Topical tamoxifen--a potential therapeutic regime in treating excessive dermal scarring?

Abnormal dermal scarring which affects a large number of people is aesthetically disfiguring and can be functionally disabling. Existing medical and surgical strategies to prevent or to treat scars are frequently disappointing and more effective therapies are needed. Tamoxifen, which has been used extensively in the treatment of breast cancer over the last 20 years has recently been shown to inhibit the proliferation of fibroblasts cultured from keloid biopsies. Successful treatment of retroperitoneal fibrosis and desmoid tumours with tamoxifen has also been reported. We have investigated the potential of tamoxifen as an inhibitor of wound contraction, using fibroblast-populated collagen lattices as an in vitro model. From these studies we postulate that tamoxifen may have potential clinical significance in the treatment of abnormal scarring. Normal adult human skin fibroblasts were embedded within type I collagen, then medium either with or without addition of tamoxifen was added to the collagen lattices. Lattice diameters were measured at intervals to assess the influence of tamoxifen on the lattice contraction. The reversibility of the inhibitory effect of tamoxifen on lattice contraction was investigated by 'washing out the tamoxifen' at different time-points. To visualise changes in the morphology of fibroblasts MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide] was added to the lattices. Tamoxifen at 1 and 5 microM had no significant influence on lattice contraction but higher concentrations of 50 and 100 microM completely inhibited contraction. At intermediate concentrations from 10 to 20 microM the degree of lattice contraction was dose-dependent. The reversibility of the inhibition was both dose- and time-dependent. Both the inhibition of contraction and the reversibility of inhibition appeared to correlate with changes in fibroblast morphology. The dose- and time-dependent inhibition of contraction by fibroblasts suggests that tamoxifen could be investigated as a novel potential therapeutic agent in treating abnormal dermal scarring.     

Morphometric studies of collagen and fibrin lattices contracted by human gingival fibroblasts; comparison with dermal fibroblasts

Cell shape variations and substratum re-organization during contraction of floating collagen and fibrin lattices seeded with human gingival fibroblasts were determined by computerized image analysis of light and scanning electron microscopic images. Data were compared with those obtained with lattices populated with human dermal fibroblasts. The extent of collagen lattice contraction was similar with both cell types, resulting in a two-fold decrease in the area fractions occupied by collagen fibers. Fibroblasts exhibited a rounded shape (form factors equal to 0.8 and 0.7 for gingival and dermal cells, respectively) at day 1 of culture; they possessed a more elongated appearance (with form factors equal to 0.3 and 0.15 for gingival and dermal cells, respectively) at day 7. Continuous (gingival) and discontinuous (dermal) layers of cells were evidenced at the cortex of lattices. Contractions were associated with a significant reduction of the diameters of collagen fibers. Re-organization of substratum, as analyzed by the "Rose of Directions" technique, was evidenced only at the vicinity of filopodia where fibers ran parallel to these protrusions. Several lysed matrix cavities were observed when fibrin lattices were populated with gingival but not dermal fibroblasts at day 5 of culture. Although cells in fibrin lattices exhibited morphometric parameters comparable with those in collagen lattices, no fibroblast layers could be demonstrated at gel peripheries. Fibrin matrices consisted of an isotropic network of entangled fibrin filaments from the start of culture, and only a slight reduction of the diameters of fibrin fibers could be evidenced in dermal fibroblast-populated lattices. Fibrinolysis at the vicinity of gingival fibroblasts led to an entire re-organization of substratum toward the formation of larger fibers. The differential behavior of gingival vs. dermal fibroblasts inside fibrin but not collagen matrices could therefore partly explain the increased rate of remodeling of gingiva as compared with dermis.     

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.     

