Overexpression of Hypoxia-Inducible Factor-1α in Primary Graft Dysfunction Developing in an Orthotopic Lung Transplantation Rat Model

Background: Primary graft dysfunction (PGD) is the major cause of early morbidity and mortality after transplantation. A high rate of PGD is a frequent complication in orthotopic lung transplantation (OLT) models, which are currently used to investigate acute and chronic rejection pathways. Hypoxia-inducible factor (HIF)-1α is a heterodimeric αβ transcription factor that mediates tissue response to hypoxia. In other solid organ transplantations, a significant correlation between HIF-1α expression and PGD was detected. To our knowledge no data are available on HIF-1α expression in PGD developing in lung transplantation. The aims of this study were to investigate HIF-1α expression (using immunohistochemistry) and correlate it to the main histological parameters related to ischemia-reperfusion (IR) injury, including terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) -positive apoptotic cells).

Methods: OLT was performed in 32 inbred rat strains and 11 of them died in the early postoperative period (from day 0-3) for IR injury. The histological and molecular evaluations were done in all lung tissues. Unimplanted donor rat lungs were used as controls. HIF-1α expression was correlated with all morphological parameters.

Results: Lung samples of animals with IR injury showed high scores of HIF-1α expression, edema, blood extravasation, granulocyte margination, apoptotic index, and necrosis in 91% of cases. Tissue overexpression of HIF-1α was detected in all lung samples with high scores of histological parameters and with high apoptotic indexes.

Conclusion: Our data demonstrate that HIF-1α was overexpressed in more severe rat lung IR injury. The use of HIF-1α inhibitors could provide a translatable route into manipulating this complex system in vivo.