Species-specific regulation of fibrinogen synthesis with implications for porcine hepatocyte xenotransplantation

Systemic low-grade inflammation and depressive symptomology at chronic phase of ischemic stroke: The chain mediating role of fibrinogen and neutrophil counts

BACKGROUND

Post-stroke depression (PSD) is the most common psychological consequence of stroke. Increased inflammatory markers resulting from ischemic stroke may played an important role in the pathogenesis of depressive symptomology. The present study was conducted to further elucidate the relationship between stroke severity, systemic low-grade inflammation and chronic phase post-stroke depressive symptomology (CP-PSDS).

METHODS

A total of 897 stroke patients were consecutively recruited in this multicenter prospective cohort study and followed up for 1 year. The analytical sample consisted of 436 patients with ischemic stroke (23.4% female, median age = 57 years) from this cohort. Serum concentrations of inflammatory markers were measured in all 436 patients with ischemic stroke, from fasting morning venous blood samples on admission. Stroke severity was evaluated using the National Institutes of Health Stroke Scale (NIHSS) on admission and post-stroke depressive symptomology (PSDS) was evaluated by 17-item Hamilton Rating Scale for Depression (HRSD).

RESULTS

In the fully adjusted models, we observed that 1) NIHSS (Model 2: β = 0.200, 95%CI, 0.057 ∼ 0.332), fibrinogen (Model 2: β = 0.828, 95%CI, 0.269 ∼ 1.435), white blood cell counts (WBC, model 2: β = 0.354, 95%CI, 0.122 ∼ 0.577) and neutrophil counts (Model 2: β = 0.401, 95%CI, 0.126 ∼ 0.655) can independently predict the CP-PSDS after ischemic stroke onset; 2) fibrinogen (Indirect effect = 0.027, 95%CI, 0.007 ∼ 0.063, 13.4% mediated), WBC (Indirect effect = 0.024, 95%CI, 0.005 ∼ 0.058, 11.8% mediated) and neutrophil counts (Indirect effect = 0.030, 95%CI, 0.006 ∼ 0.069, 14.8% mediated) could partially mediate the association between stroke severity and CP-PSDS, and 3) stroke severity might cause CP-PSDS partly through the chain-mediating role of both fibrinogen and neutrophil counts (chain mediated effect = 0.003, 95%CI, 0.000 ∼ 0.011, p = 0.025, 1.6% mediated).

CONCLUSIONS

Findings revealed that fibrinogen, WBC and neutrophil counts may be independent predictors of CP-PSDS and partial mediators of the relationship between stroke severity and CP-PSDS among patients with ischemic stroke. In addition, the chain mediating effect of fibrinogen and neutrophil counts might play an important role in the occurrence of CP-PSDS. However, no inflammatory markers were associated with CP-PSDS in females.

The resurgent landscape of xenotransplantation of pig organs in nonhuman primates

Organ shortage is a major bottleneck in allotransplantation and causes many wait-listed patients to die or become too sick for transplantation. Genetically engineered pigs have been discussed as a potential alternative to allogeneic donor organs. Although xenotransplantation of pig-derived organs in nonhuman primates (NHPs) has shown sequential advances in recent years, there are still underlying problems that need to be completely addressed before clinical applications, including (i) acute humoral xenograft rejection; (ii) acute cellular rejection; (iii) dysregulation of coagulation and inflammation; (iv) physiological incompatibility; and (v) cross-species infection. Moreover, various genetic modifications to the pig donor need to be fully characterized, with the aim of identifying the ideal transgene combination for upcoming clinical trials. In addition, suitable pretransplant screening methods need to be confirmed for optimal donor-recipient matching, ensuring a good outcome from xenotransplantation. Herein, we summarize the understanding of organ xenotransplantation in pigs-to-NHPs and highlight the current status and recent progress in extending the survival time of pig xenografts and recipients. We also discuss practical strategies for overcoming the obstacles to xenotransplantation mentioned above to further advance transplantation of pig organs in the clinic.

Bioengineering considerations in liver regenerative medicine

Background

Liver disease contributes significantly to global disease burden and is associated with rising incidence and escalating costs. It is likely that innovative approaches, arising from the emerging field of liver regenerative medicine, will counter these trends.

