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

The Growth Factor Release from a Platelet-Rich Plasma Preparation Is Influenced by the Onset of Guttate Psoriasis: A Case Report

The involvement of platelets in immune and inflammatory processes is generally recognized; nevertheless, in psoriasis, their role is not clearly understood. We studied the in vitro growth factor release from a platelet-rich plasma preparation, the concentrated growth factors (CGF), in a case of a psoriasis subject three days before the onset of the papule. The CGF clots were incubated in a cell culture medium without growth supplements for 5 h and 1, 3, 6, 7, and 8 days, and the release kinetics of PDGF-AB, VEGF, TNF-α, and TGF-β1 were evaluated. The data, based on the results obtained during the case study, report a general increase in growth factor release in the psoriasis subject with respect to the healthy control, indicating an imbalance of growth factor production from blood cells. Although the results should be validated in the future, they show new aspects of this dermatological pathology, opening new possibilities both as the method of study, using CGF, and the involvement of platelets and growth factors in its development and maintenance.

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.

Effects of pdgf-bb on rat dermal fibroblast behavior in mechanically stressed and unstressed collagen and fibrin gels

The dose-response effects of platelet-derived growth factor BB (PDGF-BB) on rat dermal fibroblast (RDF) behavior in mechanically stressed and unstressed type I collagen and fibrin were investigated using quantitative assays developed in our laboratory. In chemotaxis experiments, RDFs responded optimally (P < 0.05) to a gradient of 10 ng/ml PDGF-BB in both collagen and fibrin. In separate experiments, the migration of RDFs and the traction exerted by RDFs in the presence of PDGF-BB (0, 0.1, 1, 10, or 100 ng/ml) were assessed simultaneously in the presence or absence of stress. RDF migration increased significantly (P < 0.05) at doses of 10 and 100 ng/ml PDGF-BB in collagen and fibrin in the presence and absence of stress. In contrast, the effects of PDGF-BB on RDF traction depended on the gel type and stress state. PDGF-BB decreased fibroblast traction in stressed collagen, but increased traction in unstressed collagen (P < 0.05). No statistical conclusion could be inferred for stressed fibrin, but increasing PDGF-BB decreased traction in unstressed fibrin (P < 0.05). These results demonstrate the complex response of fibroblasts to environmental cues and suggest that mechanical resistance to compaction may be a crucial element in dictating fibroblast behavior.

MAP kinase abnormalities in hyperproliferative cultured fibroblasts from psoriatic skin

Several studies indicate that dermal fibroblasts have a specific role in the pathophysiology of psoriasis. We have previously found that cultured fibroblasts from psoriatic patients are hyperproliferative and have low cyclic AMP-dependent protein kinase activity. In this study, we observed that these cells are also larger than normal. Given the key role of mitogen-activated protein kinases (MAPK) in the regulation of cell proliferation and cytoskeleton function, we characterized MAPK in psoriatic fibroblasts and in normal fibroblasts. Serum and platelet-derived growth factor treatment of serum-deprived fibroblasts led to a larger increase in MAPK activity in psoriatic cells than in normal cells. We then purified MAPK by ion-exchange chromatography. MAPK activity was again found to be significantly higher in psoriatic fibroblasts than in normal cells, both when deprived of serum (p < 0.01) and when stimulated with serum (p < 0.05). Interestingly, 8-bromo-cAMP treatment inhibited serum-stimulated MAPK phosphorylation in normal fibroblasts but had no effect in psoriatic fibroblasts. We observed a temporal variation in nuclear localization of phosphorylated MAPK in cultured fibroblasts stimulated by either serum or platelet-derived growth factor. No difference in the localization of phosphorylated MAPK in normal and psoriatic skins was found. Psoriatic fibroblasts are the first example of a MAPK pathway abnormality in large human benign hyperproliferative cells.

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).

