Myometrial mechanotransduction and the timing of parturition: ion-channel pathways linking uterine stretch, calcium signaling, and inflammation

The timing of myometrial activation is central to both physiologic labor and preterm labor risk. During most of gestation, the uterus remains mechanically adaptable while limiting coordinated excitability; at term, the same tissue acquires the electrical, inflammatory, and contractile readiness required for effective labor ( Shynlova et al., 2020 ; Wray and Arrowsmith, 2021 ). Mechanical load is therefore not a passive background variable. It changes across pregnancy and can alter how endocrine, inflammatory, and smooth-muscle excitability pathways are interpreted ( Wray et al., 2015 ; Arrowsmith, 2023 ). A channel-centered view is useful because mechanical force is ultimately translated into ionic flux, membrane potential changes, Ca² + handling, transcriptional programs, inflammatory signaling, and contractile behavior. This does not mean that every labor pathway is an ion-channel pathway, or that every mechanically responsive conductance is a primary mechanosensor. It means that ion channels occupy a strategic interface between tissue loading, cellular excitability, Ca² + entry, and contraction timing. Existing reviews have clarified myometrial activation ( Shynlova et al., 2020 ), uterine excitability ( Wray and Arrowsmith, 2021 ), and mechanical factors in labor timing ( Arrowsmith, 2023 ). Hormonal control has also been reviewed in detail ( Hamburg-Shields and Mesiano, 2024 ), but a focused synthesis is still needed for human-centered, model-supported ion-channel mechanotransduction in the pregnant myometrium. The scope here is deliberately narrower than broad pregnancy mechanobiology, placenta-first signaling, fetal-membrane biology, cervical remodeling, immune-cell pregnancy biology, or general preterm-birth etiology. Preterm birth is discussed only where the evidence informs premature myometrial activation, preterm labor relevance, or inflammatory and hypercontractile timing problems ( Fan et al., 2025 ). For clarity, the shorthand used below is defined here: PIEZO1 and PIEZO2 are mechanically activated Piezo channels; TRPV4 is transient receptor potential vanilloid 4; TRPC denotes transient receptor potential canonical channels, with TRPC3 used where a specific isoform is discussed; TREK-1 is a two-pore-domain K + channel; TMEM16A/ANO1 is a Ca² + -activated Cl - channel; TRPM4 is transient receptor potential melastatin 4; L-type voltage-gated Ca² + channels, connexin-based gap junctions, and BK/KCa channels are treated as major executors of membrane excitability and contraction propagation rather than as primary stretch sensors. This is a focused mechanistic narrative Review. Source selection prioritized studies and reviews that inform pregnant myometrium or uterine smooth muscle, PIEZO/TRPV4/TRPC/TREK/TMEM16A/TRPM4 biology, stretch or inflammatory perturbation, human ex vivo tissue evidence, pregnancy model systems, and engineered platforms that clarify mechanical assay context. Evidence from adjacent reproductive tissues is used as boundary or background support rather than as primary evidence for myometrial labor outcomes. Throughout this Review, “mechanosensitive” is reserved for evidence that directly links mechanical force, stretch, or force-gated channel activity to the tested myometrial context. “Mechanically responsive” describes pathways altered by stretch, matrix, culture mechanics, or tissue architecture without proving direct force gating. “Adjacent excitability regulation” describes conductance and Ca² + -handling pathways that shape membrane potential, Ca² + entry, or contractile readiness downstream of, adjacent to, or in parallel with mechanotransduction. The Review first defines the mechanical and endocrine context needed to interpret channel evidence, then evaluates PIEZO and TRPV4 as the most visible force- and Ca² + -linked candidates, places TRPC, TREK, TMEM16A, TRPM4, and related pathways in their functional excitability roles, and finally separates coordinated term parturition from overdistension-associated and infection/inflammation-associated premature activation.

