Targeting cluster of differentiation 26 / dipeptidyl peptidase 4 (CD26/DPP4) in organ fibrosis

Endomyocardial fibrosis: recent advances and future therapeutic targets

Endomyocardial fibrosis, first described >75 years ago, is a cause of restrictive cardiomyopathy with an unclear aetiopathogenesis that is most commonly found in children and adolescents from tropical regions of Africa, Asia and South America. The epidemiological trends of this cardiomyopathy are difficult to ascertain. The characteristic hallmark of endomyocardial fibrosis is ventricular fibrosis that causes diastolic dysfunction and atrioventricular regurgitation. Although advances in medical treatment for heart failure and more tailored surgical techniques to treat the condition have increased survival, the outcomes in affected patients remain poor. A major focus of research is the identification of biomarkers of preclinical disease and new therapeutic targets. Collaborative multidisciplinary research and cross-learning from other fibrotic conditions should impart knowledge and help to improve the survival rates and the quality of life of patients with endomyocardial fibrosis.

circ0066187 promotes pulmonary fibrogenesis through targeting STAT3-mediated metabolism signal pathway

Idiopathic pulmonary fibrosis (IPF) is a chronic and progressive interstitial pneumonia, with increasing incidence and prevalence. One of the cellular characteristics is the differentiation of fibroblasts to myofibroblasts. However, the metabolic-related signaling pathway regulated by circular RNAs (circRNAs) during this process remains unclear. Here, we demonstrated that circ0066187 promoted fibroblast-to-myofibroblast differentiation by metabolic-related signaling pathway. Mechanism analysis research identified that circ0066187 directly targeted signal transducer and activator of transcription 3 (STAT3)-mediated metabolism signal pathway to enhance fibroblast-to-myofibroblast differentiation by sponging miR-29b-2-5p, resulting in pulmonary fibrosis. Integrative multi-omics analysis of metabolomics and proteomics revealed three pathways co-enriched in proteomics and metabolomics, namely, Protein digestion and absorption, PI3K-Akt signaling pathway, and FoxO signaling pathway. In these three signaling pathways, seven differentially expressed metabolites such as L-glutamine, L-proline, adenosine monophosphate (AMP), L-arginine, L-phenylalanine, L-lysine and L-tryptophan, and six differentially expressed proteins containing dipeptidyl peptidase-4 (DPP4), cyclin D1 (CCND1), cyclin-dependent kinase 2 (CDK2), fibroblast growth factor 2 (FGF2), collagen type VI alpha 1 (COL6A1) and superoxide dismutase 2 (SOD2) were co-enriched. Gain-and loss-of-function studies and rescue experiments were performed to verify that circ0066187 promoted STAT3 expression by inhibiting miR-29b-2-5p expression to control the above metabolites and proteins. As a result, these metabolites and proteins provided the material basis and energy requirements for the progression of pulmonary fibrosis. In conclusion, circ0066187 can function as a profibrotic metabolism-related factor, and interference with circ0066187 can prevent pulmonary fibrosis. The finding supported that circ0066187 can be a metabolism-related therapeutic target for IPF treatment.

Investigation of the Urinary Peptidome to Unravel Collagen Degradation in Health and Kidney Disease

Naturally occurring fragments of collagen type I alpha 1 chain (COL1A1) have been previously associated with chronic kidney disease (CKD), with some fragments showing positive and others negative associations. Using urinary peptidome data from healthy individuals (n = 1131) and CKD patients (n = 5585) this aspect was investigated in detail. Based on the hypothesis that many collagen peptides are derived not from the full, mature collagen molecule, but from (larger) collagen degradation products, relationships between COL1A1 peptides containing identical sequences were investigated, with the smaller (offspring) peptide being a possible degradation product of the larger (parent) one. The strongest correlations were found for relationships where the parent differed by a maximum of three amino acids from the offspring, indicating an exopeptidase-regulated stepwise degradation process. Regression analysis indicated that CKD affects this degradation process. A comparison of matched CKD patients and control individuals (n = 612 each) showed that peptides at the start of the degradation process were consistently downregulated in CKD, indicating an attenuation of COL1A1 endopeptidase-mediated degradation. However, as these peptides undergo further degradation, likely mediated by exopeptidases, this downregulation can become less significant or even reverse, leading to an upregulation of later-stage fragments and potentially explaining the inconsistencies observed in previous studies.

