Comedone formation: Etiology, clinical presentation, and treatment

An important feature in the etiology of acne is the presence of pilosebaceous ductal hypercornification, which can be seen histologically as microcomedones (Fig 1) and clinically as blackheads, whiteheads, and other forms of comedones, such as macrocomedones. There is a significant correlation between the severity of acne and the number and size of microcomedones (follicular casts), the presence of which is a measure of comedogenesis. This correlation can be demonstrated by skin surface biopsy using cyanoacrylate gel. In this procedure, microcomedones are sampled by applying cyanoacrylate gel to the skin surface. A glass microscopic slide is then applied on top of the gel and pressed firmly onto the skin for 1 minute(1-3). The glass slide is gently removed, taking with it the upper part of the stratum corneum and microcomedones, which are then analyzed by low-power microscopy or digital image analysis.(1-3)

Inflammation in acne scarring: a comparison of the responses in lesions from patients prone and not prone to scar

BACKGROUND

Many patients with inflammatory acne suffer from significant scarring, which is disfiguring and difficult to treat. A cell-mediated immune response is considered to be involved in the pathogenesis of acne, although the extent of this response has been found to differ among patients.

OBJECTIVE

To assess whether there were differences in the cell-mediated immune responses at different time points in inflamed lesion development and resolution in patients who were prone (S patients) and those with the same degree of inflamed acne who were not prone (NS patients) to develop scarring.

METHODS

Cellular and vascular markers were investigated using standard immunohistochemical techniques on biopsies of inflamed lesions of known duration, i.e. < 6 h (n = 14), 24 h (n = 14), 48 h (n = 10), 72 h (n = 10) and 6-7 days (n = 11) from the backs of acne patients.

RESULTS

In early lesions from NS patients there was a large influx of CD4+ T cells, macrophages and Langerhans cells with a high number of cells expressing HLA-DR. Also there was significant angiogenesis and vascular adhesion molecule expression. Cell recruitment peaked in 48 h lesions, after which leucocyte numbers decreased and vascular activity returned to normal. Of the T cells, only 50% were memory/effector (CD45RO+) and naive (CD45RA+) cells, while the remainder were unclassified (CD45RO-, CD45RA-). In early lesions from S patients, CD4+ T cell numbers were smaller, although a high proportion were skin homing memory/effector cells. Langerhans cell numbers and cellular HLA-DR expression were low, while numbers of macrophages, blood vessels and vascular adhesion molecules were high. In resolving lesions angiogenesis remained high, with a further influx of macrophages and skin homing memory/effector cells and increased cellular HLA-DR expression.

CONCLUSIONS

The cellular infiltrate was large and active with a greater nonspecific response (few memory T cells) in early lesions of NS patients, which subsided in resolution. In contrast, a predominantly specific immune response was present in S patients, which was initially smaller and ineffective, but was increased and activated in resolving lesions. Such excessive inflammation in healing tissue is conducive to scarring and suggests that the use of topical anti-inflammatory treatments would be appropriate for these patients.

Comedogenesis: some aetiological, clinical and therapeutic strategies

Hypercornification is an early feature of acne and usually precedes inflammation. It is associated with ductal hyperproliferation, and there are many controlling factors such as androgens, retinoids, sebum composition and cytokines. Cycling of normal follicles and of comedones may explain the natural resolution of comedones and, in the longer term, resolution of the disease itself. There is a need to tailor treatment according to comedonal type. Suboptimal therapy can often result from inappropriate assessments of comedones, especially microcomedones, sandpaper comedones, submarine comedones and macrocomedones. Macrocomedones can produce devastating acne flares, particularly if patients are inappropriately prescribed oral isotretinoin. Gentle cautery under topical local anaesthesia is a useful therapy in the treatment of such lesions. The newer retinoids and new formulations of all-trans-retinoic acid show a better benefit/risk ratio.