TRPV4 is a strong Ca² + -linked myometrial signaling candidate, but it is not best interpreted as a universal pro-contractile stretch sensor. In gravid human uterine contexts, TRPV4 has been linked to oxytocin-associated Ca² + entry and smooth-muscle contraction ( Fornes et al., 2026 ). In inflammatory preterm-labor models, TRPV4 loss or inhibition can reduce NF-κB-associated myometrial inflammation and preterm-labor susceptibility ( Ingles et al., 2025 ). Effect direction is assay-, agonist-, and state-dependent. Human myometrial tissue studies of TRPV4 activation have also reported reduced contractility under tested conditions, which blocks a selective pro-contractile narrative ( Villegas et al., 2021 ). Additional uterine-tone and pregnancy-context evidence supports TRPV4 involvement in contractility, but this remains model- and pharmacology-dependent ( Singh et al., 2015 ; Ying et al., 2015 ). Not all TRPV4 evidence is stretch evidence. Oxytocin-associated TRPV4 activation, direct TRPV4 agonism, inflammatory NF-κB signaling, and uterine-tone experiments are distinct contexts. The available evidence does not show that uterine stretch directly activates TRPV4 in vivo during labor. Direct stretch/Ca² + evidence is better supported through TRPC pathways ( Dalrymple et al., 2007 ). TRPV4 is used here for inflammatory amplification and oxytocin-associated coupling ( Ingles et al., 2025 ; Fornes et al., 2026 ). Regulatory layers further shape this interpretation. miR-203 modulation of the TRPV4-contractility axis and pharmacologic interactions involving calcium-channel or TRPC-related pathways indicate that channel function is embedded in broader transcriptional and Ca² + -handling programs ( Yart et al., 2022 ; Ying et al., 2024 ). These sources support TRPV4 as a state-specific coupling pathway rather than an isolated determinant of labor onset. Together, these studies support TRPV4 as a state-specific Ca² + /inflammatory coupling pathway rather than a universal direct stretch sensor or uniformly pro-contractile pathway in the pregnant human myometrium. Cross-system PIEZO1-TRPV4 studies help interpret this uncertainty without being directly transferable to the uterus. In pancreatic acinar cells, PIEZO1 activation can open TRPV4 and generate sustained Ca² + signaling during pressure-induced pancreatitis ( Swain et al., 2020 ). In endothelial cells, high shear stress has been reported to place PIEZO1 upstream of TRPV4, with the TRPV4-dependent sustained Ca² + phase contributing to junctional and cytoskeletal changes ( Swain and Liddle, 2021 ). These studies support three uterine hypotheses: PIEZO1 and TRPV4 may act independently in different cell compartments; they may converge on shared Ca² + , inflammatory, or contractility outputs; or, in some states, PIEZO1 may lie upstream of TRPV4-like sustained Ca² + signaling. At present, only the first two interpretations are directly defensible for pregnant myometrium; a sequential PIEZO1-to-TRPV4 pathway remains a testable extrapolation rather than a demonstrated labor mechanism.

