Local Origin of Mesenchymal Cells in a Murine Orthotopic Lung Transplantation Model of Bronchiolitis Obliterans

Abstract

Bronchiolitis obliterans is the leading cause of chronic graft failure and long-term mortality in lung transplant recipients. Here, we used a novel murine model to characterize allograft fibrogenesis within a whole-lung microenvironment. Unilateral left lung transplantation was performed in mice across varying degrees of major histocompatibility complex mismatch combinations. B6D2F1/J (a cross between C57BL/6J and DBA/2J) (Haplotype H2b/d) lungs transplanted into DBA/2J (H2d) recipients were identified to show histopathology for bronchiolitis obliterans in all allogeneic grafts. Time course analysis showed an evolution from immune cell infiltration of the bronchioles and vessels at day 14, consistent with acute rejection and lymphocytic bronchitis, to subepithelial and intraluminal fibrotic lesions of bronchiolitis obliterans by day 28. Allografts at day 28 showed a significantly higher hydroxyproline content than the isografts (33.21 ± 1.89 versus 22.36 ± 2.33 μg/mL). At day 40 the hydroxyproline content had increased further (48.91 ± 7.09 μg/mL). Flow cytometric analysis was used to investigate the origin of mesenchymal cells in fibrotic allografts. Collagen I-positive cells (89.43% ± 6.53%) in day 28 allografts were H2Db positive, showing their donor origin. This novel murine model shows consistent and reproducible allograft fibrogenesis in the context of single-lung transplantation and represents a major step forward in investigating mechanisms of chronic graft failure.

Telomere Dysfunction Drives Chronic Lung Allograft Dysfunction Pathology

“…MHC mismatched orthotopic transplantation models reproduce features of acute rejection, but not necessarily CLAD. (46)(47)(48)(49). Transplantation of B6D2F1/J lungs to DBA recipients has shown promise in development of CLAD-like pathology, but the DBA background may be a limitation because of the paucity of available genetic knockout models.…”

Models of Lung Transplant Research: a consensus statement from the National Heart, Lung, and Blood Institute workshop

“…Investigation of fibrotic lesions in the HTT model have shown them to be derived from the recipients (132). Utilizing the expression of H-2D b to differentiate donor versus recipient origin of the mesenchymal cell population in lung allografts, approximately 90% of collagen I-expressing cells in the B6D2F1/J→DBA/2J orthotopic model were of donor origin (120). These investigations suggest that the whole-lung transplant model holds an advantage over tracheal transplantation in studies of mesenchymal cell recruitment and activation, as it is more reflective of mesenchymal populations involved in pathogenesis of OB in human lungs.…”

“…More recently, investigators at the University of Michigan examined transplant of an F1 to a parent mouse to obtain moderate MHC mismatching that was less antigenically disparate (120). A similar strategy has been previously employed in the field of bone marrow transplantation to study chronic graftversus-host disease (GVHD) with injection of parental cells into F1 recipients or complete MHC mismatch (121)(122)(123)(124)(125)(126).…”

“…These studies demonstrate how the interplay between local innate immunity and alloreactive T cell subsets and alloantibody deposition contribute to chronic pulmonary GVHD with fibrotic (including OB-like) pathology. The specific combination of transplantation of B6D2F1/J (cross between C57BL/6J and H-2-b/d ) lungs into DBA/2J (H-2-d ) recipients results in consistent OB-like pathology with peribronchial and perivascular fibrosis by day 28 (120). These grafts, which are discordant at the class I allele (H-2D b ) with the recipient, demonstrate an evolution from immune cell infiltration to epithelial cell injury and development of fibrosis over time that is reminiscent of human disease.…”

Chronic lung allograft dysfunction phenotypes and treatment

“…For example, it was shown that progressive loss of self-tolerance through epitope spreading promotes airway fibrosis (22). In another experiment, it has been shown that the murine lung allograft fibrosis originates mostly from the donor (23). However, these results cannot be directly extrapolated from mice to men as in humans, 32% of OB lesions are occupied by recipient and not donor fibroblasts (24).…”