Chronic kidney disease (CKD) affects millions worldwide and frequently progresses to end-stage renal disease, requiring dialysis or transplantation. Renal interstitial fibrosis (RIF) characterized by excessive extracellular matrix (ECM) deposition and loss of functional parenchyma is the final common pathway underlying CKD progression, regardless of the initial etiology [1]. RIF disrupts renal architecture through fibroblast activation and ECM accumulation, leading to impaired glomerular filtration and tubular function [2]. Given its irreversible nature and central role in CKD, halting or reversing RIF has become a critical focus in nephrology research.

Myofibroblast activation is a pivotal event in RIF pathogenesis [3]. These specialized cells, characterized by the expression of alpha-smooth muscle actin ($\alpha$-SMA) and fibronectin (FN), are the primary source of pathological ECM [4]. Both markers correlate strongly with the onset and severity of renal fibrosis. Myofibroblasts are highly responsive to transforming growth factor beta 1 (TGF-$\beta$1), a master regulator of their differentiation and ECM production [5]. Upon TGF-$\beta$1 stimulation, they proliferate and secrete abundant ECM components particularly collagen I and FN which accumulate in the tubulointerstitium, replacing normal parenchyma [6]. This fibrotic deposition not only compromises kidney function but also fosters a pro-fibrotic microenvironment that perpetuates myofibroblast activation and disease progression [7].

The unilateral ureteral obstruction (UUO) mouse model is a well-established and widely used experimental system in nephrology research [8]. It rapidly induces renal fibrosis, inflammatory cell infiltration, oxidative stress, and ECM accumulation in the kidney, providing a reproducible platform for evaluating antifibrotic interventions [9, 10]. Although UUO does not fully recapitulate the slow progression of human CKD, it reliably models key aspects of fibrogenesis relevant to multiple CKD etiologies.

Scutellarin, a bioactive flavonoid derived from the traditional Chinese medicinal herb Erigeron breviscapus, has attracted considerable attention in recent years due to its diverse pharmacological properties. Initially recognized for its cardiovascular benefits, including enhancing cardiac function and exerting antithrombotic effects [11], scutellarin has since been shown to possess a wide range of therapeutic activities in various preclinical models. Studies have demonstrated its anti-inflammatory [12, 13], antioxidative [14, 15], and antiapoptotic [16] effects, which contribute to its protective role in multiple disease states. In the context of fibrosis, scutellarin has shown promising results in ameliorating pulmonary fibrosis [17]. It achieves this by reducing collagen deposition in lung tissues and inhibiting the expression of inflammatory factors such as NLR family pyrin domain containing 3 (NLRP3), interleukin 1$\beta$ (IL-1$\beta$), and Interleukin-18 (IL-18) [18]. These inflammatory mediators play crucial roles in promoting the epithelial mesenchymal transition (EMT), a process by which epithelial cells acquire a mesenchymal phenotype and contribute to fibrosis development [19]. Moreover, scutellarin has been shown to suppress $\alpha$-SMA expression in a diabetic nephropathy mouse model [20], suggesting its potential in mitigating renal fibrosis through the inhibition of myofibroblast activation, however, its effects on fibrosis in the context of obstructive nephropathy remain unclear.

Based on this evidence, we hypothesized that scutellarin may attenuate renal fibrosis and dysfunction in the UUO model. Consequently, we investigated its effects on functional parameters, histological fibrosis, and the expression of key ECM and fibroblast activation markers.

In this study, we demonstrated that scutellarin, a major active ingredient derived from the traditional Chinese herb Erigeron breviscapus—exerts potent antifibrotic effects on an UUO-induced mouse model of chronic tubulointerstitial fibrosis. Treatment with scutellarin significantly improved kidney function, as reflected by reductions in proteinuria, BUN, and Scr. Histologically, this was accompanied by decreased interstitial collagen deposition, confirmed by both IHC quantification of collagen I (%) and Western blot analysis showing downregulation of collagen I, FN, and $\alpha$-SMA—three canonical markers of ECM accumulation and myofibroblast activation. These findings align with prior reports of scutellarin-containing formulations improving proteinuria and renal parameters in patients with diabetic kidney disease, suggesting potential translational relevance, although direct clinical validation in fibrotic CKD remains to be established.

The coordinated suppression of $\alpha$-SMA, FN, and collagen I strongly indicates that scutellarin reduces the expression of markers associated with myofibroblast activation, which are primary cellular effectors of ECM overproduction in tubulointerstitial fibrosis. While our study did not directly assess upstream signaling events, this pattern of marker reduction is highly consistent with inhibition of the TGF-$\beta$1-driven fibrogenic program, a well-established axis in renal fibrosis. TGF-$\beta$1 potently induces the expression of $\alpha$-SMA, FN, and collagen I in renal fibroblasts and promotes EMT-like processes that contribute to myofibroblast pools [21]. Notably, earlier studies demonstrated that scutellarin suppresses TGF-$\beta$1 signaling and ameliorates fibrosis in models of diabetic nephropathy and pulmonary injury, with concomitant downregulation of these same markers [17, 20]. Thus, although direct measurement of TGF-$\beta$1 or Smad phosphorylation was not performed here, the concordance between our molecular findings and established TGF-$\beta$1 dependent responses provides a plausible and literature-supported mechanistic framework for scutellarin’s antifibrotic action.

