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Liu Y, He Y, Deng Y, Wang L. Lenticule addition keratoplasty for the treatment of keratoconus: A systematic review and critical considerations. Indian J Ophthalmol 2024; 72:S167-S175. [PMID: 38271413 DOI: 10.4103/ijo.ijo_695_23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2023] [Accepted: 09/09/2023] [Indexed: 01/27/2024] Open
Abstract
Keratoconus is a corneal disorder characterized by the progressive thinning and bulging of the cornea. Currently, the major goal of management is to halt its progression, restore normal corneal strength, prevent acute complications, and save vision. Penetrating keratoplasty and deep anterior lamellar keratoplasty as conventional surgical methods for advanced keratoconus are limited by relatively high rates of immune intolerance, slow post-operational recovery, high costs, and shortage of donor corneas. Recently, the development of lenticule addition keratoplasty enables the restoration of corneal thickness simply by implanting a lenticule into the stromal pocket created with the femtosecond laser, which can originate from cadaver corneas or more appealing, be extracted from patients via a small-incision lenticule extraction (SMILE) surgery. As the first systematic review in this field, we critically review publications on lenticule addition keratoplasty and provide our perspectives on its clinical application and the focus of future research.
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Affiliation(s)
- Yanling Liu
- Operating Room, West China Hospital, Sichuan University/West China School of Nursing, Sichuan University, Chengdu, 610041, People's Republic of China
| | - Yan He
- Operating Room, West China Hospital, Sichuan University/West China School of Nursing, Sichuan University, Chengdu, 610041, People's Republic of China
| | - Yingping Deng
- Department of Ophthalmology, West China Hospital, Sichuan University, Chengdu, 610041, People's Republic of China
| | - Lixiang Wang
- Department of Ophthalmology, West China Hospital, Sichuan University, Chengdu, 610041, People's Republic of China
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Chan JS, Han E, Lim CHL, Kurz AC, Shuman J, Liu YC, Riau AK, Mehta JS. Incisional surface quality of electron-beam irradiated cornea-extracted lenticule for stromal keratophakia: high nJ-energy vs. low nJ-energy femtosecond laser. Front Med (Lausanne) 2023; 10:1289528. [PMID: 38162883 PMCID: PMC10754972 DOI: 10.3389/fmed.2023.1289528] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2023] [Accepted: 11/20/2023] [Indexed: 01/03/2024] Open
Abstract
Introduction Corneal lenticules can be utilized as an additive material for stromal keratophakia. However, following extraction, they must be reimplanted almost immediately or cryopreserved in lenticule banks. Electron-beam (E-beam) irradiated corneas permit room-temperature storage for up to 2 years, enabling keratophakia to be performed on demand. This study aims to compare the performance of high nano Joule (nJ)-energy (VisuMax) and low nJ-energy (FEMTO LDV) femtosecond laser systems on the thickness consistency and surface quality and collagen morphology of lenticules produced from fresh and E-beamed corneas. Methods A total of 24 lenticules with -6.00 dioptre power were cut in fresh human donor corneas and E-beamed corneas with VisuMax and FEMTO LDV. Before extraction, the thickness of the lenticules was measured with anterior segment-optical coherence tomography (AS-OCT). The incisional surface roughness of extracted lenticules was analyzed using atomic force microscopy (AFM) and scanning electron microscopy (SEM). Multiphoton microscopy was then used to assess the surface collagen morphometry. Results The E-beamed lenticules that were cut using FEMTO LDV were significantly thicker than the fresh specimens as opposed to those created with VisuMax, which had a similar thickness as the fresh lenticules. On the vertex, they were ∼11% thicker than the fresh lenticules. The surface roughness (Rq) of E-beamed lenticules incised with FEMTO LDV did not differ significantly from the fresh lenticules. This contrasted with the VisuMax-fashioned lenticules, which showed notably smoother surfaces (∼36 and ∼20% lower Rq on anterior and posterior surfaces, respectively) on the E-beamed than the fresh lenticules. The FEMTO LDV induced less cumulative changes to the collagen morphology on the surfaces of both fresh and E-beamed lenticules than the VisuMax. Conclusion It has been previously demonstrated that the low nJ-energy FEMTO LDV produced a smoother cutting surface compared to high nJ-energy VisuMax in fresh lenticules. Here, we showed that this effect was also seen in the E-beamed lenticules. In addition, lower laser energy conferred fewer changes to the lenticular surface collagen morphology. The smaller disparity in surface cutting quality and collagen disturbances on the E-beamed lenticules could be beneficial for the early visual recovery of patients who undergo stromal keratophakia.
