The distribution of CD34-positive stromal cells and myofibroblasts in colorectal carcinoid tumors

In order to understand the stromal reaction associated with colorectal neoplasms, we examined specimens from 26 patients including normal colorectal tissues (n=15), carcinoid tumors (n=12), well differentiated adenocarcinomas (n=10), and poorly differentiated adenocarcinomas (n=4), using an immunohistochemical method. Myofibroblasts and CD34-positive stromal cells were distributed in the mucosa and in the area between the submucosal and subserosal layers, respectively. However, the distribution of these cells markedly changed with the invasion of neoplasms. Namely, myofibroblasts were abundant in the invasive stroma of all colorectal neoplasms. CD34-positive stromal cells were completely absent from the invasive stroma of colorectal cancers. On the other hand, CD34-positive stromal cells were absent from four out of five carcinoid tumor cases with lesions measuring less than 2 mm in size, but were present in all seven cases of carcinoid tumors measuring more than 2 mm. Double-immunostaining identified stromal cells expressing both ASMA and CD34 in several carcinoid tumor cases. Finally, no CD34-positive stromal cells were observed in the invasive stroma of colorectal cancers. However, the distribution of these cells in carcinoid tumors may depend on the lesion size. Namely, CD34-positive stromal cells existed between neoplastic nests in large-sized carcinoid tumors. Myofibroblasts in the stroma of colorectal neoplasms may originate from CD34-positive stromal cells.     

Distribution and role of CD34-positive stromal cells and myofibroblasts in human normal testicular stroma

CD34-positive stromal cells are distributed in various organs including breast, Fallopian tubes, thyroid gland, colon, pancreas, and uterine cervix. To elucidate the distribution of CD34-positive stromal cells, smooth muscle cells, and myofibroblasts in normal human testis, we examined 48 testes obtained by autopsy and operation, including five fetal, one neonatal, and 42 adult cases without evident testicular lesions, using a streptavidin-biotin immunoperoxidase technique. The expression of alpha-smooth muscle actin (ASMA), h-caldesmon, CD34, and CD31 were immunohistochemically examined in all cases. The tunica albuginea and the inner layer of seminiferous tubules in adult testis were predominantly composed of myofibroblasts. Smooth muscle cells were also scattered throughout these sites in some cases. CD34-positive stromal cells were abundant, and they formed a reticular network around the seminiferous tubules and Leydig cells as well as the outer layer of seminiferous tubules. Moreover, myofibroblasts and the CD34 reticular network were already present in the testicular stroma during fetal or neonatal development. Double immunostaining of fetal, neonatal and adult testes using ASMA and CD34 confirmed that myofibroblasts and CD34-positive stromal cells were present in the inner and outer layers of peritubular tissue, respectively. This distribution and cytological identification was also confirmed by an ultrastructural study of four cases. Finally, CD34-positive stromal cells and myofibroblasts are major components of human testicular stroma.     

The appearance of myofibroblasts and the disappearance of CD34-positive stromal cells in the area adjacent to xanthogranulomatous foci of chronic cholecystitis

We investigated the distribution of myofibroblasts and CD34-positive stromal cells in normal gallbladder and its pathological conditions (cholecystitis, n=25) using immunohistochemistry and in situ hybridization. In the wall of normal gallbladder, myofibroblasts were generally absent from all layers, but many CD34-positive stromal cells were observed in the connective tissue layer. In chronic cholecystitis with mild perimuscular fibrosis, a small to moderate number of myofibroblasts appeared in the mucosal layer. In chronic cholecystitis with marked perimuscular fibrosis, a small to large number of myofibroblasts appeared predominantly in the connective tissue layer, whereas the number of CD34-positive stromal cells decreased at the same location, although the number of myofibroblasts increased. In chronic cholecystitis with xanthogranulomatous foci, a small to large number of myofibroblasts were observed in the periphery of the xanthogranulomatous reaction and adjacent area. In contrast, CD34-positive stromal cells were completely absent or were limited to the area just around the xanthogranulomatous reaction. Induction of collagen type I and III mRNA was predominantly observed in the cytoplasm of myofibroblasts associated with the marked fibrosis, which consisted primarily of mature collagen fibers, and in the cytoplasm of myofibroblasts around the xanthogranulomatous reaction, respectively. Finally, myofibroblasts were observed in all subtypes. The increased number of myofibroblasts was most prominent in the connective tissue layer of chronic cholecystitis with marked perimuscular fibrosis or in the area adjacent to xanthogranulomatous foci of chronic cholecystitis. Under these conditions, CD34-positive stromal cells tended to disappear from the connective tissue layer, which exhibited an increase in myofibroblasts.     

