Chronic Airway Fibrosis in Orthotopic Mouse Lung Transplantation Models—An Experimental Reappraisal

Abstract

BACKGROUND: Several mouse lung transplantation (Tx) models have been proposed for the study of chronic airway fibrosis (CAF), the most prevalent complication seen in human lung transplant recipients, termed chronic lung allograft dysfunction (CLAD). Alternatively, it has been called for to establish an experimental animal model for restrictive allograft syndrome (RAS), another phenotype of CLAD. However, these mouse transplant models exhibit significant heterogeneity in consistency and reproducibility. We therefore aimed at reevaluating current available models. METHODS: 4 different Tx combinations were employed that manifest CAF: 2 minor antigen-mismatched Tx combinations (MINOR, donor: C57BL/10, recipient: C57BL/6J); or MINOR-N using recipient C57BL/6N, major histocompatibility antigen-mismatched immunosuppressed Tx (MAJOR, donor: BALB/c, recipient: C57BL/6J) and syngeneic Tx (SYN, donor and recipient: C57BL/6J) as control. The recipients were harvested and analyzed at week 8. Oxygenation, histology, reverse transcription polymerase chain reaction (RT-PCR), and magnetic resonance imaging were performed to analyze outcome of those models. RESULTS: The most prominent manifestation of CAF, thickest subepithelial fibrotic changes, worst oxygenation and the most severe acute rejection were detected in the MAJOR group, compared to all other (p<0.05). Gene expressions of TNF-and TGF-1 were higher, and IL-10 was lower in the MAJOR group. Immunohistochemistry found pleuroparenchymal fibrotic change in both the MAJOR and MINOR-J group. CONCLUSIONS: We propose the major mismatch model under mild immunosuppression as the most suitable model for studying posttransplant CAF, and both the major and minor mismatch models for the restrictive phenotype. Author's contributionsYY contributed to the experimental surgeries and retrieved and analyzed the data and codrafted the manuscript (MS); KK and LD analyzed the data; DK retrieved and analyzed the data; JJH contributed to the data analysis; II co-drafted the MS; AB contributed the data analysis and codrafted the MS; TM contributed the data analyses; WW codrafted the MS; WJ designed and coordinated the study and wrote the MS. All authors read and approved the final manuscript. DisclosureThe authors declare no conflicts of interest. FundingNone A C C E P T E D 4 AbstractBackground: Several mouse lung transplantation (Tx) models have been proposed for the study of

A B cell–dependent pathway drives chronic lung allograft rejection after ischemia–reperfusion injury in mice

“…21,22,25,[34][35][36][37][38] We have found that fibrosis diminishes over time with surgical experience, and currently we observe minimal fibrosis in allografts not subjected to IRI, in contrast to our earlier data. Allograft fibrosis in the B10→B6 LT model is highly variable among different surgeons and research groups, whereas AR is mild but reproducible.…”

“…Allograft fibrosis in the B10→B6 LT model is highly variable among different surgeons and research groups, whereas AR is mild but reproducible. 21,22,25,[34][35][36][37][38] We have found that fibrosis diminishes over time with surgical experience, and currently we observe minimal fibrosis in allografts not subjected to IRI, in contrast to our earlier data. 20 We therefore hypothesized that the limited fibrotic WIT nor 30 minutes CIT plus 60 minutes WIT caused CR (not shown).…”

“…the B10-to-B6 orthotopic LT model: ranging from as high as ~50% 20,21,25,[35][36][37]46 to none. 22,34 We have found that fibrosis diminishes with time and operator experience -as illustrated by a comparison between our current AlloMin grafts (Figure 3A,D) and equivalent grafts in our recent reports. 20,25 Although the precise reasons for reduced fibrosis are unclear, it is likely that inflammation resulting from preservation and surgical injury, and other factors such as the microbiome, 38,47 influence its development.…”

“…20 We observed consistent mild acute rejection (AR) and variable fibrosis, similar to Fan et al 21 Subsequently, we saw a decreasing incidence and severity of fibrosis -with preserved mild AR -with increasing experience, making our findings more similar to those of Yamada and associates. 22 We therefore hypothesized that innate immune activation in the lung allograft would restore fibrosis, and consequently we elected to investigate the link between IRI and CR after LT.…”

Detection of lung transplant rejection in a rat model using hyperpolarized [1‐13C] pyruvate‐based metabolic imaging

“…While the relative contributions of CD4+ and CD8+ T cell subsets to rejection are unclear, the CD4+ alloimmune response is typically short‐lived due to the destruction of donor antigen‐presenting cells (APCs) post‐transplantation . The principal alloimmune response therefore appears to be largely mediated by CD8+ CTLs, although this response may vary according to the transplant model and species . In our study, both CD4+ and CD8+ seemingly play a role in the rejection process on day 3; the CD4+ signal declines on day 7; however, the CD8+ signal doubles, suggesting that the CD8+ T‐cell response is the principal mediator of rejection (Figures and ).…”