Mast cells in the periprosthetic breast capsule.

BACKGROUND: Symptomatic capsular contracture occurs in about 10 % of primary breast augmentations and in more than double that rate in reconstruction after mastectomy, especially in the setting of radiation. Mast cells, traditionally associated with immune response and inflammation, secrete profibrotic mediators and may play a role in capsule formation and contracture. We analyzed the mast cell and fibroblast populations in breast capsule tissue from patients who underwent capsular excision. METHODS: Capsule tissue was collected from patients who underwent exchange of tissue expanders for permanent implants, revision of reconstruction, or revision augmentation. Breast capsule tissues were prepared for histological analyses of mast cells, fibroblasts, and collagen. Mast cells and fibroblasts were isolated from capsule tissue and screened for mediators and receptor expression. RESULTS: In breast capsule tissue, the average numbers of mast cells and fibroblasts were 9 ± 1/mm(2) and 33 ± 10/mm(2), respectively. There were significantly more mast cells on the posterior side than on the anterior side of the capsule tissue (12 ± 2 vs. 6 ± 1/mm(2), p < 0.01). Baker grade IV capsules had an increased number of fibroblasts compared to Baker grade I capsules (93 ± 9 vs. 40 ± 19/mm(2), p < 0.001). In breast capsule tissue, mast cells contained renin, histamine, and TGF-ß, and their respective receptors, AT1R, H1R, and TGF-ßRI were expressed by fibroblasts. CONCLUSION: These data indicate that within breast capsule tissue mast cells contain mediators that may activate neighboring fibroblasts. Understanding the role of mast cells in pathologic periprosthetic breast capsule formation may lead to novel therapies to prevent and treat capsular contracture. NO LEVEL ASSIGNED: This journal requires that authors assign a level of evidence to each submission to which Evidence-Based Medicine rankings are applicable. This excludes Review Articles, Book Reviews, and manuscripts that concern Basic Science, Animal Studies, Cadaver Studies, and Experimental Studies. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors http://www.springer.com/00266.

Mast cell isolation from the immature rat brain.

Mast cells are immune cells of hematopoietic origin that circulate as precursor cells prior to migration into vascularized tissues where they mature and undergo terminal differentiation in response to different cytokines within the local environment. Mast cells are well known as important regulators of inflammatory processes in peripheral tissues and recent studies support the involvement of mast cells in mediating the inflammatory response to cerebral hypoxia-ischemia in both the neonatal and adult brain. To better study mast cell function in vivo, it is important to be able to identify their environment-specific phenotype, as well as to study their interaction with other neural cells in vitro. Previous such studies of mast cells have relied on mast cells isolated from gut or bone marrow, or on a number of mast cell lines, all of which may behave differently from brain mast cells. The purpose of this study was to develop a technique for the isolation of mast cells from neonatal rat brain and to characterize these cells following hypoxia and hypoxia-ischemia. We adapted a previously described technique of coupling an antibody to the mast cell-specific FcεR1 receptor to a MACS microbead for the selective removal of intact mast cells from a neonatal brain preparation. We have isolated toluidine blue-positive brain mast cells that provide substrate for both protein analysis and in vitro studies. These cells express proteins previously used to specifically identify microglia in the brain, Iba-1 and coronin-1a. A subpopulation of mast cells in vivo also expresses Iba-1. Thus, we report a novel method for isolation of brain mast cells suitable for the study of mast cell phenotype under a variety of conditions. Further, we suggest that the use of proteins such as Iba-1 for the identification of microglia in the brain includes the caveat that mast cells may also be detected.

Mast cells are required for the development of renal fibrosis in the rodent unilateral ureteral obstruction model.

Mast cells are associated with inflammation and fibrosis. Whether they protect against or contribute to renal fibrosis is unclear. Based on our previous findings that mast cells can express and secrete active renin, and that angiotensin (ANG II) is profibrotic, we hypothesized that mast cells play a critical role in tubulointerstitial fibrosis. We tested this hypothesis in the 14-day unilateral ureteral obstruction (UUO) model in rats and mast cell-deficient (MCD) mice (WBB6F1-W/Wv) and their congenic controls (CC). In the 14-day UUO rat kidney, mast cell number is increased and they express active renin. Stabilizing mast cells in vivo with administration of cromolyn sodium attenuated the development of tubulointerstitial fibrosis, which was confirmed by measuring newly synthesized pepsin-soluble collagen and blind scoring of fixed trichrome-stained kidney sections accompanied by spectral analysis. Fibrosis was absent in UUO kidneys from MCD mice unlike that observed in the CC mice. Losartan treatment reduced the fibrosis in the CC UUO kidneys. The effects of mast cell degranulation and renin release were tested in the isolated, perfused kidney preparation. Mast cell degranulation led to renin-dependent protracted flow recovery. This demonstrates that mast cell renin is active in situ and the ensuing ANG II can modulate intrarenal vascular resistance in the UUO kidney. Collectively, the data demonstrate that mast cells are critical to the development of renal fibrosis in the 14-day UUO kidney. Since renin is present in human kidney mast cells, our work identifies potential targets in the treatment of renal fibrosis.

Interaction between sensory C-fibers and cardiac mast cells in ischemia/reperfusion: activation of a local renin-angiotensin system culminating in severe arrhythmic dysfunction.

