Joint effects of green space and air pollutant exposure on preterm birth: evidence from a nationwide study in China.

An association between green space exposure and preterm birth has been reported. However, evidence on the joint effects of air pollutant and green space exposure on preterm birth from nationwide research is limited in China. Based on a nationwide cohort, this study aims to explore the effect of green space exposure on preterm birth and analyze the joint effects of green space and air pollutant. Logistic regression models were developed to analyze the effects of green space exposure, and interaction effects were evaluated by adding interaction terms between green space and air pollutants. From 2013 to 2019, this study included 2,294,188 records of newborn births, of which 82,921 were preterm births. The results show that for buffer zones with 250 m, 500 m, 1000 m, and 1500 m, every 0.1 unit increase in NDVI exposure was associated with a decrease in the risk of preterm birth by 5.5% (95% CI: 4.6-6.4%), 5.8% (95% CI: 4.9-6.6%), 6.1% (95% CI: 5.3-7.0%), and 5.6% (95% CI: 4.7-6.5%), respectively. Under high-level exposure to air pollutants, high-level NDVI exposure was more strongly negatively correlated with preterm birth than low-level NDVI exposure. High-level green space exposure might mitigate the adverse effect of air pollutants on preterm birth by promoting physical activity, reducing stress, and adsorbing pollutants. Further investigation is needed to explore how green space and air pollution interact and affect preterm birth, in order to improve risk management and provide a reference for newborn health.

Loss of m6A demethylase ALKBH5 alleviates hypoxia-induced pulmonary arterial hypertension via inhibiting Cyp1a1 mRNA decay.

BACKGROUND: Hypoxia-induced pulmonary artery hypertension (HPH) is a complication of chronic hypoxic lung disease and the third most common type of pulmonary artery hypertension (PAH). Epigenetic mechanisms play essential roles in the pathogenesis of HPH. N6-methyladenosine (m6A) is an important modified RNA nucleotide involved in a variety of biological processes and an important regulator of epigenetic processes. To date, the precise role of m6A and regulatory molecules in HPH remains unclear. METHODS: HPH model and pulmonary artery smooth muscle cells (PASMCs) were constructed from which m6A changes were observed and screened for AlkB homolog 5 (Alkbh5). Alkbh5 knock-in (KI) and knock-out (KO) mice were constructed to observe the effects on m6A and evaluate right ventricular systolic pressure (RVSP), left ventricular and septal weight [RV/(LV + S)], and pulmonary vascular remodeling in the context of HPH. Additionally, the effects of Alkbh5 knockdown using adenovirus were examined in vitro on m6A, specifically in PASMCs with regard to proliferation, migration and cytochrome P450 1A1 (Cyp1a1) mRNA stability. RESULTS: In both HPH mice lung tissues and hypoxic PASMCs, a decrease in m6A was observed, accompanied by a significant up-regulation of Alkbh5 expression. Loss of Alkbh5 attenuated the proliferation and migration of hypoxic PASMCs in vitro, with an associated increase in m6A modification. Furthermore, Alkbh5 KO mice exhibited reduced RVSP, RV/(LV + S), and attenuated vascular remodeling in HPH mice. Mechanistically, loss of Alkbh5 inhibited Cyp1a1 mRNA decay and increased its expression through an m6A-dependent post-transcriptional mechanism, which hindered the proliferation and migration of hypoxic PASMCs. CONCLUSION: The current study highlights the loss of Alkbh5 impedes the proliferation and migration of PASMCs by inhibiting post-transcriptional Cyp1a1 mRNA decay in an m6A-dependent manner.

Naturally Occurring Atherosclerosis Progression and In-Stent Restenosis: Exploring Histomorphological Associations Using Optical Coherence Tomography.