PIEZO channels provide the clearest route for linking mechanical force to myometrial signaling, but their interpretation is best separated by evidence layer. Recent mechanistic work positions PIEZO1 and PIEZO2 as force-sensitive channels involved in parturition-relevant uterine contraction programs in tested models ( Zhang et al., 2025 ). This evidence anchors the stretch-to-channel concept more directly than older general discussions of stretch-activated currents. Current human myometrial evidence is stronger for PIEZO1 than for PIEZO2. PIEZO1 presence and pharmacologic modulation have been reported in relevant human tissue contexts, but one important ex vivo line points toward Yoda1-associated relaxation and endothelial-myometrial crosstalk rather than a uniform pro-contractile effect ( Barnett et al., 2023 ). In contrast, inflammation-associated preterm-birth models link uterine PIEZO1 overexpression to contraction and inflammatory activation ( Bi et al., 2024 ). These findings indicate compartment- and state-specific effects rather than a single uniform direction of action. Three interpretive distinctions are central. Genetic or preclinical PIEZO1/PIEZO2 findings, human tissue pharmacology, and inflammatory perturbation studies represent different evidence layers. Endothelial, vascular, and myocyte localization may imply different cellular effects. Agonist-driven, deletion, overexpression, and inflammatory systems may capture different points in a pathway. Human PIEZO1 pharmacology and inflammatory-model findings are therefore interpreted as complementary but non-interchangeable contexts ( Barnett et al., 2023 ; Bi et al., 2024 ). Parturition-model PIEZO evidence adds model support ( Zhang et al., 2025 ). PIEZO2 is treated more cautiously than PIEZO1 in the human myometrial setting because direct human evidence remains limited. PIEZO2 also requires a neural boundary. In somatosensory biology, PIEZO2 is a key mechanotransducer for human touch and proprioception ( Chesler et al., 2016 ). The recent parturition study supports a role for PIEZO channels in uterine contraction programs, but direct pregnant-human-myometrium evidence remains much stronger for PIEZO1 than for PIEZO2 ( Zhang et al., 2025 ). A plausible extension is that uterine or cervical stretch could be detected by sensory afferents and coupled to autonomic, neuroendocrine, or local neuromodulatory pathways; catecholaminergic neurofibers in the pregnant cervix provide adjacent reproductive-tract context for neural participation ( Malvasi et al., 2024 ). This neural route is best framed as a mechanistic hypothesis, not as established evidence that PIEZO2 directly gates human myometrial contraction. Evidence from uterine hypercontractility outside normal pregnancy can support plausibility, but it is treated here as uterine smooth-muscle context rather than as pregnancy-specific evidence. For example, PIEZO1-related hypercontractility in adenomyosis-associated dysmenorrhea supports PIEZO-linked uterine smooth-muscle function, but it does not establish a pregnancy-specific preterm-birth mechanism ( Yan et al., 2026 ). The synthesis is therefore not a single arrow from stretch to PIEZO1 to labor. PIEZO channels provide a candidate mechanotransduction route, but PIEZO1 directionality depends on compartment, pregnancy context, perturbation, and inflammatory state; PIEZO2 remains a more limited human-myometrium claim. Figure 1 , Table 1 summarize this distinction across evidence layers. Evidence-tier view of ion-channel mechanotransduction in the pregnant myometrium. The schematic integrates mechanical, endocrine, and inflammatory inputs that can influence ion-channel signaling in the pregnant myometrium. Candidate direct mechanosensor pathways are distinguished from mechanically regulated Ca² + /inflammatory coupling pathways and from adjacent excitability regulators. Solid arrows indicate links directly supported in the cited experimental context; dashed arrows indicate setting-dependent or model-supported links; and muted or dotted visual emphasis indicates more limited direct evidence in pregnant human myometrium. PIEZO1 evidence is anchored by human tissue and inflammatory-model studies ( Barnett et al., 2023 ; Bi et al., 2024 ), while parturition-model evidence extends the PIEZO concept ( Zhang et al., 2025 ). TRPC/TRPV4 evidence supports Ca² + /inflammatory coupling in specific contexts ( Dalrymple et al., 2007 ; Ingles et al., 2025 ), with oxytocin-linked TRPV4 evidence shown separately ( Fornes et al., 2026 ). Adjacent excitability examples include TRPM4 and TMEM16A-related pathways ( Fouchet et al., 2023 ; Parkington et al., 2026 ). The figure summarizes a bounded synthesis rather than a single validated causal pathway. Channel-specific evidence boundaries in myometrial mechanotransduction.

