Lung transplantation in the fischer 344–wistar kyoto strain combination is a relevant experimental model to study the development of bronchiolitis obliterans in the rat

Ex vivo delivery of regulatory T cells for control of alloimmune priming in the donor lung

Survival after lung transplantation (LTx) is hampered by uncontrolled inflammation and alloimmunity. Regulatory T cells (Tregs) are being studied as a cellular therapy in solid organ transplantation. Whether these systemically administered Tregs can function at the appropriate location and time is an important concern. We hypothesized that in vitro expanded, recipient-derived Tregs can be delivered to donor lungs prior to LTx via ex vivo lung perfusion (EVLP), maintaining their immunomodulatory ability.In a rat model, Wistar Kyoto (WKy) CD4⁺CD25^high Tregs were expanded in vitro prior to EVLP. Expanded Tregs were administered to Fisher 344 (F344) donor lungs during EVLP; left lungs were transplanted into WKy recipients. Treg localisation and function post-transplant were assessed. In a proof-of-concept experiment, cryopreserved expanded human CD4⁺CD25⁺CD127^low Tregs were thawed and injected into discarded human lungs during EVLP.Rat Tregs entered the lung parenchyma and retained suppressive function. Expanded Tregs had no adverse effect on donor lung physiology during EVLP; lung water as measured by wet-to-dry weight ratio was reduced by Treg therapy. The administered cells remained in the graft at 3 days post-transplant where they reduced activation of intragraft effector CD4⁺ T cells; these effects were diminished by day 7. Human Tregs entered the lung parenchyma during EVLP where they expressed key immunoregulatory molecules (CTLA4⁺, 4-1BB⁺, CD39⁺, and CD15s⁺).Pre-transplant Treg administration can inhibit alloimmunity within the lung allograft at early time points post- transplant. Our organ-directed approach has potential for clinical translation.

Anti-oxidative effect of the tyrosine kinase inhibitor nintedanib: a potential therapy for chronic lung allograft dysfunction?

Background: The long-term survival after lung transplantation (LTx) is often limited by the development of chronic lung allograft dysfunction (CLAD). Increased oxidative stress has been found to occur in chronic lung allograft dysfunction because of several risk factors, e.g. immunological factors or drug related factors. The aim of this study was to investigate the anti-oxidative effect of the receptor tyrosine kinase (RTK) inhibitor nintedanib on immunologically induced oxidative stress and on drug induced oxidative stress.Methods: In-vivo studies were used for investigation of immunologically induced oxidative stress: Immunohistochemistry of transglutaminase-2 (TGM-2) was used to figure out a potential anti-oxidative effect of receptor tyrosine kinase inhibitor nintedanib in a rat model of allogeneic left LTx. In-vitro studies were used for investigation of drug induced oxidative stress: Cell viability assay, 2'7'-dichlorodihydrofluorescein diacetate (DCFDA) and immunofluorescence of transglutaminase-2 were disposed to examine the potential impact of nintedanib on cyclosporin A (CsA) treated lung fibroblasts of the rat.Results: In-vivo studies: Allogeneic transplanted animals without drug interaction showed severe chronic rejection and an excessive expression of TGM-2, whereas the application of nintedanib significantly decreased the number of TGM-2 positive cells. In-vitro studies: Concentrations of CsA ranging from 250 ng/ml to 500 ng/ml demonstrated oxidative stress caused by an increased production of reactive oxygen species (ROS) and an overexpression of TGM-2 without inducing apoptosis in cells. Concentrations of more than 1000 ng/ml led to a considerable decrease of cellularity. 30 min-pre-incubation with nintedanib at a concentration between 25 and 100 nM reduced generation of intracellular ROS and expression of TGM-2.Conclusion: These results demonstrate a downregulation of ROS and TGM-2 by pretreatment with the receptor tyrosine kinase inhibitor nintedanib and present its potential anti-oxidative and immunomodulatory effect in the treatment of chronic lung allograft dysfunction.

Diagnosis, Pathophysiology and Experimental Models of Chronic Lung Allograft Rejection

Chronic rejection is the Achilles heel of modern lung transplantation, characterized by a slow, progressive decline in allograft function. Clinically, this manifests as obstructive disease, restrictive disease, or a mixture of the 2 depending on the underlying pathology. The 2 major phenotypes of chronic rejection include bronchiolitis obliterans syndrome and restrictive allograft syndrome. The last decade of research has revealed that each of these phenotypes has a unique underlying pathophysiology which may require a distinct treatment regimen for optimal control. Insights into the intricate alloimmune pathways contributing to chronic rejection have been gained from both large and small animal models, suggesting directions for future research. In this review, we explore the pathological hallmarks of chronic rejection, recent insights gained from both clinical and basic science research, and the current state of animal models of chronic lung rejection.

