Mast cells enhance migration and proliferation of fibroblasts into an in vitro wound

Mast cells are at the interface between the external environment and the inner organism

Mast cells localized at the level of the mucosal barrier in the skin, lung, and gastrointestinal tract, intervene in the modulation of the function of the epithelial cells and are involved in innate and adaptive defensive responses. In this context, mast cells intervene in the recognition and clearance of microbial pathogens. This mini-review article discusses the role of mast cells in these barrier systems.

Mast cells in type 2 skin inflammation: Maintenance and function

Mast cells (MCs) are immune cells residing in tissues and playing indispensable roles in maintaining homeostasis and inflammatory states. Skin lesions associated with atopic dermatitis (AD) and type 2 skin inflammation display an increment in MCs, which have both pro- and anti-inflammatory effects. The direct and indirect activations of skin MCs by environmental factors such as Staphylococcus aureus can instigate type 2 skin inflammation in AD with poorly understood mechanisms. Furthermore, both IgE-dependent and -independent degranulation of MCs contribute to pruritus in AD. Conversely, MCs suppress type 2 skin inflammation by promoting Treg expansion through IL-2 secretion in the spleen. Moreover, skin MCs can upregulate gene expression involved in skin barrier function, thus mitigating AD-like inflammation. These functional variances of MCs in AD could stem from differences in experimental systems, their localization, and origins. In this review, we will focus on how MCs are maintained in the skin under homeostatic and inflammatory conditions, and how they are involved in the pathogenesis of type 2 skin inflammation.

Roles of Mast Cells in Cutaneous Diseases

Mast cells are present in all vascularized tissues of the body. They are especially abundant in tissues that are in frequent contact with the surrounding environment and act as potential sources of inflammatory and/or regulatory mediators during development of various infections and diseases. Mature mast cells’ cytoplasm contains numerous granules that store a variety of chemical mediators, cytokines, proteoglycans, and proteases. Mast cells are activated via various cell surface receptors, including FcϵRI, toll-like receptors (TLR), Mas-related G-protein-coupled receptor X2 (MRGPRX2), and cytokine receptors. IgE-mediated mast cell activation results in release of histamine and other contents of their granules into the extracellular environment, contributing to host defense against pathogens. TLRs, play a crucial role in host defense against various types of pathogens by recognizing pathogen-associated molecular patterns. On the other hand, excessive/inappropriate mast cell activation can cause various disorders. Here, we review the published literature regarding the known and potential inflammatory and regulatory roles of mast cells in cutaneous inflammation, including atopic dermatitis, psoriasis, and contact dermatitis GVHD, as well as in host defense against pathogens.

Coactivity of Mast Cells and Stem Cells on Angiogenesis and Antioxidants' Potentials at Inflammation, Proliferation, and Tissue Remodeling Phases of Wound

Background  Reactive oxygen species cause serious damage to the physiological function of tissues. Determination of total antioxidant capacity of skin tissue is one of the determinants of damaged tissue function. Mast cells (MCs) are one of the groups of cells that are invited to the site of injury. The healing process begins with the rapid release of various types of MCs' intermediate factors at the site of injury. Bone marrow mesenchymal stem cell (BMMSC) production and secretion have been shown to regenerate the skin. The aim of this research was to evaluate the wound-healing and antioxidant effects of BMMSCs per MCs.

Methods  Fifty-four albino Wistar male rats were divided into three groups: (1) nonsurgery, (2) surgery, and (3) surgery + BMMSCs. Groups 2 and 3 were operated with a 3 × 8 cm flap and in group 3, cell injections (7 × 10 ⁹ cell injection at the time of surgery) were performed. After days 4, 7, and 15, percentage of the surviving tissue, histological characteristics, superoxide dismutase (SOD) activity, and amount of malondialdehyde (MDA) were measured in the groups. For results, Graph Pad Prism 8 software was used, and data were analyzed and compared by analysis of variance and Tukey test.

Results  BMMSCs' application decreased the amount of MDA, increased SOD activity and survival rate of the flaps, and improved the histological characteristics.

Conclusion  This study revealed the protective effects BMMSCs alongside MCs against oxidative stress on the survival of the flaps. However, for clinical use, more research is needed to determine its benefits.

A Review of the Evidence for and against a Role for Mast Cells in Cutaneous Scarring and Fibrosis

Scars are generated in mature skin as a result of the normal repair process, but the replacement of normal tissue with scar tissue can lead to biomechanical and functional deficiencies in the skin as well as psychological and social issues for patients that negatively affect quality of life. Abnormal scars, such as hypertrophic scars and keloids, and cutaneous fibrosis that develops in diseases such as systemic sclerosis and graft-versus-host disease can be even more challenging for patients. There is a large body of literature suggesting that inflammation promotes the deposition of scar tissue by fibroblasts. Mast cells represent one inflammatory cell type in particular that has been implicated in skin scarring and fibrosis. Most published studies in this area support a pro-fibrotic role for mast cells in the skin, as many mast cell-derived mediators stimulate fibroblast activity and studies generally indicate higher numbers of mast cells and/or mast cell activation in scars and fibrotic skin. However, some studies in mast cell-deficient mice have suggested that these cells may not play a critical role in cutaneous scarring/fibrosis. Here, we will review the data for and against mast cells as key regulators of skin fibrosis and discuss scientific gaps in the field.

Efficacy of methylprednisolone on T-2 toxin-induced cardiotoxicity in vivo: A pathohistological study

Our aim was to compare the protective efficacy of two different formulations of methylprednisolone in T-2 toxin-induced cardiomyopathy. Methylprednisolone (soluble form, Lemod-solu^® and/or depot form, Lemod-depo^®, a total single dose of 40 mg/kg im) was given immediately after T-2 toxin (1 LD₅₀ 0.23 mg/kg sc). The myocardial tissue samples were examinated by using histopathology, semiquantitative and imaging analyses on day 1, 7, 14, 21, 28 and 60 of the study. Therapeutic application of Lemod-solu^® significantly decreased the intensity of myocardial degeneration and haemorrhages, distribution of glycogen granules in the endo- and perimysium, a total number of mast cells and the degree of their degranulation was in correlation with the reversible heart structural lesions (p <  0.01 vs. T-2 toxin). These changes were completely abolished by the therapeutic use of Lemod-solu^® plus Lemod-depo^® (p <  0.001 vs. T-2 toxin). Our results show that a significant cardioprotective efficacy of methylprednisolone is mediated by its anti-inflammatory activity.