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Affiliation(s)
- Jian S. Chan
- School of Clinical Medicine, University of New South Wales, Sydney, NSW, Australia
- Department of Ophthalmology, National University Health System, Singapore, Singapore
| | - Evelina Han
- Tissue Engineering and Cell Therapy Group, Singapore Eye Research Institute, Singapore, Singapore
| | - Chris H. L. Lim
- School of Clinical Medicine, University of New South Wales, Sydney, NSW, Australia
- Department of Ophthalmology, National University Health System, Singapore, Singapore
- Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore
| | | | - Jeremy Shuman
- Lions World Vision Institute, Tampa, FL, United States
| | - Yu-Chi Liu
- Tissue Engineering and Cell Therapy Group, Singapore Eye Research Institute, Singapore, Singapore
- Ophthalmology and Visual Sciences Academic Clinical Programme, Duke-NUS Medical School, Singapore, Singapore
- Singapore National Eye Centre, Singapore, Singapore
| | - Andri K. Riau
- Tissue Engineering and Cell Therapy Group, Singapore Eye Research Institute, Singapore, Singapore
- Ophthalmology and Visual Sciences Academic Clinical Programme, Duke-NUS Medical School, Singapore, Singapore
| | - Jodhbir S. Mehta
- Tissue Engineering and Cell Therapy Group, Singapore Eye Research Institute, Singapore, Singapore
- Ophthalmology and Visual Sciences Academic Clinical Programme, Duke-NUS Medical School, Singapore, Singapore
- Singapore National Eye Centre, Singapore, Singapore
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Thirunavukarasu AJ, Han E, Nedumaran AM, Kurz AC, Shuman J, Yusoff NZBM, Liu YC, Foo V, Czarny B, Riau AK, Mehta JS. Electron beam-irradiated donor cornea for on-demand lenticule implantation to treat corneal diseases and refractive error. Acta Biomater 2023; 169:334-347. [PMID: 37532130 DOI: 10.1016/j.actbio.2023.07.053] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2023] [Revised: 07/07/2023] [Accepted: 07/26/2023] [Indexed: 08/04/2023]
Abstract
The cornea is the major contributor to the refractive power of the eye, and corneal diseases are a leading cause of reversible blindness. The main treatment for advanced corneal disease is keratoplasty: allograft transplantation of the cornea. Examples include lenticule implantation to treat corneal disorders (e.g. keratoconus) or correct refractive errors. These procedures are limited by the shelf-life of the corneal tissue, which must be discarded within 2-4 weeks. Electron-beam irradiation is an emerging sterilisation technique, which extends this shelf life to 2 years. Here, we produced lenticules from fresh and electron-beam (E-beam) irradiated corneas to establish a new source of tissue for lenticule implantation. In vitro, in vivo, and ex vivo experiments were conducted to compare fresh and E-beam-irradiated lenticules. Results were similar in terms of cutting accuracy, ultrastructure, optical transparency, ease of extraction and transplantation, resilience to mechanical handling, biocompatibility, and post-transplant wound healing process. Two main differences were noted. First, ∼59% reduction of glycosaminoglycans resulted in greater compression of E-beam-irradiated lenticules post-transplant, likely due to reduced corneal hydration-this appeared to affect keratometry after implantation. Cutting a thicker lenticule would be required to ameliorate the difference in refraction. Second, E-beam-sterilised lenticules exhibited lower Young's modulus which may indicate greater care with handling, although no damage or perforation was caused in our procedures. In summary, E-beam-irradiated corneas are a viable source of tissue for stromal lenticules, and may facilitate on-demand lenticule implantation to treat a wide range of corneal diseases. Our study suggested that its applications in human patients are warranted. STATEMENT OF SIGNIFICANCE: Corneal blindness affects over six million patients worldwide. For patients requiring corneal transplantation, current cadaver-based procedures are limited by the short shelf-life of donor tissue. Electron-beam (E-beam) sterilisation extends this shelf-life from weeks to years but there are few published studies of its use. We demonstrated that E-beam-irradiated corneas are a viable source of lenticules for implantation. We conducted in vitro, in vivo, and ex vivo comparisons of E-beam and fresh corneal lenticules. The only differences exhibited by E-beam-treated lenticules were reduced expression of glycosaminoglycans, resulting in greater tissue compression and lower refraction suggesting that a thicker cut is required to achieve the same optical and refractive outcome; and lower Young's modulus indicating extra care with handling.
