Adapting Stem Cells to Deliver a Therapy
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There are many possible forms of therapy that either might be built or are presently being built atop of a greater knowledge of stem cells and cell biotechnologies. Cultured populations of stem cells can be let loose into the body to do their work, or existing cells can be directed to take action where they would normally stand aside, or tissues can be constructed for transplant, and many more variants upon these themes. As explained in a recent open access paper, stem cells can also stand duty as a method of delivering a therapy rather than being a form of therapy themselves: they can move around the body largely unhindered, and different types of stem cells have quite strong opinions as to which part of the body they would like to migrate towards. Given the right signals, stem cells can even be directed to quite specific locations - consider the way in which cells respond to injury, for example. This is but one of countless signals that cause stem cells to travel or take specific actions: a great deal of future medicine will be based on better understanding and control over stem cells in the body.

So let us say that you want to move a dose of a fragile therapeutic molecule into the brain, past the blood-brain barrier - and, further, to quite specific locations within the brain. Why not enlist stem cells to carry it in? Unfortunately it's not completely straightforward - stem cells have their own ideas as to where they would like to go, and if that isn't suited to the need at hand, then further improvement in control is needed. The basic concept still looks promising, however, even though early attempts are not achieving great results:

Transplantation of neural stems cells (NSCs) could be a useful means to deliver biologic therapeutics for late-stage Alzheimer's disease (AD). In this study, we conducted a small preclinical investigation of whether NSCs could be modified to express metalloproteinase 9 (MMP9), a secreted protease reported to degrade aggregated Aβ peptides that are the major constituents of the senile plaques.

Our findings illuminated three issues with using NSCs as delivery vehicles for this particular application. First, transplanted NSCs generally failed to migrate to amyloid plaques, instead tending to colonize white matter tracts. Second, the final destination of these cells was highly influenced by how they were delivered.

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Overall, we observed long-term survival of NSCs in the brains of mice with high amyloid burden. Therefore, we conclude that such cells may have potential in therapeutic applications in AD but improved targeting of these cells to disease-specific lesions may be required to enhance efficacy.

The medicine of the 2040s may involve more cell therapies than any other area at the present pace: cells ordered around, changed in situ into augmented bioartifical machinery to conduct repairs or deliver compounds to needed locations, or even joined by artificial cells that carry out similar duties but more effectively. We are built of cells, so it makes some sense that our medical technology might eventually also be largely built of cells, act through cells, or otherwise be based on the direct control and repair of cells.

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