The Needle and the Breath of the Living Network: Microbiome, Connective Tissue, and Neuroplasticity at the Interface Between Classical Chinese Medicine and Contemporary Biology

1. Introduction: From Biological Components to Interacting Systems

For much of its modern history, Western biomedicine achieved extraordinary explanatory and therapeutic power through analytical decomposition. Organs were separated into tissues, tissues into cells, cells into molecular pathways, and diseases into increasingly precise pathophysiological categories [1]. This reductionist strategy has been indispensable to the development of contemporary medicine. Yet biological understanding cannot end with decomposition. The living organism must eventually be reconstructed as an integrated system.

Contemporary biology increasingly recognizes that organs and tissues do not function as autonomous compartments [2]. Neural activity influences immune responses [3]; immune mediators alter neuronal excitability [4]; extracellular-matrix mechanics affect cellular phenotype [5]; metabolic states modify signaling pathways [6]; intestinal microorganisms generate biologically active metabolites[7]; and bidirectional communication between the gastrointestinal tract and the central nervous system contributes to physiological homeostasis and disease [8,9,10]. The body therefore increasingly appears not simply as an assembly of anatomical components but as a dynamically organized network in which mechanical, neural, immune, endocrine, metabolic, and microbial processes continuously interact.

Classical Chinese Medicine developed within a profoundly different historical and epistemological context. Nevertheless, its physiology is likewise fundamentally relational. Constructs such as Qi, Xue (Blood), Jing, Shen, Zang-Fu, and the channel or meridian systems describe patterns of transformation, circulation, functional relationship, and adaptation rather than structures that correspond straightforwardly to modern anatomical entities [11]

This distinction is essential. Qi is not adenosine triphosphate. Jing is not mitochondrial DNA. Xue cannot be reduced to circulating blood. A meridian should not be presented as demonstrably identical to a peripheral nerve, blood vessel, fascial plane, or other discrete anatomical structure. Available anatomical observations remain hypothesis-generating rather than demonstrations of ontological equivalence. Attempts to establish one-to-one correspondences risk conflating distinct explanatory frameworks. Traditional concepts lose their historical and functional meaning, while biological observations are burdened with interpretations that the experimental evidence does not support [12,13,14]

A scientifically productive dialogue therefore requires neither equivalence nor opposition. It requires comparison across levels of description. Within this framework, acupuncture provides a particularly interesting experimental model because a spatially restricted physical stimulus can generate measurable local and, under appropriate conditions, remote physiological responses [15].

2. The Needle-Tissue Interface: Mechanical Coupling and Mechanotransduction

An acupuncture needle is mechanically simple, but the biological environment into which it is introduced is not. Needle insertion traverses skin and, depending on anatomical location and insertion depth, may interact with subcutaneous connective tissue, fascia, muscle, blood vessels, and sensory nerve endings. Subsequent rotation, lifting-thrusting, or electrical stimulation can modify the characteristics of the resulting biological stimulus. Langevin et al. [16] provided important experimental evidence that the phenomenon traditionally described as “needle grasp” has a measurable biomechanical component. In this study, needle rotation markedly increased pullout force, demonstrating that needle grasp has a measurable biomechanical component. Importantly, this effect was also observed at control locations and therefore does not by itself establish acupuncture-point specificity.

The proposed mechanism involves winding of connective-tissue fibers around the rotating needle, allowing mechanical forces to be transmitted into the surrounding extracellular matrix, potentially initiating mechanotransduction within connective tissue [17]. Importantly, that publication presented a mechanistic hypothesis; it should not be interpreted as demonstrating that connective-tissue mechanotransduction constitutes the universal or dominant mechanism underlying acupuncture efficacy.

Experimental support for a cellular response subsequently emerged. In mouse subcutaneous tissue explants, needle rotation induced fibroblast spreading and lamellipodia formation and produced cytoskeletal changes extending beyond the immediate needle–tissue interface [18]. These observations provided evidence that acupuncture-like mechanical stimulation can induce active fibroblast responses consistent with mechanotransduction.

Such findings are biologically plausible within the broader framework of extracellular-matrix physiology. Fibroblasts continuously sense mechanical characteristics of their environment through integrins, cytoskeletal structures, cell-matrix adhesions, and associated signaling systems. Mechanical forces can thereby influence cellular morphology, gene expression, matrix organization, and tissue homeostasis [19,20]. The important conclusion is therefore not that connective tissue “is” the meridian system. Rather, connective tissue constitutes one biologically responsive environment through which the physical act of needling can be converted into cellular signaling.