The distribution and role of myofibroblasts and CD34-positive stromal cells in normal pancreas and various pancreatic lesions

To elucidate the distribution and role of myofibroblasts and CD34-positive stromal cells in various pancreatic lesions, we performed an immunohistochemical study using a streptoavidin-biotin immunoperoxidase technique. We selected 43 pancreatic lesions from 1 biopsied, 22 surgically resected and 12 autopsied specimens: acute pancreatitis (n=3), chronic non-obstructive pancreatitis (n=4), obstructive pancreatitis (n=7), islet cell tumor (n=4), serous cystadenoma (n=7), mucinous cystadenoma (n=6), and invasive ductal carcinoma (n=12). In normal pancreas, myofibroblasts and CD34-positive stromal cells were predominantly present in the peridcutal and periacinar areas, respectively. Both myofibroblasts and CD34-positive cells were observed in the stroma of chronic pancreatitis. In four islet cell tumors, myofibroblasts were present in the stroma of the tumor center, but no CD34-positive stromal cells were identified. Additionally, myofibroblasts and CD34-positive stromal cells were located in the inner layer and the outer layer of the capsule of three islet cell tumors, respectively. In nine of the thirteen cystadenomas, only myofibroblasts were recognized in the cyst wall. In the remaining four cystadenomas, a small number of CD34-positive cells were observed in the cyst wall. In 12 invasive ductal carcinomas, the stroma possessed a lot of myofibroblasts, but there were no or few CD34-positive stromal cells. In conclusion, it seems that the abundant amount of CD34-stromal cells in the main lesions is characteristic of chronic inflammatory lesions. Myofibroblasts and CD34-positive stromal cells may play a role in regulating the tumor growth in the capsule of islet cell tumors of the pancreas.     

The distribution of myofibroblasts and CD34-positive stromal cells in normal renal pelvis and ureter and their cancers

In this article, we examined the distribution of myofibroblasts and CD34-positive stromal cells in normal renal pelvis and ureter and their cancers using immunohistochemistry. Eighteen tumors and normal tissues apart from the main tumor were examined. In the wall of normal renal pelvis and ureter, no myofibroblasts were observed through all layers, but CD34-positive stromal cells were observed in the deep area of lamina propria, muscular layer and adventitia. In the stroma of renal pelvic and ureteral cancers, myofibroblasts were distributed in fifteen tumors and were absent in three tumors. All three tumors containing no myofibroblasts in the stroma were non-invasive type and all invasive cancers contained myofibroblasts in the stroma. CD34-positive stromal cells were consistently absent in the stroma of cancers, irrespective of the invasiveness. Finally, myofibroblasts are major stromal components in renal pelvic and ureteral cancers, particularly in invasive cancers, and CD34-positive stromal cells are consistently absent or lost in the stroma of their cancers. These findings suggest that the invasion of renal pelvic and ureteral cancers may cause the phenotypic change of stromal cells.     

The disappearance of CD34-positive and alpha-smooth muscle actin-positive stromal cells associated with human intra-uterine and tubal pregnancies

In order to elucidate the change in alpha-smooth muscle actin (ASMA)-positive and CD34-positive stromal cells associated with pregnancy, we examined endometrial and Fallopian tube tissues from 40 patients including normal endometrium (n=10), intra-uterine pregnancy (n=10), normal Fallopian tube (n=10), and tubal pregnancy (n=10), using immunohistochemistry. In normal endometrium, only a few ASMA-positive cells were focally observed. Additionally, a wide range of CD34-positive stromal cell abundance was observed. In normal Fallopian tube mucosa, a small to moderate number of both ASMA-positive and CD34-positive stromal cells was observed. Neither ASMA-positive nor CD34-positive stromal cells were observed anywhere in the decidual stroma during both intra-uterine and tubal pregnancies. Likewise, a varying abundance of ASMA-positive cells but no CD34-positive stromal cells were observed at the fetal side during both intra-uterine and tubal pregnancies. In conclusion, the disappearance of CD34-positive and ASMA-positive stromal cells may be an indicator of decidualisation induced change in the stroma during both intra-uterine and tubal pregnancies. ASMA-positive stromal cells at the fetal side associated with pregnancy may play a role in the production of villous extracellular matrix or regulation of blood flow.     

