Increased hyaluronan synthase-2 mRNA expression and hyaluronan accumulation with choroidal thickening: response during recovery from induced myopia.
OBJECTIVE
Several studies have convincingly shown that in chicks, compensation for imposed focus involves immediate changes in choroid thickness. The molecular events associated with choroidal thickening and the regulation of the choroidal response are largely unknown.


METHODS
Form-deprivation myopia was induced in the right eyes of 2-day-old chicks by the application of translucent occluders for 10 days and was followed by unrestricted vision for an additional 1 to 20 days (recovery). Individual choroids were isolated from treated and control eyes and used for reverse transcription-quantitative PCR, hyaluronan (HA) localization with biotinylated hyaluronic acid binding protein (b-HABP), and analyses of HA size and concentration by size exclusion chromatography-multiangle laser light scattering (SEC-MALLS).


RESULTS
HAS2 gene expression increased significantly after 6 hours of unrestricted vision (>7-fold) and peaked at 24 hours (>9-fold). In untreated eyes, HA was localized to perivascular sheaths of larger choroidal blood vessels; however, after 4 to 15 days of recovery, intense labeling for HA was detected throughout the thickened choroidal stroma. Analyses of choroidal HA by SEC-MALLS indicated that HA concentration was significantly increased in recovering choroids compared with controls after 4 to 8 days of recovery (≈3.5-fold).


CONCLUSIONS
Newly synthesized HA accumulates in the choroidal stroma of recovering eyes and is most likely responsible for the stromal swelling observed during recovery from myopia. This HA accumulation is initiated by a rapid increase in choroidal expression of the HAS2 gene in response to myopic defocus.
Rada
Jody A Summers
JA
Departments of Cell Biology, University of Oklahoma Health Science Center, Oklahoma City, OK 73104, USA. jody-rada@ouhsc.edu
Wiechmann
Allan F
AF
Hollaway
Lindsey R
LR
Baggenstoss
Bruce A
BA
Weigel
Paul H
PH
D000818:Animals; D000831:Animals, Newborn; D002645:Chickens; D002829:Choroid / Q000378:metabolism* / Q000473:pathology*; D002850:Chromatography, Gel; D004195:Disease Models, Animal; D015971:Gene Expression Regulation, Enzymologic / Q000502:physiology*; D014453:Glucuronosyltransferase / Q000235:genetics*; D006820:Hyaluronic Acid / Q000096:biosynthesis*; D006984:Hypertrophy; D008297:Male; D009216:Myopia / Q000473:pathology*; D012333:RNA, Messenger / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012683:Sensory Deprivation
D012333:RNA, Messenger; D006820:Hyaluronic Acid; D014453:Glucuronosyltransferase