Intradermal mast-cell secretion causing cutaneous mitogenesis

On Connective Tissue Mast Cells as Protectors of Life, Reproduction, and Progeny

The connective tissue mast cell (MC), a sentinel tissue-residing secretory immune cell, has been preserved in all vertebrate classes since approximately 500 million years. No physiological role of the MC has yet been established. Considering the power of natural selection of cells during evolution, it is likely that the MCs exert essential yet unidentified life-promoting actions. All vertebrates feature a circulatory system, and the MCs interact readily with the vasculature. It is notable that embryonic MC progenitors are generated from endothelial cells. The MC hosts many surface receptors, enabling its activation via a vast variety of potentially harmful exogenous and endogenous molecules and via reproductive hormones in the female sex organs. Activated MCs release a unique composition of preformed and newly synthesized bioactive molecules, like heparin, histamine, serotonin, proteolytic enzymes, cytokines, chemokines, and growth factors. MCs play important roles in immune responses, tissue remodeling, cell proliferation, angiogenesis, inflammation, wound healing, tissue homeostasis, health, and reproduction. As recently suggested, MCs enable perpetuation of the vertebrates because of key effects-spanning generations-in ovulation and pregnancy, as in life-preserving activities in inflammation and wound healing from birth till reproductive age, thus creating a permanent life-sustaining loop. Here, we present recent advances that further indicate that the MC is a specific life-supporting and progeny-safeguarding cell.

Do Mast Cells Contribute to the Continued Survival of Vertebrates?

This study is an attempt to shed light on why the connective tissue mast cell (MC) is preserved in all species with a blood circulatory system, i.e., the vertebrates since >500 million years, which suggests that the MC performs as yet not understood indispensible life‐promoting actions. The literature survey focuses on data in published papers on MC functions in immunological and nonimmunological reactions, host protection, pregnancy, inflammation, and wound healing. All data are thus accessible to the reader. The MC is a secretory cell with a unique mediator profile. A distinctive role for MCs is defined not only by their extensive mediator composition but also by their prominent ability to affect the vasculature to expedite selective cell recruitment and permeability changes and to set the stage for an appropriate acquired response. MCs, harboring a wide range of surface membrane receptors, are activated by the major female sex hormones as well as by diverse potentially adverse stimuli. MC activation/degranulation creates a presumably unique triad tissue response in physiological and pathological situations alike: extracellular matrix degradation and tissue remodeling, de novo cell proliferation, and de novo angiogenesis. As shown in the literature, MC‐activation is crucial for successful female reproduction in the mouse, implying one of possibly several yet unidentified physiological roles of MCs. Moreover, the activated MC aids newborns to survive to reproductive age owing to its key beneficial actions in inflammation and wound healing. Thus, a not previously described life‐perpetuating loop spanning generations are apparently formed, which, hypothetically, could contribute to the continued survival of the vertebrates.

Mast cell tryptase does not alter matrix metalloproteinase expression in human dermal fibroblasts: further evidence that proteolytically-active tryptase is a potent fibrogenic factor

There is compelling in vitro and in vivo evidence to implicate mast cells in the development of fibrosis. However, an important question remains as to the mechanisms by which mast cells mediate fibrosis. Recent evidence from our laboratory (Gruber et al., 1997, J. Immunol. , 158:2310-2317) has revealed that tryptase, the unique and abundant serine protease of human mast cells, is capable of activating fibroblasts by stimulating chemotaxis, proliferation, and procollagen mRNA synthesis. Regulation of matrix metalloproteinase (MMP) expression is another key step in connective tissue remodeling. Therefore, the effect of tryptase on fibroblast MMP expression was investigated. Proteolytically active tryptase did not alter the cellular mRNA levels for fibroblast MMP-1, MMP-2, MMP-3, and MMP-9 as detected by RNase protection assays. Moreover, tryptase did not alter the basal levels of MMP-1, MMP-2, MMP-3, MMP-9, or the tissue inhibitor of MMP-1 (TIMP-1) in fibroblast conditioned media as detected by specific enzyme-linked immunosorbent assay (ELISA). These results indicate that tryptase does not increase MMP expression in normal dermal fibroblasts. Moreover, these data strengthen the potential role of this unique serine protease as a potent fibrogenic factor.

