DNA甲基转移酶与CD11a基因在SLE患者中的表达

目的 探讨DNA甲基转移酶(DNMT)的表达异常在SLE发病中的作用.方法 以半定量RT-PCR方法检测了SLE缓解期、活动期及正常人外周血单核细胞(PBMC)中DNMT及CD11a基因表达水平,并进行相关性分析.结果 SLE缓解期患者PBMC中DNMT1的表达水平显著低于正常人对照组(t=5.90,P<0.0001);活动期的表达水平也显著低于对照组(t=2.26,P=0.0001);缓解期与活动期比较差异无统计学意义(t=1.75,P=0.089).SLE缓解期、活动期及对照组PBMC中DNMT3A的表达水平差异无统计学意义,DNMT3B的表达水平极低.SLE缓解期PBMC中CD11a表达水平明显高于对照组(t=5.35,P<0.0001);活动期的表达水平显著高于缓解期(t=2.99,P=0.006)和正常人对照组(t=6.57,P<0.0001).DNMT1的降低与SLE疾病活动指数(SLEDAI)间无显著相关性(r=-0.34,P>0.05),CD11a的升高与SLEDAI间呈显著正相关(r=0.48,P<0.05),DNMT1与CD11a间无显著相关性(r=-0.18,P>0.05).结论 DNMT1表达水平降低在SLE的发病中可能起作用.但不是决定DNA甲基化状态的惟一因素.     

低氧对系统性硬化病患者皮肤成纤维细胞胶原蛋白合成的影响

目的 研究低氧对系统性硬化病(SSc)患者和正常人皮肤成纤维细胞胶原蛋白合成及胶原基因表达的影响。方法 分别以5例SSc患者和5例正常人皮肤成纤维细胞系作为实验对象。将成纤维细胞分别放入20%正常氧和2%低氧分压环境中培养,用分光光度仪测定细胞培养基上清液中羟脯氨酸含量,并折算成胶原蛋白含量。用Trizol提取细胞总RNA,用RT-PCR方法测定其中Ⅰ型和Ⅲ型前胶原mRNA的表达。结果 培养至第6天,低氧分压条件下,SSc患者皮肤成纤维细胞培养基中胶原蛋白含量比正常氧分压条件下显著增加(t=3.97,P=0.0041);正常人皮肤成纤维细胞培养基中胶原蛋白含量此时也显著增加(t=2.63,P=0.0302)。培养至第3天,低氧分压条件下,SSc成纤维细胞Ⅰ型和Ⅲ型前胶原mRNA表达量比正常氧分压条件下均有显著增加(Ⅰ型:t=5.81,P=0.0004;Ⅲ型:t=6.44,P=0.0002);正常人皮肤成纤维细胞此时的Ⅰ型和Ⅲ型前胶原mRNA表达量与SSc患者相似,低氧分压条件下比正常氧分压条件下均有显著增加(Ⅰ型:t=4.40,P=0.0023;Ⅲ型:t=2.24,P=0.0453)。结论 低氧状态下,SSc患者和正常人皮肤成纤维细胞胶原蛋白合成均有增加,Ⅰ型和Ⅲ型前胶原mRNA表达也均增加.低氧可能是皮肤硬化的一个相关因素。     

二期梅毒患者外周血淋巴细胞凋亡及其Fas、Bcl-2表达的研究

目的 检测二期梅毒患者外周血淋巴细胞(PBLC)凋亡及其Fas、Bcl-2的表达,探讨二期梅毒患者免疫功能异常与淋巴细胞凋亡的关系。方法 采用流式细胞仪检测33例二期梅毒患者和30例正常人PBLC细胞凋亡及其Fas、Bcl-2的表达。结果 梅毒患者PBLC及CD4⁺细胞Fas表达明显高于对照组(P<0.01),而Bcl-2表达明显低于对照组(P<0.01)。CD8⁺、CD19⁺细胞Fas、Bcl-2表达两组比较差异无统计学意义(P>0.05)。梅毒患者PBLC及CD4⁺细胞凋亡率显著高于对照组(P<0.01),CD8⁺及CD19⁺细胞凋亡率两组比较差异无统计学意义(P>0.05)。梅毒患者PBLC及CD4⁺细胞凋亡率分别与其Fas表达呈显著正相关(r=0.68,P<0.01;r=0.71,P<0.01),但与Bcl-2表达呈显著负相关(r=-0.82,P<0.01;r=-0.74,P<0.01)。结论 二期梅毒患者细胞免疫功能异常可能与淋巴细胞凋亡过度有关,而淋巴细胞凋亡过度与Fas、Bcl-2表达异常有关。     

