening of the collagenous matrix, such that larger molecules including lipoproteins become entrapped. HDL transit was rescued by depleting CD4⁺ T cells, neutralizing interleukin-17, or inhibiting lysyl oxidase that crosslinks collagen. Experimental psoriasis also increased vascular stiffness and atherosclerosis via this common pathway. Thus, interleukin-17 can reduce lipoprotein trafficking and increase vascular stiffness by, at least in part, remodeling collagen.

Defined System to Assess the in Vitro Induction of a Psoriasis Phenotype on Normal Keratinocytes by Fibroblasts from Psoriatic Subjects

Background:

Research has shown that involved as well as uninvolved skin of psoriatic subjects have an inherent defect that manifests, at a minimum, as nonapparent epidermal hyperplasia. Fibroblasts have been shown to regulate epidermal proliferation and differentiation; furthermore, fibroblasts from patients with psoriasis have altered growth, response, and mediator release when compared with normal.

Objective:

We conjectured that it might be possible to generate the enhanced epidermal proliferation inherent to psoriatic skin in vitro using a defined interactive culture system with cellular components from the skin of normal and psoriatic subjects.

Methods:

To reduce the variables whereby fibroblasts stimulate keratinocyte proliferation in vitro, a system was developed that does not permit direct contact between keratinocytes and fibroblasts, but does permit the exchange of media and mediators as well as an assessment of keratinocyte growth as a function of time. Fibroblasts from involved and uninvolved sites from biopsies of seven untreated psoriatic subjects were assessed for their effect on the growth of keratinocytes from normal subjects.

Results:

Analysis shows that five of seven fibroblast sources from involved sites and six of seven from uninvolved sites of psoriatic subjects induce normal keratinocytes to display enhanced outgrowth. Three of 14 fibroblast sources consistently do not induce this change. Fibroblasts from uninvolved sources are particularly effective, with a mean of 40 ± 8% (SD) more growth than with normal fibroblasts.

Conclusion:

It is concluded that fibroblasts from psoriatics can induce the phenotype of increased epidermal proliferation on normal keratinocytes via a soluble mediator in a defined system.

Experimental models for psoriasis

Evidence suggests that inherent in skin of psoriatic subjects are cells, architectural structures, and/or mediators, which are, at a minimum, responsible for its hyperproliferative epidermis. An objective of our laboratory has been to establish an in vitro definition of this inherent aberration. Fibroblasts are important to epidermal proliferation/differentiation. This, and an unconfirmed report that fibroblasts from psoriatic subjects might drive the abnormal epidermal proliferation in psoriasis, have caused further focus on the fibroblast. Data show that fibroblasts from patients with psoriasis, both involved and uninvolved, in the presence of human serum, either normal or psoriatic, have an increased rate of proliferation. Fibroblasts from uninvolved psoriatic sites are most responsive. To determine if fibroblasts from psoriatics could induce the psoriasiform phenotype on normal keratinocytes, an interactive skin equivalent system has been developed. With this system, fibroblasts from uninvolved and involved sites cause normal keratinocytes to have an enhanced outgrowth. Uninvolved fibroblasts cause the greatest changes. The nature of the skin equivalent system calls for this to occur via message over distance. We conclude that fibroblasts from psoriatic subjects can induce a psoriasiform phenotype via a soluble message.

The evolution of the psoriatic lesion

Psoriasis comprises a host of abnormalities, and various aspects of the pathogenesis of psoriasis have been suggested to be of primary relevance. The aim of this review is to identity driving factors in the pathogenesis of psoriasis and to explore the dynamics of processes eventually resulting in a psoriatic lesion. In this review observations on the evolution from the symptomless skin to lesional skin in patients with psoriasis will be integrated with observations in various animal models of psoriasis.

