Bioactive Self-Assembling Peptide Hydrogels Functionalized with Brain-Derived Neurotrophic Factor and Nerve Growth Factor Mimicking Peptides Synergistically Promote Peripheral Nerve Regeneration

Abstract

Various artificial materials have been fabricated as alternatives to autologous nerve grafts in peripheral nerve regeneration, and these afford positive recovery effects without the disadvantages of the gold standard. In this study, we prepared a three-dimensional functionalized self-assembling peptide nanofiber hydrogel containing two neurotrophic peptides (CTDIKGKCTGACDGKQC and RGIDKRHWNSQ derived from nerve growth factor and brain-derived neurotrophic factor, respectively) that reflected the structure and properties of the neural extracellular matrix. The material was used to promote axonal regrowth and functional recovery. Scanning electron microscopy revealed a three-dimensional porous matrix within the hydrogel. Circular dichroism spectroscopy and atomic force microscopy confirmed that the peptides displayed a β-sheet structure and self-assembled into long nanofibers. Rheology measurements and atomic force microscopy indicated that the elasticity of the peptide hydrogels was close to that of the nerve tissue matrix. In vitro work with Schwann cells and dorsal root ganglia showed that the hydrogels exhibited good cell compatibility. Furthermore, the hydrogel containing CTDIKGKCTGACDGKQC and RGIDKRHWNSQ promoted the neurite outgrowth of PC12 cells significantly compared to non-functionalized peptide. In vivo, the hydrogels were placed into chitosan tubes and used to bridge 10 mm long sciatic nerve defects in rats. We found that the combination of CTDIKGKCTGACDGKQC and RGIDKRHWNSQ accelerated axonal regeneration and afforded good functional recovery, suggesting that they synergistically facilitate peripheral nerve regeneration.

Self-assembling peptide hydrogels functionalized with LN- and BDNF- mimicking epitopes synergistically enhance peripheral nerve regeneration

“…Additionally, the chitosan degradation products could facilitate peripheral nerve regeneration by improving macrophage-constructed microenvironments 42 . The chitosan tube in this study has been verified to be helpful for peripheral nerve regeneration in previous studies 11 , 13 , 36 , 37 . Therefore, the chitosan tube was used as guidance conduit in this study.…”

“…The solution of RAD/IKV/RGI was acquired by mixing 50% RAD/IKV solution and 50% RAD/RGI solution. The self-assembling peptide hydrogels were fabricated within cell-culture Transwell inserts (10-mm diameter; Millipore, Billerica, MA, USA), as described previously 37 . Briefly, sterilized inserts were placed in a 24-well culture plate with 400 μL of Dulbecco's Modified Eagle Medium (DMEM, Gibco, Life Technologies, Carlsbad, CA, USA) in each well.…”

“…The previous study proposed an SAP nanofiber hydrogel functionalized with BDNF mimicking peptide RGI to improve axon regeneration and motor functional recovery; however, its regenerative effect was not as good as that of autografting, indicating a limitation in the use of a single factor in repairing nerve injury 36 . Other studies showed that combined use of RGI and other peptide motifs derived from growth factors, such as NGF and VEGF, promoted nerve regeneration 13 , 37 . Therefore, we expanded our previous efforts to establish synergetic scaffolds harboring LN and BDNF mimicking peptide motifs to simulate effects of the extracellular matrix and neurotrophic factors at the same time for evaluation in a rat model of sciatic nerve injury.…”

“…Moreover, BDNF concentration directly influences axonal regeneration, with low exogenous BDNF doses enhancing motor neuron axon regeneration, whereas high levels inhibiting regeneration 35 . To address this issue, we previously reported that a neurotrophic peptide sequence RGIDKRHWNSQ (RGI) derived from BDNF promoted rat sciatic nerve regeneration 36 , 37 . The BDNF-mimetic peptide motif designed based on solvent-exposed loops 3 and 4 of BDNF simulated neurite outgrowth and survival by binding to the TrkB and p75 neurotrophin receptor 38 .…”

Sequence‐Optimized Peptide Nanofibers as Growth Stimulators for Regeneration of Peripheral Neurons

“…Certain PNFs revealed high biocompatibility and did not promote tissue inflammation 1a. Further functionalities have been attached either to the peptide sequences before assembly or to the already formed fibers, including epitopes of extracellular matrix proteins such as laminin or fibronectin, polydopamine, glycosaminoglycans, or growth factors including BDNF . These biomimetic SAPs increased focal adhesion assembly, which is attractive for processes such as axonal regeneration .…”