The remaining channel pathways are included for their physiologic function, not to create a catalogue of uterine ion channels. Their role is to explain how Ca² + , K + , Cl - , and membrane-excitability pathways, together with canonical voltage-gated and cell-coupling executors, shape the conversion of mechanical, oxytocin-associated, or inflammatory inputs into contractile readiness. General reviews of uterine excitability and electromechanical signaling provide the background for this functional grouping ( Wray et al., 2015 ; Wray and Arrowsmith, 2021 ). TRPC channels are most relevant as supporting Ca² + -entry pathways. Mechanical stretch can regulate TRPC expression and Ca² + entry in human myometrial smooth-muscle cells, and labor or inflammatory contexts can influence TRPC-related Ca² + pathways ( Dalrymple et al., 2004 , 2007 ). Rat and human uterine studies support TRPC or TRP-homologue expression in pregnant myometrium ( Dalrymple et al., 2002 ; Ku et al., 2006 ). Rat capacitative calcium TrpC protein evidence adds pregnancy-model support ( Babich et al., 2004 ). Stretch-induced uterine contraction models then provide source-specific support for TRPC4/5-like channels in pregnancy-associated contractile responses ( Chung et al., 2014 ). TRPC3 requires a narrower interpretation. The miR-26a-5p/TRPC3 preterm-labor axis and the PLC-gamma/PKC/CPI-17 pathway support TRPC3 as a preterm-labor-related Ca² + or excitability regulator, but by themselves they provide limited support for TRPC3 as a primary mechanosensor ( Chen et al., 2018 , 2024 ). In the current evidence base, TRPC3 is therefore best placed in downstream Ca² + -dependent regulation rather than direct stretch sensing. K + and Cl - pathways provide hyperpolarizing brakes and depolarizing or excitability support. TREK-1 and related stretch-activated potassium currents can shape uterine smooth-muscle contraction and pregnancy-associated excitability ( Buxton et al., 2010 , 2011 ). Human variant evidence adds preterm-labor context ( Wu et al., 2012 ). Human myometrial TREK-1 currents and TRPM4 contribute to reproductive-tract and uterine contraction physiology ( Heyman et al., 2013 ; Fouchet et al., 2023 ). TMEM16A chloride-channel evidence adds a female-reproductive-tract and labor-related excitability boundary ( Parkington et al., 2026 ). L-type voltage-gated Ca² + channels, connexin/gap-junction coupling, and BK/KCa channels therefore remain explicit in this section. L-type channels convert depolarization into phasic Ca² + entry and contraction, connexin-based coupling permits electrical and contractile propagation across the myometrium, and BK/KCa currents buffer excitability and contribute to quiescence or repolarization. They are central to contraction propagation and tocolytic pharmacology, including nifedipine-linked L-type Ca² + -channel blockade, but they function here as downstream or parallel executors of membrane excitability rather than as proof of direct stretch sensing. Broad electromechanical and excitability reviews provide the main executor context ( Wray et al., 2015 ; Wray and Arrowsmith, 2021 ). Nifedipine/TRPC1 evidence adds a pharmacologic boundary ( Yart et al., 2022 ). Calcium-handling and homeostatic pathways complete the physiologic context. Store-operated Ca² + entry supports a myometrium in which contraction timing depends on multiple interacting electrical and Ca² + programs ( Tribe et al., 2000 ; Chin-Smith et al., 2014 ). CD38/cADPR signaling adds another Ca² + -handling layer ( Dogan et al., 2024 ). SLO2.1/NALCN activity and oxytocin-related K + conductance regulation add an additional excitability layer ( Ferreira et al., 2019 , 2025 ). These pathways support the central argument without replacing channel-specific mechanotransduction evidence.

