Skin Of Female Mice Research Articles

Arsenic Impairs Wound Healing Processes in Dermal Fibroblasts and Mice.

Inorganic arsenic (NaAsO2) is a naturally occurring metalloid found in water resources globally and in the United States at concentrations exceeding the U.S. Environmental Protection Agency Maximum Contamination Level of 10 ppb. While exposure to arsenic has been linked to cancer, cardiovascular disease, and skin lesions, the impact of arsenic exposure on wound healing is not fully understood. Cultured dermal fibroblasts exposed to NaAsO2 displayed reduced migration (scratch closure), proliferation, and viability with a lowest observable effect level (LOEL) of 10 µM NaAsO2 following 24 h exposure. An enrichment of Matrix Metalloproteinase 1 (MMP1) transcripts was observed at a LOEL of 1 µM NaAsO2 and 24 h exposure. In vivo, C57BL/6 mice were exposed to 10 µM NaAsO2 in their drinking water for eight weeks, then subjected to two full thickness dorsal wounds. Wounds were evaluated for closure after 6 days. Female mice displayed a significant reduction in wound closure and higher erythema levels, while males showed no effects. Gene expression analysis from skin excised from the wound site revealed significant enrichment in Arsenic 3-Methyltransferase (As3mt) and Estrogen Receptor 2 (Esr2) mRNA in the skin of female mice. These results indicate that arsenic at environmentally relevant concentrations may negatively impact wound healing processes in a sex-specific manner.

Role of Momordica charantia in preventing the natural aging process of skin and sexual organs in mice.

Although various methods for improving the natural aging of skin have been examined, an effective method is currently unavailable. Therefore, in this study, we investigated the effects of Momordica charantia on the natural aging of skin of mice and how sex differences influenced these effects. To this end, we bred female and male hairless mice without ultraviolet ray irradiation and physical stress for 2 years. During the study period, mice were orally administered 50 mg/kg/day Momordica charantia fruit extract, three times per week. The characteristics of naturally aging skin, in terms of moisture retention, hydration, thickness, and reduced wrinkle score, improved after Momordica charantia treatment in both male and female mice. Furthermore, reduced cell apoptosis was observed in the female ovaries and male testes, and the levels of testosterone and 17β-estradiol in blood were maintained. After treatment with Momordica charantia, the expression of matrix metalloprotease (MMP)-1 and hyaluronidase (HAYL)2 decreased in the skin of female mice, whereas the serum levels of interleukin (IL)-33 increased in the male mice. These results indicated that the natural aging of the skin was decelerated by Momordica charantia via regulation of the 17β-estradiol/mast cell/MMP-1/HAYL2 and testosterone/mast cell/IL-33 signaling pathways in female and male mice, respectively.

Beta-caryophyllene enhances wound healing through multiple routes.

Beta-caryophyllene is an odoriferous bicyclic sesquiterpene found in various herbs and spices. Recently, it was found that beta-caryophyllene is a ligand of the cannabinoid receptor 2 (CB2). Activation of CB2 will decrease pain, a major signal for inflammatory responses. We hypothesized that beta-caryophyllene can affect wound healing by decreasing inflammation. Here we show that cutaneous wounds of mice treated with beta-caryophyllene had enhanced re-epithelialization. The treated tissue showed increased cell proliferation and cells treated with beta-caryophyllene showed enhanced cell migration, suggesting that the higher re-epithelialization is due to enhanced cell proliferation and cell migration. The treated tissues also had up-regulated gene expression for hair follicle bulge stem cells. Olfactory receptors were not involved in the enhanced wound healing. Transient Receptor Potential channel genes were up-regulated in the injured skin exposed to beta-caryophyllene. Interestingly, there were sex differences in the impact of beta- caryophyllene as only the injured skin of female mice had enhanced re-epithelialization after exposure to beta-caryophyllene. Our study suggests that chemical compounds included in essential oils have the capability to improve wound healing, an effect generated by synergetic impacts of multiple pathways.