Decreased number of nucleolar organizing regions in collagen lattice cultured fibroblasts

Dermal fibroblasts cultivated in tridimensional matrices (lattices) of collagen exhibit a very low metabolic activity, and a low protein synthesis in particular. We have previously shown that ribosomal RNA content and half-life were decreased in collagen lattice cultured fibroblasts when compared to monolayer cultured fibroblasts. In this study, we seeded fibroblasts in collagen lattices and investigated the influence of matrix on the number of nucleolar organizing regions. We found that fibroblasts in fully retracted lattices exhibited a significant decrease of 45% (P < 0.001) in the number of nucleolar organizing regions when compared to monolayer cultured fibroblasts. This decrease was correlated to the decrease in ribosomal RNA content. These data suggest that extracellular matrix induces early alterations of synthesis and/or processing of ribosomal RNAs, explaining, at least partly, the resulting low metabolic activity.     

Targeted antimicrobial photochemotherapy

This study explores a new approach for antimicrobial therapy with light activation of targeted poly-L-lysine (pL)-chlorin e6 (ce6) conjugates. The goal was to test the hypothesis that these conjugates between pL and ce6 would efficiently target photodestruction towards gram-positive (Actinomyces viscosus) and gram-negative (Porphyromonas gingivalis) oral species while sparing an oral epithelial cell line (HCPC-1). Conjugates of ce6 with pL (average molecular weight, 2,000) having a positive, neutral, or negative charge were prepared. Illumination with red light (lambdamax = 671 nm) from a diode array produced a dose-dependent loss of CFU from the bacteria, under conditions that did not affect the viability of the epithelial cells. For P. gingivalis, the cationic conjugate produced 99% killing, while the neutral conjugate killed 91% and the anionic conjugate killed 76% after 1 min of incubation and exposure to red light for 10 min. For A. viscosus, the cationic conjugate produced >99.99% killing while HCPC-1 cells remained intact. The importance of the positive charge was shown by the effectiveness of ce6-monoethylenediamine monoamide (a monocationic derivative of ce6) in killing both bacteria. The clinically employed benzoporphyrin derivative under the same conditions killed epithelial cells while leaving P. gingivalis relatively unharmed. A mixture of ce6 with pL did not show phototoxicity comparable with that of the cationic conjugate. These results were explained by the selective uptake of the conjugates by bacteria (20- to 100-fold) compared to that by mammalian cells, while free ce6 showed much less selectivity for bacteria (5- to 20-fold). The data suggest that the cationic pL-ce6 conjugate may have an application for the photodynamic therapy of periodontal disease.     

L-2-Hydroxyglutaric aciduria: neuropathological correlations and first report of severe neurodegenerative disease and neonatal death

Chromolaena odorata (formerly Eupatorium odoratum) is used as a traditional medicine in Vietnam (Nghiem, 1992), where its Vietnamese common name is "co hoi." While it has been widely considered a weed by agriculturalists (Holm et al., 1991), the aqueous extract and the decoction from the leaves of this plant have been used throughout Vietnam for the treatment of soft tissue wounds, burn wounds, and skin infections. A number of clinical studies done by Vietnamese as well as foreign medical workers has demonstrated the efficacy of this extract on the wound-healing process. In this article, the effect of the Eupolin extract on hydrated collagen lattice contraction by human dermal fibroblasts, an in vitro model of wound contraction, is described. The significant inhibition of collagen gel contraction by Eupolin extract at 50 to 200 micrograms/ml is demonstrated in various concentrations of collagen. When the extract at 50 to 150 micrograms/ml was washed out of the lattices and replaced by fresh medium without Eupolin, the contraction of collagen by cells was resumed. The visualization of cells in the lattices by incubation in a tetrazolium salt for 2 h showed live cells at 50 to 150 micrograms/ml of extract. In contrast, all cells were killed in the higher extract doses of 300 or 400 micrograms/ml. These preliminary results showing the inhibitory effect of Eupolin extract on collagen contraction suggest that a clinical evaluation of its effect on wound contraction and scar quality should be made. This work illustrates that traditional remedies that are used by folk practitioners to improve healing can be examined in a scientific manner using in vitro wound-healing models. It could be that the synergistic properties of components of the natural extract contribute to the positive effects demonstrated on various wound-healing mechanisms.     