Amianthoid Myofibroblastoma of the Soft Tissues

Myofibroblastoma (MF) is an uncommon, usually benign, mesenchymal tumor infrequently described in soft tissues. We report here on the clinicopathologic findings of a soft tissue MF (STMF) presenting in the neck of a 90-year-old man as a slowly growing and non-painful nodule, 4 cm in greatest diameter. Histology revealed a circumscribed lesion constituted of monomorphous bipolar spindle cells arranged in swirling fascicles with intervening broad bands of hyalinized collagen and well formed “amianthoid” fibers. Immunohistochemistry showed the spindle cells to be immunoreactive for vimentin, smooth muscle actin and muscle specific actin and, focally, for desmin; im-munostaining for cytokeratin, epithelial membrane antigen, S-100 protein, factor VIII-related antigen, and CD34 was negative. Based on the present case and on those previously reported in the literature, STMF is characterized by: 1) exclusive incidence in the male sex; 2) variable immunoreactivity of the neoplastic cells for desmin, probably reflecting an origin from a peculiar subset of myofibroblasts, or, alternatively, a further myoid differentiation; 3) variable abundance of (hyalinized) collagen; 4) presence of amianthoid fibers. The combination of desmin immunoreactivity, frequently observed in MF of the breast, and amianthoid fibers, the main feature of MF of the lymph nodes, has never been observed in soft tissue MF. It is important to recognize STMF as a specific clinicopathologic entity to avoid confusion with other types of spindle cell proliferation and to differentiate it from other types of myofibromatosis.

The role of histamine in the regulation of the viability, proliferation and transforming growth factor β1 secretion of rat wound fibroblasts

BACKGROUND

Inflammation mediators play a regulatory role in repair processes. The study will examine the influence of histamine on wound fibroblast metabolic activity, viability, proliferation, and TGFβ1 secretion. The study also will identify the histamine receptor involved in regulation of the tested repair processes.

METHODS

Fibroblasts were obtained from the granulation tissue of wounds or intact dermis of rats. The MTT and BrdU assays were used to examine the effect of histamine (10^-8M-10^-4M) on the viability and metabolic activity of fibroblasts, and on their proliferative capacity. The influence of histamine receptor antagonists (i.e., ketotifen, ranitidine, ciproxifan and JNJ7777120) and agonists (2-pyridylethlamine dihydrochloride, amthamine dihydrobromide) was also investigated. The TGFβ1 and histamine receptors H1 were evaluated by enzyme-linked immunosorbent assay.

RESULTS

Histamine significantly increased granulation tissue fibroblast viability and metabolic activity at 10^-8 and 10^-6M but did not change their proliferative activity. Only the blockade of the H1 receptor removed this effect of histamine. H1 receptor agonist (2-pyridylethlamine dihydrochloride) increased cell viability, thereby mimicking histamine action. Both Histamine (10^-4M) and 2-pyridylethlamine dihydrochloride increased TGFβ1 concentration in cell culture medium. However, ketotifen blocked histamine-induced augmentation of TGFβ1. H1 receptor expression on wound fibroblasts was confirmed.

CONCLUSION

The regulatory influence of histamine on wound fibroblast function (viability/metabolic activity or secretion of TGFβ1) is dependent on H1 receptor stimulation. Contrary to wound fibroblasts, these cells express a very low level of H1 receptors when isolated from intact dermis and histamine is unable to modify their metabolic activity.

Dividing phase-dependent cytotoxicity profiling of human embryonic lung fibroblast identifies candidate anticancer reagents

Human Embryonic Lung fibroblasts (HEL cells) are widely used as a normal cell in studies of cell biology and can be easily maintained in the resting phase. Here we aimed to discover compounds that exhibit cytotoxicity against HEL cells in the dividing phase, but not in the resting phase. The cytotoxicity of each compound against HEL cells either in the resting phase or in the dividing phase was determined by MTT assay. Ratios of the IC50 of cells in the resting phase and that of cells in the dividing phase (RRD) for these compounds were compared. We selected 44 compounds that exhibited toxic effects on HEL cells in the dividing phase from a chemical library containing 325 anticancer drugs and enzyme inhibitors. The RRD values of those compounds were widely distributed. Paclitaxel and docetaxel, which are clinically used as anticancer drugs, had RRD values larger than 2000. On the other hand, the RRD value of dimethyl sulfoxide, an organic solvent, was 1. The cytotoxic effect of paclitaxel on HEL cells in the dividing phase was attenuated by aphidicolin, hydroxyurea, and nocodazole, confirming that the cytotoxic effects of paclitaxel are dependent on cells being in the dividing phase. Thapsigargin, whose RRD value was 800, the third highest RRD value in the library, exhibited therapeutic effects in a mouse model of FM3A ascites carcinoma. We suggest that compounds with high RRD values for HEL cells are candidate anticancer chemotherapy seeds.

Can transcutaneous electrical nerve stimulation improve achilles tendon healing in rats?

BACKGROUND:

Tendon injury is one of the most frequent injuries in sports activities. TENS is a physical agent used in the treatment of pain but its influence on the tendon's healing process is unclear.

OBJECTIVE:

To evaluate the influence of TENS on the healing of partial rupture of the Achilles tendon in rats.

METHOD:

Sixty Wistar rats were submitted to a partial rupture of the Achilles tendon by direct trauma and randomized into six groups (TENS or Sham stimulation) and the time of evaluation (7, 14, and 21 days post-injury). Burst TENS was applied for 30 minutes, 6 days, 100 Hz frequency, 2 Hz burst frequency, 200 µs pulse duration, and 300 ms pulse train duration. Microscopic analyses were performed to quantify the blood vessels and mast cells, birefringence to quantify collagen fiber alignment, and immunohistochemistry to quantify types I and III collagen fibers.

RESULTS:

A significant interaction was observed for collagen type I (p=0.020) where the TENS group presented lower percentage in 14 days after the lesion (p=0.33). The main group effect showed that the TENS group presented worse collagen fiber alignment (p=0.001) and lower percentage of collagen III (p=0.001) and the main time effect (p=0.001) showed decreased percentage of collagen III at 7 days (p=0.001) and 14 days (p=0.001) after lesion when compared to 21 days.

CONCLUSIONS:

Burst TENS inhibited collagen I and III production and impaired its alignment during healing of partial rupture of the Achilles tendon in rats.

Stimulatory effects of histamine on migration of nasal fibroblasts

BACKGROUND

Fibroblast migration is crucial for normal wound repair after sinonasal surgery. Histamine is known to be involved in wound healing by its effects on cell proliferation and migration. This study aimed to determine whether histamine affects the migration of nasal fibroblasts and to investigate the mechanism of action of histamine on nasal fibroblasts.

METHODS

Primary cultures of nasal fibroblasts were established from inferior turbinate samples. Fibroblast migration was evaluated with scratch assays. Cells were treated with histamine and/or histamine receptor-selective antagonists. U-73122 and pertussis toxin, which are selective inhibitors of the lower signaling pathway of H1R and H4R, were used to confirm the modulation of nasal fibroblast migration by histamine. Fibroblast cytoskeletal structures were visualized with immunocytochemistry.

RESULTS

Histamine significantly stimulated the migration of nasal fibroblasts. Antagonists selective for HR1 and HR4 significantly reduced nasal fibroblast migration. In immunocytochemical staining, histamine treatment increased membrane ruffling and pyrilamine, diphenhydramine, fexofenadine, and JNJ7777120 decreased histamine-induced membrane ruffling. U-73122 and pertussis toxin also decreased histamine-induced migration of fibroblasts. Histamine maintains its stimulatory effects on fibroblast migration in the presence of mitomycin C, which blocks proliferation of cells.

