The cellular derivation and the life span of the myofibroblast

A comparison of pathomolecular markers of fibrosis and morphology in kidney from autopsies of African Americans and whites

African Americans have an increased incidence of chronic kidney disease (CKD) due to hypertension and arteriosclerosis and increased death due to coronary artery disease, compared with whites. The pathogenesis of CKD involves the increased presence and activation of myofibroblasts and macrophages, promotion of tubulointerstitial fibrosis, and effects of tubulointerstitial cell mitosis and apoptosis. We hypothesized that increased risk of hypertensive vascular disease may be identified by renal pathomolecular markers that are associated with progressive CKD. Renal sections were available from 50 autopsies of 33 African Americans (55% males) and 17 whites (76% males) undergoing forensic autopsy for unexpected death. Sclerotic glomeruli, severity of cortical fibrosis, and renal arteriolosclerosis, total glomerular number (N (glom)), average glomerular volume (V (glom)), birth weights, and blood pressure were known. Presence and locality of markers for myofibroblasts (alpha-SMA), macrophages (CD68), collagen, pro-fibrotic transforming growth factor-beta1 were scored in renal autopsies, and tubulointerstitial apoptosis was recorded. The results demonstrated a strong positive correlation between age, cortical fibrosis and alpha-SMA (p<0.05), and between CD68 and hypertension and coronary artery disease (p<0.05). The findings confirm the role of myofibroblasts and macrophages in pathogenesis of human CKD. However, the markers showed no significant relationships to V (glom), N (glom), birth weight, or race.

The mechanistic basis of infarct healing

Myocardial infarction triggers an inflammatory cascade that results in healing and replacement of the damaged tissue with scar. Cardiomyocyte necrosis triggers innate immune mechanisms eliciting Toll-like receptor- mediated responses, activating the complement cascade and generating reactive oxygen species. Subsequent activation of NF-kappaB is a critical element in the regulation of cytokine, chemokine, and adhesion molecule expression in the ischemic myocardium. Chemokine induction mediates leukocyte recruitment in the myocardium. Pleiotropic proinflammatory cytokines, such as TNF-alpha, IL-1, and IL-6, are also upregulated in the infarct and exert a wide range of effects on a variety of cell types. Timely repression of proinflammatory gene synthesis is crucial for optimal healing; IL-10 and TGF-beta-mediated pathways may be important for suppression of chemokine and cytokine expression and for resolution of the leukocytic infiltrate. In addition, TGF-beta may be critically involved in inducing myofibroblast differentiation and activation, promoting extracellular matrix protein deposition in the infarcted area. The composition of the extracellular matrix plays an important role in regulating cell behavior. Both structural and matricellular proteins modulate cell signaling through interactions with specific surface receptors. The molecular and cellular changes associated with infarct healing directly influence ventricular remodeling and affect prognosis in patients with myocardial infarction.

Low-grade myofibroblastic sarcoma of the parapharyngeal space

Low-grade myofibroblastic sarcoma was recently described as representing malignant mesenchymal tumours that show myofibroblastic differentiation; few cases have been reported. Here, a low-grade myofibroblastic sarcoma of the parapharyngeal space is described. A 42-year-old man presented with swelling on the right side of the temporal bone. Based on histological and immunohistochemical features, the diagnosis of low-grade myofibroblastic sarcoma was established. The tumour had invaded the orbit and the brain, and therefore surgical excision was not possible. There are thought to have been no cases affecting this region reported previously in the English-language literature.

Intramandibular inflammatory myofibroblastic tumor--a true neoplasm or reactive lesion?

OBJECTIVE

Inflammatory myofibroblastic tumor (IMT) is an uncommon lesion reported to arise in various organs and by convention believed to be a nonneoplastic reactive inflammatory condition. Because of its radiographic and histologic similarities to malignancy, IMT can pose a considerable diagnostic dilemma. The purpose of this study is to report the first intramandibular IMT and to discuss the possible nature of this lesion.

STUDY DESIGN

Detailed documentation of clinical, radiographic, and histologic features; literature review.

RESULTS

This lesion showed distinct radiographic, histologic, and immunohistochemical features. The lesion recurred 14 months after initial removal with almost identical histology.

CONCLUSION

This is the first documented case of an intramandibular IMT. Due to the rarity of these lesions, their clinical sequelae and prognosis are undetermined. As a result of specific immunohistochemical phenotyping and clinical behavior of this lesion, we favored a diagnosis of inflammatory myofibroblastic tumor. Wide excision with a long-term clinical follow-up is required.

Oral inflammatory myofibroblastic tumor demonstrating ALK, p53, MDM2, CDK4, pRb, and Ki-67 immunoreactivity in an elderly patient

Inflammatory myofibroblastic tumor (IMT) is a controversial lesion composed of myofibroblasts, accompanied by varying numbers of inflammatory cells. Various pathogenetic factors have been proposed (ie, reactive, infectious, autoimmune, and neoplastic) but the etiology of most IMTs remains unknown. Here we review the literature of oral IMTs, detailing the demographic profile of these rare lesions. Moreover, we present an unusual case of IMT arising from the mandibular alveolar mucosa of an 82-year-old female. Microscopic examination revealed plump spindle cells set in a myxoid vascular stroma admixed with inflammatory cells. Numerous large ganglion cell-like cells were seen, some exhibiting emperipolesis of neutrophils. Ultrastructurally, prominent myofibroblasts with abundant rough endoplasmic reticulum were noted. Tumor cells were immunoreactive for vimentin, smooth muscle actin, and KP1 (CD68), and negative for desmin, S-100, and EBV-LMP. The lesion was excised without margins and the patient has manifested no evidence of disease at an 18-month recall. In an attempt to further delineate the potential neoplastic nature of this lesion, we assessed the immunohistochemical expression of various markers that have been linked to neoplastic transformation. The recorded positivity for ALK, p53, MDM2, CDK4, pRb, and Ki-67, despite the absence of bcl-2 reactivity, strongly favors the neoplastic origin of the studied tumor.

Low-grade sarcomas with CD34-positive fibroblasts and low-grade myofibroblastic sarcomas

A subset of low-grade fibrosarcomas is composed of CD34-positive spindle cells. These include dermatofibrosarcoma, its morphologic variants, and its associated fibrosarcoma, solitary fibrous tumor, hemangiopericytoma and their malignant counterparts, and some cases of myxoinflammatory fibroblastic sarcoma. Dermatofibrosarcoma and related lesions are characterized by a t(17;22)(q22;q13) rearrangement resulting in fusion of the genes COL1A (17q21-22) and PDGFB1 (22q13). Solitary fibrous tumor displays varying cellularity and fibrosis and a peripheral hemangiopericytomatous pattern; most tumors formerly called hemangiopericytoma are now subsumed into the category of solitary fibrous tumor, although a few strictly defined examples are recognized; however, these are probably not composed of pericytes. Myofibroblastic malignancies are best identified by electron microscopy, with which varying degrees of differentiation, including the presence of fibronexus junctions, can be identified. Low-grade sarcomas showing myofibroblastic differentiation include myofibrosarcomas and inflammatory myofibroblastic tumors. Myofibrosarcomas are spindle cell neoplasms that occur in children or adults in the head and neck, trunk, and extremities as infiltrative neoplasms and that display a fascicular or fasciitis-like pattern with focal nuclear atypia and variable expression of myoid antigens. These sarcomas are prone to recurrence and a small number metastasize. Inflammatory myofibroblastic tumor (synonymous with inflammatory fibrosarcoma) is a neoplasm arising predominantly in childhood, and frequently in intraabdominal locations. It has spindle cells in fascicular, fasciitis-like and sclerosing patterns, with heavy chronic inflammation including abundant plasma cells. Many IMT have clonal chromosomal abnormalities involving 2p22-24, and fusion of the ALK gene with tropomyosin 3 (TPM3-ALK) or tropomyosin 4 (TPM4-ALK) is found in a subset.