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Affiliation(s)
- Arun J Thirunavukarasu
- Tissue Engineering and Cell Therapy Group, Singapore Eye Research Institute, Singapore; University of Cambridge School of Clinical Medicine, Cambridge, United Kingdom
| | - Evelina Han
- Tissue Engineering and Cell Therapy Group, Singapore Eye Research Institute, Singapore
| | - Anu Maashaa Nedumaran
- School of Materials Science and Engineering, Nanyang Technological University, Singapore
| | | | | | | | - Yu-Chi Liu
- Tissue Engineering and Cell Therapy Group, Singapore Eye Research Institute, Singapore; Singapore National Eye Centre, Singapore; Ophthalmology and Visual Sciences Academic Clinical Programme, Duke-NUS Medical School, Singapore
| | - Valencia Foo
- Tissue Engineering and Cell Therapy Group, Singapore Eye Research Institute, Singapore; Singapore National Eye Centre, Singapore
| | - Bertrand Czarny
- School of Materials Science and Engineering, Nanyang Technological University, Singapore
| | - Andri K Riau
- Tissue Engineering and Cell Therapy Group, Singapore Eye Research Institute, Singapore; Ophthalmology and Visual Sciences Academic Clinical Programme, Duke-NUS Medical School, Singapore.
| | - Jodhbir S Mehta
- Tissue Engineering and Cell Therapy Group, Singapore Eye Research Institute, Singapore; School of Materials Science and Engineering, Nanyang Technological University, Singapore; Singapore National Eye Centre, Singapore; Ophthalmology and Visual Sciences Academic Clinical Programme, Duke-NUS Medical School, Singapore.
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Zhang H, Deng Y, Li Z, Tang J. Update of Research Progress on Small Incision Lenticule Extraction (SMILE) Lenticule Reuse. Clin Ophthalmol 2023; 17:1423-1431. [PMID: 37251989 PMCID: PMC10216859 DOI: 10.2147/opth.s409014] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2023] [Accepted: 05/12/2023] [Indexed: 05/31/2023] Open
Abstract
The SMILE lenticule is a complete corneal stroma that is removed from SMILE surgery. Since the increasing number of SMILE surgeries, a large number of SMILE lenticules have been produced, so the reuse and preservation of the stromal lens has become a research hotspot. Due to the rapid development of the preservation and clinical reuse of SMILE lenticules, there have been many related studies in recent years, so we updated it on this basis. We searched PubMed, Web of Science, Embase, Elsevier Science, CNKI, WANFANG Data and other databases for all articles published on the preservation and clinical reuse of SMILE lenticules, screened useful articles, selected relevant articles published in the last five years as the main body for summary, and then reached a conclusion. The existing preservation methods of SMILE lenticule include Moist chamber storage at low temperature, cryopreservation technique dehydrating agent and corneal storage medium, which have their own advantages and disadvantages. Presently, smile lenticules can be used for the treatment of corneal ulcers and perforations, corneal tissue defects, hyperopia, presbyopia and keratectasia, which have been proven to be relatively effective and safe. More research on smile lenticule reuse needs to be carried out to confirm its long-term efficacy.
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Affiliation(s)
- Hao Zhang
- Department of Ophthalmology, West China Hospital, Sichuan University, Chengdu, Sichuan, People’s Republic of China
| | - Yingping Deng
- Department of Ophthalmology, West China Hospital, Sichuan University, Chengdu, Sichuan, People’s Republic of China
| | - Zeshi Li
- West China Clinical Medical College, Sichuan University, Chengdu, Sichuan, People’s Republic of China
| | - Jing Tang
- Department of Ophthalmology, West China Hospital, Sichuan University, Chengdu, Sichuan, People’s Republic of China
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Hu X, Wei R, Liu C, Wang Y, Yang D, Sun L, Xia F, Liu S, Li M, Zhou X. Recent advances in small incision lenticule extraction (SMILE)-derived refractive lenticule preservation and clinical reuse. ENGINEERED REGENERATION 2023. [DOI: 10.1016/j.engreg.2023.01.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
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Yu N, Chen S, Yang X, Hou X, Wan L, Huang Y, Qiu J, Li Y, Zheng H, Wei H, Zeng C, Lei L, Chen P, Yang Y, Quan D, Zhuang J, Yu K. Comparison of fresh and preserved decellularized human corneal lenticules in femtosecond laser-assisted intrastromal lamellar keratoplasty. Acta Biomater 2022; 150:154-167. [PMID: 35896137 DOI: 10.1016/j.actbio.2022.07.035] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2021] [Revised: 07/14/2022] [Accepted: 07/19/2022] [Indexed: 11/30/2022]
Abstract
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.
