Re-arming the body

Raşit Gürdilek

Elif Yılmaz

You’ll have to be aware of its weaknesses as well as its strengths and develop ingenious strategies and design new weapons to overcome the shortcomings. And, things get all the more complicated if the theater of war is the human body whose operations  we can’t say we have fully mastered despite all the advances in the fields of biology, medicine and genetics. Suppose a vital organ of your body has stopped functioning. And not only your body is unable to repair it,  the breakdown leads to further damage in the organism depending on the clockwork operation of all of its systems. So, what do we do? We shall have to seek support from other species (omitting to check their consent), or, rely on artificial materials, the products of joint efforts of microbiologists, genetic engineers and nanotechnology physicists. But, wait a minute! Warriors of our body’s defense forces, immune cells, have a standing order they have to unconditionally obey: “Destroy anything that is foreign.” Well, as the saying goes, if you have a gun, your finger itches for the trigger. Our army raids its own positions, suspecting them to be foreign agents. Or, it attacks the foreign forces, natural or man-made, invited as reinforcements. Hence, measures have to be incorporated into battle plans to protect the allied forces entering our body from the onslaught of our overzealous defense forces. And Dr. Seda Kizilel and her team of graduate and PhD students at Koç University’s Biomimetics and Tisuue Engineering Laboratory are doing precisely  that.

Long years of Hollywood conditioning have left us with mental images of labs as either football field-sized expanses of dazzling lights with cypher-operated blast doors, mega screens on walls and displays with arrays of blinking diodes, where crowds of scientists in white overalls, caps and galoshes trot to and fro; or, of dark chateau dungeons where the “mad professor”  with the uncanny glint in his eyes and the accustomed tehee,  attends to organ- filled large jars bristling with wires and cables.
As it is, however, the “operations room”  of the young commander who has participated in groundbreaking research at the University of Chicago, and her staff officers where they draw up and test combat plans is not much larger than a high-end living room, the only eye-catching piece of equipment being a laser with sets of mirrors which twist and turn the light and squeeze it into a a  thin green beam, complemented with the usual lab hardware of microscopes, heaters, spinners, lockers etc.

But here is where novel strategies and  remedies are developed for ailments like cancer and diabetes, which so far have defeated efforts towards effective cures. A form of diabetes called Type 1, makes sufferers dependent on external supplementation of insulin, a hormone which helps carbohydrate and fat metabolism in the body to allow glucose intake by skeletal muscles and fat tissuewhen the pancreas becomes unable to produce it.  And this means sufferers have to inject themselves with the required dose before each meal  ─ attracting questioning looks if it’s eaten at a restaurant.

Insulin is secreted at what are called “islets”,  conglomerations of different cells in the pancreas. The source of the hormone is a cell called Beta . Islet cells do not divide and proliferate. Hence the body’s immune cells eye these with suspicion and at times when the body’s constitution weakens, they attack and destroy them. Since the body cannot replenish them, people become diabetic with ensuing dependence on external infusion of insulin.
Is it possible to enable the body to produce insulin again? It is; if you can transplant new islets. In the West, these are generally isolated from cadavers in sterile conditions and injected to the patient’s liver via the portal vein. But since this carries with it the requirement for lifelong suppression of the patient’s immune system, it makes the recipient defenseless against attack from other disease vectors. An alternative is isolating islets from animals and transplanting them to humans. Porcine insulin is is closest to the human version. The downside is that the immune system needs to be suppressed again to protect the animal cells from annihilation.
The objective of the project Dr. Kizilel and her team work on, is to make islet transplantation possible without having to suppress the immune system. For that, two approaches are tried, with islands isolated by other Turkish universities from mice and rats.  One method is to encapsulate the islands in a protective shell to make them inaccesible to immune cells.  The second is to fool the immune system!

In both methods, the team inserts the islands into a biocompatible (not rejected by the body) synthetic hydrogel designed to mimic the functions of of a fluid called extracellular matrix, which surrounds the body’s cells.   Since this gel is porous, insulin, a small molecule, can ooze out from these small openings whereas immune cells made up of large molecules cannot penetrate in to destroy the alien cells. By inserting various materials such as stem cells and vascular growth factors , researchers try to enhance the functionality of pseudo-islets. And  naturally, after the transplant, planning is switched to the choice of defense systems against the immune system.
The team bases the second approach on a strategy turning the body’s immune system aginst itself. How? By recruiting moles! After encapsulating the islands within the gel, Dr. Kizilel and her team plan to also insert auxiliary immune cells whose functions are not killing  or metabolising pathogens, but gathering and communicating information. What’s expected from these relatively smaller cells – commonly called “police cells” although their “official” stylisation is “T-regulators”, – is  to tell patrolling killer cells “Here’s clean; no enemies hiding within!”  The reason they were chosen for the deception is that in previous work,  it was demonstrated that when these cells were extracted from the blood of recipients, allowed to proliferate and reinserted, hey enhanced body’s tolerance of the transplanted organs.
A further line of research Kizilel and her team pursue is biomemitec materials. By these she means materials sensitive to certain media, like those in nature, materials that dissolve in such media. Like, for instance, gels sensitive to Ph, or acidity. These are materials developed to transport drugs to intended parts of the body, or even into the cells themselves, without disintegrating and spilling their precious cargo on the way. Suppose you want to send, say, an anti-epileptic drug to the small intestine without having it prematurely dumped and degraded in the stomach. When you load it into the Ph-sensitive synthetic gel, the gel crosses the stomach with low acidity to reach the small intestine safe and sound where it disentegrates in higher acidic medium and unloads the drug. The team has also added a new dimension to the experiments conducted abroad with light-sensitive biomimetic materials. These are done generally with ultraviolet light, necessitating protective gear. Kizilel and her team, on the other hand, have produced  biocompatible synthetic gels sensitive to visible light.

