Transforming growth factor-beta1 gene transfer ameliorates acute lung allograft rejection

Regulatory T cells in lung disease and transplantation

Pulmonary disease can refer to the disease of the lung itself or the pulmonary manifestations of systemic diseases, which are often connected to the malfunction of the immune system. Regulatory T (Treg) cells have been shown to be important in maintaining immune homeostasis and preventing inflammatory damage, including lung diseases. Given the increasing amount of evidence linking Treg cells to various pulmonary conditions, Treg cells might serve as a therapeutic strategy for the treatment of lung diseases and potentially promote lung transplant tolerance. The most potent and well-defined Treg cells are Foxp3-expressing CD4+ Treg cells, which contribute to the prevention of autoimmune lung diseases and the promotion of lung transplant rejection. The protective mechanisms of Treg cells in lung disease and transplantation involve multiple immune suppression mechanisms. This review summarizes the development, phenotype and function of CD4+Foxp3+ Treg cells. Then, we focus on the therapeutic potential of Treg cells in preventing lung disease and limiting lung transplant rejection. Furthermore, we discussed the possibility of Treg cell utilization in clinical applications. This will provide an overview of current research advances in Treg cells and their relevant application in clinics.

Gene Therapy for Acute Respiratory Distress Syndrome

Acute respiratory distress syndrome (ARDS) is a devastating clinical syndrome that leads to acute respiratory failure and accounts for over 70,000 deaths per year in the United States alone, even prior to the COVID-19 pandemic. While its molecular details have been teased apart and its pathophysiology largely established over the past 30 years, relatively few pharmacological advances in treatment have been made based on this knowledge. Indeed, mortality remains very close to what it was 30 years ago. As an alternative to traditional pharmacological approaches, gene therapy offers a highly controlled and targeted strategy to treat the disease at the molecular level. Although there is no single gene or combination of genes responsible for ARDS, there are a number of genes that can be targeted for upregulation or downregulation that could alleviate many of the symptoms and address the underlying mechanisms of this syndrome. This review will focus on the pathophysiology of ARDS and how gene therapy has been used for prevention and treatment. Strategies for gene delivery to the lung, such as barriers encountered during gene transfer, specific classes of genes that have been targeted, and the outcomes of these approaches on ARDS pathogenesis and resolution will be discussed.

Acute respiratory distress syndrome: new definition, current and future therapeutic options

Since acute respiratory distress syndrome (ARDS) was first described in 1967 there has been large number of studies addressing its pathogenesis and therapies. Despite this intense research activity, there are very few effective therapies for ARDS other than the use of lung protection strategies. This lack of therapeutic modalities is not only related to the complex pathogenesis of this syndrome but also the insensitive and nonspecific diagnostic criteria to diagnose ARDS. This review article will summarize the key features of the new definition of ARDS, and provide a brief overview of innovative therapeutic options that are being assessed in the management of ARDS.

Gene therapy for ALI/ARDS

Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) are characterized by acute respiratory failure and are associated with diverse disorders. Gene therapy is a potentially powerful approach to treat diseases related to ALI/ARDS, and numerous viral and nonviral methods for gene delivery to the lung have been developed. Discussed are recent advances in the development of more efficient viral and nonviral gene transfer systems, and the current status of gene therapy applied to ALI/ARDS-associated pulmonary diseases is reviewed. With the development of more efficient gene therapy vectors, gene therapy is a promising strategy for clinical application.

Inhibitory effect of dietary n-3 polyunsaturated fatty acids to intestinal IL-15 expression is associated with reduction of TCRαβ+CD8α+CD8β− intestinal intraepithelial lymphocytes

Intestinal intraepithelial lymphocytes (IELs) and their cytokines play an important role in the regulation of gut immune response and take part in gut immune barrier function. n-3 polyunsaturated fatty acid (PUFA) is an immunoregulator that has been shown to influence the process of gut inflammation. Interleukin (IL)-15 is a T-cell growth factor that has been shown to influence the differentiation of IEL. The aim of this study was to analyze the effects of dietary n-3 PUFA on IEL. IEL phenotype and cytokine (TNF-alpha, IFN-gamma, IL-4, IL-10 and TGF-beta1) profile were measured by FACS and real-time RT-PCR in healthy adult rats fed with fish oil diet for 90 days. Rats fed with corn oil diet served as controls. Intestinal IL-15 expression was measured by immunohistochemistry and real-time RT-PCR. The results demonstrated a decrease of intestinal IL-15 expression in the fish oil group. Associated with this deduction, n-3 PUFA significantly decreased the proportion of TCRalphabeta+CD8alpha+CD8beta- cells and IEL-derived TNF-alpha, IFN-gamma, IL-4 and IL-10. In conclusion, n-3 PUFA could inhibit intestinal mucosal expression of IL-15 and may influence phenotype and function of IEL through this mechanism.

