Explore the vast range of titles available.

Abstract The Wnt/β-catenin pathway initiates a signaling cascade that is critical in cell differentiation and the normal development of multiple organ systems. The reactivation of this pathway has been documented in experimental and human idiopathic pulmonary fibrosis, wherein Wnt/β-catenin activation has been implicated in epithelial-cell repair. Furthermore, the canonical ligand Wnt3a is known to induce myofibroblast differentiation; however, the role of noncanonical Wnt ligands remains unclear. This study showed significantly higher levels of Wnt11 expression in cells from both patients with idiopathic pulmonary fibrosis and bleomycin-treated mice, as well as in TGFβ-treated mouse lung fibroblasts. Moreover, Wnt11 induced myofibroblast differentiation as manifested by increased α-SMA (ACTA2) expression, which was similar to that induced by canonical Wnt3a/β-catenin signaling. Further investigation revealed that Wnt11 induction of α-SMA was associated with the activation of JNK (c-Jun N-terminal kinase)/c-Jun signaling and was inhibited by a JNK inhibitor. The potential importance of this signaling pathway was supported by in vivo evidence showing significantly increased levels of Wnt11 and activated JNK in the lungs of mice with bleomycin-induced pulmonary fibrosis. Interestingly, fibroblasts did not express canonical Wnt3a, but treatment of these cells with exogenous Wnt3a induced endogenous Wnt11 and Wnt5a, resulting in repression of the Wnt3a/β-catenin target gene Axin2. These findings suggested that the noncanonical Wnt induction of myofibroblast differentiation mediated by the JNK/c-Jun pathway might play a significant role in pulmonary fibrosis, in addition to or in synergy with canonical Wnt3a/β-catenin signaling. Moreover, Wnt3a activation of noncanonical Wnt signaling might trigger a switch from canonical to noncanonical Wnt signaling to induce myofibroblast differentiation.

The reactivation of Wnt signaling pathways plays an important role in driving myofibroblast differentiation in fibrotic diseases; however, the mechanism is not clearly understood. In this study, we investigate the role of non-canonical Wnt11 signaling in human lung fibroblasts and its contributions to myofibroblast differentiation. Our results show that components of the non-canonical Wnt pathway are upregulated in bleomycin-induced pulmonary fibrosis and that in vivo depletion of Wnt11 in mouse lung fibroblasts significantly reduces lung fibrosis. Furthermore, co-culture studies using fibroblasts and alveolar type II epithelial cells (AECII) revealed a Wnt11-mediated mechanism that promotes myofibroblast differentiation. Finally, we demonstrate that in human lung fibroblasts, TGFβ can increases Wnt11 transcription by regulating Smad3 binding to the Wnt11 promoter and by modulating Wnt11 promoter activity. Together, these findings identify non-canonical Wnt11 as a regulator of myofibroblast differentiation and lung fibrosis.

Telomerase is typically expressed in cellular populations capable of extended replication, such as germ cells, tumor cells, and stem cells, but is also induced in tissue injury, repair and fibrosis. Its catalytic component, telomerase reverse transcriptase (TERT) is induced in lung fibroblasts from patients with fibrotic interstitial lung disease and in rodents with bleomycin-induced pulmonary fibrosis. To evaluate the fibroblast specific role of TERT in pulmonary fibrosis, transgenic mice bearing a floxed TERT allele were generated, and then crossed with an inducible collagen α2(I)-Cre mouse line to generate fibroblast specific TERT conditional knockout mice. TERT-specific deficiency in mesenchymal cells caused attenuation of pulmonary fibrosis as manifested by reduced lung hydroxyproline content, type I collagen and α-smooth muscle actin mRNA levels. The TERT-deficient mouse lung fibroblasts displayed decreased cell proliferative capacity and higher susceptibility to induced apoptosis compared with control cells. Additionally TERT deficiency was associated with heightened α-smooth muscle actin expression indicative of myofibroblast differentiation. However the impairment of cell proliferation and increased susceptibility to apoptosis would cause a reduction in the myofibroblast progenitor population necessary to mount a successful myofibroblast-dependent fibrotic response. These findings identified a key role for TERT in fibroblast proliferation and survival essential for pulmonary fibrosis.

