Propriedades anisotrópicas e refrativas de córneas de coelhos, após implantação de inlays de colágeno tipo I extraído de tendão flexor digital superficial de bovino
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Data
2019-04-05
Autores
Barros Sobrinho, Alexandre Augusto Franchi de [UNESP]
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Editor
Universidade Estadual Paulista (Unesp)
Resumo
Membranas a base de colágeno tipo I extraído de tendão flexor digital superficial bovino foram estudados como possível matéria prima para confecção de inlays corneais. Elas foram implantadas nos estromas corneais de olhos direitos de 16 coelhos da raça Nova Zelândia Branco, adultos, machos ou fêmeas, em higidez sistêmica. Um “bolso” foi criado na região central de cada córnea para implantação e posicionamento da membrana (inlay) dentro do estroma anterior (grupo CM, 16 coelhos). Córneas com “bolso”, sem implantação de membranas (grupo SM, 16 coelhos), bem como córneas intactas (grupo controle, 4 coelhos sem qualquer procedimento cirúrgico) foram estudadas. Os grupos CM e SM foram avaliados clinicamente quanto a presença de blefarospasmo, hiperemia conjuntival, edema, secreção ocular e neovascularização e quanto às propriedades refrativas e a curvatura da córnea imediatamente antes (basal) e transcorridos 3, 7, 14, 21 e 28 dias de pós-operatório. Quatro animais dos grupos CM e SM, escolhidos ao acaso, foram submetidos à eutanásia ativa, em diferentes tempos, para colheita de córneas, as quais juntamente com córneas intactas do grupo controle, foram processadas para estudos comparativos em anisotropias ópticas (birrefringências total, de forma e intrínseca). Todas as variáveis contínuas foram testadas para a normalidade estatística. Diferenças com p < 0,05 foram consideradas significativas. Os procedimentos cirúrgicos realizados na córnea dos animais do grupo SM não alteraram a refração (p = 0,479). As córneas no grupo CM apresentaram-se com hipermetropia, astigmatismo e equivalente esférico alterados (vs. basal) a partir do terceiro dia de pós-operatório, e esses parâmetros se mantiveram alterados até o vigésimo oitavo dia de avaliação (p < 0,01). A curvatura corneal não foi alterada pelos procedimentos realizados nos grupos SM (p=0,3) e CM (p=0,28). Observaram-se elevações nas birrefringências totais e de forma das córneas nos grupos CM e SM, nos diferentes tempos avaliados, comparativamente às córneas no grupo controle. As proporções de aumento da birrefringência total foram de 4,15%, 2,98%, 2,99% e 2,79% no grupo CM e de 2,76%, 0,19%, 3,14% e 3,36% no grupo SM, aos 7, 14, 21 e 28 dias de pós-operatório, respectivamente. Os valores de birrefringência intrínseca oscilaram nos grupos estudados e entre os diferentes tempos de avaliação, representando mudanças em “turnover” associadas com remodelamento estromal. A membrana colagênica, à luz da histopatologia, mostrou-se segura, de degradação lenta, não tóxica e biocompatível com o tecido corneal de coelhos. Ademais, alterou tanto a refração corneal quanto a birrefringência total no curto prazo, porém sem alterar a curvatura corneal. Ela é portanto um material promissor para estudos futuros visando aperfeiçoamento e uso como inlays.