Several conclusions can be drawn with reasonable confidence from the current evidence. Mechanical context changes how myometrial ion-channel evidence is interpreted, PIEZO1 has stronger human myometrial support than PIEZO2, TRPV4 links Ca² + and inflammatory signaling in a setting-limited way rather than acting as a universal stretch sensor, and TRPC/TREK/TMEM16A/TRPM4-related conductances help set excitability and Ca² + handling. Human ex vivo assays can separate tissue-level pharmacology from direct in vivo labor timing ( Arrowsmith et al., 2018 ). Engineered tissues clarify mechanical context and assay readout ( Maxey et al., 2023 ; Claure et al., 2026 ), while bioprinted models extend this assay logic ( Ulrich et al., 2025b ). High-throughput Ca² + systems add screening readouts rather than clinical validation ( Herington et al., 2015 ). Major uncertainties remain unresolved. Human tissue pharmacology can reveal contractility effects that isolated cells may miss, but receptor context, donor state, agonist conditions, and inflammatory state can alter interpretation. Retosiban and oxytocin-linked ex vivo studies illustrate this tissue-pharmacology boundary ( Aye et al., 2018 ; Balki et al., 2025 ). Oxytocin physiology provides broader peripartum context ( Uvnäs-Moberg, 2024 ). Nifedipine/TRPC1 interactions and TRPV4 reduced-contractility evidence further show that channel-centered mechanisms cannot be translated without dose, tissue-state, and safety validation ( Villegas et al., 2021 ; Yart et al., 2022 ). Translation requires a higher evidentiary bar than mechanistic plausibility. Single-cell atlases and calcium-transporter signatures can identify tissue-state axes ( Ackerman et al., 2021 ; Pique-Regi et al., 2022 ). Inflammatory/prostaglandin systems and RAC1 biology help define validation needs under premature-activation conditions ( Diao et al., 2022 ; Riaposova et al., 2023 ). Engineered inflammatory systems add assay-level context ( Maxey et al., 2024 ). Matrix metallopeptidase-related contraction evidence adds another state-dependent contraction signal ( Ulrich et al., 2025a ). These sources are insufficient to replace channel-specific evidence or establish a pregnancy intervention. Future work can focus on three linked questions. First, how do PIEZO1 and PIEZO2 differ by myometrial compartment, inflammatory state, gestational timing, and species? Second, under which agonist, mechanical, and inflammatory conditions does TRPV4 support contraction, relaxation, or inflammatory amplification? Third, when TRPC, TREK, TMEM16A, TRPM4, and related channels are described as mechanically responsive, what evidence separates direct mechanosensing from downstream excitability support? Progress will require state-resolved experimental designs that combine mechanical variables, inflammatory context, human tissue relevance, and carefully chosen readouts.

Pregnant myometrium is interpreted through mechanical stretch, progesterone and estrogen balance, oxytocin tone, extracellular-matrix state, tissue architecture, and the gestational transition from quiescence to activation. Uterine stretch and progesterone action have long been linked to labor timing, and modern accounts of myometrial activation emphasize that endocrine and mechanical contexts interact rather than operating as isolated pathways ( Lei et al., 2011 ; Shynlova et al., 2020 ). Assay context is therefore part of the evidence, not a technical afterthought. A channel agonist, inhibitor, deletion, or expression change can have different functional meaning in isolated myocytes, engineered tissues, human ex vivo strips, animal pregnancy models, or inflamed tissue. Hydrogel and engineered-tissue systems show that the mechanical microenvironment can alter myometrial morphology, Ca² + responsiveness, gene expression, and agonist response patterns ( Maxey et al., 2023 ; Marr et al., 2024 ). A scalable hydrogel platform extends this model-system evidence ( Claure et al., 2026 ), but these platforms remain model systems rather than in vivo labor-outcome evidence. Mechanical signals are also distributed through cytoskeletal, adhesion, and phospho-signaling networks. Studies of mechanoadaptation and mechanical strain support a tissue-scale view in which force is interpreted through architecture and intracellular signaling rather than through a single membrane channel ( Wu et al., 2008 ; Copley Salem et al., 2018 ). Integrin organization adds adhesion-complex context ( McLendon et al., 2021 ). Human labor mechanotransduction models and uterine bioelectrical behavior add complementary tissue-level context ( Young, 2016 ; Garfield et al., 2021 ). This Review interprets evidence on three levels: direct force-gated or force-linked channel activation in myometrial systems; mechanically regulated channel expression or signaling without direct proof of force gating; and adjacent excitability pathways that shape the consequences of mechanical, endocrine, or inflammatory inputs. Stretch-induced receptor and adhesion/kinase changes provide important context ( Terzidou et al., 2005 ; Li et al., 2009 ). Prolonged-stretch contractility evidence adds a separate model boundary ( Tattersall et al., 2012 ). The strength of PIEZO, TRPV4, or TRPC claims therefore depends on channel-specific evidence in the tested system.