Effect of histamine on human fibroblast in vitro

The effects of histamine (CAS 51-45-6) on cell growth, collagen synthesis of fibroblasts derived from human foreskin, and on fibroblast-mediated collagen remodelling were studied. The cellmat DNA content was measured 2 days after human fibroblasts were plated at a split ratio of 1:10. Effect of histamine (10(-9)-10(-4) mol/l) on the increase of DNA content was not observed. Fibroblasts at confluence were cultured with histamine only, and with pyrilamine or cimetidine in addition to histamine for 2 h. Type I procollagen C-peptide in the medium was measured by enzyme immunoassay and was corrected by DNA content. Type I collagen synthesis was stimulated by histamine (10(-6)-10(-4) mol/l) and its stimulation was inhibited by cimetidine, but not by pyrilamine. Collagen solution containing fibroblast was incubated until gelation. It was incubated with histamine only, and with pyrilamine or cimetidine in addition to histamine. The gel contraction was stimulated by histamine (10(-4) mol/l) and its stimulation was inhibited by pyrilamine, but not by cimetidine. These facts suggests that histamine stimulates type I collagen synthesis of fibroblast and collagen remodeling via H2 and H1 receptors, respectively.     

Clotrimazole, an imidazole antimycotic, is a potent inhibitor of angiogenesis

PURPOSE: To evaluate the roles of fibroblast proteins in the remodeling of the subconjunctival connective tissue, we immunohistochemically assessed the expression of matrix metalloproteinases (MMP)-1 and -2, and the tissue inhibitors of matrix metalloproteinases (TIMP)-1 and -2 in cultured human subconjunctival fibroblasts and in normal and healing human subconjunctival connective tissue. METHODS: Cultured fibroblasts derived from human subconjunctival connective tissue and surgical specimens of normal and healing conjunctiva were immunostained with monoclonal antibodies directed against human MMPs and TIMPs and examined by light and electron microscopy. RESULTS: In the cultured fibroblasts, MMP-1 and TIMP-1 antibodies stained the cytoplasm in a fine granular pattern, suggesting localization of those proteins in the endoplasmic reticulum (ER) and Golgi apparatus. Antibodies to MMP-2 and TIMP-2 reacted with fibroblast cytoplasm in a granular pattern. Electron microscopy of those fibroblasts revealed MMP-1 and TIMP-1 immunoreactivity in the ER cisternae or on the membrane of the ER. In surgical samples, MMP-1 and TIMP-1 were immunohistochemically detected in healing subconjunctival tissue, but not in conjunctival epithelium or normal subconjunctival tissue. CONCLUSIONS: MMPs and TIMPs may be involved in remodeling of subconjunctival connective tissue and in fibroblast population after surgical interventions. These proteins may play a crucial role in the post-operative fibrotic process occurring during scar formation in subconjunctival tissue.     

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.     

Human wound contraction: collagen organization, fibroblasts, and myofibroblasts

The closure of ungrafted sacrococcygeal pilonidal sinus excisional wounds was studied in 15 patients. Wound punch biopsies were taken on a regular basis, and histologic sections were made. To document changes, computer-assisted morphometric image analysis was employed. Initial average wound depth was 37.8 +/- 4.6 mm, and complete closure (0 wound depth) was reached by 68 days. Wound contraction contributed 88 percent to wound closure, whereas the deposition of scar only contributed 12 percent. Maximum cells density within granulation tissue was reached by day 18. Myofibroblasts, identified by alpha-smooth muscle actin immunostaining, first appeared on day 11. Unlike those observed in laboratory animals, myofibroblasts were a minor cell population of granulation tissue, never exceeding 10 percent of the cells. The pattern of collagen fiber organization was documented by polarized light microscopy of Sirius red-stained sections. Early granulation tissue collagen fibers demonstrated a fine greenish birefringence, whereas more mature granulation tissue collagen fibers were thicker, displaying orange-yellowish birefringence. Myofibroblasts were associated exclusively with thicker collagen fibers, whereas fibroblasts were associated with both fine and thick collagen fibers. It is proposed that human wound contraction involves a volume change whereby normal dermal and adipose tissues are pulled into the defect by forces generated within fibroblasts.     