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Affiliation(s)
- Na Yu
- State Key Laboratory of Ophthalmology, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Zhongshan Ophthalmic Center, Sun Yat-sen University, P. R. China 510060
| | - Shuilian Chen
- State Key Laboratory of Ophthalmology, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Zhongshan Ophthalmic Center, Sun Yat-sen University, P. R. China 510060
| | - Xifeng Yang
- PCFM Lab, GD HPPC Lab, School of Chemistry, and Guangdong Functional Biomaterials Engineering Technology Research Center, School of Materials Science and Engineering, Sun Yat-Sen University, P. R. China 510275
| | - Xiangtao Hou
- State Key Laboratory of Ophthalmology, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Zhongshan Ophthalmic Center, Sun Yat-sen University, P. R. China 510060
| | - Linxi Wan
- State Key Laboratory of Ophthalmology, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Zhongshan Ophthalmic Center, Sun Yat-sen University, P. R. China 510060
| | - Yuke Huang
- State Key Laboratory of Ophthalmology, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Zhongshan Ophthalmic Center, Sun Yat-sen University, P. R. China 510060
| | - Jin Qiu
- State Key Laboratory of Ophthalmology, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Zhongshan Ophthalmic Center, Sun Yat-sen University, P. R. China 510060
| | - Yan Li
- State Key Laboratory of Ophthalmology, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Zhongshan Ophthalmic Center, Sun Yat-sen University, P. R. China 510060
| | - Hua Zheng
- State Key Laboratory of Ophthalmology, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Zhongshan Ophthalmic Center, Sun Yat-sen University, P. R. China 510060
| | - Han Wei
- State Key Laboratory of Ophthalmology, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Zhongshan Ophthalmic Center, Sun Yat-sen University, P. R. China 510060
| | - Chenguang Zeng
- Guangzhou Sun-shing Biotech Co., Ltd, P. R. China 510060
| | - Lei Lei
- State Key Laboratory of Ophthalmology, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Zhongshan Ophthalmic Center, Sun Yat-sen University, P. R. China 510060
| | - Pei Chen
- State Key Laboratory of Ophthalmology, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Zhongshan Ophthalmic Center, Sun Yat-sen University, P. R. China 510060
| | - Ying Yang
- State Key Laboratory of Ophthalmology, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Zhongshan Ophthalmic Center, Sun Yat-sen University, P. R. China 510060
| | - Daping Quan
- PCFM Lab, GD HPPC Lab, School of Chemistry, and Guangdong Functional Biomaterials Engineering Technology Research Center, School of Materials Science and Engineering, Sun Yat-Sen University, P. R. China 510275.
| | - Jing Zhuang
- State Key Laboratory of Ophthalmology, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Zhongshan Ophthalmic Center, Sun Yat-sen University, P. R. China 510060.
| | - Keming Yu
- State Key Laboratory of Ophthalmology, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Zhongshan Ophthalmic Center, Sun Yat-sen University, P. R. China 510060.
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Santra M, Liu YC, Jhanji V, Yam GHF. Human SMILE-Derived Stromal Lenticule Scaffold for Regenerative Therapy: Review and Perspectives. Int J Mol Sci 2022; 23:ijms23147967. [PMID: 35887309 PMCID: PMC9315730 DOI: 10.3390/ijms23147967] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2022] [Revised: 07/10/2022] [Accepted: 07/18/2022] [Indexed: 12/13/2022] Open
Abstract
A transparent cornea is paramount for vision. Corneal opacity is one of the leading causes of blindness. Although conventional corneal transplantation has been successful in recovering patients’ vision, the outcomes are challenged by a global lack of donor tissue availability. Bioengineered corneal tissues are gaining momentum as a new source for corneal wound healing and scar management. Extracellular matrix (ECM)-scaffold-based engineering offers a new perspective on corneal regenerative medicine. Ultrathin stromal laminar tissues obtained from lenticule-based refractive correction procedures, such as SMall Incision Lenticule Extraction (SMILE), are an accessible and novel source of collagen-rich ECM scaffolds with high mechanical strength, biocompatibility, and transparency. After customization (including decellularization), these lenticules can serve as an acellular scaffold niche to repopulate cells, including stromal keratocytes and stem cells, with functional phenotypes. The intrastromal transplantation of these cell/tissue composites can regenerate native-like corneal stromal tissue and restore corneal transparency. This review highlights the current status of ECM-scaffold-based engineering with cells, along with the development of drug and growth factor delivery systems, and elucidates the potential uses of stromal lenticule scaffolds in regenerative therapeutics.
