This study is an open-label, single-center, dose escalation study to evaluate of safety and efficacy of human umbilical cord -derived mesenchymal stem cells (hUC-MSCs) in children with moderate and severe bronchopulmonary dysplasia.

Bronchopulmonary dysplasia (BPD) is one of the most common chronic lung diseases with poor prognosis, especially in preterm infants with moderate and severe BPD. However, there is lack of effective therapies for this disease.

hUC-MSCs are widely used in clinic due to their low immunogenicity and convenient to get.Many animal study had shown that hUC-MSCs had therapeutic effects on a variety of animal models of lung disease.Furthermore,there are a large number of clinical trials of MSCs applied to various system diseases and the safety was verified.So,the main purpose of this study is to evaluate the safety and efficacy of hUC-MSCs in participants with moderate and severe bronchopulmonary dysplasia.

Inclusion Criteria:

1. Participants with moderate and severe bronchopulmonary dysplasia are not well treated by routine therapy
2. The legal representative or the participant had signed consent.

Exclusion Criteria:

• 1. Severe underlying diseases (e.g. systemic and hematological malignancies, heart failure, liver and kidney failure, immune deficiency, severe infectious diseases, III-IV grade pulmonary hypertension, Lung transplantation, current indications of acute surgery after lung transplantation) 2. Participants whose age is more than 1 year old.