Measurement using a non-contact 3-D measurement system and histopathologic study of surface of skin scar formation after cheiloplasty

As to postoperative scar formation of maxillofacial lesions, a number of authors have reported on the clinical classification and light or electron microscopic observations of hypertrophic scars. However, there has been no quantitative study to evaluate the surface of the postoperative scar and its relevance to changes in histopathology. The purpose of this study was to assess postoperative scar formation on patients with cleft lip quantitatively by using a non-contact 3-D measurement system and to compare the findings with the histopathologic changes. Thirty-six specimens were obtained from patients when they underwent corrective surgery of the lip. The depth of the scar was measured by using a non-contact 3-D measurement system. The results were compared with morphological findings of fibroblasts and collagen fibers of the scar tissues under a light microscope. The results were following as follows: 1. The depth of the CLP group was 181.4 +/- 78.4 microns, significantly higher than 55.7 +/- 24.8 microns of the non-cleft group (p < 0.05). 2. Histologically, the scar, which formed a diffuse mass of irregularly arranged thick collagen fibers, showed a higher value in the depth of the scar than the one which formed a regular pattern. 3. The scar with mature spindle fibroblasts showed a higher value in the depth of the scar than the one with immature round fibroblasts. In conclusion, it was suggested that a non-contact 3-D measurement system is useful for measuring the depth of the scar surface, and the histologic changes of the scar influence the depth.     

Inhibitory effects of bFGF, VEGF and minoxidil on collagen synthesis by cultured hair dermal papilla cells

Dermal papilla cells of rat vibrissa follicles cultivated in monolayers and in three-dimensional collagen gels show a different morphology in these culture systems. Dermal papilla cells cultured in lattices tend to express morphological features resembling those seen in vivo. Quantification of total collagen by incorporation of 3H-proline in monolayer cultures and in collagen lattices show that the amount of collagen found in dermal papilla cells is higher than that secreted. Moreover, collagen synthesis measured in lattices is reduced to about 50% of that found in monolayer cultures. The influence of growth factors on collagen synthesis by hair dermal papilla cells was investigated. We studied the effects of basic fibroblast growth factor (bFGF), vascular endothelial growth factor (VEGF) and minoxidil on collagen synthesis in monolayers and in lattices. VEGF, bFGF and minoxidil significantly decreased the total amount of collagen. In monolayer cultures, there was approximately a 30% inhibition of collagen production with 5 ng/ml bFGF, 0.1 ng/ml VEGF and 100 ng/ml minoxidil. However, in the lattices this inhibition was reduced to about half. These results suggest that both culture substrate and growth factors influence collagen production by rat hair dermal papilla cells.     

Polymorphism of the HLA-C promotor region

We have studied how keratinocytes cultured under hyperthermal conditions modulate skin fibroblast growth potential and their biosynthetic phenotypes in vitro. When keratinocytes were cultured at 30, 34, 37 or 39 degrees C, the conditioned medium of the keratinocytes cultured at 39 degrees C showed a greater inhibitory activity for fibroblast proliferation and greater synthetic activities of collagen and glycosaminoglycans than those incubated at 30, 34, or 37 degrees C. Transforming growth factor (TGF) beta 1 production in skin fibroblasts was also stimulated by the keratinocyte conditioned medium cultured at 39 degrees C. The stimulating activity of collagen and glycosaminoglycan syntheses of keratinocyte conditioned medium may be explained at least partly by enhanced TGF beta 1 production. The results indicate that keratinocytes cultured at a higher temperature (39 degrees C) may secrete factor(s) which modulate both fibroblast growth and matrix synthesis. This may provide evidence that under hyperthermal conditions epidermis can influence the functions of skin fibroblasts.     