Human beta defensin-1 and -2 expression in human pilosebaceous units: upregulation in acne vulgaris lesions

A rich residential microflora is harboured by the distal outer root sheath of the hair follicle and the hair canal - normally without causing skin diseases. Although the basic mechanisms involved in the development of inflammation during acne vulgaris remain unclear, microbial agents might play an important role in this process. In this study we have analyzed by in situ hybridization and immunohistochemistry the expression patterns of two antimicrobial peptides, human beta defensin-1 and human beta defensin-2, in healthy human hair follicles as well as in perilesional and intralesional skin of acne vulgaris lesions such as comedones, papules, and pustules. Strong defensin-1 and defensin-2 immunoreactivity was found in all suprabasal layers of the epidermis, the distal outer root sheath of the hair follicle, and the pilosebaceous duct. Marked defensin-1 and defensin-2 immunoreactivity was also found in the sebaceous gland and in the basal layer of the central outer root sheath including the bulge region. The majority of acne biopsies displayed a marked upregulation of defensin-2 immunoreactivity in the lesional and perilesional epithelium - in particular in pustules - and a less marked upregulation of defensin-1 immunoreactivity. The upregulation of beta-defensin expression in acne vulgaris lesions compared to controls suggests that beta-defensins may be involved in the pathogenesis of acne vulgaris.

Comedogenesis: some new aetiological, clinical and therapeutic strategies

Hypercornification is an early feature of acne and precedes inflammation. It is associated with ductal hyperproliferation and there are many controlling factors such as androgens, retinoids and cytokines. Cycling of normal follicles and of comedones may explain the natural resolution of comedones and, in the longer term, resolution of the disease itself. There is a need to tailor treatment according to comedonal type. Suboptimal therapy can often result from inappropriate assessments of comedones, especially microcomedones, missed comedones, sandpaper comedones, submarine comedones and macrocomedones. Macrocomedones can produce devastating acne flares, particularly if patients are inappropriately prescribed oral isotretinoin. Gentle cautery under topical local anaesthesia is a useful therapy in the treatment of such lesions. The newer retinoids and new formulations of all-trans-retinoic acid show a better benefit/risk ratio. Evidence-based studies are required to allow adequate comparisons.

Differential response of sebaceous glands to exogenous testosterone

To test the hypothesis that the seborrhoea of acne is an end-organ hyper-response to androgens, a standardized dose of 2% testosterone cream was applied to the forehead of eight prepubertal boys for 6 weeks and the effect determined by measurements of sebum excretion rate (SER). Three boys showed a 15-fold increase in SER and three boys were non-responders, whereas two boys had SER values between those of the responders and non-responders. These data show that sebaceous glands are stimulated by androgens to varying degrees and support the theory of an end-organ response in acne.

Are stress proteins induced during PUVA therapy?

Heat shock or stress proteins are produced in practically all cell types when they are exposed to temperatures a few degrees above normal. Measurement of the skin temperature of patients undergoing psoralen and ultraviolet A (PUVA) cabinet treatment for psoriasis revealed that the outer layers of the skin experience a mean temperature rise of 5.3 degrees C. However, this did not produce a detectable stress response in epidermal samples taken after PUVA treatment. In vitro exposure of epidermis from biopsies or of cultured keratinocytes to a 5-7 degrees C temperature rise produced a heat shock response, as measured by an increase in the production of proteins of the HSP90 and HSP70 families. These results were confirmed by the use of specific monoclonal antibodies. The corresponding mRNAs were also analysed using labelled probes. In an in vitro system, following simulated PUVA treatment of cultured keratinocytes, increases in the synthesis of HSP90 and HSP70 were detected but these increases did not correlate with changes in mRNA levels.

In situ hybridization analysis of CRABP II expression in sebaceous follicles from 13-cis retinoic acid-treated acne patients

The aim of this study was to investigate the effects of 13-cis retinoic acid treatment on cellular retinoic acid binding protein II (CRABP II) mRNA expression in sebaceous follicles from acne patients, using in situ hybridization. Biopsies were taken from uninvolved skin areas in close juxtaposition to inflamed comedos before therapy, and at 2-4 or 14-16 weeks of treatment. Paraffin sections were used for in situ hybridization study with riboprobes transcribed from human CRABP II cDNA. After oral treatment with 13-cis retinoic acid, sebaceous glands were reduced in size and atrophic, and the ratio of sebum-free to fully differentiated (sebum-producing) sebocytes was dramatically increased. The CRABP II expression in the sebaceous gland, and to some extent in infundibular structures, was strongly increased compared with the level of expression in the epidermis. The maximum signal was always found in layers of suprabasal sebocytes lacking lipid droplets, but never in the basal layers. These findings indicate a selective activity of 13-cis retinoic acid on CRABP II mRNA expression in the sebaceous glands of acne patients.

