Keratinocyte proliferation in wound healing and skin diseases

Immune-Epithelial Cross Talk in Regeneration and Repair

The epithelial tissues that line our body, such as the skin and gut, have remarkable regenerative prowess and continually renew throughout our lifetimes. Owing to their barrier function, these tissues have also evolved sophisticated repair mechanisms to swiftly heal and limit the penetration of harmful agents following injury. Researchers now appreciate that epithelial regeneration and repair are not autonomous processes but rely on a dynamic cross talk with immunity. A wealth of clinical and experimental data point to the functional coupling of reparative and inflammatory responses as two sides of the same coin. Here we bring to the fore the immunological signals that underlie homeostatic epithelial regeneration and restitution following damage. We review our current understanding of how immune cells contribute to distinct phases of repair. When unchecked, immune-mediated repair programs are co-opted to fuel epithelial pathologies such as cancer, psoriasis, and inflammatory bowel diseases. Thus, understanding the reparative functions of immunity may advance therapeutic innovation in regenerative medicine and epithelial inflammatory diseases.

Re-epithelialization of adult skin wounds: Cellular mechanisms and therapeutic strategies

Cutaneous wound healing in adult mammals is a complex multi-step process involving overlapping stages of blood clot formation, inflammation, re-epithelialization, granulation tissue formation, neovascularization, and remodelling. Re-epithelialization describes the resurfacing of a wound with new epithelium. The cellular and molecular processes involved in the initiation, maintenance, and completion of epithelialization are essential for successful wound closure. A variety of modulators are involved, including growth factors, cytokines, matrix metalloproteinases, cellular receptors, and extracellular matrix components. Here, we focus on cellular mechanisms underlying keratinocyte migration and proliferation during epidermal closure. Inability to re-epithelialize is a clear indicator of chronic non-healing wounds, which fail to proceed through the normal phases of wound healing in an orderly and timely manner. This review summarizes the current knowledge regarding the management and treatment of acute and chronic wounds, with a focus on re-epithelialization, offering some insights into novel future therapies.

Antimicrobial Peptide LL37 and MAVS Signaling Drive Interferon-β Production by Epidermal Keratinocytes during Skin Injury

Type 1 interferons (IFNs) promote inflammation in the skin but the mechanisms responsible for inducing these cytokines are not well understood. We found that IFN-β was abundantly produced by epidermal keratinocytes (KCs) in psoriasis and during wound repair. KC IFN-β production depended on stimulation of mitochondrial antiviral-signaling protein (MAVS) by the antimicrobial peptide LL37 and double stranded-RNA released from necrotic cells. MAVS activated downstream TBK1 (TANK-Binding Kinase 1)-AKT (AKT serine/threonine kinase 1)-IRF3 (interferon regulatory factor 3) signaling cascade leading to IFN-β production and then promoted maturation of dendritic cells. In mice, the production of epidermal IFN-β by LL37 required MAVS, and human wounded and/or psoriatic skin showed activation of MAVS-associated IRF3 and induction of MAVS and IFN-β gene signatures. These findings show that KCs are an important source of IFN-β and MAVS is critical to this function, and demonstrates how the epidermis triggers unwanted skin inflammation under disease conditions.

Effect of Nitroglycerin Ointment on Psoriatic Plaques

Background:

Nitric oxide is thought to play a major role in a number of inflammatory diseases. Psoriasis is a common inflammatory disease of the skin.

Objective:

To determine the effect of nitric oxide on psoriasis, nitroglycerin that is converted into nitric oxide in human skin was applied to psoriatic plaques.

Methods:

Nine individuals with chronic plaque-type psoriasis were treated with nitroglycerin ointment for 6 weeks.

Results:

The plaque of one individual improved with the application of nitroglycerin. By contrast, one individual's nitroglycerin-treated plaque improved dramatically about 6 weeks after cessation of treatment. On the other hand, the plaques of five individuals worsened with nitroglycerin treatment. Moreover, in one individual, the nitroglycerin-treated plaque increased in size, whereas the placebo-treated plaque improved slightly.

Conclusion:

Nitroglycerin ointment and, by extension, nitric oxide, may affect both the initiation and resolution of psoriasis.

