Stem cell transplant may affect future hearing loss treatment
Japanese researchers evaluated the risks and effects of transplanting two types of stem cells into the cochlea of mice. They concluded that adult-derived induced pluripotent stem cells (iPS) and mouse embryonic stem cells (ES) showed similar survival and nerve Differentiation ability. However, transplanting iPS cells into the cochlea of mice has the risk of tumor growth. Considering the possibility of tumorigenesis, they concluded that the source of induced pluripotent stem cells is a key issue for induced pluripotent stem cell therapy.
Dr. Takayuki Nakagawa, Department of Otolaryngology, Graduate School of Medicine, Kyoto University, Japan, said: "Hearing loss affects millions of people worldwide."Recent research has shown that stem cell-based methods have the potential to regenerate hair cells and related auditory primary neurons . These structures are critical to hearing, and defects can cause severe hearing loss and deafness."
The authors note that embryonic stem cells have previously been identified as promising transplant candidates, but they are also related to immune rejection and ethical issues. Therefore, this study compared the survival rate and neural differentiation ability of ES and three mouse iPS cell clones.
Dr. Nakagawa explained: "Our study uses induced pluripotent stem cells from patient sources to determine whether they provide a promising alternative to embryonic stem cells." In addition, the potential tumor risk of iPS cells needs to be clarified. "
Four weeks after transplantation, the researchers found that most of the transplanted cochlea showed sedimentation of iPS or ES-derived neurons. However, there are differences in the number of cells based on cell lines. They pointed out that because the cochlea is small, the number of cells that can be transplanted into the cochlea is limited. Therefore, the number of fixed units is very low.
They also noticed that after a group of iPS cells were transplanted, teratomas (capsular tumors) formed in some cochlea.
Dr. Nakagawa said: "As far as we know, this is the first document of cochlear teratoma formation after cell transplantation."
The researchers concluded that the formation of teratomas in an iPS cell line indicates the necessity of selecting an appropriate iPS cell line to avoid tumorigenesis. They also pointed out that it is necessary to develop a method to eliminate undifferentiated cells after nerve induction in order to establish a safe therapy based on iPS for the inner ear.
"Although this study does not observe the ability of transplanted cells to repair hearing loss, it does provide insight into the survival and fate of transplanted cells. It emphasizes the importance of factors such as knowing the original source of cells and their degree of undifferentiation In order to rank the cells according to their likelihood of forming a tumor.