Biology subjects

Padmanaban, P.

Publications and source records attributed to Padmanaban, P..

5 recordsLinked to original sources

bioRxiv2024

Shape that matters: Yolk geometry spatially modulates developing vascular networks within chick chorioallantoic membrane

Controlling the multiscale organization of vasculature within diverse geometries is essential for shaping tissue-specific and organ-specific architectures. Nevertheless, how geometrical characteristics of surrounding tissues influence vessel morphology and blood flow remains unclear. Where the regulation of vascular organization by mechanical signals associated with fluid flow is well known, this study postulates that the organization of developing vasculature can also be regulated by mechanical signals connected to the confinement and thus the deformation of surrounding tissues. To test the Shape-Induced Vascular Adaptation (SIVA) concept, fertilized chicken egg contents containing developing vasculature were cultured within engineered eggshell platforms of different shapes. Our findings demonstrate that the vascularized chick chorioallantoic membrane (CAM) adapts to the shape of engineered eggshell, long before reaching its boundaries. This adaptation affects the organization of the vascular network within the CAM, affecting parameters such as vessel area, branching, orientation, length, diameter and endpoints. Specifically, we observed that sharp corners in the engineered eggshell led to more elongated vascular structures. To further explore the dynamic nature of this phenomenon, a proof-of-concept experiment was performed using a shape-shifting engineered eggshell that deforms the egg content from circle to square shape. Using this shape-shifting prototype, we observed a direct effect of eggshell deformation on the vessel morphology and flow dynamics in a time-dependent manner. Overall, our exovo experimental platform provides a unique opportunity to study how mechanical stimuli such as shape influence the spatial and temporal organization of developing vascularized tissues. By subjecting these tissues to various static and dynamic conditions, we induced both local and global changes in their organization. This class of perturbation provides us with an additional tool which can be used for shaping vascular organization within developing tissues and to engineer tissues with geometrically tunable vessel structures.

bioengineering↗

bioRxiv2024

Bioprinting of aptamer-based programmable bioinks to modulate multiscale microvascular morphogenesis in 4D

Dynamic growth factor presentation influences how individual endothelial cells assemble into complex vascular networks. Here, we developed programmable bioinks that facilitate dynamic VEGF presentation to guide vascular morphogenesis within 3D-bioprinted constructs. We leveraged aptamers high affinity for rapid VEGF sequestration in spatially confined regions and utilized aptamer-complementary sequence (CS) hybridization to tune VEGF release kinetics temporally, days after bioprinting. We show that spatial resolution of programmable bioink, combined with CS-triggered VEGF release, significantly influences alignment, organization, and morphogenesis of microvascular networks in bioprinted constructs. The presence of aptamer-tethered VEGF and the generation of instantaneous VEGF gradients upon CS-triggering restricted hierarchical network formation to the printed aptamer regions at all spatial resolutions. Network properties improved as the spatial resolution decreased, with low-resolution designs yielding the highest network properties. Specifically, CS-treated low-resolution designs exhibited significant vascular network remodeling, with increase in vessel density(1.35-fold), branching density(1.54-fold), and average vessel length(2.19-fold) compared to non-treated samples. Our results suggests that CS acts as an external trigger capable of inducing time-controlled changes in network organization and alignment on-demand within spatially localized regions of a bioprinted construct. We envision that these programmable bioinks will open new opportunities for bioengineering functional, hierarchically self-organized vascular networks within engineered tissues.

bioengineering↗

bioRxiv2024

Switching to external flows: perturbations of developing vasculature within chicken chorioallantoic membrane

The impact of fluid flow shear stresses, generated by the movement of blood through vasculature, on the organization and maturation of vessels is widely recognized. Nevertheless, it remains uncertain whether external fluid flows outside of the vasculature in the surrounding tissue can similarly play a role in governing these processes. In this research, we introduce an innovative technique called superfusion-induced vascular steering (SIVS). SIVS involves the controlled imposition of external fluid flow patterns onto the vascularized chick chorioallantoic membrane (CAM), allowing us to observe how this impacts the organization of vascular networks. To investigate the concept of SIVS, we conducted superfusion experiments on the intact chick CAM cultured within engineered eggshell system, using phosphate buffered saline (PBS). To capture and analyze the effects of superfusion, we employed a custom-built microscopy setup, enabling us to image both superfused and non-superfused regions within the developing CAM. This study provides valuable insights into the practical application of fluid superfusion within an in vivo context, shedding light on its significance for understanding tissue development and manipulation in an engineering setting.

bioengineering↗

bioRxiv2023

Flow in fetoplacental microvessels in vitro enhances perfusion, barrier function, and matrix stability

Proper placental vascularization is vital for pregnancy outcomes, but assessing it with animal models and human explants has limitations. Here, we present a 3D in vitro model of human placenta terminal villi that includes fetal mesenchyme and vascular endothelium. By co-culturing HUVEC, placental fibroblasts, and pericytes in a macro-fluidic chip with a flow reservoir, we generate fully perfusable fetal microvessels. Pressure-driven flow is crucial for the growth and remodeling of these microvessels, resulting in early formation of interconnected placental vascular networks and maintained viability. Computational fluid dynamics simulations predict shear forces, which increase microtissue stiffness, decrease diffusivity and enhance barrier function as shear stress rises. Mass-spec analysis reveals the deposition of numerous extracellular proteins, with flow notably enhancing the expression of matrix stability regulators, proteins associated with actin dynamics, and cytoskeleton organization. Our model provides a powerful tool for deducing complex in vivo parameters, such as shear stress on developing vascularized placental tissue, and holds promise for unraveling gestational disorders related to the vasculature.

bioengineering↗

bioRxiv2023

Mammary microvessels are sensitive to menstrual cycle sex hormones

The mammary gland is a highly vascularized organ that is influenced by sex hormones including estrogen (E2) and progesterone (P4). Beyond whole-organism studies in rodents or 2D monocultures, hormonal interactions and their effects on the breast microvasculature remains largely understudied. Recent methods to generate 3D microvessels on-chip have enabled direct observation of complex vascular processes; however, these models often use non-tissue-specific cell types, such as HUVEC and fibroblasts from various sources. Here, novel mammary-specific microvessels are generated by co-culturing primary breast endothelial cells and fibroblasts under optimized culture conditions. These microvessels are mechano-sensitive (to interstitial flow) and require endothelial-stromal interactions to develop fully perfusable vessels. These mammary-specific microvessels are also responsive to exogenous stimulation by sex hormones. When treated with combined E2 and P4, corresponding to the four phases of the menstrual cycle (period, follicular, ovular, and luteal), vascular remodeling and barrier function are altered in a phase-dependent manner. The presence of high E2 (ovulation) promotes vascular growth and remodeling, corresponding to high depletion of proangiogenic factors, whereas high P4 concentrations (luteal) promote vascular regression. The effects of combined E2 and P4 hormones are not only dose-dependent but also tissue-specific, as is shown by similarly treating non-tissue-specific HUVEC microvessels.

bioengineering↗