大疱性类天疱疮患者黏膜受累与糖皮质激素控制量的相关性

目的 探讨大疱性类天疱疮(bullous pemphigoid,BP)患者黏膜受累与糖皮质激素控制量的相关性。方法 对1988-2002年103例BP住院患者平均糖皮质激素起始控制量、皮损全部消退时间和糖皮质激素开始减量时间进行回顾性研究,按照患者入院时皮损累及部位分为黏膜受累组和无黏膜受累组。结果 103例患者,黏膜受累组37例占35.9%,无黏膜受累组66例占64.1%,黏膜受累组控制病情所需的糖皮质激素量高于无黏膜受累组(t=3.49,P<0.001),两组患者皮损全部消退时间和糖皮质激素首次减量时间差异无显著性(t=0.82和t=0.41,P>0.05)。结论 BP黏膜损害与糖皮质激素控制量相关。     

斑块状银屑病表皮干扰素-γ受体mRNA表达的研究

目的 探讨斑块状银屑病患者表皮干扰素-γ受体mRNA的表达及其在发病机制中的作用.方法 采集28例斑块状银屑病患者皮损及周围外观正常皮肤,28例正常人皮肤作为对照,分离表皮,逆转录聚合酶链反应(RT-PCR)法检测干扰素-γ受体mRNA表达水平.PASI评分法评估银屑病的严重程度.结果 斑块状银屑病患者皮损和非皮损表皮干扰素-γ受体mRNA的表达率为100%,对照样本的表达率为17.86%(5/28);患者皮损、非皮损和对照表皮干扰素-γ受体mRNA的表达水平均值分别为1.002±0.563、0.188±0.095、0.005±0.012,皮损处的表达水平明显高于非皮损处(t=7.54,P<0.01),非皮损处明显高于正常人对照;进行期与稳定期皮损的表达水平分别为1.210±0.489和0.379±0.163,进行期显著高于稳定期(t=4.37,P<0.01);而皮损处的表达水平与PASI评分值无相关性.结论 表皮干扰素-γ受体mRNA的表达可能与银屑病皮损的形成和病情的活动性有关.     

梅毒患者病程中宿主的免疫学变化

目的 探讨梅毒螺旋体(TP)感染的不同病程与宿主免疫学变化的关系。方法 采用ELISA法分别检测一期和二期梅毒患者血清抗TP抗体的滴度(用活动指数AI表示)。MTT比色法测定一期和二期梅毒患者血清对脐带血淋巴细胞增殖反应的影响(用刺激指数SI表示)。ABC-ELLSA法分别检测一期和二期梅毒患者血清中细胞因子IL-2、IL-4含量。结果 二期梅毒患者抗TP抗体的活动指数(AI)显著高于一期梅毒(t=3.92,P<0.01)。一期和二期梅毒血清对脐带血淋巴细胞增殖反应的刺激指数SI显著低于无血清含PHA组(q₁=12.99,P₁<0.01。q₂=12.04,P₂<0.01),且二期梅毒血清SI亦显著低于一期梅毒(q=7.18,P<0.01)。一期梅毒血清中IL-2含量明显高于二期梅毒(t=3.50,P<0.05),IL-4含量与二期梅毒差异无显著性(t=1.31,P>0.05)。结论 抗TP抗体随着梅毒病程由一期向二期进展其滴度越来越高,但与体液免疫有关的细胞因子IL-4没有发生显著性变化;宿主感染梅毒螺旋体后,其细胞免疫功能受到明显抑制,且随着病程由一期向二期进展,其抑制现象越来越显著。     

