Abstract
Purpose: :
To use in vitro assays to examine the biological consequences of co-exposure of two potential therapeutic candidates of interest for the treatment of retinal degenerative diseases, namely, multipotent RPCs and sterilized GDNF-containing PLGA microparticles.
Methods: :
Human RPCs were grown under standard proliferation conditions and treatment groups co-cultured with 0.5mg/ml GDNF microparticles, equivalent to 10ng/ml of GDNF, for 48 hours. The microparticles were seeded either directly into RPC cultures, or into cell culture inserts which were then placed into the cultures. Microparticles and cell morphology were monitored by IncuCyte live cell imaging system, cell viability was assessed via Cell Counting Kit-8, apoptosis was measured via caspase-3 detection, and phenotype assessed via a gene expression profile including progenitor and lineage markers that was quantified using real-time PCR (ABI 7500 fast).
Results: :
hRPCs proliferated to confluence over the 48 h test period under all conditions. In direct contact cultures, the microparticles displayed a tendency to aggregate during the initial 12 h period. Cell viability and apoptosis were unaffected by the presence of microparticles at estimated therapeutic concentrations. Gene expression was unaffected without direct contact. Contact resulted in detectable changes, particularly up-regulation of p16 and p21 cyclin-dependent kinase inhibitors, as well as CRALBP and class I and II MHC antigens.
Conclusions: :
GDNF microparticles have little detectable influence on hRPCs when separated by a permeable barrier, however, direct contact does induce moderate changes in gene expression most suggestive of down-regulation of the cell cycle with an increased propensity towards differentiation, similar to what we previously reported with murine RPCs grown directly on PLGA scaffolds. The potential for increased MHC expression should also be considered in the context of transplantation.
Keywords: retinal degenerations: cell biology • retina • transplantation