Research may lead to better treatment for peripheral nerve damage

Researchers know that certain cells in the immune system help repair damage after an injury to a peripheral nerve — the nervous system tissue that connects muscles and organs to the brain and spinal cord and is responsible for controlling sensation, movement and motor co-ordination. But how these immune cells help nerve cells during regeneration has not been very well understood. Until now.

In a paper published in Cell Reports, researchers from the University of Calgary Faculty of Veterinary Medicine (UCVM) and Hotchkiss Brain Institute (HBI) identify specific neurochemicals emitted by immune cells, called macrophages, that help the specialized glial cells, called Schwann cells, to regenerate myelin, the fatty sheath that wraps around nerve fibres.

“We’re furthering the understanding about the interaction between the immune system and supportive cells. We’ve shown that immune cells secrete growth factors that can help the Schwann cells, the support cells, with the regenerative process,” says Dr. Jo Anne Stratton, PhD, a post doc in Jeff Biernaskie and Rajiv Midha’s lab (pictured above). “We’re one of the first to identify the signals that allow macrophages to influence Schwann cell function and to promote the formation of new myelin, a very important fatty tissue that helps the nerves conduct more efficiently.”

The research could lead to more effective treatment for people who have suffered peripheral nerve damage. In prior research, Dr. Midha, MD, professor and department head of  the Department of Clinical Neurosciences at the Cumming School of Medicine, demonstrated that about three per cent of Canadians suffering trauma end up with a peripheral nerve injury and many of them go on to endure lifelong disabilities. Often, doctors take a “wait-and-see” approach to these injuries, postponing surgery to repair the damage until they can determine the severity and whether natural repair processes will ensue.

“The treatment to date is an invasive surgery where you expose the nerve,” says Stratton. “It’s often done three to six months after the injury and in many cases it is only partially effective.” But as researchers better understand the interaction between immune and nerve cells, and what neurochemicals are secreted at what stage of the process, they could develop 'drug cocktails' to be administered just after the injury or with surgery to improve outcomes."

“We need to start thinking about how to pharmacologically modulate the immune cells or mimic their pro-regenerative signals to enhance tissue regeneration,” says Dr. Biernaskie, PhD, associate professor of stem cell biology at UCVM and the Calgary Firefighters Burn Treatment Society Chair in Skin Regeneration and Wound Healing. “But at the same time appreciate that other drugs may negatively influence immune cell function and processes needed for improving regeneration. We have to be careful not to inadvertently disrupt these integral interactions between macrophage and Schwann cells.”

Co-authors on the work include Alexandra Holmes, Nicole Rosin, Sarthak Sinha, Mohit Vohra, Nicole Burma and Dr. Tuan Trang, PhD. The researchers are continuing to study macrophage, Schwann and other cells in the peripheral nervous system — and how they interact with each other — to better understand how to promote regeneration in nerve cells after an injury. The research published in Cell Reports was supported by Alberta Innovates and Alberta Children’s Hospital Research Institute.