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The Role Of Lymphatic Channels In Peripheral Nerve Regeneration: A Pilot Animal Study With A Rat Inguinal Lymph Node Flap Model
Daiki Kitano, MD,
Michael Mazarei, MD candidate, Shayan M. Sarrami, MD, Chiaki Komatsu, MD, Baris Bengur, MD, Kacey G. Marra, PHD, Carolyn De La Cruz, MD.
University of Pittsburgh, Pittsburgh, PA, USA.
PURPOSE: The lymphatic system regulates the microenvironment at sites of injury by draining interstitial fluid, limiting edema, and exerting anti-inflammatory effects. However, it's role within peripheral nerve regeneration is understudied. We evaluated whether transplanted lymphatic tissue promotes axonal regeneration.
METHODS: In this study, we developed a rat vascularized lymph node transfer model based on the superficial inferior epigastric artery (SIEA) flap. Inguinal lymph nodes (LNs) were harvested as pedicled SIEA flaps and microsurgically wrapped around transected, epineurally repaired sciatic nerves to place the LN in direct contact with the neurorrhaphy site. At 8 weeks, nerves were harvested for histology. Lymphatic/vascular structures were identified by podoplanin (PDPN) and CD31 double immunofluorescence; regenerated axons were labeled with S100β. Quantification included PDPN/CD31 double-positive structures per 500-µm˛ intraneural region and S100β-positive profiles distal to the repair.
RESULTS: In uninjured nerves, PDPN/CD31 double-positive vessels were common in peri-epineurial fibrofatty tissue—typically adjacent to CD31-only blood vessels—but were rare within nerve fibers. LN flap coverage produced a marked rise in intraneural lymphatic channels (mean 17.4 per 500-µm˛), exceeding both uninjured nerves (3.4, p=0.0006) and neurorrhaphy-only repairs (3.0, p=0.0004). Axonal regeneration paralleled these findings: distal S100β-positive counts were higher with LN flaps (135.1) than neurorrhaphy alone (23.8, p<0.0001), though below uninjured controls (228.4, p=0.001).
CONCLUSION: Transplanted inguinal LNs induce intraneural lymphatic channel formation and create a microenvironment supportive of axonal regrowth after sciatic nerve repair. Lymphatic tissue transfer may augment peripheral nerve reconstruction. Ongoing work will validate true lymphangiogenesis and correlate histology with motor and sensory recovery.
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