Variations of Clonal Marrow Stem Cell Lines Established from Human Bone Marrow in Surface Epitopes, Differentiation Potential, Gene Expression, and Cytokine Secretion

Proteomic profiling of mesenchymal stem cell-derived extracellular vesicles: Impact of isolation methods on protein cargo

Extracellular vesicles (EVs) are nanosized vesicles with a lipid bilayer that are secreted by cells and play a critical role in cell-to-cell communication. Despite the promising reports regarding their diagnostic and therapeutic potential, the utilization of EVs in the clinical setting is limited due to insufficient information about their cargo and a lack of standardization in isolation and analysis methods. Considering protein cargos in EVs as key contributors to their therapeutic potency, we conducted a tandem mass tag (TMT) quantitative proteomics analysis of three subpopulations of mesenchymal stem cell (MSC)-derived EVs obtained through three different isolation techniques: ultracentrifugation (UC), high-speed centrifugation (HS), and ultracentrifugation on sucrose cushion (SU). Subsequently, we checked EV marker expression, size distribution, and morphological characterization, followed by bioinformatic analysis. The bioinformatic analysis of the proteome results revealed that these subpopulations exhibit distinct molecular and functional characteristics. The choice of isolation method impacts the proteome of isolated EVs by isolating different subpopulations of EVs. Specifically, EVs isolated through the high-speed centrifugation (HS) method exhibited a higher abundance of ribosomal and mitochondrial proteins. Functional apoptosis assays comparing isolated mitochondria with EVs isolated through different methods revealed that HS-EVs, but not other EVs, induced early apoptosis in cancer cells. On the other hand, EVs isolated using the sucrose cushion (SU) and ultracentrifugation (UC) methods demonstrated a higher abundance of proteins primarily involved in the immune response, cell-cell interactions and extracellular matrix interactions. Our analyses unveil notable disparities in proteins and associated biological functions among EV subpopulations, underscoring the importance of meticulously selecting isolation methods and resultant EV subpopulations based on the intended application.

Homogenous subpopulation of human mesenchymal stem cells and their extracellular vesicles restore function of endometrium in an experimental rat model of Asherman syndrome

BACKGROUND

Asherman syndrome (AS), or intrauterine adhesions, is a main cause of infertility in reproductive age women after endometrial injury. Mesenchymal stem cells (MSCs) and their extracellular vesicles (EVs) are promising candidates for therapies that repair damaged endometria. However, concerns about their efficacy are attributed to heterogeneity of the cell populations and EVs. A homogenous population of MSCs and effective EV subpopulation are needed to develop potentially promising therapeutic options in regenerative medicine.

METHODS

AS model was induced by mechanical injury in adult rat uteri. Then, the animals were treated immediately with homogeneous population of human bone marrow-derived clonal MSCs (cMSCs), heterogenous parental MSCs (hMSCs), or cMSCs-derived EV subpopulations (EV20K and EV110K). The animals were sacrificed two weeks post-treatment and uterine horns were collected. The sections were taken, and hematoxylin-eosin was used to examine the repair of endometrial structure. Fibrosis was measured by Masson's trichrome staining and α-SMA and cell proliferation by Ki67 immunostaining. The function of the uteri was explored by the result of mating trial test. Expression changes of TNFα, IL-10, VEGF, and LIF were assayed by ELISA.

RESULTS

Histological analysis indicated fewer glands, thinner endometria, increased fibrotic areas, and decreased proliferation of epithelial and stroma of the uteri in the treated compared with intact and sham-operated animals. However, these parameters improved after transplantation of both types of cMSCs and hMSCs and/or both cryopreserved EVs subpopulations. The cMSCs demonstrated more successful implantation of the embryos in comparison with hMSCs. The tracing of the transplanted cMSCs and EVs showed that they migrated and localized in the uteri. Protein expression analysis results demonstrated downregulation of proinflammatory factor TNFα and upregulation of anti-inflammatory cytokine IL-10, and endometrial receptivity cytokines VEGF and LIF in cMSC- and EV20K-treated animals.

