Abstract
Purpose: :
This study sought to establish procedures to derive properly differentiated lens cells from undifferentiated human embryonic stem (ES) cells.
Methods: :
To generate large quantities of lens progenitor cells and differentiated lens cells, a human embryonic stem (hES) cell line called H1 was exposed to growth factors known to regulate lens development and the optimal sequence, timing and concentration of these factors was determined. Differentiation of hES cells was monitored by examining the sequential expression of lens crystallins and other markers of lens differentiation between the differentiated lens cells and actual human lens samples by quantitative RT-PCR, immunofluorescence and western immunobloting. The morphology of the differentiated lens cells was also evaluated by electron microscopy.
Results: :
Using growth factors known to regulate ectoderm and lens placode formation (BMP4, BMP7, FGF2 and noggin), in a two stage-experimental procedure, a majority of cells cultured for 12 days expressed PAX6, a lens-lineage specific transcription factor. After 15 days in culture, these cells subsequently expressed both of αA- and αB-crystallins. Next, various combinations of FGF2/Wnt3a/BMP4 and BMP7 were tested to examine lentoid body formation indicative of achieving the three-dimensional biconcave structures required for mature lens function The most efficient production of these structures, at day 35 of culture, was found using FGF2 and Wnt3a.
Conclusions: :
These studies identify a novel procedure to generate differentiated human lens cells from human ES and possibly from patient-specific induced pluripotent (iPS) cells. These de novo differentiated lens cells provide a unique tool to study diverse biological processes including progenitor lens formation, epithelial cell differentiation, fiber cell differentiation, lens protection and cataractogenesis.
Keywords: differentiation • crystallins • growth factors/growth factor receptors