Normal and psoriatic keratinocytes and fibroblasts compared in culture

Human pluripotent stem cells: An alternative for 3D in vitro modelling of skin disease

To effectively study the skin and its pathology, various platforms have been used to date, with in vitro 3D skin models being considered the future gold standard. These models have generally been engineered from primary cell lines. However, their short life span leading to the use of various donors, imposes issues with genetic variation. Human pluripotent stem cell (hPSC)-technology holds great prospects as an alternative to the use of primary cell lines to study the pathophysiology of human skin diseases. This is due to their potential to generate an unlimited number of genetically identical skin models that closely mimic the complexity of in vivo human skin. During the past decade, researchers have therefore started to use human embryonic and induced pluripotent stem cells (hESC/iPSC) to derive skin resident-like cells and components. These have subsequently been used to engineer hPSC-derived 3D skin models. In this review, we focus on the advantages, recent developments, and future perspectives in using hPSCs as an alternative cell source for modelling human skin diseases in vitro.

Topical retinoic acid alters the expression of cellular retinoic acid-binding protein-I and cellular retinoic acid-binding protein-II in non-lesional but not lesional psoriatic skin

Therapeutic retinoids have profound effects on psoriatic skin pathology but their interactions with various retinoid-binding proteins in lesional vs non-lesional skin have not been investigated. Using quantitative real-time PCR the mRNA expression of cellular retinol-binding protein I (CRBPI) and retinoic acid-binding protein I/II (CRABPI/CRABPII) was studied in psoriatic and healthy control (=normal) skin after 4 days of occlusive RA/vehicle treatment (n=6). Untreated psoriatic lesions showed a markedly elevated CRABPII/CRABPI ratio, while the CRBPI level was reduced in lesional and non-lesional skin as compared to normal skin. In RA-treated normal and non-lesional skin, the mRNA expression of CRBPI was unaltered while that of CRABPI and CRABPII was reduced by approximately 80% and increased approximately 5-fold, respectively, as compared to vehicle-treated skin. In contrast, lesional skin exposed to RA showed an almost 90% increase in CRBPI transcripts but unaltered expression of CRABPI and CRABPII, yet, the mRNA expression of several inflammatory mediators, e.g. inducible nitric oxide synthase, interferon-gamma and interleukin-1beta, was clearly reduced. Immunohistochemistry localized CRABPII to suprabasal keratinocytes in normal skin and revealed markedly elevated levels in lesional skin. RA treatment induced CRABPII protein expression in normal and non-lesional skin, to similar levels as in untreated lesions. The results indicate that the effects of RA differ in normal/non-lesional psoriatic skin and lesional skin. Whether the high expression of CRABPII in psoriatic skin lesions is due to increased amounts of endogenous retinoids in lesional skin or reflects an abnormal regulation of the CRABPII gene in psoriasis remains to be studied.

Psoriasis and altered calcium metabolism: downregulated capacitative calcium influx and defective calcium-mediated cell signaling in cultured psoriatic keratinocytes

Intracellular calcium plays an important part in the regulation of proliferation and differentiation of keratinocytes. Detached from their in vivo environment, cultured psoriatic keratinocytes were investigated by monitoring free intracellular calcium concentration, which was measured using fura-2/AM as a calcium-sensitive probe. The mean increase in intracellular calcium of psoriatic keratinocytes was significantly reduced compared with control keratinocytes when intracellular calcium stores were mobilized from endoplasmic reticulum with thapsigargin. This finding suggests defective capacitative calcium influx of psoriatic cells. Intracellular calcium stores were similar in psoriatic and control keratinocytes, when extracellular calcium was chelated with ethyleneglycol-bis(beta-aminoethyl ether)-N,N,N',N',-tetraacetic acid and intracellular calcium was depleted with thapsigargin. Mechanical wounding of keratinocyte monolayer resulted in a significantly reduced rise in intracellular calcium of psoriatic cells in low (< 0.1 mM) and high (1.8 mM) extracellular calcium suggesting defective intercellular coupling of psoriatic keratinocytes. Blocking of gap-junctions with heptanol in wounded keratinocytes did not affect the intracellular calcium response in psoriatic keratinocytes in contrast to healthy keratinocytes. Adding adenosine triphosphate to culture medium resulted in a more pronounced intracellular calcium increase than thapsigargin in psoriatic keratinocytes, suggesting that inositol triphosphate-mediated, P2-purinergic signaling was enhanced in these cells. Moreover, psoriatic keratinocytes maintained their defective responses up to at least fifth passage suggesting that psoriatic keratinocytes have an inborn error in calcium metabolism, rather than a localized defect in response to altered extracellular calcium gradient observed in vivo.