ABSTRACT: The mechanism of in-stent restenosis (ISR) remains elusive, and in-stent neoatherosclerosis (ISNA) may hold siginificant pathophysiological implications. Nevertheless, the correlation between ISNA and the progression of untreated coronary segments affected by native atherosclerosis remains incompletely investigated. This study enrolled 225 patients diagnosed with coronary heart disease and multivessel disease (MVD). These patients underwent successful percutaneous coronary intervention (PCI) and intraoperative placement of drug-eluting stent (DES), followed by optical coherence tomography (OCT) assessment of the culprit stent. The mechanism of ISR was emamined through qualitative and quantitative analysis of OCT imaging. A significantly higher proportion of patients in the ISR with non-target lesion progression (N-TLP) group exhibited lipid plaque formation compared to the ISR without N-TLP group (69.0% versus 39.8%, P < 0.001). The incidence of thin-cap fibroatheroma (TCFA) (33.3% versus 11.4%, P = 0.001) and ISNA (60.7% versus 38.6%, P < 0.001) was markedly elevated in the ISR with N-TLP group compared to the ISR without N-TLP group. Regarding manifestations, heterogeneous hyperplasia was predominantly observed in the ISR with N-TLP group (76.2% versus 38.6%, P < 0.001), while homogeneous hyperplasia was primarily presented in the ISR without N-TLP group (61.4% versus 23.8%, P < 0.001). Patients displaying notable progression of naturally occurring atherosclerosis manifest histomorphological features of ISR, primarily characterized by heterogeneous intimal hyperplasia and a higher prevalence of ISNA. In contrast, patients without substantial progression of naturally occurring atherosclerosis exhibit histomorphologic features of ISR primarily characterized by homogeneous intimal hyperplasia.

Semaphorin3A Exacerbates Cardiac Microvascular Rarefaction in Pressure Overload-Induced Heart Disease.

Microvascular endothelial cells (MiVECs) impair angiogenic potential, leading to microvascular rarefaction, which is a characteristic feature of chronic pressure overload-induced cardiac dysfunction. Semaphorin3A (Sema3A) is a secreted protein upregulated in MiVECs following angiotensin II (Ang II) activation and pressure overload stimuli. However, its role and mechanism in microvascular rarefaction remain elusive. The function and mechanism of action of Sema3A in pressure overload-induced microvascular rarefaction, is explored, through an Ang II-induced animal model of pressure overload. RNA sequencing, immunoblotting analysis, enzyme-linked immunosorbent assay, quantitative reverse transcription polymerase chain reaction (qRT-PCR), and immunofluorescence staining results indicate that Sema3A is predominantly expressed and significantly upregulated in MiVECs under pressure overload. Immunoelectron microscopy and nano-flow cytometry analyses indicate small extracellular vesicles (sEVs), with surface-attached Sema3A, to be a novel tool for efficient release and delivery of Sema3A from the MiVECs to extracellular microenvironment. To investigate pressure overload-mediated cardiac microvascular rarefaction and cardiac fibrosis in vivo, endothelial-specific Sema3A knockdown mice are established. Mechanistically, serum response factor (transcription factor) promotes the production of Sema3A; Sema3A-positive sEVs compete with vascular endothelial growth factor A to bind to neuropilin-1. Therefore, MiVECs lose their ability to respond to angiogenesis. In conclusion, Sema3A is a key pathogenic mediator that impairs the angiogenic potential of MiVECs, which leads to cardiac microvascular rarefaction in pressure overload-induced heart disease.

Third trimester as the susceptibility window for maternal PM2.5 exposure and preterm birth: A nationwide surveillance-based association study in China.