T regulatory cells in stable posttransplant bronchiolitis obliterans syndrome

BACKGROUND

Obliterative bronchiolitis (OB), mainly mediated by T cells, remains the major cause of morbidity and death in long-term lung transplant. Acute rejection (AR), also a T-cell mediated process, is strongly linked to OB. For unknown reasons, several patients with OB halt their pulmonary function decline and stabilize their obstructive defect for a long period. Our aim was to assess the T-cell activation in blood, induced sputum, and broncho-alveolar lavage during AR, stable OB (sOB), and evolving OB (eOB).

METHODS

T-cell phenotype and cytokine production were assessed by flow cytometry in these three compartments. Interleukin-4, interferon-gamma and transforming growth factor (TGF)-beta levels were measured by enzyme-linked immunosorbent assay in blood cell culture supernatants. Results were compared between healthy lung transplant recipients and AR (n=7), sOB (n=7), and eOB (n=13).

RESULTS

Stable and evolutive OB were characterized by a Treg, Th1, and Th2 activation, but compared to eOB, Treg and Th2 cells predominated in sOB. A clear Th1 activation was observed in AR. TGF-beta was increased in AR and evolving OB.

CONCLUSION

These preliminary results indicate a contrasted T-cell activation profile depending on the clinical conditions. We speculate that Treg cells could counterbalance the Th0 activation seen in evolving OB and participate in stabilization of airway obstruction.

Pirfenidone inhibits obliterative airway disease in mouse tracheal allografts

BACKGROUND

Obliterative bronchiolitis (OB) is the histologic correlate of chronic airway rejection, which remains the most significant cause of death in long-term survivors of lung transplantation. Using an established murine heterotopic tracheal transplant model of chronic airway rejection, the effects of the oral anti-fibrotic agent pirfenidone on development of the OB-like lesion were evaluated.

METHODS

Tracheas from BALB/c mice were implanted into the sub-cutaneous tissue of C57BL/6 mice, and the allografts were evaluated morphologically for airway rejection changes and immunohistochemically for transforming growth factor (TGF)-beta at 16 or 28 days after transplantation. In addition, the potential additive effects of pirfenidone in combination with 2 immunosuppressive agents, cyclosporine or rapamycin, was evaluated.

RESULTS

Compared with untreated controls, pirfenidone-fed mice showed less epithelial cell injury and luminal granulation tissue and fibrosis. Plasma TGF-beta levels and local TGF-beta expression based on immunohistochemistry were decreased in the pirfenidone-treated animals. Pirfenidone given on Day 9 or 16 post-transplant through Day 28 resulted in no significant improvement compared with controls. There was no significant additive effect of pirfenidone in combination with cyclosporine, whereas pirfenidone plus rapamycin demonstrated additive protection against the development of the obstructive airway lesion.

CONCLUSIONS

In aggregate, these results show that the anti-fibrotic agent pirfenidone inhibits the development of the OB-like lesion in this mouse model of human chronic airway rejection, and that these effects may be mediated by TGF-beta. The results also suggest that pirfenidone may be worthy of investigation in human lung transplant recipients at high risk of developing OB.

Gene Therapy for Lung Diseases

Gene therapy is under development for a variety of lung disease, both those caused by single gene defects, such as cystic fibrosis and α₁-antitrypsin deficiency, and multifactorial diseases such as cancer, asthma, lung fibrosis, and ARDS. Both viral and nonviral approaches have been explored, the major limitation to the former being the inability to repeatedly administer, which renders this approach perhaps more applicable to conditions requiring single administration, such as cancer. Progress in development and clinical trials in each of these diseases is reviewed, together with some potential newer approaches for the future.