Isolation of Mouse Epidermal Keratinocytes and Their In Vitro Clonogenic Culture.

The protocol described here is a reliable method of harvesting primary keratinocytes from adult female mice (54 ± 2 days old) yielding approximately 30 x 106 viable cells per mouse. Primary adult mouse keratinocytes are harvested from the dorsal skin of female mice. Male mice (~6 weeks old) can be used for keratinocyte harvesting depending on the requirements of the experiment. Euthanized mice are shaved and sterilized with serial washes in povidone iodine and ethanol solutions (70% alcohol). After disinfecting the mice, the dorsal skin is removed and the subcutaneous fat and muscle are removed with a scalpel and discarded. The skins are cut into small pieces and treated with a mild, low temperature trypsinization to detach the lower dermis from the epidermis. The scraped epidermises are stirred at low speed, filtered to remove the hairs, counted, and re-suspended in culture medium. This method provides an excellent single cell suspension of highly culturable cells for many downstream applications.

Evaluation of Skin Response After Erbium:Yttrium- Aluminum-Garnet Laser Irradiation: A Network Analysis Approach.

Introduction: Application of laser in medicine and cosmetic purposes has raised grossly in recent years. There are contradictory finding about its side effects. In this research critical differentially expressed proteins after irradiation erbium:yttrium-aluminum-garnet (Er:YAG) laser on skin are investigated. Methods: Proteome data including 31 proteins were obtained from a proteomics investigation of laser irradiation, Er:YAG on female mouse skin that are published by Pan et al. The query proteins and 100 related ones were included in the protein-protein interaction (PPI) network. The central nodes were determined and all of nodes were included in action maps. Expression, activation, inhibition, binding, and reaction were considered in action plan. Results: Numbers of 16 proteins were recognized by STRING database and were included in the network. Except PHRF1, the other 15 query proteins were included in the main connected component of the constructed network. Ten central nodes of the network and ten numbers of top query proteins based on degree value were identified as central proteins of the network. All nodes of the network analyzed via action maps and the important acted nodes were determined as RPSA, GAPDH, TPT1, DCTN2, HSPB1, and PDIA3. Conclusion: Two balanced processes including cancer promotion and cancer prevention were after irradiation were identified.

Infl uence of neurogenic chronic pain on indicators of kallikreinkinin system in skin of female mice in dynamics of В16/F10 melanoma development

Objective: determination of levels of the kallikrein-kinin system (KKS) indicators in cutaneous melanoma and in the skin not associated with tumor in female mice with chronic neurogenic pain in the dynamics of В16/F10 melanoma growth. Materials and methods: the study included 8 weeks old female С57ВL/6 mice weighing 24-26 g (n=132). Th e animals were divided into 4 groups: 64 – В16/F10 melanoma with chronic neurogenic pain (main group), 22 – chronic neurogenic pain without melanoma, 27 – В16/F10 melanoma only (comparison group), 19 – intact mice. KKS parameters were determined by ELISA. Statistical processing of results was performing using the Statistica 10 program and the Wilcoxon test. Results: chronic pain infl uenced the development of transplantable В16/F10 melanoma: tumors in animals of the main group appeared 1 week aft er the transplantation and were bifocal; 100% metastasis to the liver, lungs and to non-typical sites (the heart and uterus). Tumors in mice of the comparison group appeared in 2 weeks, and metastases in 4 weeks. Th e mean survival was 19.17±1.35 days in the main group and 30.25±1.67 days in the comparison group. In the skin of mice of the main group, we observed progressive kininogen consumption, KLK-1 depletion from the second week of the tumor growth, and its accumulation in the tumor with its maximum by the end of week 3. KLK-14 signifi cantly increased in the skin; in the tumor it stabilized aft er an increase in week 1. KKS parameters diff ered signifi cantly in the skin and tumor tissues of mice in compared groups. Conclusions : Chronic neurogenic pain causes a radical reorganization of KKS metabolism in the skin of intact mice: an increase in kininogen and prekallikrein and a decrease in KLK-1. B16/F10 melanoma transplantation with chronic neurogenic pain preserves the increase of prekallikrein in the skin, but increases as well its consumption in tumor tissue simultaneously with the activation of KLK-1 (in the skin until its exhaustion) and KLK-14.

