Regenerative Effects of Mesenchymal Stem Cells: Contribution of Muse Cells, a Novel Pluripotent Stem Cell Type that Resides in Mesenchymal Cells

Neurosphere formation enhances the neurogenic differentiation potential and migratory ability of umbilical cord-mesenchymal stromal cells

BACKGROUND AIMS

The human umbilical cord (UC) is a rich source of mesenchymal stromal cells (MSCs), which have been reported to have multi-lineage potential. The objectives of this study were to investigate the characteristics and capacity of UC-MSC neurosphere formation and whether this event enhances the propensity of UC-MSCs to undergo neural differentiation.

METHODS

UC-MSCs were collected by the improved explant method. UC-MSCs and neurosphere-forming UC-MSCs (UC-MSC-neurospheres) were induced to undergo neurogenic differentiation, the latter of which were induced by suspension culturing in the presence of epidermal growth factor and basic fibroblast growth factor. The differentiation and migratory capacities of the individual cultures were then compared on the basis of the expression of neural markers, as measured by immunocytochemistry, immunoblotting and quantitative real-time polymerase chain reaction and transwell assays, respectively.

RESULTS

Both UC-MSCs and UC-MSC-neurospheres were capable of differentiating into neurogenic cells when cultured in neurogenic differentiation medium. However, pre-conditioned UC-MSC-neurospheres exhibited significantly higher expression of neural markers--including microtubule-associated protein (MAP2), MUSASHI1, glial fibrillary acidic protein (GFAP), and NESTIN--compared with those derived from UC-MSCs directly. Moreover, UC-MSC-neurospheres expressed significantly higher levels of the stemness markers NANOG, KLF4 and OCT4 than did UC-MSCs. Migration assays also revealed that both UC-MSCs and UC-MSC-neurospheres actively migrate toward glucose-depleted cells.

CONCLUSIONS

Neurogenic differentiation potential probably is greater in UC-MSC-neurospheres than in UC-MSCs. Thus, UC-MSC-neurospheres may serve as a better source of cells for neurogenic regenerative medicine.

Valproic Acid Increases CD133 Positive Cells that Show Low Sensitivity to Cytostatics in Neuroblastoma

Valproic acid (VPA) is a well-known antiepileptic drug that exhibits antitumor activities through its action as a histone deacetylase inhibitor. CD133 is considered to be a cancer stem cell marker in several tumors including neuroblastoma. CD133 transcription is strictly regulated by epigenetic modifications. We evaluated the epigenetic effects of treatment with 1mM VPA and its influence on the expression of CD133 in four human neuroblastoma cell lines. Chemoresistance and cell cycle of CD133+ and CD133- populations were examined by flow cytometry. We performed bisulfite conversion followed by methylation-sensitive high resolution melting analysis to assess the methylation status of CD133 promoters P1 and P3. Our results revealed that VPA induced CD133 expression that was associated with increased acetylation of histones H3 and H4. On treatment with VPA and cytostatics, CD133+ cells were mainly detected in the S and G2/M phases of the cell cycle and they showed less activated caspase-3 compared to CD133- cells. UKF-NB-3 neuroblastoma cells which express CD133 displayed higher colony and neurosphere formation capacities when treated with VPA, unlike IMR-32 which lacks for CD133 protein. Induction of CD133 in UKF-NB-3 was associated with increased expression of phosphorylated Akt and pluripotency transcription factors Nanog, Oct-4 and Sox2. VPA did not induce CD133 expression in cell lines with methylated P1 and P3 promoters, where the CD133 protein was not detected. Applying the demethylating agent 5-aza-2'-deoxycytidine to the cell lines with methylated promoters resulted in CD133 re-expression that was associated with a drop in P1 and P3 methylation level. In conclusion, CD133 expression in neuroblastoma can be regulated by histone acetylation and/or methylation of its CpG promoters. VPA can induce CD133+ cells which display high proliferation potential and low sensitivity to cytostatics in neuroblastoma. These results give new insight into the possible limitations to use VPA in cancer therapy.