Expression of CD34, alpha-smooth muscle actin, and transforming growth factor beta1 in squamous intraepithelial lesions and squamous cell carcinoma of the larynx and hypopharynx

AIM OF THE STUDY

There is increasing evidence that stromal reaction in cancer has an important diagnostic and prognostic significance. Recent studies have shown that CD34-positive stromal cells and myofibroblasts may play an important role in host response to invasive cancer. The aim of our study was to analyze the expression of CD34, alpha-smooth muscle actin (SMA), and transforming growth factor beta1 (TGFbeta1) in squamous intraepithelial lesions (SILs) and squamous cell carcinoma (SCC) of the larynx and hypopharynx, to establish their significance, and to elucidate the mechanism of myofibroblast formation.

METHODS

Immunohistochemistry was performed on samples of 42 resected larynges and 12 laryngeal biopsies of SILs and SCC using antibodies against SMA, CD34, CD31, TGFbeta1, and TGFbeta1 receptors. The expression of TGFbeta1 mRNA was detected with RNA in situ hybridization using specific oligonucleotides for TGFbeta1.

RESULTS

The stroma in normal laryngeal mucosa and SILs contained scattered CD34-positive cells, but there were no SMA-positive myofibroblasts. In contrast, the stroma of SCC contained SMA-positive myofibroblasts, but there were no CD34-positive stromal cells. This pattern of stromal reaction was also observed in the peritumoral zone. In adjacent normal tissue, there were CD34-positive stromal cells and no myofibroblasts. We found more intense TGFbeta1 expression in carcinoma cells than in the normal laryngeal epithelium and positive staining for both TGFbeta1 receptors on stromal cells of the normal mucosa. In SCC, many myofibroblasts expressed TGFbeta1 and both receptors for TGFbeta1. Expression of TGFbeta1 mRNA was similar to expression of TGFbeta1 protein.

CONCLUSION

Our study shows that disappearance of CD34-positive stromal cells and appearance of SMA-positive stromal myofibroblasts are associated with transformation of laryngeal SILs to SCC. This pattern of stromal reaction was found not only in the tumor but also in the peritumoral zone, defined as a band of host tissue between the invasive tumor front and adjacent normal tissue. Our findings also support the suggestion that overproduced TGFbeta1 in carcinoma cells mediates one of the mechanisms of transformation of stromal cells to myofibroblasts in laryngeal carcinogenesis.

Myofibroblastic malignancies

Malignant tumors composed of myofibroblasts are increasingly being recognized, but their existence remains controversial. Currently accepted examples within this category represent spindle cell or pleomorphic neoplasms of the soft tissues with a spectrum of histological grades. Low- and intermediate-grade myofibrosarcomas are fascicular spindle cell neoplasms resembling fibrosarcoma or leiomyosarcoma. They infiltrate deep soft tissue with disproportionate involvement of head and neck sites and can recur locally but infrequently metastasize. They variably express myoid immunohistochemical markers, and their differential diagnosis includes benign myofibroblastic proliferations such as fasciitis and fibromatosis as well as other types of spindle cell sarcoma. High-grade (pleomorphic) myofibrosarcomas are an ultrastructurally defined subset of malignant fibrous histiocytoma, which they resemble in morphology and behavior. Inflammatory myofibroblastic tumor and infantile fibrosarcoma are neoplasms that have myofibroblastic features and have been included in this category, but they have distinctive genetic findings. This article reviews the concept of myofibrosarcoma and describes its variants.

Valvular myofibroblast activation by transforming growth factor-beta: implications for pathological extracellular matrix remodeling in heart valve disease

The pathogenesis of cardiac valve disease correlates with the emergence of muscle-like fibroblasts (myofibroblasts). These cells display prominent stress fibers containing alpha-smooth muscle actin (alpha-SMA) and are believed to differentiate from valvular interstitial cells (VICs). However, the biological factors that initiate myofibroblast differentiation and activation in valves remain unidentified. We show that transforming growth factor-beta1 (TGF-beta1) mediates differentiation of VICs into active myofibroblasts in vitro in a dose-dependent manner, as determined by a significant increase in alpha-SMA and the dramatic augmentation of stress fiber formation and alignment. Additionally, TGF-beta1 and increased mechanical stress function synergistically to enhance contractility. In turn, contractile valve myofibroblasts exert tension on the extracellular matrix, resulting in a dramatic realignment of extracellular fibronectin fibrils. TGF-beta1 also inhibits valve myofibroblast proliferation without enhancing apoptosis. Our results are consistent with activation of a highly contractile myofibroblast phenotype by TGF-beta1 and are the first to connect valve myofibroblast contractility with pathological valve matrix remodeling. We suggest that the activation of contractile myofibroblasts by TGF-beta1 may be a significant first step in promoting alterations to the valve matrix architecture that are evident in valvular heart disease.

Myofibrosarcoma

Myofibrosarcomas are malignant tumours of myofibroblasts, which have been recognised for many years, but have become clearly defined only recently. They are low- or high-grade sarcomas that arise in soft tissue or bone in adults or children. Low-grade myofibrosarcomas are infiltrative tumours, usually in deep soft tissue, with a predilection for the head and neck region, which display a range of microscopic appearances from fasciitis-like to fibrosarcoma-like; all cases at least focally display nuclear pleomorphism. They express smooth-muscle actin and calponin, and some express desmin, but most lack h-caldesmon. Low-grade myofibrosarcomas can recur but rarely metastasise. Their differential diagnosis is from benign myofibroblastic proliferations, such as fasciitis and fibromatosis, as well as from fibrosarcoma and leiomyosarcoma. Pleomorphic myofibrosarcomas are high-grade pleomorphic sarcomas (malignant fibrous histiocytoma), which show ultrastructural evidence of myofibroblastic differentiation. They closely resemble malignant fibrous histiocytoma clinically and morphologically, but are more frequently actin positive. This article describes the low- and high-grade variants of myofibrosarcoma and other malignant tumours with myofibroblastic differentiation.