The main advance of this Review is not the proposal of a single labor channel pathway, but a bounded synthesis of how force-sensitive, mechanically responsive, and excitability-regulating ion-channel mechanisms may shape the timing of myometrial activation. PIEZO channels provide the strongest candidate direct mechanotransduction route, with PIEZO1 directionality depending on compartment and inflammatory state and PIEZO2 requiring more cautious human-myometrium interpretation. TRPV4, TRPC, TREK, TMEM16A, TRPM4, and related pathways are best understood as state-limited Ca² + , inflammatory, and excitability regulators rather than isolated therapeutic switches. Physiologic term parturition, overdistension-associated premature activation, and infection/inflammation-associated preterm birth can share downstream modules, but they differ in trigger, timing, tissue state, and translational readiness. The strongest future need is not simply more channel association studies, but state-resolved validation in human myometrium and carefully bounded model systems. Such work will determine which channel-linked mechanisms are direct force sensors, which are mechanically regulated coupling pathways, and which are adjacent excitability regulators that shape the consequences of uterine load and inflammation.

The central synthesis is that the same broad physiologic programs can participate in different timing outcomes. Physiologic term parturition and premature activation both involve excitability, Ca² + signaling, endocrine tone, inflammatory mediators, and contraction programs. Their interpretation depends on timing, trigger, tissue state, and regulatory context. Progesterone and parturition-hormone physiology provide endocrine boundary conditions ( Shynlova et al., 2023 ; Hamburg-Shields and Mesiano, 2024 ), while oxytocin physiology adds a peripartum signaling context ( Uvnäs-Moberg, 2024 ). Progesterone-receptor and broader electromechanical accounts add developmental and timing context ( Wu and DeMayo, 2017 ; Zangeneh and Hantoushzadeh, 2023 ). This timing distinction helps resolve apparent channel conflicts. PIEZO1 need not be uniformly pro-contractile or anti-contractile if human ex vivo relaxation/quiescence signals and inflammation-associated contractile/PTB signals arise from different compartments, agonist contexts, and inflammatory states ( Barnett et al., 2023 ; Bi et al., 2024 ). Similarly, TRPV4 can be linked to oxytocin-associated contraction and inflammatory activation ( Ingles et al., 2025 ; Fornes et al., 2026 ), while tocolytic or reduced-contractility evidence blocks a simple pro-contractile story ( Villegas et al., 2021 ). Uterine-tone data add another state-specific layer ( Ying et al., 2015 ). Adjacent excitability evidence requires the same context separation. TRPC and TRPC3 evidence is separated into stretch-responsive Ca² + entry and preterm-labor regulatory support ( Dalrymple et al., 2007 ; Chen et al., 2024 ). TRPM4 and CD38/cADPR evidence define contractile and Ca² + -handling context ( Fouchet et al., 2023 ; Dogan et al., 2024 ). TMEM16A evidence adds a chloride-channel and reproductive-tract boundary ( Parkington et al., 2026 ). These pathways are not elevated to master mechanotransducers without direct force-sensing evidence. The physiologic-versus-pathologic distinction also clarifies the clinical framing. Mechanosensitive and mechanically responsive ion channels may identify vulnerabilities in myometrial activation, but current evidence does not support treating them as ready prevention targets for preterm birth. The evidence is strongest for mechanistic plausibility, tissue and model-system biology, and future assay design; it is weaker for direct clinical intervention, timing, safety, and patient selection.

