Changes in nascent chromatin structure regulate activation of the pro-fibrotic transcriptome and myofibroblast emergence in organ fibrosis

Complement factor H drives idiopathic pulmonary fibrosis by autocrine C3 regulation, suppressing macrophage phagocytosis and enhancing fibrotic progression

Idiopathic pulmonary fibrosis (IPF) is a chronic and progressive interstitial lung disease with limited therapeutic options. In this study, we identified Complement Factor H (CFH) as a critical regulator in the pathogenesis of IPF, contributing to fibrotic progression through autocrine regulation of complement component C3 and suppression of macrophage phagocytosis. Transcriptomic analysis of IPF lung tissues revealed upregulation of CFH and enrichment of pro-fibrotic pathways, including M2 macrophage infiltration. Weighted Gene Co-expression Network Analysis (WGCNA) and machine learning further validated CFH as a key gene associated with macrophage polarization and fibrotic remodeling. Functional studies demonstrated that CFH deficiency in mouse models attenuated bleomycin-induced pulmonary fibrosis, as evidenced by reduced collagen deposition, improved lung function, and decreased macrophage infiltration. Mechanistically, CFH deficiency enhanced macrophage efferocytosis and autophagy, reducing macrophage-mediated inflammation and fibrosis. Moreover, siRNA-loaded liposomes targeting CFH mitigated pulmonary fibrosis in vivo, further supporting the therapeutic potential of CFH modulation. These findings highlight CFH as a promising therapeutic target for IPF and underscore the importance of complement regulation in macrophage-driven fibrosis.

BRD4: an effective target for organ fibrosis

Fibrosis is an excessive wound-healing response induced by repeated or chronic external stimuli to tissues, significantly impacting quality of life and primarily contributing to organ failure. Organ fibrosis is reported to cause 45% of all-cause mortality worldwide. Despite extensive efforts to develop new antifibrotic drugs, drug discovery has not kept pace with the clinical demand. Currently, only pirfenidone and nintedanib are approved by the FDA to treat pulmonary fibrotic illness, whereas there are currently no available antifibrotic drugs for hepatic, cardiac or renal fibrosis. The development of fibrosis is closely related to epigenetic alterations. The field of epigenetics primarily studies biological processes, including chromatin modifications, epigenetic readers, DNA transcription and RNA translation. The bromodomain and extra-terminal structural domain (BET) family, a class of epigenetic readers, specifically recognizes acetylated histone lysine residues and promotes the formation of transcriptional complexes. Bromodomain-containing protein 4 (BRD4) is one of the most well-researched proteins in the BET family. BRD4 is implicated in the expression of genes related to inflammation and pro-fibrosis during fibrosis. Inhibition of BRD4 has shown promising anti-fibrotic effects in preclinical studies; however, no BRD4 inhibitor has been approved for clinical use. This review introduces the structure and function of BET proteins, the research progress on BRD4 in organ fibrosis, and the inhibitors of BRD4 utilized in fibrosis. We emphasize the feasibility of targeting BRD4 as an anti-fibrotic strategy and discuss the therapeutic potential and challenges associated with BRD4 inhibitors in treating fibrotic diseases.

Fibroblast and myofibroblast activation in normal tissue repair and fibrosis

The term 'fibroblast' often serves as a catch-all for a diverse array of mesenchymal cells, including perivascular cells, stromal progenitor cells and bona fide fibroblasts. Although phenotypically similar, these subpopulations are functionally distinct, maintaining tissue integrity and serving as local progenitor reservoirs. In response to tissue injury, these cells undergo a dynamic fibroblast-myofibroblast transition, marked by extracellular matrix secretion and contraction of actomyosin-based stress fibres. Importantly, whereas transient activation into myofibroblasts aids in tissue repair, persistent activation triggers pathological fibrosis. In this Review, we discuss the roles of mechanical cues, such as tissue stiffness and strain, alongside cell signalling pathways and extracellular matrix ligands in modulating myofibroblast activation and survival. We also highlight the role of epigenetic modifications and myofibroblast memory in physiological and pathological processes. Finally, we discuss potential strategies for therapeutically interfering with these factors and the associated signal transduction pathways to improve the outcome of dysregulated healing.

Osteoporosis: Molecular Pathology, Diagnostics, and Therapeutics

Osteoporosis is a major public health concern affecting millions of people worldwide and resulting in significant economic costs. The condition is characterized by changes in bone homeostasis, which lead to reduced bone mass, impaired bone quality, and an increased risk of fractures. The pathophysiology of osteoporosis is complex and multifactorial, involving imbalances in hormones, cytokines, and growth factors. Understanding the cellular and molecular mechanisms underlying osteoporosis is essential for appropriate diagnosis and management of the condition. This paper provides a comprehensive review of the normal cellular and molecular mechanisms of bone homeostasis, followed by an in-depth discussion of the proposed pathophysiology of osteoporosis through the osteoimmunological, gut microbiome, and cellular senescence models. Furthermore, the diagnostic tools used to assess osteoporosis, including bone mineral density measurements, biochemical markers of bone turnover, and diagnostic imaging modalities, are also discussed. Finally, both the current pharmacological and non-pharmacological treatment algorithms and management options for osteoporosis, including an exploration of the management of osteoporotic fragility fractures, are highlighted. This review reveals the need for further research to fully elucidate the molecular mechanisms underlying the condition and to develop more effective therapeutic strategies.

Fibrosis-the tale of H3K27 histone methyltransferases and demethylases

Fibrosis, or excessive scarring, is characterized by the emergence of alpha-smooth muscle actin (αSMA)-expressing myofibroblasts and the excessive accumulation of fibrotic extracellular matrix (ECM). Currently, there is a lack of effective treatment options for fibrosis, highlighting an unmet need to identify new therapeutic targets. The acquisition of a fibrotic phenotype is associated with changes in chromatin structure, a key determinant of gene transcription activation and repression. The major repressive histone mark, H3K27me3, has been linked to dynamic changes in gene expression in fibrosis through alterations in chromatin structure. H3K27-specific homologous histone methylase (HMT) enzymes, Enhancer of zeste 1 and 2 (EZH1, EZH2), which are the alternative subunits of the Polycomb Repressive Complex 2 (PRC2) and demethylase (KDM) enzymes, Ubiquitously transcribed tetratricopeptide repeat, X chromosome (UTX), and Lysine demethylase 6B (KDM6B), are responsible for regulating methylation status of H3K27me3. In this review, we explore how these key enzymes regulate chromatin structure to alter gene expression in fibrosis, highlighting them as attractive targets for the treatment of fibrosis.