Multipotent Mesenchymal Stem Cell Treatment for Discogenic Low Back Pain and Disc Degeneration

Low back pain with resultant loss of function, decreased productivity, and high economic costs is burdensome for both the individual and the society. Evidence suggests that intervertebral disc pathology is a major contributor to spine-related pain and degeneration. When commonly used conservative therapies fail, traditional percutaneous or surgical options may be beneficial for pain relief but are suboptimal because of their inability to alter disc microenvironment catabolism, restore disc tissue, and/or preserve native spine biomechanics. Percutaneously injected Multipotent Mesenchymal Stem Cell (MSC) therapy has recently gained clinical interest for its potential to revolutionarily treat disc-generated (discogenic) pain and associated disc degeneration. Unlike previous therapies to date, MSCs may uniquely offer the ability to improve discogenic pain and provide more sustained improvement by reducing disc microenvironment catabolism and regenerating disc tissue. Consistent treatment success has the potential to create a paradigm shift with regards to the treatment of discogenic pain and disc degeneration.

Porcine lung mesenchymal stromal cells possess differentiation and immunoregulatory properties

Introduction

Mesenchymal stem (stromal) cells (MSCs) possess self-renewal, differentiation and immunoregulatory properties, and therefore are being evaluated as cellular therapy for inflammatory and autoimmune diseases, and for tissue repair. MSCs isolated from bone marrow are extensively studied. Besides bone marrow, MSCs have been identified in almost all organs of the body including the lungs. Lung-derived MSCs may be more effective as therapy for lung diseases as compared to bone marrow-derived MSCs. Pigs are similar to humans in anatomy, physiology and immunological responses, and thus may serve as a useful large animal preclinical model to study potential cellular therapy for human diseases.

Methods

We isolated MSCs from the lungs (L-MSCs) of 4–6-week-old germ-free pigs. We determined the self-renewal, proliferation and differentiation potential of L-MSCs. We also examined the mechanisms of immunoregulation by porcine L-MSCs.

Results

MSCs isolated from porcine lungs showed spindle-shaped morphology and proliferated actively in culture. Porcine L-MSCs expressed mesenchymal markers CD29, CD44, CD90 and CD105 and lacked the expression of hematopoietic markers CD34 and CD45. These cells were multipotent and differentiated into adipocytes, osteocytes and epithelial cells. Like human MSCs, L-MSCs possessed immunoregulatory properties and inhibited proliferation of T cells and interferon-γ and tumor necrosis factor-α production by T cells and dendritic cells, respectively, and increased the production of T-helper 2 cytokines interleukin (IL)-4 and IL-13 by T cells. L-MSCs induced the production of prostaglandin E2 (PGE2) in MSC–T cell co-cultures and inhibition of PGE2 significantly restored (not completely) the immune modulatory effects of L-MSCs.

Conclusions

Here, we demonstrate that MSCs can be isolated from porcine lung and that these cells, similar to human lung MSCs, possess in vitro proliferation, differentiation and immunomodulatory functions. Thus, these cells may serve as a model system to evaluate the contribution of lung MSCs in modulating the immune response, interactions with resident epithelial cells and tissue repair in a pig model of human lung diseases.

Targeted mesenchymal stem cell and vascular endothelial growth factor strategies for repair of nerve defects with nerve tissue implanted autogenous vein graft conduits

Peripheral nerve gaps exceeding 1 cm require a bridging repair strategy. Clinical feasibility of autogenous nerve grafting is limited by donor site comorbidity. In this study we investigated neuroregenerative efficacy of autogenous vein grafts implanted with tissue fragments from distal nerve in combination with vascular endothelial growth factor (VEGF) or mesenchymal stem cells (MSCs) in repair of rat peripheral nerve defects. Six-groups of Sprague-Dawley rats (n = 8 each) were evaluated in the autogenous setting using a 1.6 cm long peroneal nerve defect: Empty vein graft (group 1), Nerve graft (group 2), Vein graft and nerve fragments (group 3), Vein graft and nerve fragments and blank microspheres (group 4), Vein graft and nerve fragments and VEGF microspheres (group 5), Vein graft and nerve fragments and MSCs (group 6). Nerve fragments were derived from distal segment. Walking track analysis, electrophysiology and nerve histomorphometry were performed for assessment. Peroneal function indices (PFI), electrophysiology (amplitude) and axon count results for group 2 were -9.12 ± 3.07, 12.81 ± 2.46 mV, and 1697.88 ± 166.18, whereas the results for group 5 were -9.35 ± 2.55, 12.68 ± 1.78, and 1566 ± 131.44, respectively. The assessment results did not reveal statistical difference between groups 2 and 5 (P > 0.05). The best outcomes were seen in group 2 and 5 followed by group 6. Compared to other groups, poorest outcomes were seen in group 1 (P ≤ 0.05). PFI, electrophysiology (amplitude) and axon count results for group 1 were -208.82 ± 110.69, 0.86 ± 0.52, and 444.50 ± 274.03, respectively. Vein conduits implanted with distal nerve-derived nerve fragments improved axonal regeneration. VEGF was superior to MSCs in facilitating nerve regeneration. © 2015 Wiley Periodicals, Inc. Microsurgery 36:578-585, 2016.