Differential proliferation of endothelial cells and keratinocytes in psoriasis and spongiotic dermatitis

This study used MIB-1 monoclonal antibody to quantify the proliferating keratinocytes and endothelial cells and their proliferation fractions in cases of normal skin, acute and established plaque psoriasis, and acute and chronic spongiotic dermatitis. The number and the proliferation fraction of MIB-1 positive cells were higher in psoriatic and chronic spongiotic lesions than in normal skin (p < 0.05). Established plaque psoriasis had a higher number of proliferating keratinocytes and a higher keratinocytic proliferation fraction than did acute psoriasis (p < 0.05). The number of proliferating endothelial cells decreased as acute psoriatic lesion became chronic, but the number in acute spongiotic lesion increased as it became chronic. The endothelial proliferation fraction was higher in acute psoriasis than in established plaque psoriasis (p < 0.05). The ratio of keratinocytic proliferation fraction to endothelial cell proliferation fraction of the psoriatic and spongiotic lesions suggested the presence of different reaction patterns to inflammation in psoriasis and spongiotic dermatitis.

Keratins (K16 and K17) as markers of keratinocyte hyperproliferation in psoriasis in vivo and in vitro

Keratinocyte differentiation in psoriasis was examined using a panel of monospecific monoclonal antibodies to keratins (K), including two recently developed monoclonal antibodies raised to carboxy terminal peptides of K6 (LL020) and K16 (LL025). Keratinocytes from normal skin, untreated psoriatic plaques and non-lesional psoriatic skin, were cultured using multiple in vitro systems. Time-lapse cinephotography was used to measure the intermitotic time of normal and psoriatic keratinocytes in both low calcium-defined and serum-containing media. The intermitotic time did not differ significantly between psoriatic and normal keratinocytes. Keratin expression of psoriatic and normal keratinocytes in vitro was examined by both gel electrophoresis and immunocytochemistry. K6, K16 and K17 were detected suprabasally in all culture systems in vitro, but only in interfollicular psoriatic epidermis in vivo, and not in normal skin. Small subpopulations of keratinocytes expressed simple epithelial keratins K7, K8, K18 and K19 in cultures on plastic substrates, but these keratins were absent in skin equivalents of normal or psoriatic skin. No psoriasis-specific pattern of differentiation was found in vitro. As the K6 peptide antibody reacted with basal cells of normal skin, probably due to K5 cross-reactivity, K16 expression determined by LL025 was found to be the most sensitive indicator of the psoriatic state of differentiation, and this antibody is recommended for future work on psoriasis. K17 had a distinct pattern of tissue distribution in normal skin: K17, but not K16, was present in basal myoepithelial cells in sweat glands, and the deep outer root sheath, but K17 distribution paralleled that of K16 in suprabasal psoriatic epidermis. As keratins K6, K16 and K17 are expressed in keratinocyte hyperproliferation, when high levels of certain cytokines are also expressed, the role of growth factors and regulatory nuclear transcription factors in the control of K6, K16 and K17 expression in psoriasis requires further study, in order to provide insight into the relationship between proliferation and differentiation.