Murine acariasis: I. Pathological and clinical evidence suggesting cutaneous allergy and wasting syndrome in BALB/c mouse

We describe here a disease related to mite-associated ulcerative dermatitis in BALB/c mice, a strain previously classified as resistant to this condition. The disease was recognized by pruritic cutaneous pathology and wasting. Pathologic studies showed a marked allergic-type inflammation in the skin. The dominant histologic feature was extensive mast cell infiltration in cutaneous lesions and in lymphoid tissues, associated with a greatly elevated serum IgE concentration. The disease was secondary to infestation with an acarian ectoparasite Myocoptes musculinus, and seemed to represent an allergic reaction to the parasite-derived substances, with an associated wasting syndrome. This condition may be a useful experimental model for allergic diseases.

Bromodeoxyuridine labeling studies on the proliferation of intestinal mucosal mast cells in normal and athymic rats

The proliferation of mucosal-type mast cells (MMC) in rat small intestine was studied using a bromodeoxyuridine (BrdU)-labeling method. After 24-h cumulative injections of BrdU into adult SD rats, 3.5% of MMC were labeled, while only 0.3% and 0.1% of mast cells were labeled in back skin and ear respectively. From the results, it was concluded that MMC division occurred more than 10 times as frequently as the division of skin mast cells. Similar results were obtained in athymic adult rats (F344/N Jcl-rnu) in which the number of MMC was similar to that in heterologous animals. Thus, thymic factor(s) or T cells may not have an important role in MMC division in normal states. When SD rats were infected with Nippostrongylus brasiliensis, vigorous proliferation of MMC was brought about 13 to 15 days after infection. At that period, 40% of MMC were labeled by a single injection of BrdU, and 85% of MMC were labeled by 9-h cumulative injections of BrdU, with the result that most MMC rapidly proliferated in the intestinal mucosa during this period. Mitotic figures of MMC were sometimes observed. On the contrary, hyperplasia of MMC was not observed in athymic rats infected with nematodes. Therefore, MMC hyperplasia after nematode infection is dependent on thymic factor or T cells, and its mechanism is different from that of MMC division in normal states, in which thymic factor(s) or T cells are not essential.

On mast cell-mediated mitogenesis in normal and hyperplastic mesenterial windows in female rats

The outcome of the mast cell-mediated mitogenesis in hyperplastic membranous mesenterial windows of lactating rats as well as in normal mesenterial windows of age-matched and young virgin female rats was studied quantitatively in vivo and in organ culture. Besides elucidating the effect of age and tissue hyperplasia on mitogenic responsiveness, this approach should provide some insight into the pathogenic mechanics of the previously reported supranormal mast cell-mediated mitogenic reaction that emerges in similarly hyperplastic mesenterial windows of diabetic rats. Mast cell secretion was elicited by Compound 48/80 and the histamine release, which was quantified fluorometrically, was unaffected by lactation. The young female rats showed a statistically significant mast cell-dependent mitogenesis taken as the mitotic index and the fraction of the predominating fibroblasts and mesothelial cells in the (S+G2) cell cycle phases after Feulgen-DNA absorption analysis of the cells in situ. Although there was an age-dependent decrease in mitogenesis, the older lactating and non-lactating virgin control rats also showed mast cell-mediated mitogenesis measured as the specific DNA activity. The hyperplastic mesenterial tissue of the lactating animals showed a virtually normal mitogenic reactivity following local mast cell secretion, but at a lower level than in the age-matched controls. This finding suggests that the supranormal mast cell-mediated mitogenesis previously found in the hyperplastic mesenterial windows of diabetic animals is causally related to the diabetic condition rather than to the hyperplastic state of the test tissue.

