Transplantation of Unique Subpopulation of Fibroblasts, Muse Cells, Ameliorates Experimental Stroke Possibly via Robust Neuronal Differentiation

Abstract

Objective: Muse cells reside as pre-existing pluripotent-like stem cells within the fibroblasts, are nontumorigenic, exhibit differentiation capacity into triploblastic-lineage cells, and replenish lost cells when transplanted in injury models. Cell fate and function of human skin fibroblast-derived Muse cells were evaluated in a rat stroke model. Methods: Muse cells (30,000), collected by pluripotent surface marker stage-specific embryonic antigen-3, were injected stereotaxically into three deposits within the rat ischemic cortex at 2 days after transient middle cerebral artery occlusion, and the cells' biological effects were examined for more than 84 days. Results: Muse cells spontaneously and promptly committed to neural/ neuronal-lineage cells when cocultured with stroke brain slices. Muse-transplanted stroke rats exhibited significant improvements in neurological and motor functions compared to control groups at chronic days 70 and 84, without a reduction in the infarct size. Muse cells survived in the host brain for up to 84 days and differentiated into NeuN (~65%), MAP-2 (~32%), calbindin (~28%), and GST-p (~25%)-positive cells in the cortex, but glial fibrillary acidic proteinpositive cells were rare. Tumor formation was not observed. Muse cells integrated into the sensory-motor cortex, extended their neurites into cervical spinal cord, and displayed normalized hind limb somatosensory evoked potentials. Interpretation: Muse cells are unique from other stem cells in that they differentiate with high ratio into neuronal cells after integration with host brain microenvironment, possibly reconstructing the neuronal circuit to mitigate stroke symptoms. Human fibroblast-derived Muse cells pose as a novel source of transplantable stem cells, circumventing the need for gene manipulations, especially when contemplating autologous cell therapy for stroke. STEM CELLS 2016;34:160-173 SIGNIFICANCE STATEMENTHuman dermal fibroblast-derived Muse cells have practical advantages for regenerative medicine; they are non-tumorigenic, easily accessed both commercially and from skin biopsies of patients, and can be easily collected as SSEA-3(1) cells either by FACS or magnetic-activated cell sorting. Most importantly, Muse cells do not need to be induced to attain stemness and to commit into specific lineages prior to transplantation, because they already display inherent stem cell properties upon isolation, and after transplantation spontaneously home into the damaged site and differentiate into cells compatible with the target tissue, rendering the need for gene manipulation and intricate cell induction protocols unnecessary. As we envision an autologous stem cell product in the clinic, Muse cells will simply involve a two-step process, namely routine collection from fibroblasts and immediate transplantation to the patient. Finally, with the present functional outcomes achieved with only 30,000 Muse cells, such low effective cell dose indicates excellent therapeutic potency of Muse cells compared to general MSC ...

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“…Studies have shown that MAP-2 expression was significantly increased during nerve injury, which represented reconstruction of dendritic structure to improve neurological function (Lin et al, 2015;Shafit-Zagardo et al, 2000;Uchida et al, 2015). MAP-2 is an important structural and functional protein found in the neuron bodies and dendrites for maintaining microtubule stability and nerve regeneration (Mohan and John, 2015).…”

The secretome of MUSE cells contains factors that may play a role in regulation of stemness, apoptosis and immunomodulation

“…11 In stroke model, they spontaneously differentiated into neuronal cells and participated in reconstruction of pyramidal tract, and in hepatectomy model, intravenously injected Muse cells differentiated into liver components after homing. 12,13 Since na€ ıve Muse cells were used in all these studies, Muse cells do not need to be induced into purposive cells prior to transplantation, unlike embryonic stem (ES) and induced pluripotent stem (iPS) cells. These unique performances are expected to be useful for regenerative medicine, while other functional aspect of Muse cells remains to be clarified.…”

Recent Advances in Stem Cell-Based Therapeutics for Stroke

“…Because of the adult tissue origin and the resemblance with many of the stem cell phenotypic features, bone marrow-derived stem cells have emerged as leading transplantable cell type for CNS disorders, including stroke [25]. Specialized subsets or populations, as well as engineered stem/progenitor cells, have been derived from the bone marrow, including mesenchymal stem or stromal cells (MSCs), endothelial progenitor cells (EPCs), SB623, multipotent adult progenitor cells (MAPCs), Multilineage-differentiating stress-enduring (Muse), among many others [26–30]. Among these bone marrow-derived cells, MSCs have been extensively studied in stroke animal models.…”