Maternal PM2.5 exposure has been identified as a potential risk factor for preterm birth, yet the inconsistent findings on the susceptible exposure windows may be partially due to the influence of gaseous pollutants. This study aims to examine the association between PM2.5 exposure and preterm birth during different susceptible exposure windows after adjusting for exposure to gaseous pollutants. We collected 2,294,188 records of singleton live births from 30 provinces of China from 2013 to 2019, and the gridded daily concentrations of air pollutants (including PM2.5, O3, NO2, SO2, and CO) were derived by using machine learning models for assessing individual exposure. We employed logistic regression to develop single-pollutant models (including PM2.5 only) and co-pollutant models (including PM2.5 and a gaseous pollutant) to estimate the odds ratio for preterm birth and its subtypes, with adjustment for maternal age, neonatal sex, parity, meteorological conditions, and other potential confounders. In the single-pollutant models, PM2.5 exposure in each trimester was significantly associated with preterm birth, and the third trimester exposure showed a stronger association with very preterm birth than that with moderate to late preterm birth. The co-pollutant models revealed that preterm birth might be significantly associated only with maternal exposure to PM2.5 in the third trimester, and not with exposure in the first or second trimester. The observed significant associations between preterm birth and maternal PM2.5 exposure in the first and second trimesters in single-pollutant models might primarily be influenced by exposure to gaseous pollutants. Our study provides evidence that the third trimester may be the susceptible window for maternal PM2.5 exposure and preterm birth. The association between PM2.5 exposure and preterm birth could be influenced by gaseous pollutants, which should be taken into consideration when evaluating the impact of PM2.5 exposure on maternal and fetal health.

The Influence of Airborne Particulate Matter on the Risk of Gestational Diabetes Mellitus: A Large Retrospective Study in Chongqing, China.

Emerging research findings suggest that airborne particulate matter might be a risk factor for gestational diabetes mellitus (GDM). However, the concentration-response relationships and the susceptible time windows for different types of particulate matter may vary. In this retrospective analysis, we employ a novel robust approach to assess the crucial time windows regarding the prevalence of GDM and to distinguish the susceptibility of three GDM subtypes to air pollution exposure. This study included 16,303 pregnant women who received routine antenatal care in 2018-2021 at the Maternal and Child Health Hospital in Chongqing, China. In total, 2482 women (15.2%) were diagnosed with GDM. We assessed the individual daily average exposure to air pollution, including PM2.5, PM10, O3, NO2, SO2, and CO based on the volunteers' addresses. We used high-accuracy gridded air pollution data generated by machine learning models to assess particulate matter per maternal exposure levels. We further analyzed the association of pre-pregnancy, early, and mid-pregnancy exposure to environmental pollutants using a generalized additive model (GAM) and distributed lag nonlinear models (DLNMs) to analyze the association between exposure at specific gestational weeks and the risk of GDM. We observed that, during the first trimester, per IQR increases for PM10 and PM2.5 exposure were associated with increased GDM risk (PM10: OR = 1.19, 95%CI: 1.07~1.33; PM2.5: OR = 1.32, 95%CI: 1.15~1.50) and isolated post-load hyperglycemia (GDM-IPH) risk (PM10: OR = 1.23, 95%CI: 1.09~1.39; PM2.5: OR = 1.38, 95%CI: 1.18~1.61). Second-trimester O3 exposure was positively correlated with the associated risk of GDM, while pre-pregnancy and first-trimester exposure was negatively associated with the risk of GDM-IPH. Exposure to SO2 in the second trimester was negatively associated with the risk of GDM-IPH. However, there were no observed associations between NO2 and CO exposure and the risk of GDM and its subgroups. Our results suggest that maternal exposure to particulate matter during early pregnancy and exposure to O3 in the second trimester might increase the risk of GDM, and GDM-IPH is the susceptible GDM subtype to airborne particulate matter exposure.

Urinary polycyclic aromatic hydrocarbon metabolites are positively related to serum testosterone levels of males and serum estradiol levels of females among U.S. adults.