Another item on the team’s work list,  likely to receive international acknowledgement,  is the manufacture of enzyme-sensitive biomimetic materials with magnetic nanoparticles for fight against cancer. One comes accross previously published experiments on the use of magnetically manipulated nanoparticles for cancer diagnosis. However, these are intravenously injected either in “naked” (uncoated)form or with polymers directly attached to the nanoparticle.

But, as they tend to cluster into aggregates and give themselves away, they trigger an immune response. In Kizilel’s laboratory, however, these nano particles have been encapsulated with a protective gel  for the first time in Turkey. These materials are also called “smart hydrogels.”

In the study, iron oxide nanoparticles previously used for cancer diagnosis and can be manipulated with magnetic fields because of their magnetic properties, are first encapsulated  in a gel whose chains are broken when there are enzymes in the environment. Next, pieces of protein sensitive to certain enzymes attached on the surface of the gel  spherule, enabling it to bind to the receptor on the surface of the tumor cell. Thus, making its way into the cell, the gel, containing magnetic nanoparticles, disintegrates on encountering collagenase enzyme and the released cancer drug tears apart the nucleus of the tumor cell and kills it. Still another possibility contemplated in connection with these microrobots, is making them sensitive to light, e.g. infrared light, instead of enzymes, so that the nanoparticles can be made to change their form or fold at the desired spot when doused with infrared light which can penetrate tissues.
Kizilel’s lab is also working on tissues. A project soon to be launched in cooperation with researchers from Japan’s Kyoto University aims at forming vascular tissues. Islets are once again at the center of the project.  Islets will be merged with nanogels (constructs at scales billionths of a meter) which dissolve in certain media (e.g. water) produced at Kyoto University and those produced at Kizilel’s lab to form a hybrid construction. Then molecules which initiate vascular growth will be inserted. These hybrid constructions then will be injected to animals at Kizilel’s lab – permission has just been obtained – and will be checked for development of vessels inside.
Why is vascularisation so important? The reason is that these islets can be transplanted not to the pancreas, but to the liver. Restoring pancreatic functions requires some 300.000 islets. And these can be transplanted, at least for now, uncoated. Even in this form, so many of them can clog the capillaries branched to everywhere in the liver, which literally is a blood-soaked tissue. Furthermore, the liquid carrying the injected islets can cause disruptions in liver functions by increasing the ambient pressure. When coated with hydrogel, islets with enlarged dimensions will further confound the problem.
What’s more, even supposing they survive the immune response thanks to their nanogel coatings, these cells can lose their vitality and functionality at the low-oxygen environment of the abdominal cavity.  Hence, the ultimate target of the project is equipping these islets with their own vascular tissues so as to enable them to dip into  the blood supply of the body. To check whether vascularisation takes place inside the hybrid gelous construct, they will be monitored first “in vitro” (lab environment) and then “in vivo” (in live body). In case vascularisation is observed, the next step would be trying to form the vessels around the islets by  dissolving the gel around the islet to bring it in contact with the formed vessels.  Then, these would be observed for possible changes in the insulin secreting functions of the islets.
 Among other biomimetic projects, Dr. Kizilel lists those designed for treatment of, say,  Alzheimer  through controlled drug transport with the encapsulation of hydrophobic  materials inside gels produced in her laboratory, and those done with the insulin-dissolving enzymes, for diabetes type- 2 cure.
The centerpiece of the lab’s equipment is a laser apparatus which, through a process called photopolymerisation, turns the photostarter molecules in the sample liquid into radicals by pumping them to higher energy levels with light at certain wave lengths.With the formation thus of polymer chains with cross bonds, the liquid and its contents turn into gels with the consistency of contact lenses. Besides the laser, the lab is endowed with other standard and specialised equipment needed for the research and experiments.
And the manpower, or rather the brainpower behind all these impressive achievements?

A few well-motivated graduate and PhD  students whose skills more than make up for the numerical shortages.

Özlem Çevik, is already well-acquainted with success. Having graduated from Yildiz Technical University’s Bioengineering Department at the top of her class, she qualified for a scholarship from TUBITAK, the scientific and technological research council of Turkey, which brought her for graduate studies at Koç University’s Chemistry and Engineering Department, under the guidance of Seda Kizilel. She is currently working on hydrogels which change  form in step with changes in Ph levels.

Tuğba Bal is another graduate of the ITU Molecular Biology and Genetics Department. Having completed her graduate studies at Dr. Kizilel’s lab, she is working for her PhD on Type 1 diabetes. Her current work in the lab involves the construction of water-based hydrogels called polyethyline glycol and coating islets with these to protect them from immune response. When stem cells, extracted from fat tissue at other universities, were placed beside the islets, marked improvements were observed in the functioning of the latter. In the next stage, growth factors will be inserted into the gel besides the islets and stem cells in hopes of triggering vascularisation.

Thus we conclude our tour of the lab, thanking Dr. Kizilel and her team, small but as “multipotent” as the cells they handle, and leave with full confidence that we shall come back soon to report on the fruits of their efforts.