Differential expression of CRABP-II in fibroblasts derived from dermis and subcutaneous fat

We have shown previously that fibroblasts derived from fat or dermal tissue differ in their functional properties, such as proliferation rate and contractile properties. To study these differences further, two-dimensional electrophoresis (2D PAGE) was performed on proteins isolated from cultured subcutaneous fat and dermal fibroblasts. The 2D gels were screened for proteins that were differentially expressed in all donors (n = 5). Five protein spots were subjected to further analysis by mass spectrometry. Two proteins could be identified: brain acid soluble protein 1 (BASP1) and cellular retinoic acid binding protein-II (CRABP-II). CRABP-II is of interest in terms of re-epithelialisation and was clearly expressed in dermal fibroblasts but not in fat fibroblasts. Real time PCR was performed to confirm the 2D data on CRABP-II. The CRABP-II mRNA level was significantly increased in dermal tissue and cultured dermal fibroblasts compared to fat tissue and cultured fat-derived fibroblasts, respectively. The mode of action of CRABP-II in skin is to mediate retinoic acid activity. Retinoic acid is known to inhibit migration and to stimulate differentiation of keratinocytes. The expression of CRABP-II by dermal fibroblasts implicates a role for these fibroblasts in wound re-epithelialisation, in contrast to subcutaneous fat-derived fibroblasts.

The Effect of Myofibroblast on Contracture of Hypertrophic Scar

Wound contraction in humans has both positive and negative effects. It is beneficial to wound healing by narrowing the wound margins, but the formation of undesirable scar contracture brings cosmetic and even functional problems. The entire mechanism of wound healing and scar contracture is not clear yet, but it is at least considered that both the fibroblasts and the myofibroblasts are responsible for contraction in healing wounds. The myofibroblast is a cell that possesses all the morphologic and biochemical characteristics of both a fibroblast and a smooth muscle cell. Normally, the myofibroblasts appear in the initial wound healing processes and generate contractile forces to pull both edges of an open wound until it disappears by apoptosis. But as an altered regulation of myofibroblast disappearance, they remain in the dermis and continuously contract the scar, eventually causing scar contracture. In this research, to compare and directly evaluate the influence on scar contracture of the myofibroblast versus the fibroblast, dermal tissues were taken from 10 patients who had highly contracted hypertrophic scars. The myofibroblasts were isolated and concentrated from the fibroblasts using the magnetic activating cell-sorting column to obtain the myofibroblast group, which contained about 28 to 41 percent of the myofibroblasts, and the fibroblast group, which contained less than 0.9 percent of the myofibroblasts. Each group was cultured in the fibroblast-populated collagen lattice for 13 days, and the contraction of the collagen gel was measured every other day. In addition, they were selectively treated with tranilast [N-(3',4'-dimethoxycinnamoyl) anthranilic acid] to evaluate the influence on the contraction of the collagen gel lattice. During the culture, the myofibroblast group, compared with the fibroblast group, showed statistically significant contraction of the collagen gel lattice day by day, except on the first day, and only the myofibroblast group was affected by tranilast treatment, showing significant inhibition of gel contraction. By utilizing an in vitro model, the authors have demonstrated that myofibroblasts play a more important role in the contracture of the hypertrophic scar.

Myofibroblast and endothelial cell proliferation during murine myocardial infarct repair

Granulation tissue formation is a critical step in infarct repair, however, the kinetics of cell replication and the molecules that regulate this process are poorly understood. In uninjured mouse hearts and at 2 days post-infarction, very little DNA synthesis (measured by incorporation of a BrdU pulse) was detected in any cell type. Four days after permanent coronary occlusion, the rates of myofibroblast (smooth muscle alpha-actin and BrdU double-positive) and endothelial cell (CD31 and BrdU double-positive) proliferation were 15.4 +/- 1.1% and 2.9 +/- 0.5%, respectively. Most proliferating cells were located at the interface of the infarct and viable tissue. By 1 week, fibroblast and endothelial cell proliferation declined to 4.1 +/- 0.6% and 0.7 +/- 0.1%, respectively. In the 2-week infarct, the remaining necrosis had been phagocytosed, and fibroblast and endothelial cell proliferation were <0.5%. Although leukocytes were abundant throughout infarct repair, no significant proliferation was detected at any time in cells expressing CD45 or mac-3. Infarct size at 4 days was 38 +/- 5% of the left ventricle and contracted to 20 +/- 4% by 4 weeks. After 4 days, the chamber dilated to four times that of the control hearts and remained so for the duration of the time course. The vascular density (per mm(2)) declined from 3643 +/- 82 in control hearts to 2716 +/- 197 at 1 week and 1010 +/- 47 at 4 weeks post-myocardial infarction (MI). The average percent area occupied by vessels did not change significantly between the groups but the area/vessel ( micro m(2)) increased from 14.1 +/- 0.3 in control hearts to 16.9 +/- 1.9 at 1 week and 38.7 +/- 7.9 at 4 weeks post-MI. These data indicate that mitogens for fibroblasts and endothelial cells peak within 4 days of infarction in the mouse heart. This provides the basis for identifying the responsible molecules and developing strategies to alter wound repair and improve cardiac function.

Function and regulation of melanoma-stromal fibroblast interactions: when seeds meet soil

Melanoma development and progression not only involve genetic and epigenetic changes that take place within the melanocytic cells, but also involve processes that are determined collectively by contextual factors including intercellular adhesions and communications. In this review, we focus on melanoma-stromal fibroblast crosstalk by direct cell-cell contact and by growth factors/cytokines/chemokines interacting with their respective receptors. The interactions between melanoma cells and stromal fibroblasts create a context that promotes tumor growth, migration/invasion, and angiogenesis. An understanding of this process and developing new experimental and screening models are of great importance for the development of effective therapeutical strategies to treat melanoma.

CNP gene expression is activated by Wnt signaling and correlates with Wnt4 expression during renal injury

C-type natriuretic peptide (CNP) regulates salt excretion, vascular tone, and fibroblast proliferation and activation. CNP inhibits fibroblast activation in vitro and fibrosis in vivo, but endogenous CNP gene (Nppc) expression during tissue fibrosis has not been reported. We determined that Nppc is induced in renal tubular epithelia and then in interstitial myofibroblasts after unilateral ureteral obstruction (UUO). Induction of Nppc occurred in identical cell populations to those in which Wnt4 is induced after renal injury. In addition, Nppc was activated in Wnt4-expressing cells during nephrogenesis. Wnt signaling components beta-catenin and T cell factor/lymphoid enhancer binding factor (TCF/LEF) specifically bound to cognate elements in the Nppc proximal promoter. Wnt-4, beta-catenin, and LEF-1 activated an Nppc transgene in cultured cells, and transgene activation by Wnt-4 and LEF-1 was dependent on the presence of intact cognate elements. These findings suggest that Wnt-4 stimulates Nppc in a TCF/LEF-dependent manner after renal injury and thus may contribute to limiting renal fibrosis.