3. Connective Tissue as a Dynamic Biological Interface

Connective tissue should no longer be understood merely as passive packing material. The extracellular matrix constitutes a three-dimensional, mechanically responsive environment composed of collagens, elastin, proteoglycans, glycosaminoglycans, water, and numerous matrix-associated proteins [20]. Fibroblasts and other resident cells continuously monitor and remodel this environment.

Mechanotransduction describes the processes through which mechanical forces are sensed and converted into biochemical and cellular responses. These mechanisms are fundamental to normal tissue homeostasis and are relevant across multiple organ systems [19]. This framework offers a biologically plausible explanation for how a localized mechanical stimulus such as needle manipulation can produce responses extending beyond the microscopic trajectory of the needle itself. It does not, however, establish that such responses account for the clinical effects of acupuncture.

The distinction between biological plausibility and clinical mediation is crucial. An intriguing observation was reported examining the anatomical relationship between acupuncture points and connective-tissue planes and finding approximately 80% correspondence between mapped acupuncture locations and intermuscular or intramuscular connective-tissue planes in the anatomical regions examined [13]. The authors proposed a possible relationship between the traditional channel system and the connective-tissue network.

This observation remains hypothesis-generating. It neither establishes anatomical identity between meridians and fascia nor demonstrates that connective-tissue planes possess the functional properties attributed to meridians within Classical Chinese Medicine. Accordingly, fascia may reasonably be investigated as one biological interface of needling but should not be presented as the anatomical translation of the meridian system.

4. From Local Stimulation to Somatosensory, Autonomic, and Immune Regulation

Mechanical tissue responses represent only one level of acupuncture physiology. Skin, subcutaneous tissue, fascia, periosteum, and skeletal muscle contain sensory afferents capable of detecting mechanical, thermal, chemical, and nociceptive stimuli. Needling can therefore generate afferent activity that reaches the spinal cord and supraspinal structures and may interact with sensory, affective, autonomic, and pain-modulatory system [15,21,22].

Purinergic signaling represents one proposed peripheral mechanism. Mechanical stimulation associated with acupuncture can influence extracellular ATP and adenosine signaling, which may interact with purinergic receptors on sensory and non-neuronal cells. Experimental evidence has implicated P2X and adenosine receptors in acupuncture-associated antinociceptive responses, although much of the detailed mechanistic evidence derives from animal models [23].

The nervous system also provides a biologically plausible mechanism through which a localized somatic stimulus can influence distant physiological functions. Somato-autonomic reflexes connect peripheral somatosensory input with autonomic efferent output. Experimental acupuncture research has demonstrated that stimulation parameters, anatomical location, depth, and intensity can determine which autonomic pathways are recruited [24]. In mice, low-intensity electroacupuncture at the hindlimb ST36 region activated a vagal-adrenal anti-inflammatory pathway dependent on a population of PROKR2-expressing sensory neurons innervating deep hindlimb tissues [25]. Ablation of these neurons prevented activation of the pathway.

This represents compelling evidence for a defined neuroanatomical mechanism under a specific experimental condition. It should not, however, be generalized to imply that all acupuncture points, all needling techniques, or all clinical effects operate through the same pathway. Indeed, the emerging neurobiology of acupuncture suggests almost the opposite: biological effects appear to depend on where, how deeply, how intensely, and by which modality tissues are stimulated.

5. Acupuncture and Neuroplasticity: Evidence and Limits

The concept of neuroplasticity requires similar precision. Neuroplasticity refers to the capacity of the nervous system to modify functional organization, synaptic strength, connectivity, cellular properties, and, under some circumstances, structure in response to experience, injury, learning, or repeated stimulation [26]. A neural response to acupuncture is therefore not synonymous with neuroplasticity. Likewise, demonstrating a change in functional magnetic resonance imaging signal after acupuncture does not by itself establish enduring neural reorganization, nor does it demonstrate that such reorganization mediates a clinical outcome.

Preclinical studies have nevertheless generated evidence that repeated acupuncture or electroacupuncture can influence processes related to neurogenesis, synaptic remodeling, neurotrophic signaling, neurotransmission, and functional recovery, particularly in experimental neurological disease models [27]. Human neuroimaging studies have additionally reported changes in functional connectivity and network activity following acupuncture, including investigations in stroke and other neurological conditions [28].

The quality and interpretation of this literature vary substantially. Neuroimaging studies may be affected by small sample sizes, analytical flexibility, heterogeneity of acupuncture protocols, inadequate control procedures, and difficulty distinguishing treatment-specific effects from contextual and expectation-related responses. It is therefore more scientifically appropriate to state that acupuncture may engage processes associated with neural plasticity in selected experimental and clinical contexts than to claim that neuroplasticity represents a universal mechanism of acupuncture. This distinction becomes particularly important when neuroplasticity is connected conceptually to the microbiome.

