1Director and Medical Advisor, Eutherva Medicament Pvt. Ltd., Mumbai, India
2Senior Consultant Projects and Operations, Xplora Clinical Research Services Pvt. Ltd., Bangalore, India
3PhD Scholar, Chitkara University, Punjab, India
Chronic pain disorders are commonly explained through inflammatory and nociceptive signaling pathways, with therapeutic strategies largely directed toward cytokine suppression and prostaglandin inhibition. Prostaglandins, generated from arachidonic acid via cyclooxygenase pathways, are key mediators of acute inflammatory nociception and remain an important therapeutic target; however, symptomatic improvement does not consistently restore tissue function or prevent progression to stiffness, fibrosis, and persistent movement-related pain. Increasing evidence suggests that chronic pain may involve structural alterations within the tissue microenvironment in addition to biochemical mediators. Persistent fibrin deposition, impaired fibrinolytic activity, microcirculatory compromise, and maladaptive extracellular matrix remodeling have been implicated in the progression of tissue stiffening and altered Mechan transduction. These structural abnormalities may increase interstitial pressure, disrupt tissue compliance, and sustain nociceptor activation, thereby shifting pain from a predominantly inflammatory phenomenon to a mechanically driven pathology. In parallel, prolonged peripheral matrix dysfunction may promote sustained afferent input, neuroimmune activation, and central sensitization, contributing to fatigue and cognitive dysfunction. This review synthesizes current evidence linking prostaglandin-mediated nociceptive pathways with fibrin persistence and extracellular matrix dysregulation in chronic pain and fibrosis, and proposes a matrix-centric framework to guide therapeutic strategies aimed at restoring tissue microarchitecture, microcirculatory health, and long-term functional recovery.
Chronic pain represents a complex and multifactorial clinical condition that extends beyond persistent nociceptive signaling. It is increasingly recognized as a major contributor to long-term disability, reduced quality of life, and impaired cognitive and emotional functioning1. Despite substantial advances in pharmacological and interventional pain management, many patients continue to experience incomplete recovery, characterized by persistent stiffness, reduced tissue resilience, recurrent pain episodes, and progressive functional decline 2. These outcomes suggest that existing therapeutic paradigms may inadequately address key mechanisms underlying pain chronicity.
Tissue injury also activates the arachidonic acid cascade, leading to cyclooxygenase-mediated prostaglandin synthesis. Prostaglandins play a central role in acute nociceptive signaling and inflammatory pain modulation 3. While prostaglandin inhibition provides symptomatic relief, suppression of this pathway does not necessarily resolve underlying structural abnormalities within the extracellular matrix. This distinction further supports the need to differentiate biochemical pain signaling from mechanically sustained pain mechanisms4.
Figure 1: Chronic Pain: Inflammation vs Matrix central model 4
The tissue microenvironment plays a critical role in determining mechanical integrity, cellular communication, and repair capacity. Components such as the extracellular matrix, microvasculature, lymphatic drainage systems, and provisional protein scaffolds collectively regulate tissue homeostasis and mechanotransduction5. Disruption within this structural framework can alter tissue compliance, increase interstitial pressure, and modify sensory signaling. Among these factors, persistent fibrin deposition has emerged as a potential contributor to maladaptive tissue remodeling and fibrosis in chronic inflammatory and degenerative conditions6.
Table No. 1: Matrix and Microenvironmental Alterations Implicated in Chronic Pain
|
Structural Change |
Tissue Effect |
Pain Mechanism |
Clinical Manifestation |
|
Persistent fibrin |
Increased stiffness |
Mechanical nociception |
Activity-related pain |
|
Fibrosis |
Loss of elasticity |
Altered force distribution |
Stiffness, reduced ROM |
|
Impaired lymphatics |
Interstitial congestion |
Nerve compression |
Diffuse aching |
|
Microvascular compression |
Local hypoxia |
Metabolic sensitization |
Fatigue, deep pain |
|
ECM disorganization |
Abnormal mechanotransduction |
Lower pain thresholds |
Chronic movement pain |
|
Tissue injury with arachidonic acid activation |
Prostaglandin synthesis |
Chemical nociception |
Acute inflammatory pain flare |
Fibrin is a normal and essential component of wound healing, serving as a temporary scaffold that supports cellular migration and immune containment. Under physiological conditions, fibrin is efficiently degraded as tissue repair progresses7. However, in chronic or repetitive inflammatory states, impaired fibrinolysis may lead to prolonged fibrin persistence within tissues. This abnormal retention can interfere with microcirculatory flow, obstruct lymphatic clearance, and promote excessive extracellular matrix deposition, ultimately altering tissue mechanics8.