Regulation of cell growth and the expression of extracellular matrix proteins in colorectal adenocarcinoma: a fibroblast-tumor cell coculture model to study tumor-host interactions in vitro

The production of abundant connective tissue within malignant tumors, the so-called desmoplastic stromal reaction, is a hallmark of colorectal adenocarcinomas. This stroma is produced to a large extent by myofibroblasts and contains various amounts of collagens (type I, III, and V), chondroitin sulfate proteoglycan, hyaluronic acid, fibronectin, and tenascin-C. In this study we have established a monolayer coculture model between two different colorectal adenocarcinoma cell lines (HRT-18, and CX-2) and colonic fibroblasts (CCD-18) to investigate the mechanisms regulating (i) the production of extracellular matrix (ECM) components, (ii) the induction of myofibroblastic differentiation, and (iii) cellular proliferation. We found that TGFbeta1 and FGF-2 stimulated ECM synthesis of fibroblasts. Myofibroblastic differentiation was stimulated by TGFbeta1 but suppressed by FGF-2. There was a mutual stimulation of proliferation between fibroblasts and carcinoma cells. The analogies with ECM components expressed in cocultures and colorectal adenocarcinoma samples suggest that the coculture model used in this study is useful to study tumor cell-fibroblast interactions.

Gene expression in Peyronie's disease

Currently, surgical intervention is the only efficacious treatment for Peyronie's disease (PD), a fibromatosis of the tunica albuginea of the penis. Therapies based on the molecular pathways for this disease could provide alternatives to surgical treatment but only recently has the pathophysiology of the Peyronie's disease plaque been investigated at the molecular level. In this review, we examine the current knowledge of gene expression in the PD plaque and the relationship of PD with other fibrotic conditions such as Dupytren's disease. TGFbeta1, along with other growth factors, pro-fibrotic genes, and collagen, are expressed in fibroblasts and myofibroblasts. Myofibroblasts are normally involved in wound contracture and largely eliminated via apoptosis during the late stages of wound remodeling. In the PD plaque, however, these cells persist and may play an important role in the PD plaque fibrosis. The expression levels of TGFbeta1 and pro- and anti-fibrotic gene products, along with the nitric oxide/reactive oxygen species (NO/ROS) ratio in the tunica albuginea, appear to be essential for the formation and progression of the PD plaque and effect the expression of multiple genes. This can be assessed with the recently developed DNA-based chip arrays and results with the PD plaque have been encouraging. OSF-1 (osteoblast recruitment), MCP-1 (macrophage recruitment), procollagenase IV (collagenase degradation), and other fibrotic genes have been identified as being possible candidate regulatory genes. Finally, possible therapeutic avenues for gene-based therapy in the treatment of PD are discussed that may eventually reduce the need for surgical intervention.

Rat liver myofibroblasts and hepatic stellate cells differ in CD95-mediated apoptosis and response to TNF-alpha

Hepatic stellate cells (HSC), particularly activated HSC, are thought to be the principle matrix-producing cell of the diseased liver. However, other cell types of the fibroblast lineage, especially the rat liver myofibroblasts (rMF), also have fibrogenic potential. A major difference between the two cell types is the different life span under culture conditions. Although nearly no spontaneous apoptosis could be shown in rMF cultures, 18 +/- 2% of the activated HSC (day 7) were apoptotic. Compared with activated HSC, CD95R was expressed in 70% higher amounts in rMF. CD95L could only be detected in activated HSC. Stimulation of the CD95 system by agonistic antibodies (1 ng/ml) led to apoptosis of all rMF within 2 h, whereas activated HSC were more resistant (5.3 h/ 40% of total cells). Although transforming growth factor-beta downregulated apoptosis in both activated HSC and rMF, tumor necrosis factor-alpha (TNF-alpha) upregulated apoptosis in rMF. Lack of spontaneous apoptosis and CD95L expression in rMF and the different reaction on TNF-alpha stimulation reveal that activated HSC and rMF belong to different cell populations.

The challenge of defining normality for human mitral and aortic valves: geometrical and compositional analysis

Advances in digital imaging technology and in tools for obtaining detailed quantitation of morphological features have facilitated a new approach to pathological assessment of many tissues, including heart valves. In the present study, we quantitatively examined the tissue geometry and composition of structurally normal mitral and aortic valves removed at autopsy or surgery from patients aged 15-84 years. Through univariate analyses of quantitative variables, we have determined which features change distinctively with age. The anterior mitral valve leaflet (AMV) underwent a statistically significant decrease in area of the valve proper and an increase in the number of superficial tissue accumulations called onlays as the patients aged. For all geometric variables measured in the aortic valve, increases were seen with age, leading to a thicker valve, with enlargement of the valve proper and onlays, and with changes in the number of onlays. The mitral valve proper, composed largely of collagen in younger individuals, showed significant increases in glycosaminoglycans and elastin and a relative decrease in collagen with age. The compositional characteristics of the aortic valve proper were similar to those of the mitral valve, with a dramatic relative increase in elastin and a decrease in collagen with age. Valve onlays, when present, were similar in composition to the valve proper for both valves. Our findings regarding normal valve tissue composition, when taken in the context of geometrical features, and together with evidence of age-related changes in the relative amounts of specific constituents, provide a basis on which to analyze human heart valves affected by various known or putative diseases.

The CXC chemokine cCAF stimulates precocious deposition of ECM molecules by wound fibroblasts, accelerating development of granulation tissue

BACKGROUND

During wound repair, fibroblasts orchestrate replacement of the provisional matrix formed during clotting with tenascin, cellular fibronectin and collagen III. These, in turn, are critical for migration of endothelial cells, keratinocytes and additional fibroblasts into the wound site. Fibroblasts are also important in the deposition of collagen I during scar formation. The CXC chemokine chicken Chemotactic and Angiogenic Factor (cCAF), is highly expressed by fibroblasts after wounding and during development of the granulation tissue, especially in areas where extracellular matrix (ECM) is abundant. We hypothesized that cCAF stimulates fibroblasts to produce these matrix molecules.

RESULTS

Here we show that this chemokine can stimulate precocious deposition of tenascin, fibronectin and collagen I, but not collagen III. Studies in culture and in vivo show that tenascin stimulation can also be achieved by the N-terminal 15 aas of the protein and occurs at the level of gene expression. In contrast, stimulation of fibronectin and collagen I both require the entire molecule and do not involve changes in gene expression. Fibronectin accumulation appears to be linked to tenascin production, and collagen I to decreased MMP-1 levels. In addition, cCAF is chemotactic for fibroblasts and accelerates their migration.

CONCLUSIONS

These previously unknown functions for chemokines suggest that cCAF, the chicken orthologue of human IL-8, enhances healing by rapidly chemoattracting fibroblasts into the wound site and stimulating them to produce ECM molecules, leading to precocious development of granulation tissue. This acceleration of the repair process may have important application to healing of impaired wounds.

Active interstitial remodeling: an important process in the hibernating human myocardium

OBJECTIVES

The purpose of this study is to investigate the morphologic characteristics of the cardiac interstitium in the hibernating human myocardium and evaluate whether active remodeling is present and is an important determinant of functional recovery.

