Grafting of Encapsulated BDNF-Producing Fibroblasts into the Injured Spinal Cord Without Immune Suppression in Adult Rats

Abstract

Grafting of genetically modified cells that express therapeutic products is a promising strategy in spinal cord repair. We have previously grafted BDNF-producing fibroblasts (FB/BDNF) into injured spinal cord of adult rats, but survival of these cells requires a strict protocol of immune suppression with cyclosporin A (CsA). To develop a transplantation strategy without the detrimental effects of CsA, we studied the properties of FB/BDNF that were encapsulated in alginate-poly-L-ornithine, which possesses a semipermeable membrane that allows production and diffusion of a therapeutic product while protecting the cells from the host immune system. Our results show that encapsulated FB/BDNF, placed in culture, can survive, secrete bioactive BDNF and continue to grow for at least one month. Furthermore, encapsulated cells that have been stored in liquid nitrogen retain the ability to grow and express the transgene. Encapsulated FB/BDNF survive for at least one month after grafting into an adult rat cervical spinal cord injury site in the absence of immune suppression. Transgene expression decreased within two weeks after grafting but resumed when the cells were harvested and re-cultured, suggesting that soluble factors originating from the host immune response may contribute to the downregulation. In the presence of capsules that contained FB/BDNF, but not cell-free control capsules, there were many axons and dendrites at the grafting site. We conclude that alginate encapsulation of genetically modified cells may be an effective strategy for delivery of therapeutic products to the injured spinal cord and may provide a permissive environment for host axon growth in the absence of immune suppression.

3D‐model of adult cardiac stem cells promotes cardiac differentiation and resistance to oxidative stress

“…Other positively charged surfaces, such as poly-L-lysine, but not PLO, have been used previously to facilitate the formation of hepatocyte aggregates exhibiting liver-specific functions [Tzanakakis et al, 2001]. PLO, similar to other polycations especially poly-L-lysine, has been used mostly in combination with other molecules for various applications such as non-viral gene delivery [Fimmel et al, 2000;Ramsay and Gumbleton, 2002;Brown et al, 2003], packaging system (in alginate beads) for cellular grafts [Tobias et al, 2001;Calafiore, 2003], or as attachment matrix/ scaffold for neuronal and embryonic stem cell cultures [Murashov et al, 2005;Flanagan et al, 2006;Morizane et al, 2006]. Polyamino acids, such as PLO, have also been shown to activate cell signaling pathways [Haber et al, 1991].…”

Neurotrophic Factors Used to Treat Spinal Cord Injury

“…Interestingly, adult SCI is similarly known to alter p75 expression (Ji et al, 2015;King et al, 2000;Liebl et al, 2001), which could potentially affect the action of exogenously applied BDNF. In contrast to these inconsistent effects on CST regeneration, many studies have reported regrowth of 5HT fibers in response to BDNF administration (Boyce et al, 2007;Brock et al, 2010;Coumans et al, 2001;Golden et al, 2007;Koda et al, 2007;Lu et al, 2005;Tobias et al, 2001), which has the potential to facilitate locomotor recovery (Slawinska, Miazga, & Jordan, 2014).…”

“…After direct AAV injection, sustained expression of BDNF and NT-3 has been described in cells in the injured spinal cord up to 16 weeks' postinjection . In contrast, downregulation of the BDNF gene in encapsulated fibroblasts 2 weeks after transplantation into an adult rat cervical SCI was reported (Tobias et al, 2001). Interestingly, expression returned when the cells were harvested and put back into culture, "suggesting that soluble factors originating from the host immune response may contribute to the down-regulation" (Tobias et al, 2001).…”

Neural ECM mimetics

“…As the cross-linking multivalent cations gradually diffuse out from the gel, it slowly degrades and is excreted in urine. Alginate gels are frequently used as matrices for encapsulation of living cells and for the release of proteins (Novikova et al, 2006;Tobias et al, 2001Tobias et al, , 2005. In regeneration studies, alginate gels are often applied as cell carrier substances.…”