Fibronectin filaments and actin microfilaments are organized into a fibronexus in Dupuytren's diseased tissue

Overcoming scarring in the urethra: Challenges for tissue engineering

Urethral stricture disease is increasingly common occurring in about 1% of males over the age of 55. The stricture tissue is rich in myofibroblasts and multi-nucleated giant cells which are thought to be related to stricture formation and collagen synthesis. An increase in collagen is associated with the loss of the normal vasculature of the normal urethra. The actual incidence differs based on worldwide populations, geography, and income. The stricture aetiology, location, length and patient's age and comorbidity are important in deciding the course of treatment. In this review we aim to summarise the existing knowledge of the aetiology of urethral strictures, review current treatment regimens, and present the challenges of using tissue-engineered buccal mucosa (TEBM) to repair scarring of the urethra. In asking this question we are also mindful that recurrent fibrosis occurs in other tissues-how can we learn from these other pathologies?

Update on the role of molecular factors and fibroblasts in the pathogenesis of Dupuytren's disease

The mechanism by which the fibroblast is able to trigger palmar fibromatosis is still not yet fully understood. It would appear certain that the "abnormal" fibroblasts continuously synthesise profibrotic cytokines which are able to determine the activation to myofibroblasts, to stimulate them to the further proliferation and synthesis of other cytokines, to modify the cells' differentiation and ultrastructural characteristics, as well as the production of matrix and other proteins. Several fibroblast growth factors have been suggested to be responsible of an abnormal cell activation with an aberrantly elevated collagen synthesis and extracellular deposition in Dupuytren's disease, as TGF-Beta, TNF-Alfa, PDGF, GM-CSF, free radicals, metalloproteinases, sex hormones, gene modified expression, mechanical stimulation. The Authors review the current state of knowledge in the field, by analyzing the role of these cytokines in the palmar fibromatosis.

Open Palm Technique in Dupuytren's Disease Treatment

Objective

To evaluate the results of the open palm technique for the treatment of Dupuytren's disease.

Method

The authors used the technique described by McCash. Twelve patients (13 hands) were surgically treated, between october 2002 and september 2011.

Results

The wounds healed in a medium of 25 days (variation of 17 to 30 days). There were no complications, such as infection, haematoma formation, skin necrosis, residual edema.

Conclusion

The open palm technique remains a safe alternative for the treatment of Dupuytren's disease, with satisfactory results and low risk of complications.

Smooth and textured silicone surfaces of modified gel mammary prostheses cause a different impact on fibroproliferative properties of dermal fibroblasts

Our study addressed the question of whether surface properties of modern standard gel prostheses may have a measurable impact on the fibrogenic properties of cultured human dermal fibroblasts. Fibroblasts were isolated from breast implants by using the explant culture technique and incubated either on smooth or on textured silicone elastomere surfaces. Fibroblast growth was observed 4 weeks following incubation. Expression of transforming growth factor (TGF)-β1 was measured after cell culture. Incubated fibroblasts on textured surfaces showed a fivefold lower growth rate during all experiments. TGF-β1 expression was lowered in smooth surface fibroblasts compared with textured surface cultures. Our results show that smooth and textured silicone surfaces of modified gel breast implants have a different impact on the fibroproliferative properties of dermal fibroblasts. These preliminary results seem promising and we aim to further perform qualitative and quantitative analyses of the inflammatory processes in the environment of the implant and their link to the TGF-β pathway.

Myofibroblast distribution in Dupuytren's cords: correlation with digital contracture

PURPOSE

Dupuytren's tissue has typically been described as being composed of myofibroblast-rich palmar nodules and relatively acellular tendon-like cords. We aimed to determine myofibroblast distribution (alpha-smooth muscle actin [alpha-SMA] positive cells) within Dupuytren's tissue and to correlate histologically defined alpha-SMA-positive nodules with digital contracture and recurrent disease.

METHODS

One hundred and three digital Dupuytren's cords (72 fasciectomy, 31 dermofasciectomy) were stained with anti-alpha-SMA antibody. The presence of alpha-SMA-positive nodules, their surface area, and alpha-SMA-positive cells were quantified throughout excised Dupuytren's tissue. Clinical data on diathesis, flexion deformity, and previous surgeries were collected.

RESULTS

Cords were nodular (66%) or non-nodular (34%). Nodular cords contained 1 (55%), 2 (33%), or 3 or more nodules (12%) composed of localized collections of cells. The mean total nodule surface area was 23 mm(2) (range, 1.3-105 mm(2)). Nodules contained the highest number of alpha-SMA-positive cells (mean 97%, 2374 cells/mm(2)) compared to peri-nodular areas (mean 32%, 763 cells/mm(2)), and more distant cord (mean 8%, 495 cells/mm(2)). Non-nodular cords contained 9% to 17% alpha-SMA-positive cells (mean 475-663 cells/mm(2)), with higher numbers distally. There was greater digital contracture in patients with non-nodular cords. Thirty-six of 38 proximal interphalangeal (PIP) joint-marked samples had a nodule that co-localized with the PIP joint. Nodule size did not correlate with flexion deformity or with primary or recurrent disease.

