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Stem cells can now be safely delivered to the site of injury or disease. T.V. Jayan reports:
Stem cells, one of the most promising medical therapies of the 21st century, may get a boost from a humble marine plant. A team led by an Indian researcher in the US turned a substance isolated from a commonly found brown algae into a device that can release stem cells inside the human body for permanent repair jobs.
A polymer naturally occurring in brown seaweed forms the scaffold for the delivery mechanism
Stem cells have the ability to morph into every kind of cell and tissue in the body and are thus considered to be a potential antidote for a host of medical problems, ranging from a degenerative ailment like Alzheimerâ€™s to an injury resulting in a broken leg. Though this has been known for a while, one of the key issues that prevented stem cell culture from moving into the realm of application was the lack of an effective delivery mechanism.
Ravi Kane, professor of chemical and biological engineering at the Rensselaer Polytechnic Institute in New York, and his team seem to have resolved this problem. The researchers (who include two Indian students, Akhilesh Banerjee and Supriya Punyani) extracted a polymer naturally occurring in brown seaweed and converted it into a device that can support the growth and release of stem cells at the site of an injury or the source of a disease.
â€œWe have developed a scaffold for stem cell culture that can degrade in the body at a controlled rate,â€ says Kane, who was voted among the top 100 scientific brains below the age of 35 by the Massachusetts Institute of Technology in 2004. Such scaffolds, he thinks, could be used some day to release stem cells directly into injured tissue.
The seaweed material, known as alginate, is actually a complex carbohydrate-like sugar. Highly fibrous, it can turn into a tiny, rigid three-dimensional mesh when mixed with calcium. The resulting stuff, called alginate hydrogel, can retain stem cells. These substances are safe, palatable and already in use in the food industry.
But when it comes to medical application, alginate poses a problem. It does not naturally dissolve in the human body and can stay on for months. It may thus not be ideal for stem cell implantation.
Stem cells can now be safely delivered to the site of injury or disease. T.V. Jayan reports
Kane and his colleagues, however, have found a safe and effective means to disintegrate the hydrogel once itâ€™s inside the body.
According to a report by the scientists in the forthcoming issue of the journal Biomaterials, one of the reasons alginate does not dissolve naturally in the human body is that mammals do not produce an enzyme that is responsible for disintegrating it. Such an enzyme, however, does exist in brown algae as well as many bacteria.
Hence if this enzyme were packed within the cage, it would ensure the controlled degradation of the scaffold so that a sustained release of stem cells is assured. For this, the Rensselaer scientists first created microscale beads (microspheres) containing varying amounts of the enzyme alginate lyase. Subsequently, they were encapsulated in the larger alginate scaffolds along with the stem cells. As the microspheres degraded, the enzyme was released into the larger alginate scaffolds and it slowly began to eat away at their surface, releasing the healthy stem cells in a controlled fashion.
â€œYou could either (surgically) implant the stem cell containing hydrogel at the site of the injury or form gels in situ,â€ Kane told KnowHow.
â€œThis seems to be an interesting piece of work from the point of view of medical application,â€ says Vidita Vaidya, a scientist working on neural stem cells at the Tata Institute of Fundamental Research, Mumbai. â€œThe immediate beneficiaries of such stem cell-filled scaffold implantation would be those suffering from paralysis due to spinal cord injury.â€
The scientists say that the microspheres can also be filled with drug molecules and proteins that could influence the fate of the encapsulated stem cells. â€œBy adding these materials to the larger scaffold, we can direct the stem cells to become the type of mature, differentiated cells that we desire,â€ Kane remarks.
Source: The Telegraph (Kolkata, India)