Hyaluronic acid in bronchoalveolar lavage fluid in patients with sarcoidosis: relationship to lavage mast cells

Hyaluronate (hyaluronic acid), a potential marker for activated pulmonary fibroblasts, appears in increased concentrations in bronchoalveolar lavage fluid from patients with sarcoidosis. The mechanisms underlying fibroblast proliferation are largely unknown but activated alveolar T lymphocytes and macrophages probably play a part; the mast cell is also important for fibroblast proliferation. This study was designed to determine whether there is any association between pulmonary mast cells in lavage fluid, which are known to be increased in patients with sarcoidosis, and signs of pulmonary fibroblast activation. A strong correlation was found between lavage fluid hyaluronate and recovered mast cells (r = 0.72, p less than 0.001). Moreover, mast cell and hyaluronate estimations correlated inversely with lung volume and transfer factor for carbon monoxide, and both indices increased with advancing radiological sarcoid stage. Macrophage and granulocyte counts were normal in lavage fluid from patients with sarcoidosis and were not related to lavage fluid hyaluronate or laboratory signs of the disease in the lungs. Lymphocytes were recovered in increased numbers (p less than 0.001) and were related to the lavage fluid mast cells and hyaluronate. It is concluded that in sarcoidosis release of hyaluronate into the airways is related to the degree of lung disease and to the local inflammatory reaction in the lung as defined by increased numbers of mast cells and lymphocytes in lavage fluid. The findings may reflect a link between the immune system, activation of mast cells, and a pulmonary fibroblast proliferation.

Kinetics of mast cell, fibroblast, and epidermal cell proliferation during acute graft-versus-host disease in the neonatal rat

Acute graft-versus-host disease (GVHD) was induced in newborn Brown-Norway (BN) and DA rats by i.v. injection of 3 X 10(7) Lewis (L) lymph node cells. Control BN and DA rats received syngeneic cells. Rats were injected i.v. with [methyl-3H]thymidine for 1 h before being killed at 1, 2, 4, 5, 6, 8, 10, 11, 12, 13, and 14 days after the cellular inoculum. A piece of ventral abdominal skin was removed. Autoradiography was used to determine cell proliferative activity (labeling index, LI) in mast cells and fibroblasts of the dermis and basal cells of the epidermis. In addition, the number of mast cells per high-power field was determined for all 4 groups of rats: control DA, GVHD-DA, control BN, and GVHD-BN. Only GVHD-BN rats demonstrated extensive dermatitis. The LI of mast cells, fibroblasts, and basal cells decreased in control rats with increasing age. Although there were differences between DA and BN rats, there was a general pattern of increased proliferation of mast cells at early time points of GVHD followed by a decrease to or below control levels. The number of mast cells per high-power field also increased at early time intervals in both the DA and BN GVHD rats, but decreased significantly at later time points. These data confirm previous studies on chronic GVHD which demonstrated a decrease in the number of mast cells in the skin. Fibroblast LI was decreased at day 1 in both DA and BN GVHD rats. In GVHD-DA, fibroblast LI remained depressed while GVHD-BN demonstrated a second peak in LI at day 10 before declining below control levels. The most prominent basal cell response occurred in GVHD-BN between days 6-14 and is probably indicative of an attempted reparative response associated with GVHD dermatitis in this species. These data demonstrate that the activation of mast cells (proliferation and subsequent degranulation) correlates temporally with cell kinetic alterations occurring in the dermis and epidermis during acute GVHD.

Analysis of bronchoalveolar lavage fluid from bleomycin-induced pulmonary fibrosis in hamsters

The purpose of this study was to analyze the cellular and noncellular components of bronchoalveolar lavage fluid (BALF) at varying times during the development of pulmonary fibrosis induced by bleomycin. Hamsters were killed and lavaged in situ following the administration of a single intratracheal injection of 1 unit of bleomycin or an equivalent volume of sterile isotonic saline. The results show that the total cell counts in the BALF of bleomycin-treated hamsters, as compared with controls, were increased 7.7, 4.4, 2.4, 1.6, and 1.9-fold at 2, 4, 7, 14, and 21 days after treatment, respectively. The predominant cell types in the BALF of control animals were macrophages which constituted 84% of the total cells, followed by lymphocytes, 11%. The predominant cell types in the BALF of bleomycin-treated animals were polymorphonuclear leukocytes (PMN) which constituted 65% at two days and approximately 50% of the total at 4, 7, and 14 days; at 21 days macrophages were the predominant cell type constituting 50%, followed by lymphocytes at 30%. However, the total number of lymphocytes was not increased at 21 days compared to previous times. The noncellular protein content of BALF from bleomycin-treated hamsters, an index of pulmonary vascular permeability, was increased to 224, 559, 637, and 270% of control (2.7 mg/lung) at 2, 4, 7, and 14 days after treatment, respectively, and returned to control levels at 21 days. The acid phosphatase activity in the supernatant of BALF of bleomycin-treated animals was significantly increased to 181, 181, 199, 176, and 125% of control (258 units/lung) at 2, 4, 7, 14, and 21 days, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Increased number of mast cells in the testis of neonatally estrogenized rats

