Platelet-Rich Plasma (PRP) bidirectionally modulates scar formation via the Piezo1-YAP/TAZ axis: a novel mechanotransduction hypothesis

Platelet-Rich Plasma (PRP), a core biotherapeutic material in regenerative medicine, exhibits unique advantages in wound healing and tissue regeneration owing to its high concentrations of platelets and diverse bioactive factors, including albumin, fibrinogen, globulins, and growth factors such as Transforming growth factor-β1 (TGF-β1), Platelet-derived growth factor (PDGF), and Vascular endothelial growth factor (VEGF) [1]. However, the paradoxical bidirectional regulatory effects observed in its clinical application have garnered increasing attention: while PRP accelerates wound healing by promoting cell proliferation, angiogenesis, and ordered collagen deposition, it may also induce hypertrophic scars or even keloids due to excessive fibroblast activation and dysregulated extracellular matrix (ECM) metabolism [2,3]. This bidirectional effect underscores an urgent unmet clinical need: the lack of mechanistic understanding of PRP's scar-modulating pathways has prevented the development of precision strategies to maximize its therapeutic potential while mitigating fibrotic risks. Current research remains limited to broad biochemical signaling or generic ECM remodeling [4,5], with no focus on the mechanotransduction networks that bridge PRP's biological and physical effects on scar tissue.Recent advances in mechanotransduction research have shown that cellular sensing and response to matrix mechanical cues (e.g., stiffness, tension) are critical regulators of ECM metabolism and scar fate. Among these, Piezo1-the first identified mechanosensitive cation channel in eukaryotes (non-selective, permeable to Na⁺, Ca²⁺, and other ions) [6,7]-is overexpressed in scar tissue, responds to mechanical stretch, and drives fibroblast activation and hypertrophic scar formation [8,9]. The interplay between its activation and YAP/TAZ nuclear translocation serves as the central mechanism by which mechanical and certain chemical signals influence scar outcomes [10][11][12]. In skin fibrosis, Piezo1 forms a positive feedback loop by sensing tissue stiffness: its upregulation promotes a fibroblast proliferative phenotype, whereas Piezo1-knockout fibroblasts lose their fibrotic traits even on high-stiffness substrates [13,14]. Piezo1-YAP/TAZ is consistently implicated in scar pathogenesis: Piezo1 is overexpressed in hypertrophic scar/keloid fibroblasts and YAP/TAZ nuclear translocation directly promotes fibroblast activation and ECM deposition [8,9,12]. No other pathway has been shown to integrate PRP's dual biochemical-mechanical actions, making it the most relevant and translatable target for optimizing PRP therapy. Beyond skin, Piezo1 has been implicated in pulmonary fibrosis [15], cardiac fibrosis [16], and liver fibrosis [17], suggesting its broader role in mechanotransduction-driven fibrotic diseases. However, its mechanistic contribution may vary across organs and contexts.Previous studies have suggested that PRP may activate or synergize with the Piezo1 channel via its abundant growth factors and potential lipid components, concurrently triggering critical Ca²⁺ signaling cascades that drive angiogenesis, cell proliferation, differentiation, and matrix remodeling-ultimately promoting the regeneration of damaged myocardial tissue [18]. Regarding whether PRP can directly activate the Piezo1 channel, current evidence lacks direct experimental validation; however, indirect correlations and theoretical support have been proposed: the platelet plasma membrane in PRP may supply phosphatidylinositol bisphosphate (PIP₂), a lipid molecule recognized as a co-factor for Piezo1 channel activation [18][19][20][21].Despite the well-established pro-regenerative effects of PRP, a critical knowledge gap persists in understanding whether PRP modulates fibroblast behavior and scar progression through the Piezo1-mediated mechanotransduction pathway. Based on our understanding of PRP's active