Know how hair follicle stem cells can be used into nerve regeneration

Nerve Regeneration

Nerves

The human nervous system is composed of a central nervous system (CNS) comprising brain and spinal cord and the peripheral nervous system (PNS). The brain controls the effector cells, which carry out the physiological responses requested by the brain, and nerves which carry the messages back and forth. Thus, the nervous system is a "wired" communication system of the body.

Nerves are basically composed of axons, a long, slender projection of a nerve cell, or neuron, that carries electrical impulses from it. Nerves are the connecting ‘wires’ which interconnect different parts of central nervous system. The disruption in this network because of nerve damage can be likened to cutting an electrical cord connecting a lamp to an outlet, meaning the signal between the cell body and effector cells is interrupted, and neurons are unable to convey effective requests such as a muscle movement resulting in paralysis.

Nerve regeneration

Severe nerve damage is currently incurable as part of the neuron downstream of the injury dies off and this neuron cannot be replaced. Grafting, which works well for skin tissue damage, doesn’t work in the case of nerves because of loss of nerve function where the donor tissue is removed and the difficulty in reconnecting the nerve cells.

Though there is no cure for nerve damage, some medicines such as methylprednisolone and Sygen are used to limit secondary damage and reduce the loss of nerve function to limited effects. However, it seems that this is the most that can be done for nerve damage using drugs.

It is biotechnology which seems to hold the future for successful nerve regeneration. Scientists are trying to regenerate nerves in vivo through following methods:
  • Guidance Channels
  • Stem Cells
  • Growth Factors
  • Gene Therapy

The scope of this article is limited to discussing stem cells for nerve regeneration.

Stem cells for nerve regeneration

Stem cells display a high level of plasticity, their main reason to be used in nerve regeneration. By plasticity we mean that these cells can be programmed to different tissue functions irrespective of their origin. This property of stem cells means that it would be possible to take any stem cell from a patient and influence that cell in specific ways to get nerve function. After injecting these manipulated stem cells into patient’s body, the cell could migrate to the location of the injury and immediately function as nerve cells. In fact, experiments have shown stem cells to be even more flexible than expected. In mouse models, nerve stem cells have even produced blood cells after putting them into the bone marrow.

Hair follicle cells for nerve regeneration

Hair growth is a unique, cyclic regeneration phenomenon and the throughout the life of mammals.

The hair follicle bulge area is a rich source of actively growing, pluripotent adult stem cells. These cells can be put through a culture, molded and reprogrammed into neurons, glia, keratinocytes, smooth muscle cells, and melanocytes in vitro. With the hair follicle undergoing repeated cycles of periods of growth (anagen), regression (catagen), and rest (telogen), the follicle bulge region contains cells that are, by several criteria, true stem cells.

During the anagen phase of the hair growth cycle, the bulge stem cells periodically differentiate into all of the follicle cell types including the outer-root sheath, hair matrix cells, and inner-root sheath as well as sebaceous-gland basal cells, and epidermis.

Scientists in their studies have found that in response to wounding, some cells exit the follicle, migrate and proliferate to repopulate the infundibulum and epidermis. Multipotent adult stem cells isolated from mammalian skin dermis, termed skin-derived precursors, can proliferate and differentiate in culture to produce neurons, glia, smooth muscle cells, and adipocytes. However, the exact location of the skin-derived precursors was not identified.

In vivo studies show the nestin-driven GFP hair follicle stem cells can differentiate into blood vessels and neural tissue after transplantation to the subcutis of mice.

Equivalent hair follicle stem cells derived from transgenic mice with beta-actin-driven GFP implanted into the gap region of a severed sciatic nerve greatly enhanced the rate of nerve regeneration and the restoration of nerve function. The follicle cells transdifferentiated largely into Schwann cells, which are known to support neuron regrowth.

These results suggest that hair follicle stem cells provide an important, accessible, autologous source of adult stem cells for regenerative medicine. On day, it may be possible to take stem cells from the hair follicle of a person. Culture the cells and transform them into nerve cells, and then inject the cells into damaged nerves to regenerate them. Such an approach may be a long way into the future, but the first studies to prove this is possible have been done.