Traumatic spinal cord injury (TSCI) can cause paralysis and permanent disability. Rehabilitation (RB) is currently the only accepted treatment, although its beneficial effect is limited. The development of biomaterials has provided therapeutic possibilities for TSCI, where our research group previously showed that the plasma-synthesized polypyrrole/iodine (PPy/I), a biopolymer with different physicochemical characteristics than those of the PPy synthesized by conventional methods, promotes recovery of motor function after TSCI. The present study evaluated if the plasma-synthesized PPy/I applied in combination with RB could increase its beneficial effects and the mechanisms involved. Adult rats with TSCI were divided into no treatment (control); biopolymer (PPy/I); mixed RB by swimming and enriched environment (SW/EE); and combined treatment (PPy/I + SW/EE) groups. Eight weeks after TSCI, the general health of the animals that received any of the treatments was better than the control animals. Functional recovery evaluated by two scales was better and was achieved in less time with the PPy/I + SW/EE combination. All treatments significantly increased βIII-tubulin (nerve plasticity) expression, but only PPy/I increased GAP-43 (nerve regeneration) and MBP (myelination) expression when were analyzed by immunohistochemistry. The expression of GFAP (glial scar) decreased in treated groups when determined by histochemistry, while morphometric analysis showed that tissue was better preserved when PPy/I and PPy/I + SW/EE were administered. The application of PPy/I + SW/EE, promotes the preservation of nervous tissue, and the expression of molecules related to plasticity as βIII-tubulin, reduces the glial scar, improves general health and allows the recovery of motor function after TSCI.
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This work was supported by the Instituto Mexicano del Seguro Social (IMSS) [FIS/IMSS/PROTG16/1603, 2016]; Stephanie Sánchez-Torres received a scholarship from CONACyT  and IMSS [029-2012]; Dr. Hermelinda Salgado-Ceballos thanks the IMSS Foundation for the grant of excellence granted.
The authors thank the technical support provided by the histotechnologist María del Carmen Baltazar Cortés.
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The authors declare no competing interests, confirm that there are no known conflicts of interest associated with this publication and there has been no significant financial support for this work that could have influenced its outcome.
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Sánchez-Torres, S., Díaz-Ruíz, A., Ríos, C. et al. Recovery of motor function after traumatic spinal cord injury by using plasma-synthesized polypyrrole/iodine application in combination with a mixed rehabilitation scheme. J Mater Sci: Mater Med 31, 58 (2020). https://doi.org/10.1007/s10856-020-06395-5