CONCLUSIONS

We found that two thirds of digital cords were nodular. Nodules were hypercellular, the majority being alpha-SMA-positive cells. Nodules varied in size and co-localized with the PIP joint. Cord was relatively cellular throughout; a proportion of these cells were alpha-SMA-positive and cells aligned with collagen fibers. Non-nodular cords correlated with significantly greater digital flexion contracture. We propose that cells in nodular cords contract and deposit extracellular matrix components. The matrix is then remodeled in shortened configuration, and as fixed flexion deformity develops, stress shielding eventually leads to myofibroblast apoptosis, and cord becomes less cellular.

Fibronectin modulates osteoblast behavior on Nitinol

We have previously demonstrated that primary rat osteoclasts behave differently when cultured on austenite and martensite Nitinol. In this study, we coated the two phases of Nitinol with plasma fibronectin and studied if this modifies the proliferation and cell cycle of MC3T3-E1 osteoblasts. The influence of the crystalline structure of Nitinol on the remodeling and conformation of fibronectin was also studied. The results on austenite demonstrated that fibronectin was more strongly remodeled and the cells spread better compared with the martensite phase. Interestingly, the conformation of the protein showed no differences between austenite and martensite. In addition, fibronectin improved cell proliferation in both phases, but the effect of fibronectin coating was stronger on the austenite surface. In addition, in both Nitinol phases, the proportion of cells in the G(1) phase was observed to grow in the presence of fibronectin. This could indicate cell differentiation on Nitinol.

[Role of fibroblasts in physiologic, reparative and pathologic processes]

Fibroblast is counted as one of the important cell of the connective tissue. At the present time many phenotypes are known taking part in normal, repair and pathological processes, meanwhile cellular and molecular events occur, where fibroblasts play essential role. Among molecular factors, first of all integrins, growth factors, cytokines and matrix molecules are discussed. The aim of this work is to summarize the morphological, biochemical and functional role of fibroblasts in addition to the physiological process, wound repair and in such pathological processes as Dupuytren's disease, rheumatoid arthritis, Graves' ophthalmopathy and carcinogenesis. It becomes known that fibroblasts participate in dynamic interplay with other cells and with the extracellular matrix. The results of the new investigations clarify better the physiological and pathological processes of the tissue, at the same time give potential help to the therapy of some illnesses. The authors summarise the important data of the subject on the basis of international literature and of their own investigations.

Enhanced Dupuytren's disease fibroblast populated collagen lattice contraction is independent of endogenous active TGF-beta2

Background

Dupuytren's disease (DD) is a debilitating fibro-proliferative disorder of the hand characterized by the appearance of fibrotic lesions (nodules and cords) leading to flexion contractures of the fingers and loss of hand function. Although the molecular mechanism of DD is unknown, it has been suggested that transforming growth factor-β₂ (TGF-β₂) may play an important role in the underlying patho-physiology of the disease. The purpose of this study was to further explore this hypothesis by examining the effects of TGF-β₂ on primary cell cultures derived from patient-matched disease and normal palmar fascia tissue using a three-dimensional collagen contraction assay.

Methods

Fibroblast-populated collagen lattice (FPCL) contraction assays using primary cell cultures derived from diseased and control fascia of the same DD patients were studied in response to exogenous TGF-β₂ and neutralizing anti-TGF-β₂ antibodies.

Results

Contraction of the FPCLs occurred significantly faster and to a greater extent in disease cells compared to control cells. The addition of TGF-β₂ enhanced the rate and degree of collagen contraction in a dose-dependent fashion for both control and diseased cells. Neutralizing anti-TGF-β₂ antibodies abolished exogenous TGF-β₂ stimulated collagen contraction, but did not inhibit the enhanced basal collagen contraction activity of disease FPCL cultures.

Conclusions

Although exogenous TGF-β₂ stimulated both disease and control FPCL contraction, neutralizing anti-TGF-β₂ antibodies did not affect the elevated basal collagen contraction activity of disease FPCLs, suggesting that the differences in the collagen contraction activity of control and disease FPCL cultures are not due to differences in the levels of endogenous TGF-β₂ activity.

Expression of bone morphogenetic proteins by Dupuytren's fibroblasts

PURPOSE

Dupuytren's fibroblasts, or myofibroblasts, are the primary cell type in Dupuytren's disease. Growth factors play a role in the differentiation of fibroblasts to myofibroblasts. Myofibroblasts are specialized fibroblasts that display morphologic and biochemical features similar to smooth muscle cells. Cytokines, adhesion molecules, and extracellular matrix components are all thought to play a role in myofibroblast transdifferentiation. Recent research has shown that specific cytokines, such as transforming growth factor beta1 (TGF-beta1), can modulate myofibroblast expression. We hypothesize that bone morphogenetic proteins (BMPs) play a role in the modulation of Dupuytren's fibroblasts.