Background: It has been reported for several years that polycyclic aromatic hydrocarbons (PAHs) could disturb human endocrine function. However, there is still a short of consistent conclusion about the relationship between PAH exposure and levels of sexual hormones. The aim of our study is to explore whether exposure to PAHs and how PAHs affect the levels of serum testosterone (T) and estradiol (E2) in adults, hoping to fulfill the knowledge gap. Materials and methods: This study included adults aged 20 and above who participated in the National Health and Nutrition Examination Survey (NHANES) from 2011 to 2016. We included 10 PAH metabolites in this study. The levels of urinary PAH metabolites were log-transformed and divided into quartiles. The associations between PAH metabolites and both serum T levels of males and E2 levels of females were investigated using multivariate regression models. We furtherly calculated PAHs scores by sum of ranks across 10 PAHs metabolites, which represented the exposure levels of PAHs mixtures, and the association between PAHs scores and serum T and E2 levels were analyzed. Results: A total of 4,654 subjects were included in this study, including 2,460 males and 2,194 females. After adjusting for confounders, 2-hydroxynapthalene and 3-hydroxyfluorene were positively associated with serum T levels of males (p-value for trend=0.047, and p-value for trend=0.006, respectively), while 1-hydroxyphenanthrene was positively associated with serum E2 levels of females (p-value for trend=0.013). In the adjusted models, no significant association was found between PAHs scores and either T levels of males or E2 levels of females (p-value for trend=0.615, and p-value for trend=0.241, respectively). Conclusions: This study showed urinary 2-hydroxynapthalene and 3-hydroxyfluorene were associated with increased T levels of males, and urinary 1-hydroxyphenanthrene was associated with increased E2 levels of females. The observed association indicated disrupting effects of PAH exposure on reproductive health.

Methyltransferase like 3-mediated N6-methylatidin methylation inhibits vascular smooth muscle cells phenotype switching via promoting phosphatidylinositol 3-kinase mRNA decay.

N6-methylatidine (m6A) is involved in post-transcriptional metabolism and a variety of pathological processes. However, little is known about the role of m6A in vascular proliferative diseases, particularly in vascular smooth muscle cells (VSMCs) phenotype switching-induced neointimal hyperplasia. In the current study, we discovered that methyltransferase like 3 (METTL3) is a critical candidate for catalyzing a global increase in m6A in response to carotid artery injury and various VSMCs phenotype switching. The inhibited neointimal hyperplasia was obtained after in vivo gene transfer to knock-down Mettl3. In vitro overexpression of Mettl3 resulted in increased VSMC proliferation, migration, and reduced contractile gene expression with a global elevation of m6A modification. In contrast, Mettl3 knockdown reversed this facilitated phenotypic switch in VSMCs, as demonstrated by downregulated m6A, decreased proliferation, migration, and increased expression of contractile genes. Mechanistically, Mettl3 knock-down was found to promote higher phosphatidylinositol 3-kinase (Pi3k) mRNA decay thus inactivating the PI3K/AKT signal to inhibit VSMCs phenotype switching. Overall, our findings highlight the importance of METTL3-mediated m6A in VSMCs phenotype switching and offer a novel perspective on targeting METTL3 as a therapeutic option for VSMCs phenotype switching modulated pathogenesis, including atherosclerosis and restenosis.

CircERBB2IP promotes post-infarction revascularization via the miR-145a-5p/Smad5 axis.

Myocardial infarction is one of the leading diseases causing death and disability worldwide, and the revascularization of damaged tissues is essential for myocardial-injury repair. Circular RNAs (circRNAs) are widely involved in physiological and pathological processes in various systems throughout the body, and the role of circRNAs in cardiovascular disease is gaining attention. In this study, we determined that circERBB2IP is highly expressed in the hearts of newborn mice. Silencing or overexpression of circERBB2IP inhibited and promoted angiogenesis in vivo and in vitro, respectively. Mechanistically, the transcription factor GATA4 promotes the production of circERBB2IP. Furthermore, circERBB2IP functioned as an endogenous miR-145a-5p sponge and was able to sequester and repress miR-145a-5p activity, which led to an increased expression level of Smad5. In summary, circERBB2IP can promote angiogenesis after myocardial infarction through the miR-145a-5p/Smad5 axis. These data suggest that circERBB2IP may be a potential therapeutic target for the treatment of myocardial infarction.

