Trametinib Attenuates Delayed Rejection and Preserves Thymic Function in Rat Lung Transplantation.

Delayed immunological rejection after human lung transplantation causes chronic lung allograft dysfunction, which is associated with high mortality. Delayed rejection may be attributable to indirect alloantigen presentation by host antigen-presenting cells; however, its pathophysiology is not fully understood. The mitogen-activated protein kinase pathway is activated in T cells upon stimulation, and we previously showed that the MEK inhibitor, trametinib, suppresses graft-versus-host disease after murine bone marrow transplantation. We investigated whether trametinib suppresses graft rejection after two types of rat lung transplantation and analyzed its immunological mode of action. Major histocompatibility complex-mismatched transplantation from brown Norway rats into Lewis rats and minor histocompatibility antigen-mismatched transplantation from Fischer 344 rats into Lewis rats were performed. Cyclosporine (CsA) and/or trametinib were administered alone or consecutively. Acute and delayed rejection, lymphocyte infiltration, and pulmonary function were evaluated. Administration of trametinib after CsA suppressed delayed rejection, reduced inflammatory cell infiltration and fibrosis within the graft, and preserved pulmonary functions at Day 28. Trametinib suppressed functional differentiation of T and B cells in the periphery but preserved thymic T cell differentiation. Donor B cells within the graft disappeared by Day 14, indicating that delayed graft rejection at Day 28 was mainly due to indirect presentation by host antigen-presenting cells. Finally, trametinib administration without CsA preconditioning suppressed rejection after minor histocompatibility antigen-mismatched transplantation. Trametinib attenuates delayed rejection upon major histocompatibility complex-mismatched transplantation by suppressing indirect presentation and is a promising candidate to treat chronic lung allograft dysfunction in humans.

Dual inhibition of the MEK/ERK and PI3K/AKT pathways prevents pulmonary GVHD suppressing perivenulitis and bronchiolitis.

Patients with pulmonary graft-versus-host disease (pGVHD) have a poor prognosis after allogeneic hematopoietic stem cell transplantation (allo-HSCT). Furthermore, pGVHD pathogenesis is not fully elucidated in humans, and currently available immunosuppressants are inadequately effective. We performed pathologic evaluation of lung specimens from 45 allo-HSCT recipients with pGVHD who underwent lung transplantation. Patient pathology was characterized by bronchiolitis and subpleural perivascular inflammation, with B-cell, monocyte, and T-cell accumulation around bronchioles. Bronchiolitis, perivascular inflammation, and peribronchial macrophage aggregation were also identified in a murine pGVHD model after transplant of bone marrow cells and splenocytes from C57BL/6 to B10.BR mice. Among mitogen-activated protein kinase kinase (MEK) inhibitors, cobimetinib, but not trametinib, improved survival rates. Cobimetinib attenuated bronchiolitis, improved airway resistance and lung compliance in the mice, and suppressed activation of B cells and tumor necrosis factor α production by monocytes in vitro; these features were not suppressed by trametinib or tacrolimus. Furthermore, cobimetinib suppressed activation of phosphatidylinositol 3-kinase/protein kinase B (PI3K/AKT) signaling, resulting in B-cell and monocyte suppression. Dual inhibition of the MEK/extracellular signal-regulated kinase (ERK) and PI3K/AKT pathways using a combination of trametinib and the PI3K inhibitor taselisib strongly suppressed B-cell activation in vitro and improved mouse survival rates compared with vehicle or monotherapy with trametinib or taselisib. Imaging mass cytometry of human pGVHD revealed that T cells around bronchioles were positive for phosphorylated ERK, whereas B cells were positive for phosphorylated AKT. Thus, perivascular inflammation and bronchiolitis mediated by activation of the MEK/ERK and PI3K/AKT pathways are essential for pGVHD and represent a potential novel therapeutic target in humans.

Comparison of de novo donor-specific antibodies between living and cadaveric lung transplantation.