BACKGROUND

Myocardial hibernation is associated with structural myocardial changes, which involve both the cardiomyocytes and the cardiac interstitium.

METHODS

We evaluated 15 patients with coronary disease with two-dimensional echocardiography and thallium-201 ((201)Tl) tomography before coronary bypass surgery. During surgery, transmural myocardial biopsies were performed guided by transesophageal echocardiography. Myocardial biopsies were stained immunohistochemically to investigate fibroblast phenotype and examine evidence of active remodeling in the heart.

RESULTS

Among the 29 biopsied segments included in the study, 24 showed evidence of systolic dysfunction. The majority of dysfunctional segments (86.4%) were viable ((201)Tl uptake > or = 60%). After revascularization, 12 dysfunctional segments recovered function as assessed with an echocardiogram three months after bypass surgery. Interstitial fibroblasts expressing the embryonal isoform of smooth muscle myosin heavy chain (SMemb) were noted in dysfunctional segments, predominantly located in border areas adjacent to viable myocardial tissue. Segments with recovery had higher SMemb expression (0.46 +/- 0.16% [n = 12] vs. 0.10 +/- 0.02% [n = 12]; p < 0.05) and a higher ratio of alpha-smooth muscle actin to collagen (0.14 +/- 0.026 [n = 12] vs. 0.07 +/- 0.01 [n = 12]; p < 0.05) compared with segments without recovery, indicating fibroblast activation and higher cellularity of the fibrotic areas. In addition, interstitial deposition of the matricellular protein tenascin, a marker of active remodeling, was higher in hibernating segments than in segments with persistent dysfunction (p < 0.05), suggesting an active continuous fibrotic process. Multiple logistic regression demonstrated a significant independent association between SMemb expression and functional recovery (p < 0.01).

CONCLUSIONS

Fibroblast activation and expression of SMemb and tenascin provide evidence of continuous remodeling in the cardiac interstitium of the hibernating myocardium, an important predictor of recovery of function after revascularization.

Differences in motility pattern between human buccal fibroblasts and periodontal and skin fibroblasts

Migration of fibroblasts from surrounding normal tissue into the wound bed is an important requirement for successful wound healing. This study investigated the motility pattern of buccal, periodontal and skin fibroblasts to determine whether differences in the wound healing efficiency at these sites can be explained by differences in the motile behavior of their respective fibroblast populations. The migratory characteristics were studied in a two-dimensional culture system. The migration of single cells was time-lapse video recorded at intervals of 15 min for a period of 6 h using a computer-assisted microscope work-station. For evaluation of cell morphology, cell contours were recognized semiautomatically and used for determination of cell area, cell spreading and number and length of processes. We found that the cellular displacement of the buccal fibroblasts was only approximately 50% of the cellular displacement of periodontal and skin fibroblasts. The decreased cellular displacement of the buccal fibroblasts was found to be due to both lower cellular speed and less persistence in direction. The buccal fibroblasts also displayed smaller areas and longer processes. The differences in cellular morphology and motility pattern amongst the three fibroblast types could not be explained by differences in secretion of extracellular matrix components and are therefore believed to reflect phenotypic differences amongst fibroblast subpopulations.

The cxc chemokine cCAF stimulates differentiation of fibroblasts into myofibroblasts and accelerates wound closure

Chemokines are small cytokines primarily known for their roles in inflammation. More recently, however, they have been implicated in processes involved in development of the granulation tissue of wounds, but little is known about their functions during this process. Fibroblasts play key roles in this phase of healing: some fibroblasts differentiate into myofibroblasts, alpha-smooth muscle actin (SMA)-producing cells that are important in wound closure and contraction. Here we show that the CXC chemokine chicken chemotactic and angiogenic factor (cCAF) stimulates fibroblasts to produce high levels of alpha-SMA and to contract collagen gels more effectively than do normal fibroblasts, both characteristic properties of myofibroblasts. Specific inhibition of alpha-SMA expression resulted in abrogation of cCAF-induced contraction. Furthermore, application of cCAF to wounds in vivo increases the number of myofibroblasts present in the granulation tissue and accelerates wound closure and contraction. We also show that these effects in culture and in vivo can be achieved by a peptide containing the NH2-terminal 15 amino acids of the cCAF protein and that inhibition of alpha-SMA expression also results in inhibition of N-peptide-induced collagen gel contraction. We propose that chemokines are major contributors for the differentiation of fibroblasts into myofibroblasts during formation of the repair tissue. Because myofibroblasts are important in many pathological conditions, and because chemokines and their receptors are amenable to pharmacological manipulations, chemokine stimulation of myofibroblast differentiation may have implications for modulation of functions of these cells in vivo.

Melanoma-stroma interactions: structural and functional aspects

Cutaneous melanomas are notorious for their tendency to metastasise. Because the tumour microenvironment plays an important part in tumour development and progression, we review the structural and functional aspects of interactions between melanoma and the stroma. We emphasise fibrovascular patterns (both in uveal and cutaneous melanoma), cellular and extracellular composition of the stroma, and the molecules involved. Also, we discuss functional interactions, focusing on melanoma-fibroblast cross-talk by soluble factors and by direct cell-cell contact. On the basis of recent findings we propose that involvement of fibroblasts in melanoma-stromagenesis occurs through different stages: recruitment, activation, and conversion to myofibroblasts, or differentiation to fibrocytes. We reason that this involvement is topographically linked to different areas in and around the tumour, and hypothesise that stromal activation, as seen in tumor ulceration or immunological regression in melanoma, stimulates tumour progression.

Reactive stroma in prostate cancer progression

PURPOSE

The development of an altered stromal microenvironment in response to carcinoma is a common feature of many tumors. We reviewed the literature describing characteristics of reactive stroma, how reactive stroma affects cancer progression and how carcinoma regulates reactive stroma. Moreover, we present a hypothesis of reactive stroma in prostate cancer and discuss how the biology of reactive stroma may be used in novel diagnostic and therapeutic approaches.

MATERIALS AND METHODS

An extensive literature search was performed to review reports of the general features of wound repair stroma, general stromal responses to carcinoma, and stromal biology of normal and prostate cancer tissues. These studies were analyzed and a reactive stroma hypothesis in prostate cancer was developed.

RESULTS

Modifications to the stroma of breast, colon and prostate tumors parallel the generation of granulation tissue in wound repair. These changes include stromal cell phenotypic switching, extracellular matrix remodeling and angiogenesis induction. Therefore, it is predicted that a modified wound healing response induces the formation of reactive stroma in cancer to create a tumor promoting environment. Based on its role in wound repair and its over expression in prostate cancer, transforming growth factor-beta stands out as a potential regulator of reactive stroma.

CONCLUSIONS

Reactive stroma in prostate cancer and granulation tissue in wound repair show similar biological responses and processes that are predicted to promote cancer progression. Further identification of specific functional and regulatory mechanisms in prostate cancer reactive stroma may aid in the use of reactive stroma for novel diagnostic and therapeutic approaches.