Vitamin D3 inhibits proliferation and increases c-myc expression in fibroblasts from psoriatic patients

Fibroblast cultures were established from the skin of normal and psoriatic subjects. The response to 1 alpha,25-dihydroxyvitamin D3 [1,25-(OH)2D3] of each kind of cells was assessed by measuring tritiated thymidine incorporation into DNA as an index of cell proliferation. We found that both types of cells responded with a similar dose- and time-dependent inhibition of thymidine incorporation. We also studied the response of the mRNA encoding the proto-oncogene c-myc, since its level is associated to the proliferative state in many cell types. Psoriatic fibroblasts contained higher basal amounts of c-myc RNA than control fibroblasts. Addition of 1,25-(OH)2D3 to the culture medium induced a time-dependent increase of c-myc RNA in psoriatic fibroblasts but not in controls. As a control, retinoic acid had no effect in any of the two cell types. It is concluded that in primary normal human fibroblasts, c-myc RNA levels are not correlated with the proliferative state, and that there is an altered expression of this proto-oncogene in psoriasis.

Effects of Serum from Normal and Psoriatic Subjects on the Proliferation of Fibroblasts from Involved and Uninvolved Skin of Psoriatic Patients

Background:

A framework hypothesis for the pathogenesis of psoriasis states that “there is an aberration throughout the skin of patients with psoriasis that is modified to disease expression by circulating factors.”

Objective:

A question to emerge from this hypothesis concerns whether fibroblasts could be more central to the aberration than other cells of the skin? This article focuses on the modulation of growth of fibroblasts from uninvolved and involved sites of patients with psoriasis as a function of the type of serum in which they are grown.

Methods:

Fibroblasts were generated from normal subjects and from involved and uninvolved sites of six untreated psoriatic subjects and their growth in vitro was assessed as a function of the type of serum (fetal bovine serum, normal human serum, and serum from psoriatic subjects) in which they are grown.

Results:

The data show (a) that fibroblasts from psoriatic subjects, especially from uninvolved sites, have an inherent capacity to proliferate at an enhanced rate relative to normal fibroblasts; (b) that this enhanced proliferation can be augmented by normal human serum and to a greater degree by serum from psoriatic subjects; (c) that ≈ 40% of the enhanced proliferation is secondary to the psoriasis serum phenotype; (d) that ≈ 30% of enhanced proliferation is secondary to the psoriasis fibroblast phenotype; and (e) that the magnitude of these features are independent of the severity of psoriasis, as assessed at the time of donation of biopsies for generation of test fibroblasts or of blood for serum.

Conclusion:

These data support the hypothesis that there is an aberration throughout the skin of patients with psoriasis (enhanced proliferation of fibroblasts in vitro, especially from uninvolved sites) that is modified by circulating factors (serum).

Increased collagen synthesis in psoriasis in vivo

Psoriasis is an inflammatory skin disease of unknown a etiology which also involves changes in dermal elements. Previous in vitro studies have shown an increased collagen synthesis rate in cultured fibroblasts. In this study collagen synthesis was studied in vivo in the uninvolved skin of psoriatic patients using a newly developed method in which collagen propeptides were measured in suction blister fluid. Both type I and type III collagen synthesis rates, as measured in terms of the carboxyterminal propeptide of type I procollagen (PICP) and the aminoterminal propeptide of type III procollagen (PIIINP), were increased about two-fold in uninvolved psoriatic skin as compared with controls, the mean level of PICP being 870 and 457 micrograms, respectively (P < 0.001), and of PIIINP being 294 and 124 micrograms, respectively (P < 0.01). The increased collagen synthesis rate was also confirmed by in situ hybridization using specific probes. Collagen mRNAs were found to be particularly abundant in psoriatic patients, who also demonstrated a high collagen synthesis rate when assayed by measuring collagen propeptides. The increased rate of collagen synthesis in the uninvolved psoriatic skin seemed not to be related to the severity of the disease or to various treatments such as UVB, PUVA, retinoids or cytostatic drugs, but seemed more likely to be due to the psoriasis itself. Interestingly, skin thickness was not increased in the patients with psoriasis, even though collagen synthesis was markedly elevated, perhaps suggesting that in psoriasis the turnover rate of collagen is enhanced.