Exosomal MiR-29a in Cardiomyocytes Induced by Angiotensin II Regulates Cardiac Microvascular Endothelial Cell Proliferation, Migration and Angiogenesis by Targeting VEGFA.

BACKGROUND: Exosomes released from cardiomyocytes (CMs) potentially play an important role in angiogenesis through microRNA (miR) delivery. Studies have reported an important role for miR-29a in regulating angiogenesis and pathological myocardial hypertrophy. However, whether CMderived exosomal miR-29a is involved in regulating cardiac microvascular endothelial cell (CMEC) homeostasis during myocardial hypertrophy has not been determined. METHODS: Angiotensin II (Ang II) was used to induce CM hypertrophy, and ultracentrifugation was then used to extract exosomes from a CM-conditioned medium. CMECs were cocultured with a conditioned medium in the presence or absence of exosomes derived from CMs (Nor-exos) or exosomes derived from angiotensin II-induced CMs (Ang II-exos). Moreover, a rescue experiment was performed using CMs or CMECs infected with miR-29a mimics or inhibitors. Tube formation assays, Transwell assays, and 5-ethynyl-20-deoxyuridine (EdU) assays were then performed to determine the changes in CMECs treated with exosomes. The miR-29a expression was measured by qRT-PCR, and Western blotting and flow cytometry assays were performed to evaluate the proliferation of CMECs. RESULTS: The results showed that Ang II-induced exosomal miR-29a inhibited the angiogenic ability, migratory function, and proliferation of CMECs. Subsequently, the downstream target gene of miR- 29a, namely, vascular endothelial growth factor (VEGFA), was detected by qRT-PCR and Western blotting, and the results verified that miR-29a targeted the inhibition of the VEGFA expression to subsequently inhibit the angiogenic ability of CMECs. CONCLUSION: Our results suggest that exosomes derived from Ang II-induced CMs are involved in regulating CMCE proliferation, migration, and angiogenesis by targeting VEGFA through the transfer of miR-29a to CMECs.

CircUbe3a from M2 macrophage-derived small extracellular vesicles mediates myocardial fibrosis after acute myocardial infarction.

Objective: This study aimed to explore the role of circular RNAs (circRNAs) in M2 macrophage (M2M)-derived small extracellular vesicles (SEVs) in myocardial fibrosis development. Methods: The regulatory role of M2M-derived extracellular vesicles (EVs) was evaluated in a mouse model of acute myocardial infarction. Immunofluorescence, quantitative real-time PCR (RT-qPCR), nanoparticle tracking analysis, Western blot analysis and electron microscopy were used to identify macrophages, large extracellular vesicles (LEVs) and SEVs. The circRNA expression profiles of M0 macrophages (M0Ms) and M2Ms were determined by microarray analysis. Bioinformatic analysis, cell coculture and cell proliferation assays were performed to investigate the expression, function, and regulatory mechanisms of circUbe3a in vitro. qPCR, RNA immunoprecipitation (RIP), dual-luciferase reporter assays, RNA fluorescence in situ hybridization (RNA-FISH), Western blot analysis and a series of rescue experiments were used to verify the correlation among circUbe3a, miR-138-5p and RhoC. Results: CircUbe3a from M2M-derived SEVs triggered functional changes in cardiac fibroblasts (CFs). CircUbe3a was synthesized and loaded into SEVs during increased M2M infiltration after myocardial infarction. The fusion of the released SEVs with the plasma membrane likely caused the release of circUbe3a into the cytosol of CFs. Silencing or overexpressing circUbe3a altered CF proliferation, migration, and phenotypic transformation in vitro. We confirmed that circUbe3a plays a crucial role in enhancing functional changes in CFs by sponging miR-138-5p and then translationally repressing RhoC in vitro. In vivo, the addition of M2M-derived SEVs or overexpression of circUbe3a significantly exacerbated myocardial fibrosis after acute myocardial infarction, and these effects were partially abolished by circUbe3a-specific shRNA. Conclusions: Our findings suggest that M2M-derived circUbe3a-containing SEVs promote the proliferation, migration, and phenotypic transformation of CFs by directly targeting the miR-138-5p/RhoC axis, which may also exacerbate myocardial fibrosis after acute myocardial infarction.