This multimodal activity places scutellarin within a broader class of natural compounds derived from traditional Chinese medicine that target renal fibrosis through shared and distinct mechanisms. For instance, baicalin (from Scutellaria baicalensis) [22, 23] and curcumin (derived from Curcuma longa) [24, 25] also suppress TGF-$\beta$1/Smad signaling and EMT, while concurrently activating the nuclear factor erythroid 2-related factor 2 antioxidant pathway to mitigate oxidative stress-driven fibrogenesis. Similarly, tanshinone IIA (derived from Salvia miltiorrhiza) [26, 27] inhibits TGF-$\beta$1 and NLRP3 inflammasome activation—matching the anti-inflammatory effects in other organs—while also specifically promoting apoptosis in activated myofibroblasts, a mechanism not yet documented for scutellarin. Meanwhile, notoginsenoside R1 (derived from Panax notoginseng) [28] improves renal function and reduces fibrotic markers by inhibiting TGF-$\beta$1, closely mirroring the functional and molecular outcomes observed in our study. Together, these agents highlight a shared therapeutic strategy: targeting the TGF-$\beta$1-EMT-ECM axis while simultaneously ancillary drivers such as inflammation and redox imbalance. Scutellarin distinguishes itself not necessarily by a unique mechanism but by its established clinical use in microvascular complications and favorable safety profile, which may accelerate its repurposing for CKD.

It is important to acknowledge that scutellarin possesses documented anti-inflammatory and antioxidant properties in other organ systems [10, 14, 15, 18], and given that inflammation and oxidative stress can amplify fibrogenic signaling in the obstructed kidney, such ancillary effects may indirectly contribute to the observed benefit. Since direct measurements of redox status, inflammatory cytokines, or inflammasome components were not conducted in our model, the involvement of these pathways is speculative and warrants future investigation.

Unlike current standard-of-care agents (e.g., angiotensin-converting enzyme inhibitors or angiotensin receptor blockers) that primarily modulate hemodynamics to slow rather than reverse fibrosis [29, 30, 31], scutellarin therapeutically targets key structural components of the fibrotic response, evidenced by decreased collagen I deposition and reduced myofibroblast marker expression.

This study has several limitations that should be acknowledged. First, while the observed downregulation of $\alpha$-SMA, FN, and collagen I strongly suggests an attenuation of myofibroblast activity, the precise cellular origin of this effect—whether from the inhibition of resident fibroblast activation, EMT, or other cellular sources—remains undetermined due to the lack of lineage tracing or additional specific phenotypic markers. Second, the current experimental design, which administered scutellarin both before and after UUO surgery, does not allow us to distinguish whether the compound prevents the initial development of fibrosis or reverses established fibrotic lesions; this distinction is critical for its potential clinical application. Third, although the UUO model is a well-established tool for studying rapid fibrogenesis, it does not fully recapitulate the complex and slow progression of human CKD. Therefore, the translational relevance of these findings requires further validation in models that better mimic common human CKD etiologies, such as diabetic or hypertensive nephropathy, and ultimately in controlled clinical trials to confirm efficacy and establish optimal dosing regimens.

Despite the limitations acknowledged above, Our findings demonstrate that scutellarin attenuates RIF and improves functional parameters in the UUO mouse model, associated with reduced expression of collagen I, $\alpha$-SMA, and fibronectin. These results support further preclinical evaluation of scutellarin as an antifibrotic agent in kidney disease. Future studies should investigate its effects on additional models that better reflect human CKD pathophysiology, such as diabetic or hypertensive nephropathy, and elucidate the underlying molecular mechanisms, including potential modulation of TGF-$\beta$1 signaling. Comprehensive pharmacokinetic and toxicological assessments are required before clinical application. However, because targeting renal fibrosis remains a critical therapeutic goal, natural compounds such as scutellarin represent potential adjunctive therapies for progressive kidney disease.

The datasets used in the current study are available from the corresponding author upon reasonable request.

LG designed the research and contributed to manuscript writing. LG, ZZ, QL and DC performed the research and conducted experiments. LG, DC, CC and ZZ performed data analysis. TY, YW, RC participated in research design, data collection and analysis, interpretation of results, and manuscript writing. All authors contributed to editorial changes in the manuscript. All authors read and approved the final manuscript. All authors have participated sufficiently in the work and agreed to be accountable for all aspects of the work.

The Institutional Animal Ethics Committee of Qujing University of Medicine & Health Sciences approved (No. DL2025003) and conducted the study according to the Regulations on the Administration of Laboratory Animals (State Council of China), the Guiding Opinions on the Humane Treatment of Laboratory Animals (MOST, 2006), the Guidelines for Ethical Review of Laboratory Animal Welfare (GB/T 35892-2018), and the ARRIVE 2.0 guidelines.

Not applicable.

This research was supported by the following grants: (1) the 2025 Science Research Project of Yunnan Provincial Department of Education, “Research of Scutellarin by Inhibiting NLRP3 Inflammasome to Delay Pyroptosis of Diabetic Nephropathy Podocytes” (2025J1657); and (2) the Applied Basic Research Joint Special Funds of Chinese Medicine from Yunnan Provincial Science and Technology Department (202401AZ070001-097).

The authors declare no conflicts of interest.