Distinct plasma biomarkers confirm the diagnosis of mastocytosis and identify increased risk of anaphylaxis.

BACKGROUND: Mastocytosis encompasses a heterogeneous group of disorders characterized by accumulation of clonal mast cells (MCs) in the skin and/or internal organs. Patients typically present with a broad variety of recurrent mediator-related clinical symptoms, including severe anaphylaxis. However, not all patients with mastocytosis experience anaphylactic reactions. OBJECTIVE: We sought to identify disease-specific biomarkers in plasma that could be used to predict patients with mastocytosis with increased risk of anaphylaxis. METHODS: Nineteen patients (≥18 years) and 2 control groups (11 subjects with allergic asthma and 13 healthy volunteers without history of atopy) were recruited. In total, 248 plasma proteins were analyzed by Proximity Extension Assay using Olink Proseek Multiplex panels. RESULTS: We identified 4 novel proteins, in addition to tryptase, E-selectin, adrenomedullin, T-cell immunoglobulin, and mucin domain 1, and CUB domain-containing protein 1/CD138 to be significantly increased in patients with mastocytosis compared with both patients with asthma and healthy controls. Furthermore, we investigated whether we could discriminate between patients with mastocytosis with or without anaphylaxis. In addition to tryptase, we identified 3 novel proteins, that is, allergin-1, pregnancy-associated plasma protein-A, and galectin-3, with significantly different levels in patients with mastocytosis with anaphylaxis compared with those without anaphylaxis. CONCLUSIONS: Newly identified proteomic biomarkers may be used to predict patients with mastocytosis with increased risk of anaphylaxis.

Regulation of mast cell survival and apoptosis.

One key characteristic of certain mast cell populations is their longevity. Mast cell survival can also be promoted by Fc-receptor activation. Regulation of cell survival and apoptosis is regulated by the Bcl-2 family that consists of pro- and anti-apoptotic proteins. Depending on their relative cellular expression levels, the cells are either rescued or destined for apoptosis. To determine the regulation of mast cell survival and apoptosis, the expression of different Bcl-2 protein family members can be measured by western blot. The amount of viable versus apoptotic cells is decided by AnnexinV/propidium iodide staining, and cell lysates are prepared for western blot analysis from the appropriated time points.

Differentiation of mast cell subpopulations from mouse embryonic stem cells.

Mast cells can generally be divided into two major groups, connective tissue mast cells and mucosal mast cells. We and others have previously shown that these mast cell populations can be developed in vitro from mouse bone marrow stem cells using a combination of specific growth factors and cytokines. Mast cell differentiation from mouse embryonic stem (ES) cells is an important alternative method when developing mast cells from an embryonic lethal genetic deficiency or to reduce the use and handling of experimental animals. In this study, we have used protocols prior known to induce connective tissue like mast cells (CTLMC) (SCF and IL-4) and mucosal like mast cells (MLMC) (SCF, IL-3, IL-9 and TGF-ß) from mouse bone marrow progenitor cells and employed these protocols to study if phenotype specific mast cells can be developed from ES cells. We here demonstrate that mast cells of the different phenotypes, CTLMC and MLMC, can be derived from mouse ES cells. The mast cell populations were characterized by chymase expression, receptor expression and their difference in activation pattern and in activation-induced survival.