Studies and perspectives of signal transduction in the skin

Tumor-promoting phorbol ester and epidermal growth factor (EGF) exert marked influences on the proliferation and differentiation of keratinocytes. These two agents bring their physiological functions into play via protein kinase C (PKC) activation (and/or down regulation) and protein tyrosine kinase, respectively. In this paper, the present situation in the studies on the signal transduction of keratinocytes centering around these two kinases is discussed. An outline of studies on signal transduction of cells other than keratinocytes in the skin is also given.

Human dermal fibroblast interleukin-1 receptor antagonist (IL-1ra) and interleukin-1 beta (IL-1 beta) mRNA and protein are co-stimulated by phorbol ester: implication for a homeostatic mechanism

Although the major functions of fibroblasts are to produce extracellular matrix and to maintain a structural framework for organ systems, recent studies have demonstrated that fibroblasts are active participants in inflammatory processes by synthesizing various inflammatory mediators. In this report, we provide evidence that fibroblasts may contribute to the regulation of inflammation by the synthesis of both the intracellular form and the secretory form of interleukin-1 receptor antagonists in conjunction with interleukin-1 beta production. Indirect immunofluorescence microscopy localized interleukin-1 receptor antagonist and interleukin-1 beta proteins primarily in the fibroblast cytoplasm. Polymerase chain reaction amplification of reverse-transcribed mRNA with primers specific for the intracellular form of interleukin-1 receptor antagonist detected cDNA fragments present in both unstimulated and phorbol ester-stimulated fibroblasts, identical in molecular size to that in unstimulated keratinocytes. Amplification with primers specific for the secretory form of interleukin-1 receptor antagonist, however, detected cDNA fragments in phorbol ester-stimulated fibroblasts and phytohemagglutinin-stimulated peripheral mononuclear cells, but not in unstimulated fibroblasts or keratinocytes. The amplified fibroblast cDNA sequences for both intracellular and secretory interleukin-1 receptor antagonists were confirmed by digestion with three restriction endonucleases. By ethidium bromide visualization of amplified cDNA derived from serially diluted total cellular RNA and by Southern blot hybridization analysis of amplified cDNA, we have demonstrated that fibroblast interleukin-1 receptor antagonist mRNA and interleukin-1 beta mRNA were co-stimulated by phorbol ester. Similarly, ELISA demonstrated that fibroblast cytoplasmic interleukin-1 receptor antagonist protein and interleukin-1 beta protein were co-stimulated by phorbol ester. Our data suggests that the intracellular form of interleukin-1 receptor antagonist may be important in maintaining physiologic homeostasis in fibroblasts during interleukin-1 beta induction and release.

Protein kinase C activity in normal and psoriatic cells: cultures of fibroblasts and lymphocytes

Protein kinase C (PKC) activity was measured in cultures of fibroblasts from biopsies of the involved and uninvolved skin of seven patients with psoriasis and from the skin biopsies of nine normal controls. PKC activity was significantly increased (P less than 0.005) in the particulate fraction of fibroblasts obtained from the involved areas of skin (450 +/- SEM 89 pmol/mg protein/3 min) and the uninvolved skin (394 +/- 94 pmol/mg protein/3 min) in psoriasis as compared to that of controls (103 +/- 24 pmol/mg protein/3 min). The soluble fraction of PKC activity was comparable in controls and in the fibroblasts obtained from involved areas and not significantly different from the values in fibroblasts from uninvolved skin. PKC activity was also measured in the soluble and particulate fractions of lymphocytes from 13 patients with psoriasis and from 14 normal controls. The PKC activity did not differ in the lymphocytes of patients with psoriasis from the controls in either the cytosolic or the membrane fractions. The increase in PKC activity as expressed at the membrane level of psoriatic fibroblasts may be related to an increase in sensitivity of these cells to hormones or growth factors involved in the regulation of their growth.