Figure 2 : Mechanism linking fibrin persistence to chronic pain9
Growing evidence suggests that unresolved fibrin scaffolds may function as structural drivers of fibrosis and mechanical pain. By increasing tissue stiffness and sustaining nociceptor activation, fibrin-rich matrices may shift pain from a predominantly inflammatory phenomenon to a structurally mediated condition10. Furthermore, prolonged peripheral tissue dysfunction may contribute to sustained afferent signaling and neuroimmune activation, linking matrix pathology with central sensitization and cognitive symptoms commonly reported in chronic pain populations11. This review examines the role of fibrin persistence and extracellular matrix dysregulation in the development and maintenance of chronic pain and fibrosis. By integrating findings from musculoskeletal, inflammatory, and neurobiological research, the review aims to provide a cohesive framework that situates chronic pain within a broader context of tissue structure and repair12. Understanding chronic pain through this matrix-centric perspective may offer insights into more durable therapeutic strategies focused on restoring tissue microarchitecture rather than suppressing signaling pathways alone.
Limitations of Inflammation-Centric Models of Chronic Pain
Inflammation-centric models have long served as the dominant framework for understanding chronic pain. These models emphasize the role of pro-inflammatory cytokines, prostaglandins, immune cell infiltration, and nociceptive sensitization in driving pain perception. Therapeutic strategies derived from this paradigm primarily focus on suppressing inflammatory signaling through non-steroidal anti-inflammatory drugs, corticosteroids, disease-modifying agents, and targeted biologics13. While such approaches are effective in reducing acute inflammatory activity, their ability to reverse chronic pain and restore tissue function remains limited. Another limitation of inflammation-focused models lies in their emphasis on signaling pathways rather than tissue structure. While cytokines and prostaglandins play critical roles in initiating nociceptive responses, they do not adequately explain long-term alterations in tissue compliance, elasticity, and load tolerance. Chronic pain is frequently accompanied by fibrotic changes, reduced shock absorption, and impaired force distribution within affected tissues14. Such mechanical abnormalities are poorly addressed by therapies aimed solely at molecular signal suppression. Collectively, these limitations indicate that chronic pain cannot be fully understood as a prolonged inflammatory response alone. Instead, it may represent a disorder of impaired tissue repair and maladaptive remodeling, in which unresolved structural changes within the extracellular matrix and microenvironment sustain mechanical stress and nociceptive activation. Recognizing these shortcomings provides a rationale for exploring alternative frameworks that incorporate both biological signaling and tissue architecture15.
Prostaglandin-Mediated Nociception and Its Relationship to Structural Pain
Prostaglandins are lipid-derived mediators synthesized from arachidonic acid through cyclooxygenase (COX) pathways and play a central role in acute inflammatory nociception. Tissue injury and immune activation stimulate prostaglandin production, which enhances peripheral nociceptor sensitivity, promotes vasodilation, and amplifies pain perception16. Consequently, prostaglandin inhibition through non-steroidal anti-inflammatory drugs (NSAIDs) remains a cornerstone of symptomatic pain management. However, prostaglandin-driven mechanisms primarily explain biochemical amplification of pain during active inflammation and do not fully account for persistent stiffness, movement-dependent discomfort, or chronic pain syndromes that continue despite inflammatory suppression. Clinical observations suggest that while prostaglandins contribute to early nociceptive signaling, they are insufficient to explain long-term pain maintenance when structural abnormalities remain unresolved 17.
