A time window for rescuing dying retinal ganglion cells

BACKGROUND

Retinal ganglion cell (RGC) degeneration and death cause vision loss in patients with glaucoma. Regulated cell death, once initiated, is generally considered to be an irreversible process. Recently, we showed that, by timely removing the cell death stimulus, stressed neuronal PC12 cells can recover from phosphatidylserine (PS) exposure, nuclear shrinkage, DNA damage, mitochondrial fragmentation, mitochondrial membrane potential loss, and retraction of neurites, all hallmarks of an activated cell death program. Whether the cell death process can be reversed in neurons of the central nervous system, like RGCs, is still unknown. Here, we studied reversibility of the activated cell death program in primary rat RGCs (prRGCs).

METHODS

prRGCs were exposed to ethanol (5%, vol/vol) to induce cell death. At different stages of the cell death process, ethanol was removed by washing and injured prRGCs were further cultured in fresh medium to see whether they recovered. The dynamics of single cells were monitored by high-resolution live-cell spinning disk microscopy. PS exposure, mitochondrial structure, membrane potential, and intracellular Ca2+ were revealed by annexin A5-FITC, Mito-tracker, TMRM, and Fluo 8-AM staining, respectively. The distribution of cytochrome c was investigated by immunofluorescence. The ultrastructure of mitochondria was studied by electron microscopy.

RESULTS

Analysis of temporal relationships between mitochondrial changes and PS exposure showed that fragmentation of the mitochondrial network and loss of mitochondrial membrane potential occurred before PS exposure. Mitochondrial changes proceeded caspase-independently, while PS exposure was caspase dependent. Interestingly, prRGCs recovered quickly from these mitochondrial changes but not from PS exposure at the plasma membrane. Correlative light and electron microscopy showed that stress-induced decrease in mitochondrial area, length and cristae number was reversible. Intracellular Ca2+ was elevated during this stage of reversible mitochondrial injury, but there was no sign of mitochondrial cytochrome c release.

CONCLUSIONS

Our study demonstrates that RGCs with impaired mitochondrial structure and function can fully recover if there is no mitochondrial cytochrome c release yet, and no PS is exposed at the plasma membrane. This finding indicates that there is a time window for rescuing dying or injured RGCs, by simply removing the cell death stimulus. Video Abstract.

Pathogenic CWF19L1 variants as a novel cause of autosomal recessive cerebellar ataxia and atrophy

Autosomal recessive cerebellar ataxia (ARCA) is a group of neurological disorders characterized by degeneration or abnormal development of the cerebellum and spinal cord. ARCA is clinically and genetically highly heterogeneous, with over 20 genes involved. Exome sequencing of a girl with ARCA from non-consanguineous Dutch parents revealed two pathogenic variants c.37G>C; p.D13H and c.946A>T; p.K316* in CWF19L1, a gene with an unknown function, recently reported to cause ARCA in a Turkish family. Sanger sequencing showed that the c.37G>C variant was inherited from the father and the c.946A>T variant from the mother. Pathogenicity was based on the damaging effect on protein function as the c.37G>C variant changed the highly conserved, negatively charged aspartic acid to the positively charged histidine and the c.946A>T variant introduced a premature stop codon. In addition, 27 patients with ARCA were tested for pathogenic variants in CWF19L1, however, no pathogenic variants were identified. Our data confirm CWF19L1 as a novel but rare gene causing ARCA.

Corneal astigmatism after clear corneal and corneoscleral incisions for cataract surgery

PURPOSE

To compare the astigmatism induced by clear corneal incisions (CCIs) and corneoscleral tunnel incisions (CSIs) for cataract surgery over 6 months.

SETTING

Rotterdam Eye Hospital, rotterdam, The Netherlands.

METHODS

Thirty-five patients having phacoemulsification were recruited prospectively; 15 had CCIs and 20, CSIs. Corneal topography was performed by computerized videokeratoscopy preoperatively and 6 months postoperatively. The change in keratometric astigmatism was calculated using the absolute magnitude and vector analysis methods.

RESULTS

There was no significant difference between the change in astigmatism produced by the two incisions (Student's t-test).

CONCLUSION

The CCI for cataract surgery did not produce significantly greater astigmatism than the CSI. Concern over CCIs having a greater risk of increasing corneal astigmatism is unfounded and does not justify withholding the technique from patients it could benefit.