Stem cell therapy in pain medicine

Abstract

Stem cells are attracting attention as a key element in future medicine, satisfying the desire to live a healthier life with the possibility that they can regenerate tissue damaged or degenerated by disease or aging. Stem cells are defined as undifferentiated cells that have the ability to replicate and differentiate themselves into various tissues cells. Stem cells, commonly encountered in clinical or preclinical stages, are largely classified into embryonic, adult, and induced pluripotent stem cells. Recently, stem cell transplantation has been frequently applied to the treatment of pain as an alternative or promising approach for the treatment of severe osteoarthritis, neuropathic pain, and intractable musculoskeletal pain which do not respond to conventional medicine. The main idea of applying stem cells to neuropathic pain is based on the ability of stem cells to release neurotrophic factors, along with providing a cellular source for replacing the injured neural cells, making them ideal candidates for modulating and possibly reversing intractable neuropathic pain. Even though various differentiation capacities of stem cells are reported, there is not enough knowledge and technique to control the differentiation into desired tissues in vivo. Even though the use of stem cells is still in the very early stages of clinical use and raises complicated ethical problems, the future of stem cells therapies is very bright with the help of accumulating evidence and technology.

Keywords: Adult Stem Cells; Aging; Cell Differentiation; Embryonic Stem Cells; Induced Pluripotent Stem Cells; Musculoskeletal Pain; Nerve Growth Factors; Neuralgia; Osteoarthritis.

Fig. 1

Three types of stem cells. After the sperm enters the ovum using the acrosome head to break the zona pellucida, the fertilized egg is called as a zygote before it divides into 16 cells (the morula). The blastocyst formation begins 5 days after fertilization. The blastocyst has 2 types of blastomere cells: the inner cell mass (embryoblast) and trophoblast. The inner cell mass becomes the embryo (till 8 wk), and then the fetus (from 9 wk). The embryonic stem cells are derived from the inner cell mass of the blastocyst. The induced pluripotent stem cells are made from the differentiated somatic cells of the adult, affected by Yamanaka factor. The adult stem cells vary from 1) the hematopoietic stem cells, derived from the umbilical cord of the fetus, 2) the bone marrow mesenchymal stem cells and hematopoietic stem cells, harvested from the bone marrow of an adult, 3) the adipose mesenchymal stem cells, derived from adipose tissue, and 4) the organ mesenchymal stem cells, harvested from the adult body. The embryonic and induced pluripotent stem cells have pluripotent potential; the adult stem cells have multipotent properties. Self-renewal ability, the malignancy rate, and the possibility of ethical problems are increasingly higher in the adult stem cells, induced pluripotent stem cells, and embryonic stem cells, respectively.