Research on effects of vitamin A palmitate on repair of mechanical corneal epithelial defects and conjunctival goblet cells in rabbits

Abstract

Randomized controlled experimental study to investigate the influence of vitamin A palmitate and bovine recombinant basic fibroblast growth factor (bFGF) on repair of mechanical corneal epithelial defects, conjunctival epithelial cells and goblet cells in rabbits. One hundred and twenty New Zealand rabbits (all males) were selected to establish the mechanical corneal epithelial defects models (scratching out a round area with the diameter of 8 mm in the centre of cornea). Forty eight New Zealand rabbits were randomly divided into 4 groups: group A used lincomycin hydrochloride eye drops (LED) after the model had been established; group B used vitamin A palmitate eye gel and LED; group C used recombinant bFGF eye gel and LED; group D used vitamin A palmitate eye gel, bFGF eye gel and LED. Photo slit lamp examination and measurement of repaired area were performed on day 0, day 1, day 4 and day 7; transmission electron microscopy, histological microscope examination and impression cytology were performed on day 0, day 1, day 4 and day 7 to analysis the morphology and repairment of corneal epithelium, conjunctival epithelial cells and the goblet cells. The variants were tested using analysis of variance and Tukey's test. Statistic analysis showed that on day 1, the size of areas of repaired corneal epithelium was: group A(53.512 +/- 18.850) mm(2), group B (92.194 +/- 14.367) mm(2), group C (89.779 +/- 20.535) mm(2), group D (127.816 +/- 16.379) mm(2). The difference in size of repaired areas between different groups was statistically significant (F = 17.663, P = 0.000), with exception of the difference between groups B and C (P = 0.995). Conjunctival impression cytology showed that, the average number of conjunctival goblet cells per 740 microm x 550 microm at day 1 was decreased, group A (10.083 +/- 4.441), group B (10.667 +/- 3.551), group C (9.583 +/- 4.502), group D (9.167 +/- 5.606). The difference between these four groups was not significant (F = 0.239, P = 0.868). At day 4, the size of areas of repaired corneal epithelium was: group A (120.369 +/- 11.839) mm(2), group B (156.606 +/- 8.087) mm(2), group C (154.216 +/- 9.990) mm(2), group D (175.181 +/- 5.168) mm(2), which showed a significant difference between each two groups (F = 37.665, P = 0.000), with exception between groups B and C (P = 0.968). The average number of goblet cells at day 4 was recovered, which was: group A (41.250 +/- 4.575), group B (56.083 +/- 6.374), group C (48.417 +/- 4.562), group D (61.917 +/- 5.017), with a significant difference between these four groups (F = 36.210, P = 0.000). At day 7, the size of areas of repaired corneal epithelium had a statistical significance (F = 32.656, P = 0.000) between these four groups, which was group A (177.472 +/- 3.585) mm(2), group B (186.715 +/- 3.022) mm(2), group C (182.293 +/- 3.158) mm(2), group D (194.106 +/- 2.176) mm(2). The area of repaired corneal epithelium in group D was larger than that of other groups (P < 0.05). The average number of goblet cells was recovered significantly, which was: group A (63.167 +/- 11.488), group B (99.501 +/- 15.877), group C (82.015 +/- 9.175), group D (104.750 +/- 9.659). There was a significant difference in goblet cell number between these groups (F = 30.312, P = 0.000) with exception between groups B and D (P = 0.700). In transmission electron microscope examination of the cornea, we found that vitamin A palmitate and bFGF could both promote the development of intracellular conjunction. Vitamin A palmitate protected corneal epithelial cells, prevented cell keratinization, promoted proliferation and differentiation of corneal epithelial cells. In transmission electron microscopy examination of the conjunctiva, conjunctival goblet cells in groups B and D recovered well with rich secretary granules, which were quite different from groups A and C. Conjunctival epithelium of groups B, C and D were well-differentiated with tight intracellular conjunction. Vitamin A palmitate and bFGF could promote the repair of mechanical corneal epithelial defects and the development of intracellular conjunction. The effect is more significant when vitamin A palmitate is combined with bFGF. Vitamin A palmitate promotes regeneration of conjunctival goblet cells and can re-establish intracellular conjunction of conjunctival epithelium. The protective effect of vitamin A palmitate on conjunctival goblet cells is better than that of bFGF.