Differential relative sulfation of Keratan sulfate glycosaminoglycan in the chick cornea during embryonic development.
OBJECTIVE
To investigate structural remodeling of the developing corneal stroma concomitant with changing sulfation patterns of keratan sulfate (KS) glycosaminoglycan (GAG) epitopes during embryogenesis and the onset of corneal transparency.


METHODS
Developing chick corneas were obtained from embryonic day (E)12 to E18 of incubation. Extracellular matrix composition and collagen fibril spacing were evaluated by synchrotron x-ray diffraction, hydroxyproline assay, ELISA (with antibodies against lesser and more highly sulfated KS), and transmission electron microscopy with specific proteoglycan staining.


RESULTS
A significant relative increase in highly sulfated KS epitope labeling occurred with respect to hydroxyproline content in the final week of chick development, as mean collagen interfibrillar distance decreased. Small KS PG filaments increased in frequency with development and were predominantly fibril associated.


CONCLUSIONS
The accumulation of highly sulfated KS during the E12 to E18 timeframe could serve to fine tune local matrix hydration and collagen fibril spacing during corneal growth, as gross dehydration and compaction of the stroma progress through the action of the nascent endothelial pump.
Liles
Melody
M
Structural Biophysics Group, School of Optometry and Vision Sciences, Cardiff University, Cardiff, Wales, United Kingdom.
Palka
Barbara P
BP
Harris
Anthony
A
Kerr
Briedgeen
B
Hughes
Clare
C
Young
Robert D
RD
Meek
Keith M
KM
Caterson
Bruce
B
Quantock
Andrew J
AJ
D000818:Animals; D002642:Chick Embryo; D003319:Corneal Stroma / Q000196:embryology* / Q000378:metabolism* / Q000648:ultrastructure; D047108:Embryonic Development; D004797:Enzyme-Linked Immunosorbent Assay; D016326:Extracellular Matrix Proteins / Q000378:metabolism; D024022:Fibrillar Collagens / Q000378:metabolism / Q000648:ultrastructure; D006909:Hydroxyproline / Q000378:metabolism; D007632:Keratan Sulfate / Q000378:metabolism* / Q000648:ultrastructure; D046529:Microscopy, Electron, Transmission; D013431:Sulfates / Q000378:metabolism; D014961:X-Ray Diffraction
D016326:Extracellular Matrix Proteins; D024022:Fibrillar Collagens; D013431:Sulfates; D007632:Keratan Sulfate; D006909:Hydroxyproline