Proliferation, C-myc, and cyclin D1 expression in diffuse alveolar damage: potential roles in pathogenesis and implications for prognosis.

In this study we compared expression of DNA topoisomerase IIalpha, a marker of cellular proliferation, c-myc, and cyclin D1 in lung biopsy specimens showing diffuse alveolar damage (DAD) with control lung tissues. We subsequently correlated DNA topoisomerase IIalpha, c-myc, and cyclin D1 expression with survival. We hypothesized that poor outcome may correlate with a higher proliferation index, and that c-myc and cyclin D1 activation are potentially important regulators of both proliferation and apoptosis in DAD. Immnuohistochemical stains for c-myc, cyclin D1, and DNA topoisomerase IIalpha were performed on 10 cases of DAD (15 cases for DNA topoisomerase IIalpha) and 10 control lungs. A proliferation index for each case was calculated by dividing the number of nuclei expressing DNA topoisomerase IIalpha by the total number of nuclei counted. The percentages of alveolar pneumocytes and interstitial cells staining positively for c-myc and cyclin D1 were estimated. The average proliferation index (DNA topoisomerase IIalpha index) in DAD (0.16 +/- 0.06, n = 15) was significantly greater than in control lungs (0.00 +/- 0.01, n = 10) (P < .0001). The average proliferation index of patients with DAD who died of respiratory failure (0.18 +/- 0.05, n = 9) was significantly greater than the average proliferation index of patients whose respiratory disease resolved or stabilized (0.11 +/- 0.05, n = 5) (P < .03). Expression of c-myc in alveolar pneumocytes and interstitial cells was more intense and slightly more widespread in cases of DAD compared with control lungs. In 9 of 10 cases of DAD, cyclin D1 expression was present in up to 30% of alveolar pneumocytes and up to 10% of interstitial cells. No staining for cyclin D1 was present in control lungs. These results show that the proliferation index in DAD potentially correlates with patient survival. Furthermore, enhanced expression of c-myc and cyclin D1 may contribute to dysregulation of cellular proliferation and apoptosis observed in DAD.     

Association of p53 and WAF1 expression with apoptosis in diffuse alveolar damage.

Little is known about alterations in cell cycle regulatory proteins such as p53 and WAF1 in diffuse alveolar damage (DAD). We hypothesized that up-regulation of p53 and WAF1 in type II pneumocytes in DAD is associated with underlying DNA damage and apoptosis. Twenty cases of DAD and twenty control specimens of lung adjacent to resected tumors were studied. Immunohistochemical stains with antibodies recognizing p53 and WAF1 were performed, and apoptosis was assessed in sixteen cases by the nick end-labeling method. We identified p53 expression and apoptosis in all cases of DAD but not in any of the control lungs. We detected WAF1 expression in nineteen of twenty cases of DAD and in sixteen of twenty control lungs. In general, the distribution and intensity of WAF1 staining were greater in DAD than in control lungs. Staining for both p53 and WAF1 and labeling of apoptotic cells in DAD were usually focal ( < 10% of cells) and predominantly localized in type II pneumocytes. We conclude that increased p53 and WAF1 expression in DAD reflects normal physiological up-regulation in response to cellular and DNA damage and is associated with apoptosis of type II pneumocytes. p53-dependent apoptosis may contribute to the pathogenesis of this disease.     

大鼠肢体缺血再灌注后肺组织BAX基因表达上调

目的探讨在体大鼠肢体缺血再灌注(LIR)后肺组织BAX和BCL-2基因表达的变化。方法在大鼠肢体缺血再灌注(LIR)损伤动物模型上,用TUNEL法、电泳法及免疫组织化学等技术观察LIR后肺损伤发生过程中,肺组织细胞凋亡变化以及BAX和BCL-2蛋白质表达的改变。结果大鼠LIR后,肺血管内皮细胞及附壁的炎细胞凋亡明显增加;肺组织BCL-2表达的变化不大,但BAX蛋白质表达明显上调,DNA断链率升高,活性氧(ROS)含量增加,且与肺组织细胞凋亡的增加相一致。结论肺组织细胞凋亡以及BAX和BCL-2表达的变化可能参与LIR后肺损伤的发生。     