Virgin olive oil blended polyurethane micro/nanofibers ornamented with copper oxide nanocrystals for biomedical applications

Recently, substantial interest has been generated in using electrospun biomimetic nanofibers of hybrids, particularly organic/inorganic, to engineer different tissues. The present work, for the first time, introduced a unique natural and synthetic hybrid micronanofiber wound dressing, composed of virgin olive oil/copper oxide nanocrystals and polyurethane (PU), developed via facile electrospinning. The as-spun organic/inorganic hybrid micronanofibers were characterized by scanning electron microscopy (SEM), energy dispersive X-ray analysis, X-ray diffraction, electron probe microanalysis, and transmission electron microscopy. The interaction of cells with scaffold was studied by culturing NIH 3T3 fibroblasts on an as-spun hybrid micronanofibrous mat, and viability, proliferation, and growth were assessed. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay results and SEM observation showed that the hybrid micronanofibrous scaffold was noncytotoxic to fibroblast cell culture and was found to benefit cell attachment and proliferation. Hence our results suggest the potential utilization of as-spun micronanoscaffolds for tissue engineering. Copper oxide–olive oil/PU wound dressing may exert its positive beneficial effects at every stage during wound-healing progression, and these micronanofibers may serve diverse biomedical applications, such as tissue regeneration, damaged skin treatment, wound healing applications, etc. Conclusively, the fabricated olive oil–copper oxide/PU micronanofibers combine the benefits of virgin olive oil and copper oxide, and therefore hold great promise for biomedical applications in the near future.

Helium-neon laser improves skin repair in rabbits

The purpose of this study was to evaluate the influence of helium-neon laser on skin injury in rabbits. For this purpose, 15 New Zealand rabbits underwent bilateral skin damage in leg. Helium-neon laser light, at a fluence of 6 J∕cm2 and wavelength of 632.8 nm, was applied on the left legs (laser group). The right leg lesions (control group) served as negative control. All sections were histopathologically analyzed using HE sections. The results showed little infiltration of inflammatory cells, with proliferation of fibroblasts forming a few fibrous connective tissue after 1 week post-injury. The lesion on the 3rd week was characterized by granulation tissue, which formed from proliferated fibrous connective tissue, congested blood vessels and mild mononuclear cell infiltration. On the 5th week, it was observed that debris material surrounded by a thick layer of connective tissue and dense collage, fibroblasts cells present in the dermis covered by a thick epidermal layer represented by keratinized epithelium. Taken together, our results suggest that helium-neon laser is able to improve skin repair in rabbits at early phases of recovery.

Copper-taurine (CT): a potential organic compound to facilitate infected wound healing

Taurine plays various important roles in a large number of physiological and pathological conditions in human body, such as the cytoprotective functions, antioxidant, anti-inflammatory and anti-apoptosis effects. Copper demonstrates a critical effect in the processes of wound healing, including induction of endothelial growth factor, angiogenesis, antimicrobial potency and expression and stabilization of extracellular matrix. Both copper and taurine are effective in accelerating wound healing, but it was rarely reported about the formation of copper complexes of taurine and the effect of the compound in wound healing. Generally speaking, to human body, organic compound could provide a better bioavailability than the inorganic ones. We thus hypothesize that taurine combined with copper would be a new therapeutic candidate for infected wound healing. We name the new compound copper-taurine (CT). Copper-taurine (CT) added into the wound dressings would not only reduce the risk of wound infection, but, more importantly, would stimulate wound repair directly. The sustained release of copper and taurine from the wound dressings into the wound site would together facilitate the wound healing more potently.

The effects of topical tripeptide copper complex and helium-neon laser on wound healing in rabbits

The aim of this study was to compare the clinical and histopathological effects of tripeptide copper complex (TCC) and two different doses of laser application (helium-neon laser, 1 and 3 J cm(-2)) on wound healing with untreated control wounds. Experimental wounds were created on a total of 24 New Zealand white rabbits and topical TCC or laser was applied for 28 days. The wounds were observed daily, and planimetry was performed on days 7, 14, 21 and 28 to measure the unhealed wound area and percentage of total wound healing. Biopsies were taken weekly to evaluate the inflammatory response and the level of neovascularization. The median time for the first observable granulation tissue was shorter (P < 0.05) in the low and high dose laser groups than in the control group (3 and 2.66 vs. 4.5 days), but was not different between the TCC and control groups (4.16 vs. 4.5 days). Filling of the open wound to skin level with granulation tissue was faster (P < 0.05) in the TCC and high dose laser groups than in the control group (14 and 16 vs. 25 days), but was not different between the low dose laser and control groups (23 vs. 25 days). The average time for healing was shorter (P < 0.05) in the TCC and high dose laser groups (29.8 and 30.2 vs. 34.6 days), but was not different between the low dose laser and control groups (33.8 vs. 34.6 days). Histopathologically, wound healing was characterized by a decrease in the neutrophil counts and an increase in neovascularization. The TCC and high dose laser groups had greater neutrophil and vessel counts than in the control group, suggesting a more beneficial effect for wound healing.

