Treatment of rats with spinal cord injury using human bone marrow-derived stromal cells prepared by negative selection

Abstract

Background: Spinal cord injury (SCI) is a highly debilitating pathology without curative treatment. One of the most promising disease modifying strategies consists in the implantation of stem cells to reduce inflammation and promote neural regeneration. In the present study we tested a new human bone marrow-derived stromal cell preparation (bmSC) as a therapy of SCI.Methods: Spinal cord contusion injury was induced in adult male rats at thoracic level T9/T10 using the Infinite Horizon impactor. One hour after lesion the animals were treated with a sub-occipital injection of human bmSC into the cisterna magna. No immune suppression was used. One dose of bmSC consisted, on average, of 2.3 million non-manipulated cells in 100 μL suspension, which was processed out of fresh human bone marrow from the iliac crest of healthy volunteers. Treatment efficacy was compared with intraperitoneal injections of methylprednisolone (MP) and saline. The recovery of motor functions was assessed during a surveillance period of nine weeks. Adverse events as well as general health, weight and urodynamic functions were monitored daily. After this time, the animals were perfused, and the spinal cord tissue was investigated histologically.Results: Rats treated with bmSC did not reject the human implants and showed no sign of sickness behavior or neuropathic pain. Compared to MP treatment, animals displayed better recovery of their SCI-induced motor deficits. There were no significant differences in the recovery of bladder control between groups. Histological analysis at ten weeks after SCI revealed no differences in tissue sparing and astrogliosis, however, bmSC treatment was accompanied with reduced axonal degeneration in the dorsal ascending fiber tracts, lower Iba1-immunoreactivity (IR) close to the lesion site and reduced apoptosis in the ventral grey matter. Neuroinflammation, as evidenced by CD68-IR, was significantly reduced in the MP-treated group.Conclusions: Human bmSC that were prepared by negative selection without expansion in culture have neuroprotective properties after SCI. Given the effect size on motor function, implantation in the acute phase was not sufficient to induce spinal cord repair. Due to their immune modulatory properties, allogeneic implants of bmSC can be used in combinatorial therapies of SCI.

Why do anti-inflammatory signals of bone marrow-derived stromal cells improve neurodegenerative conditions where anti-inflammatory drugs fail?

“…Such transplants supposedly modulate the immune system in both acute (Deda et al 2008;Martinez et al 2017;Tsai et al 2018;Cofano et al 2019;Jin et al 2019) and chronic (Mazzini et al 2016;Ciervo et al 2017;Gashmardi et al 2017;Sykova et al 2017;Cizkova et al 2018;Garbuzova-Davis et al 2018;Oh et al 2018;Gugliandolo et al 2019) neurodegenerative disorders in experimental animals as well as in patients. Our own experiments with human bm-SC in experimental animal models of both an acute (traumatic spinal cord injury; tSCI) (de Munter et al 2019a;Romero-Ramirez et al 2020) and a chronic neurodegenerative disorder (amyotrophic lateral sclerosis; ALS) (de Munter et al 2019b) were fully in line with these findings. In these studies, fresh bm-SCs specimen were manufactured into standardized preparations for intrathecal application, to bring naïve stem cells into the environment where neuroinflammation and degeneration are ongoing.…”

“…The lesion size in the animals treated with bm-SCs was somewhat smaller than in the rats treated with vehicle and methylprednisolone, but not significantly. An interesting finding, though, was the significantly lower expression of Iba-1 in the lesion site of the animals treated with bm-SCs, but not in the animals treated with methylprednisolone and/or vehicle (Romero-Ramirez et al 2020) confirming the hypothesis that bm-SCs reach anti-inflammatory effects by different means than pharmacological interventions.…”

“…We explored the effect of an intrathecal transplantation with bm-SCs (4 × 10 5 CD34 + cells) in both T-cell-deficient and immune-competent Wistar rats, 1 day after a traumatic spinal cord injury, resulting in a complete paraplegia (de Munter et al 2019a;Romero-Ramirez et al 2020). Bm-SCs were found to be free of side effects, to significantly protect for SCI-related mortality, and to improve natural motor recovery (Basso et al 1995) compared to placebotreated animals, in the following weeks (de Munter et al 2019a).…”

“…Bm-SCs were found to be free of side effects, to significantly protect for SCI-related mortality, and to improve natural motor recovery (Basso et al 1995) compared to placebotreated animals, in the following weeks (de Munter et al 2019a). When compared to an acute 48-h intra-peritoneal high-dose methylprednisolone (MP) application (Romero- Ramirez et al 2020), bm-SC again significantly improved locomotor functions (Basso et al 1995) and restored body weight. Bm-SC-treated rats also never evidenced SCIassociated neuropathic pains during testing of mechanical nociception (von Frey), as sporadically seen in SCI rats treated with placebo and/or MP.…”

“…To further address the question why immune-modulating bm-SCs strategies are more successful than antiinflammatory drugs in human neurodegenerative disorders, we want to summarize the different cytokines and proteins with the relevant pathway and want to discuss a compilation of all findings from three preclinical studies, looking after the effects of an intervention with bm-SC in in SCI and ALS-like animal models (de Munter et al 2019a, b;Romero-Ramirez et al 2020). The following cytokines and proteins were studied in the mentioned preclinical experiments:…”