METHODS

Dupuytren's fibroblasts and normal palmar fascia fibroblasts (control) were analyzed for messenger RNA expression of BMPs (BMP-1, -2, -3, -4, -5, -6, -7, -8, -9, -10 and -11), their receptors (BMPR-IA, BMPR-IB, and BMPR-II), and their antagonists (follistatin and noggin) by reverse-transcription polymerase chain reaction (PCR). Western blot analysis and immunostaining also were used to confirm the differential expression of BMP-4.

RESULTS

With reverse-transcription PCR the expression profile for normal palmar fascia fibroblasts versus Dupuytren's fibroblasts was found to show similar expression of BMP-1 and -11; qualitatively decreased expression of BMP-6, BMP-8, BMPR-IA, BMPR-IB, and BMPR-II in Dupuytren's fibroblasts; and no expression of BMP-4 in Dupuytren's fibroblasts. There was no expression of BMP-2, -3, -5, -7, -9, and -10 in both the control fibroblasts and Dupuytren's fibroblasts. In line with the messenger RNA expression pattern BMP-4 was detected in only the control fibroblasts and not in the Dupuytren's fibroblasts, whereas BMP-8 (chosen for comparison purposes) was detectable in both cell populations. Immunostaining for BMP-8 and BMP-4 confirmed our findings with reverse-transcription PCR and Western blot analysis.

CONCLUSIONS

This study reports on the expression of BMPs in Dupuytren's fibroblasts. We characterized the expression of BMPs in both normal palmar fascia fibroblasts and in Dupuytren's fibroblasts through reverse-transcription PCR, Western blot analysis, and immunostaining. The most significant difference in expression profiles was in the expression of BMP-4; that is, BMP-4 was expressed in the normal fibroblasts but not in the Dupuytren's fibroblasts. Whether BMP-4 is necessary and/or sufficient for maintaining a normal palmar fascia fibroblast phenotype is not yet known. Further studies are needed to elucidate the exact role of BMPs, and especially BMP-4, in Dupuytren's fibroblasts.

Collagen as a clinical target: nonoperative treatment of Dupuytren's disease

The cellular events leading to abnormal synthesis of collagen are important to our understanding of pathologic processes leading to impaired joint function. The contracture of Dupuytren's disease is a notable example. In a series of controlled phase-2 clinical trials, excessive collagen deposition in Dupuytren's disease has been targeted by a unique nonoperative method using enzyme (Clostridial collagenase) injection therapy to lyse and rupture finger cords causing metacarpophalangeal and/or proximal interphalangeal joint contractures. Forty-nine patients were treated in a random, placebo-controlled trial of one dose of collagenase versus placebo at one center. Subsequently 80 patients were treated in a random, placebo-controlled, dose-response study of collagenase at 2 test centers. The results of these studies indicate that nonoperative collagenase injection therapy for Dupuytren's disease is both a safe and effective method of treating this disorder in the majority of patients as an alternative to surgical fasciectomy. Phase-3 efficacy trials are now being planned to further develop and test this method under Food and Drug Administration regulatory guidelines. The findings of our study may lead to simpler and less invasive nonoperative treatments of joint limitation in which collagen plays a major pathologic role.

How do fibroblasts interact with the extracellular matrix in wound contraction?

Two strong yet contradictory theories exist on how wound contraction occurs. This article, in two parts, reviews the research on both sides and discusses the limitations of non-human experiments.

Transforming growth factor-beta1 promotes the morphological and functional differentiation of the myofibroblast

The myofibroblast is responsible for the generation of contractile force associated with wound contraction and pathological contractures and is characterized by the presence of alpha-smooth muscle (alpha-sm) actin-containing stress fibers, vinculin-containing fibronexus adhesion complexes, and fibronectin fibrils containing the ED-A splice variant. Transforming growth factor-beta1 (TGF-beta1) can promote the expression of alpha-sm actin in myofibroblasts, but the functional significance of this increased expression is unclear. In this study, we demonstrate, using the stress-relaxed collagen lattice contraction assay, that TGF-beta1 promoted a dose-dependent increase in the generation of contractile force in myofibroblasts and a concomitant increase in the expression of alpha-sm actin. We also demonstrate that TGF-beta1 enhanced the formation of the structural elements important in myofibroblast contractile force generation and transmission, including stress fibers, vinculin-containing fibronexus adhesion complexes, and fibronectin fibrils, and that this enhancement occurred prior to, and independent of, alpha-sm actin expression. This differentiated myofibroblast phenotype was not stable. Removal of TGF-beta1 resulted in reduced expression of alpha-sm actin as well as a decreased assembly of stress fibers and vinculin-containing adhesion complexes; however, there was no reduction in fibronectin fibrils. We conclude that TGF-beta1 promotes the morphological and functional differentiation of the myofibroblast by first enhancing the formation of the structural elements characteristic of the myofibroblast followed by increased expression of alpha-sm actin and contractile force generation.

