Posttransplantation lung ischemia–reperfusion (IR) injuries affect both patient survival
and graft function. In this study, we evaluated the protective effects of infused human
multilineage-differentiating stress-enduring (Muse) cells, a novel, easily harvested type
of nontumorigenic endogenous reparative stem cell, against acute IR lung injury in a rat
model. After a 2-h warm IR injury induction in a left rat lung, human Muse cells, human
mesenchymal stem cells (MSCs), and vehicle were injected via the left pulmonary artery
after reperfusion. Functionality, histological findings, and protein expression were
subsequently assessed in the injured lung. In vitro, we also compared human Muse cells
with human MSCs in terms of migration abilities and the secretory properties of protective
substances. The arterial oxygen partial pressure to fractional inspired oxygen ratio,
alveolar-arterial oxygen gradient, left lung compliance, and histological injury score on
hematoxylin–eosin sections were significantly better in the Muse group relative to the MSC
and vehicle groups. Compared to MSCs, human Muse cells homed more efficiently to the
injured lung, where they suppressed the apoptosis and stimulated proliferation of host
alveolar cells. Human Muse cells also migrated to serum from lung-injured model rats and
produced beneficial substances (keratinocyte growth factor [KGF], hepatocyte growth
factor, angiopoietin-1, and prostaglandin E2) in vitro. Western blot of lung tissue
confirmed high expression of KGF and their target molecules (interleukin-6, protein kinase
B, and B-cell lymphoma-2) in the Muse group. Thus, Muse cells efficiently ameliorated lung
IR injury via pleiotropic effects in a rat model. These findings support further
investigation on the use of human Muse cells for lung IR injury.