Feasibility of in vitro culturing of lesional psoriatic keratinocytes in medium containing high calcium concentrations

Lesional psoriatic keratinocyte (LPK) culture is considered to be difficult under high-Ca2+ conditions in the absence of special proliferative agents. Using a permeable collagen membrane, we obtained a culture of LPKs under high-Ca2+ conditions without any special proliferative agents. Single-cell suspensions were prepared from the epidermis of chronic psoriatic plaques. Cells were inoculated on the collagen membrane suspended slightly above the bottom of a Petri dish. We used a culture medium of Eagle's MEM containing 10% fetal calf serum. LPKs attached to the membrane 12 h after inoculation and gradually spread. They reached a confluent state by the 10th day of culture. We measured the concentrations of TGF alpha and IL-6 in the medium of LPKs, and compared these with the concentrations in normal keratinocyte (NK) cultures. Significantly increased secretion of TGF alpha by LPKs was observed during the initial phase but this secretion subsequently decreased. Concentrations of IL-6 were below the detectable level in both of NKs and LPKs throughout the observation period. Our results demonstrate that cultured LPKs under high-Ca2+ conditions secrete a larger amount of TGF alpha but not IL-6. Our cell culture system, which allows LPKs to spread and stratify, contributes to the study of the pathogenesis of psoriasis.

Cyclooxygenase activity is increased in platelets from psoriatic patients

The aim of the present study was to ascertain the relationship between in vitro hyper-aggregability and alterations in arachidonic acid metabolism in platelets from psoriatic patients. We have studied the response to several concentrations of ADP, collagen, and arachidonic acid of intact platelets from psoriatic patients and normal subjects, with and without irreversible inhibition of platelet cyclooxygenase by aspirin. Apparent kinetic constants (apparent Michaelis constant [Km] and apparent maximum velocity [Vmax]) of cyclooxygenase in platelets from both controls and psoriatic patients were also studied. The maximum percentage and slope of aggregation induced by collagen or sodium arachidonate were significantly greater (p less than 0.05) in platelets from psoriasis patients, whereas lag time was significantly shorter in the psoriasis group in response to arachidonic acid only when compared to controls. Cyclooxygenase pathway blockade inhibited the response to aggregation inducers in the following order: sodium arachidonate greater than collagen greater than ADP. When platelets were pre-treated with aspirin no significant differences were observed between controls and psoriasis patients. We also found a significant increase of the apparent Vmax value (p less than 0.05) for cyclooxygenase activity in platelets from psoriatic patients in comparison with controls. Our results indicate that platelet hyperaggregation in psoriatic patients is related to enhanced cyclooxygenase activity in their platelets.

A study of protein synthesis in cells cultured from involved psoriatic skin

Using histochemical techniques an abnormal programme of epidermal differentiation has been well documented in psoriasis. In order to characterise further the biochemistry of this process we have cultured dermal fibroblasts and epidermal keratinocytes from involved psoriatic skin. This has facilitated metabolic radiolabelling of skin cells and analysis of protein synthesis by two-dimensional polyacrylamide gel electrophoresis. The expression of keratin and differentiation markers was identical to that of normal keratinocytes, suggesting that psoriatic epidermal differentiation is not truncated in vitro as has been postulated to be the case in vivo. Low molecular mass components (5-8.5 kDa), previously shown to be upregulated in suprabasal keratinocytes, were detected in epidermal fractions from psoriatic skin enriched for basal cells. Of special interest was a component of 26 kDa, pI 5.9, which was highly upregulated in psoriatic as compared to normal cultured keratinocytes and was not detected in fibroblasts. These findings are in accord with a qualitatively abnormal pattern of differentiation for keratinocytes in the involved psoriatic epidermis.

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.

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.