CONCLUSION

Transplantation of MSCs and EVs contributed to endometrial repair and restoration of reproductive function, likely by inhibition of excessive fibrosis and inflammation, enhancement of endometrial cell proliferation, and regulation of molecular markers related to endometrial receptivity. Compared to classical hMSCs, cMSCs were more efficient than hMSCs in restoration of reproductive function. Moreover, EV20K is more cost-effective and feasible for prevention of AS in comparison with conventional EVs (EV110K).

Rapid and effective preparation of clonal bone marrow-derived mesenchymal stem/stromal cell sheets to reduce renal fibrosis

Allogeneic "off-the-shelf" mesenchymal stem/stromal cell (MSC) therapy requires scalable, quality-controlled cell manufacturing and distribution systems to provide clinical-grade products using cryogenic cell banking. However, previous studies report impaired cell function associated with administering freeze-thawed MSCs as single cell suspensions, potentially compromising reliable therapeutic efficacy. Using long-term culture-adapted clinical-grade clonal human bone marrow MSCs (cBMSCs) in this study, we engineered cBMSC sheets in 24 h to provide rapid preparation. We then sought to determine the influence of cBMSC freeze-thawing on both in vitro production of pro-regenerative factors and in vivo ability to reduce renal fibrosis in a rat model compared to freshly harvested cBMSCs. Sheets from freeze-thawed cBMSCs sheets exhibited comparable in vitro protein production and gene expression of pro-regenerative factors [e.g., hepatocyte growth factor (HGF), vascular endothelial growth factor (VEGF), and interleukin 10 (IL-10)] to freshly harvested cBMSC sheets. Additionally, freeze-thawed cBMSC sheets successfully suppressed renal fibrosis in vivo in an established rat ischemia-reperfusion injury model. Despite previous studies reporting that freeze-thawed MSCs exhibit impaired cell functions compared to fresh MSC single cell suspensions, cell sheets engineered from freeze-thawed cBMSCs do not exhibit impaired cell functions, supporting critical steps toward future clinical translation of cBMSC-based kidney disease treatment.

Clinically Relevant Mesenchymal Stem/Stromal Cell Sheet Transplantation Method for Kidney Disease

Chronic kidney disease (CKD) is the irreversible loss of nephron function, leading to a build-up of toxins, prolonged inflammation, and ultimately fibrosis. Currently, no effective therapies exist to treat CKD due to its complex pathophysiology. Mesenchymal stem/stromal cell (MSC) transplantation is a promising strategy to treat kidney diseases, and multiple clinical trials are currently ongoing. We previously demonstrated that rat bone marrow-derived MSC (BMSC) sheets transplanted onto surgically decapsulated kidney exert therapeutic effects that suppressed renal fibrosis progression based on enhanced vascularization. However, there are clinical concerns about kidney decapsulation such as impaired glomerular filtration rate and Na⁺ ion and H₂O excretion, leading to kidney dysfunction. Therefore, for transitioning from basic research to translational research using cell sheet therapy for kidney disease, it is essential to develop a new cell sheet transplantation strategy without kidney decapsulation. Significantly, we employed cell sheets engineered from clinical-grade human clonal BMSC (cBMSC) and transplanted these onto intact renal capsule to evaluate their therapeutic ability in the rat ischemia-reperfusion injury (IRI) model. Histological analysis 1-day postsurgery showed that cBMSC sheets engrafted well onto intact renal capsule. Interestingly, some grafted cBMSCs migrated into the renal parenchyma. At 1-3 days postsurgery (acute stage), grafted cBMSC sheets prevented tubular epithelial cell injury. At 28 days postsurgery (chronic phase), we observed that grafted cBMSC sheets suppressed renal fibrosis in the rat IRI model. Taken together, engineered cBMSC sheet transplantation onto intact renal capsule suppresses tubular epithelial cell injury and renal fibrosis, supporting further development as a possible clinically relevant strategy. Impact statement Chronic kidney disease (CKD) produces irreversible loss of nephron function, leading to toxemia, prolonged inflammation, and ultimately kidney fibrosis. Currently, no therapies exist to effectively treat CKD due to its complex pathophysiology. Mesenchymal stem/stromal cells (MSCs) are widely known to secret therapeutic paracrine factors, which is expected to provide a new effective therapy for unmet medical needs. However, unsatisfied MSC quality and administration methods to patients limit their therapeutic effects. In this study, we engineered clonal bone marrow-derived MSC sheets and established clinically relevant cell sheet transplantation strategy to treat renal fibrosis, which would improve MSC treatment for kidney disease.