Transcriptome Analysis of Fibroblasts in Hypoxia-Induced Vascular Remodeling: Functional Roles of CD26/DPP4

In hypoxic pulmonary hypertension (PH), pulmonary vascular remodeling is characterized by the emergence of activated adventitial fibroblasts, leading to medial smooth muscle hyperplasia. Previous studies have suggested that CD26/dipeptidyl peptidase-4 (DPP4) plays a crucial role in the pathobiological processes in lung diseases. However, its role in pulmonary fibroblasts in hypoxic PH remains unknown. Therefore, we aimed to clarify the mechanistic role of CD26/DPP4 in lung fibroblasts in hypoxic PH. Dpp4 knockout (Dpp4 KO) and wild-type (WT) mice were exposed to hypoxia for 4 weeks. The degree of PH severity and medial wall thickness was augmented in Dpp4 KO mice compared with that in WT mice, suggesting that CD26/DPP4 plays a suppressive role in the development of hypoxic PH. Transcriptome analysis of human lung fibroblasts cultured under hypoxic conditions revealed that TGFB2, TGFB3, and TGFA were all upregulated as differentially expressed genes after DPP4 knockdown with small interfering RNA treatment. These results suggest that CD26/DPP4 plays a suppressive role in TGFβ signal-regulated fibroblast activation under hypoxic conditions. Therefore, CD26/DPP4 may be a potential therapeutic target in patients with PH associated with chronic hypoxia.

Anatomical location, sex, and age modulate adipocyte progenitor populations in perivascular adipose tissues

Perivascular adipose tissue (PVAT) regulates vascular function due to its capacity to synthesize vasoactive products and its mechanical properties. PVATs most abundant cells are adipocytes, and their populations are maintained by the maturation of adipocyte progenitor cells (APC), which may play a pivotal role in the pathogenesis of cardiovascular diseases. However, the distribution of APC within PVAT depots, their potential variation in spatial location, and the influence of sex and age on their abundance remain unknown. We hypothesize that APC abundance in PVAT is affected by location, age, sex and that APC subtypes have specific spatial distributions. PVAT from thoracic and abdominal aorta, and mesenteric arteries, and AT from interscapular, gonadal, and subcutaneous depots from 13-week and 30-week-old females and males Pdgfrα-CreERT2 x LSL-tdTomato mice (n = 28) were analyzed. Abdominal aorta PVAT had fewer progenitors than mesenteric PVAT and gonadal AT. Aging reduced the abundance of APC in the thoracic aorta but increased their numbers in mesenteric PVAT. Females had more APC than males in mesenteric PVAT and gonadal AT depots. APC exhibited unique spatial distribution in the aorta and mesenteric PVAT where they localized neighboring vasa vasorum and arteries. APC subtypes (APC1, APC2, APC3, diff APC) were identified in all PVAT depots. Thoracic aorta PVAT APC3 were located in the adventitia while diff APC were in the parenchyma. This study identified variability in APC populations based on depot, age, and sex. The distinctive spatial distribution and the presence of diverse APC subtypes suggest that they may contribute differently to cardiovascular diseases-induced PVAT remodeling.

Functional Roles of CD26/DPP4 in Bleomycin-Induced Pulmonary Hypertension Associated with Interstitial Lung Disease

Pulmonary hypertension (PH) with interstitial lung diseases (ILDs) often causes intractable conditions. CD26/Dipeptidyl peptidase-4 (DPP4) is expressed in lung constituent cells and may be related to the pathogenesis of various respiratory diseases. We aimed to clarify the functional roles of CD26/DPP4 in PH-ILD, paying particular attention to vascular smooth muscle cells (SMCs). Dpp4 knockout (Dpp4KO) and wild type (WT) mice were administered bleomycin (BLM) intraperitoneally to establish a PH-ILD model. The BLM-induced increase in the right ventricular systolic pressure and the right ventricular hypertrophy observed in WT mice were attenuated in Dpp4KO mice. The BLM-induced vascular muscularization in small pulmonary vessels in Dpp4KO mice was milder than that in WT mice. The viability of TGFβ-stimulated human pulmonary artery SMCs (hPASMCs) was lowered due to the DPP4 knockdown with small interfering RNA. According to the results of the transcriptome analysis, upregulated genes in hPASMCs with TGFβ treatment were related to pulmonary vascular SMC proliferation via the Notch, PI3K-Akt, and NFκB signaling pathways. Additionally, DPP4 knockdown in hPASMCs inhibited the pathways upregulated by TGFβ treatment. These results suggest that genetic deficiency of Dpp4 protects against BLM-induced PH-ILD by alleviating vascular remodeling, potentially through the exertion of an antiproliferative effect via inhibition of the TGFβ-related pathways in PASMCs.

