BackgroundOcular alkali burns leads to corneal ulcer and angiogenesis and even corneal opacity. There is still no ideal treatment method. Studies showed that mesenchymal stem cells (MSCs) can repair corneal wound in vivo, but the specific mechanism is still not clear.

ObjectiveThis study aimed to observe the histopathological change after the early transplatation of bone marrow MSCs (BMSCs) for corneal alkali burn model in rabbits and explore the anti-inflammatory effects of MSCs after corneal alkali burn.

MethodsBone marrow of 4 ml was collected from 2-3 month-old Japanese rabbit. BMSCs were isolated and cultured from the bone marrow of rabbits, and the third generation of cells were used in this study. Cultured cells were identified by morphology and the expressions of surface markers. Corneal alkali burn models were extablished in the right eyes of 24 rabbits by attaching the filter paper with 0. 1% NaOH at the central cornea for 30 seconds, and then the models were randomized into 2 groups. BMSCs suspension of 300 μl (concentration 5×10 ⁶/μl) was subconjunctivally injected 1 hour after modeling in the BMSCs group, and equal volume of PBS was used in the same way in the PBS group. Corneal opacification was scored under the slim lamp microscope in 3, 14 and 28 days after injection. The polymorphonuclear neutrophils (PMNs) were counted by histopathological examination, and the expression of matrix metalloproteinase-2 (MMP-2) in the corneal tissue was evaluated by immunochemistry in various time points. The use and care of the rabbits followed the statement of ARVO.

ResultsThe rabbit BMSCs were plastic-adherent cells that exhibited a fibroblast-like shape. Cultrued cells highly expressed surface adhesion molecular markers CD29 and CD90 (99. 18% and 97. 94%) and lowly expressed hematopoietic cell markers CD34 and CD31 (0. 74% and 0. 15%). Opacification of cornea, defect of corneal epithelium, stromal edema and neovascularization appeared after modeling. In 14 days and 28 days after modeling, the opacification scores in the BMSCs group were 2. 37±0. 52 and 2. 25±0. 50, which were significantly lower than 3. 00±0. 53 and 3. 25±0. 50 in the PBS group ( t=2. 376, 2. 828, both at P<0. 05). After subconjunctival injection, the number of PMNs was (34. 17±1. 85) /12 fields and (25. 64±3. 86)/12 fields in the BMSCs group, showing significant decrease in comparison with (42. 70±1. 54) /12 fields and (32. 67±1. 42)/12 fields in the PBS group ( t=10. 021, 4. 832, both at P=0. 000). The expression levels of MMP-2 ( A value) in cornea were 0. 388±0. 016 and 0. 384±0. 006 in the BMSCs group, with considerable decreases in comparison with 0. 438±0. 006 and 0. 412±0. 005 in the PBS group ( t=10. 205, 13. 514, both at P=0. 000).

ConclusionsEarly transplantation of BMSCs can arrest the occurrance of corneal ulcer by suppressing the infiltration of PMNs, alleviateing the inflammation reaction, downregulating the expression of MMP-2 in cornea and inhibiting the degradation of stromal collagen fibers.