Identification of circulating fibrocytes as precursors of bronchial myofibroblasts in asthma

The mechanisms contributing to airway wall remodeling in asthma are under investigation to identify appropriate therapeutic targets. Bronchial myofibroblasts would represent an important target because they play a crucial role in the genesis of subepithelial fibrosis, a characteristic feature of the remodeling process, but their origin is poorly understood. We hypothesized that they originate from fibrocytes, circulating cells with the unique characteristic of expressing the hemopoietic stem cell Ag CD34 and collagen I. In this study we show that allergen exposure induces the accumulation of fibrocyte-like cells in the bronchial mucosa of patients with allergic asthma. These cells are CD34-positive; express collagen I and alpha-smooth muscle actin, a marker of myofibroblasts; and localize to areas of collagen deposition below the epithelium. By tracking labeled circulating fibrocytes in a mouse model of allergic asthma, we provide evidence that fibrocytes are indeed recruited into the bronchial tissue following allergen exposure and differentiate into myofibroblasts. We also show that human circulating fibrocytes acquire the myofibroblast phenotype under in vitro stimulation with fibrogenic cytokines that are produced in exaggerated quantities in asthmatic airways. These results indicate that circulating fibrocytes may function as myofibroblast precursors and may contribute to the genesis of subepithelial fibrosis in asthma.     

Human cytomegalovirus infection of bone marrow myofibroblasts enhances myeloid progenitor adhesion and elicits viral transmission

Human cytomegalovirus (CMV) infection of bone marrow transplant recipients can cause pancytopenia, as well as life-threatening interstitial pneumonia. CMV replicates actively in bone marrow stromal cells, whereas it remains latent in hematopoietic progenitors. Our aim was to study the influence of CMV infection on adherence of CD34(+) cells to the myofibroblastic component of human bone marrow and examine transmission of virus from myofibroblasts to CD34(+) cells. We show that smooth actin, but not fibronectin, organization is markedly modified by CMV infection of bone marrow stromal myofibroblasts. Nonetheless, CMV infection led to increased adherence of the CD34(+) progenitor cell line, KG1a, relative to adherence to uninfected myofibroblasts from the same donors. Adherence of CD34(+) cells to infected bone marrow myofibroblasts resulted in transfer of virions and viral proteins through close cell-to-cell contacts. This phenomenon may play a role in the pathophysiology of CMV bone marrow infection and in eventual virus dissemination.     

Follicular dendritic cells are related to bone marrow stromal cell progenitors and to myofibroblasts

Follicular dendritic cells (FDC) are involved in the presentation of native Ags to B cells during the secondary immune response. Some authors consider FDC to be hemopoietic cells, whereas others believe them to be mesenchymal cells. The low proportion of FDC in the lymphoid follicle, together with technical difficulties in their isolation, make these cells difficult to study. We show that Fibroblast Medium can be used successfully to isolate and maintain FDC lines. In this culture medium, we obtained 18 FDC lines from human tonsils, which proliferated for as long as 18 wk and showed a stable Ag phenotype as detected by flow cytometry and RT-PCR. FDC lines were CD45-negative and expressed Ags associated to FDC (CD21, CD23, CD35, CD40, CD73, BAFF, ICAM-1, and VCAM-1) and Ags specific for FDC (DRC-1, CNA.42, and HJ2). These cell lines were also able to bind B cells and secrete CXCL13, functional activities characteristic of FDC. Nevertheless, the additional expression of STRO-1, together with CD10, CD13, CD29, CD34, CD63, CD73, CD90, ICAM-1, VCAM-1, HLA-DR, alkaline phosphatase, and alpha-smooth muscle actin (alpha-SM actin) indicated that FDC are closely related to bone marrow stromal cell progenitors. The expression of alpha-SM actin also relates FDC with myofibroblasts. Like myofibroblasts, FDC lines expressed stress fibers containing alpha-SM actin and were able to contract collagen gels under the effect of TGFbeta1 and platelet-derived growth factor. These findings suggest that FDC are a specialized form of myofibroblast and derive from bone marrow stromal cell progenitors.     

