Defining recovery neurobiology of injured spinal cord by synthetic matrix-assisted hMSC implantation

Abstract

Mesenchymal stromal stem cells (MSCs) isolated from adult tissues offer tangible potential for regenerative medicine, given their feasibility for autologous transplantation. MSC research shows encouraging results in experimental stroke, amyotrophic lateral sclerosis, and neurotrauma models. However, further translational progress has been hampered by poor MSC graft survival, jeopardizing cellular and molecular bases for neural repair in vivo. We have devised an adult human bone marrow MSC (hMSC) delivery formula by investigating molecular events involving hMSCs incorporated in a uniquely designed poly(lactic-co-glycolic) acid scaffold, a clinically safe polymer, following inflammatory exposures in a dorsal root ganglion organotypic coculture system. Also, in rat T9-T10 hemisection spinal cord injury (SCI), we demonstrated that the tailored scaffolding maintained hMSC stemness, engraftment, and led to robust motosensory improvement, neuropathic pain and tissue damage mitigation, and myelin preservation. The scaffolded nontransdifferentiated hMSCs exerted multimodal effects of neurotrophism, angiogenesis, neurogenesis, antiautoimmunity, and antiinflammation. Hindlimb locomotion was restored by reestablished integrity of submidbrain circuits of serotonergic reticulospinal innervation at lumbar levels, the propriospinal projection network, neuromuscular junction, and central pattern generator, providing a platform for investigating molecular events underlying the repair impact of nondifferentiated hMSCs. Our approach enabled investigation of recovery neurobiology components for injured adult mammalian spinal cord that are different from those involved in normal neural function. The uncovered neural circuits and their molecular and cellular targets offer a biological underpinning for development of clinical rehabilitation therapies to treat disabilities and complications of SCI.spinal cord injury | recovery neurobiology | mesenchymal stromal stem cell | PLGA | locomotion R epair of neurotrauma, stroke, and neurodegenerative diseases remains an unmet medical demand because of their pathophysiological complexity and the limited spontaneous healing capacity of adult mammalian CNS. Human mesenchymal stromal stem cells (hMSCs) offer autologous transplantation feasibility (1-4) and have been studied both experimentally and clinically for traumatic brain injury (TBI) and spinal cord injury (SCI) (5-8). Although MSCs possess homeostatic and proneurogenic activities (7, 9), studies relying on neural transdifferentiation (i.e., putative differentiations of MSCs into neural cells without reentering the pluripotency phase) did not show long-term functional improvement in SCI models. The poor outcomes were attributed mainly to suboptimal survival of MSCs, leaving key therapeutic mechanisms undetermined (10). We previously established a 3D cell delivery technology by seeding neural stem cells (NSCs) in biodegradable polymer scaffolds that significantly improved donor efficacy and enabled investigation of NSC repair mechanisms in t...

Establishing an Organotypic System for Investigating Multimodal Neural Repair Effects of Human Mesenchymal Stromal Stem Cells

“…Any established hMSC line can be characterized following the procedures and parameters described in protocol. For our original studies, hMSC lines were established from cells obtained from either a 26-year-old male donor (7023-R) or a 29-year-old female donor (7038-L) at the Tulane University Center for Gene Therapy, an NIH-funded cell distribution center Ropper et al, 2017).…”

“…Current Protocols in Stem Cell Biology tailored with unique porous, soft, and smooth features to maintain the stemness biology of hMSCs (Ropper et al, 2017).…”

“…These cells and their physiological and pathophysiological interactions function in normal and repair/regenerative responses to nerve injury that can be investigated mechanistically (Scholz & Woolf, 2007;Thakor et al, 2009). In a recent study (Ropper et al, 2017), we experimented with hMSC-DRG co-cultures by plating hMSCs over adult rat DRG explants embedded in trophic factor reduced matrigel, a gelatinous protein mixture initially produced by Engelbreth-Holm-Swarm (EHS) mouse sarcoma cells (i.e., Matrigel R , manufactured and marketed by Corning Life Sciences and BD Biosciences). We found that proper matrigel plating introduced a substrate that was suitable for examining profiles of DRG neuritogenesis (Leclere et al, 2007;Thakor et al, 2009), whereas direct seeding of hMSCs enabled both physical and chemical communication with DRGs.…”

“…The events can be recapitulated directly by using a DRG following surgical removal, or with further manipulation in vitro to investigate selective targets (e.g., exposure to specific trophic or tropic factor, and proinflammatory or anti-inflammatory molecules). Importantly, desirable stem cell or polymer scaffolding features determined by this platform technology may be used to design stem cell-based multimodal implants to investigate or offer repair and regenerative mechanisms in vivo for the injured or diseased spinal cord or brain (Kaplan et al, 2018;Ropper et al, 2017;Teng et al, 2002Teng et al, , 2011Teng et al, , 2012Yu et al, 2009).…”

Holistic Approach to Axonal Regeneration in Cases of Spinal Cord Injury

“…These non-toxic materials can be used to form robust bridges and scaffolds which facilitate nerve regeneration. Recent studies have also found that multiple poly (lactic-co-glycolic) channels can serve as bridges that physically direct the growth of axons across the injury while also optimizing the post-traumatic spinal cord microenvironment [78][79][80]. Numerous methods have been developed to synthesize bridges using natural or synthetic polymers [81], and certain biomaterials have been shown to provide neuroprotective benefits for SCI patients.…”