Synergistic Enhancement of Peripheral Nerve Defect Repair using Peptide Functionalized Aligned Nanofiber Conduits

Peripheral nerve regeneration has moved through a variety of stages. Over the past few decades, new details
regarding the process of peripheral nerve regeneration have been elucidated. While the axonal regrowth process
has long been studied, it was noted recently that the regrowth and repair proceeds in tandem with Schwann cell
(SC) infiltration into the injured peripheral nerve defect. SC recruitment and directed migration has been a topic
of interest in our laboratories, with a focus on biased SC migration using topographical and ECM-mimicking
peptides. Our in vitro preliminary data shows a clear induction of directional SC migration using tethered
concentration gradients of both TGF-β peptide and YIGSR-peptide. Our in vivo preliminary data further
demonstrates that synthetic nanofibers support SC infiltration and maturation. Together, these data have
provided us with substantial motivation to further investigate mechanisms that mimic the neuroregenerative
process through the recruitment of SC. To pursue these goals, we have developed functional, degradable
polymers and versatile touch-spinning fabrication strategies to generate spatially-defined, bioactive, aligned
nanofiber conduits and we propose to use this platform to improve the regenerative capacity of injured peripheral
nerves. We believe that cell-free material solutions that enhance the endogenous repair process are
translationally-relevant and will provide the best options for translation of these functional conduits to the clinic
in the near term. We hypothesize that tethered, peptide-based bioactive factors in distinct concentration profiles,
in combination with topographical cues, will increase SC infiltration, and therefore, neuroregeneration, across
critical-sized gaps.
We will pursue this hypothesis with three independent aims. Specific Aim 1: Tethered laminin peptide gradients
to enhance neural cell migration and SC infiltration. We will investigate how concentration gradients of tethered
laminin peptide enhance neurite and SC response, singly and in an explant (multicellular) model. The outcome
of this Aim will yield an optimal nanofiber (diameter, laminin-peptide gradient) to advance to our proposed in vivo
studies in Aim 3. Specific Aim 2: Tethered TGF-β peptide gradients to enhance neural cell migration and SC
infiltration. We will investigate how concentration gradients of tethered TGF-β peptide-based growth factor in
combination with RGD enhance neurite and SC response, singly and in an explant (multicellular) model. The
outcome of this Aim will yield an optimal nanofiber (diameter, TGF-β peptide gradient) to advance to our
proposed in vivo studies in Specific Aim 3. Specific Aim 3: In vivo neural regeneration outcomes improve with
combinations of laminin peptide gradients and TGF-β gradients. We will use the best nanofiber scaffolds
independently identified in Aims 1 and 2 to investigate whether combinations of laminin peptide and TGF-β
peptide concentration gradients will synergistically enhance the initial process of neural regeneration and long-
term functional recovery in vivo in a well-established rat sciatic nerve defect model. With a focus on the early
steps in endogenous repair, along with a long-term recovery metric, this work will provide foundational evidence
in the role that SC play in the nerve regeneration processes. This knowledge will shift our focus in nerve repair
from the axon to cells that are known to support the regeneration process to enhance recovery.

Grant Number: 5R01NS124889-04
NIH Institute/Center: NIH
Principal Investigator: Matthew Becker