UTHealth Research Shows Modified Adult Stem Cells May Be Helpful In Spinal Cord Injury

Spinal damage paralyzes people and drastically changes their lives. Healing people with spinal cord injuries could restore motility to paralyzed people. However, this is a very complicated bit of treatment, and a deal of work needs to be done. A result that might bring us closer to that goal comes from the University of Texas. Researchers at the University of Texas Health Science Center at Houston have shown that in spinal cord-damaged rats, transplantation of genetically modified adult stem cells can help restore movement (published in the Feb. 24 issue of the Journal of Neuroscience).

Spinal cord injury causes “demyelination.” This 50-cent words simply means the destruction of the sheath that surrounds the long bits of that extend from neurons in the central nervous system. This sheath is composed of a protein called myelin, and this myelin sheath is produced by special cells called oligodendrocytes. Oligodendrocytes wrap around the axons of nerves and augment the conduction of nerve impulses through nerve cell axons. Without myelin sheaths, the nerves cannot send messages to make muscles move.

Qilin Cao, M.D.,and his colleagues discovered that transplanted adult stem cells called oligodendrocyte precursor cells (or OPCs) from the spinal cord could become mature oligodendrocytes. The new cells could form myelin sheaths and help restore electrical pathways through the spinal cord. This process, whereby oligodendrocytes make the myelin sheath is called “remyelination.”

Cao and his co-workers isolated oligodendrocyte precursor cells from adult spinal cord and before they transplanted them, they genetically modified them to express a special protein called ciliary neurotrophic factor (CNTF), a protein that encourages nerve growth. CNTF facilitates survival and differentiation of Oligodendrocyte Precursor Cells in cell culture.  Perhaps the most important result is that the demyelination coincided exactly with the anatomical location where they were needed.

This study confirms stem cell grafting in attempts to remyelinate an injured spinal cord is a viable therapeutic strategy.  Secondly, it also shows that recovery regenerative treatments will require more than simply grafting naïve precursor cells.

Embryonic Stem Cells Restore Sight in Blind Mice

Retinitis pigmentosa is a group of genetic diseases that affect sight. The disease is progressive, usually beginning with night blindness, then proceeding to night blindness and then complete blindness. The progression of the disease is somewhat slow, and many people retain some sight for the remainder of their lives, but others become completely blind.

Retinitis pigmentosa is caused by the death of retinal photoreceptor cells. The abnormalities originate in either the photoreceptors themselves, or the retinal epithelium behind the photoreceptors into which the photoreceptors are embedded.

Is there a way to replace dead photoreceptors? Yes there is, at least in mice. An international research team has used mouse embryonic stem cells to replace diseased retinal cells and restore sight in a mice with retinitis pigmentosa. The team, led by scientists at Columbia University Medical Center, made retinal cells and used them to replace the dead photoreceptors. They suggested that this regenerative strategy could potentially become a new treatment for retinitis pigmentosa, which is a leading cause of blindness that affects approximately one in 3,000 to 4,000 people, or 1.5 million people worldwide. This study will appear in the journal Transplantation in the March 27, 2010 print issue.

The retinal pigment epithelium cells are specialized retinal cells and they help maintain vision.  Retinitis pigmentosa results from the death of these retinal cells on the periphery of the retina, which leads to “tunnel vision.”  In people with tunnel vision, the field of vision is narrowed considerably and everything outside the “tunnel” appears blurred or wavy.

In this study, sight was restored in one-fourth of the mice that received the stem cells, but complications of benign tumors and retinal detachments were seen in some of the mice.  Therefore there is a need to optimize these techniques to decrease these complications.  One modification that might be to use cells other than embryonic stem cells that do not cause tumors.

For example, inside the eye and lining the back part of it is a layer of photoreceptors that detect light, color, and images.  These photoreceptors convey this information to the brain with the help of several cells and assist them.  Collectively, this layer is called the retina.  Adjacent to the retina is a structure called the ciliary epithelium, which also harbors a stem cell population that divides and grows in response to retinal injury.  Because of this, ciliary epithelium stem cells are also called retinal stem cells or RSCs.  When grown in the laboratory, RSCs can differentiate into many of the cell types found in the retina (T.A. Reh and A. J. Fischer, Methods in Enzymology 2006;419:52-73).  Discovery of this stem cell population offers the possibility of using them to repair retinal damage.

Because retinal damage and death are a major component of many diseases of the aged like macular degeneration and Stargardt disease, this procedure might provide some very exciting ways to treat blindness in older patients.