Direct current electric field regulates endothelial permeability under physiologically relevant fluid forces in a microfluidic vessel bifurcation model

A review of the evidence to support electrical stimulation-induced vascularization in engineered tissue

Tissue engineering presents a promising solution for regenerative medicine and the success depends on the supply of oxygen/nutrients to the cells by rapid vascularization. More and more technologies are being developed to facilitate vascularization of engineered tissues. In this review, we indicated that a regulatory system which influences all angiogenesis associated cells to achieve their desired functional state is ideal for the construction of vascularized engineered tissues in vitro. We presented the evidence that electrical stimulation (ES) enhances the synergistic promotion of co-cultured angiogenesis associated cells and its potential regulatory mechanisms, highlighted the potential advantages of a combination of mesenchymal stem cells (MSCs), endothelial cells (ECs) and ES to achieve tissue vascularization, with particular emphasis on the different biological pathways of ES-regulated ECs. Finally, we proposed the future direction of using ES to reconstruct engineered tissue blood vessels, pointed out the potential advantages and disadvantages of ES application on tissue vascularization.

Development of Silk Fibroin Scaffolds for Vascular Repair

Silk fibroin (SF) is a biocompatible natural protein with excellent mechanical characteristics. SF-based biomaterials can be structured using a number of techniques, allowing the tuning of materials for specific biomedical applications. In this study, SF films, porous membranes, and electrospun membranes were produced using solvent-casting, salt-leaching, and electrospinning methodologies, respectively. SF-based materials were subjected to physicochemical and biological characterizations to determine their suitability for tissue regeneration applications. Mechanical analysis showed stress-strain curves of brittle materials in films and porous membranes, while electrospun membranes featured stress-strain curves typical of ductile materials. All samples showed similar chemical composition, melting transition, hydrophobic behavior, and low cytotoxicity levels, regardless of their architecture. Finally, all of the SF-based materials promote the proliferation of human umbilical vein endothelial cells (HUVECs). These findings demonstrate the different relationship between HUVEC behavior and the SF sample's topography, which can be taken advantage of for the design of vascular implants.

Human dermal microvascular endothelial cell morphological response to fluid shear stress

As the cells that line the vasculature, endothelial cells are continually exposed to fluid shear stress by blood flow. Recent studies suggest that the morphological response of endothelial cells to fluid shear stress depends on the endothelial cell type. Thus, the present study characterizes the morphological response of human dermal microvascular endothelial cells (HMEC-1) and nuclei to steady, laminar, and unidirectional fluid shear stress. Cultured HMEC-1 monolayers were exposed to shear stress of 0.3 dyn/cm², 16 dyn/cm², or 32 dyn/cm² for 72 h with hourly live-cell imaging capturing both the nuclear and cellular morphology. Despite changes in elongation and alignment occurring with increasing fluid shear stress, there was a lack of elongation and alignment over time under each fluid shear stress condition. Conversely, changes in cellular and nuclear area exhibited dependence on both time and fluid shear stress magnitude. The trends in cellular morphology differed at shear stress levels above and below 16 dyn/cm², whereas the nuclear orientation was independent of fluid shear stress magnitude. These findings show the complex morphological response of HMEC-1 to fluid shear stress.

Electroceutical treatment of infected chronic wounds in a dog and a cat

OBJECTIVES

To describe the use of an innovative printed electroceutical dressing (PED) to treat non-healing, infected chronic wounds in one dog and one cat and report outcomes.

ANIMALS

A 4-year-old female spayed Mastiff and a 1-year-old female spayed domestic shorthair cat.

STUDY DESIGN

Short case series.

METHODS

Both cases had chronic wounds (duration: approximately 1 year for the dog and 6 3/4 months for the cat) that remained open and infected despite various wound management strategies. Both animals were treated with the PED. Observations from the records regarding wound size, antimicrobial susceptibility, and the time to healing were recorded.

RESULTS

After 10 days of PED treatment in the dog and 17 days of PED treatment in the cat, the wounds had decreased in size by approximately 4.2 times in the dog and 2.5 times in the cat. Culture of punch biopsies yielded negative results. Wounds were clinically healed at 67 days in the dog and 47 days in the cat. No further treatment of the wounds was required beyond that point.

CONCLUSION

Application of a PED led to closure of two chronic wounds and resolution of their persistent infection.

CLINICAL SIGNIFICANCE

PEDs may provide a new treatment modality to mitigate infection and promote healing of chronic wounds.

Endothelial barrier function is co-regulated at vessel bifurcations by fluid forces and sphingosine-1-phosphate

Sphingosine-1-phosphate (S1P) is a bioactive sphingolipid mediator of endothelial barrier function. Prior studies have implicated mechanical stimulation due to intravascular laminar shear stress in co-regulating S1P signaling in endothelial cells (ECs). Yet, vascular networks in vivo consist of vessel bifurcations, and this geometry generates hemodynamic forces at the bifurcation point distinct from laminar shear stress. However, the role of these forces at vessel bifurcations in regulating S1P-dependent endothelial barrier function is not known. In this study, we implemented a microfluidic platform that recapitulates the flow dynamics of vessel bifurcations with in situ quantification of the permeability of microvessel analogues. Co-application of S1P with impinging bifurcated fluid flow, which is characterized by approximately zero shear stress and 38 dyn•cm-2 stagnation pressure at the vessel bifurcation point, promotes vessel stabilization. Similarly, co-treatment of S1P with 3 dyn•cm-2 laminar shear stress is also protective of endothelial barrier function. Moreover, it is shown that vessel stabilization due to bifurcated fluid flow and laminar shear stress is dependent on S1P receptor 1 or 2 signaling. Collectively, these findings demonstrate the endothelium-protective function of fluid forces at vessel bifurcations and their involvement in coordinating S1P-dependent regulation of vessel permeability.