Ex vivo expansion of corneolimbal stem cells for ocular surface reconstruction
Corneal epithelial stem cells reside in limbus, a special structure located at the corneoscleral junction. Extensive ocular surface trauma or inflammation can often lead to loss of limbal stem cells, known as limbal deficiency. The hallmarks of limbal stem cell deficiency are conjunctival invasion of corneal surface, poor epithelial wound healing, corneal neovascularization and inflammation. The autologous or allogenic limbal stem cells can be cultivated and expanded in special tissue culture with various matrix carries including amniotic membrane. The expanded source may provide a viable corneal stem cell source for ocular surface rehabilitation.
Molecular genetics of corneal dystrophies
Corneal epithelial/stromal dystrophies are a group of inherited corneal conditions characterized by abnormal protein aggregations with resultant corneal opacities and recurrent epithelial breakdowns. Mutations of keratoepithelin (KE), an extracellular matrix protein also known as TGFBI or BGH3 have been identified in the affected families. KE mutations can cause either amyloid formations (such as in various types of corneal lattice dystrophy) or amorphous aggregates (such as in corneal granular dystrophy or Avellino dystrophy). The molecular basis dictating the clinical phenotype has been unclear. The KE gene is located in human chromosome 5q31 and regulated by TGF-b (transforming growth factor- beta). This lab has previously identified the KE gene promoter. However, the activating mechanism of KE gene promoter has not been delineated. Studies on the regulation of gene promoter and related KE protein expression may reveal the pathogenesis of various corneal epithelial/stromal dystrophies and facilitate the development of novel therapeutic strategies for related corneal pathology.
Molecular therapy for corneal dystrophies and hereditary glaucoma
RNA interference has been identified as a powerful tool for gene silencing. It can also be used to suppress expression of untoward genes of inherited conditions. We have developed several siRNAs (small interfering RNA containing short double-stranded RNAs) as a molecular silencer to knock down gene expression of KE and myocilin (a protein purportedly responsible for certain types of hereditary open-angle glaucoma), respectively. Using appropriate siRNA molecules, RNAi can selectively suppress the expression of KE and myocilin protein in vitro, respectively. Anterior segment of the eye is readily accessible for topical delivery of therapeutics to the target tissues such as cornea or trabecular meshwork. We are investigating the feasibility of delivering siRNAs to anterior segment as a new potential therapeutic strategy for inherited ocular conditions such as corneal dystrophies and glaucoma.