可诱导共刺激分子在系统性红斑狼疮患者外周血T淋巴细胞的表达

目的 探讨可诱导共刺激分子(ICOS)在系统性红斑狼疮(SLE)患者外周血T淋巴细胞的表达。方法 应用双色荧光抗体染色技术经流式细胞仪检测了33例SLE患者和16例正常人对照者外周血中T淋巴细胞表面ICOS的自然表达水平,同时收集SLE患者的实验室检查指标,并用SLE疾病活动指数(SLEDAI)来判定SLE患者疾病活动程度,比较分析不同组别SLE患者ICOS表达水平与SLEDAI的相关性。结果 活动期SLE组T淋巴细胞ICOS表达水平明显高于正常人对照组(P<0.01)和非活动期SLE组(P<0.01),非活动期SLE组与正常人对照组T淋巴细胞ICOS表达水平则差异无统计学意义(P>0.05)。活动期组与非活动期组SLE患者T淋巴细胞ICOS表达水平均与SLEDAI呈显著正相关(r=0.71,P=0.001、r=0.56,P=0.03)。结论 活动期SLE患者T淋巴细胞ICOS表达增高,ICOS可能与SLE的发病机制有关。     

银屑病患者外周血肝细胞生长因子和粒细胞-巨噬细胞集落刺激因子水平改变

目的 探讨肝细胞生长因子(HGF)和粒细胞-巨噬细胞集落刺激因子(GM-CSF)与银屑病的关系。方法 采用双抗体夹心酶联免疫吸附试验(ELISA)检测寻常性银屑病患者和正常人血清中HGF和GM-CSF水平。结果 进行期寻常性银屑病患者血清中HGF水平明显高于静止期及正常人对照(P<0.01),而静止期患者血清中HGF水平与正常人对照比较差异无统计学意义(P>0.05);进行期银屑病患者血清中GM-CSF水平明显高于正常人对照及静止期(P<0.01),静止期患者血清中GM-CSF水平亦高于正常人对照(P<0.05);进行期泛发性与局限性皮损患者之间血清HGF及GM-CSF水平差异均无统计学意义;患者血清HGF和GM-CSF水平与PASI计分均呈正相关(分别为r=0.38和r=0.30,P<0.002和P<0.02)。结论 寻常性银屑病患者外周血循环HGF和GM-CSF水平明显增高,HGF和GM-CSF可能参与银屑病发病。     

神经性皮炎皮损处神经纤维的数量及其与朗格汉斯细胞关系的研究

目的探讨神经性皮炎患者皮损处神经纤维的数量变化及其与朗格汉斯细胞接触的关系.方法用辣根过氧化物酶结合的链霉亲和素-生物素技术观察24例神经性皮炎患者皮损处神经纤维的表达及数量变化.用免疫荧光双标记及共聚焦激光扫描显微镜技术观察神经性皮炎患者皮损处神经纤维与朗格汉斯细胞接触数量关系.用实时定量PCR方法检测皮损处神经生长因子mRNA的表达情况.结果 神经性皮炎患者皮损处神经纤维长度显著增加,与皮损周边对照(t=6.90,P<0.001)及正常人对照(t=5.71,P<0.001)比较差异有统计学意义.皮损表皮内有神经纤维接触的朗格汉斯细胞占朗格汉斯细胞总数的百分数明显增多,与皮损周边对照(X²=43.91,P<0.001)及正常人对照(X²=46.11,P<0.001)比较差异有统计学意义.皮损处神经生长因子mRNA高表达,与皮损周边对照(t=3.25,P<0.01)及正常人对照(t=3.67,P<0.01)比较差异有统计学意义.结论 神经性皮炎患者皮损处存在高水平活性的NGF导致神经纤维增生.     

端粒酶活性与细胞凋亡在尖锐湿疣患者组织中的表达

目的 探讨尖锐湿疣(CA)皮损中端粒酶活性与细胞凋亡表达情况及其两者之间的相关性。方法 采用端粒重复序列扩增文件-酶标法(TRAP-ELISA)检测了30例尖锐湿疣患者皮损端粒酶活性,并与正常组织和肿瘤细胞株作对照;原位末端标记法(TUNEL)检测皮损中细胞凋亡。结果 27例(90%)尖锐湿疣皮损中端粒酶活性A₄₅₀值为0.50~2.76,平均1.302,明显高于正常皮肤组织,差异有显著性(t=6.12,P<0.01);24例皮损中有凋亡细胞,占80%,且端粒酶活性与凋亡指数呈显著负相关,r=-0.52,P=0.004。结论 端粒酶可以在一些非恶性皮肤病中表达,且影响细胞凋亡,可能参与CA发病。     

Autocrine regulation of re-epithelialization after wounding by chemokine receptors CCR1, CCR10, CXCR1, CXCR2, and CXCR3