Lessons learned from psoriatic plaques concerning mechanisms of tissue repair, remodeling, and inflammation

Following injury, skin establishes a balance between too little inflammation increasing risk of infection, and excessive inflammation contributing to delayed wound healing and scarring. Mounting evidence indicates both initiation and termination of inflammation involve active mechanisms. Not only does inflammation itself seem to be a paradox because inflammatory responses are both essential and potentially detrimental, but one chronic inflammatory skin disease (e.g. psoriasis) presents additional paradoxes. While plaques share several factors with wound healing, two understudied and puzzling aspects include why do not inflamed plaques more frequently transform?; and why do not plaques result in scarring? To get at these questions, we review responses involved in wound repair. Oral mucosa was probed because, like fetal skin, wound repair is characterized by its rapidity, low inflammation, and scarless resolution. Active roles for macrophages as both initiators and terminators of inflammation are highlighted. Therapeutic implications are discussed regarding psoriasis and pyoderma gangrenosum. Based on biochemical and immunohistochemical considerations linking psoriatic plaques to hard palate, a novel metaplastic model is presented. We hypothesize saliva and chronic trauma contribute to a constitutive epithelial program where keratinocyte proliferation is more intense prior to differentiation, accompanied by keratin 16 expression in hard palate, thereby resembling plaques. Rather than viewing psoriasis as a nonspecific response to inflammation, we postulate a metaplastic switch by which prepsoriatic skin is converted to a distinct adult tissue type resembling hard palate. In summary, many lessons can be learned by focusing on complex processes involved in regulation of inflammation, tissue repair, and remodeling.

Cytokeratin expression in initial oral mucositis of head and neck irradiated patients

OBJECTIVE

The aim of this work was to study cytokeratin (Ck) expression in initial radiation-induced oral mucositis.

STUDY DESIGN

Eleven cases of initial radiomucositis of the buccal mucosa and 9 normal specimens were immunostained for Ck 1, 5, 6, 7, 8, 10, 14, 16, 18, and 19 by immunoperoxidase method.

RESULTS

Expression of Ck 1, 6, 10, and 16 was stronger in mucositis than in normal mucosa. Ck 7, 8, and 18 were negative for both control and study groups. Ck 5, 13, and 14 were positive for both groups, nevertheless suprabasal staining for Ck 14 was more evident in mucositis than in the control group. Sporadic staining for Ck 19 was observed in 1 case of mucositis and in 2 controls.

CONCLUSIONS

Increased Ck expression can be associated with the reactive proliferation of the epithelium and increasing resistance of the oral mucosa during the initial phases of radiotherapy.

Characterization of the expression and function of N-methyl-D-aspartate receptor in keratinocytes

The N-methyl-D-aspartate (NMDA) receptor is expressed on neural tissue where it gates calcium ion entry upon stimulation. Using immunohistochemistry, it has been demonstrated in this study that the NMDAR1 receptor is also expressed on keratinocytes (KCs) in normal human skin and inflamed psoriatic skin in vivo. Furthermore, the NMDA receptor was functional as demonstrated by the ability of this receptor to trigger Ca++ influx in KCs. Incubation of cultured, human KCs with MK-801 decreases the cell growth and induces an increase in apoptosis. These findings demonstrate that the KC expression of NMDA receptor is a mechanism through which the influx of Ca++ into the cell can be regulated and suggest that the expression of this receptor may play a role in the regulation of KC growth and differentiation.

Psoriatic lesional keratinocytes promote the maturation of human monocyte-derived Langerhans cells

BACKGROUND

Langerhans cells (LCs) are important antigen-presenting cells in the epidermis and may play a key role in the pathogenesis of psoriasis. It has been proven that LCs isolated from psoriatic lesions are abnormal. However, the mechanism of the abnormality has not been reported so far.

OBJECTIVE

In the present study, we investigated the effect of psoriatic lesional keratinocytes on the maturation of LCs.

METHODS

Monocytes isolated from healthy peripheral blood could differentiate into LCs in the presence of granulocyte-macrophage colony-stimulating factor, interleukin (IL) 4 and transforming growth factor beta1 for 5 days. Then, human monocyte-derived LCs were cultured with supernatants from psoriatic lesional keratinocytes for another 2 days. Their phenotypes and phagocytic capacity were analyzed by flow cytometry. IL-12 secreted by LCs was determined by ELISA.

RESULTS

Supernatants from psoriatic lesional keratinocytes could up-regulate the expression of HLA-DR and CD86 on LCs more significantly than supernatants from healthy keratinocytes, but less powerfully than lipopolysaccharide. The levels of IL-12 secreted by LCs also increased. In contrast, the expression of CD1a on LCs and their phagocytic capacity were reduced.

CONCLUSION

Human monocyte-derived LCs cultured with supernatants from psoriatic lesional keratinocytes displayed the characteristics of maturation. This suggests that psoriatic lesional keratinocytes might secrete some factors that could promote the maturation of LCs, which may play important roles in immune reactions related to psoriasis.