Tubular phenotypic change in progressive tubulointerstitial fibrosis in human glomerulonephritis

There is much debate over the origins of fibroblast-type cells that accumulate in interstitial fibrosis. A controversial hypothesis, supported by data from animal and cell-culture studies, is that fibroblast-type cells can derive from tubular epithelial cells by a process of epithelial-mesenchymal transdifferentiation. However, to date, no evidence supports this postulate in human glomerulonephritis. This study sought to provide evidence that tubular epithelial cells can undergo phenotypic change toward a fibroblast-like cell in human glomerulonephritis. One hundred twenty-seven open renal biopsy specimens from patients with minimal change disease (MCD), immunoglobulin A (IgA) nephropathy, and rapidly progressive glomerulonephritis (RPGN) were examined for tubular phenotypic change by two-color immunohistochemistry using the criteria of de novo expression of alpha-smooth muscle actin (alpha-SMA), a myofibroblast marker; loss of the epithelial marker cytokeratin; and collagen production. In normal human kidney and MCD, tubular epithelial cells expressed cytokeratin with no evidence of alpha-SMA staining. However, in 36 of 90 cases of IgA nephropathy and 9 of 18 cases of RPGN, small numbers of tubular epithelial cells in areas of fibrosis showed de novo alpha-SMA expression, accounting for 0.4% +/- 0.2% (IgA nephropathy) and 3.8% +/- 1.5% (RPGN) of cortical tubules. An intermediate stage of phenotypic change was observed in some cuboidal epithelial cells that expressed both cytokeratin and alpha-SMA. Tubules containing alpha-SMA-positive (alpha-SMA(+)) cells also stained for collagen types I and III, suggesting that tubular cells undergoing phenotypic change have an active role in the fibrotic process. There also was a marked increase in transforming growth factor-beta1 (TGF-beta1) tubular expression in areas with interstitial fibrosis, including tubules with phenotypic change. There was a highly significant correlation between tubular alpha-SMA expression and interstitial fibrosis, interstitial alpha-SMA(+) myofibroblast accumulation, deposition of collagen types I and III, tubular TGF-beta1 expression, and renal dysfunction. In conclusion, this study provides evidence that tubular epithelial cells can undergo phenotypic change toward a myofibroblast-like phenotype on the basis of de novo alpha-SMA expression, loss of cytokeratin, and de novo collagen staining. These data, although not conclusive, provide the first support for the hypothesis that transdifferentiation of tubular epithelial cells has a role in progressive renal fibrosis in human glomerulonephritis.

Differences in the morphology of the processus vaginalis with sex and underlying disease condition

The structures of sacs from boys and girls with inguinal hernia, and from boys with undescended testis or hydrocele were evaluated and compared. Particular attention was directed to determine if a clue helpful in describing the mechanism of obliteration of processus vaginalis (PV) exists. Sacs from boys (n: 8) and girls (n: 11) with inguinal hernia, and sacs from boys with undescended testis (n: 11) and hydrocele (n: 10) were obtained and stained with hematoxylin-eosin, trichrome and elastic van Gieson. The histologic structures of each group of samples were determined and compared. Smooth muscle was presented as a layer within the sacs of girls and boys with inguinal hernia. However, smooth muscle bundles were sparsely presented in sacs associated with undescended testis and hydrocele. Myofibroblasts were commonly encountered in sacs associated with inguinal hernia. The smooth muscle was invariably presented in sacs that contained myofibroblasts. While sacs from boys only had smooth muscle, sacs from girls also had striated muscle. Since the muscle components of sacs vary, PV is sexually dimorphic. Persistence of PV seems to be associated with the presence of smooth muscle and myofibroblasts within the sac wall. Myofibroblasts may have originated from the smooth muscle, and reflect the attempts at obliteration of PV.

Phenotypic change of muscularis mucosae in early invasive colorectal adenocarcinoma

BACKGROUND

Invasive colorectal adenocarcinomas have bundles of eosinophilic spindle cells, which are regarded as myofibroblasts, in their desmoplastic stroma, some of which are continuous with the muscularis mucosa.

AIM

To investigate the relation between the eosinophilic spindle cells and the muscularis mucosa based on their cytoskeletal phenotypes in early invasive colorectal adenocarcinoma.

METHODS

Formalin fixed, paraffin wax embedded tissues of 17 early invasive colorectal adenocarcinomas were immunostained for alpha-smooth muscle actin (alpha-SMA), desmin, and vimentin.

RESULTS

The phenotype of the muscularis mucosa was alpha-SMA positive, desmin positive, and vimentin weakly positive, whereas the eosinophilic spindle cells showed a decreased degree of immunoreactivity for alpha-SMA and desmin in particular, and an increased degree of immunoreactivity for vimentin. The degree of phenotypic difference between the muscularis mucosa and the eosinophilic spindle cells was greater in the eosinophilic spindle cells in the centre of the invasive area that were not continuous with the muscularis mucosa than in the eosinophilic spindle cells continuous with the muscularis mucosa.

CONCLUSIONS

These findings suggest that the smooth muscle cells of the muscularis mucosa change their phenotype to become eosinophilic spindle cells, namely myofibroblasts, in the early invasive area of colorectal adenocarcinoma.

Repetitive acute pancreatic injury in the mouse induces procollagen alpha1(I) expression colocalized to pancreatic stellate cells

Pancreatic stellate cells may be a major source of extracellular matrix deposition during injury. This study was undertaken to establish whether pancreatic stellate cells are a source of Type I collagen in vivo and whether they continue to be a source of matrix production in the post-injury fibrotic pancreas. To induce pancreatic fibrogenesis, acute pancreatic injury was induced in mice three times weekly with supraphysiologic doses of cerulein. Animals were treated for 6 weeks and allowed to recover for an additional 6 weeks. Stellate cell activation and pancreatic collagen expression were measured by immunohistochemistry, whole tissue RNA analysis, and in situ hybridization. Histology and digital image analysis demonstrated the development of substantial pancreatic fibrosis after 6 weeks of treatment. During recovery, incomplete resolution of the fibrosis was found. Procollagen alpha1(I) mRNA increased more than 15-fold during treatment and continued to be 5-fold elevated during the post-injury phase. In situ hybridization studies demonstrated that collagen gene expression was colocalized to activated pancreatic stellate cells. Collagen expression and fibrosis persisted in focal areas during recovery. These findings show that pancreatic stellate cells are the major source of collagen during repetitive injury in vivo. Additionally, focal areas of sustained pancreatic fibrogenesis persist after cessation of cerulein treatment, and these areas may contribute to sustained total organ collagen expression in the absence of ongoing injury.

Rat liver myofibroblasts and hepatic stellate cells: different cell populations of the fibroblast lineage with fibrogenic potential

BACKGROUND & AIMS

Hepatic stellate cells (HSCs) are considered the principal matrix-producing cells of the damaged liver. However, other cell types of the fibroblast lineage that have not yet been characterized are also involved in liver tissue repair and fibrogenesis.

