Modified acellular porcine corneal matrix in deep lamellar transplantation of rabbit cornea

Structure and properties of the acellular porcine cornea irradiated with electron beam and its in-situ implantation

Different sterilization doses of the electron beam (E-beam) will change the properties of biomaterials and affect their clinical application. Acellular porcine cornea (APC) is a promising corneal substitute to alleviate the shortage of corneal resources. The residual DNA was significantly reduced to 18.50 ± 3.19 ng/mg, and the clearance rate of α-Gal was close to 100% after the treatment with freezing-thawing combined enzyme, indicating that the decellularization was effective. The effects of different E-beam doses at 0, 2, 8, 15, and 25 kGy on the APC were studied. With the increase in irradiation dose, the transmittance, tensile strength, and swelling ratio of APC gradually decreased, but the resistance to enzymatic degradation was stronger than that of non-irradiated APC, especially at 8 kGy. The structure of APC was denser after irradiation, but the dose of 25 kGy could cause partial collagen fiber fracture and increase the pore size. The cell viability of the APC irradiated by 15 and 25 kGy were greater than 80%. After the implantation in rabbit corneas, there was no obvious neovascularization and inflammation, but the dose of 25 kGy had a more destructive effect on the chemical bonds of collagen, which made the APC easier to be degraded. The thickness of APC in the 25 kGy group was thinner than that in the 15 kGy group 1 year after surgery, and the epithelium grew more slowly, so the E-beam dose of 15 kGy might be more suitable for the sterilization of APC.

Properties of Dual-Crosslinked Collagen-Based Membranes as Corneal Repair Material

Corneal disease has become the second leading cause of blindness in the world. Corneal transplantation is currently considered to be one of the common treatments for vision loss. This paper presents a novel approach utilizing dual-crosslinked membranes composed of polyrotaxane multiple aldehydes (PRAs), 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC), and N-hydroxysuccinimide (NHS) in the development process. Collagen was crosslinked, respectively, by EDC/NHS and PRAs to form stable amide bonds and imine groups. Through the formation of a double interpenetrating network, dual-crosslinked (Col-EDC-PRA) membranes exhibited enhanced resistance to collagenase degradation and superior mechanical properties compared to membranes crosslinked with a single crosslinker. Furthermore, Col-EDC-PRA membranes display favorable light transmittance and water content characteristics. Cell experiments showed that Col-EDC-PRA membranes were noncytotoxic and were not significantly different from other membranes. In a rabbit keratoplasty model, corneal stromal repair occurred at 5 months, evidenced by the presence of stromal cells and neo-stroma, as depicted in hematoxylin-eosin-stained histologic sections and optical coherence tomography images of the anterior segment. Moreover, there was no inflammation and corneal neovascularization, as well as no corneal rejection reaction in the surgical area. Overall, the results demonstrated that the dual-crosslinked membranes served effectively for corneal tissue regeneration after corneal defect.

Properties of the acellular porcine cornea crosslinked with UVA/riboflavin as scaffolds for Boston Keratoprosthesis

The Boston Keratoprosthesis type I (B-KPro) is widely used in the world, but the lack of donor corneas limits its application. This study aims to prepare the acellular porcine cornea (APC) crosslinked with ultraviolet A (UVA)/riboflavin instead of donor corneas as the scaffold for B-KPro. Decellularization of freeze-thaw combined with biological enzymes resulted in approximately 5 ng/mg DNA residue, the a-Gal removal rate of 99%, and glycosaminoglycans retention at a high level of 46.66 ± 2.59 mg/mg. UVA/ riboflavin cross-linking was adopted to induce the formation of new chemical bonds between adjacent collagen chains in the corneal stroma to improve the mechanical properties and resistance to enzymatic hydrolysis. Through comprehensive analysis of the biomechanics, enzyme degradation, immunogenicity and histological structure of the APC crosslinked at different times, CL3 (irradiation conditions, 365 nm, 3 mW/cm, 80 min, both sides) was selected and transplanted into the rabbit cornea model through interlamellar keratoplasty and penetrating keratoplasty as the scaffold of the B-KPro. Compared with the native porcine cornea (NPC) and APC, the experiment of interlamellar pocket indicated that the structure of CL3 was homogeneous without degradation and vascularization in vivo at 12 weeks after surgery. Simultaneously, the results of transplantation of B-KPro showed complete epithelialization of CL3 within 1 week, and neovascularization of the cornea indicated rejection but could be controlled with immunosuppressants. At 3 months postoperatively, the lens of B-KPro remained transparent, and the structure of CL3 was compact and uniform, accompanied by the migration and proliferation of a large number of stromal cells without degradation, suggesting the CL3 could be a promising corneal substitute.

