[Experimental study of glyceraldehyde cross-linking of posterior scleral on FDM in guinea pigs].
OBJECTIVE
The purpose of this study is to observe the effects of glyceraldehyde cross-linking on sclera biomechanical strength and experimental myopia.


METHODS
50 three weeks aged guinea pigs were randomly divided into 5 groups: A, B, C, D, E. Each group had 10 guinea pigs. The right eye was set as the experimental eye, the left eye was used as control. Group A: 7 days mask; Group B: 21 days mask, plus physiological saline retrobulbar injection at mask day 1, 8, 15; Group C: 21 days mask, plus 0.05 mol/L glyceraldehyde retrobulbar injection at mask day 1, 8, 15; Group D: 21 days mask, plus 0.5 mol/L glyceraldehyde retrobulbar injection at mask day 1, 8, 15; Group E: normal control group. Several parameters of 7 guinea pigs of each group were measured before and after deprivation (mask day 7, 14, 21), including ocular axial length, refractive error, ultimate stress (σmax) (MPa), ultimate strain(εmax) (%) and 6% elastic modulus (MPa). The effects of glyceraldehyde on adjacent tissues of the rest 3 guinea pigs were detected by histopathological and immunohistochemical studies. Differences between experiment eyes and contralateral, eyes were compared with paired t test and correlative analysis.


RESULTS
The experimental eyes appeared the increase of the the vitreous cavity length, the axial length and myopia after deprivation. In group A, group B and group C, the differences of the length of the vitreous cavity (group A (2.991 ± 0.078) mm, group B (2.961 ± 0.038) mm and group C (2.936 ± 0.021) mm), the axial length(group A (7.263 ± 0.133) mm, group B (7.732 ± 0.099) mm and group C (7.665 ± 0.055) mm) and refractive error (group A (-2.214 ± 2.881) D, group B (-4.525 ± 2.415) D and group C (-1.607 ± 0.866) D) between the experimental eye and the fellow eye was statistically significant (vitreous cavity = 3.234, 4.758, 7.608; Pvitreous cavity = 0.018, 0.002, 0.001; axial = 3.198,, 4.758, 7.608; Paxial = 0.019, 0.002, 0.000; refraction = -7.120, -4.020, -6.334; Prefraction = 0.000, 0.005, 0.001). In group D and group E, there is no difference between deprived eye and control eye about the length of the vitreous chamber as well as axial length (vitreous = 0.542, -0.646; Pvitreous cavity = 0.607, 0.539; axial = 0.542, -0.646; Paxial = 0.607, 0.539). The experimental eye ((-3.921 ± 0.874)D) and the fellow eye ((-3.321 ± 1.205)D) of group D, the difference of diopter was statistically significant (refraction = -3.154, Prefraction = 0.020). At the end of the experiment, the change of diopter of experimental eye of group B, C, D, E was significantly different (F = 61.249, P = 0.000). The difference of diopter change between group B ((8.800 ± 0.616) D), group C ( (7.236 ± 2.198) D), group D ( (6.271 ± 1.112) D) and the normal control group ((0.934 ± 0.158) D) was statistically significant (PB = 0.000, PC = 0.000, PD = 0.000). At the end of the experiment, the ultimate stress and 6% elastic modulus of group B experimental eye was (7.988 ± 3.677) MPa (P = 0.002) and (19.938 ± 4.871) MPa (P = 0.001), decreased 10.06% and 34.17% respectively. On the other hand the ultimate strain was (28.6 ± 3.6) % (P = 0.034), increased 19.17%. After the cross-linking treatment, the ultimate stress and 6% elastic modulus of group C experimental eye was (9.244 ± 0.806) MPa (P = 0.001) and (26.180 ± 4.388) MPa (P = 0.031) , decreased 23.13% and 13.34%, the ultimate strain was (26.2 ± 1.0) % (P = 0.016) , increased 12.93% separately. The ultimate stress of group D experimental eye was (12.476 ± 2.507) MPa (P = 0.580), decreased 5.50%, 6% elastic modulus was (30.446 ± 3.410) MPa (P = 0.314), increased 6.53%, ultimate strain was (23.8 ± 1.8) % (P = 0.253), decreased 4.42% respectively. Ultrastructure examination showed that, decreased scleral thickness with fibers lined up in order, without inflammatory cells Infiltration. Expressions of matrix metalloproteinases-2(MMP-2) mainly decrease in the episcleral tissue. The stroma of choroid, and the outer plexiform layer.


CONCLUSIONS
Glyceraldehyde is a safe and effective cross-linking agent that could significantly enhance the sclera biomechanical strength. Glyceraldehyde cross-linking method could effectively control the development of myopia in animal model.
Tianjin Eye Hospital, Tianjin Key Lab of Ophthalmology and Visual Science, Tianjin Eye Institute, Clinical College of Ophthalmology Tianjin Medical University, Tianjin 300020, China.
Ying
Y
Wang
Tianjin Eye Hospital, Tianjin Key Lab of Ophthalmology and Visual Science, Tianjin Eye Institute, Clinical College of Ophthalmology Tianjin Medical University, Tianjin 300020, China. Email: hanquanhong126@126.com.
Quanhong
Q
Han
Tianjin Eye Hospital, Tianjin Key Lab of Ophthalmology and Visual Science, Tianjin Eye Institute, Clinical College of Ophthalmology Tianjin Medical University, Tianjin 300020, China.
Fengmei
F
Han
Tianjin Eye Hospital, Tianjin Key Lab of Ophthalmology and Visual Science, Tianjin Eye Institute, Clinical College of Ophthalmology Tianjin Medical University, Tianjin 300020, China.
Yanhua
Y
Chu
Tianjin Eye Hospital, Tianjin Key Lab of Ophthalmology and Visual Science, Tianjin Eye Institute, Clinical College of Ophthalmology Tianjin Medical University, Tianjin 300020, China.
Kanxing
K
Zhao
D000818:Animals; D003432:Cross-Linking Reagents / Q000737:chemistry; D004195:Disease Models, Animal; D005556:Form Perception; D005985:Glyceraldehyde / Q000737:chemistry*; D006168:Guinea Pigs; D009216:Myopia / Q000188:drug therapy* / Q000473:pathology*; D012590:Sclera / Q000502:physiology*
D003432:Cross-Linking Reagents; D005985:Glyceraldehyde