Abstract
Purpose :
To investigate the function of secreted protein acidic and rich in cysteine (SPARC) in the maintenance of limbal stem cells (LSCs) physiological function.
Methods :
LSCs were treated with different concentration of exogenous SPARC (5μg/ml, 1μg/ml, 0.5μg/ml, 0.1μg/ml and 0μg/ml), the marker expression (p63,ABCG-2,Bmi-1,CK3/12), mitogenic effect and holoclone forming capacity of cultured LSCs were analyzed by immunofluorescent staining, PCR, CCK-8 test, EdU labeling and colony-forming efficiency test. To explore the mechanism of SPARC in the stemness preservation of LSCs, the phosphorylation of signal pathway p38-MAPK,ERK, JNK, STAT3 and PI3K was evaluated by western blot and immunofluorescent staining.
Results :
Immunofluorescent staining showed that exogenous SPACR increased the expression of LSCs specific markers such as p63,ABCG-2,Bmi-1 and decreased the expression of differentiation marker CK3/12 in a concentration - dependent manner. EdU assay demonstrated that SPARC stimulated LSCs proliferation,in the group of 5μg/ml and 1μg/ml over 12% p63-positive cells showed EdU-positive, and in 0μg/ml group only less than 4% p63-positive cells were labeled by EdU. Due to exogenous SPARC inhibited the adhesion of differentiated corneal epithelial cells, CCK-8 and CFE test showed a slight decline in 5μg/ml and 1μg/ml group, however the clone morphology in these 2 group was more uniform and regular. With 1μg/ml SPARC, the activation of phosphorylated p38-MAPK was observed by western blot and immunofluorescent staining. Signal pathway inhibitor of p38-MAPK further validated this result.
Conclusions :
SPARC mediate the stemness preservation of LSCs through the phosphorylation of p38-MAPK signal pathway.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.