Renin, the rate-limiting enzyme in the activation of the renin-angiotensin system (RAS), is synthesized and stored in cardiac mast cells. In ischemia/reperfusion, cardiac sensory nerves release neuropeptides such as substance P that, by degranulating mast cells, might promote renin release, thus activating a local RAS and ultimately inducing cardiac dysfunction. We tested this hypothesis in whole hearts ex vivo, in cardiac nerve terminals in vitro, and in cultured mast cells. We found that substance P-containing nerves are juxtaposed to renin-containing cardiac mast cells. Chemical stimulation of these nerves elicited substance P release that was accompanied by renin release, with the latter being preventable by mast cell stabilization or blockade of substance P receptors. Substance P caused degranulation of mast cells in culture and elicited renin release, and both of these were prevented by substance P receptor blockade. Ischemia/reperfusion in ex vivo hearts caused the release of substance P, which was associated with an increase in renin and norepinephrine overflow and with sustained reperfusion arrhythmias; substance P receptor blockade prevented these changes. Substance P, norepinephrine, and renin were also released by acetaldehyde, a known product of ischemia/reperfusion, from cardiac synaptosomes and cultured mast cells, respectively. Collectively, our findings indicate that an important link exists in the heart between sensory nerves and renin-containing mast cells; substance P released from sensory nerves plays a significant role in the release of mast cell renin in ischemia/reperfusion and in the activation of a local cardiac RAS. This culminates in angiotensin production, norepinephrine release, and arrhythmic cardiac dysfunction.

Suppression of miRNA-708 by polycomb group promotes metastases by calcium-induced cell migration.

The progression of cancer to metastatic disease is a major cause of death. We identified miR-708 being transcriptionally repressed by polycomb repressor complex 2-induced H3K27 trimethylation in metastatic breast cancer. miR-708 targets the endoplasmic reticulum protein neuronatin to decrease intracellular calcium level, resulting in reduction of activation of ERK and FAK, decreased cell migration, and impaired metastases. Ectopic expression of neuronatin refractory to suppression by miR-708 rescued cell migration and metastasis defects. In patients with breast cancer, miR-708 expression was decreased in lymph node and distal metastases, suggesting a metastasis-suppressive role. Our findings uncover a mechanistic role for miR-708 in metastasis and provide a rationale for developing miR-708 as a therapeutic agent against metastatic breast cancer.

Mast cells: a pivotal role in pulmonary fibrosis.

Pulmonary fibrosis is characterized by an inflammatory response that includes macrophages, neutrophils, lymphocytes, and mast cells. The purpose of this study was to evaluate whether mast cells play a role in initiating pulmonary fibrosis. Pulmonary fibrosis was induced with bleomycin in mast-cell-deficient WBB6F1-W/W(v) (MCD) mice and their congenic controls (WBB6F1-(+)/(+)). Mast cell deficiency protected against bleomycin-induced pulmonary fibrosis, but protection was reversed with the re-introduction of mast cells to the lungs of MCD mice. Two mast cell mediators were identified as fibrogenic: histamine and renin, via angiotensin (ANG II). Both human and rat lung fibroblasts express the histamine H1 and ANG II AT1 receptor subtypes and when activated, they promote proliferation, transforming growth factor ß1 secretion, and collagen synthesis. Mast cells appear to be critical to pulmonary fibrosis. Therapeutic blockade of mast cell degranulation and/or histamine and ANG II receptors should attenuate pulmonary fibrosis.

Targeting cardiac mast cells: pharmacological modulation of the local renin-angiotensin system.

Enhanced production of angiotensin II and excessive release of norepinephrine in the ischemic heart are major causes of arrhythmias and sudden cardiac death. Mast cell-dependent mechanisms are pivotal in the local formation of angiotensin II and modulation of norepinephrine release in cardiac pathophysiology. Cardiac mast cells increase in number in myocardial ischemia and are located in close proximity to sympathetic neurons expressing angiotensin AT1- and histamine H3-receptors. Once activated, cardiac mast cells release a host of potent pro-inflammatory and pro-fibrotic cytokines, chemokines, preformed mediators (e.g., histamine) and proteases (e.g., renin). In myocardial ischemia, angiotensin II (formed locally from mast cell-derived renin) and histamine (also released from local mast cells) respectively activate AT1- and H3-receptors on sympathetic nerve endings. Stimulation of angiotensin AT1-receptors is arrhythmogenic whereas H3-receptor activation is cardioprotective. It is likely that in ischemia/reperfusion the balance may be tipped toward the deleterious effects of mast cell renin, as demonstrated in mast cell-deficient mice, lacking mast cell renin and histamine in the heart. In these mice, no ventricular fibrillation occurs at reperfusion following ischemia, as opposed to wild-type hearts which all fibrillate. Preventing mast cell degranulation in the heart and inhibiting the activation of a local renin-angiotensin system, hence abolishing its detrimental effects on cardiac rhythmicity, appears to be more significant than the loss of histamine-induced cardioprotection. This suggests that therapeutic targets in the treatment of myocardial ischemia, and potentially congestive heart failure and hypertension, should include prevention of mast cell degranulation, mast cell renin inhibition, local ACE inhibition, ANG II antagonism and H3-receptor activation.