Fig. 5.

Sequence of events leading to mitochondrial transfer from alveolus-attached bone-marrow-derived stromal cells (BMSCs) to the alveolar epithelium. The sketch of the distal airway (left) shows the arrival of airway instilled BMSCs (MSC) in alveoli composed of alveolar type 1 and type 2 cells (AT2 and AT2, respectively) and alveolar macrophages (AM). Subsequent processes in the alveolus (right) are 1) BMSCs adhere to the alveolar epithelium through Cx43 interactions; 2) gap junctions form between BMSCs and the epithelium; 3) calcium levels increase in the BMSCs; and 4) BMSCs release mitochondria-containing microvesicles which enter the epithelium and release their mitochondria in the cytosol.