Physical state of the extracellular matrix regulates the structure and molecular composition of cell-matrix adhesions

This study establishes that the physical state of the extracellular matrix can regulate integrin-mediated cytoskeletal assembly and tyrosine phosphorylation to generate two distinct types of cell-matrix adhesions. In primary fibroblasts, alpha(5)beta(1) integrin associates mainly with fibronectin fibrils and forms adhesions structurally distinct from focal contacts, independent of actomyosin-mediated cell contractility. These "fibrillar adhesions" are enriched in tensin, but contain low levels of the typical focal contact components paxillin, vinculin, and tyrosine-phosphorylated proteins. However, when the fibronectin is covalently linked to the substrate, alpha(5)beta(1) integrin forms highly tyrosine-phosphorylated, "classical" focal contacts containing high levels of paxillin and vinculin. These experiments indicate that the physical state of the matrix, not just its molecular composition, is a critical factor in defining cytoskeletal organization and phosphorylation at adhesion sites. We propose that molecular organization of adhesion sites is controlled by at least two mechanisms: 1) specific integrins associate with their ligands in transmembrane complexes with appropriate cytoplasmic anchor proteins (e.g., fibronectin-alpha(5)beta(1) integrin-tensin complexes), and 2) physical properties (e.g., rigidity) of the extracellular matrix regulate local tension at adhesion sites and activate local tyrosine phosphorylation, recruiting a variety of plaque molecules to these sites. These mechanisms generate structurally and functionally distinct types of matrix adhesions in fibroblasts.

New insights in the development of Dupuytren's contracture: a review

Recent advances in the understanding of myofibroblast histology and function, the activity of fibrogenic cytokines, the role of the extracellular matrix and of free radicals are contributing to an understanding of the aetiology of Dupuytren's disease but not yet to its treatment. Surgical excision remains the best treatment.

Myofibroblastoma of breast: evidence favoring smooth-muscle rather than myofibroblastic differentiation

A histopathological study of two cases of the tumor known in the literature as myofibroblastoma of the breast is presented. The tumors occurred in Caucasian males aged 57 and 62 years. Histologically, these were moderately cellular, lobulated spindle-cell lesions, each with a reasonably well-delineated edge with surrounding fatty connective tissue. No breast ducts or lobules were present. Tumor cell nuclei were bland, with small nucleoli and some nuclear grooving. Nuclear atypia and mitoses were absent. Immunostaining revealed positivity for a-smooth-muscle actin, desmin, and CD34. Tumor cells contained rough endoplasmic reticulum, bundles of myofilaments with focal densities, intermediate filaments, attachment plaques alternating with plasmalemmal caveolae, and focal lamina. Ultrastructural findings pointed to true smooth-muscle differentiation, and the cell-surface in particular lacked surface features of myofibroblasts (fibronectin fibrils [microtendons] and fibronexus junctions). These and published data suggest that at least some of the lesions referred to in the literature as myofibroblastoma may not be myofibroblastic and may be better designated as myogenic stromal tumors or as variants of leiomyoma.

The effect of interferon-alpha2b on an in vitro model Dupuytren's contracture

The effects of interferon-alpha2b (IFN-alpha2b) on Dupuytren's and control palmar fibroblasts were evaluated using the fibroblast-populated collagen lattice model. Three paired strains of Dupuytren's and control fibroblasts were exposed to IFN-alpha2b for 96 hours before incorporation into triplicate collagen lattices. Contraction of the lattices was recorded and Northern blot analysis of cytoskeletal mRNA was performed. Comparisons of Dupuytren's and control fibroblasts revealed significantly increased contractility of the Dupuytren's fibroblasts in 2 of the 3 strains. Treatment with IFN-alpha2b significantly inhibited contraction in both Dupuytren's and control fibroblasts. In Dupuytren's fibroblasts, treatment with IFN-alpha2b significantly down-regulated mRNA expression for cytoplasmic beta-actin and gamma-actin.

