Comparison of femtosecond laser-assisted corneal intrastromal xenotransplantation and the allotransplantation in rhesus monkeys

Inhibitory effect of anti-Scg3 on corneal neovascularization: a preliminary study

BACKGROUND

Corneal neovascularization (CNV) is an important disease that causes blindness. Secretogranin III (Scg3) has emerged as a new influencing factor of neovascularization. This study analyzed the Scg3 antibody's inhibitory effect on CNV and and explored its preliminary mechanism.

METHODS

Human umbilical vein endothelial cells (HUVECs) were treated with Scg3 and anti-Scg3. Cell proliferation, wound healing migration and tube formation assays were performed. Healthy adult New Zealand rabbits were randomly selected to be alkali burned and establish the corneal neovascularization (CNV) model. The rabbits were randomly divided into 3 groups (the high concentration group, low concentration group and control group). Different doses of anti-Scg3 and PBS were administered to the rabbits. Clinical examinations, immunostaining, quantitative real-time polymerase chain reaction (qPCR) and western blotting analyses were performed postoperatively.

RESULTS

In the in vitro study, the Scg3 antibody mixture inhibited Scg3-induced endothelial cell proliferation and angiogenesis. In the in vivo study, significant CNV was observed in the control group. Confocal microscopy also revealed considerable active neovascularization in the control group. There was no obvious CNV growth in the high concentration group. Additionally, CD31, LYVE1 and CD45 expression was significantly inhibited after treatment with a high concentration of Scg3 antibody. The qPCR and western blotting analyses revealed that the levels of ERK in the low concentration group and high concentration group were higher than those in the control group at 7 days and 14 days. The levels of VEGF in the control group were significantly increased compared with those in the high concentration group. In all three groups, the levels of Akt were not significantly different at any time point.

CONCLUSION

The expression of Scg3 could affect the growth of HUVECs in vitro. Treatment with a high concentration (0.5 µg/mL) of Scg3 antibody reduced the inflammatory response and inhibited the growth of corneal neovascularization after corneal alkali burn injury in rabbits. The MEK/ERK pathway might play an important role in the inhibitory effect of anti-Scg3.

Comparison of fresh and preserved decellularized human corneal lenticules in femtosecond laser-assisted intrastromal lamellar keratoplasty

Substantial evidence has demonstrated the application of fresh and decellularized human corneal lenticules from increasing myopic surgeries. Further preservation of decellularized corneal lenticules would extend its clinical application. However, whether fresh and preserved decellularized lenticules have the same effects in vivo, including refractive correction, remains unclear. Here, we made comprehensive comparisons between fresh human lenticules (FHLs) and preserved decellularized human lenticules (DHLs). Another group of decellularized lenticules was combined with crosslinking for potential keratoconus therapy. Optical transparency, biomechanical properties, and fibrillar ultrastructure were analyzed to evaluate the DHLs and crosslinked DHLs (cDHLs) in vitro. The DHLs retained high transparency and regular ultrastructure, with genetic materials mostly being eliminated. The strength of lenticules in the cDHL group was markedly increased by crosslinking. Moreover, after storage in glycerol for 3 months, the lenticules were reimplanted into rabbit corneal lamellar pockets assisted by a femtosecond laser. The rabbits were followed for another 3 months. There were no obvious rejective complications in any of the three groups. From 1 week to 3 months postoperatively, the host corneas of the FHL group remained highly transparent, while slight hazes were observed in the DHL group. However, the corneas of the cDHL group displayed opacity throughout the 3-month postoperative period. Furthermore, all the lenticules could effectively induce corneal steepening and refractive changes. Taken together, our data indicated that FHLs are ideal inlay products, whereas preserved DHLs could be an alternative for intrastromal lamellar keratoplasty. Our study provides new insights into the clinical application of human lenticule recycling. STATEMENT OF SIGNIFICANCE: : Currently, substantial evidence has demonstrated the application of fresh and decellularized human corneal lenticules from increasing myopic surgeries. Further preservation of decellularized lenticules would extend its clinical application. However, whether fresh and preserved decellularized lenticules have the same effects in vivo, including refractive correction, remains unclear. Herein, we decellularized human lenticules with or without mechanically strengthened crosslinking. After storage in glycerol for 3 months, the lenticules were reimplanted into rabbit corneas. Comprehensive comparisons were performed among fresh human lenticules (FHLs), decellularized human lenticules (DHLs) and crosslinked DHLs. Our study indicated that FHLs are ideal inlay products, whereas preserved DHLs could be an alternative for intrastromal lamellar keratoplasty. Our study provides new insights into the clinical application of human lenticule recycling.

