Biomarkers are objective indicators of various physiological and pathological conditions, obtained from biological samples. We conducted this study from the perspective of biomarkers for understanding disease pathology. We focused on three biomarkers for understanding disease pathology: 1) biomarkers of retinal neuronal cell death, age-related macular degeneration and autophagy (molecular biological markers), 2) trabecular meshwork and extracellular matrix in glaucomatous eyes (pathological markers), and 3) surgical findings markers, such as visualization of the intraocular membrane using Brilliant Blue G, and the development of novel vitrectomy surgery adjuvants.
I. Biomarkers of retinal neuronal cell death
Since there are few biomarkers for retinal neuronal cell death, we focued on rhegmatogenous retinal detachment, rather than a chronic disease, as the target disease. Rhegmatogenous retinal detachment is a disease whose onset is readily discernable, and for which, samples can be collected by vitrectomy surgery. Among a group of molecules called Damage Associated Molecular Pattern Molecules (DAMPs), we focused on Adenosine Triphosphate (ATP). Ocular extracellular ATP could serve as a biomarker of real-time rather than cumulative cell death. The degradative enzyme ectonucleoside triphosphate diphosphohydrolase-1 (ENTPD1) was found to be a potential marker of neuroprotective activity that degraded excessive ATP. ATP is an important biomarker for future studies on retinal neuronal cell death and neuroprotective therapies.
II. Age-related macular degeneration and autophagy
There is a close relationship between the onset of age-related macular degeneration and drusen formation, which is known as a precursor lesion. We analyzed the molecular mechanism of drusen formation, a biomarker of age-related macular degeneration. We found that age-related autophagy dysfunction was important in drusen formation. Lysosome-associated membrane protein-2 (LAMP2), a glycoprotein vital for lysosome biosynthesis and autophagosome maturation, plays an essential role in this process, which is closely related to the autophagy of retinal pigment epithelial cells. Our findings suggest that the molecular mechanisms of autophagy are important in developing therapeutic and preventive strategies for age-related macular degeneration.
III. The trabecular meshwork and the extracellular matrix of the glaucomatous eye
Pathological analysis is considered to be the best biomarker for understanding disease pathology because it allows the direct observation of the true state and causes of the disease. In this article, we focused on the trabecular meshwork and extracellular matrix in glaucomatous eyes. The resected trabecular meshwork was observed in three dimensions, which allowed us to observe the anterior chamber and Schlemm's canal from both sides. Thickening of the trabecular meshwork on the anterior chamber side and narrowing and occlusion of the network gaps were also evident under scanning electron microscopy. Pseudo-exfoliation materials were deposited on the trabecular meshwork on the corneal inner surface. The visualization of pathological biomarkers was effective in elucidating the pathogenesis of glaucoma.
IV. Visualization of the intraocular membrane using Brilliant Blue G250
Visual biomarkers that capture transparent membranes, such as the lens capsule and internal limiting membrane, are important for determining the success or failure of surgeries. In 2014, we completed an investigator-initiated clinical trial of Brilliant Blue G250, a surgical adjunct to visualize difficult-to-recognize internal limiting membrane. In the current study, we also conducted a multicenter phase III clinical trial of Brilliant Blue G250 for lens capsular staining to expand its application to anterior lens capsule. The visualized surgical findings biomarkers were found to be very effective and improved the safety and efficiency of treatment.
V. Development of novel vitrectomy surgery adjuvants
Many vitreoretinal diseases occur at the vitreoretinal interface, which is the border between the retina and the vitreous. Even after a posterior vitreous detachment, there is a residual vitreous cortex on the retinal surface. Even though internal limiting membrane peeling is effective, it results in pathological retinal changes and remains a technique that depends on the skill of the surgeons. Further surgical refinements are needed to ensure safety and reproducibility. To minimize the damage to the retina and efficiently remove the membranes on the retinal surface, we created a novel concept for a vitrectomy surgery adjuvant based on a new function to add to the surgical findings biomarkers. The novel vitrectomy surgical adjuvant has both high biocompatibility and intraoperative maneuverability. Further studies are needed for future clinal trials.
In this study, we introduced our results of challenges in understanding the pathology of the disease and developing treatment methods by clearly visualizing biomarkers that are difficult to recognize.
Nippon Ganka Gakkai Zasshi (J Jpn Ophthalmol Soc) 125: 266-284, 2021.