Influence of culturing temperature and proteinase inhibitors on the spontaneously occurring changes in the organ culture of psoriatic skin

Skin explants from involved psoriatic lesions showed dissociation of keratinocytes, dermal-epidermal separation and degenerative changes such as cytoplasmic swelling of subcorneal prickled cells within 24 h after culture initiation at 37 degrees C in the absence of fetal bovine serum (FBS). These histological changes developed time dependently, while normal skin explants did not exhibit such phenomena. Some of the uninvolved psoriatic skin explants showed only degenerative change 48 to 72 h after culture initiation at 37 degrees C. To determine the nature of these spontaneously occurring changes in psoriatic skin explants and then to approach the pathogenesis of psoriasis, the effects of FBS, various proteinase inhibitors (PIs) and culturing temperature (37, 31, 24 degrees C) were examined in skin organ culture of normal and involved psoriatic skin. At 37 degrees C, only serine PIs (5 or 10 mg/ml of soybean trypsin inhibitor (SBTI), 1000 KIU/ml of aprotinin, or 2 mg/ml of camostat mesilate in the medium) or FBS (20% in the medium) could suppress the occurrence of dissociation of keratinocytes and dermal-epidermal separation but not the degenerative change in involved psoriatic skin explants, while other types of PIs did not exhibit any such inhibition. When the culturing temperature was reduced from 37 degrees C to 31 or 24 degrees C, the formation of dissociation of keratinocytes and dermal-epidermal separation was almost non-existent and only moderate degenerative change was observed. The addition of FBS or serine PIs to the culture at 31 degrees C revealed the formation of very weak degenerative change.(ABSTRACT TRUNCATED AT 250 WORDS)

Decreased growth inhibition by recombinant gamma interferon is associated with increased transforming growth factor-alpha production in keratinocytes cultured from psoriatic lesions

Keratinocytes from involved psoriatic plaques (PP), uninvolved, clinically symptomless skin of psoriatic patients (PN) and normal healthy skin (NN) have been cultured in a low calcium serum free system for multiple passages. In this way, the keratinocytes were removed from microenvironmental factors present in the skin. While the basal rate of proliferation of the PP, PN and NN keratinocytes was not different, the PP cells produced more transforming growth factor-alpha (TGF-alpha) than NN cells, and the antiproliferative response of PP cells to gamma interferon (IFN-gamma), a product of activated T lymphocytes, was reduced. We studied IFN-gamma because it can inhibit the proliferation of NN keratinocytes, induce their differentiation and the appearance of two immunoregulatory cell surface molecules, HLA-DR and intercellular adherence molecule-I (ICAM-I), and because in another epithelial cell system, epidermal growth factor (EGF) modulates IFN-gamma activity. The mean antiproliferative effects of IFN-gamma at 50,200, and 500 U/ml for the PP group (n = 10) was less compared to the NN group (n = 11); P less than 0.001, while the PN group (n = 5) had a less dramatic, but statistically significant, reduction in growth inhibition by IFN-gamma only at 200 and 500 U/ml compared to NN cells; P less than 0.05 and P less than 0.01, respectively. The amount of TGF-alpha produced and secreted by PP keratinocytes from five different individuals was significantly greater than by NN keratinocyte cultures. In addition, IFN-gamma induced TGF-alpha to a lesser extent in PP keratinocytes compared to NN keratinocyte cultures. Keratinocytes isolated from atopic dermatitis and Sézary syndrome patients were similar to NN keratinocytes. In contrast to its differential effects on TGF-alpha production and proliferation, IFN-gamma induced similar amounts of HLA-DR and ICAM-I on PP, PN and NN keratinocytes. Thus, for the PP keratinocytes, there was a dissociation between the antiproliferative and immunomodulatory effects of IFN-gamma. These results support our previous hypothesis that the hyperproliferation and altered differentiation of keratinocytes in psoriatic plaques is linked to an altered responsiveness of the keratinocytes to IFN-gamma. Moreover, these results provide an in vitro correlate of our in vivo observation of increased TGF-alpha levels in psoriatic plaques. A new pathophysiological model to understand psoriasis is proposed which integrates these observations involving IFN-gamma and TGF-alpha. This experimental approach also provides a system to dissect biochemical pathways of pathophysiological importance for keratinocyte hyperproliferation in psoriasis.