Bone-marrow-derived myofibroblasts contribute to the cancer-induced stromal reaction

To confirm whether human cancer-induced stromal cells are derived from bone marrow, bone marrow (BM) cells obtained from beta-galactosidase transgenic and recombination activating gene 1 (RAG-1) deficient double-mutant mice (H-2b) were transplanted into sublethally irradiated severe combined immunodeficient (SCID) mice (H-2d). The human pancreatic cancer cell line Capan-1 was subcutaneously xenotransplanted into SCID recipients and stromal formation was analyzed on day 14 and on day 28. Immunohistochemical and immunofluorescence studies revealed that BM-derived endothelial cells (X-gal/CD31 or H-2b/CD31 double-positive cells) and myofibroblasts (X-gal/alpha-smooth muscle actin or H-2b/alpha-smooth muscle actin double-positive cells) were present within and around the cancer nests. On day 14, the frequencies of BM-derived endothelial cells and BM-derived myofibroblasts were 25.3+/-4.4% and 12.7+/-9.6%, respectively. On day 28, the frequency of BM-derived endothelial cells was 26.7+/-9.7%, which was similar to the value on day 14. However, the frequency of BM-derived myofibroblasts was significantly higher (39.8+/-17.1%) on day 28 than on day 14 (P<0.05). The topoisomerase IIalpha-positive ratio was 2.2+/-1.2% for the H-2b-positive myofibroblasts, as opposed to only 0.3+/-0.4% for the H-2b-negative myofibroblasts, significant proliferative activity was observed in the BM-derived myofibroblasts (P<0.05). Our results indicate that BM-derived myofibroblasts become a major component of cancer-induced stromal cells in the later stage of tumor development.     

Consistent lack of CD34-positive stromal cells in the stroma of malignant breast lesions

To examine the distribution of CD34-positive and ASMA-positive stromal cells in various breast lesions, we performed immunohistochemical assays (using a streptavidin-biotin immunoperoxidase technique) of tissue specimens, obtained by excisional biopsy and partial or total mastectomy, from 62 patients with breast lesions. Specimens were obtained from 64 lesions as follows: fibrocystic disease (n=12), intraductal papilloma (n=4), fibroadenoma (n=17), invasive lobular carcinoma (n=6), invasive ductal carcinoma (n=20) and invasive micropapillary carcinoma (n=5). In normal breast tissue (controls), CD34-positive spindle cells were abundant in the intralobular stroma, but no ASMA-positive stromal cells were identified except myoepithelial cells. Small to large numbers of CD34-positive cells were observed in the stroma of 29 of 33 benign diseases. In all invasive carcinomas (lobular, ductal and micropapillary), no CD34-positive stromal cells were observed in the stroma. In the stroma of benign lesions, the number of ASMA-positive stromal cells was various, but the stroma of all invasive breast cancers contained ASMA-positive stromal cells. The present results indicate that disappearance of CD34-positive stromal cells consistently occurs in the stroma of invasive carcinoma of the breast, irrespective of histological type and may be associated with the presence of ASMA-positive stromal cells.     

Reversal of myofibroblasts by amniotic membrane stromal extract

Myofibroblasts play an important role in morphogenesis, inflammation, and fibrosis in most tissues. The amniotic membrane stroma can maintain keratocytes in cultures and prevent them from differentiating into myofibroblasts. However, it is unknown whether the AM stroma can also reverse differentiated myofibroblasts. In this study, we found that amniotic membrane stromal cells (AMSCs), which adopted fibroblastic phenotype in vivo, quickly and completely differentiated into myofibroblasts during ex vivo culture in DMEM/FBS on plastic within 2 passages. When cultured on type I collagen, the myofibroblasts maintained their phenotype, however, when these myofibroblasts were re-seeded onto a cryopreserved amniotic membrane stromal surface, they reversed to the fibroblast phenotype. Moreover, we found that the amniotic membrane stromal extract not only helps maintain primary AMSCs fibroblastic phenotype in vitro, but also can reverse differentiated myofibroblasts back to fibroblasts. This reversal was not coupled with cell proliferation. We concluded that the amniotic membrane stroma contains soluble factors that can regulate the mesenchymal cell differentiation. Further investigation into the identity of these factors and the control mechanisms may unravel a new scar-reversing strategy.     