Immunohistochemical study of desmosomes in acne vulgaris

Desmosomes contribute towards adhesion between adjacent keratinocytes. In acne vulgaris, increased intercellular adhesion is thought to contribute to the retention of keratinocytes within the follicular lumen during comedogenesis. Therefore, the distribution of different desmosomal components was investigated in normal and acne subjects. Biopsies were cryostat-sectioned (6 microns), and stained with antibodies to different desmosomal components: desmoplakin 1/2, desmoglein 1, desmocollin 3a/3b, and a late desmosomal antigen, G36-19. Desmoplakin 1/2, desmoglein 1 and desmocollin 3a/3b shared a similar distribution in follicles from control skin, from acne-affected skin, and in non-inflamed lesions. All three proteins were expressed around the periphery of keratinocytes of all the intrafollicular epidermis, except the basal lamina and the upper stratum corneum. In inflamed lesions, the expression of desmoglein 1 and desmocollin 3a/3b was diminished; in 12.5%, staining for these two proteins was completely abolished, and in 81.25% of the lesions investigated the staining was patchy. The antibody G36-19 bound to an antigen in the upper granular layer in the infundibular epidermis. No differences were noted in the staining pattern of the follicular epithelia of controls, non-inflamed, and inflamed lesions. This study, using monoclonal antibodies, did not identify any changes in the desmosomal components which might explain the increased adhesion between follicular keratinocytes during comedogenesis.

Investigation of the expression of the extracellular matrix glycoproteins tenascin and fibronectin during acne vulgaris

Tenascin and fibronectin are extracellular matrix glycoproteins which can interact with cells and alter their capacity to adhere, migrate and proliferate. In contrast with fibronectin, tenascin has a restricted distribution in normal skin, but is induced during epidermal proliferation, and in wound healing. Because acne involves hyperproliferation of ductal keratinocytes, and rupture of the duct may occur during inflammation, the distribution of tenascin and fibronectin was investigated in acne lesions, and also in acne keloids. Biopsies obtained from patients attending the acne clinics were cryostat-sectioned and stained with tenascin antiserum. The extent of tenascin staining in the dermis around the pilosebaceous unit was measured. Tenascin was continually expressed around normal control pilosebaceous ducts; it was maximal around the acroinfundibulum, extending 20.83 +/- 9.32 microns (n = 14) into the dermis, compared with staining around the infrainfundibulum (11.88 +/- 3.70 microns, n = 14). This was not significantly different from staining around normal pilosebaceous ducts obtained from acne patients. In non-inflamed lesions tenascin staining increased significantly around the infrainfundibulum to 76.88 +/- 29.97 microns (n = 12), compared with this region in the normal follicles. The staining around the acroinfundibulum did not change significantly. Around inflamed lesions the whole of the dermis was positive for tenascin. No changes were detected in the staining pattern for fibronectin, which stained the whole dermis in all the sections tested. The keloid samples stained strongly for both extracellular matrix glycoproteins. Thus, increased tenascin expression appears to be associated with the development of acne lesions.(ABSTRACT TRUNCATED AT 250 WORDS)

Quantification of cellular proliferation in acne using the monoclonal antibody Ki-67

The mechanism by which ductal hypercornification occurs in acne is uncertain. We investigated proliferation in normal and acne follicles and in the interfollicular epidermis using the monoclonal antibody Ki-67, which reacts with a nuclear antigen expressed by cells in the G1, S, M, and G2 phases of the cell cycle. Cryostat sections of biopsies from the interscapular region from acne patients and from normal volunteers were stained with Ki-67 antibody and counterstained with 2% methyl green. The number of Ki-67-positive nuclei in the basal layer were counted and expressed as a percentage of the total number of basal nuclei in the ductal or interfollicular epithelia. The data was expressed as mean percent +/- SD. In normal follicles from acne-affected sites 17.40% +/- 1.86% (n = 8) of the nuclei were Ki-67 positive. This was significantly higher (p < 0.01) than follicles from an area of skin unaffected by acne (11.01% +/- 6.16%, n = 8). In the follicular epithelia of non-inflamed lesions, the percentage of Ki-67 positive nuclei was 23.44% +/- 8.36% (n = 15). It was impossible to count the nuclei of follicular epithelium of inflamed lesions because little of this remained intact. In normal interfollicular epidermis, Ki-67-positive nuclei represented 5.33% +/- 3.36% (n = 8) of the total. This value was not significantly different from the value obtained for interfollicular epidermis near non-inflamed lesions (10.46% +/- 4.45%, n = 15). However, the number of Ki-67-positive nuclei in the interfollicular epidermis near inflamed lesions was significantly higher than either of these two values: 25.26% +/- 6.83%, n = 13, p < 0.05. Our results with Ki-67 confirm that ductal hyperproliferation occurs in acne and shows that normal follicles from acne skin may be "acne-prone."