诱导细胞凋亡青蒿琥酯抗食管癌作用机制研究

 [摘要] 目的 研究青蒿琥酯诱导食管癌细胞凋亡作用及探讨青蒿琥酯抗食管癌作用机制。方法 不同浓度的青蒿琥酯(Artesunate, Art)(0、10、20、40μg/ml) 作用Eca109细胞24h,流式细胞术（Flow cytometry, FCM）方法检测细胞凋亡、周期及细胞中bcl-2和bax蛋白的表达量。结果 青蒿琥酯作用Eca109细胞24h后,与对照组相比,细胞凋亡率显著增高P<0.05,且具有剂量依赖性。青蒿琥酯组与对照组相比,Eca109细胞中bcl-2蛋白表达水平及细胞增殖指数显著降低P<0.05,而bax蛋白表达量显著增高P<0.05,且具有剂量依赖性。结论 青蒿琥酯可以通过调节Eca109细胞中bcl-2、bax蛋白表达水平和细胞增殖,从而诱导Eca109细胞产生凋亡,起到抗食管癌作用。     

RNA干扰沉默Bax基因对线粒体途径软骨细胞凋亡的影响

 【摘要】 目的 利用体外培养的鼠软骨细胞,研究RNA干扰沉默Bax基因表达对经线粒体途径细胞凋亡的影响。方法 体外分离培养SD大鼠软骨细胞;Bax siRNA干扰沉默Bax基因表达。RT-PCR和Western blot检测mRNA及蛋白表达水平;MTT法检测细胞活力;Annexin V-FITC/PI双标记法检测细胞凋亡率;Western blot检测Bcl-2、Cytochrome C蛋白的表达。结果 Bax siRNA干扰24h后,Bax的mRNA和蛋白的表达水平均明显降低。细胞凋亡受到明显抑制,细胞存活率增高。并且,在Bax基因沉默的细胞中,Cytochrome C蛋白表达水平降低,同时Bcl-2蛋白表达水平升高。结论 RNA干扰沉默Bax基因可抑制鼠软骨细胞凋亡并且促进其存活,其机制可能与线粒体途径相关。     

NPM1基因突变表达对THP-1白血病细胞增殖和凋亡的作用探讨

 摘要：目的 探讨核仁磷酸蛋白（NPM1）基因突变对白血病细胞增殖潜能和凋亡发生的影响。方法 将携带NPM1 A型突变（NPM1 mA）的重组质粒载体pEGFPC1-NPM1 mA转染白血病THP-1细胞系,构建稳定表达NPM1 A型突变蛋白的白血病细胞株(THP-1 mA),同时设立未处理组（THP-1）和空载体转染组（THP-1 C1）作为对照。通过MTT试验观察细胞体外增殖能力,流式细胞术分析细胞周期分布及凋亡发生率的改变;采用RT-PCR和Western blot分别检测细胞凋亡相关蛋白（Bax和Bcl-2）mRNA及蛋白表达水平。结果 与未处理组和空载体转染组细胞相比较,携NPM1突变体的THP-1 mA细胞体外增殖能力明显增强,S期细胞比例明显增高,G1期细胞比例显著减低;而NPM1突变体转染后THP-1细胞的凋亡率没有显著变化,同时细胞凋亡相关蛋白Bax, Bcl-2的mRNA和蛋白表达以及Bax/Bcl-2比值亦未见明显改变。结论 NPM1突变基因能够促进白血病细胞的体外增殖能力,而对白血病细胞凋亡无显著影响,这为进一步阐明NPM1突变与AML的关系提供了新的科学依据。     

Distribution of apoptosis-related proteins in the quail ovary during folliculogenesis: BCL-2, BAX and CPP32

It is suggested that follicular apoptosis is driven by the status of the BCL-2: BAX rheostat, and that CPP32 is a key effector of granulosa cell death. In the present study, we have immunohistochemically localized two BCL-2 family members, BCL-2 and BAX, and one caspase, CPP32, in the quail ovary during folliculogenesis. BCL-2 was predominantly found in the granulosa cells of developing follicles. BAX was detected in some follicular cells of atretic follicles, and in the nucleus of some prelampbrush oocytes. Expression of CPP32 was detected in leukocytes and in follicular cells of atretic follicles. Immunostaining was also found in interstitial cells, in surface epithelial and vascular endothelial cells, and in some thecal cells of post-ovulatory follicles. In the granulosa cells of non-growing and small prehierarchal follicles, a weak immunostaining was observed. We can conclude that in the avian ovary, BAX and CPP32 are involved in atresia. The present results support the BCL-2: BAX rheostat hypothesis.     

