Characterization of cerebrovascular changes in Alzheimer's disease mice by photoacoustic imaging

The cerebral vasculature plays a significant role in the development of Alzheimer's disease(AD),however,the specific association between them remains unclear.In this paper,based on the benefits of photoacoustic imaging(PAI),including label-free,high-resolution,in vivo imaging of vessels,we investigated the structural changes of cerebral vascular in wild-type(WT)mice and AD mice at different ages,analyzed the characteristics of the vascular in different brain regions,and correlated vascular characteristics with cognitive behaviors.The results showed that vascular density and vascular branching index in the cortical and frontal regions of both WT and AD mice decreased with age.Meanwhile,vascular lacunarity increased with age,and the changes in vascular structure were more pronounced in AD mice.The trend of vascular dysfunction aligns with the worsening cognitive dysfunction as the disease progresses.Here,we utilized in vivo PAI to analyze the changes in vascular structure during the progression of AD,elucidating the spatial and temporal correlation with cognitive impairment,which will provide more intuitive data for the study of the correlation between cerebrovascular and the development of AD.

Constructal entransy dissipation rate minimization for X-shaped vascular networks

Combining with entransy theory, constructal designs of the X-shaped vascular networks(XSVNs) are implemented with fixed total tube volumes of the XSVNs. The entransy dissipation rates(EDRs) of the XSVNs are minimized, and the optimal constructs of the XSVNs are derived. Comparison of the optimal constructs of the XSVNs with two optimization objectives(EDR minimization and entropy generation rate(EGR) minimization) is conducted. It is found that when the dimensionless mass flow rate(DMFR) is small, the optimal diameter ratio of the elemental XSVN derived by EDR minimization is different from that derived by EGR minimization. For the multilevel XSVN, when the DMFR is 100, compared the XSVN with the corresponding H-shaped vascular network(HSVN), the dimensionless EDRs of the elemental, second and fourth order XSVNs are reduced by 26.39%, 15.34% and 9.81%, respectively. Compared with the entransy dissipation number(EDN) of the second order XSVN before angle optimization, the EDN after optimization is reduced by 26.15%, which illustrates that it is significant to conduct angle optimization of the XSVN. Entransy theory is applied into the constructal design of the vasculature with heat transfer and fluid flow in this paper, which provides new directions for the vasculature designs.

Cellular fluidic-based vascular networks for tissue engineering

Artificial organs are devices implanted into the living body as a substitute for damaged or diseased organs.Current efforts focus on the construction of fully functionalized artificial tissues/organs with vascular networks.Although engineering efforts have been made in creating artificial vessels with simple or complex configurations,building vascular networks with hierarchical architectures approximating native counterparts remains challenging.Herein,we give a perspective of cellular fluidics-based construction of vascular networks for tissue engineering,with inspirations drawn from a novel concept of 3D fluidic control platform based on unit-cell constructs.Through architected design of the unit cells,it enables programmed control over gas-liquid-solid interfaces and fluid flow processes in open-cell structures.This cellular-fluidics concept and the associated platform provide lots of inspirations for constructing artificial vascular networks.We believe that cellular fluidics opens a new avenue for fluid control and deterministic delivery,and would find vast opportunities in tissue engineering.

Polarity, Continuity, and Alignment in Plant Vascular Strands

Plant vascular cells are joined end to end along uninterrupted lines to connect shoot organs with roots;vascular strands are thus polar, continuous, and internally aligned. What controls the formation of vascular strands with these properties？ The “auxin canalization hypothesis”-based on positive feedback between auxin flow through a cell and the cell’s capacity for auxin transport-predicts the selection of continuous files of cells that transport auxin polarly, thus accounting for the polarity and continuity of vascular strands. By contrast, polar, continuous auxin transport-though required-is insufficient to promote internal alignment of vascular strands, implicating additional factors. The auxin canalization hypothesis was derived from the response of mature tissue to auxin application but is consistent with molecular and cellular events in embryo axis formation and shoot organ development. Objections to the hypothesis have been raised based on vascular organizations in callus tissue and shoot organs but seem unsupported by available evidence. Other objections call instead for further research; yet the inductive and orienting influence of auxin on continuous vascular differentiation remains unique.

Preparation and Endothelialization of Multi-level Vessel-like Network in Enzymated Gelatin Scaffolds

Loss of function of large tissues is an urgent clinical problem. Although the artificial microfluidic network fabricated in large tis- sue-engineered constructs has great promise, it is still difficult to develop an efficient vessel-like design to meet the requirements of the biomimetic vascular network for tissue engineering applications. In this study, we used a facile approach to fabricate a branched and multi-level vessel-like network in a large muscle scaffolds by combining stereolithography （SL） technology and enzymatic crosslinking mechanism. The morphology of microchannel cross-sections was characterized using micro-computed tomography. The square cross-sections were gradually changed to a seamless circular microfluidic network, which is similar to the natural blood vessel. In the different micro-channels, the velocity greatly affected the attachment and spread of Human Umbilical Vein Endothelial Cell （HUVEC）-Green Fluorescent Protein （GFP）. Our study demonstrated that the branched and multi-level microchannel network simulates biomimetic microenvironments to promote endothelialization. The gelatin scaffolds in the circular vessel-like networks will likely support myoblast and surrounding tissue for clinical use.