BACKGROUND: Despite growing interest in donor-specific antibodies (DSAs) and antibody-mediated rejection (AMR) in lung transplantation (LTx), no study evaluating the outcomes in recipients with de novo DSAs (dnDSAs) in living-donor lobar LTx (LDLLT) exists. We compared various characteristics of DSAs in LDLLT with those in cadaveric LTx (CLT) based on prospectively collected data. METHODS: Between October 2009 and September 2019, 211 recipients underwent LTx (128 CLTs and 83 LDLLTs). We reviewed 108 CLTs and 74 LDLLTs to determine the characteristics and clinical impact of dnDSAs. Eighteen data-deficient cases, 7 cases with preformed DSAs, and 4 re-transplants were excluded. RESULTS: There were significant differences between CLT and LDLLT patients in age, primary disease, ischemic time, and number of human leukocyte antigen mismatches per donor. The dnDSA incidence in LDLLT (6.8%) was significantly lower than that in CLT (19.4%, p = 0.02). The dnDSAs appeared later in LDLLT (mean 1,256 days) than in CLT (mean 196 days, p = 0.003). According to Cox models analyzed using dnDSA as a time-dependent covariate, dnDSA positivity was significantly associated with a poor overall survival (OS; hazard ratio [HR] 3.46, 95% confidence interval [CI] 1.59-7.57, p = 0.002) and poor CLAD-free survival in case of CLT (HR: 2.23, 95% CI: 1.08-4.63, p = 0.003). However, no such significant associations were noted in case of LDLLT. CONCLUSIONS: The dnDSA occurrence was significantly lower and later in LDLLT than in CLT. Furthermore, dnDSA-positivity was significantly associated with worse OS and CLAD-free survival after CLT but not after LDLLT.

Postoperative outcomes of lung transplant recipients with preformed donor-specific antibodies.

OBJECTIVES: Few studies have evaluated the outcomes of lung transplantation (LTx) in recipients with preformed donor-specific antibodies (DSAs). This study investigated the postoperative changes in preformed DSAs based on prospectively collected data of DSAs, and the influences of preformed DSAs on postoperative outcomes among LTx recipients. METHODS: Between July 2010 and December 2019, 216 recipients underwent LTx (81 living-donor lobar lung transplants and 135 deceased-donor lung transplants). We reviewed 8 cases with preformed DSAs to determine postoperative changes in DSAs and compared postoperative outcomes between recipients with and without DSAs. RESULTS: The preoperative mean fluorescence intensity of preformed DSAs ranged from 1141 to 14 695. Two recipients experienced antibody-mediated rejection within 2 weeks after LTx. DSAs disappeared in 7 recipients; however, 1 recipient experienced the relapse of DSAs and died from chronic lung allograft syndrome (CLAD), whereas 1 recipient had persisting DSAs within the study period and died from CLAD. Neither overall survival (OS) nor CLAD-free survival was significantly different between recipients with and without DSAs (P = 0.26 and P = 0.17, respectively). However, both OS and CLAD-free survival were significantly lower in recipients with DSAs against HLA class II than in those without these antibodies {5-year OS: 25.0% [95% confidence interval (CI): 0.9-66.5%] vs 72.1% (95% CI: 63.8-78.9%), P = 0.030 and 5-year CLAD-free survival: 26.7% (95% CI: 1.0-68.6%) vs 73.7% (95% CI: 66.5-79.5%), P = 0.002}. CONCLUSIONS: Prognosis in recipients experiencing the relapse of preformed DSAs and those with persisting DSAs may be poor. The recipients with anti-HLA class II preformed DSAs had a significantly worse prognosis.

LPS-induced Airway-centered Inflammation Leading to BOS-like Airway Remodeling Distinct From RAS-like Fibrosis in Rat Lung Transplantation.