CONCLUSION

We showed that histamine stimulates fibroblast migration in nasal fibroblasts. This effect appeared to be mediated by HR1 and HR4. However, because fibroblast migration also can be involved in scaring and fibrosis, more research is necessary to determine the effects of antihistamine on wound healing after sinus surgery.

Mast cell function: a new vision of an old cell

Since first described by Paul Ehrlich in 1878, mast cells have been mostly viewed as effectors of allergy. It has been only in the past two decades that mast cells have gained recognition for their involvement in other physiological and pathological processes. Mast cells have a widespread distribution and are found predominantly at the interface between the host and the external environment. Mast cell maturation, phenotype and function are a direct consequence of the local microenvironment and have a marked influence on their ability to specifically recognize and respond to various stimuli through the release of an array of biologically active mediators. These features enable mast cells to act as both first responders in harmful situations as well as to respond to changes in their environment by communicating with a variety of other cells implicated in physiological and immunological responses. Therefore, the critical role of mast cells in both innate and adaptive immunity, including immune tolerance, has gained increased prominence. Conversely, mast cell dysfunction has pointed to these cells as the main offenders in several chronic allergic/inflammatory disorders, cancer and autoimmune diseases. This review summarizes the current knowledge of mast cell function in both normal and pathological conditions with regards to their regulation, phenotype and role.

Are mast cells instrumental for fibrotic diseases?

Idiopathic pulmonary fibrosis (IPF) is a fatal lung disorder of unknown etiology characterized by accumulation of lung fibroblasts and extracellular matrix deposition, ultimately leading to compromised tissue architecture and lung function capacity. IPF has a heterogeneous clinical course; however the median survival after diagnosis is only 3–5 years. The pharmaceutical and biotechnology industry has made many attempts to find effective treatments for IPF, but the disease has so far defied all attempts at therapeutic intervention. Clinical trial failures may arise for many reasons, including disease heterogeneity, lack of readily measurable clinical end points other than overall survival, and, perhaps most of all, a lack of understanding of the underlying molecular mechanisms of the progression of IPF. The precise link between inflammation and fibrosis remains unclear, but it appears that immune cells can promote fibrosis by releasing fibrogenic factors. So far, however, therapeutic approaches targeting macrophages, neutrophils, or lymphocytes have failed to alter disease pathogenesis. A new cell to garner research interest in fibrosis is the mast cell. Increased numbers of mast cells have long been known to be present in pulmonary fibrosis and clinically correlations between mast cells and fibrosis have been reported. More recent data suggests that mast cells may contribute to the fibrotic process by stimulating fibroblasts resident in the lung, thus driving the pathogenesis of the disease. In this review, we will discuss the mast cell and its physiological role in tissue repair and remodeling, as well as its pathological role in fibrotic diseases such as IPF, where the process of tissue repair and remodeling is thought to be dysregulated.

Development of mast cells and importance of their tryptase and chymase serine proteases in inflammation and wound healing

Mast cells (MCs) are active participants in blood coagulation and innate and acquired immunity. This review focuses on the development of mouse and human MCs, as well as the involvement of their granule serine proteases in inflammation and the connective tissue remodeling that occurs during the different phases of the healing process of wounded skin and other organs. The accumulated data suggest that MCs, their tryptases, and their chymases play important roles in tissue repair. While MCs initially promote healing, they can be detrimental if they are chronically stimulated or if too many MCs become activated at the same time. The possibility that MCs and their granule serine proteases contribute to the formation of keloid and hypertrophic scars makes them potential targets for therapeutic intervention in the repair of damaged skin.

The localisation of inflammatory cells and expression of associated proteoglycans in response to implanted chitosan

Implantation of a foreign material almost certainly results in the formation of a fibrous capsule around the implant however, mechanistic events leading to its formation are largely unexplored. Mast cells are an inflammatory cell type known to play a role in the response to material implants, through the release of pro-inflammatory proteases and cytokines from their α-granules following activation. This study examined the in vivo and in vitro response of mast cells to chitosan, through detection of markers known to be produced by mast cells or involved with the inflammatory response. Mast cells, identified as Leder stained positive cells, were shown to be present in response to material implants. Additionally, the mast cell receptor, c-kit, along with collagen, serglycin, perlecan and chondroitin sulphate were detected within the fibrous capsules, where distribution varied between material implants. In conjunction, rat mast cells (RBL-2H3) were shown to be activated following exposure to chitosan as indicated by the release of β-hexosaminidase. Proteoglycan and glycosaminoglycans produced by the cells showed similar expression and localisation when in contact with chitosan to when chemically activated. These data support the role that mast cells play in the inflammatory host response to chitosan implants, where mediators released from their α-granules impact on the formation of a fibrous capsule by supporting the production and organisation of collagen fibres.

CADM1 is a key receptor mediating human mast cell adhesion to human lung fibroblasts and airway smooth muscle cells

Background

Mast cells (MCs) play a central role in the development of many diseases including asthma and pulmonary fibrosis. Interactions of human lung mast cells (HLMCs) with human airway smooth muscle cells (HASMCs) are partially dependent on adhesion mediated by cell adhesion molecule-1 (CADM1), but the adhesion mechanism through which HLMCs interact with human lung fibroblasts (HLFs) is not known. CADM1 is expressed as several isoforms (SP4, SP1, SP6) in HLMCs, with SP4 dominant. These isoforms differentially regulate HLMC homotypic adhesion and survival.

Objective

In this study we have investigated the role of CADM1 isoforms in the adhesion of HLMCs and HMC-1 cells to primary HASMCs and HLFs.

Methods

CADM1 overexpression or downregulation was achieved using adenoviral delivery of CADM1 short hairpin RNAs or isoform-specific cDNAs respectively.

Results

Downregulation of CADM1 attenuated both HLMC and HMC-1 adhesion to both primary HASMCs and HLFs. Overexpression of either SP1 or SP4 isoforms did not alter MC adhesion to HASMCs, whereas overexpression of SP4, but not SP1, significantly increased both HMC-1 cell and HLMC adhesion to HLFs. The expression level of CADM1 SP4 strongly predicted the extent of MC adhesion; linear regression indicated that CADM1 accounts for up to 67% and 32% of adhesion to HLFs for HMC-1 cells and HLMCs, respectively. HLFs supported HLMC proliferation and survival through a CADM1-dependent mechanism. With respect to CADM1 counter-receptor expression, HLFs expressed both CADM1 and nectin-3, whereas HASMCs expressed only nectin-3.

Conclusion and Clinical Relevance

Collectively these data indicate that the CADM1 SP4 isoform is a key receptor mediating human MC adhesion to HASMCs and HLFs. The differential expression of CADM1 counter-receptors on HLFs compared to HASMCs may allow the specific targeting of either HLMC-HLF or HLMC-HASMC interactions in the lung parenchyma and airways.

