Figure 4.

Intratracheal bone marrow–derived mesenchymal stem cell (MSC) administration on Postnatal Day 4 improves lung structure. O₂-exposed lungs display the characteristic features of alveolar simplification that are unchanged with pulmonary artery smooth muscle cells (PASMCs). Conversely, lungs treated with intratracheal bone marrow–derived mesenchymal stem cells (BMSCs) have smaller and more numerous alveoli. Quantification of alveolar structures, using the mean linear intercept (Lm), confirms improved alveolarization in MSC-treated animals as compared with the other O₂-exposed groups.