Post-mitotic human dermal fibroblasts efficiently support the growth of human follicular keratinocytes

For growth at low seeding densities, keratinocytes isolated from human tissues like epidermis or hair follicles are dependent on mesenchyme-derived feeder cells such as the 3T3-cell employed so far. As an alternative method, the present study describes the use of post-mitotic human dermal fibroblasts sublethally irradiated or mitomycin C-treated. Special emphasis was put on efficient growth of primary keratinocyte cultures plated at very low seeding densities. Thus, outer root sheath cells isolated from two anagen human hair follicles and plated in a 35-mm culture dish (3 - 6 X 10(2) attached cells) grew to confluence within 3 weeks (6 - 8 X 10(5) cells). Similar results were obtained for interfollicular keratinocytes. A crucial point for the function of these fibroblast feeder cells is plating at appropriate densities, considering their tremendous increase in cell size at the post-mitotic state. Plating densities of 4 - 5 X 10(3/cm2 allow full spreading of the feeder cells and do not impede the settling and expansion of the keratinocytes. Major advantages of this system include easier handling and better reproducibility than using 3T3-cells. Moreover, homologous fibroblast feeders mimic more closely the physiologic situation and therefore might provide a valuable tool for studying interactions between human mesenchymal and epithelial cells. Finally, potential hazards of using transformed feeder cells from a different species in keratinocyte cultures raised for wound covering in humans could be thus avoided.

Re-expression of disease-characteristic features of non-bullous congenital ichthyosiform erythroderma (CIE) after grafting of the pathological keratinocyte cultures to athymic mice

Epidermal keratinocytes separated from skin lesions of non-bullous congenital ichthyosiform erythroderma were investigated in an attempt at experimental reproduction of this keratinization disorder. In vitro studies on growth and differentiation of pathological keratinocytes isolated from the influence of the host's dermal and humoral components were performed using the immersed epidermal cell culture technique. Ten to 25-day-old confluent and stratified cultures were examined by means of photonic and electron microscopy, and stained with various differentiation markers for indirect immunofluorescence studies. The cultured epidermis showed low-grade differentiation and no clear-cut evenly distributed signs of the original disease. Grafting on congenitally athymic nude mice allowed further differentiation of the epidermal sheets and re-expression of the histologic and ultrastructural features of non-bullous congenital ichthyosiform erythroderma. Thus, the purely epidermal origin of this particular form of autosomal recessive ichthyosis could be confirmed. Large amounts of pathological keratinocytes generated from small skin biopsies may be used for experimental purposes after grafting on several athymic animals.

Calcium/calmodulin regulation of the proliferation of human epidermal keratinocytes, dermal fibroblasts and mouse B16 melanoma cells in culture

We have investigated the relationship between extracellular calcium, intracellular calmodulin and proliferation in normal keratinocytes. Keratinocyte proliferation and its sensitivity to calmodulin antagonists was compared with that of normal human dermal fibroblasts and neoplastic mouse B16 melanoma cells. Keratinocytes were similar to fibroblasts in showing reduced proliferation in low (0.15 mM) calcium medium and unlike B16 cells which continued to proliferate until calcium was reduced to submicromolar levels. Intracellular calmodulin was significantly higher in rapidly dividing keratinocytes in normal (1.15 mM) calcium medium than in slower dividing cells in low (0.15 mM) calcium. Fibroblasts and B16 cells maintained similar calmodulin levels in both low and normal calcium media. Calmodulin antagonists inhibited proliferation of all three cell types equally. Thus, keratinocyte calmodulin seems related to the proliferative state of the cell (unlike fibroblast calmodulin) and calmodulin antagonists may be of use in controlling the hyperproliferation of the psoriatic epidermis.