Effect of nitric oxide on the differentiation of fibroblasts into myofibroblasts in the Peyronie’s fibrotic plaque and in its rat model

The myofibroblast shares phenotypic features of both fibroblasts and smooth muscle cells. It plays a critical role in collagen deposition and wound healing and disappears by apoptosis when the wound is closed. Its abnormal persistence leads to hypertrophic scar formation and other fibrotic conditions. Myofibroblasts are present in the fibrotic plaque of the tunica albuginea (TA) of the penis in men with Peyronie's disease (PD), a localized fibrosis that is accompanied by a spontaneous induction of the inducible nitric oxide synthase (iNOS), also observed in the TGFbeta1-elicited, PD-like lesion in the rat model. iNOS expression counteracts fibrosis, by producing nitric oxide (NO) that reduces collagen deposition in part by neutralization of profibrotic reactive oxygen species. In this study we investigated whether fibroblast differentiation into myofibroblasts is enhanced in the human and rat PD-like plaque and in cultures of human tissue fibroblasts. We also examined whether NO reduces this cell differentiation and collagen synthesis. The myofibroblast content in the fibroblast population was measured by quantitative immunohistochemistry as the ratio between alpha-smooth muscle actin (ASMA; myofibroblast marker) and vimentin (general fibroblast marker) levels. We found that myofibroblast content was considerably increased in the human and TGFbeta1-induced rat plaques as compared to control TA. Inhibition of iNOS activity by chronic administration of L-iminoethyl-L-lysine to rats with TGFbeta1-induced TA lesion increased myofibroblast abundance and collagen I synthesis measured in plaque and TA homogenates from animals injected with a collagen I promoter construct driving the expression of beta-galactosidase. Fibroblast differentiation into myofibroblasts occurred with passage in the cell cultures from the human PD plaque, but was minimal in cultures from the TA. Induction of iNOS in PD and TA cultures with a cytokine cocktail and a NO donor, S-nitroso-N-acetyl penicillamine (SNAP), was detected by immunohistochemistry. Both treatments reduced the total number of cells and the number of ASMA positive cells, whereas only SNAP decreased collagen I immunostaining. These results support the hypotheses that myofibroblasts play a role in the development of the PD plaque and that the antifibrotic effects of NO may be mediated at least in part by the reduction of myofibroblast abundance and lead to a reduction in collagen I synthesis.     

Human marrow stromal precursors are alpha 1 integrin subunit-positive

In this work we studied the expression of adhesion molecules on primate human and non-human marrow stromal cells (primary cultures and lines) and on human CD34(+) hematopoietic normal and leukemic precursors. Differential expression of alpha1 integrin subunit was observed, since this molecule was intensely expressed by marrow stroma but not detected on CD34(+) cells. We used this difference to select, in fresh bone marrow samples, alpha 1-positive cells. We found that all stromal precursors giving rise to colony-forming units-fibroblasts (CFU-F) were present in the alpha 1-positive fraction. No colonies were detected in the alpha 1-negative fraction even after 2 weeks of culture. Phenotypic studies of stromal cells derived from alpha1-positive cells and grown in long-term marrow culture indicated that these cells were similar to stromal cells from primary cultures. We also observed early upregulation of alpha 4 and alpha 2 integrin subunits in cultures derived from alpha1-positive cells with maximal expression by day 10 (26 and 51%, respectively) preceding a gradual decline to low to nil values at day 30 (4.5 and 12%). These data indicate that alpha 1 integrin subunit is a marker for both mature stromal cells and stromal precursors, while alpha 2 and alpha 4 integrin subunits are expressed primarily by immature cells.     