components, Piezo1's functional roles (mechanosensing and pro-fibrotic activity), and their established regulatory crosstalk, we propose the following plausible hypothesis: PRP bidirectionally regulates scar formation by activating the Piezo1 channel on fibroblast surfaces, thereby modulating fibroblast proliferation, differentiation, and ECM metabolism. This framework not only clarifies PRP's molecular mechanism of action but also provides a targeted strategy to optimize clinical outcomes (e.g., Piezo1 inhibitors, injection parameter tuning), filling the unmet need for precision anti-scar therapies.We propose that PRP bidirectionally modulates fibroblast function and scar progression by targeting the Piezo1-YAP/TAZ mechanotransduction axis via multidimensional biological effects (Figure 1.). During physiological repair, this modulation attenuates scar formation; during pathological fibrosis, it promotes the development of hypertrophic scars or keloids. We further hypothesize that PRP regulates the Piezo1 channel through the following mechanisms:2.1 TGF-β1 secreted by PRP upregulates Piezo1 expression/activity, and the two interact via positive/negative feedback loops to modulate scar formation [22][23][24][25].2.2 PRP alters tissue mechanical properties (e.g., stiffness) by inducing cell proliferation and matrix remodeling. Changes in the stiffness of its contained fibrin matrix further tune the tension of the tissue mechanical microenvironment, thereby regulating Piezo1 channel activity.The platelet plasma membrane in PRP may supply phosphatidylinositol bisphosphate (PIP₂)-a lipid molecule known to activate the Piezo1 channel [18][19][20][21].During PRP injection therapy, mechanical force from the injection directly activates the Piezo1 channel. PRP injection may also activate mechanosensitive Piezo1 channels by locally increasing tissue tension.The core pathological process of hypertrophic scarring (e.g., in skin wounds and visceral organs like the lung or liver) involves excessive fibroblast activation driven by dysregulated mechanotransduction pathways [26] and aberrant ECM deposition orchestrated by profibrotic signaling hubs such as YAP/TAZ in pulmonary fibrosis [27].As a mechanosensitive ion channel, Piezo1 primarily regulates cellular functions (e.g., fibroblast proliferation, collagen secretion) by sensing extracellular mechanical cues (e.g., tissue tension, matrix stiffnes) or indirectly via growth factor signaling [13,14].These functions exhibit bidirectional roles in physiological repair and pathological fibrosis-findings that strongly support the feasibility of targeting Piezo1 for scar therapy. Piezo1 activation in physiological tissue repair occurs through physiological mechanical cues (e.g., wound-edge contraction, collagen matrix remodeling) and regulated growth factor signaling. Moderate Piezo1 activation, as part of fibroblast functional regulation, facilitates normal tissue healing and reduces scar overgrowth [12,28]. In contrast, pathological fibrosis arises from a synergistic interplay between Piezo1 hyperactivation (triggered by persistent mechanical stretch or excess profibrotic factors) and other pathological elements (e.g., chronic inflammation, aberrant ECM deposition). Activated Piezo1 further amplifies TGF-β1-downstream profibrotic signals via calcium signaling (forming a positive feedback loop) and activates pathways like YAP/TAZ. This drives uncontrolled fibroblast proliferation and excessive ECM deposition, potentially promoting hypertrophic scar or keloid formation [13,29].The biological effects of PRP depend primarily on bioactive molecules released upon platelet activation: beyond growth factors, these include the fibrin scaffold formed postactivation. This scaffold not only provides physical support for cell migration/adhesion but also modulates cell behavior via mechanical properties (e.g., matrix stiffness) [30].Based on current mechanistic insights, PRP bidirectionally regulates fibroblast function and scar progression by targeting the Piezo1-YAP/TAZ mechanotransduction