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Mouse brain tissue kept alive for several weeks in laboratory

Mouse brain tissue kept alive for several weeks in laboratory

Researchers from Japan have kept small portions of mouse brain tissue alive and viable for a period of 25 days, isolating in a culture. This has highly increased the timeline in which the isolated brain tissue can keep the functions intact extending days to weeks. This can affect the research in therapeutic drugs in a positive way. The findings have been published in the Analytical Sciences journal.

The key to success was a new technique that combines a special kind of membrane with an improved microfluidic device. Microfluidic devices use small channels for delivery of fluid into tissues and are better than the normal culture dishes specially for ex vivo tissue experiments. They can also be customized highly and mimic certain kinds of cell behaviors. They also require small volume samples thus making it easy to study the cell interactions. 

However, only a few days is not sufficient to understand how body systems react to various things. The main problem is to keep a balance. Tissues dry quickly so the system has to be kept moist along with nutrients in a wet culture medium. Too much moisture prevents cells to exchange gases which the tissue needs thus drowning it finally. This problem had to be tackled by the researchers. 

This device has a semi-permeable microfluidic channel that is surrounded by an artificial membrane and solid walls. These are made from polydimethylsiloxane, a polymer mainly used in microfluidic devices. The tissue does not sit in the bath consisting of the culture medium but instead, the fluid circulates through the channel, passing by the membrane to keep the tissues most while still maintaining the exchange of gases between cells. 

Nobutoshi Ota, a biochemist at RIKEN Center for Biosystems Dynamics Research said that the medium flow was difficult to be controlled as the microchannel between the porous membrane and PDMS walls were not normal. The team got success after repeated trials and modifications to the membrane while adjusting the flow rates of the inlet and outlet.

A small part of the brain named suprachiasmatic nucleus(SCN)  was used which is responsible for keeping the circadian and biological rhythms intact in mammals. Neuronal cells in SCN exchange information by keeping the motion of peptides and molecules between cells intact. This is ideal for studying cell interactions. 

The mice from where the SCNs were harvested had been edited genetically such that the circadian rhythm in the brain was connected to the production of a fluorescent protein indicating if everything was working properly. 

The fluorescence was active for 25 days compared to that of a normal culture dish where after 10 hours the activity control reduced by 6 percent. The experiment lasted for only 25 days since it was the cutoff time for this experiment. It could have lasted well beyond 100 days. 

Researchers believe that this can also be used for remaining organ tissues with the possibility for human organs that are grown in the laboratory. This will improve the research in organogenesis by culturing and observation which is needed for the growth of organs and tissue. 

Journal Reference: Analytical Sciences

Blood vessels 3D rendering

Scientists develop functional blood vessels from cadaver tissues

Blood vessels can be damaged in many conditions such as trauma, cardiac disorders. If they are not repaired in time, it can lead to serious complications. So they can be repaired in two ways, either make a new one or replace it with a vessel from a different body part.

Both the options have their own limitations. Hence researchers are working on a third option, use the blood vessels from a dead body. Humacyte, a medical research company based in North Carolina is working on a new method for replacing blood vessels from tissues of its deceased donors. Their recent trials involving patients with kidney failure have shown positive results. Instead of swapping a damaged vessel with the one from the cadaver, they have developed a model in which the donated cells work in making a protein framework for the patient’s cells to grow.

This method has some great advantages over the the existing methods. If the blood vessels of the body did not work doctors usually found a replacement for them from another body part. The replacement must match the right size and shape, and this involves lot of work. But even then, the replaced vessel might not work and proper grafting may not take place. In some cases, a synthetic vessel can also work if it is replaced for a larger blood vessel, but it gets very risky for smaller blood vessels.

Hence, a midway approach is to make a frame for the blood vessel and let it be populated by the tissues from the patient’s body. This can be either a synthetic one or a framework of proteins from a cadaver.

Superficial blood vessels of the head and neck

Superficial blood vessels of the head and neck( Credits – Wikimedia Commons)

The challenge in this method is to make sure the host cells move into their new ‘home’ and gets repopulated there. It is very crucial to identify which cells take part in the re-population of the implanted material and whether it is successful or not in the patient’s body.

The team at Humacyte seeded smooth muscle cells from cadavers onto a biodegradable mesh. The cells were fed nutrients and it produced a a 3D network of collagen proteins. After the disintegration of the mesh, a protein tube of 420 mm length and 6mm diameter formed. This was termed as human acellular vessel(HAV). All the foreign cells in the HAV were removed as they can be recognised as foreign substance and initiate immune response in the body.

This HAV was implanted in the upper arms of 60 persons with kidney failure. These blood vessels did not generate any significant immune response. Samples of HAV were obtained after a couple of years and it was found that the HAVs were populated with smooth muscle and endothelial cells and microvessels which supplied nutrients to the implant.

Thus the procedure was successful and researchers feel this can now be implemented in hundreds of patients and in future can be used in more complicated injuries such as cardiac injuries.