The mitogenic effects of sera from psoriatic subjects on normal dermal fibroblasts: an absence of correlation with the clinical activity of psoriasis

Serum was obtained from 21 normal and 22 psoriatic subjects, and the severity of skin disease in the psoriatic patients was recorded using the PASI score. The scores ranged from 1.8 to 51.0. The growth stimulatory effect of the sera on normal dermal fibroblasts in cell culture was assessed by measuring [3H]-thymidine uptake. Each serum was assessed at four concentrations (2,5, 10,20%). The psoriatic sera were more growth stimulatory than normal sera, but this difference was statistically significant (P less than 0.02) only at 20% serum concentration. Eleven of the 22 psoriatic serum samples had a mitogenic effect greater than the mean +/- SEM of all the normal sera; these sera were then from patients with PASI scores of 4.5-51.0. Six of these psoriatic subjects were recalled after 5 months; their PASI scores were reassessed, and the mitogenic effect of new serum samples was compared with that of the initial samples. All of these patients displayed a change in serum mitogenic effect, but this was not consistent with the change in severity of skin disease over the corresponding time period. In one subject, the severity of the psoriasis had increased marginally over the 5 months, while the mitogenic effect of her serum decreased significantly (mean counts of 43808 vs. 32660; P = 0.0029).

Glycosaminoglycans production by cultured skin fibroblasts from the Pasini and Cockayne-Touraine forms of dominant dystrophic epidermolysis bullosa

Qualitative and quantitative comparisons of glycosaminoglycans e (GAG) production were made on fibroblast lines cultured from the skin of six patients with the Pasini (albopapuloid) form of dominant dystrophic epidermolysis bullosa, six with the non-albopapuloid form (Cockayne-Touraine), eight lines from patients with simplex or recessive dystrophic epidermolysis bullosa and eight lines from normal individuals. A reasonable match of donor age and gender, site, and passage number was achieved. Contrary to an earlier report, the lines from the Pasini group were unexceptional in the amount of GAG they secreted and the proportions of sulfated and nonsulfated GAG showed no consistent difference from the Cockayne-Touraine or control lines. The Pasini lines secreted 77 +/- 18 (SEM) microgram GAG-uronic acid per 10(7) cells and the Cockayne-Touraine lines 81 +/- 12 micrograms at equivalent cells densities. Sulfated GAG represented averages of 19 +/- 4+ in Pasini lines, 17 +/- 5% in Cockayne-Touraine, and 14 +/- 3% in controls. These findings are consistent with current views of albopapuloid lesions as an unreliable clinical sign in epidermolysis bullosa and bring into question the validity of the Pasini entity.

Alteration of cartilagenous proteoglycan in psoriasis

Articular tissue was obtained at surgery for a femoral neck fracture in a patient with psoriasis without arthritis. The proteoglycan of the cartilage of the sample was analysed biochemically. Normal cartilage is known to produce two types of proteoglycan monomers (fast- and slow-sedimenting groups), which are distinguishable by density-gradient ultracentrifugation. In the psoriatic cartilage analysed in the present study, it was shown that the former group was absent and only the latter group remained.

Inhibition of psoriatic cell proliferation in in vitro skin models by amiprilose hydrochloride

Amiprilose hydrochloride, a 3-substituted glucose derivative, was found to inhibit the proliferation of human fibroblasts and keratinocytes originating from psoriatic lesions. Fibroblasts and keratinocytes were obtained from skin biopsies of normal donors, and from the biopsies of active/involved and uninvolved sites of psoriatic donors. The cells were cultured as monolayers or as components of tissue equivalent models. Keratinocytes and fibroblasts originating from biopsies of psoriatically involved areas were shown to proliferate at a significantly higher rate than those derived from uninvolved areas. The antiproliferative effect of amiprilose hydrochloride was not observed with normal keratinocytes or fibroblasts from the skin of healthy donors or from uninvolved areas of psoriatic donors. Amiprilose hydrochloride was not cytotoxic to any of these cells at levels below 0.1%. The combination of the low cytotoxicity and the selective antiproliferative effect indicates that this compound may be a useful antipsoriatic agent. The use of monolayer cultures and tissue equivalent models in this study illustrates the utility of such a progressive strategy in the evaluation of potential topical pharmaceuticals.