Cellular terrain surrounding sympathetic nerve pathways in the rat orbit: comparisons of orbital connective tissue and smooth muscle cell phenotypes

Sympathetic axons are abundant within some orbital tissues but are absent from others. This study investigated cellular phenotypes of tissues containing sympathetic nerves en passage and compared these with phenotypes in regions devoid of sympathetic nerves and with smooth muscle targets. Two primary orbital smooth muscle targets, the tarsal muscle and orbital muscle, contained many synaptophysin-immunoreactive nerves. Target cells had ultrastructural features typical of smooth muscle and were immunoreactive for alpha-smooth muscle actin, smooth muscle myosin heavy chain, desmin, vinculin, and laminin, but not non-muscle myosin, vimentin, fibronectin, or type IV collagen; nerve growth factor (NGF) mRNA was detected by reverse transcription-polymerase chain reaction. Periorbital sheath devoid of sympathetic nerves contained elongated fibroblasts that were immunoreactive for vimentin, non-muscle myosin, and fibronectin, but not for alpha-smooth muscle actin, smooth muscle myosin heavy chain, vinculin, desmin, laminin, or type IV collagen, and did not express NGF mRNA. Regions of periorbital sheath containing sympathetic nerves had few synaptophysin-immunoreactive varicosities. Cells in this region contained myofilaments, ribosomes, and rough endoplasmic reticulum and were larger than tarsal muscle cells. They expressed NGF mRNA and showed a unique immunophenotype, reacting for vimentin, alpha-smooth muscle actin and myosin heavy chain, desmin, vinculin, laminin, and type IV collagen. This phenotype reflects both fibroblast and smooth muscle features similar to myofibroblasts or transdifferentiated smooth muscle described in other tissues. The spatial association between these cells and sympathetic nerves suggests that they may be involved in axon guidance or maintenance.

Sclerosing epithelioid fibrosarcoma: a study of five cases emphasizing diagnostic criteria

AIMS

To study the clinical and histopathological features of sclerosing epithelioid fibrosarcoma, and to define diagnostic criteria for this uncommon soft-tissue tumour.

METHODS AND RESULTS

Standard histological, immunohistochemical and ultrastructural techniques were applied to five tumours from head and neck, chest wall and groin. Tumours consisted of groups of monomorphic rounded/epithelioid cells surrounded by a prominent collagenous stroma. Tumour cells showed positive vimentin staining but were negative for other markers. They contained prominent rough endoplasmic reticulum and a large Golgi apparatus which in one case was producing collagen secretion granules, an ultrastructural marker for collagen production. Three patients had medium to long-term survival (3-7 years). Of these, one was disease-free for 3 years, and two experienced multiple recurrences: one of the latter died of metastatic disease.

CONCLUSION

Criteria for diagnosing this uncommon tumour include: small to medium cell size, clear or pale cytoplasm, cellular arrangement in cords and strands, dense collagenous stroma; vimentin staining; rough endoplasmic reticulum and a Golgi apparatus producing, in well preserved examples, collagen secretion granules. The paper emphasizes the value of electron microscopy, supporting an appropriate histological picture and immunophenotype, in identifying these relatively low-grade sarcomas.

Myofibroblasts of palmar fibromatosis co-express transforming growth factor-alpha and epidermal growth factor receptor

Several studies have shown that different growth factors are involved in the pathogenesis of palmar fibromatosis. The aim of the present study was to investigate whether transforming growth factor alpha (TGF-alpha) and its cellular receptor, epidermal growth factor receptor (EGF-R), are expressed in palmar fibromatosis. Nodules from 20 patients with palmar fibromatosis and control normal palmar fascias were studied by the reverse transcription-polymerase chain reaction (RT-PCR) and immunohistochemistry. RT-PCR followed by Southern blotting demonstrated that palmar fibromatosis nodules contained high levels of TGF-alpha and EGF-R messenger RNA (mRNA) transcripts, while normal fascias showed only low levels. Depending on the degree of cellularity and fibrosis, the three following histological phases were recognized in palmar fibromatosis nodules: proliferative, involutional, and residual. Immunohistochemistry, using alpha-smooth muscle actin as a cellular marker for myofibroblasts, revealed that TGF-alpha and EGF-R are co-expressed by myofibroblasts in the highly cellular areas of both proliferative and involutional phases, while they are absent or only focally detectable in the fibroblasts of normal fascia and in hypocellular and fibrotic areas of both involutional and residual phases. The restricted co-expression of TGF-alpha and EGF-R to myofibroblasts, the proliferating cellular component of nodules, suggests that an autocrine and/or juxtacrine growth stimulation by TGF-alpha via the EGF-R may be involved in the pathogenesis of palmar fibromatosis.

Contraction of collagen lattices by cells from Dupuytren's nodules

The aim of this study was to see if nodular cells in Dupuytren's disease differed from dermal cells in their contractile capacity and motility. Ten surgical specimens from patients with Dupuytren's disease and contracture of the finger of more than 45 degrees were harvested and the nodular cells were explanted and cultured. Dermal fibroblasts from the forearm were used as control cells. Both types of cell had the same growth pattern. The morphology on confocal laser scanning microscopy was also similar in both types of cell. Dermal control cells caused significantly more contraction of collagen lattices compared with fibroblasts from nodules of Dupuytren's contracture. The F-actin content was equal in both groups. Platelet derived growth factor, PDGF-BB (but not PDGF-AA), increased the chemotactic activity of both cell types, but there were no differences between them. The results indicate that at a late state of the disease cells from Dupuytren's nodules lose their contractile capacity and regain a phenotype resembling that of dermal fibroblasts.