This study identifies chemokine receptors involved in an autocrine regulation of re-epithelialization after skin tissue damage. We determined which receptors, from a panel of 13, are expressed in healthy human epidermis and which monospecific chemokine ligands, secreted by keratinocytes, were able to stimulate migration and proliferation. A reconstructed epidermis cryo(freeze)-wound model was used to assess chemokine secretion after wounding and the effect of pertussis toxin (chemokine receptor blocker) on re-epithelialization and differentiation. Chemokine receptors CCR1, CCR3, CCR4, CCR6, CCR10, CXCR1, CXCR2, CXCR3, and CXCR4 were expressed in epidermis. No expression of CCR2, CCR5, CCR7, and CCR8 was observed by either immunostaining or flow cytometry. Five chemokine receptors (CCR1, CCR10, CXCR1, CXCR2, and CXCR3) were identified, the corresponding monospecific ligands (CCL14, CCL27, CXCL8, CXCL1, CXCL10, respectively) of which were not only able to stimulate keratinocyte migration and/or proliferation but were also secreted by keratinocytes after introducing cryo-wounds into epidermal equivalents. Blocking of receptor-ligand interactions with pertussis toxin delayed re-epithelialization, but did not influence differentiation (as assessed by formation of basal layer, spinous layer, granular layer, and stratum corneum) after cryo-wounding. Taken together, these results confirm that an autocrine positive-feedback loop of epithelialization exists in order to stimulate wound closure after skin injury.     

Fibroblasts and ascorbate regulate epidermalization in reconstructed human epidermis

Skin equivalent model provides a new investigating system to study the role of extracellular matrix and dermal factors such as collagen, basement membrane components and fibroblasts (Fb) which contribute to cell-cell and cell-matrix interactions. Although basement membrane factors is known to play an important role in epidermal differentiation and epidermal-matrix adhesion, comparative effects of these extracellular matrix and dermal factors on the reconstruction of epidermis are little known. In this study, we investigated effects of type I collagen (Coll I), type IV collagen plus laminin (LAM) coated Coll I (Coll IV+LAM), and human Fb enriched Coll I (Coll I+Fb) on epidermal reconstruction. When human keratinocytes were cultured on three different gels containing Coll I, Coll IV+LAM and Coll I+Fb, basal keratinocytes were cuboidal and perpendicular to the dermo-epidermal junction only in the gel containing Coll I+Fb. Proliferation marker expression was prominent and differentiation marker expression was similar with those of normal skin in the gel containing Coll I+Fb than in the other gel models. Since ascorbate is suspected to exert an effect as a modulator of proliferation and differentiation in keratinocytes, we tested the effects of ascorbate on human epidermis reconstruction. When 25 μg/ml ascorbate was added, disordered arrangement of epidermis was disappeared and differentiation marker expression was similar with its expression in normal skin. These data indicate that human Fb and a modulator of proliferation and differentiation such as ascorbate are essential for epidermalization in reconstructed epidermis.     

A new method for studying epidermalization in vitro

A new method for studying epidermalization in vitro is described. It consists of inserting a punch biopsy that serves as a source of epidermis into dermal equivalent freshly made up, with fibroblasts mixed in a collagen matrix. Fibroblasts cling to collagen fibrils and contract the matrix, leading in 3 days to a resistant dermal equivalent holding the punch biopsy firmly in place. At day 5, a culture medium favouring epidermal growth was used and a fringe of a new epidermis appeared around the punch, the area of which grew linearly with time. This new epidermis showed a pattern of differentiation similar to epidermis in vivo, with cuboidal basal cells, keratohyalin granules, membrane coating granules and the expression of the 65-67 kd keratin subset. The method seems to combine the advantages of the explant technique and of classical keratinocyte cultures, providing the researcher with a large quantity of differentiated epidermis, the pharmacologist with simple and quantitative system in which to study modifications of growth and differentiation of epidermis, and the plastic surgeon with a possible material for skin grafting.     