The presence of increased numbers of mast cells in the testis of adult neonatally estrogenized rats is reported. The histometric study revealed significant differences between control and estrogenized animals for two ages considered (45 and 90 days). This increase might be related with the development of connective tissue in estrogenized rats.

Early cellular events in pulmonary fibrosis

In this review we have surveyed recent investigations of early cellular events in pulmonary fibrosis both in animal models and in human diseases. Analysis of the interactions of the numerous cell types in the lung following injury is an almost overwhelmingly complex enterprise. In the animal models experimental design has a profound effect on results, making it difficult to compare studies when species, fibrogenic agent, dose, route of exposure, schedule of administration, time course, and analytical methods may not be equivalent. In human diseases we are rarely able to obtain data at precisely the same time point in the course of the disease even among patients in the same study, and possible confounding variables present are legion. Transcending these difficulties for the moment, can we draw any conclusions from our current knowledge of early cellular interactions in pulmonary fibrosis? What is striking is not that there are so many agents that can potentially induce pulmonary fibrosis, but that the lung has such capabilities for recovery. Although the major effector cells may all initially participate in damaging the lung and initiating fibrosis, there is evidence that they may also have the capacity to participate in subsequent repair. Macrophages may initially recruit fibroblasts and stimulate them to proliferate, only to suppress them subsequently. Macrophage production of prostaglandins can lead to suppression of macrophage, neutrophil and lymphocyte responses, thus attenuating tissue injury and the development of fibrosis. Neutrophils may initially release toxic metabolites and enzymes that damage parenchyma. However, there is evidence that they may later play a role in attenuating fibrosis, perhaps through collagenase secretion, or through as yet unknown mechanisms. Lymphocytes may initially participate in a number of damaging ways by secreting chemoattractants for other cells and participating in destructive autoimmune processes. However, there is evidence that subpopulations of T cells may dramatically shift during the course of fibrosis, leading to attenuation of the process. It may thus be useful to consider irreversible pulmonary fibrosis as the end result of a process in which the balance of normal injury/repair mechanisms is disrupted. There is clearly no single "fibrogenic event." Rather, there seem to be a number of places where disruption of balance/repair processes may begin. In diseases of unknown etiology such as sarcoidosis or IPF, loss of control may occur at the genetic level, leading to the destructive alveolitis that is the apparent precursor of fibrosis.(ABSTRACT TRUNCATED AT 400 WORDS)

Cystadenolymphoma: an immunohistochemical study with special reference to Ig E and mastcells

Cystadenolymphomas (adenolymphomas) were analysed by immunohistochemical studies for the presence of immunoglobulin A, E, G and M. The distribution pattern was examined by a quantitative analysis. The relative ratio of immunoglobulins was 31.8% (Ig A), 26.6% (Ig E), 28.6% (Ig G) and 13% (Ig M). The different compartments of the lymphoid stroma were analysed separately (subepithelial area, parafollicular area, follicular area). The distribution of mast cells was studied in a parallel approach by the toluidine blue technique. These cells were found in the stroma, but also in the epithelial parts. Our results show that the subepithelial zone in cystadenolymphomas is a region of special cellular reaction (plasma cells, mast cells). The Ig E producing plasma cells and the mastcells seem to play a special role in these tumors.

