The glial scar resulting from spinal cord injury is rich in chondroitin sulfate proteoglycan (CSPG), a formidable barrier to axonal regeneration. We explored the possibility of breaching that barrier by first examining the scar in a functional in vitro model. We found that embryonic stem cell-derived neural lineage cells (ESNLCs) with prominent expression of nerve glial antigen 2 (NG2) survived, passed through an increasingly inhibitory gradient of CSPG, and expressed matrix metalloproteinase 9 (MMP-9) at the appropriate stage of their development. Outgrowth of axons from ESNLCs followed because the migrating cells sculpted pathways in which CSPG was degraded. The degradative mechanism involved MMP-9 but not MMP-2. To confirm these results in vivo, we transplanted ESNLCs directly into the cavity of a contused spinal cord 9 days after injury. A week later, ESNLCs survived and were expressing both NG2 and MMP-9. Their axons had grown through long distances (>10 mm), although they preferred to traverse white rather than gray matter. These data are consistent with the concept that expression of inhibitory CSPG within the injury scar is an important impediment to regeneration but that NG2+ progenitors derived from ESNLCs can modify the microenvironment to allow axons to grow through the barrier. This beneficial action may be partly due to developmental expression of MMP-9. We conclude that it might eventually be possible to encourage axonal regeneration in the human spinal cord by transplanting ESNLCs or other cells that express NG2.

BACKGROUND AND OBJECTIVES: Despite many publications about cavernous malformations (CMs), controversy remains regarding diagnostic and management strategies. To update evidence-based guidelines for the clinical management of brain and spinal cord CMs. METHODS: The Alliance to Cure CMs, the patient support group in the United States advocating on behalf of patients and research in CM, convened a multidisciplinary writing group comprising expert CM clinicians to help summarize the existing literature related to the clinical care of CM, focusing on 5 topics: (1) epidemiology and natural history, (2) genetic testing and counseling, (3) diagnostic criteria and imaging standards, (4) neurosurgical considerations, and (5) neurological considerations. Building on prior evidence-based recommendations reflecting literature review through October 2014, the group conducted a systematic review of the more recent literature, identified references for mandatory citation, rated evidence, developed recommendations, and established consensus according to a prespecified protocol. Finally, the writing group outlined remaining knowledge gaps and controversies to guide future research. RESULTS: From 2672 publications published between October 1, 2014, and March 15, 2023, and meeting key word criteria, 234 were selected based on prearticulated criteria for mandatory consideration in evidence-based recommendations. Topic authors used these and other supporting references to summarize current knowledge and arrive at 53 management recommendations, with unanimous consensus based on a Delphi process. These were rated by class (strength of recommendation) and level (quality of evidence) per the American Heart Association/American Stroke Association criteria. Eighteen recommendations were class 1 (34%), class 2 in 31 (58%), and class 3 in 4 (8%). Three were level A (6%), 19 (36%) were level B, and 31 (58%) were level C. CONCLUSION: Current evidence supports prior and new recommendations for the management of CMs, but many reflect moderate classes and low levels, mandating further research to better inform clinical practice.