人感染高致病性禽流感病毒H5N1的病理学观察

目的 观察人感染高致病性禽流感病毒H5N1后各主要脏器的病理改变.方法 按传染病尸体解剖要求对2例死亡病例系统解剖,并获得心、肝、脾、肺和肾等主要脏器,对1例重症患者行肺大泡切除术,组织常规HE和免疫组织化学染色,光学显微镜下观察.结果 2例肺组织主要呈弥漫性肺泡损伤改变.早期呈渗出性改变,肺泡上皮坏死脱落,肺泡腔内见大量均匀粉染渗出液伴广泛透明膜形成.中晚期主要呈增生性和纤维化性改变,肺泡上皮和支气管上皮增生,肺泡腔内渗出物和肺间质纤维化.1例在慢性支气管扩张症基础上伴弥漫性肺泡损伤和肺间质纤维化.免疫器官改变:全身淋巴组织萎缩伴活跃的噬血现象.其他脏器病变:1例心脏有间质性心肌炎;1例肾脏有急性肾小管坏死;1例有脑水肿伴脑实质内神经细胞嗜酸性变,轴突肿胀,粗细不均.脑室旁见灶状坏死.1例孕妇胎盘内多灶状滋养叶细胞坏死伴营养不良性钙化,有急性坏死性蜕膜炎.胚胎肺脏有肺水肿和肺炎改变.结论 人感染高致病性禽流感病毒H5N1后首先出现呼吸系统症状,广泛弥漫性肺泡损伤致低氧血症是病理学基础,患者最终因多器官功能衰竭致呼吸、循环衰竭死亡.     

Production of the proto-oncogene BAX does not vary with changing in luteal function in women

The mechanisms of luteal maintenance and regression in women are uncertain, but morphological and oligonucleosome studies raise the possibility that apoptosis may be involved. BAX is a proto-oncogene of the BCL-2 family which can induce apoptosis. The aim of this study was to determine whether BAX is expressed in the human corpus luteum and whether the level of expression changes relative to the stage of the luteal phase or in simulated early pregnancy. Carefully timed samples of corpus luteum were studied by immunostaining, sodium dodecyl sulphate-polyacrylamide gel electrophoresis and immunoblotting. BAX protein was immunolocalized in luteal sections from all stages including luteal rescue but BAX production did not change during luteal maintenance or regression. Localization of BAX to the steroid-secreting cells of the corpus luteum implies a functional role and BAX may interact with other members of the BCL-2 family to affect luteal function.      

Effects of intrapulmonary viral tropism and cytokine expression on the histological patterns of cytomegalovirus pneumonia

Pulmonary cytomegalovirus (CMV) infection causes fatal CMV pneumonia (CMVp) in immunocompromised patients; however, the mechanisms underlying CMV-infection-induced pulmonary lesion development remain largely unknown. We examined the relationship between CMVp patterns and intrapulmonary viral tropism, including expression of inflammatory cytokines and related molecules. Double immunohistochemistry of CMV antigen and cellular markers showed that epithelial tropism was associated with a diffuse alveolar damage (DAD) pattern (CMVp-DAD) while stromal tropism was associated with a predominantly interstitial inflammation/fibrosis (IIF) (CMVp-IIF) or a combination of DAD and IIF (CMVp-complex). Transforming growth factor (TGF)-β1 expression was relevant to CMV-induced tissue injury, and its expression was higher in CMVp-complex and CMVp-IIF than in CMVp-DAD. Expression of integrin β6 (ITGB6), an adhesion molecule and important activator of TGF-β1 in interstitial pneumonia, was lost in CMV-infected pneumocytes, especially CMVp-DAD, whereas CMV-negative pneumocytes in CMVp-complex and CMVp-IIF showed overexpression. Diffuse interleukin (IL)-8 up-regulation and strong expression were present in both CMV-infected pneumocytes and stromal cells only in CMVp-IIF cases with marked interstitial neutrophilic infiltration. On the basis of viral tropism and the expression of TGF-β1, ITGB6, and IL-8, we conclude that CMV-infected pulmonary cells play an important role in the development of diverse CMVp patterns.     