Androgens Attenuate Vitamin D Production Induced by UVB Irradiation of the Skin of Male Mice by an Enzymatic Mechanism

Cutaneous exposure to UVB irradiation is an important source of vitamin D. Here, we examined sex-specific differences in cutaneous vitamin D production in mice. Both male and female mice on a vitamin D-deficient diet manifested vitamin D deficiency, with mineral abnormalities, secondary hyperparathyroidism, and osteomalacia. UVB irradiation significantly increased vitamin D levels in the skin of female mice and normalized serum 25-hydroxyvitamin D3 and 1,25-dihydroxyvitamin D3 levels, as well as mineral and skeletal abnormalities. However, in male mice, the vitamin D response to UVB was attenuated and mineral and skeletal abnormalities were not normalized. The vitamin D precursor, 7-dehydrocholesterol (7DHC), was significantly lower in the skin of male than female mice. This reduction was due to local androgen action in the skin as demonstrated by castration studies and skin-specific androgen receptor deletion in male mice, both of which reversed the male phenotype. Local androgen regulation in the skin of the CYP11A1 gene, which encodes a crucial enzyme that metabolizes cholesterol, 7DHC, and vitamin D, appeared to contribute to the gender differences in UVB-induced vitamin D production and to its reversal of vitamin D deficiency. Sex-specific, enzymatically regulated differences in cutaneous production of vitamin D may therefore be of importance to ensure vitamin D sufficiency.

Danggui buxue tang inhibits 2,4-dinitrochlorobenzene: induced atopic dermatitis in mice.

Danggui Buxue Tang (DBT) is a herbal decoction that has been used in Chinese medicine to enhance qi and blood circulation. Previously, we found that DBT can suppress allergy-related asthma in mice, leading us to hypothesize that DBT might ameliorate allergy disease. In this study, we evaluated whether DBT can attenuate atopic dermatitis (AD) symptoms and have an anti-inflammatory effect on AD-like mice. The dorsal skin of female mice was shaved and sensitized cutaneously (skin smear) with 1-chloro-2,4-dinitrobenzene. Mice were then given various doses of DBT from days 14 to 29 cutaneously. DBT treatment suppressed ear swelling and skin inflammation and decreased mast cell and eosinophil infiltration into skin and ear tissue. DBT also inhibited levels of IgE and Th2-associated cytokine levels in serum. These results demonstrate that cutaneous administration of DBT reduced the development of AD-like skin lesions in mice.

Abstract 4954: Hematogenous metastasis of ovarian cancer: Re-thinking mode of spread

Abstract Background: Most patients with ovarian cancer have widely metastatic disease within the abdominal cavity at primary diagnosis; historically, this was thought to occur via intraperitoneal “seeding”. Here, we report unexpected findings related to hematogenous ovarian cancer metastasis with a strong tropism for the omentum. Methods: We established a novel parabiosis model where the skin of female mice was fused surgically from the shoulder to the hip joint. Two weeks later, the “host” parabiont mice were injected with tumor cells into ovary. Once the host mice became moribund, the parabionts were separated, and the host mice were euthanized. Tumor development and patterns of metastasis were analyzed in the host mice. A series of additional in vitro and in vivo experiments were carried out to decipher the underlying mechanisms. Results: The parabiosis models demonstrated that tumor cells injected into the ovary of each “host” mouse metastasized to the corresponding “guest” mouse, predominantly to the omentum. Using high-throughput transcriptome analysis and phospho-proteome arrays, we demonstrated that ErbB3, an EGFR family receptor tyrosine kinase (RTK) was highly expressed in the ovarian cancer cells that hematogenously metastasized to the omentum (SKOV3-OM3) compared to parental cells. The ErbB3-NRG1 axis activated Src/PI3K/AKT signaling pathway, which in turn induced loss of polarity and increased invasion of ovarian cancer cells. Depletion of murine NRG1 using target specific siRNAs almost completely abolished omental metastasis. In contrast, overexpression of ErbB3 resulted in enhanced tumor formation and omental metastatic spread, which confirms the role of ErbB3 in hematogenous omental metastasis. Additional studies with a function-blocking antibody specific to ErbB3 led to substantial reduction in hematogenous metastasis of ovarian cancer cells. Conclusions: Collectively, our results provide the first evidence that ovarian cancer cells are capable of hematogenous metastasis, but with strong tropism for the omentum. These findings not only provide a new understanding of ovarian cancer metastasis, but also identify novel therapeutic targets. Citation Format: Sunila Pradeep, Seung Wook Kim, Sherry Wu, Nishimuara Masato, Takahito Miyake, Choi Hyun-Jin, Rajesha Rupaimoole, Jinsong Liu, Isahai Fidler, Gabriel Lopez, Anil Sood. Hematogenous metastasis of ovarian cancer: Re-thinking mode of spread. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4954. doi:10.1158/1538-7445.AM2014-4954