Increased in vivo collagen synthesis and in vitro cell proliferative effect of glycolic acid

BACKGROUND: Glycolic acid treatment is believed to reverse the photoaging process by increasing collagen synthesis in the skin. However, this effect has not been clearly defined even though alpha hydroxy acid products are used extensively. OBJECTIVE: This study aimed to define the primary effect of glycolic acid on collagen synthesis that may be achieved by functional activation or proliferation of fibroblasts. METHODS: Glycolic acid treatment was compared in vivo with lactic acid (hairless mice) and in vitro to malic acid (normal human skin fibroblast culture) with controls. To find the functional activation of fibroblasts, Northern blot assay for type I collagen synthesis with histometric analysis (in vivo) was performed. Cell proliferation assay (MTT) with procollagen type I C-peptide (PICP) enzyme immunoassay and radioisotope ([3H]proline) incorporated collagen production from cultured fibroblasts were determined. RESULTS: The in vivo collagen mRNA expression with histometric analysis revealed greater collagen synthesis by glycolic acid compared with lactic acid and control. In vitro cell proliferative effect of glycolic and greater amount of collagen production showed a steady increase in a dose-dependent manner. CONCLUSION: Both in vivo and in vitro, glycolic acid treatment increased the production of collagen and fibroblast proliferation. These effects may be the mechanism by which glycolic acid reverses the process of photoaging.     

Synthetic integrin-binding peptides promote adhesion and proliferation of human periodontal ligament cells in vitro

Periodontal ligament (PDL) cells have been shown to express several integrins (alphav, alpha5, beta1, beta3) that use RGD (arginine-glycine-aspartic Acid)-dependent mechanisms for the recognition and binding of their ligands. The objective of this study was to evaluate the effects of certain integrin-binding cyclic and linear synthetic RGD-containing peptides on PDL cells' adhesion, proliferation, and de novo protein synthesis in vitro. Fifth passages of normal human PDL cells established from teeth extracted from patients (ages 12 to 14) for orthodontic reasons were used for all experiments. Synthetic peptides containing the EPRGDNYR sequence in two different spatial conformations (linear and cyclic) were covalently attached to bovine serum albumin (BSA). Type I collagen, EPRGDNYR-BSA conjugates, 1:1 mixtures of type I collagen and conjugates, as well as BSA (a negative control) were coated on bacteriological plastic and evaluated for their attachment-promoting activities. In addition, the effects of these substrates on cell proliferation were evaluated by [3H]thymidine incorporation by the PDL cells. For attachment and spreading, the cyclic forms of EPRGDNYR-BSA conjugate and type I collagen were most potent, followed by linear EPRGDNYR-BSA conjugate. The effects of all collagen/conjugate mixtures were equivalent to that of type I collagen except for the collagen/linear EPRGDNYR-BSA mixture, which was less potent. The cyclic EPRGDNYR-BSA conjugate was the most effective substrate to stimulate cell proliferation, and it was followed in potency by the linear peptide-BSA conjugate. Collagen alone did not stimulate [3H]thymidine incorporation above the control level. Mixtures of collagen with all of the conjugates showed stimulatory effects similar to that of the cyclic peptide-BSA conjugate. No significant differences in de novo protein synthesis were detected. These results suggest that the synthetic RGD-containing peptides attached to a carrier are potent ligands for the human PDL cells, and that they could provide a basis for the development of new strategies aimed at the regeneration of the periodontium.     

Crosslinked CNBr-activated hyaluronan-collagen matrices: effects on fibroblast contraction

Previously we demonstrated that the contraction of collagen fibrillar matrices (CFM) by fibroblasts was significantly reduced when high concentrations (> 1 mg/ml) of hyaluronan were present in the media. This highlights the prominent role of hyaluronan in preventing scar formation during fetal wound healing. In the present study, we covalently crosslinked different concentrations of CNBr-activated hyaluronan to CFM and investigated the ability of fibroblasts to contract these matrices. Matrices are not contracted when optimal concentrations of CNBr-activated hyaluronan are crosslinked to collagen. Biochemical and cytological analysis of these matrices suggests that hyaluronan strengthens the collagen fibrils and blocks direct communication between fibroblasts and the collagen fibrils. Based on current evidence we are able to propose two molecular crosslinking models, multiple point attachment and simple point attachment between CNBr-activated hyaluronan and collagen molecules, hypotheses supported by the susceptibility of these matrices to digestion by collagenase.     

