Fluid flow along venous adventitia in rabbits: is it a potential drainage system complementary to vascular circulations?

Objectivization study of acupuncture Deqi and brain modulation mechanisms: a review

Deqi is an important prerequisite for acupuncture to achieve optimal efficacy. Chinese medicine has long been concerned with the relationship between Deqi and the clinical efficacy of acupuncture. However, the underlying mechanisms of Deqi are complex and there is a lack of systematic summaries of objective quantitative studies of Deqi. Acupuncture Deqi can achieve the purpose of treating diseases by regulating the interaction of local and neighboring acupoints, brain centers, and target organs. At local and neighboring acupoints, Deqi can change their tissue structure, temperature, blood perfusion, energy metabolism, and electrophysiological indicators. At the central brain level, Deqi can activate the brain regions of the thalamus, parahippocampal gyrus, postcentral gyrus, insular, middle temporal gyrus, cingulate gyrus, etc. It also has extensive effects on the limbic-paralimbic-neocortical-network and default mode network. The brain mechanisms of Deqi vary depending on the acupuncture techniques and points chosen. In addition, Deqi 's mechanism of action involves correcting abnormalities in target organs. The mechanisms of acupuncture Deqi are multi-targeted and multi-layered. The biological mechanisms of Deqi are closely related to brain centers. This study will help to explore the mechanism of Deqi from a local-central-target-organ perspective and provide information for future clinical decision-making.

Periadventitial biomaterials to improve arteriovenous fistula and graft outcomes

Periadventitial biomaterials have been employed for nearly three decades to promote adaptive venous remodeling following hemodialysis vascular access creation in preclinical models and clinical trials. These systems are predicated on the combination of scaffolds, hydrogels, and/or particles with therapeutics (small molecules, proteins, genes, and cells) to prevent venous stenosis and subsequent maturation failure. Periadventitial biomaterial therapies have evolved from simple drug delivery vehicles for traditional drugs to more thoughtful designs tailored to the pathophysiology of access failure. The emergence of tissue engineering strategies and gene therapies are another exciting new direction. Despite favorable results in experimental and preclinical studies, no periadventitial therapy has been clinically approved to improve vascular access outcomes. After conducting an exhaustive review of the literature, we identify the seminal studies and clinical trials that utilize periadventitial biomaterials and discuss the key features of each biomaterial format and their respective shortcomings as they pertain to access maturation. This review provides a foundation from which clinicians, surgeons, biologists, and engineers can refer to and will hopefully inspire thoughtful, translatable treatments to finally address access failure.

Regulation of interstitial fluid flow in adventitia along vasculature by heartbeat and respiration

Converging studies showed interstitial fluid (ISF) adjacent to blood vessels flows in adventitia along vasculature into heart and lungs. We aim to reveal circulatory pathways and regulatory mechanism of such adventitial ISF flow in rat model. By MRI, real-time fluorescent imaging, micro-CT, and histological analysis, ISF was found to flow in adventitial matrix surrounded by fascia and along systemic vessels into heart, then flow into lungs via pulmonary arteries and back to heart via pulmonary veins, which was neither perivascular tissues nor blood or lymphatic vessels. Under physiological conditions, speckle-like adventitial ISF flow rate was positively correlated with heart rate, increased when holding breath, became pulsative during heavy breathing. During cardiac or respiratory cycle, each dilation or contraction of heart or lungs can generate to-and-fro adventitial ISF flow along femoral veins. Discovered regulatory mechanisms of adventitial ISF flow along vasculature by heart and lungs will revolutionize understanding of cardiovascular system.

Stimuli-induced NOergic Molecules and Neuropeptides Mediated Axon Reflexes Contribute to Tracers along Meridian Pathways

An abundance of studies from different international groups have demonstrated tracers along linear pathways resembling meridians over the body surface of humans. All experiments of the studies have been conducted by injection of a radiotracer solution or tracer dyes in a volume of solution into acupuncture points (acupoints). The solution injected into acupoints produces much stronger mechanical stimuli than acupuncture, which causes axon reflex. Anatomical studies have demonstrated that acupoints/meridians exist higher number of small nerve fibers and blood vessels with rich nitric oxide (NO) and neuropeptides in the cutaneous tissues as structures for the biomolecules mediated axon reflexes. Recent advances have determined that NO and calcitonin generelated peptides play crucial roles in the comprehension of the axon reflex. The stimuli-evoked axon reflex and NOergic biomolecules/neuropeptides increase local blood flow with higher levels in acupoints/meridians, which move radioactive substances or tracer dyes in the skin and subcutaneous tissue under a linear path resembling acupoints and meridians, the important phenomena of meridians induced by the stimuli. The evidence and understanding of the biomolecular processes of the tracers along linear pathways resembling meridians have been summarized with an emphasis on recent developments of NO and neuropeptides mediating stimuli-evoked axon reflexes to increase local blood flow with higher levels in acupoints/meridians, which move radioactive substances or tracer dyes in the skin and subcutaneous tissue contributing to tracers along linear pathways resembling meridians in this mini-review.