Main body

Liver regenerative medicine is a rapidly expanding field based on a rich history of basic investigations into the nature of liver structure, physiology, development, regeneration, and function. With a bioengineering perspective, we discuss all major subfields within liver regenerative medicine, focusing on the history, seminal publications, recent progress within these fields, and commercialization efforts. The areas reviewed include fundamental aspects of liver transplantation, liver regeneration, primary hepatocyte cell culture, bioartificial liver, hepatocyte transplantation and liver cell therapies, mouse liver repopulation, adult liver stem cell/progenitor cells, pluripotent stem cells, hepatic microdevices, and decellularized liver grafts.

Conclusion

These studies highlight the creative directions of liver regenerative medicine, the collective efforts of scientists, engineers, and doctors, and the bright outlook for a wide range of approaches and applications which will impact patients with liver disease.

Contribution of polymeric materials to progress in xenotransplantation of microencapsulated cells: a review

Cell microencapsulation and subsequent transplantation of the microencapsulated cells require multidisciplinary approaches. Physical, chemical, biological, engineering, and medical expertise has to be combined. Several natural and synthetic polymeric materials and different technologies have been reported for the preparation of hydrogels, which are suitable to protect cells by microencapsulation. However, owing to the frequent lack of adequate characterization of the hydrogels and their components as well as incomplete description of the technology, many results of in vitro and in vivo studies appear contradictory or cannot reliably be reproduced. This review addresses the state of the art in cell microencapsulation with special focus on microencapsulated cells intended for xenotransplantation cell therapies. The choice of materials, the design and fabrication of the microspheres, as well as the conditions to be met during the cell microencapsulation process, are summarized and discussed prior to presenting research results of in vitro and in vivo studies. Overall, this review will serve to sensitize medically educated specialists for materials and technological aspects of cell microencapsulation.

Current status of hepatocyte xenotransplantation

The treatment of acute liver failure, a condition with high mortality, comprises optimal clinical care, and in severe cases liver transplantation. However, there are limitations in availability of organ donors. Hepatocyte transplantation is a promising alternative that could fill the medical need, in particular as the bridge to liver transplantation. Encapsulated porcine hepatocytes represent an unlimited source that could function as a bioreactor requiring minimal immunosuppression. Besides patients with acute liver failure, patients with alcoholic hepatitis who are unresponsive to a short course of corticosteroids are a target for hepatocyte transplantation. In this review we present an overview of the innate immune barriers in hepatocyte xenotransplantation, including the role of complement and natural antibodies; the role of phagocytic cells and ligands like CD47 in the regulation of phagocytic cells; and the role of Natural Killer cells. We present also some illustrations of physiological species incompatibilities in hepatocyte xenotransplantation, such as incompatibilities in the coagulation system. An overview of the methodology for cell microencapsulation is presented, followed by proof-of-concept studies in rodent and nonhuman primate models of fulminant liver failure: these studies document the efficacy of microencapsulated porcine hepatocytes which warrants progress towards clinical application. Lastly, we present an outline of a provisional clinical trial, that upon completion of preclinical work could start within the upcoming 2-3 years.

Regulation of alpha-1 acid glycoprotein synthesis by porcine hepatocytes in monolayer culture

Alpha-1 acid glycoprotein (AGP, orosomucoid, ORM-1) is a highly glycosylated mammalian acute-phase protein, which is synthesized primarily in the liver and represents the major serum protein in newborn pigs. Recent data have suggested that the pig is unique in that AGP is a negative acute-phase protein in this species, and its circulating concentration appears to be associated with growth rate. The purpose of the present study was to investigate the regulation of AGP synthesis in hepatocytes prepared from suckling piglets and to provide a framework to compare its regulation with that of haptoglobin (HP), a positive acute-phase protein. Hepatocytes were isolated from preweaned piglets and maintained in serum-free monolayer culture for up to 72 h. The influences of hormones, cytokines, and redox modifiers on the expression and secretion of AGP and HP were determined by relative polymerase chain reaction and by measuring the concentration of each protein secreted into culture medium. The messenger RNA abundance and/or secretion of AGP protein was enhanced by interleukin (IL)-17a, IL-1, and resveratrol and inhibited by tumor necrosis factor-α (TNF), oncostatin M, and thyroid hormone (P < 0.05). HP expression and synthesis were upregulated by oncostatin M, IL-6, and dexamethasone and downregulated by TNF (P < 0.01). The overall messenger RNA expression at 24 h was in agreement with the secreted protein patterns confirming that control of these proteins in hepatocytes is largely transcriptional. Moreover, these data support the consideration that AGP is a negative acute-phase reactant and appears to be regulated by cytokines (with the exception of TNF) and hormones primarily in a manner opposite to that of the positive acute-phase protein, HP.