Transforming growth factor-beta 1 (TGF-β1) expression in ovine lentivirus-induced lymphoid interstitial pneumonia

The aim of this study was to detect the localization of TGF-β1 protein expression in normal sheep lungs and lungs with interstitial pneumonia associated with infection with maedi-visna virus (MVV). Immunohistochemical localization of TGF-β1 was determined in 24 lungs of adult sheep naturally infected with MVV and six control lungs of seronegative sheep. The lungs of infected animals showed different lesional degrees: grade 0, no lesions; grade I, mild; grade II, moderate; grade III, severe. In normal lungs, TGF-β1 was primarily expressed in airway epithelium, bronchial cartilage and glands, endothelial cells and smooth muscle of blood vessels, alveolar macrophages and type II pneumocytes. No staining was observed in alveolar interstitium. In MVV-infected sheep an increased number of positive alveolar and interstitial macrophages and staining of alveolar interstitium was observed in grade I, grade II and some grade III lesions. In grade III lesions an inverse relationship was found between TGF-β1 staining and smooth muscle hyperplasia. Small lymphoid aggregates, in general, showed strong reactivity, whereas larger ones showed weak reactivity, mainly associated with follicular areas. No significant differences in the staining intensity of airways and blood vessels were observed between control and MVV lungs. The increased expression of TGF-β1 in early maedi lesions and its down-regulation in more advanced disease suggest the operation of a temporal regulatory mechanism whereby early expression may lead to the smooth muscle hyperplasia which develops during the disease. The striking inverse relationship between TGF-β1 expression and follicle organization is intriguing and warrants further investigation.     

纳秒级陡脉冲可用于治疗裸鼠人恶性黑色素瘤

 摘要 目的:观察纳秒级陡脉冲(Nanosecond Pulsed Electric Fields, nsPEF)治疗裸鼠皮下人恶性黑色素瘤的效果及其机制。方法：建立裸鼠皮下人黑色素瘤模型,随机分为长期治疗组及对照组各10只,观察肿瘤生长、裸鼠存活率时间,和短期治疗组(=10;分2h、4d组及对照组(分别为4、6和6只),以HE染色检查细胞形态,DNA琼脂糖凝胶电泳、TUNEL法分析细胞凋亡,Western blot法、免疫组织化学方法分析组织肿瘤Bax、Bcl-2的表达。两组均用电场峰值40kV/cm、脉冲宽度200ns、频率1Hz、脉冲次数1000个的nsPEF进行治疗。结果：长期治疗后即刻看到肿瘤区均变为灰白色,表面皮肤均没有出血现象,肿瘤质地变硬;随生存时间延长,肿瘤体积较对照组明显缩小(P<0.01);平均生存时间（天）较对照组（天）明显延长(P<0.01);短期治疗组,4d时坏死区域增多;4d时琼脂糖凝胶电泳显示较对照组有明显“ladder”状分布,凋亡率明显高于对照组(P<0.01),较对照组相比Bax表达明显增高(P<0.01)、而Bcl-2表达明显降低(P<0.01)。结论：nsPEF对裸鼠皮下人黑色素瘤有明显的治疗效果,可能是通过调控Bax、Bcl-2 基因表达诱导细胞凋亡。     

电刺激大鼠室旁核减轻缺血-再灌注胃黏膜细胞凋亡

目的研究电刺激大鼠室旁核(PVN)对胃缺血-再灌注(GI-R)损伤的保护作用及细胞机制。方法电刺激大鼠PVN后,制备GI-R模型;用免疫组化方法检测胃黏膜细胞的凋亡和增殖以及凋亡相关基因BCL-2、BAX的表达。结果与单纯GI-R组相比,电刺激PVN能明显减少GI-R后30 min、1 h和3 h胃黏膜细胞的凋亡,并能加快胃黏膜细胞的增殖;同时可以明显增加抗凋亡因子BCL-2的蛋白表达,降低促凋亡因子BAX的蛋白表达。结论电刺激大鼠PVN对GI-R损伤的保护作用可能是通过上调抗凋亡因子BCL-2、下调促凋亡因子BAX的蛋白表达,从而促进了胃黏膜细胞增殖、抑制其凋亡来实现的。     

Apoptosis and proliferation in subcutaneous panniculitis-like T-cell lymphoma.

