Platelet-Rich Fibrin Membrane Nerve Guidance Conduit for Peripheral Nerve Injuries

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Platelet-Rich Fibrin Membrane Nerve Guidance Conduit: A Potentially Promising Method for Peripheral Nerve Injuries

Peripheral nerve injuries often result in partial or complete transection of nerves, leading to paralysis, sensory abnormalities, and neuropathic pain. Current clinical interventions, such as autologous nerve grafting (ANG), remain the gold standard but face limitations like donor site morbidity and limited availability. Alternative approaches, including synthetic nerve conduits, have shown variable efficacy. This study introduces a novel platelet-rich fibrin membrane nerve guidance conduit (PRF-NGC) and evaluates its potential for peripheral nerve repair. By comparing PRF-NGC with ANG and polyurethane (PUR) conduits in a murine model, the research provides comprehensive insights into the structural, functional, and biological advantages of PRF-based solutions.

Preparation and Characterization of PRF Membrane Conduits

PRF, a second-generation platelet concentrate, was prepared from 5 mL of rat blood collected into glass-coated tubes without anticoagulants. Centrifugation at 400×g for 10 minutes yielded fibrin clots in the middle layer, which were compressed into membranes using a PRF box. The membranes were trimmed into 7 mm × 3 mm sections and wrapped around 25-gauge syringe needles to form tubular conduits. The edges were sutured with 11-0 microsurgical sutures. Scanning electron microscopy (SEM) revealed a porous fibrin matrix on the PRF membrane surface and cross-sections, critical for nutrient diffusion and cellular interactions (Figure 1A). The final conduit structure demonstrated flexibility and ease of handling (Figure 1B).

In vitro degradation assays showed PRF membranes retained structural integrity for over three months. However, in vivo biodegradation occurred within 2–3 weeks, aligning with the critical period for early nerve regeneration. This balance between temporary structural support and timely degradation minimizes long-term foreign body reactions.

Experimental Design and Surgical Procedures

A total of 24 nude mice were randomized into three groups: ANG, PRF-NGC, and PUR conduit (n = 8 per group). A 5-mm sciatic nerve defect was created in all animals. In the ANG group, the resected nerve segment was rotated 180° and sutured with 11-0 sutures. For the PRF and PUR groups, nerve stumps were inserted 1 mm into the conduit ends and secured with sutures. Matrigel was injected into both conduit types to enhance cellular adhesion and growth factor retention.

Postoperative observations at 12 weeks revealed smooth-surfaced regenerated tissues in the PRF group, with no infections, neuromas, or adhesions (Figure 1C). This confirmed the biocompatibility of PRF-NGC, a critical advantage over synthetic alternatives.

Vascular Regeneration and Angiogenesis

Immunofluorescence staining using anti-smooth muscle actin (SMA) antibodies demonstrated extensive vascular networks within and around PRF-NGC-regenerated nerves (Figure 1D). Longitudinal vessels aligned with the nerve’s proximal-distal axis, while transverse sections revealed smaller-diameter capillaries, indicating robust angiogenesis. This vascularization likely facilitated nutrient delivery and Schwann cell migration, both essential for axonal regeneration.

Morphometric Analysis of Nerve Regeneration

Transmission electron microscopy (TEM) and morphometric analyses provided quantitative comparisons of myelinated nerve fibers across groups. Key findings included:

  1. Myelinated Fiber Count: The PRF group (1,892 ± 214 fibers) significantly outperformed the PUR group (1,102 ± 187 fibers; P < 0.0001) but remained inferior to ANG (2,305 ± 198 fibers; P = 0.0013).
  2. Myelin Thickness: ANG showed the thickest myelin sheaths (0.88 ± 0.25 µm), followed by PRF (0.63 ± 0.20 µm) and PUR (0.32 ± 0.14 µm). Differences between PRF and both ANG (P = 0.0129) and PUR (P = 0.0038) were statistically significant.
  3. Fiber Diameter: PRF (4.12 ± 1.05 µm) and ANG (4.45 ± 0.98 µm) exhibited comparable diameters, both significantly larger than PUR (2.87 ± 0.76 µm; P = 0.0052 for PRF vs. PUR).

These results suggest PRF-NGC supports axonal maturation and myelination at levels approaching ANG, while far exceeding PUR conduits (Figures 1E–G).

Functional Recovery and Muscle Atrophy Prevention

Functional recovery was assessed via gastrocnemius muscle wet weight ratios and Masson’s trichrome staining. The PRF group’s muscle wet weight ratio (82.4 ± 6.1%) matched ANG (85.2 ± 5.8%) and exceeded PUR (62.3 ± 7.4%). Histological staining revealed minimal collagen deposition (blue staining) in PRF and ANG groups, indicating reduced muscle atrophy compared to PUR. This highlights PRF-NGC’s ability to preserve target muscle integrity during nerve regeneration.

Mechanisms Underlying PRF-NGC Efficacy

PRF’s regenerative potential stems from its fibrin matrix and endogenous growth factors (e.g., VEGF, PDGF, TGF-β). The porous structure permits oxygen and nutrient diffusion while directing axonal growth. Furthermore, early vascularization within PRF-NGC likely created a scaffold for Schwann cell migration, as suggested by Cattin et al., who linked blood vessels to Schwann cell guidance.

Unlike previous studies using PRF gel within rigid conduits, this study’s tubular PRF membrane optimizes mechanical support and degradation kinetics. The conduit’s flexibility and suturability enhance surgical feasibility, while its transient presence avoids long-term complications.

Clinical Implications and Future Directions

PRF-NGC bridges critical gaps in nerve repair: it eliminates donor site morbidity associated with ANG and outperforms synthetic conduits in axonal regeneration. Its autologous origin and simple preparation (no anticoagulants or additives) make it clinically translatable. However, challenges remain, including scalability for larger nerve defects and optimization of growth factor release kinetics.

Future studies should explore PRF-NGC in larger animal models and assess combinatorial therapies, such as stem cell integration or electrical stimulation, to further accelerate regeneration.

Conclusion

This study establishes PRF-NGC as a promising alternative for peripheral nerve repair. Its biocompatibility, angiogenic potential, and ability to support axonal regeneration position it as a viable competitor to autologous grafts. By addressing both biological and structural requirements of nerve repair, PRF-NGC paves the way for improved functional outcomes in patients with peripheral nerve injuries.

doi.org/10.1097/CM9.0000000000000726

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