Inflammation is part of normal labor biology, but it is also a route through which premature activation can be amplified. Myometrial cytokines, NF-κB activity, prostaglandin-related signaling, and endocrine-mechanical integration support inflammatory participation in labor onset and myometrial activation ( Khanjani et al., 2011 ; Sivarajasingam et al., 2016 ). Myometrial leukocyte interactions add immune-cell context ( Siewiera and Erlebacher, 2020 ). A channel-centered synthesis connects this biology to Ca² + and excitability while preserving differences among triggers. Figure 2 and Tables 2 , 3 summarize these distinct routes, their shared downstream modules, and the evidentiary limits of the contributing model systems. Distinct routes to term labor and preterm myometrial activation. Physiologic term parturition, overdistension-associated premature activation, and infection/inflammation-associated PTB are shown as partially overlapping but mechanistically non-equivalent routes to altered myometrial readiness. Shared downstream modules, including Ca² + signaling, membrane excitability, cytokine/NF-κB activity, prostaglandin pathways, and contractile readiness, still differ in triggers, timing, and tissue-state biology. Term inflammatory priming is supported by NF-κB and cytokine literature ( Cookson and Chapman, 2010 ; Khanjani et al., 2011 ) and by labor-onset synthesis ( Sivarajasingam et al., 2016 ). Overdistension and stretch-related premature activation are supported by mechanical/endocrine evidence ( Shynlova et al., 2008 ; Lee et al., 2015 ) and by human/nonhuman-primate overdistension evidence ( Adams Waldorf et al., 2015 ). Infection/inflammation-associated PTB is represented by immune and inflammasome evidence ( Lei et al., 2024 ; Lopez et al., 2024 ), with infection-related clinical context shown separately ( Fan et al., 2025 ). The figure is limited to evidence synthesis, without treatment, prediction, or one-step causal claims beyond the cited literature. Distinct trigger contexts that converge on myometrial activation. What each evidence system can and cannot establish in this field. Mechanical and endocrine signals can converge with inflammatory mediators. Stretch-induced cytokine or prostaglandin responses support mechanical-load/inflammatory convergence in myometrial cells and related tissue signaling ( Korita et al., 2004 ; Sooranna et al., 2005 ). CCL2/MCP-1 adds endocrine-mechanical integration context ( Shynlova et al., 2008 ). NF-κB and AP-1/IL-8 regulation add inflammatory transcriptional context ( Cookson and Chapman, 2010 ; Khanjani et al., 2012 ), and stretch-induced cytokine effects on endothelial recruitment show tissue-level immune coupling ( Lee et al., 2015 ). Three contexts are best kept distinct. Physiologic term inflammatory priming contributes to coordinated labor rather than automatically representing disease. Overdistension-associated premature activation is supported by pregnant-woman and nonhuman-primate evidence for mechanical-overload inflammatory signaling ( Adams Waldorf et al., 2015 ). Infection/inflammation-associated PTB is better supported by microbial/innate immune evidence ( Lappas, 2017 ; Lei et al., 2024 ) and by inflammasome evidence ( Lopez et al., 2024 ). A broader infection-related PTB synthesis frames the clinical context ( Fan et al., 2025 ). These contexts can share mediators, but they are not interchangeable explanations. TRPV4 and PIEZO evidence is most informative in this inflammatory discussion when it is linked to explicit context labels. TRPV4 can potentiate NF-κB-mediated inflammatory activation in preterm-labor models, and inflammatory PIEZO1 overexpression can be linked to contraction and preterm-birth contexts ( Bi et al., 2024 ; Ingles et al., 2025 ). These claims remain mechanistic and model-dependent, with insufficient support for a universal inflammatory PTB pathway or a ready drug target. This synthesis therefore treats coordinated term parturition, overdistension-associated premature activation, and infection/LPS/inflammasome-associated activation as partially overlapping but non-equivalent routes. Shared downstream modules such as Ca² + entry, NF-κB, cytokine signaling, prostaglandin pathways, and contraction readiness can appear in more than one route, but the triggers, timing, tissue states, and evidence layers remain distinct.