Direct effects of conjugated linoleic acid isomers on P815 mast cells in vitro

Conjugated linoleic acid (CLA) is a dietary fatty acid which causes extensive remodeling and mast cell recruitment in the mouse mammary gland. Two CLA isomers, 9,11- and 10,12-CLA, have differing effects in vivo, with only 10,12-CLA increasing mast cell number. The purpose of this project is to test the hypothesis that CLA acts directly on the mast cell. The P815 mastocytoma cell line was assayed for the effects of CLA on mast cell number, proliferation, apoptosis, and differentiation. Both CLA isomers decreased viable mast cell number, with no effect on membrane integrity, or cell cycle distribution. 10,12-CLA induced an increase in apoptosis, assessed by Annexin-FITC binding. Both isomers increased mast cell granularity, and secretion of MMP-9. The complex effects of CLA isomers on mast cells in the mammary gland are distinct from direct effects on mast cells in vitro, and may require interactions between multiple cell types present in vivo.

Mast cells as cellular sensors in inflammation and immunity

Mast cells are localized in tissues. Intense research on these cells over the years has demonstrated their role as effector cells in the maintenance of tissue integrity following injury produced by infectious agents, toxins, metabolic states, etc. After stimulation they release a sophisticated array of inflammatory mediators, cytokines, and growth factors to orchestrate an inflammatory response. These mediators can directly initiate tissue responses on resident cells, but they have also been shown to regulate other infiltrating immune cell functions. Research in recent years has revealed that the outcome of mast cell actions is not always detrimental for the host but can also limit disease development. In addition, mast cell functions highly depend on the physiological context in the organism. Depending on the genetic background, strength of the injurious event, the particular microenvironment, mast cells direct responses ranging from pro- to anti-inflammatory. It appears that they have evolved as cellular sensors to discern their environment in order to initiate an appropriate physiological response either aimed to favor inflammation for repair or at the contrary limit the inflammatory process to prevent further damage. Like every sophisticated machinery, its dysregulation leads to pathology. Given the broad distribution of mast cells in tissues this also explains their implication in many inflammatory diseases.

MAST CELLS INDUCE ACTIVATION OF HUMAN LUNG FIBROBLASTS IN VITRO

Mast cells are able to induce proliferation of skin fibroblasts; however, their effect on lung fibroblasts has not been clearly established. Using in vitro cocultures of rat or human mast cells with lung fibroblasts, the authors determined whether mast cells alter proliferation, collagen synthesis, and metalloproteinase production from lung fibroblasts. Mast cells enhanced the proliferation of human fibroblasts (mean +/- SEM: 90% +/- 4.7% increase, P < .001) while inhibiting fibroblast collagen synthesis (48.1% +/- 4.2% decrease, P < .001). Histamine, but not tryptase, significantly enhanced fibroblast proliferation: 92% +/- 5.8% (P < .001) and 39.2% +/- 4.3% (P > 0.05), respectively. Rat mast cell sonicate added to lung fibroblasts induced the activation of metalloproteinase-9 while inhibiting that of metaloproteinase-2. The addition of lipopolysaccharide (LPS)-stimulated lung macrophage supernatant further enhanced the poliferative effect of mast cells on fibroblasts (by 60% +/- 7.8%, P < .001) and induced synthesis of collagen from these cells (190% +/- 28% increase versus control, P < .05). This study demonstrates that mast cells influence several aspects of lung fibroblast function in vitro.

Generation of anaphylatoxins by human beta-tryptase from C3, C4, and C5

Both mast cells and complement participate in innate and acquired immunity. The current study examines whether beta-tryptase, the major protease of human mast cells, can directly generate bioactive complement anaphylatoxins. Important variables included pH, monomeric vs tetrameric forms of beta-tryptase, and the beta-tryptase-activating polyanion. The B12 mAb was used to stabilize beta-tryptase in its monomeric form. C3a and C4a were best generated from C3 and C4, respectively, by monomeric beta-tryptase in the presence of low molecular weight dextran sulfate or heparin at acidic pH. High molecular weight polyanions increased degradation of these anaphylatoxins. C5a was optimally generated from C5 at acidic pH by beta-tryptase monomers in the presence of high molecular weight dextran sulfate and heparin polyanions, but also was produced by beta-tryptase tetramers under these conditions. Mass spectrometry verified that the molecular mass of each anaphylatoxin was correct. Both beta-tryptase-generated C5a and C3a (but not C4a) were potent activators of human skin mast cells. These complement anaphylatoxins also could be generated by beta-tryptase in releasates of activated skin mast cells. Of further biologic interest, beta-tryptase also generated C3a from C3 in human plasma at acidic pH. These results suggest beta-tryptase might generate complement anaphylatoxins in vivo at sites of inflammation, such as the airway of active asthma patients where the pH is acidic and where elevated levels of beta-tryptase and complement anaphylatoxins are detected.

Immunohistochemical study of the presence of mast cells in idiopathic orbital inflammatory pseudotumor: possible role of mast cells in the course of its pathogenesis

BACKGROUND

It is well known that mast cells (MC) are involved in fibrosis and many forms of chronic inflammation. Chronic inflammatory cells infiltration and fibrosis in various orbital tissues are the main histopathologic features in patients with idiopathic orbital inflammatory pseudotumor (IOIP). Whether MC is involved in the course of chronic inflammatory conditions of IOIP is not yet clear. We sought to investigate the distribution of MCs in samples of IOIP and to explore the possible role of MC in the course of its pathegenesis.

METHODS

Immunohistochemistry with tryptase monoclonal antibody (a specific mast-cell surface marker) was used in 53 different subtypes of IOIP specimens including 19 of the lymphocyte infiltrative type, 22 of the fibrotic type, 12 of the mixed type and 4 specimens of normal orbital tissue. The number of positive stained MC was counted by light microscopy. The differences of the number of MC between various subtypes of IOIP were analyzed.

RESULTS

The average number of positive stained MC in the normal control group was 33.33 +/- 4.72 /mm(3), whereas the average numbers of positive stained MC in the lymphocyte infiltrative subtype group, the mixed subtype group and the fibrotic subtype group were 306.35 +/- 55.81 /mm(3), 662.93 +/- 115.28 /mm(3) and 813.44 +/- 146.56 /mm(3), respectively. Compared with the normal control, the number of MC increased significantly in all three subtypes of IOIP samples (P < 0.01). The number of MC in fibrotic subtype IOIP was the largest, followed by mixed subtype IOIP, and the lymphocyte infiltrative subtype IOIP (P < 0.05). The MC were distributed mainly around small vessels and in collagen fibers.

CONCLUSION

Mast cells may play an underappreciated role in the fibrosis of IOIP.

