1Division of Plastic Surgery, Ann and Robert H. Lurie Children’s Hospital of Chicago, Stanley Manne Children’s Research Institute, 2Northwestern University Feinberg School of Medicine, Division of Plastic Surgery, Ann and Robert H. Lurie Children’s Hospital of Chicago, Stanley Manne Children’s Research Institute, 3Northwestern University Feinberg School of Medicine, Division of Plastic Surgery, 4Northwestern University Feinberg School of Medicine

Background

• These findings indicate that, despite ample time for complete regeneration, the survival of regenerated motoneurons diminishes along the length of a cross-face nerve graft

• Although a longer graft may have greater clinical utility in providing more options for end-target innervation, the middle/distal areas of a long nerve graft may not provide adequate axonal regeneration to realize this benefit

• Percentage of regenerated motoneurons with positive staining for nuclei in the Proximal group (76%) was not significantly different from Control (80%) p=0.433

• Traveling further to the distal region of the graft, decreased percentage of surviving regenerated motoneurons was observed

• Middle portion of graft showed 2.2x less % survived motoneurons compared to Control p<0.0001

• Distal portion of graft showed 8.9x less % survived motoneurons compared to Control p<0.0001

Research Objectives

Methods

Results

Conclusions

Correlation between regenerated motor neurons and graft length in rat cross-face nerve graftsLauren J. Kelsey, BS1, Joanna K. Ledwon, PhD2, Lindsay E. Janes, MD3, Daniel C. Sasson, BA4, Arun K. Gosain, MD2

Stanley Manne Children’s Research Institute

• Shorter autographs demonstrate improved axonal regeneration over longer autografts in a sciatic nerve model due to changes in the regenerative environment

• For an autograph of a given length, no research has shown how the axonal regeneration changes over the distance of the graft

(D) Schematic presentation of the nerve graft. (E) Quantitative analysis of survived regeneratedmotoneurons, indicated by the double-staining of FG and PI. Each bar correlates with the locationof FG SD. placement along the nerve graft. Significant differences are shown as ****p<0.0001.Error bars represent

(A) Schematic presentation of the facial nerve nucleus (7N) in rat brain. Representative 10x imagesof motoneurons in the facial nucleus after FG placement in (B) nerve trunk/control and (C) distalregion of the nerve graft. Fluoroshield PI was used as a counterstain to detect nuclei.

Essential question: Does the number of regenerating axons drop off over the distance of a cross-face nerve graft?

Given time for complete regeneration – 12 weeks – we aim to evaluate axonal regeneration from 4 distances along a cross-face nerve graft using retrograde labeling.

• Sciatic nerve of rats harvested and coapted to main trunk of facial nerve

• After 12 weeks, graft was sectioned within the Proximal, Middle, or Distal 5mm regions, in addition to the facial nerve trunk (Control)

• When cut, nerve end was immersed in 4% Fluoro-Gold (FG) for 1h, then returned to head

• After 1 week, brain was harvested, preserved, and frozen sections were taken at 40um

• Fluoroshield PI was used as nuclear counterstain; % of motoneurons was calculated as ratio of double-positive cells to all motoneurons detected with FG

Figure 1

• Analyzing the nerve tissue itself will allow us to explore how the biological environment that encapsulates the nerve graft impacts its survival

Future Directions