Alex Moir ’23
Exosomes, which carry biomolecular cargo around the body, are a group of vesicles secreted by almost all human cells. Exosomal delivery is also cell-specific, as the outer membrane surface of exosomes contains molecules that only bind with target recipient cell membranes. Recent research has suggested exosomes may play a role in wound healing and cell repair at sites of tissue damage, positioning them as a potential key to understanding nerve cell repairs. Indeed, Schwann cells in the nervous system are able to induce nerve cell recovery and regeneration in spinal cord injury by destroying apoptotic factors, or cell suicide factors, through autophagy. Autophagy is the self clearance and degradation of harmful or damaged parts by a cell. However, the exact mechanism for this autophagy-mediated recovery is unclear. A study published by researchers from the Tianjin Medical University investigated the possible role of exosomes in Schwann cell-mediated spinal cord injury recovery, hypothesizing that Schwann cells secrete exosomes that may target damaged neurons and deliver autophagy-stimulating cargo.
The researchers used rats with surgically severed spinal cord nerves to model spinal cord injury. After their motor function baseline was established, the rats were injected at the site of injury with exosomes isolated from cultured Schwann cells. Rats were then assessed for motor function every week after the initial injection for four weeks. The researchers took samples of the rat spinal cord tissue at the site of injury and used immunostaining to test for the presence of inflammatory and apoptotic factors, as well as cell death and autophagy. Rats treated with exosomes showed significant improvement compared to untreated rats, displaying progressive recovery of motor function. Immunostaining revealed significantly lower levels of inflammatory and apoptotic factors in exosome-treated rats, as well as lower levels of dead cells and higher levels of autophagy when compared to control rats. These results support exosomes playing a central role in stimulating the destruction of cellular apoptotic and inflammatory factors by delivering autophagy-promoting molecules, thus preventing cell death.
These findings demonstrate that exosomes play a significant role in Schwann cell-mediated spinal cord injury recovery. Since exosomes can be produced and isolated from cell culture, the findings present a new potential route for the development of treatments for spinal cord injury, which currently has no effective treatments available. Additionally, future research into the specific molecules carried by Schwann cell exosomes may further reveal the mechanisms behind nerve healing.
 D. Pan, et al., Autophagy induced by schwann cell-derived exosomes promotes recovery after spinal cord injury in rats. Biotechnology Letters 43, 1-14 (2021). doi: /10.1007/s10529-021-03198-8.
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