Linagliptin Mitigates TGF-β1 Mediated Epithelial-Mesenchymal Transition in Tacrolimus-Induced Renal Interstitial Fibrosis via Smad/ERK/P38 and HIF-1α/LOXL2 Signaling Pathways

The dipeptidyl peptidase-4 (DPP-4) inhibitors, a novel anti-diabetic medication family, are renoprotective in diabetes, but a comparable benefit in chronic non-diabetic kidney diseases is still under investigation. This study aimed to elucidate the molecular mechanisms of linagliptin's (Lina) protective role in a rat model of chronic kidney injury caused by tacrolimus (TAC) independent of blood glucose levels. Thirty-two adult male Sprague Dawley rats were equally randomized into four groups and treated daily for 28 d as follows: The control group; received olive oil (1 mL/kg/d, subcutaneously), group 2; received Lina (5 mg/kg/d, orally), group 3; received TAC (1.5 mg/kg/d, subcutaneously), group 4; received TAC plus Lina concomitantly in doses as the same previous groups. Blood and urine samples were collected to investigate renal function indices and tubular injury markers. Additionally, signaling molecules, epithelial-mesenchymal transition (EMT), and fibrotic-related proteins in kidney tissue were assessed by enzyme-linked immunosorbent assay (ELISA) and Western blot analysis, immunohistochemical and histological examinations. Tacrolimus markedly induced renal injury and fibrosis as indicated by renal dysfunction, histological damage, and deposition of extracellular matrix (ECM) proteins. It also increased transforming growth factor β1 (TGF-β1), Smad4, p-extracellular signal-regulated kinase (ERK)1/2/ERK1/2, and p-P38/P38 mitogen-activated protein kinase (MAPK) protein levels. These alterations were markedly attenuated by the Lina administration. Moreover, Lina significantly inhibited EMT, evidenced by inhibiting Vimentin and α-smooth muscle actin (α-SMA) and elevating E-cadherin. Furthermore, Lina diminished hypoxia-related protein levels with a subsequent reduction in Snail and Twist expressions. We concluded that Lina may protect against TAC-induced interstitial fibrosis by modulating TGF-β1 mediated EMT via Smad-dependent and independent signaling pathways.

Therapeutic targets of fibrosis: Translational advances and current challenges

In a physiological context, the extracellular matrix (ECM) provides an important scaffold for organs. Dysregulation of ECM in disease conditions, characterised by excess deposition of connective tissue and extracellular matrix in response to a pathological insult, is a key driver of disease progression in multiple organs. The resultant fibrosis is predominantly an irreversible process and directly contributes to, and exacerbates, dysfunction of an affected organ. This is particularly paramount in the kidney, liver, heart and lung. A hybrid Joint Meeting of NC-IUPHAR and British Pharmacological Society was held in Paris and via a webinar in November 2020, when two successive sessions were devoted to translational advances in fibrosis as a therapeutic target. On the upsurge of response to these sessions, the concept of a special themed issue on this topic emerged, and is entitled Translational Advances in Fibrosis as a Therapeutic Target. In this special issue, we seek to provide an up-to-date account of the diverse molecular mechanisms and causal role that fibrosis plays in disease progression (contributing to, and exacerbating, dysfunction of affected organs). Recent developments in the understanding of molecular targets involved in fibrosis, and how their actions can be manipulated therapeutically, are included. LINKED ARTICLES: This article is part of a themed issue on Translational Advances in Fibrosis as a Therapeutic Target. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v180.22/issuetoc.

Is Spheroid a Relevant Model to Address Fibrogenesis in Keloid Research?

Keloid refers to a fibro-proliferative disorder characterized by an accumulation of extracellular matrix at the dermis level, overgrowing beyond the initial wound and forming tumor-like nodule areas. The absence of treatment for keloid is clearly related to limited knowledge about keloid etiology. In vitro, keloids were classically studied through fibroblasts monolayer culture, far from keloid in vivo complexity. Today, cell aggregates cultured as 3D spheroid have gained in popularity as new tools to mimic tissue in vitro. However, no previously published works on spheroids have specifically focused on keloids yet. Thus, we hypothesized that spheroids made of keloid fibroblasts (KFs) could be used to model fibrogenesis in vitro. Our objective was to qualify spheroids made from KFs and cultured in a basal or pro-fibrotic environment (+TGF-β1). As major parameters for fibrogenesis assessment, we evaluated apoptosis, myofibroblast differentiation and response to TGF-β1, extracellular matrix (ECM) synthesis, and ECM-related genes regulation in KFs spheroids. We surprisingly observed that fibrogenic features of KFs are strongly downregulated when cells are cultured in 3D. In conclusion, we believe that spheroid is not the most appropriate model to address fibrogenesis in keloid, but it constitutes an efficient model to study the deactivation of fibrotic cells.