Fibroblast-keratinocyte interactions in psoriasis: failure of psoriatic fibroblasts to stimulate keratinocyte proliferation in vitro

We have tested in two ways the hypothesis that dermal fibroblasts direct the hyperproliferation of the overlying epidermis in psoriasis. First, culture medium from psoriatic and from normal skin fibroblasts was added to monolayer cultures of foreskin keratinocytes. Second, psoriatic and normal fibroblasts embedded in hydrated collagen lattices were co-cultured with monolayers of foreskin keratinocytes. There was no evidence in either study that psoriatic fibroblast products could stimulate the proliferation of the keratinocytes, or that normal fibroblast products inhibited their proliferation. A positive control for the fibroblasts was provided by leucocyte supernatants, which stimulated keratinocyte proliferation by up to 65%. Our data do not support a primary role for dermal fibroblasts in psoriasis.

Beta-adrenergic stimulation of cyclic AMP is defective in cultured dermal fibroblasts of psoriatic subjects

Epidermal cells from psoriatic lesions demonstrate a very low cAMP response to beta-adrenergic stimuli. We have shown that a similar abnormality occurs in dermal fibroblasts from affected areas of skin. The cells, after 5-12 passages in tissue culture, had a much reduced response to 10(-8) M and 10(-6) M isoproterenol when compared with fibroblasts from control subjects. The abnormality was not abolished by the addition of the phosphodiesterase inhibitor, 3-isobutyl-I-methylxanthine. Other putative agonists tested were vasoactive intestinal peptide and peptide histidine methionine. Neither of these had an effect on dermal fibroblasts from either normal controls or from lesions of psoriasis.

Biochemical consequences of mechanical forces generated by distention and distortion

This review includes a number of concepts: (1) mechanical forces are transmitted to cell membranes by adhesion complexes between solid elements in the extracellular environment and the cytoskeleton; (2) the adhesion complexes require inhibition of proteases to maintain their adhesion; and (3) hydrostatic pressure is a mechanical stress on solid elements in the tissues, and it is controlled by the microcirculation and lymphatic system. Hypotheses include the following: (1) mechanical forces act on the cell membrane and induce inhibitors of proteases, thereby maintaining the adhesion complexes; (2) the transduction of chemical signals--protease inhibition--is more flexible in young cells, wounds, and psoriasis. In old tissues, protease inhibition is more sustained; and (3) cell shape, cell migration, and mitosis are in part controlled by such mechanisms. These hypotheses are supported by evidence from the literature and observations from my experience and that of many co-workers in the fields of microcirculation, lymphatic systems, angiogenesis, wound healing, and proteases.

Prolyl hydroxylase and procollagen III peptide levels in the sera from patients with collagen diseases and psoriasis

Prolyl hydroxylase (PH) and procollagen III peptide (PIIIP) levels in 43 serum samples from various collagen diseases including 19 progressive systemic sclerosis (PSS) cases were simultaneously assayed and compared to those of 22 age-matched psoriasis patients and 20 healthy controls in order to examine whether they can serve as useful parameters of fibrotic changes, especially in the skin. Serum PH levels were determined with enzyme immunoassay and serum PIIIP levels with radioimmunoassay. The average values of PH were 109% (n = 3, (p less than 0.001; generalized morphea, GM), 104% (n = 1; overlap syndrome, OS), 57% (n = 6; mixed connective tissue disease, MCTD), 48% (p less than 0.05; PSS), 33% (n = 5; dermatomyositis, DM), 28% (psoriasis), and 9% (n = 9; systemic lupus erythematosus, SLE), higher than the control levels, while those of PIIIP were 82% (OS), 57% (MCTD), 42% (p less than 0.01; PSS), 11% (GM), and 5% (DM) higher and 22% (psoriasis) and 28% (SLE), lower than the controls. These results indicate that both values were higher in the diseases with skin fibrosis and lower in those without it, suggesting that both assays generally reflect the state of actual progression of fibrosis at the point of determination. These two values had considerable correlation; however, GM, psoriasis and SLE patients had relatively higher values of PH than of PIIIP. This result suggests that the PH assay may also reflect the state of connective tissue activation; therefore the PIIIP assay may be more specific for pathological fibrotic process.(ABSTRACT TRUNCATED AT 250 WORDS)