Smad3 deficiency ameliorates experimental obliterative bronchiolitis in a heterotopic tracheal transplantation model

Chronic allograft rejection manifested as obliterative bronchiolitis (OB) remains the single greatest impediment to long-term survival after lung transplantation. Transforming growth factor-beta1 (TGF-beta1) has been implicated in the tissue remodeling response associated with OB. Therefore, its intracellular signal transducer, Smad3, is a prime target of investigation. Herein, we examine the role of TGF-beta1, through Smad3, in the development of OB using heterotopic tracheal transplantation in wild-type and Smad3-null mice. TGF-beta1 was detectable within infiltrating mononuclear cells early after transplantation. Later it was detected in fibroblasts and in the connective tissue accumulating within the lumen and the airway wall of the transplanted allografts. Connective tissue growth factor had a similar time and tissue distribution. Nuclear detection of Smad3 and phosphorylated Smads within intraluminal fibroblasts coincided with increased intraluminal deposition of fibronectin and collagen. When transplanted into Smad3-null mice, allografts failed to organize the intraluminal exudates despite fibroblast accumulation and showed reduced fibronectin and collagen deposition. In culture, Smad3-deficient fibroblasts expressed reduced fibronectin in response to TGF-beta1 compared to wild-type cells. Together, these studies suggest that the TGF-beta signal transducer, Smad3, is required for the development of experimental OB in transplanted tracheas.

Gene transfer of tumor necrosis factor inhibitor improves the function of lung allografts

BACKGROUND

Tumor necrosis factor is an important mediator of lung transplant acute rejection. Soluble type I tumor necrosis factor receptor binds to tumor necrosis factor-alpha and -beta and inhibits their function. The objectives of this study were to demonstrate efficient in vivo gene transfer of a soluble type I tumor necrosis factor receptor fusion protein (sTNF-RI-Ig) and determine its effects on lung allograft acute rejection.

METHODS

Three groups of Fischer rats (n = 6 per group) underwent recipient intramuscular transfection 24 hours before transplantation with saline, 1 x 10(10) plaque-forming units of control adenovirus encoding beta-galactosidase, or 1 x 10(10) plaque-forming units of adenovirus encoding human sTNF-RI-Ig (Ad.sTNF-RI-Ig). One group (n = 6) received recipient intramuscular transfection with 1 x 10(10) Ad.sTNF-RI-Ig at the time of transplantation. Brown Norway donor lung grafts were stored for 5 hours before orthotopic lung transplantation. Graft function and rejection scores were assessed 5 days after transplantation. Time-dependent transgene expression in muscle, serum, and lung grafts were evaluated by using enzyme-linked immunosorbent assay of human soluble type I tumor necrosis factor receptor.

RESULTS

Recipient intramuscular transfection with 1 x 10(10) plaque-forming units of Ad.sTNF-RI-Ig significantly improved arterial oxygenation when delivered 24 hours before transplantation compared with saline, beta-galactosidase, and Ad.sTNF-RI-Ig transfection at the time of transplantation (435.8 +/- 106.6 mm Hg vs 142.3 +/- 146.3 mm Hg, 177.4 +/- 153.7 mm Hg, and 237.3 +/- 185.2 mm Hg; P =.002,.005, and.046, respectively). Transgene expression was time dependent, and there was a trend toward lower vascular rejection scores (P =.066) in the Ad.sTNF-RI-Ig group transfected 24 hours before transplantation.

CONCLUSIONS

Recipient intramuscular Ad.sTNF-RI-Ig gene transfer improves allograft function in a well-established model of acute rejection. Maximum benefit was observed when transfection occurred 24 hours before transplantation.

Intratracheal adenovirus-mediated gene transfer is optimal in experimental lung transplantation

OBJECTIVE

Gene transfer to experimental lung grafts has been shown to reduce ischemia-reperfusion injury and acute rejection. The optimal delivery route should produce high lung expression with no inflammation and minimal systemic expression. The goal of this study was to determine the optimal gene transfer route for use in experimental lung transplantation.

METHODS

F344 rats were injected with 2.9 x 10(10) plaque-forming units of adenovirus vector encoding beta-galactosidase through intratracheal, intravenous, intraperitoneal, or intramuscular delivery routes and killed 48 hours later. Gene expression was measured by means of enzyme-linked immunosorbent assay.

RESULTS

Intratracheal delivery produces significantly greater gene expression in the lung (75,350 +/- 47,288 pg/100 microg of protein, P <.001 vs intravenous, intraperitoneal, and intramuscular routes) and minimal systemic expression (nonsignificant in serum, kidney, liver, spleen, and muscle vs that seen in control animals, P =.016 for heart). Immunohistochemistry staining showed beta-galactosidase expression in the bronchial epithelium of lungs transfected through the intratracheal route with mild inflammation.

CONCLUSIONS

Intratracheal gene transfer provides significant expression in the lung with mild to no inflammation and minimal systemic expression. This delivery strategy has tremendous potential in experimental lung transplant models to reduce ischemia-reperfusion injury and acute allograft rejection and should be investigated further.