Proliferation of myofibroblasts in the stroma of renal oncocytoma

Objectives: Myofibroblasts are a vital component of stroma of many malignant neoplasms, but it is not yet established whether stromal myofibroblasts also exist in benign tumours such as oncocytoma of the kidney. Materials and methods: Histomorphological and immunohistochemical analysis of 16 renal oncocytomas diagnosed at Chang Gung Memorial Hospital, Taiwan, has been performed. Results: Renal oncocytomas were composed of oncocytes, large cells with granular eosinophilic cytoplasm, arranged mostly in sheets, in tubulocystic or combined pattern. Few oncocytes appeared to be undergoing proliferation or apoptosis. MIB‐1 and active caspase 3 indices were low, but higher in tumour than in surrounding non‐tumour parenchyma (MIB‐1: 0.93 ± 0.09 versus 0.46 ± 0.07, P < 0.001 and active caspase 3: 0.76 ± 0.08 versus 0.41 ± 0.09, P < 0.001). Wnt/β‐catenin signalling was not implicated in this neoplasm, as there was no loss of E‐cadherin membranous localization or expression of intranuclear β‐catenin in the cells. Clumps of oncocytes were stained with periodic acid Schiff and had collagen I‐, collagen III‐ and fibronectin‐positive, but desmin‐ and human caldesmon‐negative stromas. Importantly, α‐smooth muscle actin (SMA)‐immunostaining established the myofibroblastic nature of many of the stromal cells. Some of the myofibroblasts were also positive for MIB‐1, indicating a proliferative role for them in the stroma. Conclusions: Renal oncocytomas were composed of two independent compartments: benign oncocytes and pronounced fibrotic stroma, which consisted of proliferating myofibroblasts (SMA‐ and MIB‐1‐positive) which were associated with excessive deposition of extracellular matrix (periodic acid Schiff‐component, collagen I‐, collagen III‐ and fibronectin‐positive, and desmin‐ and human caldesmon‐negative).     

Kinetics and collagenolytic role of eosinophils in chronic gastric ulcer in the rat

 An association between eosinophils and tissue damage has been observed in numerous disorders. However, few reports have addressed the role of infiltrating eosinophils in gastric ulcer healing. The aim of this study was to investigate the kinetics and role of eosinophils infiltrating experimental chronic gastric ulcers in the rat. We developed a monoclonal antibody against human matrix metalloproteinase 1 (MMP1) purified from conditioned culture medium of human skin fibroblasts. Acetic acid-induced gastric ulcers were resected from rats on days 1, 3, 5, 10, 20, 40, and 180 after the days of induction (day 0). Tissue specimens were immunostained with this antibody and examined with an electron microscope. Few eosinophils were observed in the granulation tissue until day 20. By days 40 and 180, MMP1-positive eosinophils had increased in the granulation tissue of open ulcers. Azan staining revealed dispersed collagen fibers around infiltrating eosinophils. In contrast, scars demonstrated few eosinophils in fibrous tissue on days 40 and 180. Eosinophils which express MMP1 infiltrate granulation tissue at the chronic stage of gastric ulceration. The results suggest that eosinophils may play a role in tissue remodeling and deterioration of ulceration. Accepted: 18 March 1997     

Subepithelial myofibroblasts are novel nonprofessional APCs in the human colonic mucosa

The human gastrointestinal mucosa is exposed to a diverse normal microflora and dietary Ags and is a common site of entry for pathogens. The mucosal immune system must respond to these diverse signals with either the initiation of immunity or tolerance. APCs are important accessory cells that modulate T cell responses which initiate and maintain adaptive immunity. The ability of APCs to communicate with CD4+ T cells is largely dependent on the expression of class II MHC molecules by the APCs. Using immunohistochemistry, confocal microscopy, and flow cytometry, we demonstrate that alpha-smooth muscle actin(+), CD90+ subepithelial myofibroblasts (stromal cells) constitutively express class II MHC molecules in normal colonic mucosa and that they are distinct from professional APCs such as macrophages and dendritic cells. Primary isolates of human colonic myofibroblasts (CMFs) cultured in vitro were able to stimulate allogeneic CD4+ T cell proliferation. This process was dependent on class II MHC and CD80/86 costimulatory molecule expression by the myofibroblasts. We also demonstrate that CMFs, engineered to express a specific DR4 allele, can process and present human serum albumin to a human serum albumin-specific and DR4 allele-restricted T cell hybridoma. These studies characterize a novel cell phenotype which, due to its strategic location and class II MHC expression, may be involved in capture of Ags that cross the epithelial barrier and present them to lamina propria CD4+ T cells. Thus, human CMFs may be important in regulating local immunity in the colon.     

