When a peripheral nerve injury (PNI) occurs, the gold standard for tissue regeneration is the use of autografts. However, due to the secondary effects produced by multiple surgeries involved in the removal and implantation of autografts, for very small lesions, it is possible to replace them with the use of Nerve Guide Conduits (NGCs).
[1] However, NGCs are limited to short lesions (less than 1 cm).
[2] This limitation is caused by the absence of compounds present in the extracellular matrix (ECM) that can be provided by autografts. Since much of the regenerative process takes place on the NGC surface,
[2] our work aims to modify its surface using heparin and collagen coatings, two natural polymers present in the ECM. Heparin/collagen bilayers (HEP/COL) will increase biocompatibility, cell adhesion and migration, and allow the incorporation of neurotrophic factors such as Nerve Growth Factor (NGF). This research evaluates the effects on human Schwann cells (hSCs) when cultured on a commercial collagen NGC under four conditions: without coatings and with 6 heparin/collagen bilayers (HEP/COL)
6 with and without NGF supplemented to the culture medium (10 ng/ml). In our previous works,
[3,4] we have exhaustively characterized (HEP/COL)
6 coatings. The chemical structures of the polymers, the morphology, and the surface charge of the coatings could be determined. Real-time analysis of hSCs behavior showed 3 main phases: adhesion, proliferation, and adaptation. The adhesion phase was increased in the conditions with (HEP/COL)
6, together with the viability studies that showed an increase of up to 250% when compared to cells grown on polystyrene without coatings. The cells morphology has never been altered by (HEP/COL)
6, as well as the morphology of the coated NGC as shown in
Figure 1. Cell migration was favored and (HEP/COL)
6 also increased the expression of some proteins such as BDNF, which promotes the duration of the myelination process, or TNF alpha, which is a mediator of inflammatory and immune functions. In relation to the surface modification of a commercial NGC, these studies showed an increase of more than 200% in cell viability when compared to uncoated NGCs. We were also able to qualitatively determine (by colorimetry) the presence of heparin and to evidence the adhesion of cells on NGCs coated with (HEP/COL)
6.
In conclusion, (HEP/COL)
6 seems to be a promising strategy to improve the performance of NGCs.
Figure 1. SEM images of uncoated NGC (top) and (HEP/COL)6 coated NGC (bottom).
References:
[1] R. Ayala-caminero, L. Pinzón-herrera, C.A. Rivera Martinez, J. Almodovar, Polymeric scaffolds for three-dimensional culture of nerve cells: a model of peripheral nerve regeneration, MRS Commun. 7 (2017) 391–415. https://doi.org/10.1557/mrc.2017.90.
[2] J. Choi, J.H. Kim, J.W. Jang, H.J. Kim, S.H. Choi, S.W. Kwon, Decellularized sciatic nerve matrix as a biodegradable conduit for peripheral nerve regeneration, Neural Regen. Res. 13 (2018) 1796–1803. https://doi.org/10.4103/1673-5374.237126.
[3] L. Pinzon-Herrera, J. Mendez-Vega, A. Mulero-Russe, D.A. Castilla-Casadiego, J. Almodovar, Real-time monitoring of human Schwann cells on heparin-collagen coatings reveals enhanced adhesion and growth factor response, J. Mater. Chem. B. 8 (2020) 8809–8819. https://doi.org/10.1039/d0tb01454k.
[4] D.A. Castilla-Casadiego, L. Pinzon-Herrera, M. Perez-Perez, B.A. Quiñones-Colón, D. Suleiman, J. Almodovar, Simultaneous characterization of physical, chemical, and thermal properties of polymeric multilayers using infrared spectroscopic ellipsometry, Colloids Surfaces A. 553 (2018) 155–168. https://doi.org/10.1016/j.colsurfa.2018.05.052.