INFLUENCE OF MORACIN ON DMBA-TPA INDUCED SKIN TUMERIGENESIS IN THE MOUSE

The efforts in the study were conducted to assess the protective influence of Moracin, the major constituent of leaves of mulberry, Morus alba (L) on tumor promotion in 7, 12 – dimethylbenz (alpha) anthracene (DMBA) – initiated and 12-O-tetradecanoylphorbol 13-acetate (TPA) – promoted mouse skin tumerigenesis model. The acetone solution of Moracin was topically applied to DMBA – initiated female mouse skin at the dosage of 2.5 and 5 mg twice per week for sixteen weeks, thirty minutes prior to each promotion treatment with TPA in the first experimental schedule. The significant reduction in tumor incidence and tumor multiplicity effects were evident in the treated group. The expression of tumor necrosis factor (TNF) – alpha protein and the level of 4-hydroxynoneal (4HNE) in the normal epidermis were significantly reduced in both moracin treated groups. Moracin at the dosage of 5 mg was topically applied to the dorsal surface of mouse skin 30 minutes before application of a TPA in the second effort in the study. And the same dosages of TPA and Moracin were applied twice at the interval of 24 hours. Moracin treatment was found inhibiting the double TPA treatment – induced morphological changes reflecting inflammatory response, including leucocyte infiltration, hyperplasia and cell proliferation. Moracin treatment, furthermore significantly suppressed the elevation in 4-HNE level and elevated expression of c-fos, c-myc and cycloxygenase-2 (COX-2) in normal epidermis induced by double application of TPA. The moracin was found protective influence in tumor promotion. Utilization of Moracin may open a new avenue in the treatment of tumerigenesis.

Use of Moracin in preventing the cancer

Efforts in the study were conducted to assess the protective influence of Moracin, the major constituent of leaves of mulberry, Morusalba (L) on tumor promotion in 7, 12 - dimethylbenz( alpha ) anthracene (DMBA) - initiated and 12-O-tetradecanoylphorbol 13-acetate ( TPA ) - promoted mouse skin tumerigenesis model. The acetone solution of Moracin was topically applied to DMBA - initiated female mouse skin at the dosage of 2.5 and 5 mg twice per week for sixteen weeks, thirty minutes prior to each promotion treatment with TPA in the first experimental schedule. The significant reduction in tumor incidence and tumor multiplicity effects were evident in the treated group. The expression of tumor necrosis factor ( TNF ) - alpha protein and the level of 4-hydroxynoneal ( 4HNE) in the normal epidermis were significantly reduced in both moracin treated groups. Moracin at the dosage of 5 mg was topically applied to the dorsal surface of mouse skin 30 minutes before application of a TPA in the second effort in the study. And the same dosages of TPA and Moracin were applied twice at the interval of 24 hours. Moracin treatment was found inhibiting the double TPA treatment - induced morphological changes reflecting inflammatory response, including leucocyte infiltration, hyperplasia and cell proliferation. Moracintreatment, furthermore significantly suppressed the elevation in 4- HNE level and elevated expression of c-fos, c-myc and cycloxygenase-2 (COX-2) in normal epidermis induced by double application of TPA. The moracin was found protective influence in tumor promotion. Efficient utilization of Moracin may open a new avenue in the treatment of skin cancer.