Induction of transcription factor AP-2 by inflammatory cytokines in human keratinocytes

Activator protein-2 is an important transcription factor for the activation of a number of genes. Here we report the induction of activator protein-2 in response to inflammatory cytokines such as interleukin-6 in keratinocytes. Immunoblotting and semiquantitative reverse transcriptase-polymerase chain reaction assays using normal human keratinocytes revealed that interleukin-6 caused a time- and concentration-dependent induction of activator protein-2 mRNA and protein. The increase of activator protein-2 mRNA was detected at 30 min after stimulation and that of activator protein-2 protein was at 2 h. Their levels were lower than the control levels at 24 h. The interleukin-6-dependent induction of activator protein-2 mRNA was completely blocked by adding actinomycin D, whereas it was approximately 50% affected by cycloheximide. Co-incubation with neutralizing antibodies against various inflammatory cytokines resulted in inhibition of the interleukin-6-dependent activator protein-2 induction at varying degrees, indicating an involvement of various cytokines in the activator protein-2 induction. The activator protein-2 induction was observed in keratinocytes derived from lesional skins with psoriasis or squamous cell carcinoma, and the high levels of activator protein-2 were histochemically detected in these lesions. Furthermore, a gel mobility shift assay using the nuclear extracts from interleukin-6-treated cells showed that interleukin-6 induced the functional activator protein-2 protein for the gene activation. These findings suggest a possible regulation mechanism of activator protein-2 through a complex cytokine system, which is conceivably the initial reaction leading to skin inflammation, and resultant keratinocyte growth and carcinogenesis.

Is an epitope on keratin 17 a major target for autoreactive T lymphocytes in psoriasis?

Psoriasis is a T cell-mediated inflammatory skin disease that has been associated with infections by group A beta-haemolytic streptococci. In a previous study of patients with active psoriasis we demonstrated an increased frequency of circulating Th1-like cells that responded to 20 amino acid (aa) streptococcal M-peptides sharing sequences with human keratin. These cells disappeared after ultraviolet B (UVB)-induced clinical remission. Using T cells from the blood of 17 psoriatic patients and 17 healthy controls we have now compared the numbers of interferon-gamma (IFN-gamma)-producing cells induced by seven 18-20 aa keratin peptides and five corresponding M-peptides. The most frequent and strongest responses were observed to a peptide from keratin 17 that shares ALEEAN sequence with M-protein. The responses to this peptide were stronger than to the corresponding M-peptide containing the ALEEAN sequence. After UVB treatment T cell responses to all the M- and keratin peptides were abolished, while responses to the positive control antigen streptokinase/streptodornase (SK/SD) were not affected. These findings are consistent with the notion that aa sequences which keratin has in common with M-protein may be a major target for autoreactive T cells in psoriasis.

Different growth properties in response to epidermal growth factor and interleukin-6 of primary keratinocytes derived from normal and psoriatic lesional skin

Epidermal growth factor (EGF) family members and its receptor (EGFR) are thought to have an important role in the proliferation of epidermal keratinocytes. In this report, we investigated the EGF/EGFR system in primary keratinocytes derived from normal and psoriatic lesional skin. EGF elicited the growth of both normal human keratinocytes (NHKs) and psoriatic lesional keratinocytes (PLKs). Interleukin-6 (IL-6) potentiated the EGF-dependent growth of NHKs, but has no observable effect on PLKs, while IL-6 itself showed no growth-stimulating activities in both cell types. Immunodetection and in situ hybridization analyses revealed that IL-6 induces EGFR expression in NHKs in a time- and dose-dependent manner. This EGFR expression decreased reversibly to an undetectable level when IL-6-treated NHKs were re-cultured in IL-6-free conditions. On the other hand, PLKs expressed high levels of EGFR even when unstimulated and the expression level was not affected by IL-6 stimulation. These results suggest that the EGF/EGFR system is involved in the growth of NHKs and PLKs and that IL-6 potentiates NHK growth partly through the induction of EGFR. The different EGFR regulatory system may contribute to the pathogenesis of psoriasis.

Expression of major histocompatibility complex class II molecules by dermal inflammatory cells, epidermal Langerhans cells and keratinocytes in canine dermatological disease

The distribution of Major Histocompatibility Complex (MHC) Class II molecules in skin biopsies from 42 dogs with primary skin disease and six control dogs was examined by indirect immunohistochemical methods. Canine epidermal Langerhans cells constitutively expressed MHC Class II and the number of such cells was increased in the epidermis of dogs with discoid lupus erythematosus (n = 10), hypersensitivity dermatitis (n = 10) or deep pyoderma (n = 13) but not in eight cases of pemphigus foliaceus. Expression of MHC Class II by epidermal and follicular keratinocytes was observed in a ninth dog with pemphigus foliaceus. Within dermal inflammatory infiltrates, Class II was expressed by macrophages, dendritic cells and fibroblasts but not by neutrophils, eosinophils, mast cells or plasma cells. Only occasional dermal lymphocytes expressed surface MHC Class II, but nodular aggregates of strongly Class II-positive lymphocytes were observed within the dermis of two dogs with discoid lupus erythematosus.

