Transplantation of canine olfactory ensheathing cells producing chondroitinase ABC promotes chondroitin sulphate proteoglycan digestion and axonal sprouting following spinal cord injury

Olfactory ensheathing cell (OEC) transplantation is a promising strategy for treating spinal cord injury (SCI), as has been demonstrated in experimental SCI models and naturally occurring SCI in dogs. However, the presence of chondroitin sulphate proteoglycans within the extracellular matrix of the glial scar can inhibit efficient axonal repair and limit the therapeutic potential of OECs. Here we have used lentiviral vectors to genetically modify canine OECs to continuously deliver mammalian chondroitinase ABC at the lesion site in order to degrade the inhibitory chondroitin sulphate proteoglycans in a rodent model of spinal cord injury. We demonstrate that these chondroitinase producing canine OECs survived at 4 weeks following transplantation into the spinal cord lesion and effectively digested chondroitin sulphate proteoglycans at the site of injury. There was evidence of sprouting within the corticospinal tract rostral to the lesion and an increase in the number of corticospinal axons caudal to the lesion, suggestive of axonal regeneration. Our results indicate that delivery of the chondroitinase enzyme can be achieved with the genetically modified OECs to increase axon growth following SCI. The combination of these two promising approaches is a potential strategy for promoting neural regeneration following SCI in veterinary practice and human patients.

嗅鞘细胞（Olfactory ensheathing cell, OEC）移植是治疗脊髓损伤（spinal cord injury, SCI）的极具前景的策略，该结论已在脊髓损伤实验模型以及犬类自然发生的脊髓损伤案例中得到验证。然而，胶质瘢痕细胞外基质中的硫酸软骨素蛋白聚糖会阻碍高效的轴突修复进程，限制OEC的治疗潜能。本研究借助慢病毒载体对犬源OEC进行基因修饰，使其能够在损伤部位持续分泌哺乳动物软骨素酶ABC，以降解脊髓损伤啮齿动物模型中的抑制性硫酸软骨素蛋白聚糖。实验证实，这些分泌软骨素酶的犬源OEC在移植至脊髓损伤部位4周后仍可存活，并可有效降解损伤位点的硫酸软骨素蛋白聚糖。研究观察到，损伤前端的皮质脊髓束内出现轴突发芽现象，且损伤后端的皮质脊髓轴突数量有所增加，这提示轴突再生的发生。本研究结果表明，通过基因修饰的OEC可实现软骨素酶的递送，从而提升脊髓损伤后的轴突生长能力。将这两种颇具前景的策略相结合，有望成为兽医临床与人类患者中促进脊髓损伤后神经再生的潜在治疗方案。