Therapeutic effects of human multilineage-differentiating stress enduring (MUSE) cell transplantation into infarct brain of mice

OBJECTIVE

Bone marrow stromal cells (BMSCs) are heterogeneous and their therapeutic effect is pleiotropic. Multilineage-differentiating stress enduring (Muse) cells are recently identified to comprise several percentages of BMSCs, being able to differentiate into triploblastic lineages including neuronal cells and act as tissue repair cells. This study was aimed to clarify how Muse and non-Muse cells in BMSCs contribute to functional recovery after ischemic stroke.

METHODS

Human BMSCs were separated into stage specific embryonic antigen-3-positive Muse cells and -negative non-Muse cells. Immunodeficient mice were subjected to permanent middle cerebral artery occlusion and received transplantation of vehicle, Muse, non-Muse or BMSCs (2.5×104 cells) into the ipsilateral striatum 7 days later.

RESULTS

Motor function recovery in BMSC and non-Muse groups became apparent at 21 days after transplantation, but reached the plateau thereafter. In Muse group, functional recovery was not observed for up to 28 days post-transplantation, but became apparent at 35 days post-transplantation. On immunohistochemistry, only Muse cells were integrated into peri-infarct cortex and differentiate into Tuj-1- and NeuN-expressing cells, while negligible number of BMSCs and non-Muse cells remained in the peri-infarct area at 42 days post-transplantation.

CONCLUSIONS

These findings strongly suggest that Muse cells and non-Muse cells may contribute differently to tissue regeneration and functional recovery. Muse cells may be more responsible for replacement of the lost neurons through their integration into the peri-infarct cortex and spontaneous differentiation into neuronal marker-positive cells. Non-Muse cells do not remain in the host brain and may exhibit trophic effects rather than cell replacement.

Mesenchymal stem cells as a source of Schwann cells: their anticipated use in peripheral nerve regeneration

Schwann cells form myelin, sustain axons and provide the microenvironment for nerve fibers, thereby playing a key role in the peripheral nervous system (PNS). Schwann cells also provide support for the damaged PNS by producing factors that strongly promote axonal regrowth and contribute to remyelination, which is crucial for the recovery of neural function. These advantages are not confined to the PNS and also apply to the central nervous system. Many diseases, including peripheral nerve injury, neuropathy, multiple sclerosis and spinal cord injury, are targets for Schwann cell therapy. The collection of Schwann cells, however, causes new damage to other peripheral nerve segments. Furthermore, the doubling time of Schwann cells is not very fast, and thus adequate amounts of Schwann cells for clinical use cannot be collected within a reasonable amount of time. Mesenchymal stem cells, which are highly proliferative, are easily accessible from various types of mesenchymal tissues, such as the bone marrow, umbilical cord and fat tissue. Because these cells have the ability to cross oligolineage boundaries between mesodermal to ectodermal lineages, they are capable of differentiating into Schwann cells with step-by-step cytokine stimulation. In this review, we summarize the properties of mesenchymal stem cell-derived Schwann cells, which are comparable to authentic Schwann cells, and discuss future perspectives.

