MSC-derived cytokines repair radiation-induced intra-villi microvascular injury

Microvascular injury initiates the pathogenesis of radiation enteropathy. As previously demonstrated, the secretome from mesenchymal stem cells contains various angiogenic cytokines that exhibited therapeutic potential for ischemic lesions. As such, the present study aimed to investigate whether cytokines derived from mesenchymal stem cells can repair endothelial injuries from irradiated intestine. Here, serum-free medium was conditioned by human adipose-derived mesenchymal stem cells, and we found that there were several angiogenic cytokines in the medium, including IL-8, angiogenin, HGF and VEGF. This medium promoted the formation of tubules between human umbilical cord vein endothelial cells and protected these cells against radiation-induced apoptosis in vitro. Likewise, our in vivo results revealed that repeated injections of mesenchymal stem cell-conditioned medium could accelerate the recovery of irradiated mice by reducing the serum levels of pro-inflammatory cytokines, including IL-1α, IL-6 and TNF-α, and promoting intra-villi angiogenesis. Herein, intervention by conditioned medium could increase the number of circulating endothelial progenitors, whereas neutralizing SDF-1α and/or inhibiting PI3K would hamper the recruitment of endothelial progenitors to the injured sites. Such results suggested that SDF-1α and PI3K-mediated phosphorylation were required for intra-villi angiogenesis. To illustrate this, we found that conditioned medium enabled endothelial cells to increase intracellular levels of phosphorylated Akt Ser473, both under irradiated and steady state conditions, and to up-regulate the expression of the CXCR4 and CXCR7 genes. Collectively, the present results revealed the therapeutic effects of mesenchymal stem cell-derived cytokines on microvascular injury of irradiated intestine.

A new cell culture system for infection with hepatitis B virus that fuses HepG2 cells with primary human hepatocytes

Hepatitis B virus (HBV) infection exhibits a very narrow host range and shows a strong tropism for liver parenchymal cells, however none of the previously established experimental models can reproduce the natural process of HBV infection. In the present study, primary human hepatocytes were fused with HepG2 cells to establish the hybrid HepCHLine-4 cell line with high susceptibility to HBV. The HepCHLine-4 cells expressed HBV-specific antigen when co-incubated with HBV-positive serum from a hepatitis B patient. Post-infection, HBV relaxed circular DNA and covalently closed circular DNA were detected in HepCHLine-4 cells using a nested polymerase chain reaction, and HBV-specific particles were visualized by electron microscopy of the culture media of HepCHLine-4 cells. HepG2 cells were not susceptible to HBV infection under the same conditions. The HepCHLine-4 cells can be sub-cultured for > 12 months while maintaining susceptibility to HBV and may, therefore, be useful for studying HBV infection and the viral life cycle in human hepatocytes.

Gut commensal bacteria, Paneth cells and their relations to radiation enteropathy

In steady state, the intestinal epithelium forms an important part of the gut barrier to defend against luminal bacterial attack. However, the intestinal epithelium is compromised by ionizing irradiation due to its inherent self-renewing capacity. In this process, small intestinal bacterial overgrowth is a critical event that reciprocally alters the immune milieu. In other words, intestinal bacterial dysbiosis induces inflammation in response to intestinal injuries, thus influencing the repair process of irradiated lesions. In fact, it is accepted that commensal bacteria can generally enhance the host radiation sensitivity. To address the determination of radiation sensitivity, we hypothesize that Paneth cells press a critical “button” because these cells are central to intestinal health and disease by using their peptides, which are responsible for controlling stem cell development in the small intestine and luminal bacterial diversity. Herein, the most important question is whether Paneth cells alter their secretion profiles in the situation of ionizing irradiation. On this basis, the tolerance of Paneth cells to ionizing radiation and related mechanisms by which radiation affects Paneth cell survival and death will be discussed in this review. We hope that the relevant results will be helpful in developing new approaches against radiation enteropathy.

Comparative sequence and expression analysis of tapetum specific male sterility related genes in Medicago truncatula

Heterosis, or enhancement through outbreeding, is one of the most promising approaches for increasing crop yield. Male sterility (MS), which promotes heterosis, has been widely applied in hybrid crop production. Medicago truncatula is a model legume species and is closely related to M. sativa, an important legume forage plant. Although the molecular mechanisms of MS in M. truncatula and M. sativa remain unclear, several studies of MS have been conducted in Arabidopsis thaliana. Previous research has shown that MS is associated with the destruction of tapetal cell layers. Disruption of tapetum developmental processes may result in pollen abortion. In an effort to identify genes useful for breeding in M. sativa, we identified MS related genes in M. truncatula using BLAST and homology to A. thaliana genes. In this study, we identified 63 tapetum specific male sterility (TSMS) related genes. The length of TSMS genes varied from 225 to 3747 bp. We identified 15 conserved domains and 8 cis-elements associated with TSMS related genes. Analysis of the phylogenetic relationships among these genes allowed them to be classified into three groups, MtTsms A, MtTsms B, and MtTsms C. Expression analyses revealed that these genes may be involved in developmental processes and response to abiotic stress.