Subcutaneous panniculitis-like T cell lymphoma (SPTCL), designated recently as a distinct clinicopathologic entity in the World Health Organization Classification, is a neoplasm composed of cytotoxic T-cells that preferentially involves subcutaneous adipose tissue. Histologically, SPTCL is characterized by extensive karyorrhectic debris and tumor necrosis suggesting that apoptotic mechanisms are involved in its pathogenesis. We assessed the apoptotic index (AI) and proliferation rate (PR) of 13 cases of SPTCL by TUNEL test and Ki-67 immunostaining, respectively. We also immunohistochemically assessed for expression of BCL-2 (anti-apoptosis), BAX (pro-apoptosis), and P53 and correlated the results with apoptosis and proliferation. We detected a high AI (median 8.1%) in 11 cases of SPTCL, and 12 cases had low BCL-2 and high BAX expression. BCL-2 expression inversely correlated with AI (P <.001) and BAX (P <.001). We found a low PR (cutoff > or = 25%) in eight (61%) cases. There was an inverse correlation between AI and PR (r = -.58, P =.04). Ten cases were assessed for P53; immunostaining results were heterogeneous but P53 expression correlated with large cell cytologic features. Our findings demonstrate that SPTCLs have a high AI that may be explained by differential expression of BCL-2 and BAX in the neoplastic cells.     

葛根素减轻乙醇导致大鼠生精细胞的凋亡

目的 观察乙醇导致大鼠生精细胞的凋亡及葛根素的干预。方法 将大鼠30 只,随机均分为对照组、乙醇组及葛根素干预组。于实验第40天免疫组织化学法（SABC）检测左侧睾丸各组Bcl-2、Bax 蛋白在生精细胞的表达; RT-PCR检测右侧睾丸各组Bcl-2及Bax mRNA的表达;TUNEL 法检测生精细胞的凋亡。结果 醇组平均每个生精小管断面中Bcl-2 蛋白阳性细胞数和A值低于对照组(P<0.01),而平均每个生精小管断面中Bax 蛋白的阳性细胞数和A值高于对照组(P<0.01);乙醇组Bax mRNA表达较葛根素干预组及对照组强（P<0.05）,而Bcl-2 mRNA表达较葛根素干预组及对照组弱（P<0.05）;乙醇组每个生精小管横切面中的凋亡细胞数目高于对照组(P< 0.01),葛根素干预组显著缓解上述变化。结论 根素对乙醇导致的大鼠生精细胞凋亡有干预作用。     

Immunohistochemical detection of ubiquitin-positive intracytoplasmic eosinophilic inclusion bodies in diffuse alveolar damage

AIMS: To clarify the relationship between ubiquitin-positive pneumocytes and intracytoplasmic eosinophilic inclusion bodies (IB) in patients who died of diffuse alveolar damage (DAD). METHODS AND RESULTS: Eighteen patients with DAD were studied, in whom hyaline membranes were present in one or more out of five sections from each lobe of the lungs and 15 patients with no DAD. Light microscopy revealed hyaline membrane in over 25% of lobes from 18 patients with DAD. The cytoplasm of pneumocytes from six of 18 cases of DAD contained IB. Immunohistochemically, all IBs were characteristically positive for both ubiquitin (Ub) and cytokeratin KL-1. Cytoplasmic granules were also Ub+ in four cases of DAD without IB. IB+ or Ub+ pneumocytes were undetectable in non-DAD patients. We evaluated DAD severity based on hyaline membrane formation; the mean score in DAD with IB (3.60; n = 6) was significantly higher than that in Ub- (2.92; n = 8). Ub+ pneumocytes were found with or without IB among those cases with high DAD scores. CONCLUSIONS: These findings suggest that disordered proteolysis in the Ub-mediated proteasome system leads to the accumulation of abnormal ubiquitinated protein, which includes cytokeratin, in pneumocytes. This is the first report to suggest that Ub+ pneumocytes are associated with disease severity in patients with DAD.     

棕榈酸诱导胰岛素瘤细胞MIN6细胞凋亡

目的探讨蛋白激酶B及其磷酸化在棕榈酸诱导的胰岛素瘤细胞MIN6凋亡中的作用。方法胰岛素瘤细胞MIN6分别在含有不同棕榈酸浓度(0～0.5 mmol/L)的DMEM高糖培养基中孵育,培养基中加或不加PI3K/PKB的阻断剂LY294002;TUNEL法观察凋亡并计数凋亡率;透射电镜观察MIN6细胞超微结构;Western blot检测蛋白激酶B(PKB)及其磷酸化蛋白p-PKB(Ser473)的表达;RT-PCR法检测BAX、BCL-2mRNA的表达。结果MIN6细胞凋亡随着培养基中棕榈酸浓度的增加而增加,LY294002可增强其凋亡程度;棕榈酸抑制MIN6细胞的PKB在473位丝氨酸位点的磷酸化,抑制BCL-2mRNA的表达并促进BAXmRNA的表达。结论棕榈酸可能通过抑制PKB磷酸化的激活而诱导糖尿病时胰岛β细胞的凋亡。     