Increased phosphorylation of two 48 kDa nuclear proteins in fibroblasts derived from psoriatic patients

Psoriasis is a hereditary disease primarily affecting the skin and characterized by an abnormally high proliferation rate of the epidermal cells. Based on some recent reports indicating that the dermal compartment of the skin is involved in the hyperproliferative process, too, we investigated the nuclear protein pattern of human skin fibroblasts in cell cultures obtained from skin biopsy specimens of normal volunteers and from involved and healthy skin of untreated psoriatic patients. To eludicate the extent of phosphorylation of these proteins which occurs as a cell cycle-specific event, we performed in vitro phosphorylation of the 5 M ureasoluble nuclear proteins after serum stimulation of starved fibroblasts. Without exogeneous kinase in the assay the phosphorylation of several acidic proteins was detected. Two of them with a pI of 3.5 and a molecular mass near 48 kDa seem to be enhanced in synthesis and modification in the psoriatic fibroblasts indicating a specific function particularly in these cells.

Increased chemotactic and mitogenic response of psoriatic fibroblasts to platelet-derived growth factor

The effect of increasing doses from 1.25 to 10 ng/ml of PDGF was tested for chemotactic and mitogenic activity on psoriatic fibroblasts cultured from involved and uninvolved skin of five patients compared to normal fibroblasts from five matched control subjects. The chemotactic response of psoriatic fibroblasts from involved skin (p less than 0.05) and uninvolved skin (p less than 0.005) is significantly enhanced compared to normal fibroblasts. Similarly, PDGF in the presence of platelet poor human plasma is a more potent mitogenic agent in psoriatic fibroblasts than in normal fibroblasts. This increased sensitivity of psoriatic fibroblasts to PDGF may be related to the inflammatory and vascularization processes involved in psoriatic dermis.

Contraction of collagen lattices by skin fibroblasts: drug-induced changes

A range of dermatologically useful drugs were added to human skin fibroblasts cultured in collagen lattices to assess possible effects on the rate of lattice contraction. Vitamin C, Vitamin E, phenytoin, sodium salicylate, D-penicillamine and dibutyryl c-AMP had no significant effect. Chlorhexidine acetate at 10 micrograms/ml arrested contraction after 24 h but this was related to its cytotoxicity. The antibiotics griseofulvin (2-16 micrograms/ml) and cycloheximide (5-30 micrograms/ml) caused dose-related inhibitions of contraction without affecting fibroblast viability. Four corticosteroids at 10 micrograms/ml inhibited contraction, clobetasol propionate having the greatest effect. On the other hand 4 retinoids at 10(-5) M enhanced contraction by up to 20%. As lattice contraction appears to model the contraction of skin wounds and there are broad parallels between the effects shown here of antiseptics, corticosteroids and the retinoids, and their reported influence on healing wounds, the lattice system may be a useful pharmacological screen for new compounds.

Increased protein kinase C activity in fibroblast membranes from psoriatic patients

The activity of phospholipid/Ca2+-dependent protein kinase (PKc) was measured in the membrane and cytosolic fractions of normal and psoriatic human fibroblasts. The psoriatic fibroblasts displayed higher membrane-associated PKc activity than normal cells. In contrast, no significant difference in PKc activities was observed in cytosolic fractions from normal and psoriatic fibroblasts. These data suggest that PKc is preferentially associated with the membrane in psoriatic fibroblasts and that such elevated PKc activity in membranes may play a role in the pathogenesis of this disease.

Urinary excretion of glycosaminoglycans in psoriasis

Urine from patients with generalised plaque psoriasis contained substantially more precipitable glycosaminoglycans (GAG) and uronic acid than the urine of healthy controls. The difference was not related to sex, age, renal function, the hospital environment, or to the presence of arthritis. Successful topical treatment with tar or dithranol, or PUVA therapy, did not affect the rate of GAG excretion. Cellulose acetate electrophoresis of the GAG from patients and controls showed similar patterns dominated by chondroitin sulphate. There was no evidence to favour the skin lesions as the source of the additional glycosaminoglycans and the findings are consistent with the concept of psoriasis as a general disease.