Three-Dimensional Culture of Equine Bone Marrow-Derived Mesenchymal Stem Cells Enhances Anti-Inflammatory Properties in a Donor-Dependent Manner

Three-dimensional (3D) culture of human mesenchymal stem cells (MSCs) as spheroids enhances the production of important regulators of inflammation: prostaglandin E2 (PGE₂), interleukin (IL)-6, and tumor necrosis factor-inducible gene 6 (TSG-6). The horse is a model species and suffers from musculoskeletal, ocular, and systemic inflammatory disease. It is unknown if 3D culture promotes enhanced production of immunomodulatory cytokines and regulators in equine MSCs and if there is variation between individual cell donors. We evaluated the feasibility, cell viability, and stem cell marker stability of 3D-cultured equine bone marrow-derived MSCs (eBMSCs) and determined the effect of inflammatory stimulation upon gene expression and secretion of key regulators of inflammation [PGE₂, TSG-6, IL-10, IL-6, stromal cell-derived factor 1 (SDF-1)]. Variations in anti-inflammatory phenotype between six donors were investigated, with and without IL-1β stimulation, in either monolayer [two-dimensional (2D)] or 3D culture. Our results showed that eBMSCs self-aggregate in 3D culture while maintaining cell viability and markers of stemness CD90, CD44, CD104, and Oct4. In addition, 3D culture enhances the anti-inflammatory phenotype regardless of inflammatory stimulation by increasing PGE₂, IL-6, TSG-6, SDF-1, and IL-10. Finally, anti-inflammatory phenotype was enhanced by IL-1β exposure but showed significant variation between cell lines in the degree of gene upregulation, and what genes were expressed. We conclude that 3D culture of eBMSCs as spheroids alters their anti-inflammatory phenotype, but this effect is influenced by cytokine exposure and cell donor.

Standard toxicity study of clinical-grade allogeneic human bone marrow-derived clonal mesenchymal stromal cells

INTRODUCTION

Mesenchymal stromal cells (MSCs) have opened a new window to treat inflammatory and non-inflammatory diseases. Nonetheless, their clinical applications require rigorous control and monitoring procedures to ensure full compliance with the principles of good manufacturing practice (GMP). Various evaluations should be passed in conjunction with the development of these newly emerging therapeutic products from bench-to-bedside. These evaluations include in vitro characterization, preclinical studies, and clinical trials to ensure product safety and efficacy. Therefore, a robust and well-designed preclinical study is critical to confirm product safety. This study aims to determine the probable toxicity effects of local and systemic injections of cryopreserved human bone marrow-derived clonal MSCs (BM-cMSCs) during subacute and subchronic periods of time.

METHODS

BM-cMSCs were characterized according to the International Society for Cell and Gene Therapy (ISCT) criteria for MSCs. Both safety and toxicity of the BM-cMSCs population produced under GMP-compatible conditions were assessed in both sexes of Sprague Dawley (SD) rats via systemic intravenous (IV) administration and local injection in intervertebral disc (IVD). Behavioral changes, clinical signs of toxicity, and changes in body weight, water and food consumption were the important variables for product toxicity testing over 14 consecutive days during the subacute period and 90 consecutive days during the subchronic period. At the end of the assessment periods, the rats were killed for histopathology analysis of the target tissues. The BM-cMSCs potential for tumorigenicity was checked in nude mice.

RESULTS

Single IV and IVD injections of BM-cMSCs did not cause significant signs of clinical toxicity, or changes in laboratory and histopathology data during the subacute (14 day) and subchronic (90 day) periods. Ex vivo-expanded and cryopreserved BM-cMSCs did not induce tumor formation in nude mice.

CONCLUSION

The results suggest that local and systemic administrations of xenogeneic BM-cMSCs in both sexes of SD rats do not cause toxicity during the subacute and subchronic periods of time. Also, BM-cMSCs were non-tumorigenic in nude mice.

