Abstract
To optimize gene delivery to myelinating Schwann cells we compared clinically relevant AAV serotypes and injection routes. AAV9 and AAVrh10 vectors expressing either EGFP or the neuropathy-associated gene GJB1/Connexin32 (Cx32) under a myelin specific promoter were injected intrathecally or intravenously in wild type and Gjb1-null mice, respectively. Vector biodistribution in lumbar roots and sciatic nerves was higher in AAVrh10 injected mice while EGFP and Cx32 expression rates and levels were similar between the two serotypes. A gradient of biodistribution away from the injection site was seen with both intrathecal and intravenous delivery, while similar expression rates were achieved despite higher vector amounts injected intravenously. Quantified immune cells in relevant tissues were similar to non-injected littermates. Overall, AAV9 and AAVrh10 efficiently transduce Schwann cells throughout the peripheral nervous system with both clinically relevant routes of administration, although AAV9 and intrathecal injection may offer a more efficient approach for treating demyelinating neuropathies.
Highlights
Inherited neuropathies known as Charcot-Marie-Tooth (CMT) disease are heterogeneous disorders caused by mutations in many different genes and remain without effective t reatment[1,2]
AAV9-Mpz.Egfp and AAVrh10-Mpz.Egfp vectors carrying the Egfp gene were injected into 2-month-old wild type (WT) mice, while AAV9-Mpz.GJB1 and AAVrh10- Mpz.GJB1vectors carrying the GJB1 gene were injected in Gjb1-null mice in order to study their biodistribution and compare their efficacy to transduce Schwann cells
In order to achieve Schwann cell-specific expression, we used the peripheral nervous system (PNS) myelin-specific Mpz promoter[4,31,32] and delivered AAV vectors carrying either the reporter gene Egfp or the neuropathy associated gene GJB1 by lumbar intrathecal or by intravenous injection. We demonstrate that both vectors resulted in Schwann cell specific and widespread expression in PNS tissues showing similar biodistribution and gene expression pattern
Summary
Inherited neuropathies known as Charcot-Marie-Tooth (CMT) disease are heterogeneous disorders caused by mutations in many different genes and remain without effective t reatment[1,2]. The aim of this study was to clarify the most efficient viral vectors and clinically relevant delivery methods to target PNS myelinating Schwann cells. AAVrh[10] has shown expression in the PNS including dorsal root ganglia (DRGs)[17] and spinal n erves[16], with functional[17] and morphological improvements in peripheral nerves[14,15]. These studies showed that the genes carried by AAVrh[10] can be expressed in the PNS, expression was driven by ubiquitous promoters and was not targeted to Schwann cells. Studies are mainly focused on the CNS biodistribution while there are data showing that both vectors can reach the sciatic nerve[14,16,17,23] with no targeted expression
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