Idiopathic pulmonary fibrosis (IPF) is a progressive fibrotic lung disease without effective curative therapy. Recent evidence shows increased circulating myeloid-derived suppressor cells (MDSCs) in cancer, inflammation, and fibrosis, with some of these cells expressing B7H3. We sought to investigate the role of MDSCs in IPF and its potential mediation via B7H3. Here we prospectively collected peripheral blood samples from IPF patients to analyze for circulating MDSCs and B7H3 expression to assess their clinical significance and potential impact on co-cultured lung fibroblasts and T-cell activation. In parallel, we assess MDSC recruitment and potential B7H3 dependence in a mouse model of pulmonary fibrosis. Expansion of MDSCs in IPF patients correlated with disease severity. Co-culture of soluble B7H3 (sB7H3)-treated mouse monocytic MDSCs (M-MDSCs), but not granulocytic MDSCs (G-MDSCs), activated lung fibroblasts and myofibroblast differentiation. Additionally, sB7H3 significantly enhanced MDSC suppression of T-cell proliferation. Activated M-MDSCs displayed elevated TGFβ and Arg1 expression relative to that in G-MDSCs. Treatment with anti-B7H3 antibodies inhibited bone marrow-derived MDSC recruitment into the bleomycin-injured lung, accompanied by reduced expression of inflammation and fibrosis markers. Selective telomerase reverse transcriptase (TERT) deficiency in myeloid cells also diminished MDSC recruitment associated with the reduced plasma level of sB7H3, lung recruitment of c-Kit + hematopoietic progenitors, myofibroblast differentiation, and fibrosis. Lung single-cell RNA sequencing (scRNA-seq) revealed fibroblasts as a predominant potential source of sB7H3, and indeed the conditioned medium from activated mouse lung fibroblasts had a chemotactic effect on bone marrow (BM)-MDSC, which was abolished by B7H3 blocking antibody. Thus, in addition to their immunosuppressive activity, TERT and B7H3-dependent MDSC expansion/recruitment from BM could play a paracrine role to activate myofibroblast differentiation during pulmonary fibrosis with potential significance for disease progression mediated by sB7H3.

Organ fibrosis presents a substantial disease burden with few therapeutic options. Innate immunity mediates fibrinogenesis, but also plays a major role in fibrinolysis. Here, we show that immunomodulatory nanoparticles (NPs) can harness this endogenous antifibrotic capacity by catalyzing monocyte activation leading to resolution of bleomycin-induced pulmonary fibrosis . Cargo-free NPs comprised of the degradable biopolymer poly(lactide-co-glycolide) (PLG) induce a transcriptional shift toward antifibrotic immune activation in profibrotic M2 macrophages (MΦs) . NPs stimulate M2 MΦs toward a glycolytic, rather than fatty acid oxidative, metabolism; suppress canonical M2 markers like arginase-1 ( ) and periostin ( ); and upregulate collagenases, hyaluronidases and immunoregulatory factors. When delivered intravenously , NPs reverse established bleomycin-induced pulmonary fibrosis and invert the trajectory of over 1,000 genes from pre- to post-treatment according to bulk RNA-sequencing. NPs also suppress profibrotic signaling and increase expression of repair-associated pathways like peroxisome proliferator-activated receptor gamma (PPAR-γ), nuclear retinoic acid receptor (RAR), vascular endothelial growth factor (VEGF), and sphingolipid signaling in fibrotic lungs. Flow cytometry confirms that NPs induce monocyte recruitment to fibrotic lungs enhanced integrin expression. Altogether, NPs induce a robust pro-regenerative signature comprised of ECM degradation, inflammation resolution, and tissue repair pathways, concomitant with increased NP+ monocyte recruitment to fibrotic lungs. This work demonstrates that monocytes are not intrinsically profibrotic, but rather, their effects are context-dependent, and they retain a capacity for fibrotic resolution under conditions that can be induced by materials with translational potential. Organ fibrosis can follow from tissue injury and substantially impairs organ function, but it is incurable and has limited therapeutic options. Myeloid immune cells drive fibrosis onset and progression, but they can also mediate fibrosis resolution. We used polymeric NPs made from clinically translatable biomaterials to harness the antifibrotic capacity of immune cells as a fibrosis therapy. We found that intravenous NPs can reprogram myeloid cells to acquire an antifibrotic phenotype in a mouse model of pulmonary fibrosis. NPs increased myeloid activation and pulmonary recruitment while decreasing fibrosis, showing that directed immune activation, instead of suppression, could be an effective therapeutic strategy for fibrosis.