PUVA therapy damages psoriatic and normal lymphoid cells within milliseconds

Results of previous investigations have indicated that photochemotherapy (PUVA) attacks membranes of target cells. Using the combination of a stopped-flow technique and laser irradiation we were able to prove that the fast PUVA effect is explainable solely by the membrane damage. Lymphoid cells of healthy persons or psoriatics were taken, within 1 ms mixed with 8-methoxy-psoralen (8-MOP) at concentrations of 1.0, 0.1, and 0.5 microgram/ml, and then irradiated by a 337-nm laser pulse (0.5 mJ/cm2) lasting some picoseconds. Approximately 1 ms after administration of 8-MOP to the cell surface at least 10% of the cells were damaged, as could be judged using the standard trypan blue exclusion test. This happened at 8-MOP concentrations of 1.0 or 0.1 microgram/ml plus laser irradiation, but a concentration of 0.05 microgram/ml 8-MOP plus laser exposure did not cause any effect within 8 ms after mixing. There was no difference between using lymphoid cells from healthy persons or from psoriatics. The fact that only a very short time is necessary before cell damage occurs means that, as far as the fast PUVA effect is concerned, a photochemical reaction involving nuclear DNA can be discounted.

Deficiency of cyclic AMP-dependent protein kinases in human psoriasis

To determine possible differences in the cyclic AMP-dependent protein kinases of normal and psoriatic human fibroblasts, the levels of the regulatory subunits (RI and RII, respectively) of protein kinase I and protein kinase II were quantitated by photoaffinity labeling with 8-azido[32P]cAMP. The level of RII was significantly decreased, or was undetectable, in cytosol prepared from fibroblasts from five psoriatic subjects when compared to RII levels found with normal human fibroblasts. The level of cytosolic RI was decreased in fibroblasts from four psoriatic patients and was within the normal range for one diseased patient when compared to RI levels in normal human fibroblasts. The elution profile from a DEAE-cellulose column of protein kinase activity in the soluble fraction from two psoriatic patients also showed a decrease in type I kinase activity and the complete absence of type II kinase activity. Other results indicate that the level of RI in erythrocyte membranes from psoriatic subjects is significantly decreased when compared to that of erythrocyte membranes from eight normal subjects. A significant correlation (P less than 0.001) was observed between the severity of the cutaneous manifestation of the disease and the level of RI in psoriatic erythrocyte membranes. The changes noted in the levels of RI and RII in cell types other than those thought to be specifically involved in the proliferative epidermis disorder of the disease suggest a general protein kinase deficiency.

Psoriatic fibroblasts induce hyperproliferation of normal keratinocytes in a skin equivalent model in vitro

A skin equivalent model has been used to fabricate tissues with psoriatic and normal cells. Psoriatic fibroblasts can induce hyperproliferative activity in normal keratinocytes. The psoriatic epidermis from lesions continues to proliferate at high rates for at least 15 days in this model, and normal fibroblasts are unable to suppress this hyperproliferation. The primary defect in psoriatic skin may reside in the dermal fibroblast.

Effects of alpha and beta interferons on cultured human keratinocytes

Interferons (IF) are a family of glycoproteins known for their antiviral activity and the ability to inhibit growth and alter behavior of various normal and transformed cell types, both in vivo and in vitro. Because cultured human keratinocytes (HK) produce IF in response to viral infection, we undertook studies of alpha-IF and beta-IF effects on HK. Cloned human IF were added at time of seeding and at each feeding to paired dishes of keratinocytes maintained in serum-free hormone-supplemented medium. At 7 days significant inhibition of growth was observed for both alpha-IF and beta-IF, as determined by cell counts, total protein, and appearance of stained colonies, and was sustained for at least two weeks during continuous IF exposure. The inhibition was substantially blocked by prior addition of cholera toxin to the medium, consistent with competition for a common cell surface receptor. Growth of a single human epidermal carcinoma cell line was much less affected by IF than was growth of the normal keratinocytes. IF also promoted terminal differentiation of keratinocytes as assessed by desquamation rate of cells from the colony surface and by proportion of total cells having cornified envelopes. IF effect on both growth and differentiation was completely reversible within days of its removal from medium. These findings suggest that IF may function as a physiologic regulator of epidermal growth in vivo with properties of a negative growth factor or chalone.