Natural complex of cytokines is a potent stimulant to posttraumatic regeneration in rabbit cornea

We elaborated an original technique based on local application of natural complex of cytokines (NCC) secreted by autologous peripheral leukocytes. In this study, we evaluated NCC influence on the healing of penetrating corneal wounds. NCC was derived from supernatants of PHA-stimulated rabbit peripheral leukocytes. Biological tests revealed the presence of IL-1, TNF, IL-6, MIF, and LIF in the complex. Chinchilla rabbits with standard penetrating corneal wounds received daily NCC instillation. The controls were instilled with cultural media 199 with antibiotics. At 24 hours, 3, 7, 14 and 30 days post-wounding, the rabbits were euthanized. We performed morphometry of corneal cross-sections stained with hematoxylin and eosin. In NCC-treated animals, we observed more vigorous migration and activation of neutrophils and macrophages followed by augmented resorption of fibrin. The later post-injury period (14-30 days) was marked with complete healing of the endothelial defect (in the controls, the mass of proliferating cells projected into the anterior eye chamber) and mature scar tissue with a higher content of fibrous component. NCC-treated eye scars were 1.6-fold thinner than the controls'. Local application of NCC promotes effective healing of posttraumatic cornea. It regulates all stages of regeneration and prevents rude scarring.

Kinetics and regulation of human keratinocyte stem cell growth in short-term primary ex vivo culture. Cooperative growth factors from psoriatic lesional T lymphocytes stimulate proliferation among psoriatic uninvolved, but not normal, stem keratinocytes

Flow cytometric analysis of primary ex vivo keratinocyte cultures demonstrated that stem cells, (beta 1 integrin+, keratin 1/keratin 10 [K1/K10-], proliferating cell nuclear antigen [PCNA-] [Bata-Csorgo, Zs., C. Hammerberg, J. J. Voorhees, and K. D. Cooper. 1993. J. Exp. Med. 178:1271-1281]) establish such cultures. This methodology also enabled the quantitation of synchronized recruitment of these cells from G0 into G1 of the cell cycle (PCNA expression), which preceded bright beta 1 integrin expression. (beta 1 integrinbright expression has been shown to be a characteristic feature of keratinocyte stem cells in culture (Jones, P. H., and F. M. Watt. 1993. Cell. 73:713-724). Using the above assay, we determined whether lesional T lymphocytes in psoriasis could be directly responsible for the induction of the stem cell hyperproliferation that is characteristic of this disease. Indeed, CD4+ T lymphocytes, cloned from lesional psoriatic skin and stimulated by immobilized anti-CD3 plus fibronectin, promoted psoriatic uninvolved keratinocyte stem cell proliferation via soluble factors. This induction appeared to be through accelerated recruitment of stem cells from their quiescent state (G0) into cell cycle. By contrast, normal keratinocyte stem cells exhibited no such growth stimulation. Supernatants exhibiting growth induction all contained high levels of GM-CSF and gamma-IFN, low IL-3 and TNF-alpha, and variable IL-4. Only anti-gamma-IFN antibody was able to neutralize growth stimulatory activity of the supernatants on psoriatic uninvolved keratinocyte stem cells. However, because recombinant gamma-IFN alone inhibited growth in this assay, these data suggest that, in psoriasis, gamma-IFN acts cooperatively with other growth factors in the immune induction of cell cycle progression by the normally quiescent stem cell keratinocytes.

Changes in crevicular fluid levels of interleukin-1 beta, leukotriene B4, prostaglandin E2, thromboxane B2 and tumour necrosis factor alpha in experimental gingivitis in humans

We conducted a study to determine the sequence of cytokine and lipid mediator activation within the periodontium during the development of experimental gingivitis in humans. Crevicular fluid samples were collected from 7 previously cleaned, healthy patients at baseline, 1, 2, 3 and 4 weeks following the cessation of all oral hygiene measures. Gingival and plaque scores were taken at each visit to follow the development of gingivitis and plaque retention. Crevicular fluid samples were assayed in quadruplicate for prostaglandin E2 (PGE2), thromboxane B2 (TxB2), leukotriene B4, interleukin-1 beta (IL-1 beta) and tumour necrosis factor alpha (TNF alpha) by RIAs or ELISAs, maintaining site pairing to examine temporal changes. Redness scores (expressed as mean percentage of sites with redness present) increased almost linearly from a baseline value of zero to approximately 40% at 1 week, 59% at 2 weeks, 83% at 3 weeks and 100% at 4 weeks. The mean % of sites with bleeding on probing increased gradually from zero at baseline to 5% at 3 weeks and then rose abruptly to 25% at 4 weeks. CF-PGE2 and CF-TxB2 levels remained fairly stable at baseline levels for the first 3 weeks then rose sharply by 2.5- and 2-fold, respectively, at 4 weeks. CF-LTB4 levels increased 2-fold by 1 week and 4-fold by 4 weeks. The CF levels of IL-1 beta increased abruptly from mean baseline values of 16.5 +/- 9.3 ng/ml to 131 +/- 76.0 ng/ml at 1 week and remained at this level for the duration of the experiment.(ABSTRACT TRUNCATED AT 250 WORDS)

