Eyeworld

JUL 2017

EyeWorld is the official news magazine of the American Society of Cataract & Refractive Surgery.

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EW INTERNATIONAL 70 July 2017 by Stefanie Petrou Binder, MD, EyeWorld Contributing Writer one drop of the thrombin compo- nent, and mixed it on the debrided area with a spatula to form a paste- like matrix that is perfectly suitable for mesenchymal cells to grow. The gel formed instantly with the cells trapped inside it. Once the epitheli- um grows over the gel mass, the cells become a part of the stroma and they do their work at restructuring it and reversing the corneal scarring. The patients received topical anes- thesia and no peribulbar block, and the eyes were simply bandaged after the short procedure was completed. "In our earlier work that pre- ceded this, in the wound model, if we put the stem cells in at the acute stage, they would prevent scar- ring, and by putting them in at the chronic stage, once a scar formed, they could reverse the scarring and render the cornea much clearer," Dr. Basu said. "This is what we are ex- pecting to find in the present study. In the pre-clinical study, when we looked at the transmission electro- microscopic images, those corneas that were treated with the stem cells looked like anatomically normal corneas with a regular orientation of collagen fibers, while those that were not treated remained scarred and lost the normal orientation of How it's done Dr. Basu performed limbal biopsies, which yielded mesenchymal cells, by removing a small snip from the limbus of about 3 mm in diameter, at the 1 o'clock hour. The limbus healed without complications. He grew the sample in the lab, which generated both epithelial cells, which were easily isolated and removed, and mesenchymal cells. The cells expressed stem cell factors, and he identified normal human stromal tissue of type 1 collagen. The keratocytes aligned and changed ori- entation as the construct got thicker, reaching a thickness of about 150 microns in 6–8 weeks. Once the cells were grown, the patients were prepared for the procedure by marking the area on the eye where the cells were to be placed and gently debriding it. The MSCs were mixed into a commer- cially available fibrin glue, which has two components: fibrinogen and thrombin. By mixing the MSC into the fibrinogen component of the glue, which is thicker and does not dissipate when placed on the cornea, Dr. Basu was able to retain control of the mixture once placed on the cornea. He placed one drop of the fibrinogen/MSC mixture and culture system, have them differenti- ate into keratocytes that would help in modulation of the stromal prob- lem, and restore the opaque cornea into transparent tissue," Dr. Basu said at the 2016 European Society of Cataract and Refractive Surgeons (ESCRS) Congress in Copenhagen, Denmark. "This is basically regen- eration instead of replacement. We use the same scaffold of the normal cornea but make the tissue trans- parent again by changing what is being produced in the tissue. The process involves embedding MSCs into debrided corneas, regenerating human corneal stroma, remodeling active corneal wounds, and prevent- ing/reversing corneal scarring. The procedure is exciting and when we started seemed very audacious." The pilot trial included patients with corneal scars, ulcers, and burns up to 250 microns in depth, exclud- ing the epithelium, who received limbal MSC therapy. A control group was given a fibrinogen/thrombin glue mixture without MSC. The study will evaluate the effect of MSCs on reduction in corneal haz- iness, improvement in uncorrected and best corrected vision, and an improvement in cosmesis as com- pared to controls. Clinical pilot study used autologous, limbal-derived mesenchymal stem cells to reduce corneal scars C onventional corneal allograph therapy is a widely used and successful therapy for corneal scars, but donor tissue is not universally available, and grafts can sometimes be rejected. The use of stem cells could reduce the need for corneal grafts and at the same time be a more readily available therapy to patients with corneal scars and burns worldwide. A new pilot study is using human limbal-derived mesenchymal stem cells (MSC) to resolve corneal scars. The process is uncomplicated and effective, according to Sayan Basu, MD, and Vivek Singh, PhD, Tej Kohli Cornea Institute, LV Prasad Eye Institute, Hyderabad, India, who helped pio- neer this treatment. "The hypothesis that we started this work with was that in patients who have corneal stromal diseases, we could take a limbal biopsy from the same eye, the fellow eye of the patient, or from a donor, and we could grow the cells in a xeno-free Fast and uncomplicated corneal regeneration Presentation spotlight Dr. Basu applies the limbal mesenchymal stem cells in a patient with severe corneal burns in the ongoing clinical trial. Source: Sayan Basu, MD The limbal mesenchymal stem cells are prepared for application on damaged corneas.

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