A Roadmap for the Production of a GMP-Compatible Cell Bank of Allogeneic Bone Marrow-Derived Clonal Mesenchymal Stromal Cells for Cell Therapy Applications

Background

Allogeneic mesenchymal stromal cells (MSCs) have been used extensively in various clinical trials. Nevertheless, there are concerns about their efficacy, attributed mainly to the heterogeneity of the applied populations. Therefore, producing a consistent population of MSCs is crucial to improve their therapeutic efficacy. This study presents a good manufacturing practice (GMP)-compatible and cost-effective protocol for manufacturing, banking, and lot-release of a homogeneous population of human bone marrow-derived clonal MSCs (cMSCs).

Methods

Here, cMSCs were isolated based on the subfractionation culturing method. Afterward, isolated clones that could reproduce up to passage three were stored as the seed stock. To select proliferative clones, we used an innovative, cost-effective screening strategy based on lengthy serial passaging. Finally, the selected clones re-cultured from the seed stock to establish the following four-tired cell banking system: initial, master, working, and end of product cell banks (ICB, MCB, WCB, and EoPCB).

Results

Through a rigorous screening strategy, three clones were selected from a total of 21 clones that were stored during the clonal isolation process. The selected clones met the identity, quality, and safety assessments criteria. The validated clones were stored in the four-tiered cell bank system under GMP conditions, and certificates of analysis were provided for the three-individual ready-to-release batches. Finally, a stability study validated the EoPCB, release, and transport process of the frozen final products.

Conclusion

Collectively, this study presents a technical and translational overview of a GMP-compatible cMSCs manufacturing technology that could lead to the development of similar products for potential therapeutic applications.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1007/s12015-022-10351-x.

Strategies to address mesenchymal stem/stromal cell heterogeneity in immunomodulatory profiles to improve cell-based therapies

Mesenchymal stromal cells (MSCs) have gained immense attention over the past two decades due to their multipotent differentiation potential and pro-regenerative and immunomodulatory cytokine secretory profiles. Their ability to modulate the host immune system and promote tolerance has prompted several allogeneic and autologous hMSC-based clinical trials for the treatment of graft-versus-host disease and several other immune-induced disorders. However, clinical success beyond safety is still controversial and highly variable, with inconclusive therapeutic benefits and little mechanistic explanation. This clinical variability has been broadly attributed to inconsistent MSC sourcing, phenotypic characterization, variable potency, and non-standard isolation protocols, leading to functional heterogeneity among administered MSCs. Homogeneous MSC populations are proposed to yield more predictable, reliable biological responses and clinically meaningful properties relevant to cell-based therapies. Limited comparisons of heterogeneous MSCs with homogenous MSCs are reported. This review addresses this gap in the literature with a critical analysis of strategies aimed at decreasing MSC heterogeneity concerning their reported immunomodulatory profiles. STATEMENT OF SIGNIFICANCE: This review collates, summarizes, and critically analyzes published strategies that seek to improve homogeneity in immunomodulatory functioning MSC populations intended as cell therapies to treat immune-based disorders, such as graft-vs-host-disease. No such review for MSC therapies, immunomodulatory profiles and cell heterogeneity analysis is published. Since MSCs represent the most clinically studied experimental cell therapy platform globally for which there remains no US domestic marketing approval, insights into MSC challenges in therapeutic product development are imperative to providing solutions for immunomodulatory variabilities.

Long-term efficacy and safety of intravenous injection of clonal mesenchymal stem cells derived from bone marrow in five adults with moderate to severe atopic dermatitis

Atopic dermatitis is a chronic and relapsing inflammatory skin disease that is treated with immunosuppressants. However, long-term use of immunosuppressants may cause toxicity and severe side-effects. To confirm the long-term efficacy and safety of clonal mesenchymal stem cell therapy, we performed investigator-initiated clinical trials and long-term observation in five adult patients with moderate to severe atopic dermatitis that was refractory to conventional treatments. The clinical response assessment values such as Eczema Area and Severity Index (EASI) improved significantly at 16 weeks, and 80% (4/5) of the patients achieved EASI-50 after one or two treatment cycles. Patients were observed for long-term efficacy and safety for an average of 38 weeks (range, 16-86) and showed no serious side-effects. Among the cytokines tested, CCL-17, interleukin (IL)-13, and IL-22 significantly decreased at the end-point of the five participants, two patients who maintained good clinical response over 84 weeks showed increased IL-17 cytokine levels in the blood.

