Gene expression and locomotor recovery in adult rats with spinal cord injury and plasma-synthesized polypyrrole/iodine application combined with a mixed rehabilitation scheme.

Introduction: Spinal cord injury (SCI) can cause paralysis, for which effective therapeutic strategies have not been developed yet. The only accepted strategy for patients is rehabilitation (RB), although this does not allow complete recovery of lost functions, which makes it necessary to combine it with strategies such as plasma-synthesized polypyrrole/iodine (PPy/I), a biopolymer with different physicochemical properties than PPy synthesized by conventional methods. After SCI in rats, PPy/I promotes functional recovery. Therefore, the purpose of this study was to increase the beneficial effects of both strategies and identify which genes activate PPy/I when applied alone or in combination with a mixed scheme of RB by swimming and enriched environment (SW/EE) in rats with SCI. Methods: Microarray analysis was performed to identify mechanisms of action underlying the effects of PPy/I and PPy/I+SW/EE on motor function recovery as evaluated by the BBB scale. Results: Results showed robust upregulation by PPy/I in genes related to the developmental process, biogenesis, synapse, and synaptic vesicle trafficking. In addition, PPy/I+SW/EE increased the expression of genes related to proliferation, biogenesis, cell development, morphogenesis, cell differentiation, neurogenesis, neuron development, and synapse formation processes. Immunofluorescence analysis showed the expression of ß-III tubulin in all groups, a decreased expression of caspase-3 in the PPy/I group and GFAP in the PPy/I+SW/EE group (p < 0.05). Better preservation of nerve tissue was observed in PPy/I and PPy/SW/EE groups (p < 0.05). In the BBB scale, the control group scored 1.72 ± 0.41, animals with PPy/I treatment scored 4.23 ± 0.33, and those with PPy/I+SW/EE scored 9.13 ± 0.43 1 month after follow-up. Conclusion: Thus, PPy/I+SW/EE could represent a therapeutic alternative for motor function recovery after SCI.

Evolution of Spinal Cord Transection of Rhesus Monkey Implanted with Polymer Synthesized by Plasma Evaluated by Diffusion Tensor Imaging.

In spinal cord injury (SCI) there is damage to the nervous tissue, due to the initial damage and pathophysiological processes that are triggered subsequently. There is no effective therapeutic strategy for motor functional recovery derived from the injury. Several studies have demonstrated neurons growth in cell cultures on polymers synthesized by plasma derived from pyrrole, and the increased recovery of motor function in rats by implanting the polymer in acute states of the SCI in contusion and transection models. In the process of transferring these advances towards humans it is recommended to test in mayor species, such as nonhuman primates, prioritizing the use of non-invasive techniques to evaluate the injury progression with the applied treatments. This work shows the ability of diffusion tensor imaging (DTI) to evaluate the evolution of the SCI in nonhuman primates through the fraction of anisotropy (FA) analysis and the diffusion tensor tractography (DTT) calculus. The injury progression was analysed up to 3 months after the injury day by FA and DTT. The FA recovery and the DTT re-stabilization were observed in the experimental implanted subject with the polymer, in contrast with the non-implanted subject. The parameters derived from DTI are concordant with the histology and the motor functional behaviour.

Effect of the combined treatment of albumin with plasma synthesised pyrrole polymers on motor recovery after traumatic spinal cord injury in rats.

Traumatic spinal cord injury (TSCI) is a health problem for which there is currently no treatment or definitive therapy. Medicine has explored therapeutic options for patients with TSCI with the aim to improve their quality of life. One alternative has been the development of biomaterials that offer neuroprotection or neuroregeneration of damaged nerve tissue. The microinjection of iodine-doped polypyrrole particles synthesised by plasma (PPPy/I) has shown neuroprotective effects that favour motor function recovery in experimental animals with TSCI. However, their ability to migrate into the tissue has led to the need to test a suspension vehicle that enables the concentration of particles at the site of injury. To achieve this, two biomaterials of PPPy/I (P1 and P2) were studied. The superficial physicochemical characterisation of the polymers was performed by infrared spectroscopy, X-ray photoelectron spectroscopy and contact angle. The rheological performance under oscillatory shear rate of suspensions containing both polymers alone and in combination with bovine serum albumin was also studied. In vivo tests were performed on animals with and without TSCI that were microinjected with particles of P1 or P2 in suspension using a solution of rat serum albumin. Exposure to the protein solutions generates a protein multilayer on the surface of the biomaterials that can drastically change the behaviour of both P1 and P2, which led to severe repercussions in the in vivo assays. The results showed that surface chemistry plays an important role in the performance and that it is possible to treat TSCI with these materials. The interaction of the surface of materials PPPy/I.1 (P1) and PPPy/I.2 (P2) with bovine serum albumin (BSA) resulted in a series of changes in the surface chemistry of both biomaterials. The contact angle study (Fig. A) showed the presence of a critical BSA concentration ([BSA]c), in which a monolayer was formed on both polymers and then a stable protein multilayer, as evidenced by the establishment of a plateau in the determination of the contact angle. In vivo tests showed that this interaction may be beneficial in the treatment of traumatic spinal cord injury (TSCI), depending on the surface characteristics with or without rat serum albumin (RSA). The TSCI + P1 and TSCI + P2 + RSA groups obtained significant differences in functional recovery compared with the control group according to the Basso, Beattie and Bresnahan scale (BBB).