Importantly, prostaglandins also participate in physiological repair processes by regulating vascular tone, platelet activity, and tissue remodeling responses. Thus, prolonged suppression of prostaglandin pathways may reduce pain yet fail to restore tissue resilience or reverse maladaptive extracellular matrix remodeling18. These limitations highlight the distinction between transient biochemical mediators such as prostaglandins and persistent structural drivers of pain, including fibrin retention, extracellular matrix dysregulation, and fibrotic stiffening. Integrating prostaglandin-mediated nociception within a matrix-centric framework provides a more comprehensive understanding of how acute inflammatory pain may transition into mechanically sustained chronic pain19.
Physiological Role of Fibrin in Tissue Repair and Homeostasis
Fibrin plays a fundamental role in normal tissue repair and immune regulation. Following vascular injury or inflammation, fibrin is formed through the conversion of fibrinogen by thrombin, resulting in a provisional matrix that stabilizes the injury site. This fibrin scaffold provides mechanical support, limits hemorrhage, and creates a structured environment that facilitates cellular migration and tissue regeneration. Under physiological conditions, fibrin deposition is a tightly regulated and transient process20. The provisional fibrin matrix serves multiple functions during early wound healing. It supports the adhesion and migration of fibroblasts, endothelial cells, and immune cells, enabling coordinated tissue repair. Fibrin also acts as a reservoir for growth factors and cytokines, contributing to localized immune containment and controlled inflammatory signaling21. By organizing the early repair environment, fibrin ensures that tissue regeneration proceeds in an orderly and spatially defined manner.
Figure 3: Extracellular matrix damage and dysregulation in chronic pain22
Equally important to fibrin formation is its timely removal. The fibrinolytic system, primarily mediated by plasmin, degrades fibrin as healing progresses, allowing the provisional matrix to be replaced by appropriately organized extracellular matrix components such as collagen and elastin23. This transition is essential for restoring tissue elasticity, mechanical strength, and functional integrity. Efficient fibrin clearance ensures that repair processes remain adaptive rather than excessive.
Physiological fibrin turnover is closely linked to intact microcirculatory and lymphatic function. Adequate blood flow supports enzymatic fibrinolysis, while lymphatic drainage facilitates the removal of degradation products and excess interstitial proteins24. Together, these systems maintain tissue homeostasis by preventing prolonged protein accumulation and interstitial congestion.
Pathological Persistence of Fibrin and Impaired Fibrinolysis
In chronic or recurrent inflammatory states, the balance between fibrin formation and fibrinolytic clearance can become disrupted. Impaired plasmin activity, altered expression of fibrinolytic enzymes, and sustained vascular permeability may collectively promote the accumulation of fibrin-rich matrices within tissues25.
Persistent fibrin scaffolds alter the biochemical and mechanical properties of the tissue microenvironment. Unlike transient provisional matrices, unresolved fibrin networks can entrap inflammatory mediators, immune cells, and plasma proteins, prolonging localized inflammatory signaling even in the absence of overt immune activation26. This environment may sustain low-grade inflammation and interfere with the normal resolution of tissue repair processes.
Figure 4 : Linkage between persistant fibrin deposition and extracellular matrix dyregulation in chronic pain27
Fibrin-rich matrices also provide a structural framework for excessive extracellular matrix deposition. Fibroblasts interacting with persistent fibrin scaffolds may exhibit prolonged activation and increased collagen synthesis. Over time, this process can promote the transition from adaptive repair to fibrotic remodeling, characterized by excessive collagen accumulation, reduced elasticity, and impaired load distribution. Such structural alterations are commonly observed in chronic musculoskeletal disorders and fibrotic conditions28. These structural changes may remain clinically relevant even when conventional markers of inflammation appear normalized. As a result, symptom persistence and recurrence can occur despite successful suppression of inflammatory pathways29. This observation supports the notion that unresolved fibrin and associated matrix alterations represent a distinct and underrecognized contributor to chronic pain and fibrosis.