Proliferation and glycosaminoglycans secretion in fibroblasts from psoriatic skin: differential responses to retinoids

The effects of four retinoids, all-trans-retinoic acid (tretinoin), 13-cis-retinoic acid (isotretinoin), R0 10-1670 (etretin) and the arotinoid, R0 15-0778, on fibroblast proliferation and glycosaminoglycans (GAG) secretion in vitro were studied. Fibroblasts lines cultured from normal skin (HSF) were compared with those from lesional (PSA) and non-lesional (PSB) psoriatic skin. In general, the retinoids inhibited proliferation; the action was cytostatic, in rank order tretinoin greater than isotretinoin greater than etretin greater than arotinoid. The psoriatic cells tended to be more sensitive than the HSF lines, overall mean proliferation values (+/- SEM), as a percentage of untreated controls being: HSF 72 ++- 3, PSA 61 +/- 3 and PSB 54 +/- 3. Stimulation of GAG secretion at low concentrations (10(-7) M) of all four retinoids, declined as concentrations increased, and secretion was inhibited at 10(-4)M in PSB fibroblasts. Calculation of effects on GAG secretion due to changes in cell density confirmed the rank order for direct stimulation of secretion as arotinoid greater than etretin greater than isotretinoin greater than tretinoin. Electrophoresis of [3H]-labelled glycosaminoglycans secreted in the presence of 10(-7) M arotinoid showed that it was predominantly hyaluronic acid, as in untreated cells. These data confirm that different retinoids have contrasting levels of effects on mesenchymal cells and suggest a greater sensitivity to drugs in fibroblasts from psoriatic skin.

High levels of hyaluronate in suction blister fluid from active psoriatic lesions

Hyaluronate concentrations were measured in suction blister fluid from blisters raised on the abdominal skin of 12 healthy control subjects, on unaffected skin of 14 patients with psoriasis, and on lesional skin from 12 of these patients. The concentrations of hyaluronate in blister fluid from the controls and from the uninvolved skin of patients with psoriasis were within the same range (2.9-10.5 and 2.4-7.8 mg/l, respectively). Six of the patients had active, widespread, untreated psoriasis and in these cases the hyaluronate concentration in blister fluid from lesional skin was greatly increased (24-30 mg/l). Patients with stable or regressing psoriasis had no significant increase in hyaluronate levels in the blister fluid from lesional skin compared with the controls (range 4.6-12.4 mg/l). Patients with active psoriasis had significantly higher serum hyaluronate concentrations than the controls and those with inactive psoriasis.

Contraction of collagen lattices by skin fibroblasts from dystrophic recessive epidermolysis bullosa and other dermatoses

Skin fibroblasts incorporated into a lattice of hydrated collagen contract it to form a tissue-like structure. Fibroblasts from patients with skin diseases, including psoriasis, epidermolysis bullosa, and scleroderma, and from control subjects, all showed a similar ability to contract the lattice. The established skin epithelial cell line NCTC 2544, melanoma cells, and 3T6 mouse fibroblasts produced little contraction. Contraction required the presence of serum and was unaffected by the addition of fibronectin (10-20 micrograms/ml). Hyaluronic acid at 50-500 micrograms/ml had no effect, but contraction was inhibited at 1 mg/ml.

Cultured psoriatic fibroblasts from involved and uninvolved sites have a partial but not absolute resistance to the proliferation-inhibition activity of 1,25-dihydroxyvitamin D3

We examined the responsiveness of cultured dermal fibroblasts from biopsies of uninvolved and involved areas of skin from six patients with psoriasis to the cell-proliferation-inhibition activity of 1,25-dihydroxyvitamin D3 (1,25-(OH)2-D3). Cultured fibroblasts from age-matched controls responded to 1,25-(OH)2-D3 (at 0.01, 1, 10, and 100 microM) in a dose-dependent fashion, whereas cultured psoriatic fibroblasts from involved or uninvolved skin showed no inhibition of proliferation when exposed to 0.01 or 1 microM of 1,25-(OH)2-D3. However, 1,25-(OH)2-D3 did inhibit proliferation of cultured psoriatic fibroblasts when the concentrations were increased to 10 and 100 microM. An analysis of the 1,25-(OH)2-D3 receptors in cultured psoriatic fibroblasts from uninvolved skin revealed that the Kd, nmax, and sedimentation coefficient were identical to the receptors found in the fibroblasts from age-matched controls. Therefore, cultured psoriatic fibroblasts from involved and uninvolved skin have a partial resistance to 1,25-(OH)2-D3, suggesting that there may be a biochemical defect that is inherent in the dermal fibroblasts of psoriatic patients. Recognition of this defect may provide a new approach for the evaluation of the cause and treatment of this disfiguring skin disorder.

