A major barrier to intraspinal regeneration after dorsal root (DR) injury is the DR entry zone (DREZ), the CNS/PNS interface. DR axons stop regenerating at the DREZ, even if regenerative capacity is increased by a nerve conditioning lesion. This potent blockade has long been attributed to myelin-associated inhibitors and CSPGs, but incomplete lesions and conflicting reports have prevented conclusive agreement. Here we evaluated DR regeneration in mice, using novel strategies to facilitate complete lesions and analyses, selective tracing of proprioceptive and mechanoreceptive axons, and the first simultaneous targeting of Nogo/Reticulon-4, MAG, OMgp, CSPGs and GDNF. Co-eliminating myelin inhibitors and CSPGs elicited regeneration of only a few conditioning-lesioned DR axons across the DREZ. Their absence, however, markedly and synergistically enhanced regeneration of GDNF-stimulated axons, highlighting the importance of sufficiently elevating intrinsic growth capacity. We also conclude that myelin inhibitors and CSPGs are not the primary mechanism stopping axons at the DREZ.
Numerical data generated or analyzed during this study are included in the manuscript and supporting files. Source data files have been submitted for Figures 3, 4, 5,6, 6-S1, 7, 8, 9.
- Young-Jin Son
- Young-Jin Son
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
Animal experimentation: All animal care and procedures were conducted in accordance with the National Research Council's Guide for the Care and Use of Laboratory Animals and approved by the Institutional Animal Care and Use Committee at Lewis Katz School of Medicine at Temple University, Philadelphia, PA, USA. (animal protocol #4919),
- Lilianna Solnica-Krezel, Washington University School of Medicine, United States
- Received: September 11, 2020
- Accepted: May 3, 2021
- Accepted Manuscript published: May 4, 2021 (version 1)
© 2021, Zhai et al.
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