Cold shock induces the synthesis of stress proteins in human keratinocytes

Heat shock proteins or stress proteins are synthesized when cells are exposed to a wide variety of physiologic stresses. The stress response is evolutionarily highly conserved, suggestive of an essential function(s) for the survival of organisms, protecting them from harmful trauma. Exposure to cold induces a stress response in organisms such as Drosophila melanogaster and Sarcophaga crassipalpis and this led us to determine whether or not cold shock responses occur in human skin after exposure to cold such as might occur during cryopreservation of tissues or cryosurgery. Biopsies taken from fresh human skin at chest surgery were exposed to 4, 15, 20, and 37 degrees C (control) for 60 min and then allowed to incorporate 35S-methionine at 37 degrees C for up to 3 h. Proteins from the epidermis were extracted and analyzed by sodium dodecyl-sulfate-polyacrylamide gel electrophoresis. At 15 degrees C and below there was increased synthesis of 90 and 72 kD proteins 2 h after shocking. The 72-kD protein was identified as a heat shock protein using a monoclonal antibody to HSP72 and it is proposed from electrophoretic evidence that the 90-kD protein is also a heat shock protein. Clearly, cold shock stimulates a stress response in human epidermis altering the spectrum of proteins expressed and inducing the synthesis of heat shock proteins.

Detection of Propionibacterium acnes polypeptides which have stimulated an immune response in acne patients but not in normal individuals

Patient and normal volunteer sera were used as probes in two-dimensional PAGE of P. acnes culture supernatant fluid and cell extracts to determine whether specific P. acnes polypeptides were associated with the immune reaction in acne. Eight polypeptides, M(r) 20 to 131 x 10(3), pI 4.7 to 6.5 in the cell extract, and 7 polypeptides M(r) 10 to 24 kD, pI 4.8 to 7.5 in the culture supernatant fluid were specifically highlighted by patient sera and not volunteer sera. These polypeptides were not related to described extracellular enzymes of P. acnes. It is possible that these polypeptides are involved in the induction of acne.

Simple assays of retinoid activity as potential screens for compounds that may be useful in treatment of psoriasis

Human epidermal cell cultures were used to study the effects of retinoids on keratinocyte differentiation. Keratin profiles were studied by quantitative gel electrophoresis of culture extracts, whereas the extent of envelope formation was assessed in an enzyme-linked immunosorbent assay (ELISA) using an antibody that specifically recognizes keratinocyte envelopes. Exposure of cultures to a variety of different retinoids produced both dose-dependent decreases in keratin 16 with consequent increases in the keratin 14: keratin 16 ratio, and a decrease in envelope formation. The order of activity in both assays was similar: arotinoid ethyl ester (Ro 13-6298) greater than or equal to arotinoid acid (Ro 13-7410) much greater than all trans retinoic acid (Ro 1-5488) greater than acitretin (Ro 10-1670) greater than or equal to etretinate (Ro 10-9359), the only difference being that acitretin was slightly more active than etretinate in the keratin assay whereas these retinoids were equi-active in the envelope assay. Analysis of the lesional keratins of psoriasis patients showed that etretinate caused a reduction in keratin 16 and an increase in the keratin 14:keratin 16 ratio, although the magnitude of these changes and their correlation with clinical improvement was variable. As the in vitro assays reported here are simple and quick, they allow rapid screening of compounds for retinoid-like activity.

Isotretinoin treatment of severe acne affects the endogenous concentration of vitamin A in sebaceous glands

An investigation of pooled skin samples from 22 acne patients has shown that isotretinoin and its major metabolite, 4-oxo-isotretinoin, can be detected in sebaceous glands during treatment with isotretinoin (1 mg/kg/d for 4 months). The levels are less than those in the epidermis, thus excluding selective drug distribution as a prime explanation for drug function. Oral isotretinoin markedly increases retinol levels and decreases dehydroretinol levels in the skin while on therapy. The effect is more pronounced in sebaceous glands than in epidermis and dermis. The increased retinol levels probably reflect a metabolic interference with endogenous vitamin A, since isotretinoin cannot be converted into retinol in vivo. Previous studies have shown that dehydroretinol accumulates in hyperproliferative, keratinizing skin lesions and so its reduction with isotretinoin therapy may relate to a reduction in cell proliferation or to dedifferentiation. However, the precise interrelationships of these observations need further elucidation.

