CORNEAL ENDOTHELIUM

NCRM’s work on Corneal Endothelium:
Bullous Keratopathy is a pathological condition which affects the cornea in which small vesicles, or bullae, are formed in the cornea due to endothelial dysfunction. Bullous keratopathy more often occurs in old age and has been addressed as the most common disease affecting the cornea in old age.


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Fig. 1. A schematic illustration of Bullous Keratopathy which makes the corneal endothelium opaque

  Corneal Transplantation is an effective approach to restore vision for such conditions.
 Though the cornea has three well defined components, until recently, even for a partial damage of the cornea i.e. damage of one of the three components, the whole cornea was transplanted.


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Fig. 2. Picture of a Bullous Keratopathy affected eye of a patient
(Picture courtesy: Dr John Sudhakar, Joseph Eye Hospital, Trichy)

As far as the endothelial damages (inner most layers) are concerned, stem cell treatment was considered difficult. A few reasons behind this are:
Though the outer layer- epithelium has stem cells which when expanded can be transplanted on the affected portion and could help retrieve the vision by epithelial layer healing, the endothelium was not considered to have stem cells or progenitor cells for such repair either by itself or by a transplant assisted healing.
Endothelium was considered to be a very sensitive single layer of cells.  Even growing mature endothelial cells in the laboratory was considered to be difficult.
 Endothelium being a sensitive layer of cells could be damaged even when a lens removal procedure is done or could get damaged with aging and no regeneration by natural repairing process was found to be occurring for its recovery.
With this background, when a cadaver eye (dead donors cornea)  is obtained for transplantation to a prospective recipient (needy patient) the cadaver cornea is checked whether all three layers are in good condition and then transplanted to the recipient even when the recipient has a cornea which is defective in any one of the three components.
Recently a procedure of separating the endothelial layer of the donors eye (even when the epithelium is defective) and using the same to replace the defective endothelial layer (in such cases, the patients epithelium and stroma should be normal) has come into practice. This is a technically demanding procedure done in a very few centers in the world. This also has a limitation that the eye on only one side with defective endothelium (with other components normal) could be corrected using one donor eye.


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Fig.3. Selective replacement of endothelial layer only, when other layers are normal.

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 Fig.4. Total replacement of cornea; otherwise called corneal transplantation

At this juncture, Dr. Shiro Amano and his team of Tokyo University Japan found that the human corneal endothelium also has progenitor cells and that such cells could be multiplied in the laboratory. They were able to find out ways to separate the healthy endothelium from donors eye (even when the other two components could be damaged) and divide them into several pieces and isolate the endothelial cells and multiply the isolated endothelial cells in their laboratory. In addition to it they also tried the curative potential of such multiplied endothelial cells in animal models, which worked out well This phenomenally outstanding work of Dr Amano et al  attracted the attention of the entire international faculty working on endothelial disorders.

Amano et al could separate the endothelial cells as a layer from the donor’s eye and then subject them to cell multiplication immediately. The separation of such endothelium is a technically demanding job that has to be accomplished by an ophthalmologist with expertise in corneal surgeries. 
Advantages with cell based therapy of corneal endothelium:

This developments achieved by Dr Amano when comes to a clinical practice, can help cure more than one patient using one donor eye, because one donors endothelial layer is multiplied into several times to be used in more than one needy patient.

Present limitations with cell based therapy for corneal endothelium:
Though this finding was an eye opener to the eye specialists all over the world, unfortunately this has not been taken to a successful clinical application, because the multiplication did not produce a single layer of membrane like endothelium whereas it produced only several spheres of cells which had to be applied to the animal models and then those animals were made to keep their eyes down for 24 Hrs so that the cell spheres could settle down due to gravity, which is practically, a difficult procedure to be done in any human patient.

With this background, NCRM got into this job of reproducing the same in their lab in Chennai and also further adding some value to it.

NCRM’s contribution to the corneal endothelial work:
Dr Amano`s lab could separate the endothelial cells as a layer from the donors eye and then subject them to cell multiplication immediately. The separation of such endothelium is a technically demanding job that has to be accomplished by an ophthalmologist with expertise in corneal surgeries. Since at NCRM we don’t have a corneal surgeon we tried several methods of transporting the corneal endothelial layer separated by an experienced ophthalmologist at Joseph Eye Hospital in Trichy, which is 300 KM from Chennai and transported them to Chennai, which is a unique accomplishment we have tried. Among the various (totally 17) methodologies we tried, one of them could in a reproducible manner yield viable endothelial cells which could further be multiplied in NCRM laboratory, thereby making it possible a methodology by which corneal endothelial layers separated from a faraway place could be transported to a central lab in the Indian climatic conditions without cold storage or any special preservation methods and be proven to have viable cells to be expanded with prospective clinical application . This has also paved a way for us to transport such multiplied cells back to the hospital without special preservation methods to the hospitals for a clinical application.

By making such special preservation methods unnecessary it becomes a viable economical option that any hospital in small rural areas of India can send the donor eye-endothelial layer to a central laboratory like NCRM taking 24-36 Hrs by normal logistics and that the laboratory can also send back the multiplied cells back to the hospitals in remote places without hassles.

What next:
Though NCRM could reproduce the same work done by Dr Amano with a value addition of transportation of separated corneal endothelium from donor eyes from a hospital to a central lab at varying temperature conditions, the clinical application needs some more technical inputs. At this juncture we were in need a scaffold or a membrane like structure   which can hold the multiplied cells close to the affected portion of the endothelium, prevent them from getting scattering around, (which could make them get settled in unwanted places causing trouble) and hold them for some time i.e a few days until healing of the diseased endothelium takes place and then could be removed .

  1. When a donor corneal endothelial specimen is received, it could be used for more than 5-10 needy patients’ eyes against the present technology by which it could be used for only one patient’s one eye.
  2. There is no need that every small clinic/hospital in small villages/periphery should have a stem cell processing laboratory with elaborate investments and infrastructure, but a central lab within reach by 24-36 hrs logistics facility that too in room temperature preservation of the cells can serve a large surrounding area making things affordable to common man.

Step after the initial studies:
We propose to establish WORLD’S FIRST CORNEAL ENDOTHELIAL STEMCELL BANK(CESBANK) and supply to the corneal surgeons of the entire world the Corneal Endothelial Stem cells so that they can treat their patients with our stem cells.

Transplantation safety of allogenic corneal endothelial stem cells:
Yes it is. Because corneal transplantation needs no blood group or any kind of tissue matching as it has been in clinical practice in for more than five decades.