Japan uses human cells to reshape the cornea

Recently, researchers at Osaka University in Japan successfully used human cells to cultivate eye tissue such as cornea, crystal and retina for the first time in the world. The result was published in the famous scientific journal Nature. The study will help medical workers reconstruct the corneal epithelial tissue of the eye using inducible pluripotent stem cells (iPS) grown from the patient's own cells to allow the patient to see the light again. Compared with the traditional donor-derived cornea, this artificial cornea is not only abundant in source, but also is not prone to allogeneic rejection.

As early as 2007, Japanese scientist Yamanaka Miyazaki passed the transgenic induction, allowing highly differentiated human adult cells to “rejuvenate” and re-established into differentiated stem cells, thus winning the 2012 Nobel Prize. Such stem cells, which are "reversely grown" from adult cells, are called induced pluripotent stem cells. Induced pluripotent stem cells not only have the same differentiation potential as embryonic stem cells, but also have a wider range of sources and are more readily available than embryonic stem cells. From the beginning of its birth, induced pluripotent stem cells have become the focus of attention of scientists around the world.

After induction and culture, induced pluripotent stem cells can differentiate into various cells and tissues, and even develop into a new organ, providing an organ source for patients who need organ transplantation. Induced pluripotent stem cells cultured from the patient's own cells, due to homologous cells, transplanted new tissues and organs into the patient, do not cause allogeneic transplant rejection, and are an ideal source of organ transplantation. So far, scientists have used induced pluripotent stem cells to culture liver cells, cardiomyocytes, nerve cells, hematopoietic stem cells, etc., so that the application of induced pluripotent stem cells in clinical medicine is expected to become a reality. In 2009, the Chinese Academy of Sciences first used inducible pluripotent stem cells to culture live mice, demonstrating that induced pluripotent stem cells have the same ability to differentiate as fertilized eggs.

However, induced pluripotent stem cells are not 100% safe. When used in clinical applications, such cells do not cause rejection but have the risk of differentiating into tumor cells. So far, science and technology still cannot fully control the risk of induced pluripotent stem cells to differentiate into tumors. This also casts a shadow over the clinical application of induced pluripotent stem cells.

However, scientists and volunteers have not been ruined. After all, this new technology has the potential to save thousands of patients. In 2014, Japanese scientists first transplanted the retina of induced pluripotent stem cells into an eye disease patient, which is the first clinical application of induced pluripotent stem cells in the world.

Technically difficult

The structure of the eye is extremely complex and fine, and the cornea, retina, conjunctiva, lens, and any tissue lesions can cause blindness in the eye. The cornea from the donation of the remains is extremely limited. The use of stem cells to cultivate eye tissue has become a concern of experts. However, the induction of stem cells into complex ocular tissues is technically difficult and has always been a scientific problem.

Until 2007, Japan first extracted adult stem cells from adult corneal epithelium, and used this stem cells to culture corneal and conjunctival tissues. This historic achievement indicates that stem cell technology will play a major role in the clinical treatment of eye diseases. However, the number of such adult stem cells is sparse, the differentiation potential is not strong, and the clinical application range is narrow.

In 2014, researchers at Hopkins University in the United States first used induced pluripotent stem cells to develop stereoscopic retinal tissue with photosensitivity. This is the first time that induced pluripotent stem cells have been induced into human eye tissue. Dr. M. Valeria Canto-Sorell, associate professor of ophthalmology at the Johns Hopkins University School of Medicine, said that they can extract cells from patients with retinal diseases and It is transformed into stem cells and a plurality of retinas are cultured. Retinal tissue cultured in the laboratory will replace the patient's diseased or dead retinal tissue, allowing the patient to restore vision.

Remodeling the cornea

In a new study published by Osaka University in Japan, researchers have induced inducible pluripotent stem cells into tissues containing cornea, crystals, and retina, and isolated corneal tissue. They transplanted the cultured artificial corneal tissue to the rabbit that lost the cornea and achieved the desired experimental results.

In past studies, researchers have only been able to culture induced pluripotent stem cells into the posterior half of the eyeball (such as the retina, retinal pigment epithelial cells, etc.); in this study, the researchers were induced to induce inducible pluripotency. Stem cells are successfully differentiated into the first half of the eye (such as the stratum corneum and lens) and the second half (such as the retina and retinal pigment epithelial cells). This study is the first in the world.

Inducible pluripotent stem cells have a unique advantage in the application of artificial corneas. First, induced pluripotent stem cells are derived from the patient's own cells and are not susceptible to allogeneic rejection. Second, although induced pluripotent stem cells may produce tumor cells, there are no blood vessels in the cornea, and the internal environment is not suitable for tumor cells to survive. The cornea produced by induced pluripotent stem cells has a very low possibility of tumorigenesis and is very suitable for corneal transplantation.

After obtaining this encouraging result, the research team said that they will apply to the Osaka University Ethics Committee for clinical research at the end of 2016 to rejuvenate the cornea damaged by injury or disease.

The researchers believe that this research may bring new treatment methods, replace the donor cornea with artificial cornea, supplement the lack of donor corneal source, and let more patients see the light again. In two years, this artificial cornea is expected to be transplanted to patients.