Monoclonal antibody analysis of keratin expression in epidermal diseases: a 48- and 56-kdalton keratin as molecular markers for hyperproliferative keratinocytes

The polypeptide composition of epidermal keratin varies in disease. To better understand the biological meaning of these variations, we have analyzed keratins from a number of human epidermal diseases by the immunoblot technique using AE1 and AE3 monoclonal antikeratin antibodies. The results reveal a continuous spectrum of keratin expression ranging from one closely resembling the normal in vivo pattern to one almost identical to cultured epidermal keratinocytes. Specifically, a 50-kilodalton (kd) (AE1-positive) and a 58-kd (AE3-positive) keratin are present in all diseases, supporting the concept that they represent "permanent" markers for keratinocytes. A 56.5-kd (AE1) and a 65-67-kd (AE3) keratin, previously shown to be markers for keratinization, are expressed only by lesions retaining a keratinized morphology. A 48-kd (AE1) and a 56-kd (AE3) keratin are present in all hyperproliferative (para- or nonkeratinized) disorders, but not in normal abdominal epidermis or in ichthyosis vulgaris which is a nonhyperproliferative disease. These two keratins have previously been found in various nonepidermal keratinocytes undergoing hyperproliferation, suggesting that these keratins are not epidermis-specific and may represent markers for hyperproliferative keratinocytes in general. In various epidermal diseases, there is a reciprocal expression of the (keratin) markers for hyperproliferation and keratinization, supporting the mutual exclusiveness of the two cellular events. Moreover, our results indicate that, as far as keratin expression is concerned, cultured human epidermal cells resemble and thus may be regarded as a model for epidermal hyperplasia. Finally, the apparent lack of any major, disease-specific keratin changes in the epidermal disorders studied so far implies that keratin abnormalities probably represent the consequence, rather than the cause, of these diseases.

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

Fibroblasts were cultured from the involved and uninvolved forearm skin of patients with severe generalized psoriasis and compared with those from the forearms of normal controls of similar ages. Thirteen strains were obtained from involved skin (PSA strains) and sixteen strains from uninvolved skin (PSB), with thirteen control strains (NSF). Outgrowth of fibroblasts from the psoriatic skin explants was slightly quicker than from control skin and the average proliferation rates of passaged strains were PSA 144, PSB 134 and NSF 94 (P less than 0.05). Psoriatic fibroblasts were abnormally dependent on serum for anchorage. In serum-free medium many cells rounded up and were only loosely attached to the substratum. This effect was rapid, reversible and not corrected by adding fibronectin. Cell attachment assays showed only small differences between the psoriatic and normal fibroblasts and the main effect of serum withdrawal appeared to be on spreading rather than attachment. These data suggest that the dermis of both involved and uninvolved psoriatic skin is abnormal and that the hyperactivity persists in vitro. Our findings seem most compatible with a hyperproliferative reaction of both epidermis and dermis to an extracutaneous, perhaps vascular, stimulus.