Nerve growth factor effect on human primary fibroblastic-keratocytes: Possible mechanism during corneal healing

In response to corneal injury, cytokines and growth factors play a crucial role by influencing epithelial-stromal interaction during the healing and reparative processes which may resolve in tissue remodeling and fibrosis. While transforming growth factor-beta1 (TGF-beta1) is considered the main profibrogenic modulator of these process, recently the nerve growth factor (NGF) appears as a pleiotropic modulator of wound-healing and inflammatory responses. Interestingly in the cornea, where NGF, trkA(NGFR) and p75(NTR) are expressed by epithelial cells and keratocytes, the NGF eye-drop induces the healing of neurotrophic or autoimmune corneal ulcers. During corneal healing, quiescent keratocytes are replaced by active fibroblast-like keratocytes/myofibroblasts. While the NGF effect on epithelial cells has been investigated, no data are reported for NGF effects on fibroblastic-keratocytes, during corneal healing. NGF, trkA(NGFR) and p75(NTR) were found expressed by fibroblastic-keratocytes. NGF was able to induce fibroblastic-keratocyte differentiation into myofibroblasts, migration, Metalloproteinase-9 expression/activity and contraction of a 3D collagen gel, without affecting their proliferation and collagen production. These data also show a two-directional control of fibroblastic-keratocytes by NGF and TGF-beta1. To sum up, the findings of this study indicate that NGF can modulate some functional activities of fibroblastic-keratocytes, thus substantiating the healing effects of NGF on corneal wound-healing.

Mast cells are required for normal healing of skin wounds in mice

Mast cells (MCs) have recently been reported to play a pivotal role in the elicitation of inflammatory reactions that are beneficial to the host, e.g., during innate immune responses to bacteria. To explore whether MCs also contribute to wound repair, we studied experimentally induced skin wounds in MC-deficient Kit(W)/Kit(W-v) mice, normal Kit+/+ mice, and MC-reconstituted Kit(W)/Kit(W-v) mice. Wound closure was significantly impaired in the absence of MCs during the first 6 days of wound healing and histomorphometric analyses of MC degranulation at the wound edges revealed distance-dependent MC activation, i.e., MC degranulation was most prominent directly adjacent to the wound. In addition, Kit(W)/Kit(W-v) mice showed impaired extravasation and recruitment of neutrophils to the wounded areas. Notably, wound closure, extravasation, and neutrophil recruitment were found to be normal in MC-reconstituted Kit(W)/Kit(W-v) mice. Therefore, we examined whether MCs promote wound healing by releasing histamine or TNF-alpha. Interestingly, wound closure was reduced in mice treated with an H1-receptor antagonist but not after treatment with an H2-receptor antagonist or in the absence of TNF-alpha. Taken together, our findings indicate that MC activation and histamine release are required for normal cutaneous wound healing.

The pro-fibrogenic effect of nerve growth factor on conjunctival fibroblasts is mediated by transforming growth factor-beta

BACKGROUND

Nerve growth factor (NGF) and nerve growth factor receptor (NGFR) expressions have been found to be increased in sub-conjunctival scarring.

OBJECTIVE

The aim of this study was to investigate the in vitro effects of NGF on some pro-fibrogenic properties of human conjunctival fibroblasts.

METHODS

Expression of NGF, trkA(NGFR) and p75NTR on human fibroblasts grown from conjunctival biopsies and incubated for 2 or 6 days with NGF were evaluated by immunofluorescence, RT-PCR, flow cytometry and ELISA. The fibrogenic effect of NGF on conjunctival fibroblasts was investigated by evaluating their migration (wound model), proliferation ([3H]-thymidine incorporation), collagen production (3H]-proline incorporation), expression of alpha-smooth muscle actin (alpha-SMA) (cell surface ELISA) and contraction of 3D collagen gels.

RESULTS

NGF induced the expression of p75NTR in the fibroblasts that constitutively expressed only trkA(NGF) and increased the migration of wounded fibroblasts, but not their proliferation and collagen production. NGF induced the conversion of fibroblasts into myofibroblasts expressing alpha-SMA, and enhanced their contraction of a collagen matrix. Interestingly, chronic NGF treatment induced transforming growth factor-beta1 (TGF-beta1) production by fibroblasts, and following specific TGF-beta neutralization, all the NGF-induced effects were completely abrogated.

CONCLUSION

Our findings indicate that NGF, via TGF-beta induction, is likely to be involved in the healing or fibrotic processes occurring in conjunctiva during some pathological conditions.

Anti-allergic activity of a Kampo (Japanese herbal) medicine "Sho-seiryu-to (Xiao-Qing-Long-Tang)" on airway inflammation in a mouse model

Effects of a Kampo (Japanese herbal) medicine "Sho-seiryu-to (SST, Xiao-Qing-Long-Tang in Chinese)", which has been used for the treatment of allergic bronchial asthma clinically, were examined on ovalbumin (OVA)-sensitized allergic airway inflammation model (i.e., bronchial asthma) in a mouse. When SST was orally administered at 0.5 g/kg/day from day 1 to 6 days after OVA inhalation, SST reduced the OVA-specific IgE antibody titer in bronchoalveolar lavage (BAL) fluids at 7 days after the OVA inhalation. CD4(+) T cells obtained from the mouse lung produced more interleukin (IL)-4 and IL-5 but less interferon (IFN)-gamma than T cells from nonsensitized control animals. However, oral administration of SST reduced the production of IL-4 and IL-5 and the production of IFN-gamma returned to the control level. In addition, the IL-4 level was increased in the BAL fluid of the OVA-sensitized animals compared to the nonsensitized control, while the IFN-gamma levels decreased. SST reduced the IL-4 levels in the BAL fluids and returned the IFN-gamma level to control levels. Nerve growth factor (NGF) was increased in the BAL fluids of the OVA-sensitized mice over that of nonsensitized mice, but oral administration of SST augmented the NGF levels to approximately 2 times higher than in the sensitized mice. Although lung cells obtained from sensitized mice produced higher levels of NGF than nonsensitized mice, oral administration of SST augmented the production of NGF by the lung cells even higher ( approximately 2 times more than cells from sensitized mice). Administration of anti-NGF antibody to the airway blocked the effects of SST. These results suggest that SST modulates Th1/Th2 balance in the lungs and augmentation of NGF in the lungs may be related to the effects of SST. Pinellic acid (9S, 12S, 13S-trihydroxy-10E-octadecenoic acid), one component of the herbs of SST [Int. Immunopharmacol. 2 (2002) 1183], was purified from the tuber of Pinellia ternata Breitenbach. Oral administration of pinellic acid (50 microg/kg/day) also reduced the OVA-specific IgE antibody titer in BAL fluids from the sensitized mouse. This result suggests that pinellic acid is one of active ingredient(s) in SST.

Cytokine regulation of pulmonary fibrosis in scleroderma

Pulmonary fibrosis occurs in up to 70% of scleroderma patients and progresses to cause severe restrictive lung disease in about 15% of patients. The mechanisms that cause pulmonary fibrosis in scleroderma remain incompletely understood. Increased amounts of mRNA or protein for multiple profibrotic cytokines and chemokines have been identified in lung tissue or broncholveolar lavage samples from scleroderma patients, when compared to healthy controls. These cytokines include transforming growth factor (TGF)-beta, connective tissue growth factor (CTGF), platelet-derived growth factor (PDGF), oncostatin M (OSM), monocyte chemotactic factor-1 and pulmonary and activation-regulated chemokine (PARC). Potential cellular sources of these profibrotic cytokines and chemokines in scleroderma lung disease include alternatively activated macrophages, activated CD8+ T cells, eosinophils, mast cells, epithelial cells and fibroblasts themselves. This review summarizes the literature on involvement of cytokines and chemokines in the development of pulmonary fibrosis in scleroderma.