METHODS

We established cultures of cells of the fibroblast lineage, termed rat liver myofibroblasts, and analyzed their phenotypical and functional properties in comparison with HSCs.

RESULTS

HSCs and rat liver myofibroblasts were discernible by morphological criteria and growth behavior. Prolonged subcultivation of rat liver myofibroblasts was achieved, but HSCs were maintained in culture at maximum until second passage. HSCs were characterized by expression of glial fibrillary acidic protein, desmin, and vascular cell adhesion molecule 1, which were almost completely absent in rat liver myofibroblasts. For synthetic properties, HSCs and rat liver myofibroblasts displayed mostly overlapping properties with 4 striking differences. The complement-activating protease P100 and the protease inhibitor alpha(2)-macroglobulin were preferentially expressed by HSCs, whereas interleukin 6-coding messenger RNAs and the extracellular matrix protein fibulin 2 were almost exclusively detectable in rat liver myofibroblasts.

CONCLUSIONS

The data show that morphologically and functionally different fibroblastic populations, HSCs and rat liver myofibroblasts, can be derived from liver tissue. HSCs may not represent the single matrix-producing cell type of the fibroblast lineage in the liver.

Structural characteristics of oversulfated chondroitin/dermatan sulfates in the fibrous lesions of the liver with cirrhosis

The structural characteristics of oversulfated chondroitin/dermatan sulfates (C/DSs) in the fibrous lesions of the rat liver with cirrhosis were examined. Long-Evans Cinnamon rats were subjected to the present study as the model animals with cirrhosis. The serial polyester wax sections of liver with cirrhosis were processed into the fibrous lesions and the nonfibrous lesions. The oversulfated C/DSs in the tissue sections on a glass slide were degraded to unsaturated disaccharides by chondroitinase ABC and ACII digestion in the presence of bacterial collagenase. Subsequently, the resulting unsaturated disaccharides were determined by the reversed-phase ion-pair high-performance liquid chromatography with fluorometric postcolumn derivatization using 2-cyanoacetamide as a reagent. Through these in situ investigations, we found some facts as follows: (i) in the fibrous lesion, the remarkable increase of the oversulfated C/DSs content and the decrease of the oversulfation degree of the C/DSs were observed compared with those in the nonfibrous lesion, (ii) the proportion of the iduronic acid content in the C/DSs in the fibrous lesion was significantly low compared with that in the nonfibrous lesion, and (iii) in the nonfibrous lesion close to the fibrous lesion, both quantitative and qualitative alterations of C/DSs were not observed at all. These findings indicate that the oversulfated C/DSs with low iduronic acid content are possible marker for the fibrogenesis of liver with cirrhosis.

Myofibroblasts. I. Paracrine cells important in health and disease

Myofibroblasts are a unique group of smooth-muscle-like fibroblasts that have a similar appearance and function regardless of their tissue of residence. Through the secretion of inflammatory and anti-inflammatory cytokines, chemokines, growth factors, both lipid and gaseous inflammatory mediators, as well as extracellular matrix proteins and proteases, they play an important role in organogenesis and oncogenesis, inflammation, repair, and fibrosis in most organs and tissues. Platelet-derived growth factor (PDGF) and stem cell factor are two secreted proteins responsible for differentiating myofibroblasts from embryological stem cells. These and other growth factors cause proliferation of myofibroblasts, and myofibroblast secretion of extracellular matrix (ECM) molecules and various cytokines and growth factors causes mobility, proliferation, and differentiation of epithelial or parenchymal cells. Repeated cycles of injury and repair lead to organ or tissue fibrosis through secretion of ECM by the myofibroblasts. Transforming growth factor-beta and the PDGF family of growth factors are the key factors in the fibrotic response. Because of their ubiquitous presence in all tissues, myofibroblasts play important roles in various organ diseases and perhaps in multisystem diseases as well.

Divergence of smooth muscle target and sympathetic pathway cell phenotypes in the orbit of the developing rat

The periorbital sheath serves as a major pathway for sympathetic nerves traveling to distal orbital targets in the rat. This tissue accommodates sympathetic fiber sprouting in the neonate but becomes impassable by postnatal day 30 (PND 30). In contrast, smooth muscle target remains receptive to sympathetic ingrowth. To determine the attributes of receptive and nonreceptive tissues, we compared periorbital pathway and target tissue phenotypes prior to (PND 5 and PND 15) and after (PND 30 and PND 60) the period when pathway receptivity is lost. Both pathway cells and superior tarsal smooth muscle cells expressed alpha-smooth muscle actin and smooth muscle myosin heavy chain throughout development. At PND 5-15, both tissues also expressed vimentin, collagen IV, laminin 1 and laminin beta2, whereas fibronectin was detected only in pathway tissue. At PND 30, vimentin, collagen IV, and fibronectin were absent in tarsal muscle but were robust in pathway tissue. Laminin 1 and laminin beta2 expression was maintained in muscle; however, in pathway cells, laminin 1 declined modestly, and laminin beta2 decreased precipitously to barely detectable levels. Quantitative competitive polymerase chain reaction showed that nerve growth factor mRNA was present in the pathway throughout development at levels that were greater than both surrounding connective tissue and tarsal muscle. We conclude that the loss of pathway receptivity to sympathetic nerve ingrowth is associated with a transition from a phenotype similar to fetal smooth muscle cells to one that is more consistent with myofibroblast-like cells.

Myofibroblasts in schistosomal portal fibrosis of man

Myofibroblasts, cells with intermediate features between smooth muscle cells and fibroblasts, have been described as an important cellular component of schistosomal portal fibrosis. The origin, distribution and fate of myofibroblasts were investigated by means of light, fluorescent, immunoenzymatic and ultrastructural techniques in wedge liver biopsies from 68 patients with the hepatosplenic form of schistosomiasis. Results demonstrated that the presence of myofibroblasts varied considerably from case to case and was always related to smooth muscle cell dispersion, which occurred around medium-sized damaged portal vein branches. By sequential observation of several cases, it was evident that myofibroblasts derived by differentiation of vascular smooth muscle and gradually tended to disappear, some of them further differentiating into fibroblasts. Thus, in schistosomal pipestem fibrosis myofibroblasts appear as transient cells, focally accumulated around damaged portal vein branches, and do not seem to have by themselves any important participation in the pathogenesis of hepatosplenic schistosomiasis.

The evolving contribution of renal pathology to understanding interstitial nephritis

One hundred years of progress in the study of interstitial nephritis has expanded our diagnostic entities, resulted in identification of numerous pathogenic events, and defined the nature of the inflammatory infiltrate in ways that are useful both for general understanding and for diagnostic classification. We stand poised to enter the next hundred years with new techniques applicable to renal biopsies that detect specific biologic activities in situ in tissue sections. In the future, the information gained from these techniques is likely to result in refined and more accurate assessments of prognosis in patients with kidney disease, and to guide therapeutic interventions designed to interrupt specific sequences of active renal injury.