6. The Microbiome: The Organism as Ecosystem

The human organism is not only multicellular; it is also ecological. The gastrointestinal tract contains complex microbial communities that participate in nutrient metabolism, xenobiotic transformation, epithelial homeostasis, immune regulation, and production or modification of numerous bioactive compounds [29].

Among the most extensively investigated microbial metabolites are the short-chain fatty acids (SCFAs), particularly acetate, propionate, and butyrate. These molecules are principally generated through microbial fermentation of dietary substrates and can influence intestinal epithelial biology, immune responses, metabolism, and signaling pathways relevant to communication between the gut and other organs [30,31].

The microbiota-gut-brain axis describes bidirectional communication among intestinal microorganisms, the gastrointestinal tract, and the nervous system [7,9,31]. Relevant pathways include vagal and other neural signaling, immune mediators, endocrine pathways, microbial metabolites, tryptophan metabolism, enteroendocrine signaling, and regulation of intestinal and neurovascular barriers. The term “axis” should not be interpreted as a single linear pathway. It describes a multidirectional biological network.

The brain can alter intestinal motility, secretion, permeability, immune activity, and microbial habitat through autonomic, neuroendocrine, behavioral, and dietary mechanisms [32]. Conversely, intestinal microorganisms and their products can influence host physiology through local and systemic pathways [33]. This bidirectionality is central to understanding the microbiome without attributing excessive causal power to microbial composition alone.

7. Microbiome and Neuroplasticity: Association Is Not Causation

A particularly attractive contemporary hypothesis proposes that microbiome-related signals may influence processes relevant to neuroplasticity [34]. This is biologically plausible. Microbial metabolites can interact with immune, endocrine, neural, and epigenetic mechanisms; intestinal barrier function can alter host exposure to microbial products; and microbiota-dependent signals may influence neuroinflammation, neurotransmission, neurotrophic pathways, and behavior [35].

Nevertheless, the evidence in humans requires caution. A systematic review of 16 unique human studies linking gut microbiota with structural or functional brain connectivity found associations involving several taxa and networks, but no discernible overall pattern; findings were poorly replicated and methods were substantially heterogeneous [36]. Thus, microbiome composition and brain connectivity can reasonably be investigated as interacting domains, but current human evidence does not establish a predictable causal sequence from a particular microbial profile to a specific neuroplastic state. This distinction is especially relevant when acupuncture is introduced into the proposed pathway.

8. Acupuncture and the Gut Microbiome: An Emerging but Unsettled Field

Interest in the possibility that acupuncture might influence intestinal microbial ecology has increased considerably. Experimental studies have reported changes in microbial diversity, relative abundance of selected taxa, intestinal barrier markers, inflammatory mediators, microbial metabolites, and behavioral or physiological outcomes after acupuncture or electroacupuncture [37]. Such findings have been described across several disease models.

However, the maturity of this evidence should not be overstated. A systematic review and meta-analysis examining acupuncture and/or moxibustion effects on gut microbiota included 20 preclinical studies but only three clinical studies [38]. The authors reported changes in selected microbial measures but also emphasized considerable heterogeneity among disease models and studies. Alpha-diversity findings were not consistently different between intervention and control groups across commonly used indices.

The imbalance between animal and human evidence is important. Experimental models permit mechanistic manipulation but cannot automatically establish human therapeutic mechanisms [39]. Conversely, small clinical studies reporting simultaneous symptom improvement and microbiome changes cannot establish that microbial alterations mediate the clinical response [40].

Three propositions must therefore be distinguished:

• acupuncture is followed by a change in microbial composition;
• acupuncture modifies host physiology in a manner that changes the intestinal ecological niche; and
• microbiome modification causally mediates the therapeutic effect of acupuncture.

These propositions are not equivalent. Current evidence provides considerably greater support for the first two than for the third. Recent disease-specific reviews have proposed microbiota-gut-brain mechanisms in conditions including neuropsychiatric, cognitive, and gastrointestinal disorders [41,42]. These models are scientifically interesting, but many remain dependent on preclinical evidence and correlations among microbial, inflammatory, metabolic, neurobiological, and behavioral outcomes. Accordingly, the microbiome should currently be considered a candidate component of a broader host response to acupuncture, rather than an established universal mediator of acupuncture efficacy.