Coenzyme Q10 inhibits the aging of mesenchymal stem cells induced by D-galactose through Akt/mTOR signaling

Increasing evidences indicate that reactive oxygen species are the main factor promoting stem cell aging. Recent studies have demonstrated that coenzyme Q10 (CoQ10) plays a positive role in organ and cellular aging. However, the potential for CoQ10 to protect stem cell aging has not been fully evaluated, and the mechanisms of cell senescence inhibited by CoQ10 are still poorly understood. Our previous study had indicated that D-galactose (D-gal) can remarkably induce mesenchymal stem cell (MSC) aging through promoting intracellular ROS generation. In this study, we showed that CoQ10 could significantly inhibit MSC aging induced by D-gal. Moreover, in the CoQ10 group, the expression of p-Akt and p-mTOR was clearly reduced compared with that in the D-gal group. However, after Akt activating by CA-Akt plasmid, the senescence-cell number in the CoQ10 group was significantly higher than that in the control group. These results indicated that CoQ10 could inhibit D-gal-induced MSC aging through the Akt/mTOR signaling.

Muse cells, newly found non-tumorigenic pluripotent stem cells, reside in human mesenchymal tissues

Mesenchymal stem cells (MSCs) have been presumed to include a subpopulation of pluripotent-like cells as they differentiate not only into the same mesodermal-lineage cells but also into ectodermal- and endodermal-lineage cells and exert tissue regenerative effects in a wide variety of tissues. A novel type of pluripotent stem cell, Multilineage-differentiating stress enduring (Muse) cells, was recently discovered in mesenchymal tissues such as the bone marrow, adipose tissue, dermis and connective tissue of organs, as well as in cultured fibroblasts and bone marrow-MSCs. Muse cells are able to differentiate into all three germ layers from a single cell and to self-renew, and yet exhibit non-tumorigenic and low telomerase activities. They can migrate to and target damaged sites in vivo, spontaneously differentiate into cells compatible with the targeted tissue, and contribute to tissue repair. Thus, Muse cells may account for the wide variety of differentiation abilities and tissue repair effects that have been observed in MSCs. Muse cells are unique in that they are pluripotent stem cells that belong in the living body, and are thus assumed to play an important role in 'regenerative homeostasis' in vivo.

Are hematopoietic stem cells involved in hepatocarcinogenesis?

THE LIVER HAS THREE CELL LINEAGES ABLE TO PROLIFERATE AFTER A HEPATIC INJURY: the mature hepatocyte, the ductular "bipolar" progenitor cell termed "oval cell" and the putative periductular stem cell. Hepatocytes can only produce other hepatocytes whereas ductular progenitor cells are considerate bipolar since they can give rise to biliary cells or hepatocytes. Periductular stem cells are rare in the liver, have a very long proliferation potential and may be multipotent, being this aspect still under investigation. They originate in the bone marrow since their progeny express genetic markers of donor hematopoietic cells after bone marrow transplantation. Since the liver is the hematopoietic organ of the fetus, it is possible that hematopoietic stem cells may reside in the liver of the adult. This assumption is proved by the finding that oval cells express hematopoietic markers like CD34, CD45, CD 109, Thy-1, c-kit, and others, which are also expressed by bone marrow-derived hematopoietic stem cells (BMSCs). Few and discordant studies have evaluated the role of BMSC in hepatocarcinogenesis so far and further studies in vitro and in vivo are warranted in order to definitively clarify such an issue.

Therapeutic Implications of Newly Identified Stem Cell Populations From the Skin Dermis

Skin, the largest organ of the body, is a promising reservoir for adult stem cells. The epidermal stem cells and hair follicle stem cells have been well studied for their important roles in homeostasis, regeneration, and repair of the epidermis and appendages for decades. However, stem cells residing in dermis were not identified until the year 2001, when a variety of stem cell subpopulations have been isolated and identified from the dermis of mammalian skin such as neural crest stem cells, mesenchymal stem cell-like dermal stem cells, and dermal hematopoietic cells. These stem cell subpopulations exhibited capabilities of self-renewing, multipotent differentiating, and immunosuppressive properties. Hence, the dermis-derived stem cells showed extensive potential applications in regenerative medicine, especially for wound healing/tissue repair, neural repair, and hematopoietic recovery. Here we summarized current research on the stem cell subpopulations derived from the dermis and aimed to provide a comprehensive review on their isolation, specific markers, differentiation capacity, and the functional activities in homeostasis, regeneration, and tissue repair.