Transfer of mitochondria between COPD airway smooth muscle cells

Background: Transfer of mitochondria from stem cells to airway smooth muscle cells (ASMCs) can attenuate oxidative stress-induced mitochondrial dysfunction. It is not known whether ASMCs can also exchange mitochondria, or what role this process may play in health and in disease. Aims: To quantify and assess the functional impact of mitochondrial transfer between ASMCs from ex-smoker and COPD subjects. Methods: MitoTracker-stained cells were co-cultured with CellTrace-stained cells. Transfer of mitochondria was quantified by flow cytometry and visualised using fluorescence microscopy. Fluorescence activated cell sorting (FACS) was used to separate cells that received exogenous mitochondria from cells that did not. These were plated for assessment of i) mitochondrial respiration using the Seahorse CellMitoStress Test; ii) mitochondrial ROS (mtROS) and mitochondrial membrane potential (Δψm) using MitoSOX and TMRM dyes, respectively; iii) proliferation using a BrdU incorporation assay and iv) gene expression and mitochondrial DNA (mtDNA) copy number using qPCR. Results: Transfer of mitochondria occurred between ASMCs from both ex-smoker and COPD subjects. ASMCs that received exogenous mitochondria showed increased mitochondrial respiration (1.5 fold, p Conclusions: Transfer of mitochondria occurs between ASMCs and regulates mitochondrial and cellular function, suggesting it may be an important homeostatic mechanism in the airways.