axis via multidimensional effects. Below, we elucidate the underlying mechanisms:As a platelet-enriched reservoir of bioactive factors, PRP's key effector-TGF-β1)is initially present as a latent complex (latent TGF-β1, L-TGF-β1) embedded in the ECM [31]. In fibrotic contexts, fibroblast contractions (amplified by matrix stiffness and Piezo1-mediated mechanosignaling) drive ECM remodeling to release and activate L-TGF-β1 [32]. Activated TGF-β1 then regulates Piezo1 mRNA transcription and membrane protein expression via the classical Smad-dependent pathway (Smad2/3 phosphorylation) and non-classical MAPK/YAP pathway [23,[33][34][35]. Notably, Piezo1 activation mediates calcium (Ca²⁺) influx, which, via calmodulin-dependent kinase II (CaMKⅡ), phosphorylates TGF-β1 receptor I (TβRⅠ). This enhances downstream TGF-β1-Smad signaling, forming a "TGF-β1↑→Piezo1↑→amplified TGF-β1 signaling" positive feedback loop [13,23]. During physiological repair, this loop maintains ECM homeostasis (synthesis vs. degradation) and limits scar formation. However, in pathological fibrosis, the loop is markedly amplified: In hypertrophic scars, elevated matrix stiffness exacerbates fibrosis via the Piezo1-Wnt2/Wnt11-CCL24 inflammatory pathway-while increased stiffness further upregulates Piezo1, creating a "stiffness↑→Piezo1↑→fibrosis↑" vicious cycle [13]. Mechanically activated Piezo1-YAP signaling upregulates factors like CCN1/CCN2, driving fibroblast proliferation and collagen deposition to strengthen pro-fibrotic loops.A similar mechanism operates in pulmonary fibrosis, where TGF-β1/Smad synergizes with molecules like SULF1/NEU3 to promote ECM deposition [15,36]. For targeted intervention, inhibiting Piezo1 (e.g., with the inhibitor OB-1) blocks TGF-β1 signaling, reduces aberrant collagen deposition, and disrupts the fibrotic loop [23]. Conversely, moderate Piezo1 activation during physiological repair is critical for cell migration and angiogenesis-its depletion causes epithelial barrier dysfunction [37].In summary, the Piezo1-TGF-β1 positive feedback loop is a core node in fibrosis progression. Its dynamic balance dictates whether tissue repair adopts a physiological (scar-minimizing) or pathological (fibrotic/hypertrophic) trajectory. This framework not only explains PRP's dual effects on scar formation but also identifies Piezo1 as a precision target for optimizing PRP-based therapies-e.g., balancing its proregenerative and pro-fibrotic activities via mechanistic modulation.The fibrin matrix in PRP modulates porosity and elastic modulus, which may influence cell migration and angiogenesis [13,14]. For instance, combining PRP with microvascular fragments (MVF) accelerates wound healing and markedly boosts neovascular density [38,39]. In this therapeutic context, MVF synergize with PRP to enhance neovascularization in chronic wounds by integrating into existing vasculature and stimulating capillary formation, while also improving tissue perfusion and nutrient delivery [39]. Together, these actions foster an optimal microenvironment that reduces scar formation. PRP-induced fibroblast proliferation and ECM remodeling significantly alter the local mechanical microenvironment of tissues. On one hand, PRP promotes fibroblast secretion of ECM components (e.g., collagen, fibronectin) to increase substrate stiffness; on the other hand, PRP inhibits ECM deposition by regulating fibroblast function [40]. Additionally, the fibrin matrix in PRP-by modulating porosity and elastic modulus-may influence cell migration and angiogenesis [41,42]. For example, PRP combined with MVF accelerates wound healing and boosts neovascular density [43]. As a mechanosensitive ion channel, the open probability of Piezo1 highly depends on ECM physical properties: elevated matrix stiffness triggers Piezo1 conformational rearrangement, enhancing interactions between its intracellular domains and ankyrin/vimentin. This promotes Ca²⁺ influx and activates downstream YAP/TAZ signaling, driving scar formation [44]. Conversely, during physiological repair, moderate