Long-Term Clinical Outcomes of Small-Incision Femtosecond Laser-Assisted Intracorneal Concave Lenticule Implantation in Patients with Keratoconus

Purpose

The purpose of this study was to evaluate the long-term prognosis of small-incision femtosecond laser-assisted intracorneal concave lenticule implantation (SFII) in correction of human keratoconus.

Methods

This was a prospective study for 11 patients who received SFII after being diagnosed as progressive keratoconus based on the Amsler–Krumeich classification system. Clinical assessment was performed for all the patients prior to and postsurgically at different time points for 5 years. These included uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), biomechanically corrected intraocular pressure (bIOP), corneal topography, anterior segment optical coherence tomography (AS-OCT), confocal microscopy, and biomechanical assessment with Corvis ST.

Results

Comparison of preoperative and 60-month postoperative UDVA and CDVA (P_60months=0.081 and 0.001, respectively), all eyes showed an improvement in CDVA. Corneal topography showed no significant changes in corneal anterior K1, K2, posterior K1, K2, posterior elevation, or corneal densitometry compared with preoperative levels (P > 0.05). Corvis ST showed that central corneal thickness (CCT) and stiffness at applanation 1 (SP-A1) were significantly greater 1 week postsurgically when compared to the baseline (P < 0.05) and remained stable thereafter. The lenticule under the AS-OCT remained transparent throughout the entire postsurgical period. Under confocal microscopy, corneal edema and an increase in cell activation and reflectivity were observed at the lenticule-stromal interface within 1 week postoperatively. These reactions gradually subsided with time within 6 months.

Conclusion

SFII is an effective procedure to prevent the progression of keratoconus due to its minimal invasiveness and capability of maintaining a steady biometry of the cornea.

Changes in intraocular pressure and ocular pulse amplitude of rhesus macaques after blue light scleral cross-linking

BACKGROUND

Scleral cross-linking can enhance the biomechanical strength of the sclera and is expected to be a new operative method for the prevention of myopia. However, studies investigating the changes in intraocular pressure (IOP) and ocular pulse amplitude (OPA) after blue light-riboflavin induced scleral collagen cross-linking (SXL) in rhesus monkeys are limited. This study aimed to investigate the changes in IOP and OPA in three-year-old rhesus macaques 1 week, 1 month, and 3 months after blue light-riboflavin SXL.

METHODS

Seven three-year-old rhesus macaques (14 eyes) were randomly divided into two groups, with 4 monkeys in group A (8 eyes) and 3 monkeys in group B (6 eyes). The right eye of each rhesus macaque was used as the experimental eye, whereas the left eye was used as the control. In group A, one quadrant of each right eye was irradiated. In group B, two quadrants of each right eye and one quadrant of each left eye were irradiated. The IOP and OPA of both eyes were measured in all seven rhesus macaques before SXL and 1 week, 1 month, and 3 months postoperatively, and differences in the IOP and OPA between the experimental and control eyes were evaluated via the paired t test.

RESULTS

In groups A and B, there were no significant differences between the experimental and control eyes in the IOP or OPA before SXL or 1 week, 1 month, or 3 months postoperatively (P > 0.05).

CONCLUSIONS

The IOP and OPA are not significantly affected in 1 vs 0 or in 1 vs 2 quadrants of blue light SXL.

Effect of SMILE-derived decellularized lenticules as an adhesion barrier in a rabbit model of glaucoma filtration surgery

Background

To investigate the effects of small incision lenticule extraction (SMILE)-derived decellularized lenticules on intraocular pressure (IOP) and conjunctival scarring in a rabbit model of glaucoma filtration surgery.