Serial cultivation of epidermal keratinocytes from psoriatic plaques

Using the combined techniques of Rheinwald and Green, and Liu and Karasek, large quantities of proliferative keratinocytes from involved (PP) or uninvolved (PN) skin of psoriatic patients and from normal skin of non-psoriatic donors (NN) can be obtained. Primary cultures, initiated from a 6-mm punch biopsy, are grown on a 3T3 feeder layer seeded on a collagen surface and fed with Dulbecco's Modified Eagle's Medium containing 20% fetal calf serum, hydrocortisone, epidermal growth factor, and cholera toxin. To test the hypothesis that the mechanism(s) responsible for the abnormal proliferation of psoriatic keratinocytes may be located within the cells themselves, primary cultures are passaged onto collagen surfaces without a feeder layer and maintained with medium plus serum, but no additional supplements, and the growth profiles of the 3 cell populations compared. No difference in morphology among these cells is observed in either primary or passaged cultures. In primary cultures, PP keratinocytes, especially those isolated from active lesions, seem to initiate growth at a slower rate than do PN and NN keratinocytes. The difference in the growth rate, as determined by cell number, DNA content, and mitotic activity, is insignificant among passaged PP, PN, and NN cells. Waves observed in the mitotic index and the metabolic activity of the passaged keratinocytes from all 3 sources suggest that the cells are synchronized during subculturing. The cells have high metabolic and mitotic activities during the first week after subculturing, indicative of an initial population of actively dividing cells. We have not found the characteristic feature of hyperproliferation seen in psoriatic keratinocytes in situ, in the cultured cells; however, it is too early to reach the definite conclusion that the mechanism(s) responsible for psoriasis does not exist in the keratinocyte itself. These 3 cell types may respond differently to agents that either enhance or inhibit cell growth and, by using the culture system outlined in this report, we may study these factors and their potential role in psoriasis.

In vitro growth rates of epidermal cells derived from the skin of psoriatic patients and non-psoriatic controls

The growth of epidermal cells derived from clinically normal skin of psoriatic patients and controls has been studied in culture. Growth rates were measured in secondary cultures established with 5 x 10(4) cells/35 mm plate without feeder layers by determining the plating efficiency, and cell yield and surface area of growth at the end of a 14-day culture period. There was no significant correlation of plating efficiency, cell yield/colony or surface area/colony with the sex or age of the donor in either the normal or psoriatic groups. The morphological development of normal and psoriatic epidermal cell cultures was similar. Comparisons of plating efficiency, cell yield/colony and surface area/colony for the normal and psoriatic groups revealed no significant difference.

Keratin polypeptide profile in psoriatic epidermis normalized by treatment with etretinate (aromatic retinoid Ro 10-9359)

The variations in the expression of epidermal keratins occurring during retinoid therapy were studied in patients with psoriasis before and during oral administration of etretinate (aromatic retinoid Ro 10-9359) and compared with normal epidermis. Sodium dodecyl sulfate polyacrylamide gel electrophoresis densitometric readings were performed on keratins extracted from epidermal cells obtained through trypsinization of skin specimens. Epidermal cells were also tested by immunofluorescence (IF) for the presence of BMZ antigens as markers of basal cells and for the presence of TK and KP (67 K, 63 K, and 55 K) with sera with antibodies against BMZ antigens and specific antisera for TK and KP. In psoriasis-involved epidermis, SDS-PAGE anaLysis showed lower amounts of 67 K and increased amounts of 63 K and 55 K, as compared with normal epidermis. Low proportions of cells expressing by IF the 67 K and the 63 K were also noted, with a defective expression of these two KP by suprabasal keratinocytes in psoriasis-involved epidermis. During etretinate administration, a return toward the normal electrophoretic pattern and a correction of the defective cellular expression of these two KP were obtained parallel with clinical improvement. These findings indicate the presence in involved psoriatic epidermis of a population of suprabasal keratinocytes that do not express the high-molecular-weight KP and show a normalization of the relative proportions of the KP with etretinate.

Maturation of human gingival keratinocytes cultured with fibroblasts from keratinizing and non-keratinizing epithelia

When keratinocytes from epidermis, gingiva and buccal mucosa are cultured in vitro they form a stratified squamous epithelium that lacks evidence of orthokeratinization or parakeratinization. We attempted to induce orthokeratinization or parakeratinization in cultured gingival keratinocytes by co-cultivation with fibroblasts from human skin, gingiva and buccal mucosa. Keratinization was defined by the morphological appearance of the cultured cells and by the presence of large molecular weight keratin proteins (63,000 and 67,000 mol. wt). Using these criteria, the chosen fibroblasts failed to induce any alteration in the pattern of keratinization. We conclude that under our present culture conditions, fibroblasts alone cannot induce keratinization in cultured keratinocytes.