Coexpression of Aspartic Proteinases and Human Leukocyte Antigen-DR in Human Transplanted Lung

Aspartic proteinases have recently been shown to be implicated in antigen processing. We explored the expression of two aspartic proteinases, cathepsins E and D, and of human leukocyte antigen-DR (HLA-DR) molecules in a consecutive series of 80 transbronchial biopsies from transplanted lungs. For controls, we studied five normal donor lungs (not suitable for transplantation on account of thoracic trauma) and macroscopically normal areas of three cancer-affected lungs. Two of the five unsuitable donor lungs showed minimal inflammatory changes. Macroscopically normal samples from the three cancerous lungs showed mild and focal inflammatory infiltrates. In histologically normal lungs, HLA-DR expression was limited to professional antigenpresenting cells. Macroscopically normal lung samples with minimal inflammatory changes from both donor and cancer lungs showed variable HLA-DR expression by alveolar and bronchial epithelial cells and by endothelial cells. All transplanted lung biopsies showed HLA-DR expression by epithelial (alveolar and bronchial) and endothelial cells, with a trend for increased positivity in acute rejection. Cathepsin E was restricted to Clara and to rare bronchus-associated lymphoid tissue-related epithelial cells in histologically normal lung samples, whereas minimal de novo cathepsin E expression by rare alveolar pneumocytes was noted in control lung samples exhibiting minimal inflammatory changes. In all transplanted lung biopsies, cathepsin E was diffusely expressed de novo by hyperplastic alveolar epithelial cells, regardless of the presence or degree of rejection. Cathepsin D was expressed only by alveolar macrophages and by ciliated bronchial cells of normal, minimally inflamed, and transplanted lungs. In transplanted lung, Clara cells and several hyperplastic alveolar pneumocytes coexpressed HLA-DR and cathepsin E, whereas all alveolar macrophages and a few ciliated cells coexpressed cathepsin D and HLA-DR The present investigation suggests that the de novo expression of cathepsin E and HLA-DR by hyperplastic alveolar pneumocytes of transplanted lung may be crucial for antigen processing and presentation to recipient competent T cells, and thus for the triggering of the immune-inflammatory cascade that leads to rejection.     

Differential immunolocalization of VEGF in rat and human adult lung,and in experimental rat lung fibrosis: Light,fluorescence, and electron microscopy

Vascular endothelial growth factor (VEGF) is a cytokine with main angiogenetic functions in embryonic development and tumor‐formation. In the adult lung, reports of the localization of VEGF were controversial. A precise cell typing of VEGF‐positive pulmonary cells is still lacking. Nothing is known about a potential role in pulmonary fibrosis. Immunohistochemistry (IH), double immunofluorescence microscopy (DIF), and immunoelectron microscopy (IEM) were used to study the differential distribution of VEGF in paraffin‐embedded (IH, DIF) and in cryo‐substituted, Lowicryl‐embedded (IEM) specimens of normal rat and human lungs and fibrotic rat lungs. Fibrosis was induced by intratracheal bleomycin treatment. IH and DIF showed that VEGF was present in surfactant protein (SP) D‐positive alveolar type II pneumocytes, bronchiolar Clara cells, smooth muscle (SM) cells, and α‐SM actin‐positive myofibroblasts of normal rat and human lungs. Fibrotic lesions in bleomycin‐treated rat lungs were rich in VEGF‐positive cells presenting with a heterogeneous phenotype (mainly SP‐D‐positive type II pneumocytes, α‐SM actin‐positive myofibroblasts). There were no signs of angiogenesis. Post‐embedding immunogold labeling using protein A‐gold and IgG‐gold technique revealed a specific localization of VEGF to mitochondria, Clara cell secretory granules, and capillary interendothelial cell junctions. The predominant localization of VEGF to bronchiolar and alveolar epithelial and α‐SM actin‐positive cells, and the marked increase of VEGF‐positive type II pneumocytes and myofibroblasts in fibrotic lung lesions, indicate that in adult lungs VEGF is involved in processes other than angiogenesis. Anat Rec 254:61–73, 1999. © 1999 Wiley‐Liss, Inc.