Abstract
Purpose :
The corneal wound healing effects of secreted factors (secretome) produced by bone marrow-derived human mesenchymal stem cells (MSCs) were evaluated as a function of their growth in 2D culture conditions and on 3D electrospun fiber scaffolds.
Methods :
Electrospun fiber scaffolds (0.7–1.0 µm diameter) composed of 1:1 polycaprolactone:gelatin were fabricated to provide a 3D microenvironment for MSCs and their mechanical properties were optimized to be similar to corneal tissue. The secretome produced by the MSCs cultured on fiber matrices versus 2D culture dishes were analyzed by Luminex immunoassay. In vitro proliferation and scratch-based wound healing assays were performed to compare the effects of the secretome on corneal fibroblast cells (CFCs) when delivered synchronously from co-cultured MSCs through a transwell co-culture system versus asynchronously after harvesting the factors separately and adding them to the media. Electrospun fibers seeded with MSCs were then applied to a rabbit corneal organ culture system. Corneas were fixed and stained for alpha smooth muscle actin (alpha-SMA), keratan sulfate (KS), and H&E and then analyzed by confocal microscopy.
Results :
The secretome of MSCs cultured on the 3D versus 2D substrates showed substantial compositional differences. Concentrations of factors such as HGF and ICAM-1 were increased over 5x in 3D cultures compared to 2D cultures. Metabolic activity of CFCs was sustained for 6 days when co-cultured with MSCs seeded on the fibers but decreased with time under other conditions. Scratch assays showed 95% closure at 48 hours when CFCs were co-cultured with MSCs seeded on fibers, while the control group only exhibited 50% closure at 48 hours. When applied to corneas in organ culture, MSCs seeded on fibers promoted faster epithelialization. Immunostaining showed that expression of alpha-SMA was lower in corneas treated with MSCs seeded on fibers, suggesting suppression of myofibroblastic change. KS expression was higher in corneas treated with MSCs seeded on fibers, suggesting that keratocytic phenotype was preserved.
Conclusions :
MSCs cultured on electrospun fibers facilitate wound healing in CFCs and on explanted corneas through differential secretome profiles compared to MSCs cultured on 2D substrates. Future work is merited to further understand the nature and basis of these differences and their effects in animal models.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.