Intranuclear mesoscale viscoelastic changes during osteoblastic differentiation of human mesenchymal stem cells.

Cell nuclei behave as viscoelastic materials. Dynamic regulation of the viscoelastic properties of nuclei in living cells is crucial for diverse biological and biophysical processes, specifically for intranuclear mesoscale viscoelasticity, through modulation of the efficiency of force propagation to the nucleoplasm and gene expression patterns. However, how the intranuclear mesoscale viscoelasticity of stem cells changes with differentiation is unclear and so is its biological significance. Here, we quantified the changes in intranuclear mesoscale viscoelasticity during osteoblastic differentiation of human mesenchymal stem cells. This analysis revealed that the intranuclear region is a viscoelastic solid, probably with a higher efficiency of force transmission that results in high sensitivity to mechanical signals in the early stages of osteoblastic differentiation. The intranuclear region was noted to alter to a viscoelastic liquid with a lower efficiency, which is responsible for the robustness of gene expression toward terminal differentiation. Additionally, evaluation of changes in the mesoscale viscoelasticity due to chromatin decondensation and correlation between the mesoscale viscoelasticity and local DNA density suggested that size of gap and flexibility of chromatin meshwork structures, which are modulated depending on chromatin condensation state, determine mesoscale viscoelasticity, with various rates of contribution in different differentiation stages. Given that chromatin within the nucleus condenses into heterochromatin as stem cells adopt a specific lineage by restricting transcription, viscoelasticity is perhaps a key factor in cooperative regulation of the nuclear mechanosensitivity and gene expression pattern for stem cell differentiation.

Corneal Endothelial Health after Phacoemulsification Cataract Surgery without Viscoelastic Substance.

PURPOSE: To evaluate corneal endothelial health after cataract surgery without viscoelastic substance (VS). METHODS: A prospective, non-randomized, case-series study was developed, and phacoemulsification cataract surgery without VS was performed on 1324 eyes between September 2015 and September 2018. As main outcomes, mean endothelial cell density (ECD) and mean central corneal thickness (CCT) were assessed before surgery and then 6 and 12 months after surgery. Data are summarized as mean, standard deviation (SD), and 95% confidence intervals (CI). RESULTS: A total of 1324 eyes were operated, and 31 were excluded by intraoperative complications. The mean ECD baseline was 2506 cells/mm2 (SD = 215, CI = 2494-2518); 6 months after surgery, it was 2328 cells/mm2 (SD = 213, CI = 2316-2340); and 1 year after surgery, it was 2265 cells/mm2 (SD = 214, CI = 2253-2277). In terms of percentage differences, the mean ECD decrease was 9.4% after 1 year. The mean preoperative CCT was 531.6 µm (SD = 34.8, CI = 529.7-533.5); 6 months after surgery, it was 537.7 µm (SD = 38.2, CI = 535.6-539.8); and 1 year after surgery, it was 537.9 µm (SD = 37.9, CI = 535.8-540.0). The mean CCT increased 1.2% 1 year after surgery. CONCLUSIONS: Phacoemulsification cataract surgery can be completely performed without VS, with very low intraoperative complications. The postoperative ECD and CCT changes occurred primarily during the first 6 months, and the changes decreased during the second semester.

Use of viscoelastic substance for preventing Descemet's membrane rupture in deep anterior lamellar keratoplasty / Uso de substância viscoelástica na prevenção da ruptura da membrana de Descemet na ceratoplastia lamelar anterior profunda

ABSTRACT Purpose: This study aimed to investigate the effect of using a viscoelastic substance in Descemet's membrane rupture in "double bubble" deep anterior lamellar keratoplasty. Methods: The medical records and videos of surgeries of 40 patients who underwent surgery between January 2014 and July 2015 were retrospectively evaluated. The patients were divided into two groups: 20 patients whose perforation of the posterior stromal wall was performed without administration of any viscoelastic substance (group 1) and 20 patients whose perforation of the posterior stromal wall was performed with administration of viscoelastic substance onto the posterior stroma (group 2). The Descemet's membrane perforation rate was compared between groups. Results: Perforation of the Descemet's membrane was observed in 12 (60.0%) patients in group 1 and only three (15.0%) patients in group 2. This difference was statistically significant (p=0.003). Only one (5%) patient in group 2 had macroperforation during the procedure, and the surgery was converted to penetrating keratoplasty. Eleven (55.0%) patients in group 1 had macroperforation of Descemet's membrane, and surgeries were converted to penetrating keratoplasty. This difference between the groups was statistically significant (p=0.001). Conclusions: Administering a viscoelastic substance onto the posterior stromal side just before puncture is an effective method to decrease the risk of Descemet's membrane perforation in deep anterior lamellar keratoplasty.(AU)

RESUMO Objetivo: Investigar o efeito do uso de uma substância viscoelástica na ruptura da membrana de Descemet em casos de ceratoplastia lamelar anterior profunda em "bolha dupla". Métodos: Foram avaliados retrospectivamente prontuários e vídeos de cirurgias de 40 pacientes operados entre janeiro de 2014 e julho de 2015. Os pacientes foram divididos em dois grupos: 20 pacientes nos quais a parede posterior do estroma foi puncionada sem a colocação de nenhuma substância viscoelástica (grupo 1) e 20 pacientes nos quais uma substância viscoelástica foi aplicada sobre o estroma posterior ao ser puncionada a parede posterior do estroma (grupo 2). A taxa de perfuração da membrana de Descemet foi comparada entre os grupos. Resultados: Observou-se perfuração da membrana de Descemet em 12 casos (60,0%) no grupo 1 e em apenas 3 casos (15,0%) no grupo 2. Essa diferença foi estatisticamente significativa (p=0,003). Apenas um caso (5%) no grupo 2 teve macroperfuração durante o procedimento, sendo a cirurgia então convertida em uma ceratoplastia penetrante. Onze casos (55,0%) no grupo 1 tiveram macroperfuração da membrana de Descemet e essas cirurgias foram convertidas em ceratoplastias penetrantes. Essa diferença entre os grupos foi estatisticamente significativa (p=0,001). Conclusões: A aplicação de substância viscoelástica sobre o lado posterior do estroma logo antes da punção é um método eficaz para diminuir o risco de perfuração da membrana de Descemet na ceratoplastia lamelar anterior profunda.(AU)

Toxic Anterior Segment Syndrome Outbreak after Cataract Surgery Triggered by Viscoelastic Substance.

