Background Human corneal endothelial cells undergo very little or no proliferation and respond to cell loss by migration and cellular enlargement. Significant cell loss or damage may result in corneal oedema, opacity and loss of vision. In vitro expansion of corneal endothelial cells (CECs) is a promising strategy for corneal regeneration. The transition zone (TZ) may be an alternative source of CECs. The objective of this study was to establish a protocol for TZ cell culture, and to determine their potential to proliferate and differentiate into cells that resemble CECs in vitro. Methods An explant culture protocol for the human TZ was established. Cell proliferation was assessed using 5‐ethynyl‐2’‐deoxyuridine (EdU) assay. The expression of stem cell and endothelial markers was assessed using immunohistochemistry and quantitative polymerase chain reaction. Results TZ cells can be passaged up to 12 times; cells became polygonal 3 to 4 passages before senescence. An average of 41% of cells incorporated EdU over a 5‐day period. TZ cells expressed the corneal endothelial proteins ZO‐1 and Na+/K+ ATPase, Col8A2, the periocular mesenchyme marker PITX2, and the neural crest stem cell markers Nestin and Sox10. TZ cells expressed mRNA of a range of neural crest, periocular mesenchyme, and corneal endothelial genes. Conclusions TZ cells can proliferate and differentiate into cells that resemble CECs, demonstrating their potential to be an alternative cell source for corneal endothelial cell therapy.

Insulin-like growth factor-II (IGF-II) deficiency occurs when a conceptus inherits an inactive gene from the father (Igf2m؉/p؊): fetal wet weight is reduced to 60% of wild-type, with the decline starting at E11. The umbilical cord vessels of mutant and wild-type were compared. At E8.0 -E8.5, the timing of somite formation and chorioallantoic fusion was not altered. At E14.5-E16.5, the left umbilical artery degenerated approximately 1 day later in Igf2m؉/p؊ conceptuses when compared with the wild-type. In the common umbilical artery at E15.5, muscle volume was reduced by one third in IGF-II deficiency. Treating the umbilical arteries as ideal tubes, the values of radius 4 /length suggest that blood flow through the placenta may be reduced by more than half in the Igf2m؉/p؊ conceptuses. Developmental Dynamics 233:88 -94, 2005.