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

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.

Intervaginal space injection of photothermal chemotherapy nanoparticles for facilitating tumor targeting and improving outcomes in mice

Although numerous photothermal nanoparticles have been designed to improve the enhanced and permeability and retention (EPR) effect, the delivery of nanoparticles to the tumor site remains a major obstacle in cancer treatment. The interstital structure and its internal fluid that play an important role in material transmission, intercellular signal transduction, tissue morphology, immunity, tumor development, and disease diagnosis and treatment may be considered as a new route for drug delivery. Here, we prepared a nanoplatform composed of polydopamine (PDA), indocyanine green (ICG) as a photothermal agent, and paclitaxel (PTX) as a chemotherapeutic drug. The designed PDA-ICG nanoparticles displayed excellent photothermal conversion ability, with the synergistic effect of PTX, the growth of MDA-MB-231 cells was significantly suppressed with the cell viability of 6.19% in vitro. Taking advantage of bioimaging ability of ICG, tumor-targeting of the nanoparticles injected into the interstitial space was study, Compared with intravenous injection, nanoparticles better targeted the tumor based on the interstitial fluid flow in MBA-MD-231 bearing mice. Furthermore, the antitumor efficacy was studied in vivo. With the improved accumulation of PDA-ICG-PTX nanoparticles injected into the interstitial space and the synergistic effect of photothermal therapy and chemotherapy, tumor growth was inhibited without obvious side effects. These results demonstrated that interstitial space injection may be a superior administration route for tumor-targeting nanoparticles. The PDA-ICG-PTX nanoparticles delivered via the interstitial space exhibit great potential in the photothermal chemotherapy of cancers.

Biomaterials and bioelectronics for self-powered neurostimulation

Self-powered neurostimulation via biomaterials and bioelectronics innovation has emerged as a compelling approach to explore, repair, and modulate neural systems. This review examines the application of self-powered bioelectronics for electrical stimulation of both the central and peripheral nervous systems, as well as isolated neurons. Contemporary research has adeptly harnessed biomechanical and biochemical energy from the human body, through various mechanisms such as triboelectricity, piezoelectricity, magnetoelasticity, and biofuel cells, to power these advanced bioelectronics. Notably, these self-powered bioelectronics hold substantial potential for delivering neural stimulations that are customized for the treatment of neurological diseases, facilitation of neural regeneration, and the development of neuroprosthetics. Looking ahead, we expect that the ongoing advancements in biomaterials and bioelectronics will drive the field of self-powered neurostimulation toward the realization of more advanced, closed-loop therapeutic solutions, paving the way for personalized and adaptable neurostimulators in the coming decades.

Interstitial Fluid Flows along Perivascular and Adventitial Clearances around Neurovascular Bundles

This study reports new phenomena of the interstitial fluid (ISF) microflow along perivascular and adventitial clearances (PAC) around neurovascular bundles. The fluorescent tracing was used to observe the ISF flow along the PAC of neurovascular bundles in 8-10 week old BALB/c mice. The new results include: (1) the topologic structure of the PAC around the neurovascular bundles is revealed; (2) the heart-orientated ISF flow along the PAC is observed; (3) the double-belt ISF flow along the venous adventitial clearance of the PAC is recorded; (4) the waterfall-like ISF flow induced by the small branching vessel or torn fascia along the PAC is discovered. Based on the above new phenomena, this paper approached the following objectives: (1) the kinematic laws of the ISF flow along the PAC around neurovascular bundles are set up; (2) the applicability of the hypothesis on the PAC and its subspaces by numerical simulations are examined. The findings of this paper not only enriched the image of the ISF flow through the body but also explained the kernel structure of the ISF flow (i.e., the PAC). It helps to lay the foundation for the kinematics and dynamics of the ISF flow along the PAC around neurovascular bundles.

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 Situ Self-Organizing Materials for Local Stress-Responsive Reconstruction of Skin Interstitium

Remodeling of the fibrous network in the skin interstitium is a crucial step in the process of skin wound healing. In the present study, a hierarchically structured xanthan gum-chitosan (XG-CS) composite hydrogel is developed as a skin wound healing material that responds to stress at wound sites by in situ self-organizing and self-repairing the interstitial fibrous network. The composite gel adheres tightly to the injured fibers forming an intact interstitial pathway, and thereby promotes the physiological function of fibroblasts. A software-based quantitative assessment is performed to evaluate the stress state at wound sites, which confirms that the composite gel adapted in vivo to wound stress and ultimately promotes fast wound healing. The results highlight the importance of interstitial reconstruction in tissue recovery, and will inspire novel strategies in regenerative medicine.

The Shape and Function of Solid Fascias Depend on the Presence of Liquid Fascias

Scientific research is not a showcase of his own talent or own resources, it is a chance to improve common knowledge on certain topics for the collective well-being. A researcher should use multidisciplinarity to observe a phenomenon in its entirety and not only its alignment of thought, federations, committees, and knowledge; to get to understand it is necessary to exploit more tools and more disciplines. The article discusses the importance of the fluids (or liquid fascia) in maintaining the shape and function of the human body, as, currently, many texts forget how much body fluids are fundamental for understanding structural dynamics (bones and muscles, fibrils, and cells). By revisiting the current literature, the text wishes to highlight how the liquid fascia determines body adaptation in the presence of mechanical stress. Without fluids, there would be no body shape that we know.