Pharmacologic regulation of Dupuytren's fibroblast contraction in vitro

Dupuytren's disease is associated with contraction of specialized fibroblasts present in the diseased palmar fascia. Pharmacologic agents were evaluated for their ability to promote or inhibit contraction of Dupuytren's fibroblasts in vitro using a collagen lattice contraction assay. In the first part of the study, lysophosphatidic acid (LPA), serotonin, angiotensin II, and prostaglandin F2 alpha were tested for their ability to promote Dupuytren's fibroblast contraction. Lysophosphatidic acid was found to significantly promote Dupuytren's fibroblast contraction as compared with controls. This response to LPA is dose dependent, with a half-maximal response of 0.07 microM. Angiotensin II, serotonin, and prostaglandin F2 alpha at 1 mM, induced a significant amount of contraction as compared to controls, but the amount of contraction was at least six times less than that observed for LPA. In the second part of the study, prostaglandins E1 and E2 or the calcium blockers nifedipine and verapamil were tested for their ability to inhibit LPA-promoted contraction. It was found that both types of inhibitors partially block LPA-promoted contraction of Dupuytren's fibroblasts. The effect of the various pharmacologic agents on normal palmar fibroblasts was not evaluated. The focus of this study was to examine the regulation of contraction of Dupuytren's fibroblasts. This study demonstrates that LPA is a potent agonist of Dupuytren's fibroblast contraction and that this contraction can be inhibited by specific pharmacologic agents. These findings provide a rational basis for investigating further the clinical use of the calcium channel blockers nifedipine or verapamil and prostaglandins E1 and E2 to control Dupuytren's disease and possibly other fibrotic conditions.

Focal adhesions, contractility, and signaling

Focal adhesions are sites of tight adhesion to the underlying extracellular matrix developed by cells in culture. They provided a structural link between the actin cytoskeleton and the extracellular matrix and are regions of signal transduction that relate to growth control. The assembly of focal adhesions is regulated by the GTP-binding protein Rho. Rho stimulates contractility which, in cells that are tightly adherent to the substrate, generates isometric tension. In turn, this leads to the bundling of actin filaments and the aggregation of integrins (extracellular matrix receptors) in the plane of the membrane. The aggregation of integrins activates the focal adhesion kinase and leads to the assembly of a multicomponent signaling complex.

Differential expression of fibronectin splice variants, oncofetal glycosylated fibronectin and laminin isoforms in nodular palmar fibromatosis

The tissue formation process in nodular palmar fibromatosis (Morbus Dupuytren) was investigated by the demonstration of fibronectin splice variants (ED-A and ED-B fibronectin), de novo glycosylated fibronectin and laminin isoforms (A, M, B1, B2, s chains) in association to the proliferative activity (Ki-67 antigen) and the occurrence of myofibroblast phenotype (alpha-smooth muscle actin, desmin). The proliferative noduli of the fibromatosis were characterized by a diffuse immunostaining for alpha-smooth muscle actin, and single cells positive for desmin and the Ki-67 antigen. In contrast to the surrounding aponeurosis as extracellular matrix, components of the whole proliferative noduli were defined: ED-A, ED-B and de novo glycosylated fibronectin, B1 and B2 laminin chain, tenascin and collagen type IV. The demonstration of the A and M laminin chain was restricted to a few cells of the proliferative noduli. S laminin could be visualized in the majority of palmar aponeurotic fibroblasts. As revealed by mRNA, in situ hybridization a de novo synthesis of fibronectin could only be detected within proliferative noduli. There is a positive correlation between the myofibroblast phenotype formation, cellular proliferation and the occurrence of ED-A and ED-B containing fibronectin, as well as de novo glycosylated fibronectin in Dupuytren's disease. The ultrastructural irregularities of myofibroblastic basal lamina and the heterogeneity of the myofibroblast phenotype are equivalent to the variability of laminin isoform immunostaining.

