Tissue-engineered vascular grafts that are based on reconstituted extracellular matrices have been plagued by weak mechanical strength that prevents handling or anastomosis to native vessels. In this study, we devise a method for making dense, suturable collagen tubular constructs of diameter £1 mm for potential microsurgical applications, by dehydrating tubes of native rat tail type I collagen and crosslinking them with 20 mM genipin. Crosslinked dense collagen tubes with 1 mm inner diameter yielded ultimate tensile strength of 342 -15 gF and burst pressure of 1313 -156 mm Hg, comparable to the strength of a rat femoral artery, and supported endothelial cell adhesion and growth. End-to-end anastomosis of 0.5-mm-diameter tubes to explanted arteries displayed anastomotic strength of 82 -21 gF, which is sufficient for surgical applications. In vivo implantation of cell-free tubes as interpositional grafts in the rat femoral circulation yielded stable anastomosis with blood flow for 20 min. Seeded dense collagen tubes represent a promising alternative to venous graft that can potentially be used to bridge between short artery stubs in replantation surgeries.

Current methods to treat large soft-tissue defects mainly rely on autologous transfer of adipocutaneous flaps, a method that is often limited by donor site availability. Engineered vascularized adipose tissues can potentially be a viable and readily accessible substitute to autologous flaps. In this study, we engineered a small-scale adipose tissue with pre-patterned vasculature that enables immediate perfusion. Vessels formed after one day of perfusion and displayed barrier function after three days of perfusion. Under constant perfusion, adipose tissues remained viable and responded to lipoactive hormones insulin and epinephrine with lipid accumulation and loss, respectively. Adipocyte growth correlated inversely with distance away from the feeding vessel, as predicted by a Krogh-type model.

Although much progress has been made in engineering vascular grafts for large‐ and small‐diameter arterial repair or bypass, the extension of these results to the microsurgical size scale has been challenging. Here, we evaluated the use of dense collagen tubes (outer diameter 1 mm, inner diameter 0.5 mm) for vascular microsurgery as interpositional grafts to the femoral artery of Lewis rats. These tubes were formed by dehydrating tubular collagen gels around a mandrel, crosslinking them with genipin, seeding with syngeneic endothelial cells, and culturing before implantation by suture anastomosis. The retention of a confluent endothelial lining inside the tubes after mock surgical handling depended strongly on the crosslinker concentration and culture time. Optimized preparation conditions enabled retention of endothelium after mock surgical handling in ~80% of tubes and maintenance of patency 7 days after implantation in ~40% of grafts. Histological analysis showed the development of granulation tissue and the presence of CD31‐positive structures on the inner and outer surfaces of implants. This study provides a proof‐of‐principle demonstration that endothelialized dense collagen tubes can remain patent for up to 7 days after vascular microsurgery, and points to the importance of mild scaffold crosslinking for maintaining firm endothelial adhesion.

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Background Intensive farming practices have gradually shifted from traditional grazing to housing for horses in China, changing from a single forage diet to a more comprehensive mixed diet. Grains as the primary source of energy for horses under intensive farming conditions, play a critical role in their growth, development, and health. However, there is a considerable variation in glucose production based on the different sources of dietary grains and starch content, proportions, and structures. Thus, it is crucial to choose a suitable grain as a source of energy for horses at various stages of growth.The study aimed to investigate the effects of different diets of steam-pressed flaked grains (corn, oats, and barley) on nutrient digestibility, blood glucose metabolism, and fecal volatile fatty acids (VFA) content in weaned foals of Kazakh horses. Male Kazakh horse foals (n = 18) weaned at the age of 5 months were randomly divided into three groups (n = 6 each) based on the different grains in the diet: corn group (CG), oats group (OG), and barley group (BG). The amount of concentrate supplement fed to the foals was determined based on the presence of equal starch in the concentrate. The results showed that the apparent digestibility of all nutrients was lower in the OG than in the CG and BG. The amylose intake and digestibility were higher in the OG than in CG. Blood glucose concentration and glucagon levels were higher in the CG than in OG and BG. The insulin/glucose ratio was higher in the BG than in the CG and OG; BG increased the fecal lactic acid and total VFA (TVFA) levels in foals and reduced the fecal pH, respectively. Results The results showed that the amylose intake and digestibility were higher in the OG than in CG. Blood glucose concentration and glucagon levels were higher in the CG than in OG and BG. The insulin/glucose ratio was higher in the BG than in the CG and OG; BG increased the fecal lactic acid and total VFA (TVFA) levels in foals and reduced the fecal pH, respectively. Conclusions In this study, Feeding corn increases the blood glucose concentration in weaned foals, is efficient in sugar production and promotes glucagon secretion in foals; Oats and barley increased the digestibility of amylose in feed significantly. Feeding barley improves blood insulin sensitivity in foals and can increase the concentration of lactic acid in faeces. By comparing the digestive physiology of three grains in weaned foals, choosing the best grains for weaning foals and scientifically formulating the diet of weaning foals could improve the digestion and absorption of nutrients, promoting growth and development.

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