"UNRAVELING KERATOCONUS: MITOCHONDRIAL ULTRASTRUCTURE CHANGES AND DNA VARIATIONS"

Keratoconus (KC) is thinning of corneal stroma & irregular astigmatism, resulting in diminution of vision. The etiology is unknown yet. There is evidence of imbalance in oxidative balance and mitochondrial function in KC corneas. Therefore, our study conducted the whole mitochondrial DNA (mtDNA) sequencing to study the mtDNA variations and analyse the mitochondrial morphology in KC patients.

It is a prospective, cross-sectional pilot study at Dr. R. P. Centre for Ophthalmic Sciences & department of anatomy AIIMS New Delhi.

Ten KC patients were recruited in this0 prospective study. Blood and cornea from same patients were collected for mtDNA genome sequencing. Tissue was collected to perform transmission electron microscopy (TEM). DNA was isolated from blood and corneal tissues followed by agarose gel electrophoresis and library preparation. Whole mtDNA sequencing was done on the libraries by illumina HISeqX sequencer. 1*1mm corneal tissue was processed for TEM.

In our study, mutations were found in both D-loop region and coding region. Most common mutations were T to C and C to T followed by A to G in D-loop region.  Total of 189 mutations at different position were found in coding region. There were 137 mutations reported as pathogenic in HmtVar database. Numerous degraded mitochondria with dissolved cristae were present in all the corneal tissues of KC patients.

This is first of its kind of study providing information of mtDNA mutations & structural changes in Indian population of keratoconus. This pilot study demonstrates how mtDNA damage contributes to KC. A larger cohort of patients needed to evaluate mtDNA mutations as a genetic risk factor indirectly contributing to development and/or progression of KC.