9. The Acupuncture Point as a Biological Interface

This evidence invites reconsideration of what is meant biologically by an acupuncture point. From a biomedical perspective, needling a defined location can interact with multiple tissue components: extracellular matrix, fibroblasts, immune cells, blood vessels, sensory nerve endings, muscle fibers, and, depending on depth, periosteal or other deep-tissue structures [43].

No single component necessarily defines the acupuncture point. From the perspective of Classical Chinese Medicine, the point has a different epistemological status [44]. Its meaning derives from its position within a functional system of channels, its relationships with Zang-Fu, its traditional indications, and its role within patterns involving Qi, Xue, Yin-Yang, and the Five Phases. The two maps therefore operate at different explanatory levels. A contemporary biological map can ask what tissues are stimulated, which afferent populations are activated, which molecular mediators are released, which central networks respond, and which autonomic or immune functions change. The traditional map asks how the same intervention should be understood within a system of functional relationships developed through a different medical tradition. Scientific difficulty arises when observations made on one map are presented as proof of the ontological reality of constructs belonging to the other.

10. Qi, Connective Tissue, and Biological Information: The Importance of Non-Equivalence

Modern attempts to reinterpret Qi as bioelectricity, ATP, electromagnetic energy, extracellular-matrix signaling, interstitial fluid movement, or “information” are conceptually attractive but scientifically problematic. These terms describe different phenomena. Mechanotransduction belongs to cellular and molecular biology. Neuroplasticity belongs to neuroscience. Microbial ecology describes communities of microorganisms and their interactions with the host. Autonomic regulation concerns defined neural circuits and physiological outputs [12,13,14,43].

Qi, by contrast, belongs to a medical-philosophical framework in which physiological processes are described through transformation, movement, relationship, polarity, and functional pattern. The intellectual value of bringing these frameworks together therefore lies not in declaring equivalence, but in asking whether they generate complementary questions. The question should not be: What modern molecule is Qi? A more productive question is: Can the relational logic embodied in traditional medical concepts stimulate experimentally testable hypotheses about multilevel biological regulation? That formulation permits dialogue without pseudoscientific reductionism.

11. Toward a Multilayered Biological Model of Acupuncture

The available evidence supports a model in which several partially overlapping levels of biological response can be distinguished. However, the strength and directness of evidence differ substantially across these levels, ranging from direct biomechanical observations and experimentally defined neuroanatomical circuits to predominantly associative evidence for neuroplastic and microbiome-related effects. Representative mechanistic evidence across these biological levels, together with the principal limitations of each evidence domain, is summarized in Table 1.

Taken together, these observations support a context-dependent multilevel model in which acupuncture is conceptualized as a localized physical perturbation capable of engaging tissue, sensory, autonomic, central neural, immune–endocrine, and gut–microbial domains to varying degrees (Figure 1).

At the local mechanical level, needle insertion and manipulation deform tissues and can engage extracellular-matrix and fibroblast mechanotransduction [13,16,17,18,19]. At the peripheral neurochemical level, mechanical stimulation may influence sensory afferents and local signaling systems, including purinergic pathways [23]. At the neural level, somatosensory input can reach spinal and supraspinal networks and, under specific conditions, recruit defined autonomic reflex pathways [24,25]. At the central adaptive level, repeated stimulation may be associated with functional and structural processes relevant to neuroplasticity, although evidence and causal interpretation remain condition-specific [27,28]. At the immune and metabolic levels, neural, endocrine, and local tissue responses may modify inflammatory signaling and systemic physiology [22]. Finally, at the microbial-ecological level, changes in host autonomic activity, intestinal motility, secretion, immunity, barrier function, diet, metabolism, and behavior could alter the intestinal environment and thereby influence microbial communities. Conversely, microbiota-derived signals could theoretically participate in downstream host responses [8,10,30,31,36,38,47].

These levels should not be represented as a proven linear sequence: needle → fascia → nervous system → gut → microbiome → brain → clinical improvement. Current evidence does not justify such a deterministic pathway. A more appropriate representation is a multidirectional network with condition-dependent interactions, some of which are experimentally supported, some biologically plausible, and others still hypothetical.

12. The Living Network

The organism can therefore be viewed as containing multiple superimposed networks: an extracellular and mechanical network; a sensory and autonomic neural network; an immune network; endocrine and metabolic networks; an intestinal microbial ecosystem; and the higher-order neural networks through which perception, cognition, affect, and behavior emerge [22].

These systems are not independent. When a needle enters the body, it enters this interconnected biological environment. Mechanical forces can alter local tissues. Sensory afferents can encode the stimulus. Central neural structures can integrate the incoming information. Autonomic outputs can influence distant organs. Immune and metabolic pathways may participate in the response. Under particular circumstances, intestinal physiology and microbial ecology may also change.

