 PNEUMOSTEM consists of ex vivo cultured allogeneic, unrelated, human umbilical cord blood-derived mesenchymal stem cells hUCB-MSCs and it is intended for use as a cellular therapy product for prevention of Bronchopulmonary Dysplasia BPD. This study is an open-label, single-center, dose escalation study to evaluate of safety and efficacy of PNEUMOSTEM in premature infants at high risk for BPD. 