Ultrastructure of mast cells in the hyperplastic buccal mucosa of the zinc-deficient rat

As previously reported, young rats on zinc-deficient diets develop a marked epithelial hyperplasia in the mucosa of the cheek, associated with a four-fold increase in the number of mast cells in the lamina propria. We now report the results of a quantitative and qualitative ultrastructural study of these mast cells. In contrast to the cells in mast cell-related disease, the cells were of normal morphology, but of consistently increased size, containing proportionally increased numbers of mitochondria and specific granules. The size distribution of the granules was as in controls. Microvilli were lengthened in proportion to the increase in the cell circumference. The number of nuclear pores was increased but their spacing was as in controls. In all these measurements, the experimental mast cells were a remarkably homogeneous population. We conclude that mast cells are capable of developing into cells of larger size showing evidence of greater activity. It may be that this development occurs in response to the same (unknown) stimulus which causes their number to increase. By virtue of their increased number and size, mast cells may play an important role in the enhancement of the microcirculation commonly seen in conditions of epithelial hyperplasia.

Evidence of mast-cell histamine being mitogenic in intact tissue

We have reported previously that secretion by connective tissue mast cells (MCs) causes mitogenesis in adjacent cells in diverse rat tissues. In cultured rat mesentery there was a spontaneous release of about 45% of the histamine in 2 days, and a spontaneous marked increase in basal proliferation of the mesentery. The MC secretagogues, compound 48/80 and polymyxin B, released additional histamine and stimulated mitogenesis further. In contrast, 48/80 added to cultures of guinea-pig mesentery, the MC of which are unresponsive to the drug, did not affect the basal proliferation. However, exogenous histamine at 10(-10) M mitogenically stimulated the cultured guinea-pig mesentery. A histamine H2-receptor antagonist, which itself was mitogenically inert, significantly suppressed the 48/80-induced MC-mediated mitogenesis in rat mesentery in vivo and in vitro. On the other hand, a histamine H1-receptor antagonist did not affect this MC-mediated mitogenesis in rat. Our findings indicate that histamine is one of possibly several mitogens which are released or activated by the secreting MC.

Time-course and rate of healing after wounding the avascular mesentery in diabetic rats

The effects of inflicting trauma on the mesentery of diabetic and control rats by perforation with a scalpel were studied with regard to time-course of healing and rate of healing by closure. In this tissue, which is virtually free from blood vessels and nerves, healing precedes vascularization of the wound area. Insulin-deficient rats with streptozotocin diabetes of 4 weeks' duration were used. Non-specific histamine release and cell proliferation (expressed as specific DNA activity) lasting 30 h took place after opening the abdomen and handling the mesentery. Wounding caused further histamine release and cell proliferation. These variables were the same in diabetic and control rats. The time-course of healing was significantly delayed in diabetes, whereas the rate of healing (number of wound closures per day) during the phase of rapid healing was not. Because the rate of healing was normal in diabetic rats the impairment of healing in diabetes can be ascribed to pre-healing reparative events unrelated not only to vascular and neural factors but apparently also to the amount of histamine released and to the cell proliferation elicited by wounding. The delayed healing thus seems to be related to some cellular or metabolic feature of diabetes as yet unknown.

Tumor-bearing depresses distant mast-cell-mediated mitogenesis

A methylcholanthrene-induced sarcoma grafted subcutaneously in rats was used in early transplantation generations. Tumor-bearing rats showed weight loss compatible with cachexia. Healthy rats of the same age served as controls. In tumor-bearing rats the basal mesenteric proliferation was unaffected whereas the strictly mast-cell-mediated hyperproliferative reaction in the mesentery was significantly reduced after intraperitoneal injection of the mast-cell-secretagogue compound 48/80, as judged from specific DNA activity and mitosis counting. However, in mesentery and peritoneal lavage the number of mast cells, their histamine-releasing capacity, and their content of histamine, 5-hydroxytryptamine and heparin were unaffected by tumor-burden. The findings suggest the presence of a tumor-associated systemic factor of unknown nature which interferes with the biochemical events leading to the mast-cell-dependent mitogenesis. Since this mitogenic reaction may normally compensate for injury at the cellular level it is questioned whether the decreased mast-cell-dependent proliferation in tumor-bearing is a component of cachexia.