The participation of myofibroblasts in the capsular formation of human conventional and chromophobe renal cell carcinomas

The presence of myofibroblasts has been elucidated in neoplastic capsules of various organs. In the present article, we examine the presence of myofibroblasts in the capsule of renal cell carcinoma (RCC) and discuss the origin of the myofibroblasts. Nineteen renal tumors (conventional RCC, n=17; chromophobe RCC, n=2) with evident and totally surrounded fibrous capsule were selected. Abundant myofibroblasts were immunohistochemically observed in the capsule of the RCCs. These findings were confirmed by electron and immunoelectron microscopic studies of three conventional RCCs. Type III and I collagens were predominant in the outer and inner layers of the RCC capsule, respectively. The cytoplasm of the tubular epithelial cells in the tissue surrounding the neoplastic capsule stained positively for transforming growth factor (TGF)-beta 1. In situ hybridization detected type I collagen mRNA in myofibroblasts of the capsule. Myofibroblasts may participate in the capsular formation of conventional and chromophobe RCCs through the collagen production.     

Antifibrotic properties of caveolin-1 scaffolding domain in vitro and in vivo

Lung fibrosis involves the overexpression of ECM proteins, primarily collagen, by alpha-smooth muscle actin (ASMA)-positive cells. Caveolin-1 is a master regulator of collagen expression by cultured lung fibroblasts and of lung fibrosis in vivo. A peptide equivalent to the caveolin-1 scaffolding domain (CSD peptide) inhibits collagen and tenascin-C expression by normal lung fibroblasts (NLF) and fibroblasts from the fibrotic lungs of scleroderma patients (SLF). CSD peptide inhibits ASMA expression in SLF but not NLF. Similar inhibition of collagen, tenascin-C, and ASMA expression was also observed when caveolin-1 expression was upregulated using adenovirus. These observations suggest that the low caveolin-1 levels in SLF cause their overexpression of collagen, tenascin-C, and ASMA. In mechanistic studies, MEK, ERK, JNK, and Akt were hyperactivated in SLF, and CSD peptide inhibited their activation and altered their subcellular localization. These studies and experiments using kinase inhibitors suggest many differences between NLF and SLF in signaling cascades. To validate these data, we determined that the alterations in signaling molecule activation observed in SLF also occur in fibrotic lung tissue from scleroderma patients and in mice with bleomycin-induced lung fibrosis. Finally, we demonstrated that systemic administration of CSD peptide to bleomycin-treated mice blocks epithelial cell apoptosis, inflammatory cell infiltration, and changes in tissue morphology as well as signaling molecule activation and collagen, tenascin-C, and ASMA expression associated with lung fibrosis. CSD peptide may be a prototype for novel treatments for human lung fibrosis that act, in part, by inhibiting the expression of ASMA and ECM proteins.     

Gene expression study of monocytes/macrophages during early foreign body reaction and identification of potential precursors of myofibroblasts

Foreign body reaction (FBR), initiated by adherence of macrophages to biomaterials, is associated with several complications. Searching for mechanisms potentially useful to overcome these complications, we have established the signaling role of monocytes/macrophages in the development of FBR and the presence of CD34(+) cells that potentially differentiate into myofibroblasts. Therefore, CD68(+) cells were in vitro activated with fibrinogen and also purified from the FBR after 3 days of implantation in rats. Gene expression profiles showed a switch from monocytes and macrophages attracted by fibrinogen to activated macrophages and eventually wound-healing macrophages. The immature FBR also contained a subpopulation of CD34(+) cells, which could be differentiated into myofibroblasts. This study showed that macrophages are the clear driving force of FBR, dependent on milieu, and myofibroblast deposition and differentiation.