Peripheral nerve injury has become an increasingly prevalent clinical concern, causing great morbidity in the community. Although there have been significant advancements in the treatment of peripheral nerve damage in recent years, the issue of long-term nerve regeneration remains. Furthermore, Wallerian degeneration has created an obstacle to long-term nerve regeneration. For this reason, there has been extensive research on the use of exogenous and endogenous stem cells as an adjunct or even primary treatment option for peripheral nerve injury. The plasticity and inducibility of stem cells make them an enticing option for initiating neuronal cell regrowth and optimal sensory and functional nerve regeneration. Peripheral nerve injury has a broad range of causative factors and etiologies. As such, unique stem cell-induced peripheral nerve treatments are being investigated to ameliorate the damage incited by all causes, including trauma, neuropathy, and systemic neurodegenerative diseases. This review is oriented to outline the potential role of stem cell therapies in peripheral nerve injury versus the current standards of care, compare the benefits and drawbacks of specific stem cell lines under investigation, and highlight the current models of stem cell therapy in the peripheral nervous system, with the ultimate goal of narrowing down and optimizing the role and scope of stem cell therapy in peripheral nerve injury.

This review demonstrates current literature on pineal gland physiology, pathology, and animal model experiments to concisely explore future needs in research development with respect to pineal gland function and neuro-regenerative properties. The pineal gland plays an integral role in sleep and recovery by promoting physiologic circadian rhythms via production and release of melatonin. Yet, the current literature shows that the pineal gland has neuroprotective effects that modulate both peripheral and central nerve injuries through several direct and indirect mechanisms, such as angiogenesis and induction of growth factors and anti-inflammatory mediators. Animal models have also shown correlations between pineal gland function and metabolic homeostasis. Studies have shown that a functional pineal gland is essential in preventing and slowing the progression of certain diseases such as diabetes, osteoporosis, vertebral osteoarthritis, and neurodegenerative processes. Lastly, the array of cell culturing methods and animal models that can be used to further develop the study of pineal gland function and nervous system injury were reviewed.