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Author Spotlight: Investigating the Key Factors of Obliterative Bronchiolitis After Lung Transplantation
Published on: November 10, 2023
Significant role for microRNA-21 affecting toll-like receptor pathway in primary graft dysfunction after human lung
Zhongping Xu1, Monal Sharma1, Andrew Gelman2
1Department of Surgery, Washington University School of Medicine, St. Louis, Missouri, USA; Norton Thoracic Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona, USA.
Background:
MicroRNAs (miRNAs) were recently identified as modulators of immune responses after human lung transplantation (LTx). This study was undertaken to assess the contribution of miRNAs to the pathogenesis of primary graft dysfunction (PGD) after LTx.
Methods:
Of the 39 recipients, 14 (35.9%) developed Grade 3 PGD (i.e., severe PGD) within the first 72 hours of LTx. The remaining 25 recipients (64.1%) had Grade 2 or less PGD, and served as the control group. miRNAs were isolated from cells purified by bronchoalveolar lavage (BAL). Bioinformatic prediction and validation by luciferase reporter assays were performed to identify targets regulated by miR-21. Transfection of human monocytic cell line (THP-1) was conducted to determine miR-21's cellular function.
Results:
Pilot miRNA profiling of donor BAL samples before implantation in PGD (n = 6) revealed significant upregulation in 44 miRNAs and downregulation in 80 miRNAs compared with control (n = 6). Validation using a separate cohort demonstrated significant underexpression of miR-21 in patients with severe PGD. Furthermore, underexpression of miR-21 levels was negatively correlated with clinical PGD grades (Grade 2 PGD vs Grade 0 PGD: p = 0.042; Grade 3 PGD vs Grade 0 PGD: p = 0.004). Molecular analysis demonstrated that miR-21 targeted key components in the toll-like receptor (TLR) signaling pathway, including TLR4, IRAK3 and CXCL10. Further, incubation of THP-1 cells with cell-free BAL from severe PGD resulted in transactivation of inflammatory cytokines interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α). In contrast, increased expression of miR-21 resulted in marked suppression of IL-1-β and TNF-α production.
Conclusions:
Underexpression of miR-21 may lead to the development of severe PGD by activating key components of the TLR pathway.
Insights
Low miR-21 levels in lung transplant recipients are linked to severe primary graft dysfunction. This suggests miR-21 may protect against PGD by regulating the toll-like receptor pathway.
Area of Science:
- Immunology
- Molecular Biology
- Transplantation Science
Background:
- MicroRNAs (miRNAs) are recognized regulators of immune responses post-lung transplantation (LTx).
- Primary graft dysfunction (PGD) remains a significant challenge after LTx, necessitating research into its underlying mechanisms.
Purpose of the Study:
- To investigate the role of miRNAs in the pathogenesis of PGD following LTx.
- Specifically, to assess the contribution of miR-21 to PGD development and its molecular targets.
Main Methods:
- Analysis of miRNA profiles in bronchoalveolar lavage (BAL) cells from LTx recipients with and without severe PGD.
- Bioinformatic prediction and luciferase assays to identify miR-21 targets.
- In vitro studies using THP-1 cells to determine miR-21's functional impact on inflammatory pathways.
Main Results:
- Significant differential expression of 44 upregulated and 80 downregulated miRNAs was observed in PGD patients.
- Severe PGD was associated with significant underexpression of miR-21, negatively correlated with PGD severity.
- miR-21 was found to target key components of the toll-like receptor (TLR) pathway, including TLR4, IRAK3, and CXCL10.
- Reduced miR-21 levels correlated with increased inflammatory cytokine production (IL-1β, TNF-α), while increased miR-21 suppressed these cytokines.
Conclusions:
- Underexpression of miR-21 is implicated in the development of severe PGD after LTx.
- miR-21 may exert protective effects by modulating the TLR signaling pathway and suppressing inflammatory responses.