BACKGROUND: Localization of inflammatory stimuli may direct lung allografts to different phenotypes of chronic dysfunction, such as bronchiolitis obliterans syndrome (BOS) or restrictive allograft syndrome (RAS). We hypothesized that airway stimulation with lipopolysaccharide (LPS) in rats leads to airway-centered inflammation similar to human BOS. METHODS: Rat left lung transplantation was conducted (donor: Brown Norway, recipient: Lewis). Allotransplant recipients received cyclosporine A (CsA) until postoperative day 56 with airway instillation of LPS (Allo-LPS, n = 8), phosphate buffered saline (Allo-PBS, n = 5) from days 35 to 46 (3 times a wk), or no further treatment (n = 4). Some allotransplant recipients received CsA until day 14 and were immunosuppression free after day 15 until day 56. Bronchial and pleural fibrosis were semiquantified; alveolar fibrosis was evaluated with a histological scale. RESULTS: The Allo-LPS group had significantly increased International Society for Heart and Lung Transplantation rejection grades (grade A, P = 0.005; grade B, P = 0.004), bronchial obstructive proportion (0.34 ± 0.04% [Allo-LPS] versus 0.11 ± 0.04% [Allo-PBS], P = 0.006), and airway resistance (3.05 ± 1.78 cm H2O·s/mL [Allo-LPS] versus 0.83 ± 0.58 cm H2O·s/mL [Allo-PBS], P = 0.007) compared with other groups. Allotransplant recipients that underwent a short course of CsA developed RAS-like fibrosis involving the airways, alveoli, and pleura. CONCLUSIONS: Airway instillation of LPS in allografts under immunosuppression resulted in BOS-like airway-centered inflammation and fibrosis distinct from RAS-like diffuse fibrosis, which was induced by a shortened course of immunosuppression. We propose novel animal models for BOS and RAS after lung transplantation.

Native upper lobe-sparing living-donor lobar lung transplantation maximizes respiratory function of the donor graft.

BACKGROUND: We have developed a novel method for native upper lobe-sparing living-donor lobar lung transplantation (LDLLT) to overcome a small-for-size graft in standard LDLLT with acceptable results. We hypothesized that grafts implanted with this procedure might work more efficiently than those in standard lobe transplantation. METHODS: Bilateral LDLLT was performed in 31 patients with a functional graft matching of less than 60% at our institution between August 2008 and December 2015. Of these, 22 patients were available for evaluation of pulmonary function more than 1 year later: 15 undergoing standard LDLLT with less than 60% functional matching and 7 undergoing native upper lobe-sparing LDLLT. RESULTS: Overall survival at 2 years was 87.5% in the lobe-sparing LDLLT patients and 79.0% in the standard LDLLT patients (p = 0.401). The median forced vital capacity size-matching levels were 50.7% ± 1.6% in the standard LDLLT and 45.2% ± 2.3% in the sparing LDLLT group (p = 0.074). The 1-year and 2-year post-operative volume ratios of inspiration to expiration were significantly different between the 2 groups, at 1.76 and 1.45 after standard LDLLT (p = 0.019) vs 2.41 and 2.23 after lobe-sparing LDLLT (p = 0.015). CONCLUSIONS: The grafts in lobe-sparing LDLLT functioned more effectively than those in standard LDLLT. This advantage was associated with the improvement of pulmonary functions.

Unilateral Chronic Lung Allograft Dysfunction Assessed by Biphasic Computed Tomographic Volumetry in Bilateral Living-donor Lobar Lung Transplantation.

BACKGROUND: Early diagnosis of unilateral chronic lung allograft dysfunction (CLAD) is difficult because the unaffected contralateral lung functions as a reservoir in bilateral living-donor lobar lung transplantation (LDLLT). We previously reported the usefulness of 133Xe ventilation scintigraphy for detection of unilateral change, but the supply of 133Xe has been stopped globally. The present study aimed to examine the usefulness of inspiratory and expiratory computed tomography (I/E CT) volumetry for detection of unilateral change in CLAD patients. METHODS: This was a retrospective single-center, observational study using prospectively collected data. A total of 58 patients who underwent bilateral LDLLT from August 2008 to February 2017 were analyzed. Respiratory function tests, I/E CT were prospectively conducted. ΔLung volume was defined as the value obtained by subtracting expiratory lung volume from inspiratory lung volume. RESULTS: Fourteen (24%) cases were clinically diagnosed with CLAD, of which 10 (71%) were diagnosed as unilateral CLAD. ΔLung volume of bilateral lungs strongly correlated with forced vital capacity (r = 0.92, P < 0.01) and forced expiratory volume in 1 second (r = 0.80, P < 0.01). Regardless the phenotypes (bronchiolitis obliterans syndrome or restrictive allograft syndrome) of CLAD, Δlung volume onset/baseline significantly decreased compared with that in the non-CLAD group. Among the 10 unilateral CLAD patients, 3 with clinically suspected unilateral rejection yet did not show a 20% decline in forced expiratory volume in 1 second. In 2 of these, Δlung volume of unilateral lungs on the rejection side decreased by 20% or more. CONCLUSIONS: Our findings suggest that I/E CT volumetry may be useful for assessment and early diagnosis of unilateral CLAD after bilateral LDLLT.