Mast cells as a target of rheumatoid arthritis treatment

Rheumatoid arthritis (RA) is a chronic inflammatory disease and its exact cause and pathophysiological process remain unclear. Fibroblast-like synoviocytes, macrophages and T lymphocytes are considered to be the major contributors in the pathophysiological process of RA; however, an increasing number of papers have drawn attention to the potential role of mast cells (MCs) in the process. In an animal model of RA, we reported an increase in MC numbers in the arthritic region, which agreed with the observation in human RA. In addition, a good correlation between the number of MCs and the development of disease was observed. However, there has been little experimental or clinical evidence of the beneficial effects of the modification of MC activity on the pathogenesis of RA and this is the weak point of the hypothesis. We therefore studied the effects of a MC-stabilizing compound, cromoglicate lisetil (CL), which is an orally deliverable prodrug of cromolyn sodium, on the RA disease model. The MC-stabilizer had efficacy in a mouse model. The beneficial effects of CL in this animal model further suggested the contribution of MCs in the pathophysiological process of RA. Concerning the contributive mechanism of MC on the pathogenesis of RA, our results using a disease model suggested that activation of MC chymase and matrix metalloproteinases might be involved. MC is now considered to be one of the targets of RA treatment.

Human mast cells stimulate fibroblast proliferation, collagen synthesis and lattice contraction: a direct role for mast cells in skin fibrosis

BACKGROUND

Mast cells, the key cells of immediate hypersensitivity type reactions, have also been postulated to have a central role in influencing tissue remodelling and fibrosis occurring in the skin.

OBJECTIVE

Our aim was to investigate the direct role of human mast cells (HMC) in skin fibrotic processes, by assessing the effects of the addition of the human mast cell line HMC-1 to human skin fibroblasts, and to identify the responsible mediators.

METHODS

HMC-1 sonicates were added to human skin fibroblasts and the following parameters were evaluated: proliferation ([3H]-thymidine), collagen synthesis ([3H] proline), activity of matrix metalloproteinases (MMPs) (zymography) and tissue inhibitors of metalloproteinases (TIMPs) (reverse zymography), and collagen gel contraction.

RESULTS

HMC-1 sonicate increased significantly both proliferation and collagen production in the human skin fibroblasts and these properties were not affected by heating of the sonicate (56 degrees C, 30 min, or 100 degrees C, 3 min). Two main mast cell mediators, histamine and tryptase, were found to be responsible for the increase in fibroblast proliferation and collagen production. HMC-1 sonicate did not display any pre-formed gelatinase activity, and its addition to the fibroblasts did not change their pro-MMP-2 and MMP-2 activity. On the other hand, HMC-1 were found to possess TIMP-1 and TIMP-2. Addition of HMC-1 had no effect on fibroblasts TIMP-1 but induced a dose-dependent increase of TIMP-2 activity. In addition, HMC-1 sonicate seeded together with the fibroblasts in tri-dimensional collagen gel significantly enhanced their contraction.

CONCLUSION

We have shown that human mast cells, by granule-stored and therefore quickly releasable mediators, increase human skin fibroblast proliferation, collagen synthesis, TIMP-2 and collagen gel contraction. Therefore, mast cells have a direct and potentiating role in skin remodelling and fibrosis.

The mast cell in wound healing

This review describes the role of the mast cell in the pathobiology of skin healing. After illustrating its main morphofunctional characteristics, with special reference to the dog and cat, we consider the involvement of the mast cell in the various phases of skin repair. With the aid of a wide array of newly formed or preformed mediators released by degranulation, the activated mast cell controls the key events of the healing phases: triggering and modulation of the inflammatory stage, proliferation of connective cellular elements and final remodelling of the newly formed connective tissue matrix. The importance of the mast cell in regulating healing processes is also demonstrated by the fact that a surplus or deficit of degranulated biological mediators causes impaired repair, with the formation of exuberant granulation tissue (e.g. keloids and hypertrophic scars), delayed closure (dehiscence) and chronicity of the inflammatory stage.

Nerve growth factor displays stimulatory effects on human skin and lung fibroblasts, demonstrating a direct role for this factor in tissue repair

Nerve growth factor (NGF) is a polypeptide which, in addition to its effect on nerve cells, is believed to play a role in inflammatory responses and in tissue repair. Because fibroblasts represent the main target and effector cells in these processes, to investigate whether NGF is involved in lung and skin tissue repair, we studied the effect of NGF on fibroblast migration, proliferation, collagen metabolism, modulation into myofibroblasts, and contraction of collagen gel. Both skin and lung fibroblasts were found to produce NGF and to express tyrosine kinase receptor (trkA) under basal conditions, whereas the low-affinity p75 receptor was expressed only after prolonged NGF exposure. NGF significantly induced skin and lung fibroblast migration in an in vitro model of wounded fibroblast and skin migration in Boyden chambers. Nevertheless NGF did not influence either skin or lung fibroblast proliferation, collagen production, or metalloproteinase production or activation. In contrast, culture of both lung and skin fibroblasts with NGF modulated their phenotype into myofibroblasts. Moreover, addition of NGF to both fibroblast types embedded in collagen gel increased their contraction. Fibrotic human lung or skin tissues displayed immunoreactivity for NGF, trkA, and p75. These data show a direct pro-fibrogenic effect of NGF on skin and lung fibroblasts and therefore indicate a role for NGF in tissue repair and fibrosis.

Isoform-selective upregulation of mast cell chymase in the development of skin fibrosis in scleroderma model mice

The involvement of connective-tissue-type mast cells and chymase, a protease unique to their secretory granules, has been implicated in fibrotic diseases. To elucidate the role of chymase in fibroproliferative inflammation, in this study we examined the enzymatic activity and mRNA expression of chymase in the sclerotic skin of tight-skin mice; syngeneic Pallid mice served as the control. Dorsal skin specimens from mice aged 5, 10, and 20 wk were evaluated by morphometric and biochemical analyses. At ages 10 and 20 wk, the hydroxyproline concentration in tight-skin dermis was higher than that in Pallid. At any age, the subcutaneous fibrous layer was thicker in tight-skin than in Pallid. In accordance with these fibrous changes, both connective-tissue-type mast cell counts and chymase activity were higher in tight-skin skin than in Pallid skin up to 20 wk of age. Age-matched (10-wk-old) tight-skin and Pallid were quantified for their mRNA of connective-tissue-type mast-cell-specific chymase, mouse mast cell protease-4, by the competitive reverse transcriptase polymerase chain reaction technique, which revealed its higher level in tight-skin than Pallid. In contrast, the mRNA level of mouse mast cell protease-5, the chymase isoform of undifferentiated mast cells, in tight-skin skin was only a tenth that of mouse mast cell protease-4 and no different from the mouse mast cell protease-5 mRNA level of Pallid mice. An in situ hybridization study confirmed the higher expression of mouse mast cell protease-4 by connective-tissue-type mast cells in tight-skin skin than Pallid skin. These results strongly support the contention that the connective-tissue-type mast cell chymase plays a crucial role in fibroproliferative remodeling of the skin.