Fibrin–Extracellular Matrix Interactions and Fibrotic Remodeling
Persistent fibrin deposition does not exist in isolation but actively interacts with the surrounding extracellular matrix to influence tissue remodeling. When fibrin scaffolds fail to resolve, they can serve as a template for excessive extracellular matrix deposition, particularly collagen. This interaction alters the balance between matrix synthesis and degradation, favoring progressive stiffening and loss of normal tissue architecture30.
Table No.2 : Key Differences Between Inflammatory and Structural Pain Mechanisms
|
Feature |
Inflammatory Pain |
Matrix-Driven Pain |
|
Primary driver |
Cytokines |
ECM stiffness / fibrin |
|
Pain pattern |
Resting, throbbing |
Movement-dependent |
|
Response to NSAIDs |
Good (short-term) |
Poor or partial |
|
Imaging findings |
Synovitis |
Often minimal early |
|
Tissue mechanics |
Preserved |
Impaired |
|
Risk of recurrence |
Moderate |
High |
Fibroblasts play a central role in this process. Under physiological conditions, fibroblast activation is transient and tightly regulated, supporting controlled matrix deposition during repair. However, prolonged exposure to fibrin-rich environments may sustain fibroblast activation and promote differentiation into myofibroblasts. These cells exhibit increased contractility and enhanced collagen production, contributing to excessive matrix accumulation and tissue contraction31. The biochemical properties of fibrin further influence extracellular matrix behavior. Fibrin binds growth factors and cytokines involved in tissue repair, potentially prolonging their local activity. While beneficial during acute healing, sustained exposure to these signals may reinforce profibrotic pathways, including increased transforming growth factor-β signaling and reduced matrix degradation. Over time, this imbalance favors matrix accumulation over remodeling32. As collagen progressively replaces fibrin within the unresolved scaffold, the tissue becomes increasingly dense and mechanically rigid33. This transition reduces elasticity and impairs the ability of tissues to adapt to mechanical load. In joints, tendons, and periarticular structures, such changes may compromise shock absorption and force distribution, predisposing tissues to microdamage and mechanical pain. Fibrotic remodeling also alters cellular mechanotransduction. Cells embedded within stiff matrices experience altered mechanical cues, which can further promote profibrotic gene expression and suppress regenerative pathways. This creates a self-reinforcing cycle in which mechanical stiffness drives cellular behavior that perpetuates fibrosis. Such changes may persist independently of active inflammation, contributing to chronic pain and functional limitation34. Importantly, fibrotic matrix remodeling may remain subclinical on conventional imaging until advanced stages, complicating early detection35. Nevertheless, even modest increases in matrix stiffness can significantly affect tissue mechanics and sensory signaling. This observation may explain the discrepancy between imaging findings and symptom severity in many chronic pain conditions. Together, these interactions highlight fibrin persistence as a potential upstream event in fibrotic remodeling. By serving as both a biochemical and mechanical substrate for excessive extracellular matrix deposition, unresolved fibrin may link impaired tissue repair with chronic pain, stiffness, and loss of function36.
Therapeutic Implications of a Matrix-Centric Perspective
Recognition of extracellular matrix dysregulation and fibrin persistence as contributors to chronic pain has important implications for therapeutic strategy. Conventional management approaches primarily aim to suppress inflammatory signaling or modulate neural transmission37. While these interventions may reduce pain intensity, they often do not address the underlying structural abnormalities that sustain tissue dysfunction and mechanical nociception38. A matrix-centric perspective suggests that durable symptom improvement may require restoration of tissue microarchitecture alongside control of inflammatory and neural pathways. Strategies that support effective fibrin clearance, normalize extracellular matrix turnover, and improve tissue compliance may help interrupt the cycle of stiffness, mechanical stress, and persistent nociceptor activation. Such approaches may be particularly relevant in chronic musculoskeletal conditions where pain persists despite apparent inflammatory control. Improvement of microcirculatory and lymphatic function represents another potential therapeutic consideration. Adequate perfusion and drainage are essential for maintaining fibrinolytic activity and preventing interstitial protein accumulation. Interventions that enhance tissue perfusion, reduce interstitial congestion, or support physiological remodeling may indirectly contribute to pain reduction by alleviating mechanical and metabolic stress within affected tissues39. Importantly, a matrix-focused framework does not negate the role of inflammation or central sensitization but rather complements existing models. Inflammatory signaling may initiate tissue injury, while central mechanisms may amplify pain perception; however, unresolved structural abnormalities may serve as a persistent substrate that sustains both processes40. Addressing matrix pathology may therefore enhance the effectiveness of established therapies and reduce reliance on long-term pharmacological suppression. From a clinical perspective, this framework may also help explain variability in treatment response among patients with similar diagnoses41. Differences in tissue remodeling, fibrin burden, and matrix stiffness may influence symptom persistence and functional outcomes. Incorporating assessment of tissue structure and mechanical properties into clinical evaluation could improve stratification and guide individualized management strategies.
