Non-functionalized soft alginate hydrogel promotes locomotor recovery after spinal cord injury in a rat hemimyelonectomy model

BACKGROUND

Spinal cord injury (SCI) and the consecutive devastating neurological sequelae have an enormous individual and economic impact. Implantation of functionalized hydrogels is a promising approach, because they can serve as a matrix for the regenerating tissue, carry and release bioactive molecules and various cell types. We already demonstrated that non-functionalized soft alginate hydrogel supported axonal outgrowth and protected neurons against oxidative stress in vitro. Here, we investigated the effects of such soft alginate hydrogels on locomotor recovery in small and large spinal cord lesions.

METHOD

Hemimyelonectomy of 2 mm or 4 mm length was performed in rats and soft alginate hydrogel was implanted. Functional recovery of the hindlimbs was assessed in the open field [Batto Beattie Bresnahan (BBB) score] and using swimming test [Louisville Swim score (LSS)] for 140 days post injury (DPI). Reference histology was performed.

RESULTS

Rats that received an alginate implant into 2 mm spinal cord lesions demonstrated significantly improved locomotor recovery compared to controls detectable already at 10 DPI. At 140 DPI, they reached higher LSS and BBB scores in swimming and open field tests, respectively. However, this beneficial effect of alginate was lacking in animals with larger (4 mm) lesions. Histological examination suggested that fibrous scarring in the spinal cord was reduced after alginate implantation in comparison to controls.

CONCLUSIONS

Implantation of soft alginate hydrogel in small spinal cord lesions improved functional recovery. Possible underlying mechanisms include the mechanical stabilization of the wound, reduction of secondary damage and inhibition of fibrous scarring.

Interactive effects of ghrelin and ketamine on forced swim performance: Implications for novel antidepressant strategies

The efficacy of ketamine to alleviate depressive symptoms has promoted a wealth of research exploring alternate therapeutic targets for depression. Given the caveats of ketamine treatment taken together with the increasingly greater emphasis on combinatorial therapeutic approaches to depression, we sought to asses whether the hypothalamic "hunger hormone", ghrelin, would augment the effects of ketamine. Indeed, ghrelin has recently been found to possess antidepressant potential and may be especially effective against the metabolic and feeding deficits observed with depression. Two studies were performed: 1. mice were given an intraperitoneal injection of ghrelin (80μg/kg) or saline, followed by a saline or a low or high dose of ketamine (5 or 10mg/kg) and 2. mice received 10mg/kg of ketamine together with saline or the ghrelin receptor antagonist JMV2959 (3 or 6mg/kg) and Forced Swim Test (FST) performance was assessed. In both studies, ketamine alone reduced FST immobility. Similarly, ghrelin alone reduced swim immobility suggesting an antidepressant-like response. However, ghrelin did not augment the impact of ketamine when co-administered and in fact, it appeared to antagonize its actions at the lower dose. As well, JMV2959 did not significantly influence FST performance. These data confirm the antidepressant-like effects of ketamine and further suggest that ghrelin might have similar properties. Yet, our results caution against combinatorial treatment with these agents, probably owing to unexpected allosteric or other antagonist actions.