The role of the immune system in conjunctival wound healing after glaucoma surgery

The immune system has a fundamental role in the development and regulation of ocular healing, which plays an important role in the pathogenesis of most blinding diseases. This review discusses the mechanisms of normal wound healing, describing the animal and fetal wound healing models used to provide further insight into normal wound repair. In particular, conjunctival wound repair after glaucoma filtration surgery will be used to illustrate the contributions that the different components of the immune system make to the healing process. The potential role of macrophages, the possible regulatory effect of lymphocytes, and the important role of growth factors and cytokines in the wound healing reaction are discussed. The significance of the immune system in the pathogenesis of aggressive conjunctival scarring is addressed, particularly assessing the predisposing factors, including drugs, age, and ethnicity. The rationale behind the pharmacological agents currently used to modulate the wound healing response and the effects these drugs have on the function of the immune system are described. Finally, potential new therapeutic approaches to regulating the wound healing response are reported.

Mast cells are not involved in the development of cyclosporin A-induced gingival hyperplasia: a study with mast cell-deficient mice

BACKGROUND

A previous study suggested that mast cells (MC) are involved in the development of cyclosporin A-induced gingival hyperplasia, since an increased number of MC were observed in the tissue sections of enlarged gingiva. To determine the role of MC in gingival hyperplasia, an MC-deficient mouse model was used in the current study.

METHODS

MC-deficient mice (WBB6F1xW/Wv) and their littermates (+/+) were fed sucrose-containing diets supplemented with or without varying concentrations (300, 400, 500, 600 mg) of cyclosporin A/kg of diet. After 30 days, the mice were sacrificed and the degree of gingival hyperplasia was evaluated by the appearance of the gingiva. Tissue MC were stained with toluidine blue to confirm the presence or absence of MC in the enlarged gingiva.

RESULTS

Both W/Wv and +/+ mice, when fed with 600 mg cyclosporin A/kg diet for 30 days, exhibited a similar degree of gingival hyperplasia, while other test mice or control mice did not. Toluidine blue staining of the tissue sections confirmed the presence of MC in the enlarged gingiva of the +/+ mice, but not the W/Wv mice.

CONCLUSIONS

These results indicate that mast cells are not necessary in the development of cyclosporin A-induced gingival hyperplasia, and that the increased number of MC observed in the enlarged gingiva may be a secondary effect of gingival hyperplasia. We also conclude that a study of mice lacking certain molecules or cells would be quite useful in determining the molecules or cell types responsible for the pathogenesis of drug-induced gingival hyperplasia.

Mast cell involvement in normal human skin wound healing: expression of monocyte chemoattractant protein-1 is correlated with recruitment of mast cells which synthesize interleukin-4 in vivo

Mast cells (MCs) are known as key cells of immediate type hypersensitivity reactions. It has recently been shown that MCs regulate fibroblast proliferation by heterotypic cell-cell contact and secretion of interleukin-4 (IL-4) in vitro. It was therefore hypothesized that MCs may contribute to wound repair in vivo. Using immunohistology and in situ hybridization, the time course of mast cell recruitment and the expression of MC-attractant chemokines were analysed in a human skin wound-healing model, and the production of IL-4 by MCs in vivo was investigated. The data obtained indicate that the five-fold increase of the tryptase+ MCs at the fibrotic border of the wound within the first 10 days is the result of increased recruitment/survival of MCs or MC precursors, but not of increased local proliferation. Recruitment of MCs is paralleled by the expression of monocyte chemoattractant protein-1 (MCP-1), but not by other chemokines such as RANTES (regulated on activation, normal T cell expressed and secreted) and/or MIP (macrophage inflammatory protein)-1alpha/beta. Notably, 60-70% of MCs exhibited strong and selective IL-4 immunoreactivity, whereas other resident and passenger cells were rather quiescent. The data suggest that MC contribute significantly to the cytokine network of wound repair via MC-derived IL-4 and stimulation of fibroblast proliferation.

Giant cell fibroblastoma: an entity or a reactive phenomenon?

The histological and immunohistochemical features of four tumors displaying the characteristic pattern of Giant Cell Fibroblastoma (GCF) are presented. Three of them were found in association with classical and/or myxoid dermatofibrosarcoma protuberans, while the fourth tumor was a retroperitoneal malignant hemangiopericytoma where foci with features of GCF were found. Typical sinusoidal spaces and the bizarre mononuclear and multinucleated cells in close association to blood vessels presenting a wide spectrum of lesions of their walls are also described. These last changes led us to believe that GCF-like lesions might not always characterize an entity but could often represent a host reaction of the connective tissue to locally aggressive or malignant tumors.

Histamine effects on conjunctival fibroblasts from patients with vernal conjunctivitis

Histamine, an important mast cell mediator in allergic disorders, may affect extracellular matrix production and cell growth in vernal keratoconjunctivitis (VKC). In the present study, the histamine reactivity of conjunctival fibroblasts derived from VKC patients was investigated in vitro. Conjunctival fibroblast cultures were derived from biopses of 8 tarsal VKC patients and 5 normal subjects. These cells were maintained in vitro and stimulated with different concentrations of histamine with and without H1 (clorpheniramine) and H2 (cimetidine) receptor antagonists. Comparisons were made to fibroblasts grown in the same media without histamine and to fibroblasts stimulated with just antihistamine. The effects of histamine were evaluated by: (1) the MTT test to assess cell proliferation; (2) an in vitro wound model for cell migration and (3) the measurement of procollagen I (PIP) and procollagen III (PIIIP) in supernatants for collagen production. Results showed: (1) While VKC-derived fibroblasts proliferated at a faster rate than normal cells in unstimulated media, after histamine stimulation, VKC and normal cells grew at a similar rate. Both H1 and H2 antagonists significantly inhibited (P<0.05) histamine-induced cell proliferation. (2) Histamine enhanced cell migration after wounding; this effect was inhibited only by H2 antagonism. (3) When stimulated with histamine, VKC fibroblasts produced significantly more PIP than those in control media. Furthermore, VKC-derived fibroblasts were more sensitive to histamine challenge, producing significantly more PIP than normal fibroblasts. H1 and H2 antagonists did not modify histamine-stimulated PIP production. The enhanced proliferative and productive capacity of VKC fibroblasts may be the result of a selective overgrowth of one or more fibroblast subpopulations in a chronically inflamed tissue. Histamine increased proliferation, migration and collagen production in both normal and VKC fibroblasts. Since H2 antagonism modulated both cell growth and migration, but not histamine-induced collagen production, the latter may be mediated by a different receptor. These results showed that histamine is at least partially responsible for fibroblast stimulation.