While clinical translation of matrix-centric interventions remains an area of ongoing investigation, existing evidence supports the relevance of tissue structure in chronic pain maintenance. Further research is needed to clarify optimal targets, timing, and combinations of therapies that support structural restoration while maintaining symptom control42.
Clinical Conditions Where Matrix Dysfunction May Be Central
Accumulating evidence suggests that extracellular matrix dysregulation and impaired fibrin clearance may contribute to a broad range of chronic conditions characterized by persistent pain, stiffness, and functional limitation. While the relative contribution of matrix pathology may vary across disease states, common structural features can be identified in several clinical contexts43.
Osteoarthritis represents a prominent example in which pain severity often correlates poorly with radiographic findings or inflammatory activity41. Progressive changes in periarticular tissues, including synovium, ligaments, and subchondral bone, may involve persistent matrix remodeling and fibrotic stiffening. These alterations can impair load distribution and joint mechanics, contributing to movement-related pain and reduced mobility independent of active synovitis39. Post-surgical and post-traumatic stiffness provides further support for the role of matrix pathology. Following tissue injury, incomplete resolution of provisional matrices and excessive fibrotic remodeling may limit range of motion and provoke chronic pain. Such outcomes may occur even in the absence of ongoing inflammation, highlighting the importance of tissue repair quality in long-term recovery. Across these diverse conditions, a recurring pattern emerges: pain persists when tissue repair is incomplete or maladaptive, rather than solely when inflammatory activity remains high44. This observation supports the concept that extracellular matrix integrity and fibrin resolution are central determinants of long-term functional outcomes. Recognizing matrix dysfunction as a shared feature across chronic pain conditions may encourage more integrative approaches to assessment and management.
CONCLUSION
Chronic pain cannot be fully explained by inflammatory signaling or prostaglandin-mediated nociception alone. While inflammatory mediators initiate pain responses, persistent structural abnormalities such as fibrin retention, extracellular matrix dysregulation, and fibrotic remodeling may sustain mechanical stress and nociceptive activation. These alterations can modify tissue compliance, elevate interstitial pressure, and generate ongoing afferent signaling independent of active inflammation. A matrix-centric framework provides a coherent explanation for several clinical observations, including discordance between inflammatory markers and symptom severity, variability in treatment response, and persistence of pain despite apparent disease control. Importantly, this perspective does not diminish the relevance of inflammatory or central mechanisms but emphasizes the need to consider tissue microarchitecture as a parallel and interacting contributor to chronic pain.Future research should focus on clarifying the temporal relationship between fibrin persistence, matrix remodeling, and pain chronicity, as well as identifying therapeutic strategies that support effective tissue repair and mechanical restoration. Integrating structural considerations into chronic pain models may enhance both mechanistic understanding and long-term management, ultimately supporting more durable functional recovery for affected patients.
REFERENCES
Dr. Madhav Deshpande, Manik Chaudhuri, Girisha Maheshwari, Prostaglandin Signaling and Matrix Dysfunction in Chronic Pain: The Role of Fibrin Persistence and Fibrotic Remodeling, Int. J. of Pharm. Sci., 2026, Vol 4, Issue 2, 4056-4066. https://doi.org/10.5281/zenodo.18768773
10.5281/zenodo.18768773
