Reasearches showed that α-melanocyte-stimulating hormone (α-MSH) inhibits inflammation and ameliorates the ocular surface abnormalities in a scopolamine-induced dry eye rat model, and the managing effect of sodium carboxymethylcellulose (CMC) on dry eyes also has been determined.However, whether α-MSH can enhance the therapeutic effects of CMC remains to be investigated.

This study was to investigate the protective effects of α-MSH combined with CMC on ocular surface in a scopolamine-induced dry eye rat model.

Sixty clean female Wistar rats were randomly divided into normal control group, model control group, NaCl group, CMC group, α-MSH group and α-MSH+ CMC group, and 10 rats for each group.The dry eye models were established by subcutaneous injection of scopolamine hydrobromide at 9: 00, 12: 00, 15: 00 and 18: 00 per day for 28 days.0.9% NaCl solution, 1×10^-3 mg/ml α-MSH solution, 0.5% CMC eye drop, and 1×10^-3 mg/ml α-MSH+ 0.5% CMC solution were topically administered twice a day (8: 00, 17: 00) since the initial day of modeling according to grouping.Shirmer Ⅰ test (SⅠt), breakup time of tear film (BUT) and corneal fluorescence staining were performed before and 7, 14, 21, 28 days after the application of drugs.At 28 days following the administration of drugs, the eyeballs of the rats were collected.Hemotoxylin and eosin staining was employed to examine the morphology of corneas, and periodic acid schiff (PAS) staining was used to count the conjunctival goblet cells.This study protocol was approved by Experimental Animal Ethic Committee of Tianjin Medical University(SYXK 2009-0001), and the use and care of the rats complied with ARVO Statement.

The SⅠt and BUT values were significantly reduced, and the corneal fluorescence staining scores were significantly increased over time following modeling in the model control group (all at P<0.01). No significant differences were found in the SⅠt, BUT and corneal fluorescence staining scores between model control group and NaCl group at various time points (all at P>0.05). At 7, 14 and 21 days after intervention, the SⅠt values were (4.800±0.789), (4.100±0.516) and (4.300±0.856)mm in the α-MSH+ CMC group, which were considerably higher than (2.875±0.719), (2.375±0.619) and (2.532±0.957)mm in the NaCl group (all at P<0.01). At 7 days after intervention, the BUT values were (4.938±1.843) seconds and (5.000±1.491) seconds in the α-MSH group and α-MSH+ CMC group, which were significantly higher than (3.250±1.000) seconds in the NaCl group (both at P<0.01). The corneal fluorescence staining scores in the CMC group, α-MSH group and α-MSH+ CMC group were significantly lower than that in the NaCl group, with the lowest score in the α-MSH+ CMC group (all at P<0.05). The thickening of corneal epithelial layer, corneal edema and arrangement disorder of corneal stroma were found in the model control group and NaCl group; while slight corneal edema and epithelial cell proliferation were exhibited in the α-MSH+ CMC group by hemotoxylin and eosin staining.PAS staining showed that the number of goblet cells was much more in the CMC group, α-MSH group and α-MSH+ CMC group than that in the model control group and NaCl group (all at P<0.01).

The sole application of α-MSH or CMC alleviates ocular surface damage and morphological abnormality to certain extent, and the combination of α-MSH and CMC generates more effective protection in comparison with sole administration of α-MSH or CMC.The early application of the drugs plays an improvement role in tear secretion and tear film stability in dry eyes.

Dry eyes/drug therapeutic; Ocular surface; Protection; Sodium carboxymethylcellulose; α-Melanocyte-stimulating hormone; Disease models; Rats, Wistar