Lamellar Keratoplasty Using Acellular Bioengineering Cornea (BioCorneaVetTM) for the Treatment of Feline Corneal Sequestrum: A Retrospective Study of 62 Eyes (2018–2021)

Simple Summary

Corneal sequestrum is a specific and common corneal disease in cats. Surgery treatment is the recommended option. Acellular bioengineering cornea (ABC) is a popular and effective corneal transplantation material. However, no study has been published to evaluate the effectiveness and outcome of ABC lamellar transplantation for the treatment of feline corneal sequestrum (FCS). The purpose of this retrospective study was to evaluate the surgical effect of ABC lamellar transplantation in the treatment of FCS. All cats were diagnosed with FCS. All eyes received ABC lamellar transplantation for the first time, including 61 cats (62 eyes), aged 6–120 months. The average sequestrum size was 7.98 mm, with a medium of 7.75 mm (range, 4.75–11.75 mm), and the sequestrum thickness included 200 microns for 1 eye (1.61%), 300 microns for 28 eyes (45.16%), 400 microns for 29 eyes (46.77%), and 450 microns for 4 eyes (6.45%). All eyes retained vision after surgical treatment, and there was no recurrence during the follow-up period. This study has several limitations, including incomplete unification and standardization of data collection, some vacancies of follow-up time, inconsistency between then optical coherence tomography(OCT) examination and postoperative photo collection. Despite several limitations, our results show that ABC is easy to obtain and store, and has the choice of different sizes and thicknesses to achieve rapid corneal healing, and satisfactory visual and cosmetic effects in FCS treatment. Acellular bioengineering cornea can be a good alternative for the treatment of FCS.

Abstract

To retrospectively evaluate the effectiveness and outcome of lamellar keratoplasty using acellular bioengineering cornea (BioCorneaVet^TM) for the treatment of feline corneal sequestrum (FCS). The medical records of cats diagnosed with FCS that underwent lamellar keratoplasty with BioCorneaVet^TM between 2018 and 2021 with a minimum of 3 months of follow-up were reviewed. Follow-up examinations were performed weekly for 3 months, and then optical coherence tomography (OCT) examination was performed on select patients at 0, 3, 6, and 12 months post-operatively. A total of 61 cats (30 left eyes and 32 right eyes) were included. The Persian breed was overrepresented, 48/61 (78.69%). Four different thicknesses of acellular bioengineering cornea were used (200, 300, 400, or 450 microns), and the mean graft size was 8.23 mm (range, 5.00–12.00 mm). Minor complications were composed of partial dehiscence, and protrusion of the graft occurred in 7/62 eyes (11.29%). The median postoperative follow-up was 12.00 months (range, 3–41 months). A good visual outcome was achieved in 60/62 eyes (96.77%), and a mild to moderate corneal opacification occurred in 2/62 (3.23%). No recurrence of corneal sequestrum was observed. From the results, lamellar keratoplasty using acellular bioengineering cornea (BioCorneaVet^TM) is an effective treatment for FCS, providing a good tectonic support and natural collagen framework, and resulting in satisfactory visual and cosmetic effects.

The use of acellular porcine corneal stroma xenograft (BioCorneaVet™ ) for the treatment of deep stromal and full thickness corneal defects: A retrospective study of 40 cases (2019-2021)

OBJECTIVE

To document the effectiveness and outcome of corneal grafting using acellular porcine corneal stroma (APCS) for veterinary use (BioCorneaVet^™ ) to restore corneal integrity in dogs.

METHODS

A review of medical records of patients that underwent keratoplasty with APCS graft to repair deep corneal defects, descemetoceles, and perforations between 2019 and 2021 was carried out. Only animals with intact dazzle reflex, consensual PLR before the surgery and a minimum follow-up of four weeks were considered for the study, with forty dogs (1 eye each) meeting the inclusion criteria.

RESULTS

Brachycephalic breeds were the most frequently represented, and 20 right eyes and 20 left eyes were affected with 25 perforations, 8 descemetoceles, and 9 deep stromal defects (1 eye had both perforation and descemetocele). Most of the patients had concurrent ocular diseases or had undergone previous surgery on the other eye. Two different thickness of xenograft was used (300 or 450 µm), and the diameter ranged from 3 to 10 mm. Postoperative complications included mild to severe corneal vascularization, partial dehiscence, melting, and glaucoma. Follow-up time ranged from 28 to 797 days (mean: 233 days). Ocular integrity was maintained in 37/40 cases (92.5%), and vision was preserved in 36 cases (90%).

CONCLUSION

The use of APCS (BioCorneaVet^™ ) is an effective surgical treatment for deep stromal defects, descemetocele, and perforations in dogs, providing a good tectonic support and preserving anatomical integrity and vision. The cosmetic appearance was considered good in all the cases and continued to improve with time.