Astrocyte-selective AAV-ADAMTS4 gene therapy combined with hindlimb rehabilitation promotes functional recovery after spinal cord injury

Abstract

Chondroitin sulphate proteoglycans (CSPGs) are inhibitors to axon regeneration and plasticity. Bacterial chondroitinase ABC degrades CSPGs and has been extensively reported to be therapeutic after SCI but there remain concerns for its clinical translation. A disintegrin and metalloproteinase with thrombospondin motifs-4 (ADAMTS4) is a human enzyme that catalyses the proteolysis of CSPG protein cores. Infusion of ADAMTS4 into the damaged spinal cord was previously shown to improve functional recovery after SCI, however, this therapy is limited in its enzyme form. Adeno-associated viral (AAV) vector gene therapy has emerged as the vector of choice for safe, robust and long-term transgene expression in the central nervous system. Here, an AAV expression cassette containing ADAMTS4 under the control of the astrocytic GfaABC 1 D promoter was packaged into an AAV5 vector. Sustained expression of ADAMTS4 was achieved in vitro and in vivo, leading to widespread degradation of CSPGs. AAV-ADAMTS4 resulted in significantly decreased lesion size, increased sprouting of hindlimb corticospinal tract axons, increased serotonergic fiber density caudal to the injury, and improved functional recovery after moderate contusive SCI.Hindlimb-specific exercise rehabilitation was used to drive neuroplasticity towards improving functional connections. The combination of hindlimb rehabilitation with AAV-ADAMTS4 led to enhanced functional recovery after SCI. Thus, widespread and long-term degradation of CSPGs through AAV-ADAMTS4 gene therapy in a combinational approach with rehabilitation represents a promising candidate for further preclinical development. AbbreviationsAAV Adeno-associated virus ADAMTS A disintegrin and metalloproteinase with thrombospondin motifs ChABC Chondroitinase ABC CS-GAG Chondroitin sulphate glycosaminoglycan CSPG Chondroitin sulphate proteoglycan ECM Extracellular matrix GAG Glycosaminoglycan LV Lentiviral vector

Therapeutic repair for spinal cord injury: combinatory approaches to address a multifaceted problem

“…Instead, sequential rehabilitation regimes are astonishingly effective and in some cases can almost completely restore specific motor tasks (Table 5; Garcia-Alias et al, 2009;Chen et al, 2017). More recently, endogenous CSPG degradation by an astrocyte-selective AAV-ADAMTS4 gene therapy combined with hindlimb rehabilitation enhanced functional recovery following rat thoracic SCI compared to either intervention alone (Griffin et al, 2020). Current reports for the role of rehabilitation with cell transplantation are limited to one preclinical study which enlisted autologous bone marrow stem cells with swim training where a difference to functional parameters between groups was observed (Carvalho et al, 2008).…”

AAV Targeting of Glial Cell Types in the Central and Peripheral Nervous System and Relevance to Human Gene Therapy

“…A number of studies have used AAV vectors containing the 681 bp gfaABC 1 D with the goal of obtaining astrocyte specificity ( Xie et al, 2010 ; Theofilas et al, 2011 ; Dirren et al, 2014 ; Dvorzhak et al, 2016 ; Vagner et al, 2016 ; Taschenberger et al, 2017 ; Griffin et al, 2019 , 2020 ; Testen et al, 2020 ). While several studies show good evidence of astrocyte specificity ( Xie et al, 2010 ; Theofilas et al, 2011 ), other studies report transduction of other cell types ( Taschenberger et al, 2017 ; Griffin et al, 2019 ).…”

Human ex vivo spinal cord slice culture as a useful model of neural development, lesion, and allogeneic neural cell therapy

“…Moreover, they may recapitulate or mimic lesion pathology, allowing the study of pathological and regenerative pathways in tissue-like complexity [ 13 , 14 ]. Therefore, an established human nervous system slice culture model would allow promising repair strategies including gene [ 15 , 16 ] as well as neural cell therapeutic approaches [ 17 – 20 ] to be pre-clinically tested in human conditions. Thus, as a complementary method (allowing human spinal cord study, while reducing costs and resource demands in addition to animal use), human slice culture, when available, is of value.…”