Skin response to tuberculin in pig foetuses and germ-free piglets

Cellular response to intradermally administered PPD (2 TU) was demonstrated in pig foetuses of various ages and in germ-free piglets. CD2+, CD4+, CD8-, 86D-, SLA-D- T lymphocytes were the predominant cells in the skin tuberculin reaction in both foetuses and germ-free animals. Reactive T cells were observed as early as in mid-gestation, whereas SLA-D+ (porcine MHC class II) cells appeared only in older foetuses. Polymorphonuclear leukocytes were never observed in the PPD reaction.

A distinct stratum corneum antigen in psoriasis and its reactions with stratum corneum autoantibodies

Stratum corneum antibodies are ubiquitous and can be detected by various immunological methods. Of these, the ones detected by hemagglutination undergo changes in antibody titers and have been implicated in psoriasis. The purpose of our study was to examine if differences exist in the activities of the antigens isolated from psoriatic scales in comparison to normal callus. Stratum corneum antigens were prepared by trypsin-phenol-water extraction. The water phase, which contains the stratum corneum antigen, was used to sensitize the red blood cells in the hemagglutination assay. The antibody activity in human sera was determined before and after absorption with antigens isolated from callus, psoriatic scales, and cell envelopes. We found notable differences in the antigens obtained from callus and psoriatic scales. These include higher antibody titers to the antigens of the scales, the presence of unique antigenic determinants on psoriatic scales and the localization of the antigen on cell envelopes. These immunological differences were corroborated by the marked biochemical differences of certain amino acids, most notably glycine and proline, and these differences were unique to psoriatic scales as they were not shared with other hyperproliferative disorders.

Distribution of cytokeratins in oral cytological smears of HIV-infected patients

Cytological smears (CS), taken from the lateral border of the tongue of HIV-seropositive patients (HIV+) (n = 34) and of seronegative controls (HIV-) (n = 16), were examined by means of immunocytochemistry (APAAP) for the distribution patterns of different cytokeratins and MHC class II antigens. Compared with HIV- patients in CS of HIV-infected patients cornification associated cytokeratins 10/11 were increased, while the number of keratinocytes positive for cytokeratins 13/16 was comparable in both groups. Expression of simple epithelial cytokeratins 19, rarely observed in CS of HIV- patients, was a frequent findings in CS of HIV+ patients. Keratinocytes positive for MHC class II antigens were observed in CS of 12/34 HIV+, while all control CS were negative. In the group of HIV+ patients no correlation was found between the clinical presence of HL and the expression of cytokeratins or class II antigens. The altered distribution of cytokeratins may reflect local responses to proliferative stimuli or local inflammation due to the presence of microbial antigens or may occur as a general unspecific reaction in the setting of systemic viral infection. This non-invasive technique seems to be a valuable tool to determine the proliferation rate of oral epithelial cells.

Pathophysiology of cutaneous inflammation

For the better part of the past century, dermatologists have regarded the skin primarily as a large protective coat. Epidermal keratinocytes were highlighted for their production of keratins and lipids, which contributed to the structural integrity and barrier formation of skin. This "saran-wrap" perspective of skin mentioned keratinocytes only in cutaneous inflammatory reactions as passive targets for damaging diffusion products of infiltrating leukocytes. However, sufficient compelling in vitro and in vivo evidence is rapidly accumulating to support the novel perspective that epidermal keratinocytes can initiate and actively participate in the perpetuation of numerous cutaneous inflammatory reactions that involve a highly diverse array of inciting agents. This presentation emphasizes the keratinocyte and highlights the dynamic immunomodulatory capacity of this overlooked epidermal cell.

Does prolactin play a role in skin biology and pathology?

Despite its extensive repertoire of biological activities, which include the growth- and osmoregulation of epithelial tissues as well as immunoregulatory properties, the potential significance of the pituitary hormone prolactin (PRL) for human skin biology and pathology has yet to be fully appreciated. In this essay, the hypothesis is presented that PRL acts as a neuroendocrine modulator of skin epithelial cell proliferation and of the skin immune system by forming a 'prolactin-circuit' between the central nervous system and the skin. Binding to specific skin receptors, modulation of cytokine release in the skin, and stimulation of somatomedin release by mesenchymal cells are among the suggested pathways by which PRL could affect epithelial cell growth in the skin. Potential feedback signals, arising from the skin and modifying pituitary PRL release, are briefly outlined. Centering on the role of PRL in both psoriasis and hair growth as models for studying the proposed PRL-skin connection, clinical and experimental evidence in support of this theory is discussed in the context of a 'neuroimmune-dermatological' perspective.

