Rare Pulmonary Connective Tissue Type Mast Cells Regulate Lung Endothelial Cell Angiogenesis

Area of Science:

• Pulmonary Medicine
• Cell Biology
• Developmental Biology

Background:

• Mast cells are immune cells found in the lungs, with mucosal (MC_T) and connective tissue (MC_TC) phenotypes.
• MC_TCs accumulate in the lungs of infants with severe bronchopulmonary dysplasia (BPD), a chronic lung disease linked to preterm birth.
• BPD is characterized by pulmonary vascular dysmorphia, suggesting a role for MC_TCs in disease pathogenesis.

Purpose of the Study:

• To investigate the role of MC_TCs in vascular dysmorphia observed in BPD.
• To determine how MC_TCs affect endothelial cell function and angiogenesis.
• To explore the mechanistic role of MC_TC proteases in these processes.

Main Methods:

• Utilized the human mast cell line (LUVA) to model MC_TCs and MC_Ts.
• Assessed the impact of MC_TCs on vascular organization in mouse lung explant cultures.
• Studied the effects of MC_TCs on in vitro tube formation and barrier function of primary fetal human pulmonary microvascular endothelial cells.
• Tested the efficacy of protease inhibitors on MC_TC-induced changes in endothelial cell angiogenic activities.

Main Results:

• MC_TCs, but not MC_Ts, were associated with vascular dysmorphia in lung explants.
• MC_TCs potentiated interactions with, inhibited tube stability of, and disrupted junctions in fetal pulmonary microvascular endothelial cells in vitro.
• Protease inhibitors partially reversed the detrimental effects of MC_TCs on endothelial cell angiogenic activities ex vivo and in vitro.

Conclusions:

• MC_TCs may directly contribute to the disrupted angiogenesis seen in bronchopulmonary dysplasia.
• MC_TC proteases play a significant role in mediating the adverse effects on vascular development.
• Further research into mast cell subtype regulation and effector functions is crucial for understanding and treating BPD.