Cellular roadmaps of viroid infection

Viroids are single-stranded circular noncoding RNAs that infect plants. According to the International Committee on Taxonomy of Viruses, there are 44 viroids known to date. Notably, more than 20 000 distinct viroid-like RNA sequences have recently been identified in existing sequencing datasets, suggesting an unprecedented complexity in biological roles of viroids and viroid-like RNAs. Interestingly, a human pathogen, hepatitis delta virus (HDV), also replicates via a rolling circle mechanism like viroids. Therefore, knowledge of viroid infection is informative for research on HDV and other viroid-like RNAs reported from various organisms. Here, we summarize recent advancements in understanding viroid shuttling among subcellular compartments for completing replication cycles, emphasizing regulatory roles of RNA motifs and structural dynamics in diverse biological processes. We also compare the knowledge of viroid intracellular trafficking with known pathways governing cellular RNA movement in cells. Future investigations on regulatory RNA structures and cognate factors in regulating viroid subcellular trafficking and replication will likely provide new insights into RNA structure-function relationships and facilitate the development of strategies controlling RNA localization and function in cells.

Flapless one-knot suture: a novel surgical technique for transscleral fixation of C-loop intraocular lenses

AIM

To describe a novel suture approach for transscleral fixation of C-loop intraocular lenses (IOL) and to compare the surgical outcomes with the four-haptics posterior chamber (PC)-IOL technique.

METHODS

We retrospectively analyzed 16 eyes of 16 patients who underwent transscleral fixation of C-loop PC-IOLs using a flapless one-knot suture technique, which were followed up for longer than 17mo. In this technique, the capsulorless IOL was suspended using a single suture for transscleral fixation of four feet. Then we compared its surgical outcomes and complications with the four-haptics PC-IOLs using the Student's t test and Chi-square test.

RESULTS

Sixteen patients of 16 eyes with a mean age of 58.3±10.1y (42-76y) who received transscleral C-loop IOL implantation due to trauma, vitrectomy, or cataract surgery with inadequate capsule support showed improved visual acuity. The difference was not significant between two IOLs except the surgery time (P>0.05). The mean operation times of C-loop IOL surgery was 24.1±1.83min and 31.3±4.47min of the four-haptics PC-IOL method (P<0.0001). In the C-loop IOLs group, there was statistical difference between the preoperative and the postoperative UCVA (logMAR, 1.20±0.50 vs 0.57±0.32, P=0.0003). There was no statistical difference between the preoperative and the postoperative BCVA (logMAR, 0.66±0.46 vs 0.40±0.23, P=0.056). However, there was no statistically significant difference in postoperative UCVA and BCVA between the two IOLs (P>0.05). We did not detect any optic capture, IOL decentration or dislocation, suture exposed, or cystoid macular edema in patients underwent C-loop IOLs surgery.

CONCLUSION

The novel flapless one-knot suture technique for transscleral fixation of C-loop IOL is a simple, reliable, and stable technique.

Systematic Study on the Biomechanical Stability of C-Loop Intraocular Lenses: Approach to an Optimal Design of the Haptics

To study the main design parameters that affect the mechanical stability of C-loop intraocular lenses, leading to an optimal design that minimizes the axial displacement, tilt and rotation. A total of 144 geometrical variations were studied on a 1-piece, non-angulated, C-loop hydrophobic acrylate intraocular lens. The study was performed in a finite element modeling simulation. The suitable set of variations was determined using a mixed-factorial analysis, allowing to analyse the impact of the different designs on the mechanical stability of the lens (compression force, axial displacement, tilt and rotation). The design parameters under study were: the length, width, thickness and opening angle of the haptic, the haptic-optic junction and the start of the haptic curvature. The compression (or reaction) force is affected by the haptic width, the haptic-optic junction, and the interaction between both. The axial displacement is mainly affected by the width and thickness of the haptic, and the size of the haptic-optic junction as well. The tilt is affected by the haptic thickness and the interaction between the haptic curvature and the haptic-optic junction. The rotation is affected by the start of the haptic curvature, the haptic-optic junction and the haptic width. The haptic-optic juntion is one of the most influential parameters affecting the four responses studied of the C-Loop IOL. The smaller the haptic-optic juntion, the better biomechanical stability.