Methods

Trabeculectomy was performed on both eyes of New Zealand rabbits. A decellularized lenticule was placed in the subconjunctival space in one eye of the rabbits (the decellularized lenticule group), and no adjunctive treatment was performed in the fellow eye (the control group). The filtering bleb features and IOP were evaluated 0, 3, 7, 14, 21, and 28 days after surgery, and histopathologic examination was performed 28 days after surgery.

Results

Decellularized lenticules significantly increased bleb survival and decreased IOP postoperatively in the rabbit model with no adverse side effects. The histopathologic results showed a larger subconjunctival space and less subconjunctival fibrosis in the decellularized lenticule group.

Conclusions

Decellularized lenticules can prevent postoperative conjunctiva-sclera adhesion and fibrosis, and they may represent a novel antifibrotic agent for trabeculectomy.

[Hordeolum and chalazion : (Differential) diagnosis and treatment]

Hordeolum and chalazion are the most frequent inflammatory eyelid tumors. They can occur in association with underlying diseases causing Meibomian gland dysfunction and/or chronic blepharitis. Due to the typical morphological features and clinical course, the diagnosis can mostly be clinically established. The majority of these lesions resolve spontaneously over time. In some instances, surgical intervention is unavoidable. In persistent, recurrent or clinically atypical cases malignant tumors must be excluded as a differential diagnosis by excisional biopsy and histopathological assessment.

Intrastromal Allogeneic Inclusions for the Management of Keratoconus: A Review of Current Literature

ABSTRACT

A new therapeutic alternative has been developed in the past 6 years to treat severe keratoconus in young patients. Those patients had only corneal transplantation as an option, but now a variety of surgical alternatives in the form of allogeneic corneal inclusions have bloomed and are becoming more popular. Although Bowman layer transplantation is the most studied technique, recent studies have described different options with very promising preliminary results. Mostly all the techniques described improve corneal curvature, visual acuity, pachymetry, contact lens tolerance, and foremost, manage to avoid or postpone corneal transplantation. Very few complications have been described so far, which makes these techniques not only feasible but also safe. Herein, we focus on reviewing recently published studies describing these techniques and their first results.

Femtosecond laser-assisted implantation of corneal stroma lenticule for keratoconus

Purpose

To review recent progress, challenges, and future perspectives of stromal keratophakia for the treatment of advanced keratoconus.

Methods

We systematically reviewed the literature in the PubMed database, last update June 30, 2020. No language restriction was applied. The authors checked the reference lists of the retrieved articles to identify any additional study of interest.

Results

Several techniques have been proposed for the treatment of keratoconus in order to avoid or delay keratoplasty. This was primarily due to the lack of accessibility to donor corneas in many countries. The ease and predictability of the more advanced femtosecond lasers used to correct ametropias by stromal lenticule extraction lead to hypothesize that generated refractive lenticules could be implanted into corneal stromal layers to restore volume and alter the refractive properties of the cornea in patients with corneal ectasias. At the same time, new techniques for preservation, customization, and cellular therapy of the corneal stromal have been developed, directing to the valorization of otherwise discarded byproducts such as donor corneas unsuitable for either lamellar of penetrating keratoplasty.

Conclusions

Femtosecond laser-assisted stromal keratophakia could be a suitable therapeutic option for the treatment of corneal ectasias, especially in patients with advanced keratoconus, providing biomechanical support recovering the pachimetry to nearly normal value at the same time. The accuracy and predictability of the refractive outcome are yet a critical issue and the patient eligible for the procedure still has to be characterized.