T-lymphocyte-activating properties of epidermal antigen-presenting cells from normal and psoriatic skin: evidence that psoriatic epidermal antigen-presenting cells resemble cultured normal Langerhans cells

Fresh and cultured human Langerhans cells display disparate functional programs, based on their capacities to activate autologous and allogeneic T cells, and with respect to their susceptibility to inhibition by transforming growth factor-beta (TGF beta). We have compared the functional properties of epidermal antigen-presenting cells (APC) procured from uninvolved and involved skin of patients with psoriasis with fresh and cultured normal epidermal cells. Freshly obtained psoriatic epidermal APC resembled cultured normal epidermal cells in their superior capacity to activate syngeneic and allogeneic T cells; fresh normal epidermal cells failed to activate syngeneic T cells, and induced only modest proliferation among allogeneic T cells. The modest T-cell--activating properties of fresh, normal epidermal cells were not suppressed by TGF beta, whereas the T-cell--activating potential of psoriatic epidermal cells, cultured normal epidermal cells, and blood APC was inhibited approximately 50% by TGF beta. Thus, fresh psoriatic epidermal APC resemble cultured normal epidermal cells functionally. Because these properties are already evident in cells obtained from uninvolved psoriatic skin, the "cultured" functional phenotype of epidermal APC in this disease may precede the appearance of active psoriatic skin lesions. Surface marker analysis of normal and psoriatic epidermal cell suspensions revealed that virtually all of the bone marrow--derived cells in normal epidermal cell suspensions were conventional (CD1+) Langerhans cells, whereas CD1+ cells comprised only a minority of bone marrow--derived (CD45+) cells in psoriatic epidermis. It is speculated that some of the CD1-, CD45+ cells in psoriatic epidermis may be Langerhans cells that have lost their "fresh" phenotype. These data indicate that an abnormality in epidermal APC function exists in psoriatic skin--even before clinical lesions develop, and we speculate that the abnormal capacity of psoriatic epidermal APC to activate syngeneic T cells may be important in the expression of keratinocyte pathology. Because psoriatic epidermal APC functions were profoundly inhibited in vitro by treatment with cyclosporin A, the effectiveness of this drug in psoriasis may be due in part to its ability to inhibit epidermal antigen-presenting cell function in vivo.

Therapeutic use of cytokines in dermatology

Cytokines are glycoproteins produced by many different cells. Via binding to specific receptors on target cells they regulate the activation, differentiation, and proliferation of immune and nonimmune cells. After injury keratinocytes synthesize and release cytokines such as interleukins, colony stimulating factors, and growth factors. In addition, a network of interacting cytokines appears to be crucial to maintain proper balance. Dysregulation may contribute to certain diseases, particularly those of infectious and autoimmune origin. Therefore many of these mediators appear to be promising candidates to treat infectious and malignant diseases. This article briefly discusses the most important cytokines. Newly developed regimens with cytokines to treat cutaneous disorders will be reviewed.

Production of interleukin-1 and interleukin-6 by human keratinocytes and squamous cell carcinoma cell lines

Cultured human keratinocytes and squamous cell carcinoma (SCC) cell lines were analyzed for the presence of ribonucleic acid (RNA) transcripts for the cytokines interleukin-1 and interleukin-6 and for these proteins. This study demonstrates that both cytokines are synthesized and secreted by both normal keratinocytes and SCC lines. The rate of secretion of these cytokines can be augmented in response to a variety of stimuli including tumor necrosis factor-alpha, granulocyte-macrophage colony stimulating factor, transforming growth factor-beta and the combination of lipopolysaccharide and phorbol myristate acetate. Interleukin-1 and interleukin-6 have been reported to influence the proliferation of cultured human fibroblasts. However, these cytokines had no significant effect on the proliferation of human keratinocytes or the SCC lines tested. Although it seems unlikely that interleukin-1 or interleukin-6 could directly influence keratinocyte proliferation in vivo, the capacity of these cells to synthesize and release these cytokines supports earlier observations that keratinocytes may play an important role in augmenting an immune or inflammatory response.