CircHIPK3 regulates the autophagy and apoptosis of hypoxia/reoxygenation-stimulated cardiomyocytes via the miR-20b-5p/ATG7 axis.

Autophagy and apoptosis are involved in myocardial ischemia/reperfusion (I/R) injury. Research indicates that circular RNA HIPK3 (circHIPK3) is crucial to cell autophagy and apoptosis in various cancer types. However, the role of circHIPK3 in the regulation of cardiomyocyte autophagy and apoptosis during I/R remains unknown. Our study aimed to examine the regulatory effect of circHIPK3 during myocardial I/R and investigate its mechanism in cardiomyocyte autophagy and apoptosis. Methods and results. The expression of circHIPK3 was upregulated during myocardial I/R injury and hypoxia/reoxygenation (H/R) injury of cardiomyocytes. To study the potential role of circHIPK3 in myocardial H/R injury, we performed gain-of-function and loss-of-function analyses of circHIPK3 in cardiomyocytes. Overexpression of circHIPK3 significantly promoted H/R-induced cardiomyocyte autophagy and cell injury (increased intracellular reactive oxygen species (ROS) and apoptosis) compared to those in the control group, while silencing of circHIPK3 showed the opposite effect. Further research found that circHIPK3 acted as an endogenous miR-20b-5p sponge to sequester and inhibit miR-20b-5p activity, resulting in increased ATG7 expression. In addition, miR-20b-5p inhibitors reversed the decrease in ATG7 induced by silencing circHIPK3. Conclusions. CircHIPK3 can accelerate cardiomyocyte autophagy and apoptosis during myocardial I/R injury through the miR-20b-5p/ATG7 axis. These data suggest that circHIPK3 may serve as a potential therapeutic target for I/R.

Hypoxia-reoxygenation induces macrophage polarization and causes the release of exosomal miR-29a to mediate cardiomyocyte pyroptosis.