Estrogen Deficiency and Tobacco Smoke Exposure Promote Matrix Metalloproteinase-13 Activation in Skin of Aging B6 Mice

Estrogen deficiency may contribute to extracellular matrix turnover in skin. This has led previous authors to postulate that aged skin heals less efficiently when compared to younger skin. Also, cigarette smokers have been shown to heal less efficiently than nonsmokers. Matrix metalloproteinase (MMP)-13, an enzyme that participates in the degradation of the extracellular matrix, has been implicated in physiologic aging and wound healing. This study investigates the effects of smoke exposure and estrogen deficiency on MMP-13 in young and aged female mouse skin. Young and aged female C57Bl/6J mice were ovariectomized. They were then randomly administered either 17beta-estradiol (E2) or placebo pellets. Half the animals in each age group were further randomized to exposure to cigarette smoke for a period of 6 months. Smoking and estrogen deficiency increased MMP-13 protein and activity in aged skin. The tissue inhibitors of metalloproteinases, which inhibit MMPs, activity was unchanged across all groups. E2 replacement decreased the actual level of MMP-13 protein and activity. We also found an increased collagen content and decreased ER receptor protein level in aged, smoke-exposed female mice. Our experimental data show that tobacco smoke exposure and estrogen deficiency are additive risk factors for promoting increased activity of MMP-13 in aged skin. These findings suggest that MMP-13 functions as a mediator of smoke-induced skin injury in susceptible, aged experimental female mice.

A Role for the Androgen Receptor in Collagen Content of the Skin

Collagen, the major macromolecular component of skin, is responsible for maintaining the structural integrity of the tissue as well as for providing important functional characteristics, such as pliability and thickness. We have been studying the structure and regulation of collagen in mouse mutations affecting the skin. In the course of these studies, we found that there are significant differences in collagen content between the skin of wild-type male and female mice, which become evident at puberty. Furthermore, male mice with an X-linked mutation in the androgen receptor gene (formerly called testicular feminization and abbreviated as Ar(Tfm)) showed decreased levels of collagen, indicating that the androgen receptor pathway contributes to the observed differences. These findings demonstrate that there are striking differences in the collagen content of skin between male and female mice, and provide a biochemical explanation for these differences.

Scd3—A Novel Gene of the Stearoyl-CoA Desaturase Family with Restricted Expression in Skin

Stearoyl-coenzyme A (CoA) desaturase (SCD) is a key enzyme involved in the conversion of saturated fatty acids into monounsaturated fatty acids. Previously, two members of this gene family, namely, Scd1 and Scd2, have been reported. Here we report the identification and characterization of a novel member of this family, Scd3, whose expression is restricted to mouse skin, specifically to the sebaceous gland. The Scd3 gene codes for a transcript of ∼4.9 kb with an open reading frame that results in a 359-amino-acid protein. Scd3 shares 91 and 88% identity in the protein-coding region with Scd1 and Scd2, respectively, and maps to mouse chromosome 19 in very close proximity to Scd1 and Scd2. Unlike Scd1, Scd3 expression is higher in male mouse skin than in female mouse skin. The promoter sequence of Scd3 reveals similarity with Scd1 in the proximal region but also possesses several distinctive features including the polyunsaturated fatty acid-response element. Scd3 is expressed in the skin of young asebia mutant mice (Scd1ab2J/Scd1ab2J) in the absence of Scd1. Scd3 expression changes during the mouse hair cycle but not as dramatically as Scd1. The tissue-specific and sex-dependent expression of Scd3 suggests the presence of gene- and hormonal-specific control mechanisms.

