Cryopreservation is a process that preserves organelles, cells, tissues, or any other biological constructs by cooling the samples to very low temperatures. The responses of living cells to ice formation are of theoretical interest and practical relevance. Stem cells and other viable tissues, which have great potential for use in basic research as well as for many medical applications, cannot be stored with simple cooling or freezing for a long time because ice crystal formation, osmotic shock, and membrane damage during freezing and thawing will cause cell death. The successful cryopreservation of cells and tissues has been gradually increasing in recent years, with the use of cryoprotective agents and temperature control equipment. Continuous understanding of the physical and chemical properties that occur in the freezing and thawing cycle will be necessary for the successful cryopreservation of cells or tissues and their clinical applications. In this review, we briefly address representative cryopreservation processes, such as slow freezing and vitrification, and the available cryoprotective agents. In addition, some adverse effects of cryopreservation are mentioned.

Background: Despite the potential importance of pulmonary artery hypertension (PAH) in preterm infants with bronchopulmonary dysplasia (BPD), little is known about the risk factors for PAH. Objectives: To investigate the risk factors for PAH in preterm infants with BPD. Methods: Infants diagnosed with BPD were assigned to the PAH group or non-PAH group except for infants with mild BPD who had no PAH. PAH was diagnosed on the basis of echocardiograms demonstrating elevated right ventricle pressure beyond the postnatal age of 2 months. Logistic regression analysis was done for the multivariate assessment of the risk factors for PAH in preterm infants with moderate or severe BPD. Results: A total of 98 infants among 145 infants with BPD were divided into a PAH group (n = 25) or non-PAH group (n = 73), while the remaining 47 infants had mild BPD with no PAH. Among the study patients, survival rate of the PAH group was significantly lower than that of the non-PAH group. Infants with PAH had more severe cases of BPD and underwent longer durations of oxygen therapy, conventional or high-frequency ventilation, and hospitalization compared to those without PAH. Low 5-min Apgar scores (≤6; relative risk (RR) 6.2; 95% confidence interval (CI) 1.4–28.0; p = 0.017) and oligohydramnios (RR 7.7; 95% CI 2.0–29.6; p = 0.030) were found to be significant risk factors for PAH according to multivariate analysis. Conclusions: The present study shows that oligohydramnios is a specific risk factor for PAH in preterm infants with moderate or severe BPD.

Neonatal hypoxic-ischemic brain injury (HIE) remains a major cause of neurologic disabilities. However, many experimental therapies have shown limited successes. We assessed whether human mesenchymal stem cells (MSCs) could be transplanted in the HIE rat brain to improve neurologic disabilities. P7 SD rats were either subjected to left carotid artery ligation and hypoxic exposure [hypoxia-ischemia (HI)] or sham operation and normoxic exposure (sham). On P10, rat pubs received either PKH26-labeled MSCs or buffer via intracardial injection, resulting in four experimental groups: sham-buffer, sham-MSC, HI-buffer, and HI-MSC. Cylinder test and accelerating rotarod test were performed 14, 20, 30, and 40 d after injection. Six weeks after injection, cresyl violet and double immunofluorescence staining were performed. MSCs were transplanted to the whole brain mainly after HI. Glial fibrillary acidic protein and OX42 were more abundantly colocalized with MSC than neuronal specific nuclear protein or myelin basic protein. There were no significant differences in the total amounts and cell types between the lesioned and nonlesioned hemisphere. The lesioned hemispheric volume was decreased after HI (p ϭ 0.012) but not restored by MSC. Neurologic performance was significantly impaired only on the cylinder test after HI (p ϭ 0.034), and MSC transplants improved it (p ϭ 0.010). These suggest MSC can be a candidate for the treatment of neonatal HIE. (Pediatr Res 67: 42-46, 2010) H ypoxic-ischemic brain injury (HIE), a result of asphyxia at term, remains a major cause of neurologic disabilities. It occurs in ϳ20 of 1000 full-term infants. Between 20 and 50% of asphyxiated babies who exhibit HIE die during the newborn period. Of the survivors, up to 25% have permanent neuropsychological handicaps in the form of cerebral palsy, with or without associated mental retardation, learning disability, or epilepsy (1). However, except hypothermia, which has shown improvement only in mild to moderate HIE, many experimental therapies have met with limited success in the clinical environment (2).Neural stem cells have been proposed as a useful treatment modality for the diseases of the CNS including neonatal HIE in animal models. However, their lack of accessibility and the inhomogeneity in neuronal differentiation of various neurospheres limit their utility (3,4). Mesenchymal stem cells (MSCs), as cell-based therapy offer a potential source of therapies for various rodent models and clinical trials of human diseases such as Parkinson's disease, Huntington's disease, myocardiac infarction, and stroke (5-9). However, limited data are available in neonatal HIE models. Guan et al. (10) reported that more MSCs were transplanted to the neonatal rat brain when MSCs were intraperitoneally injected 2 h after hypoxia-ischemia (HI) than when they were injected in the sham group. Yasuhara et al. reported that when they injected MSCs into the hippocampus of neonatal HI rats, MSC survived 14 d after post-transplantation and helped behavioral...

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