Use of Mesenchymal Stem Cells in Pre-term Patients With Bronchopulmonary Dysplasia.

Inclusion Criteria: * Alive newborns weighing ≤ 1250 grams and GA ≤ 28 weeks, who are on mechanical ventilation with a FiO2 ≥0.3 between days 5 and 14 of life, with no immediate extubation foreseeable. Exclusion Criteria: * Presence of another concomitant congenital pathology at the time of inclusion: pulmonary malformations with compromised pulmonary function, active pulmonary haemorrhage, severe pulmonary hypoplasia, renal malformations with systemic compromise, congenital heart disease, polymalformative syndromes, chromosomopathies. * Presence of refractory haemodynamic instability of any cause at the time of inclusion. * Presence of severe neurological damage at the time of inclusion (HIV grade III or higher). * Patients who have required major surgery in the 72 hours prior to inclusion. * Patients who have necrotising enterocolitis (NEC) grades ≥II at the time of inclusion, according to the Bell classification. * Patients who are children of a mother with HIV