Improved Healing after the Co-Transplantation of HO-1 and BDNF Overexpressed Mesenchymal Stem Cells in the Subacute Spinal Cord Injury of Dogs

Abundant expression of proinflammatory cytokines after a spinal cord injury (SCI) creates an inhibitory microenvironment for neuroregeneration. The mesenchymal stem cells help to mitigate the inflammation and improve neural growth and survival. For this purpose, we potentiated the function of adipose-derived mesenchymal stem cells (Ad-MSCs) by transfecting them with brain-derived neurotrophic factor (BDNF) and heme oxygenase-1 (HO-1), through a lentivirus, to produce BDNF overexpressed Ad-MSCs (BDNF-MSCs), and HO-1 overexpressed Ad-MSCs (HO-1-MSCs). Sixteen SCI beagle dogs were randomly assigned into four treatment groups. We injected both HO-1 and BDNF-overexpressed MSCs as a combination group, to selectively control inflammation and induce neuroregeneration in SCI dogs, and compared this with BDNF-MSCs, HO-1-MSCs, and GFP-MSCs injected dogs. The groups were compared in terms of improvement in canine Basso, Beattie, and Bresnahan (cBBB) score during 8 weeks of experimentation. After 8 weeks, spinal cords were harvested and subjected to western blot analysis, immunofluorescent staining, and hematoxylin and eosin (H&E) staining. The combination group showed a significant improvement in hindlimb functions, with a higher BBB score, and a robust increase in neuroregeneration, depicted by a higher expression of Tuj-1, NF-M, and GAP-43 due to a decreased expression of the inflammatory markers interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α), and an increased expression of interleukin-10 (IL-10) (P ≤ 0.05). H&E staining showed more reduced intraparenchymal fibrosis in the combination group than in other groups (P ≤ 0.05). It was thus suggested that the cotransplantation of HO-1 and BDNF-MSCs is more effective in promoting the healing of SCI. HO-1-MSCs reduce inflammation, which favors BDNF-induced neuroregeneration in SCI of dogs.

Effect of canine mesenchymal stromal cells overexpressing heme oxygenase-1 in spinal cord injury

Heme oxygenase-1 (HO-1) is a stress-responsive enzyme that modulates the immune response and oxidative stress associated with spinal cord injury (SCI). This study aimed to investigate neuronal regeneration via transplantation of mesenchymal stromal cells (MSCs) overexpressing HO-1. Canine MSCs overexpressing HO-1 were generated by using a lentivirus packaging protocol. Eight beagle dogs with experimentally-induced SCI were divided into GFP-labeled MSC (MSC-GFP) and HO-1-overexpressing MSC (MSC-HO-1) groups. MSCs (1 × 10⁷ cells) were transplanted at 1 week after SCI. Spinal cords were harvested 8 weeks after transplantation, after which histopathological, immunofluorescence, and western blot analyses were performed. The MSC-HO-1 group showed significantly improved functional recovery at 7 weeks after transplantation. Histopathological results showed fibrotic changes and microglial cell infiltration were significantly decreased in the MSC-HO-1 group. Immunohistochemical (IHC) results showed significantly increased expression levels of HO-1 and neuronal markers in the MSC-HO-1 group. Western blot results showed significantly decreased expression of tumor necrosis factor-alpha, interleukin-6, cycloogygenase 2, phosphorylated-signal transducer and activator of transcription 3, and galactosylceramidase in the MSC-HO-1 group, while expression levels of glial fibrillary acidic protein, β3-tubulin, neurofilament medium, and neuronal nuclear antigen were similar to those observed in IHC results. Our results demonstrate that functional recovery after SCI can be promoted to a greater extent by transplantation of HO-1-overexpressing MSCs than by normal MSCs.

Impact of local injection of brain-derived neurotrophic factor-expressing mesenchymal stromal cells (MSCs) combined with intravenous MSC delivery in a canine model of chronic spinal cord injury

BACKGROUND AIMS

The microenvironment of the chronically injured spinal cord does not allow for axonal regeneration due to glial scarring. To ameliorate this, several therapeutic strategies have been used. We investigated whether combined transplantation of chondroitinase ABC (chABC) and mesenchymal stromal cells (MSCs) genetically modified to secrete brain-derived neurotrophic factor (BDNF) with intravenous (IV) administration of MSCs can promote recovery of hindlimb function after chronic spinal cord injury (SCI).

METHODS

Canine BDNF-expressing MSCs were generated using a lentivirus packaging protocol. Twelve beagle dogs with experimentally induced chronic SCI were divided into chABC/MSC-green fluorescent protein (GFP), chABC/MSC-BDNF and chABC/MSC-BDNF/IV groups. The MSCs (1 × 107 cells) and chABC were transplanted 3 weeks after SCI in all groups, and IV injection of MSC-GFP (1 × 107 cells) was performed 1 and 2 weeks after MSC transplantation in the chABC/MSC-BDNF/IV group. Spinal cords were harvested 8 weeks after transplantation.

RESULTS

The dogs in the chABC/MSC-BDNF included groups had significantly improved functional recovery 8 weeks after transplantation compared with those in the chABC/MSC-GFP group. The animals in the chABC/MSC-BDNF/IV group showed significant improvements in functional recovery at 6, 7 and 8 weeks compared with those in the chABC/MSC-BDNF group. Fibrotic changes were significantly decreased in the chABC/MSC-BDNF/IV group. We also observed significant decreases in the expression levels of tumor necrosis factor-α, interleukin-6, COX-2, glial fibrillary acidic protein and GalC and increased expression levels of BDNF, β3-tubulin neurofilament medium, and nestin in the chABC/MSC-BDNF/IV group.

CONCLUSIONS

We suggest that transplantation of combined chABC and BDNF-expressing MSCs, along with IV injection of MSCs, is the optimal therapy for chronic SCI.