Diameter distributions of collagenous tissues in relation to sex. A quantitative ultrastructural study

A number of factors have been implicated in the regulation of collagen fibril diameter. Electron microscopy analysis was used to investigate the role of sex on fibril diameter. Female mouse skin collagen fibrils’ mean diameter values were significantly smaller than those from the male, independent of age. In addition, the female rabbit collagen fibrils had a marked decrease in the mean diameter compared to male, in all the tissues examined (skin, liver, and bone). These data suggest that the collagen fibril diameter is related to sex.

Benzo[a]pyrene carcinogenicity is lost in mice lacking the aryl hydrocarbon receptor.

The contribution of the aryl hydrocarbon receptor (AhR) in induction of a battery of xenobiotic-metabolizing enzymes has been studied extensively. However, no direct proof has been obtained that it plays a role in modulating carcinogenesis. To address the question of whether AhR is required for tumor induction, we have investigated the response of AhR-deficient mice to benzo[a]pyrene (B[a]P), a widely distributed environmental carcinogen. B[a]P treatment induced expression of the cytochrome P450 gene Cyp1a1 in the skin and liver of AhR-positive mice bearing +/+ and +/- genotypes and did not induce expression of the cytochrome P450 gene Cyp1a1 in AhR-null mice in either skin or liver. In contrast, Cyp1a2 gene expression was positive in liver irrespective of the presence or absence of the AhR gene, or B[a]P treatment, although its inducibility was lost in the AhR(-/-) mouse. All AhR-positive male mice of both +/+ and +/- genotypes that received subcutaneous injection of B[a]P (2 mg) on the first and the eighth days had developed subcutaneous tumors at the site of injection at the end of the 18-week experiment. In contrast, no tumors were apparent in any of the AhR-deficient mice. Likewise, topical application of B[a]P (200 microg) at weekly intervals to the skin of female mice for 25 weeks produced skin tumors only in the AhR-positive mice. Thus the carcinogenic action of B[a]P may be determined primarily by AhR, a transcriptional regulator of the gene for CYP1A1. The results of the present study provide direct evidence that AhR is involved in carcinogenesis.

Effects of 17-beta-estradiol and ICI 182 780 on hair growth in various strains of mice.

17-beta-Estradiol (10 nmol per 200 microl acetone) applied topically twice weekly to the clipped dorsal surface of C57BL/6 or C3H female mouse skin prevented hair growth, as previously described in the CD-1 mouse strain. Twice weekly topical application of the estrogen receptor antagonist, ICI 182 780 (10nmol per 200microl acetone), induced the telogenanagen transition and produced early pigmentation appearance in skin and hair growth in C57BL/6 and C3H female mice. Whereas twice weekly topical application of 10nmol 17-beta-estradiol blocked hair growth, the intraperitoneal administration of this dose twice weekly did not block hair growth, suggesting a direct cutaneous effect of 17-beta-estradiol. We also evaluated the effect of 17-alpha-estradiol, 17-beta-estradiol, and ICI 182 780 on hair growth in male mice. As observed in female mice, 17-beta-estradiol was a potent inhibitor of hair growth and ICI 182 780 stimulated hair growth; however, unlike the results previously observed in female mice, 17-alpha-estradiol was a potent inhibitor of hair growth in male mice. These results demonstrate that (i) the route of administration of 17-beta-estradiol is critical for its ability to block hair growth; (ii) C57BL/6 and C3H mice, two commonly employed mouse strains for hair growth studies, responded to 17-beta-estradiol and ICI 182 780 in a manner similar to that described in CD-1 mice; and (iii) the hair follicles of male and female mice respond similarly to 17-beta-estradiol and ICI 182 780, but display striking sex differences in the response to 17-alpha-estradiol on hair growth.