Successful conservative management of an anastomotic airway dehiscence at the left main bronchus following bilateral cadaveric lung transplantation.

There is a dearth of data on management of anastomotic airway dehiscence following lung transplantation. Herein we report a case of successful conservative management of an anastomotic airway dehiscence after cadaveric donor lung transplantation. A 41-year-old woman with primary ciliary dyskinesia underwent cadaveric bilateral lung transplantation without cardiopulmonary bypass. On the postoperative day 25, left pneumothorax developed and bronchoscopy demonstrated a localized anastomotic dehiscence at the left main bronchus. The dehiscence was managed with 2 weeks of pleural drainage and was completely covered with regenerated bronchial epithelium at 4 months after transplantation. There is no finding suggestive of significant stenosis at 4 years of follow-up. Our case suggested asymptomatic and localized anastomotic dehiscence does not always require endobronchial stent placement or re-operation. Multiple factors that may contribute to the successful conservative management were discussed in this article.

Living-Donor Lung Transplantation After Bone Marrow Transplantation for Chediak-Higashi Syndrome.

An 8-year-old girl with Chediak-Higashi syndrome (CHS) had pulmonary complications after hematopoietic stem cell transplantation (HSCT) for hemophagocytic lymphohistiocytosis (HLH) and eventually underwent single living-donor lobar lung transplantation (LDLLT). Electron micrographic findings showed vagus nerve tissue in extracted lung having granular inclusions, which are pathognomonic for CHS. Because her mother was the donor for both hematopoietic stem cell and lung transplantations, she was weaned from immunosuppression and is doing well 3 years after lung transplantation. Furthermore, an induced pluripotent stem (iPS) cell line was established from her skin fibroblasts for investigation and potential future treatment for CHS.

Factors affecting the preoperative diagnosis of anterior mediastinal cysts.

OBJECTIVE: Although anterior mediastinal cysts are generally benign diseases, the preoperative diagnosis of these lesions is not necessarily accurate. This study aimed to investigate the factors affecting the preoperative diagnosis of anterior mediastinal cysts. METHODS: We conducted a retrospective analysis of 35 patients with pathologically diagnosed anterior mediastinal cysts (20 thymic cysts, 7 bronchogenic cysts, 5 pericardial cysts, and 3 others) that were resected at our hospital and evaluated their preoperative diagnosis, cyst size, and fluid content. RESULTS: Eighteen, 15, 1, and 1 patient(s) were preoperatively diagnosed with cystic disease, thymoma, thymic cancer, and teratoma, respectively. Cysts were significantly larger in the correct diagnosis group (40.2 ± 18.8 mm) than in the incorrect diagnosis group (21.1 ± 10.4 mm) (p = 0.0011). The cut-off value of the cyst size which separates these groups, as indicated by the receiver operating characteristic curve, was 28 mm, with a sensitivity and specificity of 0.722 and 0.823, respectively. The diagnostic accuracy for mucinous cysts was significantly lower (p < 0.001) than that for serous cysts. CONCLUSION: The presence of cysts smaller than 28 mm and mucinous fluid content was possible factors resulting in inaccurate preoperative diagnosis.

Mediastinal infectious complication after endobronchial ultrasound-guided transbronchial needle aspiration.

We report here a mediastinal infectious complication after endobronchial ultrasound-guided transbronchial needle aspiration (EBUS-TBNA) that was successfully treated using intravenous antibiotic therapy. EBUS-TBNA was performed for a 59-year old man with mediastinal adenopathy 8 years after left pneumonectomy for squamous cell carcinoma of the lung. A single-needle pass produced an adequate cytology and histology sample, and the lesion was diagnosed as small-cell lung cancer. The procedure itself was uneventful, but the patient developed a nightly fever after the biopsy. Finally, he was readmitted, and intravenous antibiotic therapy was required for 4 weeks to treat a mediastinal infection after EBUS-TBNA before chemotherapy for small-cell lung cancer.