The Effects of Human Bone Marrow-Derived Mesenchymal Stem Cell Conditioned Media Produced with Fetal Bovine Serum or Human Platelet Lysate on Skin Rejuvenation Characteristics

Background and Objectives

Human mesenchymal stem cell-conditioned medium (MSC-CM) is produced using mesenchymal stem cell culture technology and has various benefits for the skin, including wrinkle removal, skin regeneration, and increased antioxidant activity. Its popularity is thus increasing in the field of functional cosmetics.

Methods and Results

In this study, we analyzed the effects of fetal bovine serum-supplemented MSC-CM (FBS- MSC-CM) and human platelet lysate-supplemented MSC-CM (hPL-MSC-CM) on skin rejuvenation characteristics. We found that the concentrations of important growth factors (VEGF, TGF-β1, and HGF) and secretory proteins for skin regeneration were significantly higher in hPL-MSC-CM than in FBS-MSC-CM. Furthermore, the capacity for inducing proliferation of human dermal fibroblast (HDF) and keratinocytes, the migration ability of HDF, extracellular matrix (ECM) production such as collagen and elastin was higher in hPL-MSC-CM than that in FBS- MSC-CM.

Conclusions

These results support the usefulness and high economic value of hPL-MSC-CM as an alternative source of FBS-MSC-CM in the cosmetic industry for skin rejuvenation.

rhBMP-2 Pre-Treated Human Periodontal Ligament Stem Cell Sheets Regenerate a Mineralized Layer Mimicking Dental Cementum

The periodontal complex consisting of alveolar bone, cementum, and periodontal ligaments (PDL) supports human teeth through the systematic orchestration of mineralized tissues and fibrous tissues. Importantly, cementum, the outermost mineralized layer of dental roots, plays an essential role by bridging the inner ligaments from the dental root to the alveolar bone. When the periodontal complex is damaged, the regeneration of each component of the periodontal complex is necessary; however, it is still challenging to achieve complete functional regeneration. In this study, we tried to control the regeneration of cementum and PDL by using a human PDL stem cell (hPDLSC) sheet engineering technology with the pretreatment of recombinant human BMP-2 (rhBMP-2). Isolated hPDLSCs obtained from extracted human teeth were pretreated with rhBMP-2 for in vitro osteogenic differentiation and grafted on the micro/macro-porous biphasic calcium phosphate (MBCP) blocks, which represent dental roots. The MBCPs with hPDLSC sheets were implanted in the subcutaneous layer of immune-compromised mice, and rhBMP-2 pretreated hPDLSC sheets showed higher mineralization and collagen ligament deposition than the no-pretreatment group. Therefore, the rhBMP-2-hPDLSC sheet technique could be an effective strategy for the synchronized regeneration of two different tissues: mineralized tissue and fibrous tissues in periodontal complexes.

Multi-differentiation potential is necessary for optimal tenogenesis of tendon stem cells

Background

Tendon injury is a significant clinical problem due to poor healing and a high reinjury rate; successful treatment is limited by our poor understanding of endogenous tendon stem cells. Recent evidence suggests that adult stem cells are phenotypically diverse, even when comparing stem cells isolated from the same tissue from the same individual, and may in fact exist on a spectrum of proliferation and differentiation capacities. Additionally, the relationships between and clinical relevance of this phenotypic variation are poorly understood. In particular, tenogenic capacity has not been studied in comparison to tenogenic differentiation and cell proliferation. Toward this end, we performed a comprehensive assessment of cell proliferation and differentiation capacity toward four connective tissue lineages (tendon, cartilage, bone, and adipose) using tendon stem cell lines derived from single cells released directly from tendon tissue to (1) evaluate the differences, if any, in tenogenic potential, and (2) identify the relationships between differentiation phenotypes and proliferation capacity.