A robust MRI contrast agent for specific display of the interstitial stream

Experimental and clinical studies have reported phenomena of long-range fluid flow in interstitial space. However, its behaviours and functions are yet to be addressed. The imaging of the interstitial stream in vivo can clarify its transportation route and allow further understanding of physiological mechanisms and clinical relevance. Here to illustrate the route of the interstitial stream leading to the kidney, we design and synthesize a magnetic resonance imaging (MRI) contrast agent PAA-g-(DTPA-gadolinium). This MRI agent has a high longitudinal relaxivity for higher MRI contrast and large size to avoid leakage across the interstitial space. Using dynamic contrast enhanced MRI, histochemical staining, and trace element analysis of gadolinium, we track the nano-scale PAA-g-(DTPA-gadolinium) transported in the interstitial stream. The agent can be applied for a wide range of imaging and analysis of tissues and organs, thereby enabling advances in the fields of physiology, pathology, and pharmacology.

Pilot Study of Blood Perfusion Changes at PC4 and Its Surrounding Points Induced by Acupuncture and Moxibustion

Acupuncture and moxibustion are widely used in clinical practice; however, the differences between their mechanisms are unclear. In the present study, the response of blood perfusion resulting from acupuncture or moxibustion at Ximen (PC4) and its surrounding points was explored. Using the wavelet method, the differences in the frequency interval of blood flux were observed. Furthermore, the correlations between these points were analyzed. The results suggested that moxibustion could significantly improve blood flow perfusion at PC4 compared to acupuncture; however, there was no significant difference around PC4. The response of blood flux at PC4 to different stimulations was related to the frequency V (0.4–1.6 Hz) component. However, a difference in response at other points was not observed. Correlation analysis showed that both acupuncture and moxibustion could cause a decline in the correlation of blood flux signals at these recorded points, but there was no significant difference between these techniques. The results suggested that, at least in the forearm, the acupuncture or moxibustion only influenced the level of blood perfusion locally.

Layers of interstitial fluid flow along a "slit-shaped" vascular adventitia

Interstitial fluid (ISF) flow through vascular adventitia has been discovered recently. However, its kinetic pattern was unclear. We used histological and topographical identification to observe ISF flow along venous vessels in rabbits. By magnetic resonance imaging (MRI) in live subjects, the inherent pathways of ISF flow from the ankle dermis through the legs, abdomen, and thorax were enhanced by paramagnetic contrast. By fluorescence stereomicroscopy and layer-by-layer dissection after the rabbits were sacrificed, the perivascular and adventitial connective tissues (PACTs) along the saphenous veins and inferior vena cava were found to be stained by sodium fluorescein from the ankle dermis, which coincided with the findings by MRI. The direction of ISF transport in a venous PACT pathway was the same as that of venous blood flow. By confocal microscopy and histological analysis, the stained PACT pathways were verified to be the fibrous connective tissues, consisting of longitudinally assembled fibers. Real-time observations by fluorescence stereomicroscopy revealed at least two types of spaces for ISF flow: one along adventitial fibers and another one between the vascular adventitia and its covering fascia. Using nanoparticles and surfactants, a PACT pathway was found to be accessible by a nanoparticle of <100 nm and contained two parts: a transport channel and an absorptive part. The calculated velocity of continuous ISF flow along fibers of the PACT pathway was 3.6‒15.6 mm/s. These data revealed that a PACT pathway was a "slit-shaped" porous biomaterial, comprising a longitudinal transport channel and an absorptive part for imbibition. The use of surfactants suggested that interfacial tension might play an essential role in layers of continuous ISF flow along vascular vessels. A hypothetical "gel pump" is proposed based on interfacial tension and interactions to regulate ISF flow. These experimental findings may inspire future studies to explore the physiological and pathophysiological functions of vascular ISF or interfacial fluid flow among interstitial connective tissues throughout the body.