On disturbance of homeostasis in organ-cultured tissue

The intact membranous rat mesentery was cultured in Eagle's minimum essential medium containing no serum or only low concentrations of serum. The procedure is in some important respects superior to previous organ culture techniques. To estimate the extent of disturbance of homeostasis of the tissue in culture, the spontaneous mast-cell histamine release was quantitated after preculture preparation of the specimens and after different intervals in culture. Also, the proliferation of fibroblasts and mesothelial cells that predominate in the mesentery was assessed at 48 h by cytofluorometric quantitation of DNA in single-tissue cells. Spontaneous histamine release was time dependent during cultivation, amounting to ca. 50% at 48 h, and was affected by the medium used for moistening the tissue before cultivation. Culturing also brought about great spontaneous increase in the proliferation of fibroblasts and mesothelial cells, the rate being related to the concentration of serum. Addition of the mast-cell secretagogues 48/80 or polymyxin B at 1 h caused rapid release of 50 to 60% of the histamine and was followed by augmented proliferation in the serum-containing media. The spontaneous increase of cell proliferation in tissue culture may be causally related to mast-cell secretion. Further studies are needed to define factors influencing the spontaneous mast-cell secretion and the mast-cell-dependent mitogenesis in normal tissue cells.

Mast cells in cystadenolymphomas

Cystadenolymphomas are a special kind of salivary gland tumours with an epithelial and a stromal part. Mast cells, which in this tumour were only rarely mentioned, were observed in large amounts in the stroma and in the epithelium. This type of cell is present especially in those cystadenolymphomas rich in epithelial parts. The possible significance of this observation is discussed.

On the role of arachidonic acid metabolites in mast-cell mediated mitogenesis in the rat

We investigated whether the mitogenic response induced by local mast-cell secretion in the rat mesentery was affected by suppression of phospholipase A2, lipoxygenase, or cyclooxygenase in arachidonic acid metabolism. Enzyme inhibitor was given in a single intravenous dose 5 min before intraperitoneal injection of the mast-cell secretagogue 48/80. Mepacrine, a phospholipase A2 inhibitor, suppressed the generation of both leukotrienes (SRS) and prostaglandins (PG), whereas the lipoxygenase inhibitor BW 755C reduced the generation of SRS, and the cyclooxygenase inhibitor indomethacin significantly suppressed the generation of PG. None of the enzyme inhibitors affected the basal mesenteric histamine content or histamine release in the mesentery after exposure to 48/80, and none of them affected mast-cell-mediated mitogenesis in the mesentery as judged by specific DNA activity and mitosis counting. The stimulation of DNA synthesis and mitosis initiated by secreting mast cells is apparently not mediated or modulated by synthesis of leukotrienes, prostaglandins, or other known arachidonic acid metabolites.

Further studies on the delayed mast-cell-mediated mitogenesis in diabetic rat

We have investigated whether the delayed augmented mast-cell-dependent mitogenesis that we recently demonstrated in the true mesentery of diabetic rats may occur also in a tissue which is essentially different both functionally and structurally. Cutaneous proliferation in insulin-deficient rats following a single intradermal injection of compound 48/80 was assessed by the specific DNA activity and mitotic index, on days 7 and 28 after giving streptozotocin. The proliferation variables, which ran parallel, indicated that mast-cell secretion was not followed by proliferation on day 7, whereas there was markedly augmented proliferation on day 28. Mitosis counting showed that cell production following mast-cell secretion was significantly increased not only in the entire cutis but also in epithelial structures (epidermis and epidermal appendages). These findings are closely similar to the delayed augmentation of mast-cell-dependent mesenteric mitogenesis in diabetic rats. It is concluded that there may be a general pattern of delay in the appearance of augmented mast-cell-mediated mitogenesis in rats with chemically induced diabetes. It is questioned whether or not this delayed mitogenesis may be connected with the postponed proliferation in a variety of tissues and organs (such as arteries, eyes, and kidneys) that occurs in experimental and clinical diabetes.