Sunday, October 30, 2011

Delivery system makes stem cell treatment easier

Therapies that focus on delivering cells to individual organs, for regenerative purposes, might just be much more effective with a new technique developed by scientists. To send cells to their respective organs effectively, researchers engineered certain receptors on the cellular surface, that function as a 'homing device'. By doing this, cells containing the receptors will only 'hook' on to tissue that is damaged. Being able to specifically target tissues that require cell treatment is a big step forward for cell-based therapies, for example with stem cells, that have been hallowed as a 'wonder drug' for several diseases.

With the new technique, cells can simply be injected into the circulation of a patient, whereafter they will find the right way by themselves. After they reach the designated organ, they can integrate with existing tissue, and aid in regeneration of the damaged tissue. That way, cells no longer have to be injected in the damaged area, which can be quite a risky procedure. For their experiments, scientists used mesenchymal stem cells, that are able to become various cell types, and modified their surface. They were able to do this without genetic modification, or altering the behaviour of the cells. With a new receptor on the cell surface, they show behaviour that is commonly attributed to white blood cells, that are part of the immune system: they travel through the blood, but move out once they come across inflamed tissue. Because damaged tissue is usually accompanied by inflammation, the cells that are used for repair will automatically home there.

Cell-based therapies have been long promised, after scientists discovered how they could use stem cells as a treatment. These primitive cells have a lot of potential, because they have the capability to differentiate into a lot of different cell types. When the body suffers from damage and is unable to repair it with functional cells to replace dead tissue, that's where stem cells come in. By using certain chemicals, scientists are able to differentiate stem cells into tissue of choice: that's how we are able to make neurons, cells of the brain and the nervous system, that the body is usually unable to re-make by itself.

An example where this technique could come in handy is regeneration of heart muscle, after a stroke. In these patients, dead muscle cells of the heart are being replaced by non-functional scar tissue. Inhibiting this process and delivering cultured stem cells that have been directed to differentiate to heart cells, can be used to turn the scar formation around, and making functional tissue instead. Not only stroke, but also neurodegenerative diseases, like MS, can be repaired in this way.

Finding an easy way to get the drug, cells in this case, to the place of action is always an important step in drug therapies. So far, we have been unable to target bulky cells automatically. However, we are able to develop drugs that specifically target cells: by engineering antibodies that are build to recognize a single epitope (point of recognition on a protein), the drug is only able to stick at places where this protein is found in the body. By engineering cells to contain specific receptors, that home them to a specific area in the body, they basically function the same way as these antibodies. 

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