LLNL researchers performed bio-3D printing of living aneurysms and observed their healing after surgery

China3D printingNet November 9th, in the United States, about one in 50 people has a cerebral aneurysm caused by weakening of the cerebral artery wall, and it is characterized by swelling of the blood vessel. The rupture of the blood vessel can lead to brain damage, stroke and even death. A team of researchers from Lawrence Livermore National Laboratory (LLNL), Duke University, and Texas A&M has been working to improve current surgical procedures and make them more patient-specific.These scientists usebiology3D printingTechnology created the first living aneurysm outside the human body, and then performed medical procedures to observe how it responded to treatment and heal like a real brain.

The team published a paper about their work in the journal Biomanufacturing.
“Here, we use gelatin-fibrin hydrogel to develop a three-dimensional (3D) printed vascularized tissue structure with aneurysms, in which human brain microvascular endothelial cells (hCMEC) are seeded on the inner vessel wall. hCMECs are easily distributed throughout the blood vessel. The wall (including the aneurysm wall) exhibits cell adhesion, diffusion and fusion. In addition, the in vitro platform can directly measure the flow through the particle image velocimetry, which can directly evaluate the vascular flow dynamics to be compatible with the 3D computational fluid dynamics model Compare.”



In vitro living brain aneurysm. (A)3D printingSchematic representation of an aneurysm bioreactor. (B) The extracorporeal aneurysm blood vessel structure perfused with red fluorescent beads shows that a patent blood vessel is formed after the sacrificial ink is withdrawn.

Obviously, cerebral aneurysms are not easy to repair. A very invasive treatment method is to fix a metal clip to the base to redirect blood away from the base, and requires the surgeon to open the skull and expose the brain. Another common but less invasive treatment is called intravascular metal coiling, which involves the surgeon inserting a thin metal catheter into the artery in the patient’s groin and feeding it all the way through the body and into the aneurysm. Then, they package it with a stent or coil, which can cause a thrombus, and the blood vessels that grow on the thrombus will grow above the clotted plug, basically forming a wall around the aneurysm, making it different from The remaining vasculature is separated. Unfortunately, the results of these two treatments often vary from patient to patient.

“Although there are many promising treatment options, some have a long way to go. Monica Moya, an engineer and lead researcher at LLNL, said that animal models are not necessarily the best way to try these options. , Because they cannot directly observe the treatment effect, and the geometry of the aneurysm cannot be controlled. “Having this powerful human body in vitro testing platform can help promote new treatment methods. If we can use these devices to replicate as many aneurysms as possible, we may help accelerate some of these products into the clinic and fundamentally provide patients with better treatment options. “

Used before3D printingTo help surgeons use models to train these complex procedures, and even monitor brain aneurysms in real time. But the research team led by LLNL was able to replicate brain aneurysms in vitro by using human brain cells to create bioprinted blood vessels. William “Rick” Hynes, another LLNL engineer’s original lead researcher, believes that bioprinting with human cells can help medical researchers create and validate more predictive, biologically relevant 3D models for patients.

LLNL team use3D printingThe aneurysm was replicated in vitro and performed endovascular repair procedures. The catheter was inserted into the blood vessel and the platinum coil was tightly packed in the aneurysm sac. They introduced plasma into the aneurysm and observed blood clots forming where the coil was. The green area indicates endothelial cells, and the red area indicates blood clots formed. Photo by LLNL Elisa Wasson

Hynes said: “We have studied this problem and believe that if we can combine computational models and experimental methods, maybe we can come up with a more deterministic method to treat aneurysms or choose the most suitable treatment for patients. Now we can start to build a framework for a personalized model that surgeons can use to determine the best way to treat aneurysms.” Hynes and Moya collaborated with former LLNL scientist Duncan Maitland, the latter of Texas A&M Biomedicine The head of the engineering team and also the head of Shape Memory Medical, the company is developing experimental shape memory coils for the treatment of aneurysms; another former LLNL scientist, currently assistant professor Amanda Landers at Duke University (Amanda Randles) developed the code for simulating blood flow for this work. The other authors of the paper are Lindy K. Jang (Texas A&M), Javier A. Alvarado (LLNL), Marianna Pepona (Duke), Elisa M. Wasson (LLNL), Landon D. Nash (Shape Memory Medical) and Jason M Ortega (LLNL)

Particle image velocimetry (PIV) analysis and 3D computational flow model simulation. (A) (Top) PIV measurement at the back of the aneurysm dome shows that there is no detectable flow at a flow rate of 300 µl min-1. (Middle) 3D flow simulation with the same geometry and flow velocity when z = -0.66 mm. (Figure below) PIV measurement values ​​in the mother and child blood vessels captured with a 2x objective lens at the same flow rate. (B) (Above) PIV measurements are gathered on the back of the aneurysm dome, showing a circular flow pattern, and captured with a 4x objective lens at a flow rate of 20 ml min-1. (Figure below) The simulation of the same geometry and flow velocity shows that fluid movement only occurs inside the dome at high flow velocity. (C) High-fidelity geometric reconstruction of printed live aneurysms constructed from image stacks collected by confocal microscope.

