Changes in gene expression by trabecular meshwork cells in response to mechanical stretching.
OBJECTIVE
Trabecular meshwork (TM) cells appear to sense changes in intraocular pressure (IOP) as mechanical stretching. In response, they make homeostatic corrections in the aqueous humor outflow resistance, partially by increasing extracellular matrix (ECM) turnover initiated by the matrix metalloproteinases. To understand this homeostatic adjustment process further, studies were conducted to evaluate changes in TM gene expression that occur in response to mechanical stretching.


METHODS
Porcine TM cells were subjected to sustained mechanical stretching, and RNA was isolated after 12, 24, or 48 hours. Changes in gene expression were evaluated with microarrays containing approximately 8000 cDNAs. Select mRNA changes were then compared by quantitative reverse transcription-polymerase chain reaction (qRT-PCR). Western immunoblots were used to determine whether some of these changes were associated with changes in protein levels.


RESULTS
On the microarrays, 126 genes were significantly upregulated, and 29 genes were significantly downregulated at one or more time points, according to very conservative statistical and biological criteria. Of the genes that changed, several ECM regulatory genes, cytoskeletal-regulatory genes, signal-transduction genes, and stress-response genes were notable. These included several proteoglycans and matricellular ECM proteins composed of common repetitive binding domains. The results of analysis of mRNA changes in more than 20 selected genes by qRT-PCR supported the findings in the microarray analysis. Western immunoblots of several proteins demonstrated protein level changes associated with changes in the level of mRNA.


CONCLUSIONS
The expression of a variety of TM genes is significantly affected by mechanical stretching. These include several ECM proteins that contain multiple binding sites and may serve organizational roles in the TM. Several proteins that could contribute to the homeostatic modification of aqueous humor outflow resistance are also upregulated or downregulated.
Vittal
Vasavi
V
Casey Eye Institute, Oregon Health and Science University, Portland, OR 97239-4197, USA.
Rose
Anastasia
A
Gregory
Kate E
KE
Kelley
Mary J
MJ
Acott
Ted S
TS
D000818:Animals; D015153:Blotting, Western; D018929:Cell Culture Techniques; D005136:Eye Proteins / Q000235:genetics*; D015870:Gene Expression / Q000502:physiology*; D020411:Oligonucleotide Array Sequence Analysis; D012313:RNA / Q000302:isolation & purification; D012333:RNA, Messenger / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013314:Stress, Mechanical; D013552:Swine; D013997:Time Factors; D014129:Trabecular Meshwork / Q000166:cytology / Q000378:metabolism*; D015854:Up-Regulation
D005136:Eye Proteins; D012333:RNA, Messenger; D012313:RNA