matrix remodeling induced by PRP limits Piezo1 overactivation, suppresses YAP/TAZ nuclear translocation, and maintains fibroblast quiescence while facilitating ECM degradation [12]. Notably, YAP/TAZ nuclear localization correlates positively with stiffness in 2D cultures but may show inverse/nonlinear relationships in 3D environments [45]; its regulation is context-dependent (e.g., dimensionality, cell type) and involves crosstalk with pathways (e.g., Hippo, Wnt). Targeting this axis (e.g., Piezo1 genetic knockdown/knockout [37,46], GsMTx4-mediated Piezo1 inhibition [47], or YAP inhibitors) holds therapeutic promise for fibrosis and cancer, though tissue specificity remains essential to preserve physiological repair.Piezo1 expression is significantly higher in fibroblasts from pathological scars (e.g., hypertrophic scars, keloids) versus normal skin, and it positively correlates with YAP signaling. The Piezo1-YAP pathway is effectively inhibited by the Piezo1 inhibitor GsMTx4 [47]. Piezo1 responds to mechanical forces in a threshold-dependent manner (typically requiring >25mN/m membrane tension) [48]. The hypothesis that PRP bidirectionally modulates scar formation by targeting the Piezo1-YAP/TAZ mechanotransduction axis via multidimensional biological effects reveals the synergism of biochemical factors, tissue mechanics, and cellular mechanotransduction in wound repair-offering critical insights for both basic research and clinical translation:TGF-β1 in PRP not only directly drives fibroblast proliferation and collagen deposition but also upregulates Piezo1 expression via Smad2/3-mediated transcriptional activation: phosphorylated Smad2/3 binds to the Piezo1 gene promoter to induce its transcription [34]. Activated Piezo1, in turn, amplifies TGF-β1 downstream signaling through calcium influx, forming a positive feedback loop: TGF-β1↑ → Piezo1↑ → amplified TGF-β1 signaling. This mechanism explains the self-reinforcing cycle of "excessive ECM deposition-fibrosis progression" in pathological scars (e.g., hypertrophic scars) due to uncontrolled positive feedback. It also clarifies the pivotal role of moderate feedback activation (maintaining ECM homeostasis) in physiological repairproviding a novel perspective for understanding organ fibrosis (e.g., lung, liver). This highlights that the anti-fibrotic and pro-regenerative effects of PRP on scar tissue arise not only from its constituent growth factors (e.g., TGF-β1, PDGF) but also from its ability to remodel the ECM-including driving collagen cross-linking and fibrin network assembly-to dynamically alter tissue biomechanical stiffness. Such matrix stiffness changes directly modulate the open probability of Piezo1 mechanosensitive channels in resident fibroblasts: pathologically stiff scar matrices excessively activate the Piezo1-YAP/TAZ mechanotransduction axis to promote persistent fibrosis and pathological scar formation, whereas physiologically moderate matrix stiffness restricts Piezo1 overactivation and maintains fibroblast phenotypic homeostasis. Collectively, these findings indicate that future scar therapeutic strategies could be optimized by combining PRP with matrix-softening agents (e.g., lysyl oxidase (LOX) inhibitors [50]) or by fine-tuning PRP-induced matrix remodeling (e.g., via controlled fibrin concentration) to normalize tissue stiffness and Piezo1 activation, thereby maximizing therapeutic efficacy while mitigating excessive fibrosis.The direct activation of Piezo1 by mechanical forces from PRP injection links clinical procedures (e.g., injection force, frequency) to underlying mechanisms. Transient mechanical forces during injection-such as shear stress and pressure gradients-can directly trigger Piezo1 channel opening. For example: High-concentration/rapid injection may cause excessive Piezo1-YAP/TAZ activation (exacerbating fibrosis) due to overstimulation [51]; Low-dose/slow injection avoids excessive mechanical cues (promoting physiological repair). This provides a rationale for optimizing clinical PRP protocols: injection