Membranes based on type I collagen extracted from bovine superficial digital flexor tendon were studied as a possible raw material for making corneal inlays. They were implanted in the right-eye, on the corneal stroma of 16 New Zealand White rabbits, male or female, adults, in apparently systemic health. A "pocket" was created in the central region of the cornea for implantation and positioning of the membrane (inlay) within the anterior stroma (CM group, 16 rabbits). Corneas with pocket, without implantation of membranes (SM group, 16 rabbits), as well as intact corneas (control group, 4 rabbits without any surgical procedure) were studied. The CM and SM groups were clinically evaluated for the presence of blepharospasm, conjunctival hyperemia, edema, ocular secretion and neovascularization, and on the refractive properties and curvature of the cornea immediately before (baseline) and after 3, 7, 14, 21 and 28 days of the postoperative period. Four animals, randomly choose from CM and SM groups were submitted to active euthanasia at different times to harvest the corneas, which, together with intact corneas from the control group, were processed for comparative studies in optical anisotropy (total, form and intrinsic birefringences). All continuous variables were tested for statistical normality. Differences with p <0.05 were considered significant. Surgical procedures performed on the corneas of the SM group did not alter the refraction (p = 0.479). The corneas in the CM group presented with altered hipermetropy, astigmatism and sferical equivalent (vs. basal) from the third postoperative day (p <0.01) onwards, and those changes were maintained until the twenty-eighth day of evaluation. The corneal curvature was not altered by the procedures performed in the SM (p = 0.3) and CM (p = 0.28) groups. Elevations in total and form birefringence of the corneas were observed in the CM and SM groups at the different evaluated times, compared to the corneas in the control group. The proportions of increase of total birefringence were 4.15%, 2.98%, 2.99% and 2.79% in the CM group and 2.76%, 0.19%, 3.14% and 3, 36% in the SM group at 7, 14, 21 and 28 postoperative days, respectively. The intrinsic birefringence values oscillated in the studied groups and between the different evaluation times, representing changes in turnover associated with stromal remodeling. The collagen membrane, on the histopathological evaluation, was shown to be safe, to have a slow degradation time, to be non-toxic and biocompatible with rabbit corneal tissue. In addition, it altered both the corneal refraction and the total birefringence in the short term, but without altering the corneal curvature. It is, therefore, a promising material for future studies aiming the improvement and use as an inlay.
Membranes based on type I collagen extracted from bovine superficial digital flexor tendon were studied as a possible raw material for making corneal inlays. They were implanted in the right-eye, on the corneal stroma of 16 New Zealand White rabbits, male or female, adults, in apparently systemic health. A "pocket" was created in the central region of the cornea for implantation and positioning of the membrane (inlay) within the anterior stroma (CM group, 16 rabbits). Corneas with pocket, without implantation of membranes (SM group, 16 rabbits), as well as intact corneas (control group, 4 rabbits without any surgical procedure) were studied. The CM and SM groups were clinically evaluated for the presence of blepharospasm, conjunctival hyperemia, edema, ocular secretion and neovascularization, and on the refractive properties and curvature of the cornea immediately before (baseline) and after 3, 7, 14, 21 and 28 days of the postoperative period. Four animals, randomly choose from CM and SM groups were submitted to active euthanasia at different times to harvest the corneas, which, together with intact corneas from the control group, were processed for comparative studies in optical anisotropy (total, form and intrinsic birefringences). All continuous variables were tested for statistical normality. Differences with p <0.05 were considered significant. Surgical procedures performed on the corneas of the SM group did not alter the refraction (p = 0.479). The corneas in the CM group presented with altered hipermetropy, astigmatism and sferical equivalent (vs. basal) from the third postoperative day (p <0.01) onwards, and those changes were maintained until the twenty-eighth day of evaluation. The corneal curvature was not altered by the procedures performed in the SM (p = 0.3) and CM (p = 0.28) groups. Elevations in total and form birefringence of the corneas were observed in the CM and SM groups at the different evaluated times, compared to the corneas in the control group. The proportions of increase of total birefringence were 4.15%, 2.98%, 2.99% and 2.79% in the CM group and 2.76%, 0.19%, 3.14% and 3, 36% in the SM group at 7, 14, 21 and 28 postoperative days, respectively. The intrinsic birefringence values oscillated in the studied groups and between the different evaluation times, representing changes in turnover associated with stromal remodeling. The collagen membrane, on the histopathological evaluation, was shown to be safe, to have a slow degradation time, to be non-toxic and biocompatible with rabbit corneal tissue. In addition, it altered both the corneal refraction and the total birefringence in the short term, but without altering the corneal curvature. It is, therefore, a promising material for future studies aiming the improvement and use as an inlay.
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Palavras-chave
Birrefringência, Biomaterial, Colágeno, Córnea, Inlay, Curvatura corneal