In Vivo Visualization of the Pericardium Meridian with Fluorescent Dyes

The anatomical basis of acupuncture meridians continues to be enigmatic. Although much attention has been placed on potential correlations with inter/intramuscular fascia or lower electrical impedance, animal studies performed in the past 40 years have shown that tracer dyes—specifically Tc-99m pertechnetate—injected at strategic skin points generate linear migrations closely aligning with acupuncture meridians. To evaluate whether this phenomenon is also observable in humans, we injected two fluorescent dyes—fluorescein sodium and indocyanine green (ICG)—into the dermal layer both at acupuncture points (PC5, PC6, and PC7) and a nonacupoint control. Fifteen healthy volunteers were enrolled in this study. Of the 19 trials of fluorescein injected at PC6, 15 (79%) were associated with slow diffusion of the dye proximally along a path matching closely with the pericardium meridian. Furthermore, the dye emerged and coalesced proximally at exactly acupoint PC3. Injections of ICG at the acupoints PC5, PC6, or PC7 showed a similar trajectory close to the injection site but diverged when migrating proximally, failing converge on acupoint PC3. Injections of either dye at an adjacent PC6-control did not generate any notable linear pathway. Both ultrasound imaging and vein-locating device did not reveal any corresponding vessels (arterial or venous) at the visualized tracer pathway but did demonstrate correlations with intermuscular fascia.

Active interfacial dynamic transport of fluid in a network of fibrous connective tissues throughout the whole body

Fluid in interstitial spaces accounts for ~20% of an adult body weight and flows diffusively for a short range. Does it circulate around the body like vascular circulations? This bold conjecture has been debated for decades. As a conventional physiological concept, interstitial space is a micron‐sized space between cells and vasculature. Fluid in interstitial spaces is thought to be entrapped within interstitial matrix. However, our serial data have further defined a second space in interstitium that is a nanosized interfacial transport zone on a solid surface. Within this fine space, fluid along a solid fibre can be transported under a driving power and identically, interstitial fluid transport can be visualized by tracking the oriented fibres. Since 2006, our data from volunteers and cadavers have revealed a long‐distance extravascular pathway for interstitial fluid flow, comprising at least four types of anatomic distributions. The framework of each extravascular pathway contains the longitudinally assembled and oriented fibres, working as a fibrorail for fluid flow. Interestingly, our data showed that the movement of fluid in a fibrous pathway is in response to a dynamic driving source and named as dynamotaxis. By analysis of previous studies and our experimental results, a hypothesis of interstitial fluid circulatory system is proposed.

Changes of Blood Flux at BL21 and Points along BL Meridian Resulted from Acupuncture or Moxibustion: Case Cross Design Study

Acupuncture (Acup) and moxibustion (Moxi) are commonly used interventions in clinical practice. However, the difference between Acup and moxibustion mechanisms is unclear. In current study, blood perfusion responses resulted from Acup or Moxi at Weishu acupoint (BL21) and control points were explored, respectively. The time series of blood flux signals at BL21 and control points were transformed with Morlet wavelet, and the differences in each frequency interval were observed. The results suggested that acupoint response to different stimulation is a comprehensive process which related to all components of blood perfusion signals. Whereas the different response at control points was not observed, there has been significant difference coherence value between Acup and Moxi stimulation. The results suggested the influence of Acup and Moxi not only on the level of blood perfusion at local area; the intrinsic relevance after stimulation which can be evaluated by coherence analysis is also an appropriate index to distinguish different stimulations.

Understanding Fibroblasts in Order to Comprehend the Osteopathic Treatment of the Fascia

The osteopathic treatment of the fascia involves several techniques, each aimed at allowing the various layers of the connective system to slide over each other, improving the responses of the afferents in case of dysfunction. However, before becoming acquainted with a method, one must be aware of the structure and function of the tissue that needs treating, in order to not only better understand the manual approach, but also make a more conscious choice of the therapeutic technique to employ, in order to adjust the treatment to the specific needs of the patient. This paper examines the current literature regarding the function and structure of the fascial system and its foundation, that is, the fibroblasts. These connective cells have many properties, including the ability to contract and to communicate with one another. They play a key role in the transmission of the tension produced by the muscles and in the management of the interstitial fluids. They are a source of nociceptive and proprioceptive information as well, which is useful for proper functioning of the body system. Therefore, the fibroblasts are an invaluable instrument, essential to the understanding of the therapeutic effects of osteopathic treatment. Scientific research should make greater efforts to better understand their functioning and relationships.