Induction of collagenase-3 (MMP-13) expression in human skin fibroblasts by three-dimensional collagen is mediated by p38 mitogen-activated protein kinase

Collagenase-3 (matrix metalloproteinase-13, MMP-13) is a recently identified human MMP with an exceptionally wide substrate specificity and restricted tissue-specific expression. Here we show that MMP-13 expression is induced in normal human skin fibroblasts cultured within three-dimensional collagen gel resulting in production and proteolytic activation of MMP-13. Induction of MMP-13 mRNAs by collagen gel was potently inhibited by blocking antibodies against alpha1 and alpha2 integrin subunits and augmented by activating antibody against beta1 integrin subunit, indicating that both alpha1 beta1 and alpha2 beta1 integrins mediate the MMP-13-inducing cellular signal generated by three-dimensional collagen. Collagen-related induction of MMP-13 expression was dependent on tyrosine kinase activity, as it was abolished by treatment of fibroblasts with tyrosine kinase inhibitors genistein and herbimycin A. Contact of fibroblasts to three-dimensional collagen resulted in simultaneous activation of mitogen-activated protein kinases (MAPKs) in three distinct subgroups: extracellular signal-regulated kinase (ERK)1 and ERK2, Jun N-terminal kinase/stress-activated protein kinase, and p38. Induction of MMP-13 expression was inhibited by treatment of fibroblasts with a specific p38 inhibitor, SB 203580, whereas blocking the ERK1,2 pathway (Raf/MEK1,2/ERK1,2) by PD 98059, a selective inhibitor of MEK1,2 activation potently augmented MMP-13 expression. Furthermore, specific activation of ERK1,2 pathway by 12-O-tetradecanoylphorbol-13-acetate markedly suppressed MMP-13 expression in dermal fibroblasts in collagen gel. These results show that collagen-dependent induction of MMP-13 in dermal fibroblasts requires p38 activity, and is inhibited by activation of ERK1,2. Therefore, the balance between the activity of ERK1,2 and p38 MAPK pathways appears to be crucial in regulation of MMP-13 expression in dermal fibroblasts, suggesting that p38 MAPK may serve as a target for selective inhibition of collagen degradation, e.g. in chronic dermal ulcers.     

Induction of fibroblast apoptosis by anti-CD44 antibody: implications for the treatment of fibroproliferative lung disease

Fibroblast migration and proliferation within the alveolar wall and airspace after lung injury can lead to the development of fibrosis. Fibroblast cell surface CD44 is an adhesion receptor for provisional matrix proteins and mediates fibroblast invasion into fibrin matrices. Here we show that incubation of cultured fibroblasts with an anti-CD44 monoclonal antibody induces fibroblast detachment from the substratum and morphological changes compatible with apoptosis. In addition, we show that anti-CD44 monoclonal antibody rapidly induces fibroblast apoptosis within fibrin matrices. The effect of anti-CD44 antibody on induction of fibroblast apoptosis occurred within 8 hours and was dose dependent. Anti-CD44 antibody also induced fibroblast apoptosis in suspension. Furthermore, fibroblasts plated on anti-CD44-antibody-coated surfaces initially attached and spread on the antibody; however, after an 8-hour incubation time, many of the cells developed characteristic morphological features of apoptosis. Collectively, these data indicate that apoptosis did not result solely due to detachment from the substratum. Our results identify a new function for fibroblast cell surface CD44 related to the control of cell viability. We suggest this function may be important in fibroblast population control and could potentially be exploited in designing anti-fibrotic therapies.