Sensory stem cells can prod dying nerves to life: Study

A recent study on mice published in the journal Stem Cell Reports shows that a cluster of nerve cells called dorsal root ganglia (DRG) of the spinal nerve has the ability to regenerate.

The results of this study can be harnessed to restore nerve cells in people with permanent nerve damage, thereby bringing them back to their sensory activity.

“Stem cells in the DRG were already a matter of discussion; we are the first ones to pinpoint the cell type called satellite glia in DRG that has stem cell properties,” says the corresponding author of the study, Dr Beatriz Garcia-Diaz, of Institut du Cerveau – Paris Brain Institute, France.

Stem cells are special cells that can grow into any specific type of cell or tissue, for example, muscle cells or skin cells. They are being explored widely to understand the molecular mechanisms of neurological conditions.

The study paves the way for further research on satellite glia as stem cells for DRG. Some more research is needed to implement the findings in humans.

Loss of touch

The DRG is a bed of sensory neurons found in the peripheral nervous system — a broad road-like pathway with millions of nerves branching out from the brain and spinal cord. These nerves pick up and drop information from the brain to different parts of the body.

The DRG is responsible for helping us to feel touch, pain, heat and cold. Loss of these neurons or damage to them causes a condition called neuropathy, where the individual loses this sense.

Many causes of damage

“Sometimes a traumatic injury from infection, accidents, exposure to toxins, heavy metals like lead and arsenic or diabetes can cause permanent damage to these neurons,” says Dr Soumya Medarametla, consultant neurologist, Anu Institute of Neurosciences, Vijayawada.

She adds that people with neuropathy often complain of numbness, pain, a feeling of `pins and needles and weakness, as Prabhakar K, 50, of Mangaluru, experienced.

Initially, Prabhakar observed unusual swelling and a tingling sensation in his calf muscles and, subsequently, lost sensation under his right foot. His endocrinologist diagnosed him with diabetic neuropathy. His symptoms worsened after he injured his toe at the workplace. Weeks later, he observed that clots had progressed to pus and then to gangrene, leading to the loss of a toe.

Managed but not reversed

Dr Medarametla points out that neuropathy cannot be reversed but managed. “It can be prevented to some extent by removing the toxins or with chemotherapy or some medicines,” she says.

To bridge this gap in neuropathy treatment, the research team of the current study from the International Society for Stem Cell Research looked at ways to regenerate the lost sensory neurons. The initial focus of the study was to find cells in the DRG that could form new neurons.

Studies indicated that DRG carries sensory messages from various parts of the nervous system with the help of supportive cells called satellite glia and Schwann cells, together helping the neurons to function normally.

Exciting discovery

The researchers found that satellite glia contained stem cells that could regenerate and replace sensory neurons in DRG. “The open vision of the spectrum of different cell types interacting in the DRG allowed us to uncover for the first time the exciting stemness capacity of the satellite glial cells,” says Dr Garcia-Diaz.

Once they understand how the satellite glia can form new neurons, the researchers propose to find out how to activate these special cells. They envisage controlling the growth of neurons and increasing the capacity of these cells to regenerate the lost sensory neurons.

“The fact of knowing the cell type responsible for neurogenesis [formation of new neurons] in pathological conditions is crucial to finding new pathways to intervene in cases of nerve injury,” says Dr Garcia-Diaz.

Dr Medarametla agrees that some more promising research in replacing sensory nerves can make a huge difference in the clinical practice of neuropathy.

“We have unveiled the road; now it needs to be walked,” says Dr Garcia-Diaz.