Efectes de lFK506, un lligand dimmuofilines, sobre la regeneració nerviosa

Lobjectiu daquesta tesi era testar els efectes de lFK506 (o tacrolimus), un farmac immunosupressor selectiu que es lliga a les immunofilines, proteines citoplasmatiques molt ubiques. Els lligands dimmunofilines, la familia de farmacs a la qual pertany lFK506 (aixi com la Ciclosporina A i la Rapamicina), han demostrat tenir efectes neurotrofics i neuroprotectors molt prometedors a nivell experimental. Ens hem centrat en els probables efectes neurotrofics de lFK506 en la regeneracio del nervi periferic despres de lesions. S'han utilitzat dos models de lesio: 1. Lesio lleu, amb bona recuperacio funcional per se, sense necessitat de reparacio quirurgica: aixafament del nervi ciatic (crush) 2. Lesio severa, sense recuperacio funcional si no es repara quirurgicament: reseccio amplia del nervi ciatic i posterior reparacio (mitjancant un empelt dorigen autoleg o al.logenic, o mitjancant tubulitzacio tub de silicona, tub de col.lagen o tub de col.lagen amb cel.lules de Schwann al.logeniques al seu interior) Els resultats obtinguts en els diferents estudis mostren que ladministracio dFK506 accelera la taxa de regeneracio axonal despres de lesions del nervi periferic i millora el grau de reinnervacio assolit. Lestudi de dosi-resposta demostra dos pics de maxim efecte de lFK506 sobre la velocitat de regeneracio, a 0.2 i 5 mg/kg, si be la dosi de 5 mg permet assolir uns millors nivells de recuperacio funcional en seguiments llargs que la dosi de 0.2 mg/kg. No obstant, les dues dosis incrementen la reinnervacio dels organs diana i la regeneracio axonal en proporcions similars. En lesions severes per reseccio dun segment del nervi, on la reparacio quirurgica es determinant per lexit de la regeneracio, els efectes de ladministracio de lFK506 depenen del tipus de metode reparatiu utilitzat. Aixi, en les reseccions reparades mitjancant un autoempelt, on la regeneracio es bona per se, lFK506 nomes accelera lleugerament el dia dinici i el grau maxim de recuperacio assolit despres de 4 mesos. Quan sutilitza un empelt al.logenic, ladministracio continua duna dosi immunosupressora dFK506 permet evitar el rebuig i igualar leficacia daquests empelts amb els dorigen autoleg. Per altra banda, en les reseccions severes reparades mitjancant tubs de silicona, on la regeneracio es molt limitada, ladministracio dFK506 no permet incrementar el pobre percentatge dexit en la reinnervacio. Per contra, quan sutilitza un tub de col.lagen, un model intermig, els efectes de ladministracio de lFK506 son molt mes marcats i incrementen tant el percentatge dexit en la regeneracio com la velocitat i la recuperacio funcional final. En la reparacio per guies de col.lagen amb cel.lules de Schwann al seu interior, un model de protesi cel·lular que intenta remedar l'ambient que subministra un empelt nervios, ladministracio dFK506 garanteix lexit de la reinnervacio en tots els casos, si be el grau de recuperacio final assolit als 4 mesos es inferior a lobtingut amb la interposicio dautoempelts. The aim of this study is the evaluation of the effects of FK506 (tacrolimus), an immunosuppressant drug that binds to the immunophilins, a family of cytoplasmic proteins very spread in the organism. The main members of the immunophilin ligands family ara FK506, Ciclosporina A and rapamicin, and they have shown neurotrophic and neuroprotective effects besides its immunosuppressive action. In this thesis, we wanted to evaluate the neurotrophic effects of FK506 on peripheral nerve rengeration after nerve injury. We used two different models of inury in mice: 1. Severe Light lesion, with good recovery without surgical repair: sciatic nerve crush. 2. Severe lesion, that requires therapeutical repair to guarantee regeneration: resection of the sicaitic nerve and repair with the interposition of a graft (autologous or allogeneic), simple tubulization (silicone guide, collagen guide) or neural protheses, (collagen guides with Schwann cells inside) The results of our studies shown that administration of FK506 accelerates the regeneration rate after peripheral nerve lesions and improves the degree of recovery reached. The study shown that the dose-response effect of FK506 has a bimodal peak, with maximums at the dose of 0.2 and 5 mg/kg/day. However, the dose of 5 mg/Kg/day allows to reach better levels of functional recovery than the lower dose (0.2 mg/kg). Nevertheless, the two doses improve nerve regeneration and target organ reinnervation in similar degree. In more severe lesions (resection with a 6 mm gap of the sciatic nerve), the effects of FK506 depend on the kind of surgical repair used. In this way, FK506 slightly shortens the onset day of reinnervation and the maximum degree of regeneration after 4 months of follow-up in resections repaired with autografts, where regeneration is usually good. When resections were repaired with allografts, continuous administration of FK506 at an immunosuppressive dose get that this grafs we as effective as autografts are. However, supression of the treatment leads to an immune rejection and an important lost of the functional recovered, that improves poorly along time. On the other hand, treatment of FK506 after severe resections repaired with silicone tubes, where regeneration is limited, does not allow to increase the poor percentage of succesful in reinnervation. Against, when collagen guides are used, administration of FK506 increases the number of animals with distal reinnervation, speeds regeneration velocity and increases the level of recovery. If collagen guides were seeded with allogeneic Schwann cells, a neural protheses model that try to mimic the environment of the grafts, treatment with FK506 guarantees the succesful of reinnervation (100%) and the level of recovery. However, the results are poorer than that reached after graft repair.