Keratin gene expression during the resolution of psoriatic plaques: effect of dithranol, PUVA, etretinate and hydroxyurea regimens

Quantitative changes in the levels of keratin polypeptides extracted from keratotome shavings from psoriatic epidermis were measured by using one-dimensional SDS-PAGE, followed by scanning densitometry. Values obtained were compared with results for non-lesional epidermis and from epidermis from normal individuals. Patients on four different treatment regimens were investigated by repeated sampling over 3-4 months starting before therapy commenced. The levels of four keratins changed significantly: keratins I (70 kd) and 2 (66 kd) tended to rise to normal levels, while keratins 16 (50 kd) and 18 (44 kd) fell to normal levels. There were differential effects as well as differences in the rates of normalization depending upon the treatment regimen. The most rapid normalization of the levels of all four keratins was observed with topical dithranol (anthralin) treatment (five patients) with plaque resolution and keratin level normalization after 7-9 weeks. Oral hydroxyurea (three patients) had similar effects, but over a longer time scale (20 weeks). In contrast, oral etretinate (four patients) caused a normalization of all except keratin 2 (66 kd) over a period of 20-28 weeks, and keratin I (70 kd) levels tended to 'overshoot' the normal level. PUVA (five patients) caused rapid normalization (in 9-12 weeks) of keratins 2 (66 kd) and 18 (44 kd), but had much weaker effects on keratins I (70 kd) and 10 (57 kd). These results suggest that resolution of lesions as judged by clinical criteria can occur without normalization of the keratin electrophoretic profile. Possibly the most reliable marker of clinical resolution was the reduction in keratin 16 (50 kd), since treatment effects on the differentiation of keratins I (70 kd) and 2 (66 kd) were different.

Epidermal keratin levels during oral 1-alpha-hydroxyvitamin D3 treatment for psoriasis

Recently the treatment of psoriasis with vitamin D3, its metabolites or analogues, has been reported to be clinically effective and free from side effects. We have quantified the changes in the levels of epidermal lesional keratins in 15 psoriatic patients receiving oral 1 alpha(OH)D3 treatment. Lesions were sampled before treatment commenced and at monthly intervals for 4-6 months. Clinical resolution occurred in 7 patients within this time; 3 other patients showed incomplete lesion resolution and the remaining 5 patients showed a complete lack of response within the treatment period. Lesion resolution, as judged by clinical criteria, was accompanied by significant changes in the levels of three of the keratin polypeptides and smaller changes in others. Keratin 2 increased to levels greater than those in normal epidermis, while keratins 16 and 18 decreased to normal levels. Changes in the levels of keratins 1 and 5 were small and those of keratins 7, 10 and 14 minimal. These changes were compared with values found during lesion resolution with other therapies used in psoriasis, i.e. topical dithranol, PUVA, oral etretinate and hydroxyurea and were highly reminiscent of those observed during PUVA therapy but contrasted with those during etretinate treatment. The decrease in level of keratin 16, a hyperproliferation marker, suggests that 1 alpha(OH)D3 inhibits keratinocyte proliferation, but at the same time the overproduction of keratin 2, a major keratin of the granular cells, indicates that there is an increase in the number of cells in the later stages of differentiation.

IgG subclasses in acne vulgaris

IgG subclasses were measured in male patients with very low grade or severe acne. No IgG subclass deficiencies were found. Patients with severe acne had a significant increase in total IgG attributable to their exposure to antigens which stimulate the production of antibodies in the IgG2 and IgG3 subclasses.

Age incidence of antibodies to normal human epidermis

Antibodies reactive with various layers of normal human epidermis can be detected in a high percentage of sera from normal adults. Stimulation to produce these antibodies occurs at a very early age, with some suggestion that in utero stimulation may occur in a small number of cases.

Inflammatory responses in acne patients treated with 13-cis-retinoic acid (isotretinoin)

Twelve patients with acne vulgaris treated with isotretinoin for 4 months showed increased levels of immunoglobulins and helper T cells at 8 weeks and increased levels of B cells at 16 weeks.

Lymphocyte subpopulations in patients with acne vulgaris

T- and B-lymphocyte subpopulations were measured in the peripheral blood of patients with varying severity of acne and in acne-free control subjects. Increased severity of acne correlated with an increased number of T lymphocytes, helper T cells and B cells, while the number of suppressor T cells remained normal and did not alter significantly. This evidence suggests that there is no lack of regulation of the immune response in acne patients.