Mini ventricle
It is very difficult to get a model of a contracting heart. The researchers tried different methods: some connected cadaveric hearts to artificial circulation machines to make them contract, others attached special springs to the in vitro-grown heart muscle to observe how it expands and contracts. Each approach has its drawbacks: "reanimated" hearts can only beat for a few hours, while springs do not reproduce the forces acting on a real muscle.
A group of engineers, biologists and geneticists led by Christos Mijas from Boston University has developed a new way of modeling: they created a heart chamber on a microfluidic chip from a combination of nanoengineered acrylic components and living human heart tissue grown from induced pluripotent stem cells. The device can give researchers a more accurate idea of how the organ works, allowing, for example, to track the embryonic development of the heart, study pathological changes or evaluate the potential effectiveness and side effects of new treatments. Precision unidirectional Microfluidic Pump (Precision-enabled Unidirectional Microfluidic Pump), or miniPUMP, can also become a prototype for models of other organs, from lungs to kidneys.
The human heart generates complex efforts to pump blood through the body, and although it is known that the heart muscle changes for the worse in response to abnormal forces, for example, due to high blood pressure or valve insufficiency, it has been difficult to model and study these pathological processes.
The MiniPUMP functions as the ventricle of the heart. Its area is only 3 square centimeters. The acrylic components made using three-dimensional printing are placed on a thin plate containing miniature valves capable of opening and closing to control the flow of fluid, and small tubes carrying this fluid in the same way as arteries and veins do in the body. And the fluid is forced to move by contracting cardiomyocytes grown from induced pluripotent stem cells.
The video on the left shows the mini–ventricle itself, on the right - the movement of fluid in an acrylic vessel.
The basis of the miniPUMP is an acrylic frame that supports the heart tissue and moves with it as it contracts. This is a series of ultra-thin concentric spirals connected by horizontal rings.
A large-scale replica of the frame supporting the heart tissue.
To print each of the components, the group used two–photon direct laser writing - a more accurate version of three-dimensional printing. Light hitting the liquid resin causes it to solidify; since light can be directed with high accuracy, many miniPUMP components are measured in microns.
The decision to make a frame of such small dimensions, rather than life-size or larger, was deliberate and is crucial for the functioning of the model. The fact is that a thin thread made of the toughest material becomes flexible. Acrylic can be very rigid, but at the scale set in miniPUMP, the acrylic frame is able to compress beating cardiomyocytes.
The model reproduces the mechanical functions of the heart better and at the same time makes it possible to simulate the hearts of individual people. With this system, you can select a treatment for a specific patient if you take cells from him to create cardiomyocytes.
The next goal of the miniPUMP authors is to improve the technology and increase the reliability of the system.
Article C.Michas et al. Engineering a living cardiac pump on a chip using high-precision fabrication is published in the journal Science Advances.
Aminat Adzhieva, portal "Eternal Youth" http://vechnayamolodost.ru based on materials from Boston University: New Miniature Heart Could Help Speed Heart Disease Cures.