parameters (e.g., needle gauge, single-dose volume) should be tailored to scar type (hypertrophic/atrophic). Additionally, mechanical modulation techniques (e.g., combined ultrasound/acoustic radiation force) can precisely regulate Piezo1 activity.Based on this hypothesis, future scar treatment must shift from a "one-size-fits-all" approach to a personalized, mechanism-driven model: Stratify patients into "high fibrosis risk" or "delayed healing" subgroups using biomarkers (e.g., Piezo1 expression, matrix stiffness, TGF-β1 levels); Tailor PRP concentration, injection frequency, or combination therapies (e.g., with anti-fibrotic agents) to subgroup needs; Monitor changes in the mechanical microenvironment during treatment (via advanced imaging/sensors) to dynamically optimize protocols.In summary, this hypothesis not only deepens the mechanistic understanding of PRPmediated scar modulation, with Piezo1 identified as a key mechanosensitive effector [52] and potential therapeutic target for anti-fibrotic scar therapy, but also provides a robust theoretical framework for developing next-generation scar therapies that integrate biochemical, mechanical and clinical parameters.To systematically validate the hypothesis, a hierarchical experimental strategy can be designed, integrating in vitro mechanistic dissection, in vivo model testing, and multipathway synergistic blockade-centered on three core mechanisms: the TGF-β1-Piezo1 positive feedback loop, matrix mechanical regulation, and direct activation by PRP injection forces (Table 1).For the TGF-β1-Piezo1 positive feedback loop, in vitro studies can employ human skin fibroblasts (HSFs) stimulated with PRP (containing endogenous TGF-β1). TGF-β1 concentration changes can first be quantified via ELISA, while Piezo1 mRNA/protein expression can be analyzed using qPCR and Western blot (WB) to explore their correlation. To confirm the TGF-β1→Piezo1 axis, TGF-β1 can be neutralized with antibodies or its receptor I (TβRⅠ) can be knocked down via siRNA; reduced Piezo1 expression can validate upstream control. Calcium imaging can monitor Ca²⁺ influx upon Piezo1 activation, while Smad2/3 phosphorylation assays can indirectly link Piezo1 function to TGF-β signaling [53,54]. In vivo, a mouse scar model can be generated, with groups receiving PRP alone or PRP plus TGF-β1 neutralizing antibody.Immunofluorescence co-localization can assess Piezo1/TGF-β1 subcellular distribution, and WB for YAP nuclear translocation (a mechanotransduction hallmark) can test whether this feedback drives fibrosis [12,47,55,56].To evaluate matrix mechanical regulation, in vitro experiments can use collagen gels with stiffness gradients to mimic physiological/pathological microenvironments. HSFs co-cultured with PRP on these gels can be analyzed via atomic force microscopy (AFM) to quantify local matrix stiffness changes in the pericellular microenvironment surrounding individual fibroblasts (rather than bulk/overall stiffness of the gel), as AFM enables high-resolution nanomechanical mapping of pericellular matrix stiffness with spatial precision the Calcium imaging be to monitor Piezo1 channel in response to these mechanical cues (WB) to assess nuclear translocation of YAP (a downstream effector of Piezo1 test matrix stiffness via can be with a lysyl oxidase (LOX) inhibitor stiffness by collagen and changes in Piezo1 and YAP translocation can be In vivo, mouse scars can be AFM can tissue stiffness, can quantify collagen density and to fibrosis and can evaluate co-localization studies can elucidate Piezo1 matrix stiffness to activate YAP signaling, driving direct activation by injection mechanical force, in vitro experiments can PRP injection using a pressure combined with tension and cell for force control. conformational imaging can be to Piezo1 channel the on Piezo1's mechanosensitive upon channel is from that only Piezo1 protein with no between and open Calcium imaging can Ca²⁺ influx, and can confirm Piezo1 as the key this mechanotransduction response In vivo, PRP can mechanical WB can