Corneal Stromal Regeneration: A Review of Human Clinical Studies in Keratoconus Treatment

The use of advanced therapies with stem cells to reconstruct the complex tissue of corneal stroma has gained interest in recent years. Besides, collagen-based scaffolds bioengineering has been offered as another alternative over the last decade. The outcomes of the first clinical experience with stem cells therapy on corneal stroma regeneration in patients with advanced keratoconus were recently reported. Patients were distributed into three experimental groups: Group 1 (G-1) patients underwent implantation of autologous adipose-derived adult stem cells (ADASCs) alone, Group 2 (G-2) received a 120 μm decellularized donor corneal stromal laminas, and Group 3 (G-3) received a 120 μm recellularized donor laminas with ADASCs. A follow up of 36 months of clinical data, and 12 months of confocal microscopy study was performed, the authors found significant clinical improvement in almost all studied mean values of primary and secondary outcomes. Corneal confocal microscopy demonstrated an increase in cell density in the host stroma, as well as in the implanted tissue. Using different approaches, allogenic small incision lenticule extraction (SMILE) implantation was applied in cases with advanced keratoconus. Some authors reported the implantation of SMILE intrastromal lenticules combined with accelerated collagen cross-linking. Others performed intrastromal implantation of negative meniscus-shaped corneal stroma lenticules. Others have compared the outcomes of penetrating keratoplasty (PKP) vs. small-incision Intralase femtosecond (IFS) intracorneal concave lenticule implantation (SFII). Femtosecond laser-assisted small incision sutureless intrasotromal lamellar keratoplasty (SILK) has been also investigated. The published evidence shows that the implantation of autologous ADASCs, decellularized or recellularized human corneal stroma, allogenic SMILE lenticules corneal inlay, and recombinant cross-linked collagen have shown initially to be potentially effective for the treatment of advanced keratoconus. In light of the present evidence available, it can be said that the era of corneal stromal regeneration therapy has been already started.

Small-Incision Femtosecond Laser-Assisted Intracorneal Concave Lenticule Implantation in Patients With Keratoconus

Supplemental Digital Content is Available in the Text.

Purpose:

To evaluate the feasibility and efficacy of small-incision femtosecond laser–assisted intracorneal concave lenticule implantation (SFII) and penetrating keratoplasty (PKP) in patients with progressive keratoconus.

Methods:

All the patients were clinically diagnosed with progressive keratoconus. Twenty patients underwent PKP (PKP group), and 11 patients underwent SFII (SFII group). Visual acuity, intraocular pressure, corneal topography, corneal visualization Scheimpflug technology, anterior segment optical coherence tomography, and in vivo confocal microscopy were analyzed.

Results:

Vision improved at 3 months postoperatively in the SFII group. In the PKP group, corrected distance visual acuity improved 1 week after surgery. Corneal topography showed a statistically significant decrease in the anterior K1 and K2. Corneal visualization Scheimpflug technology showed that changes in the biomechanical parameters of the SFII group were also statistically different from those of the PKP group. All the grafts from both groups were clearly visible by anterior segment optical coherence tomography observation. The central corneal thickness of both groups was stable during the 24-month study period. In vivo confocal microscopy showed a few dendritic cells in the subepithelial region in the SFII group. At 3 months after surgery, many dendritic cells and inflammatory cells were observed in the basal epithelium and stroma in the PKP group.

Conclusions:

Both SFII and PKP surgical procedures resulted in a stable corneal volume and improved visual acuity in this long-term study. SFII was less invasive and more efficient compared with PKP.

Ethical and Scientific Pitfalls Concerning Laboratory Research with Non-Human Primates, and Possible Solutions

Basic and applied laboratory research, whenever intrusive or invasive, presents substantial ethical challenges for ethical committees, be it with human beings or with non-human animals. In this paper we discuss the use of non-human primates (NHPs), mostly as animal models, in laboratory based research. We examine the two ethical frameworks that support current legislation and guidelines: deontology and utilitarianism. While human based research is regulated under deontological principles, guidelines for laboratory animal research rely on utilitarianism. We argue that the utilitarian framework is inadequate for this purpose: on the one hand, it is almost impossible to accurately predict the benefits of a study for all potential stakeholders; and on the other hand, harm inflicted on NHPs (and other animals) used in laboratory research is extensive despite the increasing efforts of ethics committees and the research community to address this. Although deontology and utilitarianism are both valid ethical frameworks, we advocate that a deontological approach is more suitable, since we arguably have moral duties to NHPs. We provide suggestions on how to ensure that research currently conducted in laboratory settings shifts towards approaches that abide by deontological principles. We assert that this would not impede reasonable scientific research.