Recent achievements in stem cell-mediated myelin repair. Curr Opin Neurol. 2016;29:205-212. [PMID: 27035898 DOI: 10.1097/WCO.0000000000000323]

Mechanisms and repair strategies for white matter degeneration in CNS injury and diseases

White matter degeneration is an important pathophysiological event of the central nervous system that is collectively characterized by demyelination, oligodendrocyte loss, axonal degeneration and parenchymal changes that can result in sensory, motor, autonomic and cognitive impairments. White matter degeneration can occur due to a variety of causes including trauma, neurotoxic exposure, insufficient blood flow, neuroinflammation, and developmental and inherited neuropathies. Regardless of the etiology, the degeneration processes share similar pathologic features. In recent years, a plethora of cellular and molecular mechanisms have been identified for axon and oligodendrocyte degeneration including oxidative damage, calcium overload, neuroinflammatory events, activation of proteases, depletion of adenosine triphosphate and energy supply. Extensive efforts have been also made to develop neuroprotective and neuroregenerative approaches for white matter repair. However, less progress has been achieved in this area mainly due to the complexity and multifactorial nature of the degeneration processes. Here, we will provide a timely review on the current understanding of the cellular and molecular mechanisms of white matter degeneration and will also discuss recent pharmacological and cellular therapeutic approaches for white matter protection as well as axonal regeneration, oligodendrogenesis and remyelination.

Human mesenchymal factors induce rat hippocampal- and human neural stem cell dependent oligodendrogenesis

The generation of new oligodendrocytes is essential for adult brain repair in diseases such as multiple sclerosis. We previously identified the multifunctional p57kip2 protein as a negative regulator of myelinating glial cell differentiation and as an intrinsic switch of glial fate decision in adult neural stem cells (aNSCs). In oligodendroglial precursor cells (OPCs), p57kip2 protein nuclear exclusion was recently found to be rate limiting for differentiation to proceed. Furthermore, stimulation with mesenchymal stem cell (MSC)-derived factors enhanced oligodendrogenesis by yet unknown mechanisms. To elucidate this instructive interaction, we investigated to what degree MSC secreted factors are species dependent, whether hippocampal aNSCs respond equally well to such stimuli, whether apart from oligodendroglial differentiation also tissue integration and axonal wrapping can be promoted and whether the oligodendrogenic effect involved subcellular translocation of p57kip2. We found that CC1 positive oligodendrocytes within the hilus express nuclear p57kip2 protein and that MSC dependent stimulation of cultured hippocampal aNSCs was not accompanied by nuclear p57kip2 exclusion as observed for parenchymal OPCs after spontaneous differentiation. Stimulation with human MSC factors was observed to equally promote rat stem cell oligodendrogenesis, axonal wrapping and tissue integration. As forced nuclear shuttling of p57kip2 led to decreased CNPase- but elevated GFAP expression levels, this indicates heterogenic oligodendroglial mechanisms occurring between OPCs and aNSCs. We also show for the first time that dominant pro-oligodendroglial factors derived from human fetal MSCs can instruct human induced pluripotent stem cell-derived NSCs to differentiate into O4 positive oligodendrocytes.

Neuronally differentiated adipose-derived stem cells and aligned PHBV nanofiber nerve scaffolds promote sciatic nerve regeneration

Through a combination of biomaterials and stem cells, tissue engineering strategies for restoring and regenerating damaged peripheral nerves have recently been used to meet the challenges posed by nerve injury. In a previous study, we revealed a new way to induce neuronal differentiation of stem cells based on the temporally sequential use of miR-218 and Fibroblast Growth Factor 2 (FGF2) in vitro (FGF2-miR-218 induction approach). In the present study, we sought to investigate the application of this novel approach in repairing sciatic nerve damage in vivo. The results showed that compared with randomly oriented nanofibers, nanofibers in an aligned orientation more favored stem cell growth and elongation. Stem cells (neuronally differentiated adipose-derived mesenchymal stem cells (ASCs)) treated with the FGF2-miR-218 induction approach and integrated with 3D aligned orientation nanofibers structures as artificial nerve grafts were implanted into 10 mm transected rat sciatic nerves in vivo. The test results of immunohistochemical staining and motor function restoration indicated that the FGF2-miR-218 induction approach combined with the 3D nanofiber scaffolds facilitated the nerve regeneration. Thus, this approach could be an effective tissue engineering method for recovery of nerve damage.

Taking Advantage of Nature's Gift: Can Endogenous Neural Stem Cells Improve Myelin Regeneration?

Irreversible functional deficits in multiple sclerosis (MS) are directly correlated to axonal damage and loss. Neurodegeneration results from immune-mediated destruction of myelin sheaths and subsequent axonal demyelination. Importantly, oligodendrocytes, the myelinating glial cells of the central nervous system, can be replaced to some extent to generate new myelin sheaths. This endogenous regeneration capacity has so far mainly been attributed to the activation and recruitment of resident oligodendroglial precursor cells. As this self-repair process is limited and increasingly fails while MS progresses, much interest has evolved regarding the development of remyelination-promoting strategies and the presence of alternative cell types, which can also contribute to the restoration of myelin sheaths. The adult brain comprises at least two neurogenic niches harboring life-long adult neural stem cells (NSCs). An increasing number of investigations are beginning to shed light on these cells under pathological conditions and revealed a significant potential of NSCs to contribute to myelin repair activities. In this review, these emerging investigations are discussed with respect to the importance of stimulating endogenous repair mechanisms from germinal sources. Moreover, we present key findings of NSC-derived oligodendroglial progeny, including a comprehensive overview of factors and mechanisms involved in this process.

Bone marrow mesenchymal stem cells for treatment of pancreatic diseases: Research status and prospects

The incidence of pancreatic diseases is increasing year by year. Current treatments for pancreatic diseases are mainly symptomatic, and the research on the repair and restoration of function of the pancreatic cells progresses slowly. Stem cells have been widely used in the treatment of diseases in recent years because of their ability of multi-directional differentiation and repair of cell damage caused by disease and injury. Numerous studies confirm that pancreatic stem cells after transplantation can differentiate into pancreatic cells and play an important role in the recovery of external secretory function and repair of the damaged pancreatic cells. Particularly, both in vivo and in vitro studies show that bone marrow mesenchymal stem cells have achieved remarkable results in the treatment of pancreatic diseases, laying a theoretical and practical basis for clinical treatment of pancreatic diseases with stem cells. This article outlines the progress in treatment of acute pancreatitis, chronic pancreatitis and pancreatic cancer with bone marrow mesenchymal stem cells, demonstrating that stem cells are expected to become one of new methods for the treatment of pancreatic diseases.