Immunohistochemical expression of type VI collagen in superficial fibromatoses

The expression of type VI collagen was studied immunohistochemically in 26 cases of superficial fibromatoses (palmar, plantar and penile) using an immunoperoxidase method for light microscopic visualization. The polyclonal antibody against type VI collagen used in this study was isolated from human placenta and its specifity was tested by immunoblotting assay. All cases consisted of multiple nodules showing a variable degree of cellularity and fibrosis. Depending on the predominant histological appearance of these nodules, each case was assigned to the three following phases: proliferative, involutional and residual. Morphologically normal palmar and plantar aponeuroses were included as controls. Immunohistochemical findings showed that type VI collagen was present as longitudinal thin fibers in normal palmar and plantar aponeuroses. A differential expression of this collagen was found in the different stages of superficial fibromatoses. Type VI collagen was markedly expressed as a distinct fibrillar network in the extracellular matrix (ECM) surrounding proliferating stromal cells in proliferative and involutional phases. Its expression completely disappeared from the connective tissue undergoing fibrotic transformation during involutional and residual phases. The results of the present study suggest that type VI collagen is an extracellular marker of stromal tissue proliferation and is involved in the early phases of tissue remodelling occurring in the superficial fibromatoses.

Co-ordinate expression of alpha 5 beta 1 integrin and fibronectin in Dupuytren's disease

The expression of alpha 5 beta 1 (alpha 5 beta 1) integrin and its extracellular ligand fibronectin was studied immunohistochemically in 23 cases of Dupuytren's disease using an immunoperoxidase method for light microscopic visualization. All cases consisted of multiple nodules showing a variable degree of cellularity and fibrosis. Depending on the histological appearance of these nodules, each case was assigned to the three following phases: proliferative, involutional and residual. Alpha 5 beta 1 integrin was detected in the highly cellular areas of both proliferative and involutional phases where fibronectin was simultaneously expressed in the extracellular matrix (ECM). Diversely alpha 5 beta 1 and fibronectin disappeared from the hypocellular areas of involutional phase, undergoing fibrotic transformation, and from the fibrotic connective tissue of residual phases. These findings indicate that the expression pattern of alpha 5 beta 1 integrin correlates with the presence in the ECM of the corresponding ligand fibronectin during the different phases of Dupuytren's disease. We suggest that alpha 5 beta 1 integrin, linking fibronectin to stromal cells of both proliferative and involutional phases, may be involved in the contractile processes occurring in Dupuytren's disease.

Correlation of alpha-smooth muscle actin expression and contraction in Dupuytren's disease fibroblasts

We studied 11 nodules from patients with Dupuytren's contracture to determine whether alpha-smooth muscle actin expression in Dupuytren's fibroblasts is related to the generation of contractile force. Tissue was placed into explant culture and fibroblast strains were obtained. The mean percent of cultured Dupuytren's fibroblasts expressing alpha-smooth muscle actin, as determined by immunofluorescence, was 14 +/- 8 and ranged from 1% to 26%. The ability of Dupuytren's fibroblasts to generate contractile force was determined by using a previously described collagen lattice contraction assay. We observed a significant positive correlation between the expression of alpha-smooth muscle actin and the generation of contractile force in cell strains of Dupuytren's fibroblasts. In addition, six fibroblast strains from palmar fascia of individuals undergoing carpal tunnel release were examined. In six strains of palmar fibroblasts the mean percent of cells expressing alpha-smooth muscle actin was 5 +/- 3 and ranged from 1% to 9%. Six Dupuytren's fibroblast strains, in which more than 15% of the cells expressed alpha-smooth muscle actin, were significantly more contractile than the palmar fibroblasts. These results suggest that Dupuytren's fibroblasts can acquire smooth muscle characteristics and that the acquisition of a smooth muscle-like phenotype correlates with increased contractility.

Generation of contractile force by cultured Dupuytren's disease and normal palmar fibroblasts

Contractile fibroblasts are believed to be responsible for palmar fascia contracture in Dupuytren's Disease. An in vitro collagen lattice model was used to examine the contractile properties of Dupuytren's fibroblasts from 10 patients undergoing partial fasciectomy, and palmar fascia fibroblasts from 6 patients undergoing carpel tunnel release. Dupuytren's and palmar fascia fibroblasts cultured within a stabilized collagen lattice acquired morphological characteristics similar to those of 'myofibroblasts' in Dupuytren's diseased fascia. Both types of fibroblasts generated contractile forces that resulted in rapid collagen lattice contraction after release of the lattice from points of stabilization. Generation of contractile force by the fibroblasts was inhibited by disruption of the actin cytoskeleton, lack of cells, or serum removal. Afferent neuropeptides (substance P, galanin and neurokinin A) did not promote lattice contraction. These results demonstrate that normal palmar fascia fibroblasts can modulate into Dupuytren's-like fibroblasts and that cultured fibroblasts, from either Dupuytren's diseased or normal palmar fascia, can generate contractile forces that are transmitted to extracellular matrix. In addition, fibroblast contraction is an actin based process which requires specific factor(s) present in serum. It is suggested that in Dupuytren's disease extracellular cues trigger the modulation of fibroblasts to Dupuytren's fibroblasts and the promotion of contractile forces responsible for palmar fascia contrature.