To investigate the mechanism by which hypoxia-reoxygenation (HR) mediates macrophage polarization to the M1 phenotype and then mediates cardiomyocyte (CM) pyroptosis through exosome release. Mouse bone marrow macrophages and CMs were cultured in vitro under hypoxia for 12 h and reoxygenation for 6 h to establish an HR cell model. qPCR was used to detect the M1 or M2 macrophage markers IL-1ß, TNF-α, MR, and Arg, and a macrophage and CM coculture system was then established. Macrophages were transfected with an exosome-CD63-red fluorescent protein (RFP) lentivirus, allowing secretion of exosomes expressing RFP, and GW4869 was used to inhibit exosome release by macrophages. qPCR detected miR-29 expression in macrophage-derived exosomes, and macrophages were transfected with miR-29a inhibitors to obtain exosomes with low miR-29a expression (siR-exos). Pyroptosis indicators were detected by Western blot and ELISA. Importantly, LPS induced bone marrow macrophage polarization to the M1 type as a positive control to further verify that these exosomes (LPS-exos) regulated CM pyroptosis by delivering miR29a. Dual luciferase reporter and Western blot assays were adopted to analyze the miR-29a and MCL-1 target relationship. In addition, MCL-1 overexpression was used as a rescue experiment to determine whether miR-29a regulates pyroptosis in CM by targeting MCL-1. Macrophages expressed the M1 macrophage markers IL-1ß and TNF-α after HR exposure. After CM coculture, RFP expression was significantly higher in the HR group than in the normal (Nor) group but significantly reduced in the GW4869 group. Immunofluorescence showed that caspase-1 mRNA and protein expression in the HR group was significantly higher than that in the Nor group (P < 0.05). Caspase-1 expression was significantly decreased in the GW4869 group compared with the HR group (P < 0.05). Western blotting showed that the pyrolysis-related NLRP3 and ASC protein expression levels were significantly upregulated in the HR group compared with the control (Ctr) and Nor groups (P < 0.05). However, GW4869 effectively inhibited pyroptosis-related protein expression (P < 0.05). In addition, ELISA showed that the expression of the inflammation indicators IL-1ß and IL-18 was significantly increased in the HR group compared to the Ctr group (P < 0.05) but decreased in the GW4869 group (P < 0.05). qPCR showed that miR-29a was upregulated in the HR group compared to the Nor group. Moreover, HR-induced exosomes (HR-exos) from macrophages exacerbated HR-induced CM pyroptosis, while inhibition of miR-29a in exosomes partially offset CM pyroptosis induction. LPS-exos promoted pyroptosis-related protein expression, as the IL-1ß and IL-18 concentrations were increased in the LPS-exos group. However, pyroptosis-related proteins were observably decreased, and IL-1ß and IL-18 were also significantly decreased after miR-29a inhibition when compared with that in the HR-exos and LPS-exos groups. Mcl-1 overexpression reversed miR-29a-mediated CM pyroptosis in an HR environment. HR treatment induced macrophage polarization towards the M1 phenotype, which mediated CM pyroptosis through exosomal miR-29a transfer by targeting MCL-1.

CircHIPK3 regulates cardiac fibroblast proliferation, migration and phenotypic switching through the miR-152-3p/TGF-ß2 axis under hypoxia.

BACKGROUND: The occurrence of pathological cardiac fibrosis is attributed to tissue hypoxia. Circular RNAs play significant regulatory roles in multiple cardiovascular diseases and are involved in the regulation of physiological and pathophysiological processes. CircHIPK3 has been identified as the one of the most crucial regulators in cardiac fibrosis. However, the mechanisms by which circHIPK3 regulates cardiac fibrosis under hypoxia remain unclear. Our study aimed to determine circHIPK3 expression in cardiac fibroblasts (CFs) and investigate the functions of circHIPK3 in hypoxia environment. METHODS: The expression level of circHIPK3 in CFs under hypoxia (1% O2) was analyzed by qRT-PCR. The role of circHIPK3 on the proliferation and migration of CFs were determined by EdU, cell wound scratch assay and cell cycle. The expression of proteins associated with phenotypic transformation in CFs in vitro was examined by immunofluorescence assay and western blot. Bioinformatics analysis, dual luciferase activity assay and RNA fluorescent in situ hybridization assay revealed that miR-152-3p was identified as a target of circHIPK3 and that TGF-ß2 was targeted by miR-152-3p. RESULTS: CircHIPK3 expression was significantly upregulated in CFs in a hypoxic environment. In vitro, overexpressing circHIPK3 obviously promoted CF proliferation, migration and phenotypic changes under hypoxia, but those processes were suppressed by circHIPK3 silencing. CircHIPK3 acted as an endogenous miR-152-3p sponge and miR-152-3p aggravated circHIPK3 silencing induced inhibition of CF proliferation, migration, phenotypic transformation and TGF-ß2 expression in vitro. In summary, circHIPK3 plays a pivotal role in the development of cardiac fibrosis by targeting the miR-152-3p/TGF-ß2 axis. CONCLUSIONS: These findings demonstrated that circHIPK3 acted as a miR-152-3p sponge to regulate CF proliferation, migration and phenotypic transformation through TGF-ß2, revealing that modulation of circHIPK3 expression may represent a potential target to promote the transition of hypoxia-induced CFs to myofibroblasts.