We previously demonstrated the safety and feasibility of mesenchymal stem cell (MSC) transplantation for bronchopulmonary dysplasia (BPD) in preterm infants in a phase I clinical trial. We thus investigated the therapeutic efficacy of MSCs for BPD in premature infants. A phase II double-blind, randomized, placebo-controlled clinical trial was conducted on preterm infants at 23 to 28 gestational weeks (GW) receiving mechanical ventilator support with respiratory deterioration between postnatal days 5 and 14. Infants were stratified by 23 to 24 GW and 25 to 28 GW and randomly allocated (1:1) to receive stem cells (1 × 10 7 cells/kg, n = 33) or placebo (n = 33). Although the inflammatory cytokines in the tracheal aspirate fluid were significantly reduced with MSCs, the primary outcome of death or severe/moderate BPD in the control group (18/33, 55%) was not significantly improved with MSC transplantation (17/33, 52%). In the subgroup analysis, the secondary outcome of severe BPD was significantly improved from 53% (8/15) to 19% (3/16) with MSC transplantation in the 23 to 24 GW group but not in the 25 to 28 GW subgroup. In summary, although MSC transplantation might be safe and feasible, this small study was underpowered to detect its therapeutic efficacy in preterm infants at 23 to 28 GW. Accordingly, we are now conducting an additional larger and controlled phase II clinical trial focusing on infants at 23 to 24 GW (NCT03392467). ClinicalTrials.gov identifier: NCT01828957.

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Autosomal recessive polycystic kidney disease is among the most common inherited ciliopathies and is caused by mutations in the polycystic kidney and hepatic disease 1 (PKHD1) gene. Despite its great phenotypic variability, this condition is usually diagnosed during the neonatal and early infantile periods. We report a 37 +3-gestational-week neonate presenting with fatal autosomal recessive polycystic kidney disease who died at 28 hours of life from severe respiratory failure. The familial history is significant because a previous sibling died in utero at 24 +2 weeks of gestational age and was diagnosed with polycystic kidney disease based on prenatal ultrasonography and autopsy. Our patient's autopsy revealed findings compatible with polycystic kidney disease. In addition, a PKHD1 gene study of peripheral blood leukocytes identified the compound heterozygote mutation c.274C>T(p.Arg92Trp), as well as the novel heterozygous nonsense mutation c.2770C>T(p.Gln924*).