Migration of Human Retinal Progenitor Cells in 3D Collagen Gels

Migration
of Human Retinal Progenitor Cells in 3D Collagen Gels

Joydip Kundu^1,2, Douglas Blanton¹,
Petr Baranov², Madeleine J Oudin³, Michael J. Young²,

Miles A. Miller⁴, Douglas A Lauffenburger⁴,
Rebecca L. Carrier¹

¹Chemical Engineering, Northeastern University,
Boston, MA 02115

²Schepens Eye Research Institute, an affiliate of
Harvard Medical School, Boston, MA 02114

³David Koch Institute for Integrative Cancer Research,
Massachusetts Institute of Technology, Cambridge, MA 02115

⁴Bioengineering Department, Massachusetts Institute
of Technology, Cambridge, MA 02115

Abstract

Introduction: Retinal degeneration is the leading cause of blindness
worldwide. It is currently estimated that 25 to 30 million people worldwide
suffer from age-related macular degeneration, with no known cure available to date.
Subretinal implantation of retinal progenitor cells has shown great promise in
models of retinal degeneration for restoration of vision, but is limited by
extremely low integration (<2%) into the retina. Understanding the cues
required to promote cell behaviors essential to successful integration (e.g.,
migration) will enable rational design of cell delivery vehicles to enhance
integration within host retina following transplantation. Objective: Investigate the impact of
matrix stiffness and soluble cues (varied growth factor concentrations) on
human retinal progenitor cells (hRPCs) migration. Methodology: In this study, the migration of hRPCs within
thermo-responsive collagen gels of varying concentrations (3mg/ml, 2mg/ml and
1mg/ml) was analyzed using a high-throughput 3D migration assay. The storage
moduli (stiffness) of the collagen gels (3mg/ml, 2mg/ml and 1mg/ml) were
determined using a rheometer. The impact of addition of growth factors known to
be significant in retinal development, retinal regeneration in non-mammals, and
neuronal cell migration: epidermal growth factor (EGF) and fibroblastic growth factor
(FGF), was studied using hRPCs in 2mg/ml collagen gels. Results: The mean migration distances of the encapsulated hRPCs
within gels after 48 hours were 39±3μm (3mg/ml collagen), 46±3μm
(2mg/ml collagen) and 45±5μm (1mg/ml collagen). The storage modulus
(measured at 10% strain) of 3mg/ml collagen gels (1.29 Pa) was 2-fold higher than
that of 2mg/ml (0.64 Pa) and 1mg/ml (0.50 Pa) collagen gels. The gel stiffness
did not have a significant impact on the migration of the retinal progenitors. The
addition of EGF and FGF (at concentrations 10ng/ml and 100ng/ml) in 2mg/ml
collagen gel increased hRPC migration by 2.2-2.3 fold compared to media alone. Cells
exposed to 100ng/ml of EGF and FGF showed 1.5-1.6 fold increased migration
compared to those treated with 10ng/ml of these cytokines. The impact of
cytokines on cell signaling events in hRPCs is being explored using multiplex
cytokine analysis to elucidate the signaling pathways critical for hRPC migration.
Conclusion: These results motivate
further exploration of the impact of soluble cues in the context of different hydrogels,
representative of either the retinal microenvironment or potential cell
delivery vehicles, on hRPC migration to inform rational design of delivery
vehicles enabling successful cell transplantation to treat retinal
degeneration.

Acknowledgements: This study was
supported by Northeastern University (Tier 1 Provost Grant) and NIH Grant
1R21EY021312 (NEI).