Acupoint Activation: Response in Microcirculation and the Role of Mast Cells

BACKGROUND

According to Traditional Chinese Medicine (TCM) theory, acupuncture effects are based on the integrity function of meridians. Meridians are thought to regulate body function through the normal flow of qi and/or blood. Disturbances in this flow are thought to cause disease, and acupuncture techniques are believed to cure disease by regulating this flow. However, it is still difficult to understand the exact meaning of qi and to evaluate the activation of meridians. Thus, more and more attention has been focused on the relationship of acupuncture and circulation.

METHODS

In this narrative review, the authors focus on the state of the art in acupoint activation, microcirculation response, and on investigation of mast cells, based on current literature research.

RESULTS

Altogether, 52 references are cited and discussed critically. A schematic diagram of the relationship between acupuncture stimulation, changes of microcirculation and mast cells is presented as result.

CONCLUSION

The block diagram presented in this review article shows that mast cells might play an important role in circulation response after acupoint stimulation.

Clinical and symptomatological reflections: the fascial system

Every body structure is wrapped in connective tissue, or fascia, creating a structural continuity that gives form and function to every tissue and organ. Currently, there is still little information on the functions and interactions between the fascial continuum and the body system; unfortunately, in medical literature there are few texts explaining how fascial stasis or altered movement of the various connective layers can generate a clinical problem. Certainly, the fascia plays a significant role in conveying mechanical tension, in order to control an inflammatory environment. The fascial continuum is essential for transmitting muscle force, for correct motor coordination, and for preserving the organs in their site; the fascia is a vital instrument that enables the individual to communicate and live independently. This article considers what the literature offers on symptoms related to the fascial system, trying to connect the existing information on the continuity of the connective tissue and symptoms that are not always clearly defined. In our opinion, knowing and understanding this complex system of fascial layers is essential for the clinician and other health practitioners in finding the best treatment strategy for the patient.

Pilot study of blood perfusion coherence along the meridian in forearm

Background

Many studies have explored the relationship between skin microcirculation and meridian activation. However, few studies have examined blood perfusion coherence along the meridians, and other studies have suggested that the skin vasodilator response relates to age. This study investigated blood perfusion coherence characteristics along the meridian of the forearm in healthy volunteers.

Methods

A total of 15 young subjects (25.53 ± 2.20) and 15 middle-aged subjects (50.07 ± 3.37) were recruited for this study. Before experiments, each subject was placed in a temperature-controlled room for 60 min. Skin blood perfusion from five points was recorded simultaneously using a full-field laser perfusion imager before and after inflatable occlusion. The five points comprised three points located on the pericardium meridian, and two points from different locations. Coherence analysis between these points was performed at different frequency intervals from 0.0095 to 2 Hz.

Results

In young subjects, the coherence value was unchanged before and after occlusion, and there was no significant difference in coherence value between meridian-meridian points (M-M) and meridian-parameridian points (M-P). In middle-aged subjects, the coherence value increased significantly in both M-M and M-P at frequency intervals of 0.14-0.4 Hz, 0.4-1.6 Hz, and 1.6-2 Hz. However, there was no significant difference in coherence values between M-M and M-P.

Conclusions

Inflatable occlusion can increase middle-aged subjects’ blood perfusion coherence value of the forearm. However, there is no specificity in meridian location.

[Lymphatic vascular system, development and lymph formation. Review]

The lymphatic vascular system is widely developed among vertebrates. Lymphatic vessels provide the interstitial fluid (20% of the body weight) drainage through interstitial prelymphatic channels, capillaries, precollectors and collectors flowing into the venous blood. Endothelial cells of capillaries are overlapped and fixed to interstitial collagen and elastic fibres by anchoring filaments facilitating the fluid transfer. Precollectors and collectors have valves controlling the lymph flux direction. In addition to external mechanisms, the lymphangions of collectors have contracting muscle cells driving the flow. Lymphatic endothelial cells are routinely identified by the expression of podoplanin, LYVE-1 and VEGFR3. In the embryo, prelymphatic endothelial cells emerge from the cardinal veins and migrate into the mesenchyma forming embryonic lymphatic sacs. Prox1, Sox18 and COUP-TFII play a major role in the endothelial speciation, VEGFC as VEGFD combined to VEGFR3 in cell migration and proliferation and FoxC2 in valves development. In cancer or inflammation, various factors secreted by cancer cells and/or inflammatory cells induce a neolymphangiogenesis. Recently it has been shown that cells from the bone marrow could be potential precursors for lymphatic endothelial cells.