This does not imply that an invisible signal travels directly from an acupuncture point to the intestine, nor that every level is recruited by every acupuncture intervention. It means something simultaneously simpler and more important: biological compartments are permeable to information from other compartments. In this respect, contemporary systems biology and Classical Chinese Medicine can enter into a meaningful conceptual conversation without becoming interchangeable.

13. Neuroplasticity as a Particular Expression of Biological Adaptability

Plasticity is not unique to the nervous system. Connective tissue remodels in response to mechanical load. Epithelia continuously renew themselves. Immune systems develop memory. Microbial communities change in response to diet, medications, host physiology, age, environment, and disease. Extracellular matrices are continually synthesized and degraded. Neuroplasticity represents the nervous system’s contribution to this broader biological capacity for adaptation.

Repeated acupuncture stimulation may therefore be conceptualized as one form of repeated sensory experience capable, under appropriate circumstances, of participating in adaptive nervous-system responses [48]. The magnitude, duration, specificity, and clinical relevance of those responses must nevertheless be demonstrated rather than assumed. This perspective replaces the vague claim that acupuncture “induces neuroplasticity” with a testable scientific question: Under which conditions does repeated acupuncture stimulation produce reproducible neural changes, through which mechanisms, and to what extent do those changes mediate clinically meaningful outcomes? The same question should be applied to the microbiome.

14. From Plausibility to Causality: A Research Agenda

The next phase of acupuncture mechanism research should distinguish biological response from causal mechanism. A useful hierarchy is: a response is observed after stimulation; the response covaries with an outcome; the response temporally precedes and statistically mediates the outcome; perturbing the pathway attenuates the outcome; and, where experimentally feasible, selective activation is sufficient to reproduce the relevant phenotype. The strength of a mechanistic claim should reflect how far the evidence progresses along this sequence (Figure 2).

First, stimulation must be treated as a doseable anatomical intervention rather than a binary exposure. Studies should prespecify location, depth, tissue compartment, manual manipulation, electrical frequency, pulse width, current intensity, duration, and relevant sensory or motor thresholds. Factorial experiments comparing body region, superficial versus deep stimulation, and intensity can test whether biological specificity is predicted by the recruited neural or tissue substrate [12,25,49].

Second, neuroplasticity studies require longitudinal rather than purely acute designs. Predefined imaging and physiological endpoints should be measured beyond the immediate stimulation period, linked to validated behavioral or clinical outcomes, and analyzed for temporal precedence and mediation. Multicenter replication, harmonized acquisition pipelines, and appropriately designed controls are particularly important given the heterogeneity and small samples of the current imaging literature [28].

Third, microbiome hypotheses require progression from association toward perturbation-based evidence, including depletion, transfer, strain-level testing, and ultimately defined microbial molecules. Serial metagenomic and metabolomic sampling in humans should establish temporal order and account for diet, medication, bowel function, geography, and other major confounders. In experimental models, antibiotic or germ-free perturbation, fecal microbiota transfer, strain-level testing, and ultimately candidate microbial molecules can progressively determine whether the microbiome is necessary, sufficient, or merely responsive [40].

Finally, the proposed “living network” should become measurable. Studies that synchronize tissue, autonomic, immune, metabolic, microbial, and neural readouts can test whether cross-system changes occur in a coherent temporal sequence. The aim is not to measure every layer in every experiment, but to identify the smallest set of interacting nodes required to explain a defined physiological or clinical effect and then reproduce that pathway independently [22,28]. The principal research priorities needed to advance these mechanistic claims from association toward causal inference are summarized in Table 2.

15. An Interpretative Boundary: From Network Biology to Classical Concepts

At this point the dialogue with Taoist thought becomes philosophical rather than experimental. The Tao is not an anatomical structure or measurable biological variable. It describes process, transformation, relation, and continuous becoming. Modern biology, from a completely different intellectual tradition, increasingly portrays the organism as a non-static system. Cells remodel their environment; neural circuits change with experience; immunity adapts to encounters; microbial ecosystems respond to ecological pressures [46].

The similarity should not be mistaken for scientific identity. Rather, it offers a productive metaphor: living systems maintain continuity not by remaining unchanged, but by continually reorganizing themselves in response to internal and external conditions.

Within this interpretative framework, acupuncture can be considered a controlled perturbation introduced into a complex adaptive system. The scientific task is to determine which components of that system actually respond, through which pathways, under which conditions, and with what clinical consequences. The philosophical task is different: to consider what such responsiveness tells us about the nature of the living body. Keeping these two tasks distinct makes their dialogue stronger rather than weaker.