Direct imaging of capillaries reveals the mechanism of arteriovenous interlacing in the chick chorioallantoic membrane

Angiogenesis Dynamics: A Computational Model of Intravascular Flow Within a Structural Adaptive Vascular Network

BACKGROUND

Understanding vascular development and the key factors involved in regulating angiogenesis-the growth of new blood vessels from pre-existing vasculature-is crucial for developing therapeutic approaches to promote wound healing. Computational techniques offer valuable insights into improving angiogenic strategies, leading to enhanced tissue regeneration and improved outcomes for chronic wound healing. While chorioallantoic membrane (CAM) models are widely used for examining fundamental mechanisms in vascular development, they lack quantification of essential parameters such as blood flow rate, intravascular pressure, and changes in vessel diameter.

METHODS

To address this limitation, the current study develops a novel two-dimensional mathematical model of angiogenesis, integrating discrete and continuous modelling approaches to capture intricate cellular interactions and provide detailed information about the capillary network's structure. The proposed hybrid meshless-based model simulates sprouting angiogenesis using the in vivo CAM system.

RESULTS

The model successfully predicts the branching process with a total capillary volume fraction deviation of less than 15% compared to experimental data. Additionally, it implements blood flow through the capillary network and calculates the distribution of intravascular pressure and vessel wall shear stress. An adaptive network is introduced to consider capillary responses to hemodynamic and metabolic stimuli, reporting structural diameter changes across the generated vasculature network. The model demonstrates its robustness by verifying numerical outcomes, revealing statistically significant differences with deviations in key parameters, including diameter, wall shear stress (p < 0.05), circumferential wall stress, and metabolic stimuli (p < 0.01).

CONCLUSION

With its strong predictive capability in simulating intravascular flow and its ability to provide both quantitative and qualitative assessments, this research enhances our understanding of angiogenesis by introducing a biologically relevant network that addresses the functional demands of the tissue.

Electrical stimulation of chicken embryo development supports the Inside story scenario of human development and evolution

Animal evolution is driven by random mutations at the genome level. However, it has long been suggested that there exist physical constraints which limit the set of possible outcomes. In craniate evolution, it has been observed that head features, notably in the genus homo, can be ordered in a morphological diagram such that, as the brain expands, the head rocks more forward, face features become less prognathous and the mouth tends to recede. One school of paleontologists suggests that this trend is wired somewhere structurally inside the anatomy, and that random modifications of genes push up or down animal forms along a pre-determined path. No actual experiment has been able to settle the dispute. I present here an experiment of electric stimulation of the head in the chicken embryo which is able to enhance the magnitude of tension forces during development. This experimental intervention causes a correlated brain shrinkage and rotatory movement of the head, congruent with tissue texture, which proves that head dilation and flexure are intimately linked. Numerical modelling explains why the brain curls when it dilates. This gives support to the idea that there exists, in the texture of the vertebrate embryo, a latent dynamic pattern for the observed paleontological trends in craniates towards homo, a concept known as Inside story.

Development of a novel microfluidic perfusion 3D cell culture system for improved neuronal cell differentiation

Three-dimensional (3D) cell cultures have recently gained popularity in the biomedical sciences because of their similarity to the in vivo environment. SH-SY5Y cells, which are neuronal cells and are commonly used to investigate neurodegenerative diseases, have particularly been reported to be differentiated as neuron-like cells expressing neuron-specific markers of mature neurons in static 3D culture environments when compared to static 2D environments, and those in perfusion environments have not yet been investigated. Microfluidic technology has provided perfusion environment which has more similarity to in vivo through mimicking vascular transportation of nutrients, but air bubbles entering into microchannels drastically increase instability of the flow. Furthermore, static incubation commonly used is incompatible with perfusion setup due to its air conditions, which is a critical huddle to the biologists. In the present study, we developed a novel microfluidic perfusion 3D cell culture system that overcomes the disturbance from air bubbles and intuitionally sets the incubation with the perfusion 3D culture. The system is capable of generating concentration gradients between 5 and 95% and air bubble traps were included to increase stability during incubation by collecting air bubbles. To evaluate the perfusion 3D culture, SH-SY5Y differentiation was examined in static 2D, static 3D, and perfusion 3D cultures. Our system supported significantly increased clustering of SH-SY5Y compared to static 2D and 3D methods, as well as increasing neurite growth rate. This novel system therefore supports differentiation of SH-SY5Y and can be used to more accurately model the in vivo environment during cell culture experiments.

Coalescent angiogenesis-evidence for a novel concept of vascular network maturation

Angiogenesis describes the formation of new blood vessels from pre-existing vascular structures. While the most studied mode of angiogenesis is vascular sprouting, specific conditions or organs favor intussusception, i.e., the division or splitting of an existing vessel, as preferential mode of new vessel formation. In the present study, sustained (33-h) intravital microscopy of the vasculature in the chick chorioallantoic membrane (CAM) led to the hypothesis of a novel non-sprouting mode for vessel generation, which we termed "coalescent angiogenesis." In this process, preferential flow pathways evolve from isotropic capillary meshes enclosing tissue islands. These preferential flow pathways progressively enlarge by coalescence of capillaries and elimination of internal tissue pillars, in a process that is the reverse of intussusception. Concomitantly, less perfused segments regress. In this way, an initially mesh-like capillary network is remodeled into a tree structure, while conserving vascular wall components and maintaining blood flow. Coalescent angiogenesis, thus, describes the remodeling of an initial, hemodynamically inefficient mesh structure, into a hierarchical tree structure that provides efficient convective transport, allowing for the rapid expansion of the vasculature with maintained blood supply and function during development.