Transplantation of Schwann cells and/or olfactory ensheathing glia into the contused spinal cord: Survival, migration, axon association, and functional recovery

Abstract

Schwann cells (SCs) and olfactory ensheathing glia (OEG) have shown promise for spinal cord injury repair. We sought their in vivo identification following transplantation into the contused adult rat spinal cord at 1 week post-injury by: (i) DNA in situ hybridization (ISH) with a Y-chromosome specific probe to identify male transplants in female rats and (ii) lentiviral vector-mediated expression of EGFP. Survival, migration, and axon-glia association were quantified from 3 days to 9 weeks post-transplantation. At 3 weeks after transplantation into the lesion, a 60-90% loss of grafted cells was observed. OEG-only grafts survived very poorly within the lesion (<5%); injection outside the lesion led to a 60% survival rate, implying that the injury milieu was hostile to transplanted cells and or prevented their proliferation. At later times post-grafting, p75(+)/EGFP(-) cells in the lesion outnumbered EGFP(+) cells in all paradigms, evidence of significant host SC infiltration. SCs and OEG injected into the injury failed to migrate from the lesion. Injection of OEG outside of the injury resulted in their migration into the SC-injected injury site, not via normal-appearing host tissue but along the pia or via the central canal. In all paradigms, host axons were seen in association with or ensheathed by transplanted glia. Numerous myelinated axons were found within regions of grafted SCs but not OEG. The current study details the temporal survival, migration, axon association of SCs and OEG, and functional recovery after grafting into the contused spinal cord, research previously complicated due to a lack of quality, long-term markers for cell tracking in vivo.

Canine olfactory ensheathing cells from the olfactory mucosa can be engineered to produce active chondroitinase ABC

“…This was comparable to concentrations that have produced significant functional improvements in vivo in rat SCI models (11,16). Despite the robust levels of ChABC seen in vitro, it is possible that a proportion of OMCs will not survive following SCI transplantation (73). Therefore, with our current transduction efficiency of 34%, there may not be enough surviving ChABC-producing cells at the site of injury to achieve the desired in vivo efficacy.…”

“…However, if necessary we can increase the transduction percentage of the OMCs by using fluorescence-activated cell sorting to select OMCs expressing GFP (74,75), and therefore ChABC, leading to a cell transplant with closer to 100% transduction. It should be noted that from a clinical standpoint, OMC transplants are more likely to be given in the 'chronic' phase of SCI, at which point cell survival is greater than with acute transplantation (73). Clinical transplantation protocols will also include injection of cells cranial and caudal to the lesion, allowing cells to migrate into the lesion (76), which could also improve efficacy.…”

Transplantation and repair: Combined cell implantation and chondroitinase delivery prevents deterioration of bladder function in rats with complete spinal cord injury

“…10 Before surgery, animals were anesthetized with Hypnorm (fentanyl citrate, 120 ml per 200 g body weight; Janssen Pharmaceutics, Beerse, Belgium) and Midazolam (0.75 mg in 150 ml per 200 g body weight; S.C.; Sabex, Boucherville, QC, Canada). After a T7-9 laminectomy of the vertebral segment, 1 mm of spinal cord at Th8 was removed.…”

Neurotrophins: Potential Therapeutic Tools for the Treatment of Spinal Cord Injury

“…In addition to potentially myelinating regenerated axons, Schwann cells express cell adhesion molecules, produce components of the extracellular matrix, and secrete multiple neurotrophic factors [44][45][46][47][48][49][50][51][52][53]. Whether grafted Schwann cells provide an advantage in comparision with other potential cell grafts remains to be determined; however, as the grafted cells survive poorly in the lesioned spinal cord, they are soon replaced by migrating endogenous Schwann cells [54,55].…”