| Lung transplantation is a surgical procedure in which a patient’s diseased lungs are partially or totally replaced by lungs from another donor. It is the therapeutic measure of last resort for patients with end-stage lung disease who have exhausted all other available treatments without improvement. Many conditions could make such surgery necessary. The most common reasons for lung transplantation were: idiopathic pulmonary fibrosis; chronic obstructive pulmonary disease (COPD), including emphysema; alpha1-antitrypsin deficiency; cystic fibrosis; idiopathic pulmonary hypertension; replacing previously transplanted lungs that have failed; and other causes, including bronchiectasis and sarcoidosis. However, the relatively shortage donor pool limit a wider application of this therapy.Xenotransplantation can give a solution to the donor shortage that is currently the major barrier to solid-organ transplantation including xeno-lung transplantation. During the past years, many advances have been made to address the major initial immunological obstacle to "discordant" pig-to-human solid organ transplantation: hyperacute rejection (HAR). As organs from unmodified pigs were evaluated in animal models, HAR was found to be primarily a consequence of the recipient’s preformed anti-pig antibodies binding on porcine vascular endothelial cells leading to subsequent complement activation, thrombosis and graft failure. This process occurs within minutes to hours of human blood perfusion in porcine organs. Since the carbohydrate structure Galactose(α1,3-Galactose, Gal) is recognized by over80%of anti-pig antibodies found in man. The ability to breed pigs with multiple genetic modifications provides a unique opportunity to explore the immunologic challenges of pulmonary xenotransplantation.Our research group has established GalTKO.hCD46.hTM transgenic pig model, which on the basis of genetically modified galactosyl transferase knock-out pigs(GalTKO pigs). Endothelium and parenchymal cells from GalTKO.hCD46.hTM animals lack the Gal al,3-Gal epitope, express human CD46, a complement regulatory protein and human thrombomodulin (hTM). The differential effects of these interventions on lung physiological parameters, platelet and coagulation activation were summarized.Physiologic, hematologic and biochemical parameters during perfusion with heparinized fresh human blood were measured for14GalTKO.hCD46.hTM, GalTKO (n=16), and wild type pig lungs (n=16), and12pig lungs perfused with autologous pig blood. Median GalTKO.hCD46lung survival was175minutes compared to120for GalTKO (p=0.24) and10for wild type lungs (p<0.001). Complement activation, platelet activation, and histamine elaboration were reduced during the perfusion in GalTKO.hCD46.hTM lungs compared to GalTKO (△C3a at240’:238±22VS572±162, p=0.03;△CD62P at240’:11.9±6VS25.4±7.4, p=0.03). Thrombomodulin was detected in lung tissues through the whole perfusion process by immunohistochemistry. We consider that beside the significant down-regulation of complement activation, hCD46and hTM expression in GalTKO lungs diminished platelet and coagulation cascade activation and neutrophil sequestration. Because GalTKO.hCD46.hTM lung failure kinetics correlated directly with platelet and neutrophil sequestration, coagulation cascade activation.In vitro results showed that endothelial cells from GalTKO.hCD46.hTM transgenic pigs expressed high level of hCD46and thrombomodulin. Compared to GalTKO endothelia, hTM expression increased aPC elaboration14fold (5.5vs HUVEC) decreased thrombus volume by84%(P=0.0001), by reducing adhesion and aggregation58%and65%(P<0.001each). The thrombomodulin can effectively help thrombin to activate protein C, and significantly inhibited thrombosis in the bio-flux cell infusion process.In conclusion, The ability to breed pigs with multiple genetic modifications, and to evaluate lung physiology and histology in real-time on an ex vivo rig, represent significant advances toward better understanding the challenges inherent to pulmonary xenotransplantation. Our further progress will likely depend upon improved control of lung physiological parameters, platelet and coagulation activation pathways, by rationally targeted additional modifications to pigs and pharmacologic interventions. Researchers have proved the content and composition of polyunsaturated fatty acids affected the differentiation, proliferation and apoptosis of tumor cells.n-3polyunsaturated fatty acids are considered to play an important role in cell differentiation and function, it can lower the blood pressure, relax the vessels, inhibit the allergic and inflammatory reactions, can also act as a tumor suppressor and prevent cardiovascular disease, but the molecular mechanism is not yet clear.Recently, a new class of RNA regulatory genes known as microRNAs (miRNAs) has been found to introduce a whole new layer of gene regulation in eukaryotes. miRNAs are endogenous non-coding RNAs, consisting of19to23nucleotides in length. They play an important role in regulating gene expression by base-pairing to the complementary sites on the target mRNAs, thus blocking the translation or triggering the degradation of the target mRNAs. Since the discovery of the first miRNA (lin-4) in C. elegans, thousands of miRNAs have been identified experimentally or computationally from a variety of species. miRNAs are currently estimated to comprise1-5%of animal genes and collectively regulate up to30%of genes, making them one of the most abundant classes of regulators.Dysregulated expression of microRNAs (miRNAs) in various tissues has been associated with a variety of diseases, such as cancers and diabetes. miRNAs in serum are stable, reproducible, and consistent among individuals of the same species, served as potential biomarkers for the detection of various cancers and other diseases. We have previously developed a transgenic mouse model that expresses a gene, encoding an n-3fatty acid desaturase, which converts n-6fatty acids to n-3fatty acids. Employing Solexa, we analyzed all serum miRNAs in WT and mfat-1mice. By quantitative RT-PCR,12highly expressed miRNAs were identified in mfat-1mice. Pathway analysis of target genes regulated by these12miRNAs covered a significant number of genes involved in cancer development related pathways, including PI3K, MAPK, mTOR etc, which suggests the relationship between n-3PUFAs and cancer prevention. |
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