病原相关分子模式对人3D皮肤皮脂腺模型表皮细胞增殖与分化影响的研究

目的：明确病原相关分子模式(PAMPs)对人表皮细胞增殖与分化的影响。方法：在人皮肤和永生化SZ95皮脂腺细胞体外共培养的3D皮肤皮脂腺培养模型中加入不同浓度(2、20、200 μg/mL)的PAMPs,包括脂多糖（LPS）,磷壁酸（LTA）和肽聚糖（PGN）,培养7天后,使用PhotoShop软件计算表皮面积;免疫组化观察Ki67,cytokeratin 10（CK10）的表达,采用ImageJ软件计算染色面积,Image-Pro Plus软件计算每张图片的累积光密度（IOD）。 结果：在不同浓度的PAMPs(LPS, LTA, PGN)作用下,表皮厚度总体较对照组呈现剂量依赖性增加;此外,表皮基底层及角质层细胞Ki67及CK10的表达也呈现不同程度的增加。结论：PAMPs具有体外促进表皮细胞的增殖与分化的作用,皮肤正常微生物可能在维护皮肤屏障功能上具有重要的生物学作用。     

Proliferation and differentiation of the keratinocytes in hyperplastic epidermis overlying dermatofibroma: immunohistochemical characterization

Epidermal changes overlying dermatofibromas (DFs) have been described as ranging from psoriasiform simple hyperplasia to basaloid hyperplasia sometimes morphologically indistinguishable from superficial basal cell carcinoma (BCC). To characterize epidermal hyperplasia overlying DFs and to determine its association with the disease process, we examined 30 cases of DF showing hyperplastic epidermis. We used nine immunohistochemical markers associated with keratinocyte proliferation or differentiation. In DFs, the dermal metallothionein (MT) expression and immunophenotypic changes with regard to epidermal differentiation varied depending on the stage of lesional evolution of the DFs. Immunostaining for epidermal growth factor receptor (EGFR), MT, and keratin 6 (K6) increased in simple hyperplastic epidermis (SHE) overlying DFs (n = 11), whereas it gradually diminished in basaloid hyperplastic epidermis (BHE) overlying DFs (n = 19). In SHE, there was a significant increase in K14 expression. Among 19 BHE cases, 12 showed premature expression of involucrin and delayed appearance of K1 along with aberrant expression of K14. Conversely, the remaining 7 BHE cases showed a pattern of involucrin and K1 similar to that of normal skin coinciding with decreased or absent dermal MT expression. Loricrin and filaggrin expression in all DFs was the same as that of normal skin. Based on the sparse positivity of Ki-67 in the hyperplastic epidermis overlying DFs, we found that the biologic ability of BHE and SHE was not apparent in the hyperproliferative state observed in psoriasis and BCC. These results suggest that the dermal fibrohistiocytic process may trigger the induction of SHE overlying DFs by an unknown mechanism and then mediate both the abnormal keratinocyte differentiation and the transformation of SHE to BHE through the evolution of the dermal lesions.     

Quantitative analysis of the proliferation of epidermal cells using a human skin organ culture system and the effect of DbcAMP using markers of proliferation (BrdU, Ki-67, PCNA)

Abstract The process of re-epithelialization of a wound in the epidermis comprises the following steps: proliferation of epidermal basal cells, migration of epidermal cells to the wound surface, and cell differentiation. In the present study, we evaluated the proliferation of epidermal basal cells, an important process in wound healing, in the wound margin using a human skin organ culture system and immunohistochemical labeling with bromodeoxyuridine (BrdU), Ki-67, and proliferating cell nuclear antigen (PCNA), as markers of cell proliferation. Dibutyryl cyclic adenosine monophosphate (DbcAMP) is a derivative of cAMP and has been shown to modulate human keratinocyte proliferation. The proliferation of keratinocytes was promoted by DbcAMP and particularly strong effects in terms of BrdU labeling index, Ki-67-positive ratio, and PCNA-positive ratio, were seen at 10^–5 M. The skin organ culture system presented here uses adult preputial skin and is a simple technique that uses easily available materials. In addition to identifying S phase cells using BrdU as an index of cell proliferation, the immunohistochemical method for evaluating the expression of Ki-67 and PCNA is very simple. Accordingly, the method described here seems to be useful for evaluating cell dynamics in wound healing. Received: 6 June 2000 / Revised: 21 July 2000 / Accepted: 23 November 2000     

