Polyurethane/Gelatin Nanofibrils Neural Guidance Conduit Containing Platelet-Rich Plasma and Melatonin for Transplantation of Schwann Cells

Abstract

The current study aimed to enhance the efficacy of peripheral nerve regeneration using a biodegradable porous neural guidance conduit as a carrier to transplant allogeneic Schwann cells (SCs). The conduit was prepared from polyurethane (PU) and gelatin nanofibrils (GNFs) using thermally induced phase separation technique and filled with melatonin (MLT) and platelet-rich plasma (PRP). The prepared conduit had the porosity of 87.17 ± 1.89%, the contact angle of 78.17 ± 5.30° and the ultimate tensile strength and Young's modulus of 5.40 ± 0.98 MPa and 3.13 ± 0.65 GPa, respectively. The conduit lost about 14% of its weight after 60 days in distilled water. The produced conduit enhanced the proliferation of SCs demonstrated by a tetrazolium salt-based assay. For functional analysis, the conduit was seeded with 1.50 × 10⁴ SCs (PU/GNFs/PRP/MLT/SCs) and implanted into a 10-mm sciatic nerve defect of Wistar rat. Three control groups were used: (1) PU/GNFs/SCs, (2) PU/GNFs/PRP/SCs, and (3) Autograft. The results of sciatic functional index, hot plate latency, compound muscle action potential amplitude and latency, weight-loss percentage of wet gastrocnemius muscle and histopathological examination using hematoxylin-eosin and Luxol fast blue staining, demonstrated that using the PU/GNFs/PRP/MLT conduit to transplant SCs to the sciatic nerve defect resulted in a higher regenerative outcome than the PU/GNFs and PU/GNFs/PRP conduits.

Keywords: Gelatin; Melatonin; Neural guidance conduit; Platelet-rich plasma; Polyurethane; Schwann cells.

Fig. 1

Characterization of the neural guidance conduits. a Representative SEM micrograph of the electrospun gelatin nanofibrils. The histogram is the diameter distribution from the corresponding SEM image, b representative SEM micrograph of the PU/GNFs conduit, c histogram comparing the weight-loss percentages of the conduits in distilled water after 30 and 60 days, and d the effect of conduits on the proliferation of SCs evaluated by MTT assay. Values represent the mean ± SD, n = 3, *P < 0.05, **P < 0.01 (obtained by Student’s t test)

Fig. 2

a SEM-micrograph (pseudo-colored) of a SC on the PU/GNFs/PRP/MLT conduit exhibiting elongation and establishment of connections to the conduit and b surgical implantation of the prepared conduit in a 10-mm sciatic nerve defect in rat

Fig. 3

Functional analysis results 12 weeks post surgery. a Histogram comparing the sciatic functional index (SFI), b histogram comparing the hot plate latency results, c electromyographic results (compound muscle action potential (CMAP) amplitudes and latencies), and d histogram comparing the gastrocnemius muscle wet weight-loss percentages. Values represent the mean ± SD, n = 3, *P < 0.05, **P < 0.01, ***P < 0.005 (obtained by Student’s t test)

Fig. 4

Histological analysis of the hematoxylin–eosin stained sciatic nerve cross sections at the end of 12th week post-surgery. a PU/GNFs/SCs, b PU/GNFs/PRP/SCs, c PU/GNFs/PRP/MLT/SCs and d Autograft. B blood vessel, V vacuolar degeneration, L lamellar space, S Schwann cell. Scale bar 500 µm and ×100 magnification

Fig. 5

Histological analysis of Luxol fast blue stained sciatic nerve cross sections at the end of 12th week post-surgery. a PU/GNFs/SCs, b PU/GNFs/PRP/SCs, c PU/GNFs/PRP/MLT/SCs and d Autograft. Scale bar 500 µm and ×100 magnification