Piezo1 membrane and can collagen deposition to link membrane tension to a positive between force and combined in vitro inhibitors, and in vivo combination therapies can validate that these three pathways synergize via a remodeling force to regulate the Piezo1-YAP this hypothesis can a novel framework for PRP beyond to interplay between biochemical matrix mechanics, and mechanical can optimize PRP clinical use (e.g., injection combining with Piezo1 inhibitors) and can a theoretical for precision scar targeting the Piezo1-YAP is in regenerative for its ability to enhance tissue repair, its molecular effects on scar formation research underscores the of mechanosensitive the Piezo1 ion channel and the YAP/TAZ signaling wound healing and scar tissue, Piezo1 functions as a of mechanical with other pathways to fibrotic [8,9]. The bidirectional regulation hypothesis of PRP in scar it suppresses scarring during physiological repair and promotes fibrosis in pathological a novel to its biological effects. its this mechanism on targeting the Piezo1-YAP/TAZ axis via multidimensional signals factors, matrix mechanics, and mechanical with aberrant activation of this axis recognized as a key of The Piezo1-YAP/TAZ axis is not as the mechanism but as the that PRP's multidimensional effects and other pathways (e.g., that primarily biochemical Piezo1-YAP/TAZ both factors and mechanical cues stiffness, injection of scar formation that in direct between PRP and Piezo1 while PRP profibrotic factors like TGF-β1, it also (e.g., and (e.g., factors that may modulate scar outcomes through This functional the of PRP's the in clinical efficacy (e.g., studies scars whereas hypertrophic scars the synergistic interplay of three pathways may PRP's Among the components of PRP, both TGF-β1 and can directly modulate Piezo1 while other components may influence certain of the Piezo1-YAP/TAZ axis (Table that indirectly activates Piezo1 through a axis In this upregulates expression, and the mechanical force by activates in to through the Piezo1-YAP/TAZ axis, PRP can also wound healing and by growth factors and that activate YAP which in scar formation. The YAP/TAZ axis can be activated by increased ECM stiffness and shear of Conversely, in hypertrophic scars, PRP may tissue growth factor via TGF-β1 potentially excessive fibrosis Piezo1 or modulating YAP/TAZ can scar formation, suggesting therapeutic for fibrosis [8,9]. its the hypothesis lacks direct experimental no studies have PRP treatment Piezo1 in whether PRP's profibrotic effects depend on vivo, the between Piezo1 in scar tissue and therapeutic efficacy remains should the regulatory of PRP components on Piezo1 and interactions between profibrotic and the of Piezo1 in PRP-induced fibroblast in the effects of PRP activation combined with Piezo1 inhibitors on scar stiffness, and collagen deposition to optimal and clinical to Piezo1 expression in scar tissue with clinical outcomes vs. the hypothesis into precision no direct evidence that PRP scar formation by regulating the Piezo1-YAP/TAZ However, the roles of TGF-β1 and Piezo1, with their potential we hypothesize that PRP bidirectionally regulates fibroblast function and scar progression through this axis via biological effects. physiological repair it may whereas in pathological fibrosis, it could promote hypertrophic scars or keloids. PRP modulate Piezo1 through TGF-β1 matrix mechanical and mechanical forces induced by The → multidimensional effects on Piezo1-YAP/TAZ → scar pathway experimental this mechanism is essential for understanding PRP therapeutic and developing anti-scar (WB) and collagen deposition in YAP/TAZ correlates positively with fibrosis mechanical force directly regulates Piezo1 classical Smad-dependent pathway (Smad2/3 phosphorylation) and non-classical may TGF-β1 feedback in hypertrophic scars limits excessive fibrosis in hypertrophic scars via TGF-β1 feedback activates as a membrane co-factor for Piezo1 channel expression via mechanical force from activates Piezo1 YAP to wound healing and indirectly scar formation