My new interest - IPs (for corneal regeneration?)

A better way to grow stem cells
New synthetic surfaces overcome challenges posed by existing methods for cultivating stem cells.

Anne Trafton, MIT News Office

Human pluripotent stem cells, which can become any other kind of body cell, hold great potential to treat a wide range of ailments, including Parkinson’s disease, multiple sclerosis and spinal cord injuries. However, scientists who work with such cells have had trouble growing large enough quantities to perform experiments — in particular, to be used in human studies.

Furthermore, most materials now used to grow human stem cells include cells or proteins that come from mice embryos, which help stimulate stem-cell growth but would likely cause an immune reaction if injected into a human patient.

To overcome those issues, MIT chemical engineers, materials scientists and biologists have devised a synthetic surface that includes no foreign animal material and allows stem cells to stay alive and continue reproducing themselves for at least three months. It’s also the first synthetic material that allows single cells to form colonies of identical cells, which is necessary to identify cells with desired traits and has been difficult to achieve with existing materials.

The research team, led by Professors Robert Langer, Rudolf Jaenisch and Daniel G. Anderson, describes the new material in the Aug. 22 issue of Nature Materials. First authors of the paper are postdoctoral associates Ying Mei and Krishanu Saha.

Refining surfaces

Human stem cells can come from two sources — embryonic cells or body cells that have been reprogrammed to an immature state. That state, known as pluripotency, allows the cells to develop into any kind of specialized body cells.

It also allows the possibility of treating nearly any kind of disease that involves injuries to cells. Scientists could grow new neurons for patients with spinal cord injuries, for example, or new insulin-producing cells for people with type 1 diabetes.

To engineer such treatments, scientists would need to be able to grow stem cells in the lab for an extended period of time, manipulate their genes, and grow colonies of identical cells after they have been genetically modified. Current growth surfaces, consisting of a plastic dish coated with a layer of gelatin and then a layer of mouse cells or proteins, are notoriously inefficient, says Saha, who works in Jaenisch’s lab at the Whitehead Institute for Biomedical Research.

“For therapeutics, you need millions and millions of cells,” says Saha. “If we can make it easier for the cells to divide and grow, that will really help to get the number of cells you need to do all of the disease studies that people are excited about.”

Previous studies had suggested that several chemical and physical properties of surfaces — including roughness, stiffness and affinity for water — might play a role in stem-cell growth. The researchers created about 500 polymers (long chains of repeating molecules) that varied in those traits, grew stem cells on them and analyzed each polymer’s performance. After correlating surface characteristics with performance, they found that there was an optimal range of surface hydrophobicity (water-repelling behavior), but varying roughness and stiffness did not have much effect on cell growth.

They also adjusted the composition of the materials, including proteins embedded in the polymer. They found that the best polymers contained a high percentage of acrylates, a common ingredient in plastics, and were coated with a protein called vitronectin, which encourages cells to attach to surfaces.

Using their best-performing material, the researchers got stem cells (both embryonic and induced pluripotent) to continue growing and dividing for up to three months. They were also able to generate large quantities of cells — in the millions.

Creating new synthetic materials for stem-cell growth is a longstanding problem that many researchers have tried to solve, says Sheng Ding, an associate professor of chemistry at the Scripps Research Institute. “In the past, it was more of a trial-and-error process,” he says. “The beauty of this work is that they can design these in a very systematic way. This is really a platform that can be applied not just to human embryonic stem cells, but also other cells.”

The MIT researchers hope to refine their knowledge to help them build materials suited to other types of cells, says Anderson, from the MIT Department of Chemical Engineering, the Harvard-MIT Division of Health Sciences and Technology, and the David H. Koch Institute for Integrative Cancer Research. “We want to better understand the interactions between the cell, the surface and the proteins, and define more clearly what it takes to get the cells to grow,” he says.

Other MIT authors of the paper are Said Bogatyrev, Z. Ilke Kalcioglu, Maisam Mitalipova, Neena Pyzocha, Fredrick Rojas and Krystyn Van Vliet. Jing Yang, Andrew Hook, Martyn Davies and Morgan Alexander of the University of Nottingham (United Kingdom) and Seung-Woo Cho of Yonsei University (Korea) are also authors of the paper.

A Biosynthetic Alternative to Human Donor Tissue for Inducing Corneal Regeneration: 24-Month Follow-Up of a Phase 1 Clinical Study

Sci Transl Med 25 August 2010:
Vol. 2, Issue 46, p. 46ra61
DOI: 10.1126/scitranslmed.3001022
Research Article
A Biosynthetic Alternative to Human Donor Tissue for Inducing Corneal Regeneration: 24-Month Follow-Up of a Phase 1 Clinical Study
Per Fagerholm1,*, Neil S. Lagali1,*, Kimberley Merrett2, W. Bruce Jackson2, Rejean Munger2, Yuwen Liu3, James W. Polarek4, Monica Söderqvist5 and May Griffith1,2,†

+ Author Affiliations

1Departments of Clinical and Experimental Medicine, and Ophthalmology, Faculty of Health Sciences, Linköping University, Cell Biology Building, Level 10, SE-581 83 Linköping, Sweden.
2University of Ottawa Eye Institute, Ottawa, Ontario, Canada K1H 8L6.
3CooperVision Inc., 5870 Stoneridge Drive, Suite 1, Pleasanton, CA 94588, USA.
4FibroGen Inc., 409 Illinois Street, San Francisco, CA 94158, USA.
5Synsam Opticians, Box 362, Trädgårdstorget 2, 581 03 Linköping, Sweden.

1Departments of Clinical and Experimental Medicine, and Ophthalmology, Faculty of Health Sciences, Linköping University, Cell Biology Building, Level 10, SE-581 83 Linköping, Sweden.
2University of Ottawa Eye Institute, Ottawa, Ontario, Canada K1H 8L6.
3CooperVision Inc., 5870 Stoneridge Drive, Suite 1, Pleasanton, CA 94588, USA.
4FibroGen Inc., 409 Illinois Street, San Francisco, CA 94158, USA.
5Synsam Opticians, Box 362, Trädgårdstorget 2, 581 03 Linköping, Sweden.
†To whom correspondence should be addressed. E-mail: may.griffith@liu.se
AbstractCorneas from human donors are used to replace damaged tissue and treat corneal blindness, but there is a severe worldwide shortage of donor corneas. We conducted a phase 1 clinical study in which biosynthetic mimics of corneal extracellular matrix were implanted to replace the pathologic anterior cornea of 10 patients who had significant vision loss, with the aim of facilitating endogenous tissue regeneration without the use of human donor tissue. The biosynthetic implants remained stably integrated and avascular for 24 months after surgery, without the need for long-term use of the steroid immunosuppression that is required for traditional allotransplantation. Corneal reepithelialization occurred in all patients, although a delay in epithelial closure as a result of the overlying retaining sutures led to early, localized implant thinning and fibrosis in some patients. The tear film was restored, and stromal cells were recruited into the implant in all patients. Nerve regeneration was also observed and touch sensitivity was restored, both to an equal or to a greater degree than is seen with human donor tissue. Vision at 24 months improved from preoperative values in six patients. With further optimization, biosynthetic corneal implants could offer a safe and effective alternative to the implantation of human tissue to help address the current donor cornea shortage.