Dissertation committee:
Παναγιώτης Παπαγγελόπουλος, Καθηγητής, Ιατρική Σχολή, ΕΚΠΑ
Elizabeth Johnson, Καθηγήτρια, Ιατρική Σχολή, European University of Cyprus
Ανδρέας Μαυρογένης, Καθηγητής, Ιατρική Σχολή, ΕΚΠΑ
Ευστάθιος Χρονόπουλος, Καθηγητής, Ιατρική Σχολή, ΕΚΠΑ
Γεώργιος Αγρογιάννης, Αναπληρωτής Καθηγητής, Ιατρική Σχολή, ΕΚΠΑ
Βασίλειος Κοντογεωργάκος, Αναπληρωτής Καθηγητής, Ιατρική Σχολή, ΕΚΠΑ
Δημήτριος Κούλαλης, Επίκουρος Καθηγητής, Ιατρική Σχολή, ΕΚΠΑ
Summary:
Aim: Nerve injuries with a gap represent a clinical challenge without a clear solution. Despite substantial improvement in microsurgical techniques for nerve repair, recovery after peripheral nerve injury usually remains incomplete. Tacrolimus (FK506), an FDA approved immunosuppressant, has been found to improve reinnervation and functional recovery following peripheral nerve injury in animal models. However, systemically delivered FK506 causes undesired immunosuppression. Aim of this study was to assess the efficacy of local FK506 delivery by means of a biodegradable fibrin gel conduit to improve outcomes in the setting of a rat sciatic nerve transection model.
Methods: 40 Wistar rats were procured and equally distributed in 4 groups (A to D). After surgical preparation, in group A (SHAM), the left sciatic nerve was exposed through a gluteal incision and then the surgical wound was closed in layers without any further intervention. In group B (AUTO), the sciatic nerve was exposed, and a 10-mm section was transected. This nerve section was reversed in orientation and re-implanted in lieu of an autograft. In groups C (SLN) and D (FK506), the sciatic nerve was transected so as to create a 10-mm nerve gap. A fibrin conduit was prepared using a two-compound fibrin glue (Tisseel®). Fibrin glue was dispensed in a silicone mould around a stainless-steel core and pressed into shape for a few minutes. In group C, the fibrin conduit was mixed with normal saline, whereas in group D, the fibrin glue conduit was mixed with FK506. The conduits were subsequently used to bridge the nerve gap by being fixed to the nerve ends by 1-2 single epineurial sutures. Finally, surgical wounds were copiously irrigated and closed in layers in a regular fashion. Nerve regeneration was evaluated at 12 weeks following surgery by means of walking track analysis, electromyography and neurohistomorphometry. The resulting data was used for statistical analysis.
Results: After completion of the aforementioned tests, retrieved results underwent statistical analysis. Descriptive statistics was used to express results as means standard deviations. Appropriate statistical tests were then used to identify differences between group means. Statistical analysis was conducted with the software GraphPad Prism 9.0 (GraphPad Software, Inc., La Jolla, California, USA). Walking track analysis performed preoperatively, at 4, 8 and 12 weeks after surgery, demonstrated a gradual improvement in SFI (sciatic functional index). Preoperatively, values remained in normal-subnormal levels, as expected. In group A, as there was no nerve injury inflicted at any time, SFI values remained similar to preoperative values throughout the experiment. Group A values were also statistically better than all other groups at any time postoperatively. In all other groups, SFI was reduced significantly postoperatively, becoming strongly negative, prior to start recovering, fact indicative of the procured nerve injury and subsequent loss of function. The SFI increased over time after nerve injury within all groups. At 12 weeks, group D presented more favorable values to group C, difference found to be statistically significant. During electromyography, action potentials were demonstrated in all groups. The mean latency, amplitude and CMAP recovery index were measured at 12 weeks postoperatively. Group Α (sham) had the shortest latency, whereas group C (conduit alone) had the longest. Group D had more favorable values compared to group C but inferior as compared to group B. Group D demonstrated significantly better mean amplitude as compared to group C. Group D also demonstrated a significantly better CMAP recovery index than group C. Morphometric analysis was performed in sections from the distal nerve stump. The parameters measures included myelinated axon number and nerve fiber diameter. Significant differences between the nerve areas were found in the distal nerve portion, with groups B and D performing significantly better than group C. Group B also outperformed group D, even though statistical difference was weaker.
Conclusion: The use of fibrin gel conduit loaded with FK506 has had more favorable outcomes and faster functional recovery compared with a conduit without additives. The current study suggests that local delivery of FK506 with a biodegradable conduit can be effectively used to enhance peripheral nerve regeneration.
Keywords:
Nerve injury, Nerve regeneration, FK506, Tacrolimus, Nerve conduits