The role of HIF-1α-VEGF pathway in bronchiolitis obliterans after lung transplantation

Background

Graft function may be affected if the organ is exposed to hypoxia. We hypothesized that bronchiolitis obliterans (BO) after lung transplantation is associated with hypoxia-inducible factor-1α (HIF-1α). This study compares the expression of HIF-1α and its downstream proteins in allograft and isograft to explore the relationship between this pathway and BO in rats.

Material and methods

We performed an orthotopic left pulmonary transplant model using the tri-cuff vascular anastomosis method and evaluated the histopathology, including the severity of fibrosis (SF). The expression of HIF-1α, VEGF-A, and VEGFR-2 was accessed by immunohistochemistry.

Results

The imageology and pathology showed that the allogenic model developed BO 90 days after the operation. The percentages of a high expression of HIF-1α, VEGF-A, and VEGFR-2 in the allogeneic group were 77.27, 63.64, and 68.18% higher than in the isogeneic group, respectively. The SF score was highest in the allograft and was positively correlated with the expression of the proteins.

Conclusion

This model can simulate human BO after lung transplantation. The expression of HIF-1α and its downstream proteins in post-transplantation was up-regulated, suggesting that activation of the HIF-1α-VEGF pathway might be involved in the occurrence and prognosis of BO.

The activity of nintedanib in an animal model of allogenic left lung transplantation resembling aspects of allograft rejection

AIM OF THE STUDY

The prevention and treatment of chronic lung allograft dysfunction (CLAD) after lung transplantation (LTx) remain unsatisfactory. Growth factors may play an important role in the development of CLAD. This study evaluated the effects of nintedanib, a receptor tyrosine kinase inhibitor, in the treatment of CLAD after experimental LTx.

MATERIALS AND METHODS

A rat model of left lung allo-transplantation (Fisher 344 to Wistar Kyoto) was used to evaluate the effect of nintedanib (50 mg/kg per day) on the development of CLAD. Therapy with nintedanib began 2 days before LTx and ended on postoperative day (POD) 20 (n = 6) or 60 (n = 6). Nontreated animals who underwent LTx (n = 12) were used as controls, whereas naïve lungs (n = 24) served as reference for physiological healthy organs without transplantation damage or medical effects. Acute and chronic rejection were evaluated on POD 20 and 60, respectively.

RESULTS

Immunohistologic analysis showed a decrease in growth factors/receptors on POD 60 (nintedanib-treated vs. nontreated controls: platelet-derived growth factor (PDGF) A: [P ≤ 0.001]; PDGF receptor-α: [P ≤ 0.001]; vascular endothelial growth factor (VEGF) A: [P ≤ 0.001]; VEGF receptor-2: [P ≤ 0.001]). However, no reductions in fibrotic changes were observed in nintedanib-treated allografts compared with nontreated allografts. Although nintedanib treatment started before LTx none of the animals showed impaired wound healing. No dehiscence of the sutures of the bronchus, vessels or skin, or stenosis of the bronchus was found.

CONCLUSION

In conclusion, while nintedanib reduced the expression of growth factors/receptors in a rat LTx model, a reduction in fibrotic alterations was not observed at POD 60.

Effects of azithromycin and tanomastat on experimental bronchiolitis obliterans

OBJECTIVE

Azithromycin has become a standard of care in therapy of bronchiolitis obliterans following lung transplantation. Matrix metalloprotease-9 broncho-alveolar lavage levels increase in airway neutrophilia and bronchiolitis obliterans. Interleukin-17 may play a role in lung allograft rejection, and interleukin-12 is downregulated in bronchiolitis obliterans. Whether these mechanisms can be targeted by azithromycin remains unclear.

METHODS

Bronchiolitis obliterans was induced by transplantation of Fischer F344 rat left lungs to Wistar Kyoto rats. Allografts with azithromycin therapy from day 1 to 28 or 56 and mono- or combination therapy with the broad-spectrum matrix metalloprotease inhibitor tanomastat from day 1 to 56 were compared to control allografts and isografts. Graft histology was assessed, and tissue cytokine expression studied using Western blotting and immunofluorescence.

RESULTS

The chronic airway rejection score in the azithromycin group did not change between 4 and 8 weeks after transplantation, whereas it significantly worsened in control allografts (P = .041). Azithromycin+tanomastat prevented complete allograft fibrosis, which occurred in 40% of control allografts. Azithromycin reduced interleukin-17 expression (P = .049) and the number of IL-17(+)/CD8(+) lymphocytes at 4 weeks, and active matrix metalloprotease-9 at 8 weeks (P = .017), and increased interleukin-12 expression (P = .025) at 8 weeks following transplantation versus control allografts.

CONCLUSIONS

The expression of interleukin-17 and matrix metalloprotease-9 in bronchiolitis obliterans may be attenuated by azithromycin, and the decrease in interleukin-12 expression was prevented by azithromycin. Combination of azithromycin with a matrix metalloprotease inhibitor is worth studying further because it prevented complete allograft fibrosis in this study.