PURPOSE: The purpose of this study is to present toxic anterior segment syndrome (TASS) outbreak at our clinic and discuss possible causes of TASS. MATERIALS AND METHODS: Thirty-four eyes of 34 patients developed TASS in a consecutive 2 weeks period were included in this study. Both anterior segment and fundus examinations were performed before and after uncomplicated cataract surgery. During the follow-up period, clinical features and all possible causes were evaluated including perioperative products and processing such as sterilization technique of surgical instruments, irrigating solutions, drugs, viscoelastic substance (VES), and intraocular lens. RESULTS: Patients had corneal edema, anterior chamber reactions, and decreased vision. No patient had purulent secretion, chemosis, lid involvement, and pain. At first 2 postoperative days, patients treated as infectious endophthalmitis by topical and oral antibiotics and then TASS was suspected, and patients treated completely with topical steroids. Suspected cause for TASS was VES substance, 2% sodium hyaluronate which had newly been used as VES product in phacoemulsification surgery. No new case has occurred after stopped usage of this VES product. CONCLUSION: As far as we know, this is the largest report of TASS outbreak in the shortest period from the same clinic caused by VES. Suboptimal products of surgical materials can be the cause of TASS. Close monitoring of each surgical step and elimination of causative agent can prevent the outbreaks of TASS.

The Relations of Cataract Progressed Postoperatively and Viscoelastic Substance or Mitomycin C used in Trabeculectomy

Viscoelastic substance or Mitomycin C(MMC)is not necessarily used in trabeculectomy. Hence, the authors investigated the rate of cataract development or progression after trabeculectomy related with using of the viscoelastic substance or MMC. The authors evaluated 119 eyes undergoing trabeculectomy and divided these eyes into 4 groups :group 1, 2, 3, and 4. In group 1, viscoelastic substance or MMC was not used(27 eyes). In group 2, only viscoelastic substance was used(35 eyes). In group 3, only MMC was used(15 eyes). In group 4, both viscoelastic substance and MMC were used(42 eyes). The cataract development or progression was examined with slit-lamp biomicroscope at postoperative 6 months and defined as the decrease of visual acuity more than 2 lines. The rate of cataract development or progression at postoperative 6 months was 18%in group 1, 14%in group 2, 40%in group 3, and 19%in group 4.The use of MMC without viscoelastic substance in trabeculectomy influenced cataract development or progression extremely. In conclusion, the results of this study suggest that the viscoelastic substance may reduce the rate of cataract development or progression after trabeculectomy in which MMC is used besides.

The Effect of Viscoelastic Substance for Trabeculectomy

The viscoelastic substance has been used popularly in trabeculectomy. Hence, the authors compared the safety and postoperative influence in viscoelastic substance use group with non-use group in trabeculectomy. The authors evaluated 20 eyes of 10 open-angle glaucomatous patients undergoing trabeculectomy who had had no systemic disease, no ocular trauma history, and over 21 mmHg intraocular pressure though over 2 eye drops and over one time p.o. medications a day. One eye of these patients used viscoelastic substance(Viscoat(r), Alcon, U.S.A.)and the other did not. The authors measured intraocular pressure and anterior chamber depth at postoperative 1 day, 3 days, and 7 days and measured corneal endothelial cell numbers at preoperative and postoperative 1 month and examined complications such as anterior chamber hemorrhage, anterior chamber inflammation and cataract progression. Viscoelastic substance did not influence intraocular pressure, anterior chamber formation and corneal endothelial cell damage postoperatively in trabeculectomy(p>0.5). But as complications, intraoperative iris prolapse in two eyes, postoperative anterior chamber hemorrhage in a eye, and postoperative cataract progression in a eye developed and anterior chamber inflammation was also worse in the non-viscoelastic substance use group. Conclusively, the viscoelastic substance would reduce intraocular tissue damage, make intraoperative bleeding control easy and prevent anterior chamber collapse immediately after operation in trabeculectomy. Because only open angle glaucoma was studied in the present research, further study was applied to acute angle closure glaucoma, neovascular glaucoma which is apt to bleed, and glaucoma with cataract or uveitis in which intraoperative intraocular damage is minimized.

Use of Viscoelastic Substance in Longstanding Recurrent Hyphema Patient

Rebleeding in traumatic hyphema may cause several complications in the affected eye, and specific treatment of recurrent hyphema is still not estabilished and only conservative medical treatments are used except for surgical evacuation of the clot in case of persistent high intraocular pressure. We treated longstanding recurrent hyphema patient unresponsive to conventional medical treatment, with viscoeleastic substance which was injucted into anterior chamber. A large dose(0.2CC) of viscoelastic substance sufficient to directly compress the anterior structures(Iris, ciliary body) was injected and subsequently it increased the intraocular pressur gradually. We assume that these tamponade effect by the viscoelastic substance and later intraocular pressure rise was responsible for the therapeutic effect. Thus, viscoelastic injection into anterior chamber in longstanding recu.rrent hyphema patient may be a useful treatment.