Insulin-like growth factors are mitogenic for human keratinocytes and a squamous cell carcinoma

Normal adult human keratinocytes in monolayer culture and SCL-1, a skin-derived squamous-cell carcinoma cell line, were investigated for the expression of receptors for insulin-like growth factors (IGF) and insulin. As demonstrated by affinity crosslinking, radiolabeled IGF-1, IGF-2, and insulin bound specifically to both cell types. Each cell expressed type I IGF receptors, with affinity for IGF-1 greater than IGF-2 much greater than insulin. Insulin receptors, with highest affinity for insulin, were also present on both cells. However, keratinocytes and SCL-1 cells differed in 125I-IGF-2 binding. 125I-IGF-2-bound to both type I and type II IGF receptors in normal keratinocytes, but bound predominantly to membrane-associated IGF binding proteins in SCL-1. IGF-1 was slightly more potent than IGF-2 in stimulating growth of both keratinocytes and SCL-1 cells. In keratinocytes, concentrations of IGF-1 ranging from 5-100 ng/ml, and of IGF-2 from 50-100 ng/ml, resulted in a significant increase in cell number. At the maximum dose of 100 ng/ml, either IGF-1 or IGF-2 caused a 2.3-times increase in cell number. In SCL-1 cells, IGF-1 was more potent than IGF-2 or insulin at lower concentrations, but either IGF-1 or IGF-2 at the maximal concentration of 333 ng/ml stimulated a 4.7-times increase in thymidine incorporation. The stimulatory effect of insulin in SCL-1 was 10-50 times less potent than that of the IGF. The effect of either IGF on SCL-1 was completely inhibited by the type I IGF receptor antibody alpha IR-3, suggesting that both IGFs are mitogenic through the type I IGF receptor. Insulin action was partially blocked by alpha IR-3, suggesting that insulin can act through both the insulin and type I IGF receptors. It thus appears that IGF-1 and IGF-2 are mitogens for normal and transformed human keratinocytes and that their actions are primarily mediated through the type I IGF receptor, whereas insulin is a mitogen through both the IGF-1 receptor and the insulin receptor.

Differences in low density lipoprotein receptor expression in the suprabasal layer of normal and psoriatic epidermis

Previous morphological experiments on the distribution of binding sites for low density lipoprotein (LDL) on normal and psoriatic epidermis in situ, done with the LDL-gold technique [Mommaas-Kienhuis AM, et al. J Invest Dermatol 89: 513-517, 1987.] showed an unequivocal correlation between the ability to bind LDL-gold complexes and the state of keratinocyte differentiation. To determine the involvement of the LDL receptor in this phenomenon, we applied immunoelectronmicroscopical methods in conjunction with a monoclonal anti-LDL receptor antibody. Biopsy specimens of normal and psoriasis skin were fixed before being embedded in Lowicryl K4M. Ultrathin sections were incubated first with the anti-LDL receptor antibody, and then with a second antibody conjugated to colloidal gold. On basal cells of both normal and psoriatic epidermis the LDL receptor was distributed evenly between the cell surface and the cytoplasm. No obvious differences in the density of LDL receptors were observed. However, cells from the suprabasal layer showed two striking differences in the localization of the LDL receptor: 1) normal epidermis showed fewer LDL receptor molecules, whereas in psoriasis epidermis the number increased relative to those on basal cells; and 2) in normal suprabasal cells most of the LDL receptors were located inside the cell, but in psoriasis the majority was found on the cell surface. Both phenomena are discussed and we postulate that the higher expression of LDL receptors in psoriasis suprabasal cells and the high expression of the receptor on the cell surface is connected with the hyperproliferative state of the disorder.

Flow cytometric quantification of human epidermal cells expressing keratin 16 in vivo after standardized trauma

The intermediate filament protein keratin 16 is expressed in hyperproliferative epidermis. The present study aims to clarify the relationship between the expression of this keratin type, hyperproliferation (percentage of cells in SG2M phases), and keratinization (keratin 10 expression). These three parameters were quantified in biopsy material taken at different time intervals following sellotape stripping--this being a dynamic in vivo model for the induction of hyperproliferation. From the biopsy specimens cell suspensions were prepared, labeled with antibodies KS8.12 (specially directed against keratin 16) and RKSE60 (directed against keratin 10), and analyzed using flow cytometry. Percentages of cells in SG2M phases were assessed by measuring the relative DNA content after propidium iodide staining. Keratin 16 expression in the suprabasal layer anticipated epidermal proliferation, suggesting a role of the suprabasal compartment in the induction of epidermal growth. Keratin 10 expression decreased about 1 day after the onset of keratin 16 expression, indicating that these processes do not depend directly upon each other.

Effects of intradermal gamma-interferon in cutaneous leishmaniasis

The clinical and immunological evolution of lesions in cutaneous leishmaniasis was assessed after treatment with human recombinant gamma interferon (rIFN-gamma). 3 weeks after rIFN-gamma treatment of lesions due to Leishmania braziliensis guyanensis, 12/13 had become smaller compared with 6/13 control lesions; only 4 treated lesions were free of parasites. 9 of 13 L tropica lesions treated with rIFN-gamma resolved completely within 4-8 weeks of treatment. An acute inflammatory reaction around treated lesions was more common in lesions due to L tropica. There were no other local or systemic adverse reactions. Histological and immunohistochemical studies indicate that local application of rIFN-gamma enhances cell-mediated immune responses and thus promotes healing of cutaneous leishmaniasis.