CD34 and bronchopulmonary dysplasia: As higher number of circulating CD34+ hematopoietic stem and progenitor cells have been reported in extremely preterm neonates compared to the full-term neonates [18], we chose to isolate MSCs from 25 and 30 wks GA UC to see whether CM or EXO from earlier GA MSCs demonstrate therapeutic effects on BPD pathology.