Thrombin may contribute to the pathophysiology of central nervous system injury

Thrombin has multiple functions, including its function as a key enzyme during blood coagulation and other physiologic activities. We studied brain tissue reactions to thrombin that might be present in the central nervous system (CNS) following injury. Thrombin and three different types of controls--buffer, albumin, and plasmin--were individually infused into the rat caudate nucleus by a continuous osmotic mini-pump. Brains were examined by conventional histologic and immunohistologic techniques. Antibodies for bromodeoxyuridine (BrdU), glial fibrillary acidic protein (GFAP), vimentin, and laminin were employed to assess the infiltration of inflammatory cells, proliferation activity of cells, and reaction of astrocytes and mesenchymal cells, respectively. The number of inflammatory cells, number of BrdU-positive cells, area and number of vimentin-positive astrocytes, and the area of GFAP-positive astrocytes were quantitatively analyzed. Thrombin caused infiltration of inflammatory cells, proliferation of mesenchymal cells, induction of angiogenesis, and an increase in vimentin-positive reactive astrocytes. These histologic changes caused by thrombin infusion resembled the inflammation, scar formation, and reactive gliosis in the CNS following injury. These results suggest that thrombin may play an important role in inflammatory responses to CNS injury since thrombin is one of the blood borne factors that may interact with brain tissue after CNS injury. The data further suggest that the therapeutic application of antithrombin agents for CNS injury suppresses inflammation and the excessive gliosis and scar formation, which are barriers to neuronal regeneration.

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.

Increased dermal expression of platelet-derived growth factor receptors in growth-activated skin wounds and psoriasis

Platelet-derived growth factor (PDGF) is a potent mitogenic and chemotactic factor for fibroblasts and other cell types. PDGF effects are mediated by binding of PDGF to dimeric PDGF receptors possessing intrinsic tyrosine kinase activity. We examined the expression pattern of PDGF receptors in cryostat sections of normal and growth-activated human skin using a monoclonal antibody, PR7212, specific for the beta subunit of the PDGF receptor. PDGF receptors were expressed at low levels in normal skin, with only occasional staining of dermal connective tissue cells. In contrast, PDGF receptor expression was greatly elevated in the dermis of growth-activated skin from 15 chronic wounds and 10 psoriatic lesions. PDGF receptors were increased in dermal fibroblasts and in dermal blood vessels in both conditions. Immunoblot analysis confirmed the increased expression of beta-subtype PDGF receptors in psoriatic lesional tissue. PDGF receptors were not detected in normal or growth-activated epidermis. Differential expression of PDGF receptors could regulate increased proliferation of vascular and connective tissue cells observed in psoriasis and chronic wounds.

Effect of retinoic acid on platelet-derived growth factor (PDGF) bioactivity and type-B PDGF receptors in normal and psoriatic human fibroblasts

Psoriasis is a common skin disease in which retinoids have beneficial effects. It offers a model for the study of benign hyperproliferation with abnormal differentiation. The dermis has a prominent role in the appearance of epidermal lesions. It is therefore of interest to study the factors that modulate dermal cell proliferation. In this study, the role of retinoids in modulating platelet-derived growth factor (PDGF) bioactivity was studied in normal (six subjects) and psoriatic fibroblasts from involved and uninvolved tissues (six patients). Retinoic acid treatment (for 4 d at 10(-6) M) of psoriatic fibroblasts significantly increased the chemotactic effect of PDGF in these cells (p less than 0.01 and p less than 0.05, respectively, in involved and uninvolved skin at 20 ng/ml of platelet-derived growth factor as measured in a modified Boyden Chamber Assay). In the same way, retinoic acid treatment of psoriatic fibroblasts increased the mitogenicity of platelet-derived growth factor in these cells. Retinoic acid treatment has no significant effect on the mitogenic and chemotactic activity of PDGF in normal fibroblasts. The binding of the homodimer BB PDGF to its type-B receptor, which mediates the mitogenic and chemotactic effect of PDGF, was not modified by retinoic acid treatment either in psoriatic and/or normal fibroblasts. These results suggest that retinoic acid may modulate the PDGF bioactivity in psoriatic fibroblasts not by affecting the binding of this ligand to these cells but by influencing a post-receptor event.

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.