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Affiliation(s)
- Mithun Santra
- Corneal Regeneration Laboratory, Department of Ophthalmology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15213, USA; (M.S.); (V.J.)
| | - Yu-Chi Liu
- Tissue Engineering and Cell Therapy Group, Singapore Eye Research Institute, Singapore 169856, Singapore;
- Ophthalmology and Visual Sciences Academic Clinical Program, Duke-NUS Medical School, Singapore 169857, Singapore
| | - Vishal Jhanji
- Corneal Regeneration Laboratory, Department of Ophthalmology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15213, USA; (M.S.); (V.J.)
| | - Gary Hin-Fai Yam
- Corneal Regeneration Laboratory, Department of Ophthalmology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15213, USA; (M.S.); (V.J.)
- Tissue Engineering and Cell Therapy Group, Singapore Eye Research Institute, Singapore 169856, Singapore;
- McGowan Institute for Regenerative Medicine, University of Pittsburgh, Pittsburgh, PA 15213, USA
- Correspondence:
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Yam GHF, Bandeira F, Liu YC, Devarajan K, Yusoff NZBM, Htoon HM, Mehta JS. Effect of corneal stromal lenticule customization on neurite distribution and excitatory property. J Adv Res 2021; 38:275-284. [PMID: 35572401 PMCID: PMC9091752 DOI: 10.1016/j.jare.2021.09.004] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2021] [Revised: 09/05/2021] [Accepted: 09/14/2021] [Indexed: 11/29/2022] Open
Abstract
Refractive SMILE-derived stromal lenticules are useful in various tissue-engineering approach for therapeutics, of which they are required to be customized before implantation. Excimer laser-mediated reshaping, riboflavin-UVA-induced collagen crosslinking and chemical decellularization significantly removed lenticule neurites, but the residual neurites retained excitatory response. Reinnervation occurred in the decellularized lenticules, indicating a potential of nerve regeneration. Stromal lenticules, as a unique collagen-rich biomaterial with high transparency, refractivity and mechanically robust, together with the ability of neurite regeneration, could hold a potential for various ophthalmic applications.
Introduction Refractive stromal lenticules from Small Incision Lenticule Extraction (SMILE), though usually discarded, hold a potential for various ophthalmic applications, including refractive correction, stromal volume expansion, and biomechanical strengthening of the cornea. Objectives To investigate the effect of lenticule customization on lenticule neurite length profile and the excitatory response (calcium signaling) and the potential of reinnervation. Methods Human and porcine stromal lenticules were treated by (1) excimer laser reshaping, (2) ultraviolet A-riboflavin crosslinking (CXL), and (3) decellularization by sodium dodecyl sulfate (SDS), respectively. The overall neurite scaffold immuno-positive to TuJ1 (neuron-specific class III β-tubulin) expression and population of active neurite fragments with calcium response revealed by L-glutamate-induced Fluo-4-acetoxymethyl ester reaction were captured by wide-field laser-scanning confocal microscopy, followed by z-stack image construction. The NeuronJ plugin was used to measure neurite lengths for TuJ1 (NL-TuJ1) and calcium signal (NL-Ca). Reinnervation of lenticules was examined by the ex vivo grafting of chick dorsal root ganglia (DRG) to the decellularized human lenticules. Differences between groups and controls were analyzed with ANOVA and Mann-Whitney U test. Results The customization methods significantly eliminated neurites inside the lenticules. NL-TuJ1 was significantly reduced by 84% after excimer laser reshaping, 54% after CXL, and 96% after decellularization. The neurite remnants from reshaping and CXL exhibited calcium signaling, indicative of residual excitatory response. Re-innervation occurred in the decellularized lenticules upon stimulation of the grafted chick embryo DRG with nerve growth factor (NGF 2.5S). Conclusion All of the lenticule customization procedures reduced lenticule neurites, but the residual neurites still showed excitatory potential. Even though these neurite remnants seemed minimal, they could be advantageous to reinnervation with axon growth and guidance after lenticule reimplantation for refractive and volume restoration of the cornea.
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