Intratracheal administration of umbilical cord-derived mesenchymal stem cells attenuates hyperoxia-induced multi-organ injury via heme oxygenase-1 and JAK/STAT pathways

BACKGROUND Bronchopulmonary dysplasia(BPD)is not merely a chronic lung disease,but a systemic condition with multiple organs implications predominantly associated with hyperoxia exposure.Despite advances in current management strategies,limited progress has been made in reducing the BPD-related systemic damage.Meanwhile,although the protective effects of human umbilical cord-derived mesenchymal stem cells(hUC-MSCs)or their exosomes on hyperoxia-induced lung injury have been explored by many researchers,the underlying mechanism has not been addressed in detail,and few studies have focused on the therapeutic effect on systemic multiple organ injury.AIM To investigate whether hUC-MSC intratracheal administration could attenuate hyperoxia-induced lung,heart,and kidney injuries and the underlying regulatory mechanisms.METHODS Neonatal rats were exposed to hyperoxia(80%O_(2)),treated with hUC-MSCs intratracheal(iT)or intraperitoneal(iP)on postnatal day 7,and harvested on postnatal day 21.The tissue sections of the lung,heart,and kidney were analyzed morphometrically.Protein contents of the bronchoalveolar lavage fluid(BALF),myeloper oxidase(MPO)expression,and malondialdehyde(MDA)levels were examined.Pulmonary inflammatory cytokines were measured via enzyme-linked immunosorbent assay.A comparative transcriptomic analysis of differentially expressed genes(DEGs)in lung tissue was conducted via RNA-sequencing.Subsequently,we performed reverse transcription-quantitative polymerase chain reaction and western blot analysis to explore the expression of target mRNA and proteins related to inflammatory and oxidative responses.RESULTS iT hUC-MSCs administration improved pulmonary alveolarization and angiogenesis(P<0.01,P<0.01,P<0.001,and P<0.05 for mean linear intercept,septal counts,vascular medial thickness index,and microvessel density respectively).Meanwhile,treatment with hUC-MSCs iT ameliorated right ventricular hypertrophy(for Fulton’s index,P<0.01),and relieved reduced nephrogenic zone width(P<0.01)and glomerular diameter(P<0.001)in kidneys.Among the beneficial effects,a reduction of BALF protein,MPO,and MDA was observed in hUC-MSCs groups(P<0.01,P<0.001,and P<0.05 respectively).Increased pro-inflammatory cytokines tumor necrosis factor-alpha,interleukin(IL)-1β,and IL-6 expression observed in the hyperoxia group were significantly attenuated by hUC-MSCs administration(P<0.01,P<0.001,and P<0.05 respectively).In addition,we observed an increase in anti-inflammatory cytokine IL-10 expression in rats that received hUC-MSCs iT compared with rats reared in hyperoxia(P<0.05).Transcriptomic analysis showed that the DEGs in lung tissues induced by hyperoxia were enriched in pathways related to inflammatory responses,epithelial cell proliferation,and vasculature development.hUC-MSCs administration blunted these hyperoxia-induced dysregulated genes and resulted in a shift in the gene expression pattern toward the normoxia group.hUC-MSCs increased heme oxygenase-1(HO-1),JAK2,and STAT3 expression,and their phosphorylation in the lung,heart,and kidney(P<0.05).Remarkably,no significant difference was observed between the iT and iP administration.CONCLUSION iT hUC-MSCs administration ameliorates hyperoxia-induced lung,heart,and kidney injuries by activating HO-1 expression and JAK/STAT signaling.The therapeutic benefits of local iT and iP administration are equivalent.

Synergistic Effect of Alloying Atoms on Intrinsic Stacking-Fault Energy in Austenitic Steels

Intrinsic stacking-fault energy is a critical parameter influencing the various mechanical performances of aus- tenitic steels with high Mn concentrations. However, quantitative calculations of the stacking-fault energy （SFE） of the face-centered cubic （fcc） Fe, including the changes in concentrations and geometrical distribution of alloying atoms, cannot be obtained by using previous computation models. On the basis of the interaction energy model, we evaluated the effects of a single alloying atom （i.e., Mn, A1, Si, C and N）, as well as its aggregates, including the Mn-X dimer and Mn2-X trimer （X = A1, Si, C and N） on the SFE of the fcc Fe via first-principle calculations. Given low concentrations （〈10 wt%） of alloying atoms, dimers and trimers, theoretical calculations reveal the following： （1） Alloying atom Mn causes a decrease in the SFE, whereas A1, Si, C and N significantly increase the SFE; （2） combination with other alloying atoms to form the Mn-X dimer （X = A1, Si, C and N） exerts an effect on SFE that, to a certain extent, is close to that of the corresponding single X atom; （3） the interaction between Mnz-X and the stacking fault is stronger than that of the corresponding single X atom, inducing a significant increase in the SFE of fcc Fe. The theoretical results we obtained demonstrate that the increase in SFE in high-Mn steel originates from the synergistic effect of Mn and other trace alloy atoms.

Application of the Peierls–Nabarro Model to Symmetric Tilt Low-Angle Grain Boundary with Full Dislocation in Pure Magnesium

Three types of symmetric （1120） tilt low-angle grain boundaries （LAGBs） with array of basal, prismatic, and pyramidal edge full 〈a〉 dislocations in pure Mg have been studied by using the improved Peierls-Nabarro model in combination with the generalized stacking fault energy curve. The results show that with decreasing distance between the dislocations in all the three types of tilt LAGBs, the stress and strain fields are gradually suppressed. The reduction extent of the stress and strain fields decreases from the prismatic to basal to pyramidal dislocations. The variation of dislocation line energy （DLE） for all tilt LAGBs is divided into three stages： DLE changes slightly and linearly when the distance is larger than 300 A, - 10%; DLE declines exponentially and quickly when the distance goes from 300 to 100 A, ,- 70%; and finally, the descent speed lowers when the distance is smaller than 100 A and the dislocation core energy is nearly half of the DLE. The grain boundary energy （GBE） decreases when the tilt angle of LAGB increases from1 ° to 2° for all cases. The tilt LAGB consists of pyramidal dislocations always has the largest GBE, while that with array of prismatic dislo- cations has the smallest one in the whole range. The Peierls stress of dislocation in tilt LAGB is nearly unchanged, the same as that of single dislocation. This work is useful for further study of dissociated dislocation, solute segregation, precipitate nucleation in tilt LAGB and its interaction with single dislocations.