Incorporation of linoleic acid by cultured human keratinocytes

Abstract Linoleic acid is required for the formation and maintenance of the epidermal barrier, but most of the current in vitro keratinocyte culture systems are linoleic acid-deficient. The aim of the present study was to examine the efficiency of linoleic acid uptake in human keratinocyte cultures grown under submerged and air-exposed conditions in serum-free medium. The water-insoluble linoleic acid was bound to carrier molecules (cyclodextrin or bovine serum albumin). Comparable results were obtained with home-made and commercially available linoleic acid complexes. In the submerged cultures, the increase of the linoleic acid medium concentration (ranging from 0 to 20 μg/ml) resulted in a gradual increase in the linoleic acid cellular content, which exceeded 1.4 times the value found in native epidermis when the highest concentration of linoleic acid was used. The addition of linoleic acid did not alter the profile of the other epidermal fatty acids, with the exception of oleic acid, which decreased in parallel with the increasing linoleic acid content. While the content of linoleic acid found in phospholipids was similar to that in native epidermis, a large excess of linoleic acid was detected in triglycerides, the synthesis of which was markedly increased in cultures grown submerged in medium containing higher concentrations of linoleic acid. Under air-exposed conditions, the dermal substrate used seemed to be the most limiting factor for efficient linoleic acid supplementation. A low linoleic acid cellular content was detected when an inert filter was used. De-epidermized dermis was found to be the most permeable substrate for linoleic acid complexes. The cellular linoleic acid content increased in a parallel with the increasing linoleic acid concentration (ranging from 4 to 30 μg/ml), but the overall amount incorporated was lower than that in submerged cultures. The content of linoleic acid in the phospholipid and ceramide fractions isolated from reconstructed epidermis grown under air-exposed conditions was close to that of native epidermis, but the triglycerides remained abnormally enriched in linoleic acid, indicating persistence of some anomalies in epidermal lipogenesis in vitro. Received: 18 June 1998 / Received after revision: 15 January 1999 / Accepted: 22 January 1999     

Control of epidermal differentiation by a retinoid analogue unable to bind to cytosolic retinoic acid-binding proteins (CRABP).

The role played by cytosolic retinoic acid-binding proteins (CRABP) in the control of differentiation and morphogenesis by retinoids remains unclear, which contrasts with the presence of these binding proteins in tissues known to be targets for retinoic acid effects. Human epidermis represents a good system to address this question because 1) the effect of retinoids on keratinocyte differentiation is well documented; 2) epidermis contains CRABP, and the amount of these proteins is modulated both by keratinization and retinoids; 3) the architecture of epidermis obtained in vitro by growing adult human keratinocytes on a dermal substrate can be modulated by retinoids added to the culture medium in a dose-dependent manner; and 4) most markers of epidermal differentiation are also modulated by retinoids in a dose-dependent manner. In this study, we compared, in dose-response experiments, the biologic activities of retinoic acid and CD271, a substance unable to bind to CRABP, but able to bind to nuclear retinoic acid receptors (RAR). Our results show that retinoic acid and CD271 exert similar controls on epidermal morphogenesis and keratinocyte differentiation, as shown by the inhibition of the synthesis of suprabasal keratins, filaggrin, and transglutaminase. Therefore, we exclude a qualitative role for CRABP in the control exerted by retinoids on the differentiation and morphogenesis of cultured human keratinocytes. Instead of being involved in the pathway via which retinoids control epidermal gene expression, CRABP might regulate the amount of intracellular-active retinoic acid and thus control quantitatively the intensity of biologic effects.     

Human dermal fibroblasts modulate the effects of retinoids on epidermal growth

We report the pharmacologic effects of retinoids in a human skin-equivalent model. This sophisticated culture system is composed, as in vivo, of a dermis and epidermis, and provides a unique in vitro system for studying dermal-epidermal interactions and thus, whether normal dermal fibroblasts influence the effects of retinoids on epidermal growth. Epidermalization was initiated on collagen substrates in which fibroblasts were either viable or lysed by osmotic shock. Retinoic acid, isotretinoin, and acitretin at 10(-6) M or 10(-7) M were added to the cultures just after epidermalization, then every two days. Epidermal growth was determined after 2 weeks in terms of the surface area, DNA content, and tritiated thymidine incorporation during the last 24 h of culture. In the absence of viable fibroblasts, retinoic acid and isotretinoin increased epidermal growth, whereas etretin inhibited it. In contrast, in the presence of viable fibroblasts, retinoic acid and isotretinoin inhibited epidermal growth, whereas etretin had no effect. Thus, retinoic acid and isotretinoin had a similar effect on keratinocyte proliferation that contrasted with that of etretin. Taken as a whole, these results show that fibroblasts, present within a collagen substrate, can modulate the pharmacologic effects of retinoids on epidermal growth.