Abstract
Purpose:
Retinal ischemia-reperfusion (I/R) injury in the eye cause neurodegeneration and capillary degeneration associated with inflammation and apoptosis. Previously we have shown that adipose stromal cells (ASC) rescue from I/R injury within 7 days post transplantation. In this study, we hypothesized that attenuation of p38 MAPK, a stress kinase, by ASC conditioned media (ASC-CM) may play a role in the observed beneficial effect.
Methods:
Human ASC were cultured to confluence in serum free conditioned media for 72h and cell free supernatant was collected. Basal essential media (BEM) prepared in similar fashion without cells served as control. Unilateral retinal I/R were done in adult Lewis rats by transiently elevating the intraocular pressure for 1h. Uninjured eyes served as I/R controls. After day 7 of reperfusion the animals were randomized to receive intravitreal ASC-CM (2μL) or BME. After further 6-7 days, retinal function was assessed by Electroretinogram (ERG), retinal structure and thickness was assessed by optical coherence tomography (OCT) and the retinal extracts were processed by Western blot. Human retinal endothelial cells (HREC) exposed to TNF-α were incubated with varying dose of ASC-CM or BEM for 72hr and processed for p38 MAPK by Western blot.
Results:
Retinal I/R resulted in a significant reduction in “b” wave amplitude (as measured by electroretinogram) compared to anesthetized live un-injured control rats, and this I/R induced reduction was significantly improved by ASC-CM at day-6 post injection (p<0.05). Subsequently, ASC-CM injection rescued the retinal ganglion cells layer and whole retinal thickness assessed by OCT. Finally, retinal whole extracts from injured eyes that received ASC-CM demonstrated a significant reduction in phosphorylated p38 MAPK compared to the injured eyes that received BEM. Cultured HREC exposed to TNF-α that received ASC-CM demonstrated a decreased level of phosphorylated p38 MAPK compared to the cells that received BEM.
Conclusions:
Our findings suggest that ASC-CM not only rescue retinal ganglion cells but also improved the function of retina. Although more studies warranted, attenuation of p38 stress MAPK pathway seems to play a major role in the observed beneficial effect.
Keywords: 688 retina •
499 diabetic retinopathy •
721 stem cells