Expression of midkine in normal and burn sites of rat skin

Expression of midkine (MK), a retinoic acid-inducible heparin binding growth factor, was examined immunohistochemically in normal and burn sites of rat skin. In the normal skin, MK was localized in the epidermis and dermal appendages such as hair follicles and sebaceous glands. Mast cells in the subdermal connective tissue also accumulated MK. After burn injury, MK-positive cells began to infiltrate into subdermal connective tissue, and the number of MK-positive cells in the region increased to a maximum at postburn day two and then decreased gradually. Western blotting analysis of both normal and postburn skin revealed a 30 kDa band reactive with anti-MK antibody; this band was concluded to be a dimer of MK. These findings were discussed from the viewpoint of the possible role of MK in wound healing.

Mast cells and their mediators in cutaneous wound healing--active participants or innocent bystanders?

Mast cells are traditionally viewed as effector cells of immediate type hypersensitivity reactions. There is, however, a growing body of evidence that the cells might play an important role in the maintenance of tissue homeostasis and repair. We here present our own data and those from the literature elucidating the possible role of mast cells during wound healing. Studies on the fate of mast cells in scars of varying ages suggest that these cells degranulate during wounding, with a marked decrease of chymase-positive cells, although the total number of cells does not decrease, based on SCF-receptor staining. Mast cells contain a plethora of preformed mediators like heparin, histamine, tryptase, chymase, VEGF and TNF-alpha which, on release during the initial stages of wound healing, affect bleeding and subsequent coagulation and acute inflammation. Various additional vasoactive and chemotactic, rapidly generated mediators (C3a, C5a, LTB4, LTC4, PAF) will contribute to these processes, whereas mast cell-derived proinflammatory and growth promoting peptide mediators (VEGF, FGF-2, PDGF, TGF-beta, NGF, IL-4, IL-8) contribute to neoangiogenesis, fibrinogenesis or re-epithelization during the repair process. The increasing number of tryptase-positive mast cells in older scars suggest that these cells continue to be exposed to specific chemotactic, growth- and differentiation-promoting factors throughout the process of tissue remodelling. All these data indicate that mast cells contribute in a major way to wound healing. their role as potential initiators of or as contributors to this process, compared to other cell types, will however have to be further elucidated.

Influence of antiestrogens on the migration of breast cancer cells using an in vitro wound model

The metastasis of malignant tumor cells to other organs in the body is the major cause of cancer-related patient mortality. Therefore, the inhibition of tumor cell motility is critical in the prevention or control of tumor malignancy. In the present study, the antimetastatic potential of antiestrogens [tamoxifen (TAM); ICI-182,780 (ICI); and Analog II (AII)] on highly invasive, estrogen receptor (ER)-negative MDA-MB-231 (MDA) and non-invasive, ER-positive MCF-7 (MCF) human breast cancer cell lines was investigated using an in vitro wound model. Wounds were created in confluent cell cultures and repopulation of the wound space was evaluated by counting the number of cells that migrated into the wound area and by measuring the maximum distance traveled. In addition, the number of cells that were passively seeded into the wounded area was determined. ICI and AII reduced the number of MCF cells that migrated into the wounded area and reduced the number of viable passively seeded MDA cells. Unlike ICI and AII, TAM appeared to enhance MCF and MDA cell movement. This study indicates that the in vitro wound technique is applicable to the study of breast cancer cell movement in response to antiestrogens and other antimetastatic agents. It also demonstrates that antiestrogens differ in their influence on breast cancer cell migration.

Mast cells, eosinophils and fibrosis

We have presented results that increase our understanding of the roles MC and EOS play in modulating fibrotic processes. In vitro studies have provided clear-cut evidence for the direct involvement of these two inflammatory cells in enhancing proliferation, and either enhancing or decreasing collagen synthesis in human fibroblasts isolated from different anatomical locations. In addition, we have shown that MC and EOS interactions can also take part in modulating fibrosis. In vivo studies in murine and human cGVHD showed that MC activation is detrimental, and that MC stabilization therapy may be helpful in treating the fibrotic outcome of this disease. Much is still obscure. It is, for example, important to define the MC and EOS mediators involved in the modulation of fibroblast properties, and their pattern of influence, keeping in mind the ultimate goal of defining new therapeutic targets for the treatment of fibrotic diseases.

Mast cells and type VIII collagen in human diabetic nephropathy

Renal injury in diabetes mellitus is associated with progressive interstitial fibrosis and extracellular matrix accumulation. However, the phenotypes of cells forming the interstitial infiltrate in diabetic nephropathy have not been precisely defined. There is increasing evidence for the association of mast cells with angiogenesis, chronic inflammatory conditions and fibrosis. We have recently shown that human mast cells can produce the non-fibrillar short chain type VIII collagen in vivo. Using immunohistochemistry, in situ hybridisation and reverse transcriptase-polymerase chain reaction, we examined the contribution of mast cells and type VIII collagen to the fibrotic changes occurring in biopsy-proven diabetic nephropathy. We observed that the number of interstitial mast cells was significantly increased in diabetic nephropathy compared with normal kidney tissue. In specimens from diabetic subjects, intense immunohistochemical staining for type VIII collagen was detected in mast cells, on periglomerular fibres and in perivascular and interstitial sites. The expression of type VIII collagen in periglomerular and interstitial sites coincided with that of alpha smooth muscle actin, a marker for myofibroblastic differentiation mRNA for type VIII collagen was detected by reverse transcriptase-polymerase chain reaction in diabetic nephropathy and in a human mast cell line. By in situ hybridisation the transcripts for type VIII collagen were localised to renal mast cells. The increased number of mast cells and the elevated type VIII collagen deposition in human diabetic nephropathy provides a potential link between the extracellular matrix accumulation and the fibrosis observed in this condition.

Topical tretinoin increases dermal mast cells, induces epidermal mast cell growth factor (c-kit ligand) and modulates its distribution in hairless mice

In previous studies we have noted that mast cells are increased in tretinoin-treated photoaged hairless mouse skin. Because UV radiation is known to increase mast cell numbers, we were interested in whether tretinoin alone would modulate the mast cell population in unirradiated mice. Animals were treated topically with 0.05% tretinoin, 5 days a week, for 2, 4, 6, 8 and 10 weeks. Untreated and vehicle controls were included. Biopsies were processed for light microscopy and stained with toluidine blue. Mast cells in the upper and lower dermis were scored separately under high magnification. After 2 weeks of tretinoin, mast cells in the upper dermis were significantly increased, as indicated by the appearance of small, moderately metachromatically granulated cells near the dermal-epidermal junction. Mast cells in the lower dermis, the site of a granulomatous reaction, were large, densely granular and significantly increased after 6 weeks of treatment. Immunohistochemical evaluation for mast cell growth factor (MGF) revealed a marked increase in keratinocyte cytoplasmic staining by week 2. After 4-6 weeks, membrane-associated or intercellular staining was evident. Cells in the upper dermis also showed membrane reactivity for MGF. By 8-10 weeks, epidermal MGF reactivity had dissipated in the more basal keratinocytes. These findings show that topical tretinoin can induce epidermal MGF along with an associated mast cell hyperplasia. It is suggested that the two populations of dermal mast cells may have different functions.