Functional recovery in spinal cord injured rats using polypyrrole/iodine implants and treadmill training.

Currently, there is no universally accepted treatment for traumatic spinal cord injury (TSCI), a pathology that can cause paraplegia or quadriplegia. Due to the complexity of TSCI, more than one therapeutic strategy may be necessary to regain lost functions. Therefore, the present study proposes the use of implants of mesoparticles (MPs) of polypyrrole/iodine (PPy/I) synthesized by plasma for neuroprotection promotion and functional recovery in combination with treadmill training (TT) for neuroplasticity promotion and maintenance of muscle tone. PPy/I films were synthesized by plasma and pulverized to obtain MPs. Rats with a TSCI produced by the NYU impactor were divided into four groups: Vehicle (saline solution); MPs (PPy/I implant); Vehicle-TT (saline solution + TT); and MPs-TT (PPy/I implant + TT). The vehicle or MPs (30 µL) were injected into the lesion site 48 h after a TSCI. Four days later, TT was carried out 5 days a week for 2 months. Functional recovery was evaluated weekly using the BBB motor scale for 9 weeks and tissue protection using histological and morphometric analysis thereafter. Although the MPs of PPy/I increased nerve tissue preservation (P = 0.03) and promoted functional recovery (P = 0.015), combination with TT did not produce better neuroprotection, but significantly improved functional results (P = 0.000) when comparing with the vehicle group. So, use these therapeutic strategies by separately could stimulate specific mechanisms of neuroprotection and neuroregeneration, but when using together they could mainly potentiate different mechanisms of neuronal plasticity in the preserved spinal cord tissue after a TSCI and produce a significant functional recovery. The implant of mesoparticles of polypyrrole/iodine into the injured spinal cord displayed good integration into the nervous tissue without a response of rejection, as well as an increased in the amount of preserved tissue and a better functional recovery than the group without transplant after a traumatic spinal cord injury by contusion in rats. The relevance of the present results is that polypyrrole/iodine implants were synthesized by plasma instead by conventional chemical or electrochemical methods. Synthesis by plasma modifies physicochemical properties of polypyrrole/iodine implants, which can be responsible of the histological response and functional results. Furthermore, no additional molecules or trophic factors or cells were added to the implant for obtain such results. Even more, when the implant was used together with physical rehabilitation, better functional recovery was obtained than that observed when these strategies were used by separately.

Plasma polypyrrole implants recover motor function in rats after spinal cord transection.

We studied the use of three biocompatible materials obtained by plasma polymerization of pyrrole (PPy), pyrrole doped with iodine (PPy/I) and a copolymer formed with pyrrole and polyethylene glycol (PPy/PEG), implanted, separately, after a complete spinal cord transection in rats. Motor function assessed with the BBB scale and somatosensory evoked potentials (SEPs) in the implanted rats were studied. Results showed that the highest motor recovery was obtained in rats with PPy/I implants. They also showed a significant reduction in the latency of SEPs. Histological analyses showed no signs of implant rejection; on the contrary, implants based on PPy improved the SEPs conduction and motor function after lesion.

Tissue spinal cord response in rats after implants of polypyrrole and polyethylene glycol obtained by plasma.

Most of the biomaterials used nowadays for the reconstruction of the spinal cord (SC) tissue after an injury, tested in animals, have obtained modest results. This work presents a study about the compatibility of two novel, non-biodegradable, semi-conductive materials, obtained by plasma polymerization: iodine-doped pyrrole (PPy/I) and pyrrole-polyethylene glycol (PPy/PEG). Both polymers, separately, were implanted in the SC tissue of rats after a transection. Prior to implantation, the elemental composition and the physico-chemical properties of polymers were studied by electron scanning microscopy, IR Spectroscopy and thermogravimetric analysis. We used adult female Long Evans rats, subjected to SC transection. Animals were randomized to be allocated in one of the treatment groups and were killed four weeks after the lesion for histology study. Results showed that both implants were integrated to the SC tissue, as inflammatory and gliotic responses, similar to those observed in the control group, and rejection of the implant, were not evident. Moreover, the immediate effect of PPy/I or PPy/PEG in the injured SC prevented secondary tissue destruction, as compared to non-implanted control animals. In conclusion, implants of semi-conductive polymers were well-tolerated and integrated favorably to SC tissue after transection.