Figure 1.

Design of the study. (A) Clinical management of extremely premature-born, mechanically ventilated baboons. Abbreviations: FiO₂: fraction of inspired oxygen; HOL: hour of life; paO₂/paCO₂: partial pressures of oxygen/carbon dioxide in the arterial blood; PC-CMV: pressure-controlled continuous mandatory ventilation; PEEP: positive end-expiratory pressure; PICC: peripheral inserted central venous catheter; PIP: positive inspiratory pressure; UAC: umbilical arterial catheter. UC-MSC: umbilical cord tissue-derived mesenchymal stromal cells. Asterisks (*) indicate timepoints of echocardiographic studies. (B) Sequential deconstruction of lung tissue into unambiguously identifiable structures. Counting of lung-testsystem interactions (points: P and intersections: I) enabled quantification of absolute and relative volumes, surfaces and thicknesses unbiased by design. PBV: peribronchial/perivascular connective tissue. Analyses and acquisition of reference volumes was performed at magnifications of 10 × 10 (entire lung structure) or 40 × 10 (subanalysis of non-parenchymatous tissues). Black scale bars: 100µm, white scale bars: 25µm. Staining toluidine blue on Technovit 7100.