Fibronexus in a case of malignant fibrous histiocytoma

A 78-year-old man presented with a subcutaneous supraorbital tumor measuring approximately 4.0 x 3.0 x 1.8 cm. It was removed in several irregular portions, and histologic sections were taken from each portion. The lesion was diagnosed as a grade 3 malignant fibrous histiocytoma. Further characterization of the tumor necessitated the use of transmission electron microscopy. This appears to be the first report of fibronexus in malignant fibrous histiocytoma. This structure linked the myofibroblast with the extracellular matrix; specifically, microfilaments were linked to fibronectin fibrils. Interaction between collagen and fibronectin was noted within the extracellular matrix.

Distribution of ED-A and ED-B containing fibronectin isoforms in Dupuytren's disease

Different fibronectin (FN) isoforms arise via alternate splicing of a single gene transcript in a cell- and tissue-specific manner. Antibodies were used to evaluate the presence and distribution of FN and its isoforms in Dupuytren's diseased and normal palmar fascia. Immunolocalization studies show extracellular FN fibrils, including FN isoforms containing extra domains A (A-FN) and B (B-FN), in proliferative and involutional stage Dupuytren's diseased tissue. However, B-FN appears less abundant and more restricted in its distribution as compared to A-FN or total FN. Total FN and A-FN are significantly reduced in residual tissue, while B-FN is not present. A-FN and B-FN are not present in normal palmar fascia, while total FN staining is slight and restricted to the loose connective tissue surrounding the large, parallel bundles of collagen fibers. The presence of A-FN and B-FN in Dupuytren's diseased palmar fascia represents a disease-induced appearance of these FN isoforms and further evidence of an association between Dupuytren's disease and wound healing.

Brief review of the fibronexus and its significance for myofibroblastic differentiation and tumor diagnosis

This brief review details the structure, nature, and distribution of the fibronexus, and discusses its significance for myofibroblastic differentiation and tumor diagnosis. The fibronexus is a cell surface specialization consisting of intracellular actin filaments and extracellular fibronectin filaments associated with subplasmalemmal plaque material. The fibronexus represents an intercellular junction between myofibroblasts, but in particular is a device for providing contact between myofibroblasts and matrix that mediates continuity between intracellular contractile filaments and extracellular matrix proteins. Immunoelectron microscopy in particular has shown that the intracellular filaments contain actin. The extracellular filaments contain fibronectin and collectively form the fibronectin fibril. The plaque probably contains such proteins as vinculin, talin, alpha-actinin, and integrin. Under appropriate biologic development and fixation conditions, the fibronectin fibril of the fibronexus is characterized by and distinguished from lamina by enhanced density, a rigid appearance, failure to adhere closely to the contours of the cell surface (except focally near the plaque material), and a longitudinally filamentous substructure. Confirmation of the presence of a fibronectin fibril may be obtained by the finding of intense cell surface staining with an antifibronectin antibody. Problems in identifying the fibronexus may be encountered, however, due to poor development and fixation, in which case the filamentous substructure may be inapparent. The fibronexus is such a typical feature of and is often so conspicuous in myofibroblasts that it can be regarded as perhaps essential for the interpretation of myofibroblastic differentiation. Structures with a similar appearance have been documented in fundamentally nonmyofibroblastic cells; these include aortic and scleral spur smooth muscle cells and endothelium. Uncertainties remain in the protein composition of the fibronexus, the nature of its contact with the matrix, and its relationship to similar structures seen in nonmyofibroblastic cells. Immunoelectron microscopy provides a potential means of clarifying some of these questions.

Fibroblast contraction occurs on release of tension in attached collagen lattices: dependency on an organized actin cytoskeleton and serum

The generation of tension in granulation tissue undergoing contraction is believed to be a cell-mediated event. In this study we used attached collagen lattices as a model system for studying the cellular mechanisms of tension generation by fibroblasts in an extracellular matrix. Fibroblasts in attached collagen lattices developed stress fibers, surface associated fibronectin fibrils, and a fibronexus-like transmembrane association interconnecting the two structural components. Release of the attached collagen lattice from its points of attachment resulted in a rapid, symmetrical contraction of the collagen lattice. Rapid contraction occurred within the first 10 minutes after release of the lattice from the substratum, with greater than 70% of the contraction occurring within the first 2 minutes. Rapid contraction resulted in a shortening of the elongate fibroblasts and compaction of the stress fibers with their subsequent disappearance from the cell. Cytochalasin D treatment prior to release disrupted the actin cytoskeleton and completely inhibited rapid contraction. The removal of serum prior to release inhibited rapid contraction, while the re-addition of serum restored rapid contraction. These results demonstrate that fibroblasts can develop tension in an attached collagen lattice and that upon release of tension the fibroblasts undergo contraction resulting in a rapid contraction of the collagen lattice. Fibroblast contraction is dependent upon an organized actin cytoskeleton and is promoted by the presence of serum.