Abstract
Purpose::
Bone marrow stem cells (BMSC) are multipotent and capable of differentiating to various cell types, e.g., myocardial cells, hepatocytes, neurons, epidermal and gastrointestinal epithelial cells. In present studies, we examined whether BMSC could differentiate to keratocan expressing cells: a characteristic of corneal keratocytes.
Methods::
Bone marrow cells obtained from green fluorescent mice were intrastromally injected into corneas of Kera-/- mice and also used to prepare chimera mice of lethally γ-irradiated Kera-/- mice via tail vein injection. Immunohistochemistry and western blot analysis with anti-keratocan antibodies were used to detect the expression of keratocan in the recipient Kera-/- mice.
Results::
Immunostaining confirmed that freshly isolated BMC were keratocan negative. Green BMC injected into corneal stroma began to change shape and assumed dendritic and polygonal morphology at one week of intrastromal injection. Keratocan expression was detected around green BMC in the corneal stroma. To make sure that BMC can indeed differentiate to corneal keratocytes, EGFP negative BMC isolated from Kera-Cre/ZEG mice were intrastromally injected to corneas of Kera-/- mice. In 6 days, injected BMC were EGFP positive and displayed a dendritic or polygonal morphology, suggesting the modification of ZEG transgene by Cre recombinase driven by keratocan promoter in Kera-Cre/ZEG BMC. Immunofluorescent staining revealed newly synthesized keratocan distributed around green BMC donor cells in the corneal stroma. In a second series of experiments, chimera mice were prepared by tail vein injection of green fluorescence BMC into γ-irradiated Kera-/- mice. Green cells were found in the corneal limbal region and conjunctiva 2 weeks after the BMC tail vein injection; after four weeks, green cells presented in most area of the cornea, and even central cornea; afterwards, the numbers of green cells with various cell shapes continuously increased with many green cells at corneal peripheral region displayed dendritic morphology at 4 weeks after BMC injection. Following epithelium debided corneas healed for 6 weeks, keratocan expression was detected in chimeric mouse corneal. In chimera mice at 12 weeks after BMC reconstitution, keratocan expression by the experimental mice was detected by western blot analysis without epithelium debridement.
Conclusions::
BMSC can differentiate to keratocan expressing cells: a characteristic of keratocyte.
Keywords: cornea: stroma and keratocytes • immunohistochemistry • transplantation