From: Crosstalk between stem cell and spinal cord injury: pathophysiology and treatment strategies
 | Description | Possible therapeutic effects in SCI | Advantages | Current limitation |
---|---|---|---|---|
Mesenchymal stem cell | Mesodermal lineage multipotent progenitors can be obtained from bone marrow, umbilical cord, amnion, placenta, and fat tissue [13]. | Secreting anti-inflammatory factors, cytokines, growth factors, and cell adhesion factors to improve the microenvironment of the lesion and further promotes self-repair after SCI; immunomodulatory, neurotrophic and anti-apoptotic effects [13, 14]. | High multilineage differentiation, easily isolated and grafted, suitable for different stages of SCI, raising no ethical concern, limited risk of developing tumors, minimal immunoreactivity [15, 16]. | Mechanism requires further research which limits the efficiency of treatment; results of clinical trials are still far from obtaining functional recovery and restoring neural circuits; effective way to deliver cells still needs further research [16]. |
Embryonic stem cells | Highly undifferentiated cells that are pluripotent and can differentiate into different tissue cells [17]. | Differentiated neurons and glial cells are used to supplement cell defects caused by SCI; secrete active factors to inhibit further damage, support nerve tissue regeneration [18,19,20,21,22,23]. | Long history of research, proven to have a certain effect in a variety of diseases; pluripotent cells that can differentiate into all tissue cells [17, 18]. | Immune rejection and the risk of tumor formation; ethical issues needed to be solved [24,25,26]. |
Neural stem cells | Stem cells located in the lateral ventricle of the brain, the dentate gyrus of the hippocampus, and the central canal of the spinal cord [27]. | Modulation of the formation of glial scar, enhancing oligodendrocyte differentiation and neuronal differentiation; replace necrotic damaged cells and reconstruct local loops which in turn promotes the recovery of body function; secrete growth-promoting factors to promote the survival and growth of damaged neurons; immunomodulatory effects [28,29,30,31,32]. | A reducing tumorigenicity due to the maturation is restricted to glial and neuronal subtypes; can be harvested from either adult or fetal spinal cord tissue [33, 34]. | Further studies are necessary to confirm neurological and functional benefits, safety, adjusting doses and administrations periods as well as the most promising cellular sources to obtain NSCs [34]. |
Induced pluripotent stem cells | Considered to be effective alternative cell sources for ESCs. | Induced to be neural progenitor cells, neurons, oligodendrocytes, and astrocytes; promote remyelination, axonal regeneration and the secretion of neurotrophic factors; reducing inflammation [35]. | Self-renew and differentiate into various types of neural cells; Free of ethical issues associated with some transplant sources and importantly can be performed in an autologous manner removing the need for immune suppression [36]. | High risk of immune rejection and tumorigenesis: teratoma and true tumors [13, 36]. |
Spermatogonial stem cells | A subtype of spermatogonia [37]. | Have the potential to differentiate into various cells nervous system including functional GABAergic neurons, glutamatergic neurons, serotonergic neurons, and glial cells [38, 39]. | Multidifferentiation potential; self-replication and self-renewal abilities; able to differentiate into functional dopaminergic neurons directly without an intermediate transition process of ESCs or NSCs; pass the genetic material to the offspring; can be produced throughout the lifetime and lacking of ethical problems, tumorigenicity and immune rejection [37, 40,41,42,43]. | Multi-differentiation potential is susceptible to environmental influences; SSC treatment of nervous system diseases is exclusively designed to substitute for differentiation at present, and no reports of secretion of various factors by these cells have been found [42]. |
Adult endogenous stem cells | Stem cells located in the adult nervous system [27]. | Activate and proliferate to produce glial cells when spinal cord is injured; differentiate into astrocytes and oligodendrocytes [27, 44, 45]. | Noninvasive cell therapy that directly activated to function without the need for traumatic cell transplantation. | Ability to differentiate into neurons is limited [46]. |