An Analysis of the Epidermal Hyperplasia Produced by Acetic Acid, a Weak Tumor Promoter, in the Skin of Female Mice Initiated with Dimethylbenzanthracene

Epidermal tumor promoters like TPA (12-0-tetrade-canoyl-phorbol-13-acetate) produce an epidermal hyperplasia which is a major transformation step in tumor promotion. Acetic acid, an agent that produces an epidermal hyperplasia, has, however, been reported to be a weak promoter of tumorigenesis in mouse skin. The purpose of this investigation was to analyze the epidermal hyperplasia produced by acetic acid in order to help understand why acetic acid is a weak tumor promoter. Epidermal hyperplastic growth produced by TPA in initiated mouse skin is characterized by the appearance of an initial small transient hyperplasia followed by the principal hyperplasia. The application of 667 μmol acetic acid on the skin of mice initiated with 200 nmol dime-thylbenzanthracene does not result in a transient epidermal hyperplasia. Instead, the numbers of nucleated cell layers and the numbers of basal and suprabasal cells/mm interfollicular epidermis begin to decrease within 5 h. The epidermis then begins to lose its stainability with hematoxylin and eosin and by 19 h only faint nuclear outlines are seen. These conditions prevail until about day 2 when epidermal cells again stain. In addition, the epidermis becomes hyperplastic. The principal epidermal hyperplasia produced by TPA results in a 4-fold increase in epidermal wet weight and total protein and a 2-fold increase in total DNA. In contrast, after the application of 667 μmol acetic acid to initiated skin, the maximal increase in wet weight and protein is about 2 times that of normal, and the increase in DNA is only 50% above normal. The RNA content of TPA-induced hyperplastic epidermis reaches a maximum of about 2 times that of normal. In contrast, the RNA content of acetic acid-induced hyperplastic epidermis is actually reduced to 70% below normal levels, making it only 35% of the TPA-induced level. This is consistent with the fact that the cells of TPA-induced hyperplastic epidermis are enlarged and intensely basophilic, whereas the cells in acetic acid-induced hyperplastic epidermis tend to show little enlargement and cytoplasmic basophilia. Maximal mitotic activity in the TPA-induced hyperplastic epidermis is 14 times that of normal, whereas that after acetic acid is only 7 times above normal. Multiple applications of TPA result in an increased epidermal wet weight from that seen after 1 application. In contrast, the application of 667 μmol acetic acid once weekly for 7, 12, and 20 weeks does not result in a further increase in epidermal wet weight from that seen after the first application. Indeed, by 20 weeks epidermal wet weight is slightly less than that seen after the first application, and accordingly the epidermis appears in histologic sections to be less hyperplastic. The evidence strongly suggests that one reason acetic acid is a weak promoter of epidermal tumorigenesis is that it does not produce the degree of epidermal hyperplasia that TPA does and the hyperplasia that is produced is barely maintined, if at all, during chronic treatment.

Tumor Promotion by Abrasion Induced Epidermal Hyperplasia in the Skin of Mice

Regenerative epidermal hyperplasia produced by repeated abrasion every 21 days of the skin of female mice after initiation with 7, 12-dimethylbenz(a)anthracene results in the appearance of epidermal tumors. Full thickness wounds, approximately 2 cm in length, made every 14 days in mouse skin initiated with 7, 12-dimethylbenz(a)anthracene also results in the appearance of epidermal tumors adjacent to the wound edge. Repeated abrasion or wounding of normal female mouse skin does not result in the appearance of epidermal tumors. Repeated plucking of initiated mouse skin, which produces a milder epidermal hyperplasia than abrasion, does not result in the appearance of tumors. The data demonstrate that regenerative epidermal hyperplasia, of a sufficient intensity, can act as a tumor promoter.

Ribosome Fractions from Normal and Methylcholanthrene-Treated Mouse Epidermis

Ribosome fractions were isolated from normal, trypsinized epidermis of CD-1 female mouse skin. About 83%, of the ribosomes are free, and approximately 17% are membrane-bound. Almost all the ribosomes are found in the post-mitochondrial supernatant fraction. Epidermis 4 days after treatment with 3-methylcholanthrene shows a marked proportionate increase in both free and membrane-bound ribosomes. Again almost all the ribosomes are in the post-mitochondrial supernatant fraction.