Circulating hyaluronate in psoriasis

A radioassay method allowing measurements of low concentrations of circulating hyaluronate was used in a study of serum hyaluronate concentrations in 44 patients with psoriasis. Twenty-three of them had only skin lesions and 21 had both skin lesions and arthropathy. In both of these groups significantly elevated serum levels of hyaluronate were found. The highest values were observed in those with widespread and active skin disease and/or active arthritis. Serum hyaluronate positively correlated with the plasma concentrations of alpha 1-antitrypsin and haptoglobin and also with ESR, which may indicate a relationship between acute inflammation and increased production of hyaluronate. Seven patients with widespread atopic dermatitis included for comparison had normal hyaluronate values. In blister fluid from lesional skin in two patients with acute psoriasis, very high concentrations of hyaluronate were found, in comparison with the concentrations in blister fluid from non-involved skin. The increased concentration of serum hyaluronate in psoriasis indicates involvement of dermal and synovial tissue in psoriasis, in addition to the epidermal changes.

Mitogenic effects of sera from normal and psoriatic subjects on human skin fibroblasts

Sera from normal and psoriatic subjects had similar mitogenic effects when added to monolayer cultures of human skin fibroblasts. Fibroblasts derived from a psoriasis patient proliferated faster in both types of sera than fibroblasts from a normal subject, despite similar rates of proliferation in foetal calf serum. The psoriatic fibroblasts appeared to be inherently capable of a greater response to human serum mitogens than the normal fibroblasts.

Junctional epidermolysis bullosa in two siblings: clinical observations, collagen studies and electron microscopy

Two siblings with junctional epidermolysis bullosa are described: both survived beyond parturition. They were treated with the usual therapeutic doses of phenytoin, dapsone, prednisolone, and zinc supplements without effect. Investigation of the skin of one of the patients showed that his fibroblasts, collagen synthesis and collagenase levels were normal. In view of the normality of the collagenase levels, it is probably not surprising that phenytoin was ineffective. Electron microscopy demonstrated junctional cleavage without pathology in the dermis itself: abnormal hemidesmosomes were seen as described previously, though it is suggested that this is not the primary abnormality which results in the disease process.

Hyperactivity of fibroblasts cultured from psoriatic skin: II. Synthesis of macromolecules

Glycosaminoglycans and protein synthesis were assessed in fibroblasts cultured from the involved (PSA strains) and uninvolved (PSB strains) forearm skin of patients with severe generalized psoriasis and compared with that in fibroblasts from the forearm skin of control subjects of similar ages (NSF strains). Average rates of glycosaminoglycan secretion were 19% (PSA) and 28% higher (PSB) in psoriatic strains. Although these differences were not significant in themselves, the relationship between glycosaminoglycan secretion and fibroblast density (cells/cm2) was significantly different (P = 0.02) for the psoriatic and control groups, with the psoriatic cells secreting appreciably more glycosaminoglycans at higher cell densities. The nature of the glycosaminoglycans produced was the same in psoriatic and normal strains; 90% was recovered in the culture medium and the bulk of this appeared to be hyaluronic acid with only small amounts of sulphated components. Collagen synthesis was 77% higher in PSA and PSB strains (P less than 0.01), while other protein synthesis was increased by 44% (P less than 0.05). These findings confirm that fibroblasts from psoriatic skin are hyperactive in vitro. The data are compatible with the results of studies of psoriatic skin in vivo and suggest that the entire skin is abnormal.