The team designed the sidewall of the bioreactor for the aneurysm platform in SOLIDWORKS and used the open source Slic3r software to convert the design into G code. Then, using a custom extrusion bioprinter, the wall was printed from SE-1700 silicone onto a glass slide, which was then cured and sterilized in an autoclave. Use sacrificial ink to print the geometry of the blood vessel and surround it with a protein-based hydrogel; cool it to dissolve the ink, leaving the shape of the vessel. Human brain endothelial cells cover the channels, forming aneurysms and blood vessels.Hynes repaired the bioprinted aneurysm by inserting microcatheters and tightly packed platinum coils into the capsule. Then, the researchers introduced plasma and observed the form of blood clot formation at the coil on the aneurysm, cutting it off from the fluid flow. LLNL believes that this is “the first surgical operation on artificial living tissue in history.” Eight days later, the research team witnessed the postoperative healing process of the vascular endothelium.

Aneurysm prints endothelialization of blood vessels. (A) Confocal image of actin-stained endothelial cells 7 days after perfusion culture. (B) A close-up photo of the actin-stained endothelium (green) in the dome of the aneurysm, showing the growth of a fully confluent monolayer.

The researchers also used the device to demonstrate the effectiveness of the Randles flow dynamics model, noting that blood rarely enters the aneurysm at low flow rates, and circulating blood flow faster when the flow rate increases, just like what happens when a human patient is excited Same. .LLNL said that when used in conjunction with computer modeling, the platform is an important step in creating patient-specific care for cerebral aneurysms based on factors such as blood pressure and blood vessel geometry, which can help speed up the processing time of complex surgical techniques. Go to the training clinic. Surgeons can use it as a tool to select the best aneurysm filling coil before surgery.

“Basically, a clinician can literally look at someone’s brain scan and run it through modeling software, which can show fluid dynamics before treatment. Hynes explained that it should also be able to simulate the processing method, And allows practitioners to shrink to a certain type of coil or packaging volume to ensure the best results.

Deploy an intravascular bare platinum coil (BPC) interventional treatment inside an external aneurysm. (A) Image of double coil deployment with dome of aneurysm. (B) A photomicrograph of bright field surveillance during BPC insertion from the intravascular microcatheter (first BPC: 3 mm×6 cm, second BPC: 2 mm×3 cm). (C) The largest projected confocal image stack of artificial aneurysm before and after BPC deployment and retraction (2 mm×3 cm), which is filled with 1 µm red fluorescent beads, indicating that the No damage to the capsule.

The platform can also be used to better understand basic biology and post-operative rehabilitation, as well as to conduct test runs in advance, without the need to induce animals to have aneurysms and then undergo surgery. It can directly measure the fluid dynamics inside aneurysms and blood vessels, which animals cannot do. “This is an ideal platform for computer simulation models, because we can perform these flow measurements, which would be very difficult to perform in animals. What’s exciting is that the platform mimics the vascular compliance and mechanical stiffness of brain tissue. It is also strong enough to handle the coiling procedure. Moya said: “You see the blood vessels expanding and moving, but it can withstand the operation as if you were in the body. This makes it very suitable for use as a training platform for surgeons or an in vitro testing system for embolization devices. “

Plasma clot formation responds to the deployment of BPC in the dome of living aneurysms in vitro. After BPC is deployed and injected with bovine plasma, the largest projected confocal image stack of an intact extracorporeal aneurysm. The formation of blood clots can be seen through the accumulation of trace amounts of fluorescently labeled red human fibrinogen contained in the plasma mixture. Endothelial cells are fluorescently stained with actin in green. The imaging showed the formation and occlusion of blood clots in the aneurysm sac, and no large blood clots formed elsewhere in the vascular structure.

The LLNL team stated that this platform showed promise in the early stages. Their next step is to combine the 2D blood coagulation model created by LLNL computing engineer Ortega with Randles’ 3D hydrodynamic model to simulate how the blood clot that causes an aneurysm forms in response to the 3D coil.

China3D printingNet original article!

(Editor in charge: admin)