Low-grade myofibroblastic sarcoma: analysis of 18 cases in the spectrum of myofibroblastic tumors

The clinicopathologic, immunohistochemical, and ultrastructural features of a seemingly distinctive low-grade spindle cell sarcoma showing myofibroblastic differentiation have been analyzed in a series of 18 patients. The age range of the patients (7 women and 11 men) was 19-72 years (median: 42 years). A painless, enlarging mass was the most common clinical presentation. Five tumors arose in the oral cavity (including four lesions in the tongue), four in the lower extremities and three in the upper extremities, four cases in the abdominal/pelvic cavity, and two on the trunk. Eight soft-tissue cases involved skeletal muscle, three cases were located in perifascial tissues, and two arose in subcutaneous tissue. Tumor size ranged from 1.4 to 17 cm (median: 4 cm); in six cases (of which four were abdominal/pelvic) the lesion was larger than 5 cm. All patients were treated surgically, and four received additional adjunctive therapy. Histologically, most cases were cellular lesions showing a diffusely infiltrative pattern, and were composed of spindle-shaped tumor cells arranged mainly in fascicles. Tumor cells had poorly defined, palely eosinophilic cytoplasm and fusiform nuclei, which were either tapering and wavy or plumper and vesicular with indentations and small inconspicuous nucleoli. Tumor cells were set in a collagenous matrix often with prominent hyalinization. Mild nuclear atypia was noted in 16 cases; in the other 2 cases, and in the metastases of one other lesion, a greater degree of nuclear atypia was seen. In all but one case, the mitotic rate ranged from 1 to 6 mitoses in 10 HPFs (mean: 2/10 HPFs); in a single case, there were more than 20 mitoses in 10 HPFs. Immunohistochemically, all cases stained positively for at least one myogenic marker; 12 cases were positive for desmin, 11 for alpha-smooth muscle actin, and 6 for muscle actin (HHF35). Seven neoplasms were desmin positive/ alpha-smooth-muscle actin negative, and five cases were desmin negative/alpha-smooth-muscle actin positive emphasizing the variable immunophenotype of myofibroblastic lesions. In addition, 7 of 10 tumors stained at least focally positive for fibronectin. Ultrastructural examination in five cases showed characteristic features of myofibroblasts. Follow-up in 11 patients (median: 29 months) revealed local recurrence in 2 cases, and multiple distant soft-tissue, intraosseous, and pulmonary metastases in one other patient. Low-grade myofibroblastic sarcoma seems to represent a distinct entity in the spectrum of low-grade myofibroblastic neoplasms and is distinguishable from fibromatosis, myofibromatosis, solitary fibrous tumor, fibrosarcoma, and leiomyosarcoma.

A case of infantile digital fibromatosis with spontaneous regression

We reported a fourteen-month-old boy with infantile digital fibromatosis. At the age of seven months, a nodule appeared on the back of the left third toe, and developed into a slight red tumor divided into five hemispherical nodules. Histopathologically, spindle-shaped tumor cells with an eosinophilic inclusion body in the cytoplasm were seen in the dermis. Electron microscopy showed a dense body in the cytoplasm of the tumor cells. One year and two months after the first visit, the tumor regressed without any aggressive treatment. Japanese cases of infantile digital fibromatosis were reviewed. The literature review and our case suggest that the tumor should be observed without any aggressive treatment unless it causes mobile dysfunction of the affected finger or toe.

Role of laminin polymerization at the epithelial mesenchymal interface in bronchial myogenesis

Undifferentiated mesenchymal cells were isolated from mouse embryonic lungs and plated at subconfluent and confluent densities. During the first 5 hours in culture, all the cells were negative for smooth muscle markers. After 24 hours in culture, the mesenchymal cells that spread synthesized smooth muscle alpha-actin, muscle myosin, desmin and SM22 in levels comparable to those of mature smooth muscle. The cells that did not spread remained negative for smooth muscle markers. SM differentiation was independent of cell-cell contact or proliferation. In additional studies, undifferentiated lung mesenchymal cells were cocultured with lung embryonic epithelial cells at high density. The epithelial cells aggregated into cysts surrounded by mesenchymal cells and a basement membrane was formed between the two cell types. In these cocultures, the mesenchymal cells in contact with the basement membrane spread and differentiated into smooth muscle. The rest of the mesenchymal cells remained round and negative for smooth muscle markers. Inhibition of laminin polymerization by an antibody to the globular regions of laminin beta1/gamma1 chains blocked basement membrane assembly, mesenchymal cell spreading and smooth muscle differentiation. These studies indicated that lung embryonic mesenchymal cells have the potential to differentiate into smooth muscle and the process is triggered by their spreading along the airway basement membrane.

Transforming growth factor beta1 involvement in the conversion of fibroblasts to smooth muscle cells in the rabbit bladder serosa

In an attempt to identify the growth factors or cytokines involved in the serosal thickening that occurs in rabbit bladder subjected to partial outflow obstruction, the following growth factors--transforming growth factor beta1, platelet-derived growth factor, epidermal growth factor, granulocyte colony-stimulating factor and granulocyte-monocyte colony-stimulating factor--were delivered separately onto the serosal surface of the intact bladder via osmotic minipumps. The proliferative/differentiative cellular response of the rabbit bladder wall was evaluated by bromodeoxyuridine incorporation and immunofluorescence staining with a panel of monoclonal antibodies to cytoskeletal proteins (desmin, vimentin, keratins 8 and 18 and non-muscle myosin) and to smooth muscle (alpha-actin, myosin and SM22) proteins. Administration of the transforming growth factor, but not of the other growth factors/cytokines, was effective in inducing serosal thickening. Accumulating cells in this tissue were identified as myofibroblasts, i.e. cells showing a mixed fibroblast-smooth muscle cell differentiation profile. The phenotypic pattern of myofibroblasts changed in a time-dependent manner: 21 days after the growth factor delivery, small bundles of smooth muscle cells were found admixed with myofibroblasts, as occurs in the obstructed bladder. These 'ectopic' muscle structures displayed a variable proliferating activity and expressed an immature smooth muscle cell phenotype. The complete cellular conversion to smooth muscle cells was not achieved if transforming growth factor beta1 was delivered to fibroblasts of subcutaneous tissue. These findings suggest a tissue-specific role for this growth factor in the cellular conversion from myofibroblast to smooth muscle cells.

Multicellular spheroids: a three-dimensional in vitro culture system to study tumour biology

The growth of tumour cells as three-dimensional multicellular spheroids in vitro has led to important insights in tumour biology, since properties of the in vivo-tumour such as proliferation or nutrient gradients, can be studied under controlled conditions. While this review starts with an update of recent data on spheroid monocultures, especially concerning tumour microenvironment and therapeutic modalities, the main emphasis is put on the spectrum of heterologous cultures which have evolved in previous years. This type of culture includes tumour cell interaction with endothelial, fibroblast or immunocompetent cells. The relation of the spheroid culture model to other types of three-dimensional culture and our critical evaluation and presentation of the technical aspects of growing and analysing spheroids are included in the text. These topics are chosen to help the experimental pathologist design experiments with tumour spheroids and to stimulate discussion.