Methods

Tendon stem cells were derived from the endotenon of superficial digital flexor tendon from 3 horses. The cell suspension from each horse was separately plated simultaneously (1) at moderate density to generate a heterogenous population of cells—parent tendon cell line—and (2) at low density to separate single cells from each other to allow isolation of colonies that derive from single mother cells—clonal tendon stem cell lines.

Thirty clonal tendon stem cell lines—10 from each horse—and each parent tendon cell line were assessed for tenogenesis, tri-lineage differentiation, and cell proliferation. Differentiation was confirmed by lineage-specific cell staining and quantified by the relative gene expression of lineage-specific markers. Statistical significance was determined using analysis of variance and post hoc Tukey’s tests.

Results

Three distinct differentiation phenotypes—differentiation potency toward all 4 tissue lineages and two tri-lineage differentiation potencies—were identified in tendon clonal stem cell lines. These phenotypes were differentiation toward (1) tendon, cartilage, bone, and adipose (TCOA); (2) tendon, cartilage, and bone (TCO); and (3) tendon, cartilage, and adipose (TCA). Further, clonal cell lines that differentiated toward all four lineages had the highest expression of scleraxis and mohawk upon tenogenesis. Moreover, cell proliferation was significantly different between phenotypic groups, as evidenced by increased numbers of cumulative cell population doublings in clonal cell lines that did not differentiate toward adipose.

Conclusions

Our study provides evidence of the heterogenous character of adult stem cells and identifies key differences in tendon stem cell differentiation and proliferative potentials from the same individual and from the same tendon. Isolation of tendon stem cell lines with the capacity to differentiate into all four connective tissue lineages may yield improved therapeutic benefits in clinical models of repair and promote a native, regenerative phenotype in engineered tendons. Future studies may be targeted to understanding the functional contributions of each tendon stem cell phenotype in vivo and identifying additional cell phenotypes.

Comparative study on metabolite level in tissue-specific human mesenchymal stem cells by an ultra-performance liquid chromatography quadrupole time of flight mass spectrometry

Mesenchymal stem cells (MSCs) are a promising therapeutic option for cell-based therapy due to their immunomodulatory and regenerative properties. They can be isolated from various adult tissues, including bone marrow, fat, dental tissue, and glandular tissue. Although they share common characteristics, little is known about the biological differences between MSC populations derived from different tissues. In this study, we used MS to compare the endogenous metabolite level in the human MSCs originating from the bone marrow, adipose tissue, periodontal ligaments, and salivary glands. Using an optimized metabolomics technique, we verified that human MSCs exhibit differences in the endogenous metabolite level depending on their source material, while the multivariate analysis showed that 5 lysophosphatidylcholines and 3 lysophosphatidylethanolamines can serve as markers for the discrimination between MSC sources and may be related to differences in their differentiation capacity. These results may significantly contribute to further mechanistic studies on the MSCs and provide novel insights into the properties and optimal usage of MSCs from different tissues.

Minoxidil Promotes Hair Growth through Stimulation of Growth Factor Release from Adipose-Derived Stem Cells

Minoxidil directly promotes hair growth via the stimulation of dermal papilla (DP) and epithelial cells. Alternatively, there is little evidence for indirect promotion of hair growth via stimulation of adipose-derived stem cells (ASCs). We investigated whether minoxidil stimulates ASCs and if increased growth factor secretion by ASCs facilitates minoxidil-induced hair growth. Telogen-to-anagen induction was examined in mice. Cultured DP cells and vibrissae hair follicle organ cultures were used to further examine the underlying mechanisms. Subcutaneous injection of minoxidil-treated ASCs accelerated telogen-to-anagen transition in mice, and increased hair weight at day 14 post-injection. Minoxidil did not alter ASC proliferation, but increased migration and tube formation. Minoxidil also increased the secretion of growth factors from ASCs, including chemokine (C-X-C motif) ligand 1 (CXCL1), platelet-derived endothelial cell growth factor (PD-ECGF), and platelet-derived growth factor-C (PDGF-C). Minoxidil increased extracellular signal–regulated kinases 1/2 (ERK1/2) phosphorylation, and concomitant upregulation of PD-ECGF and PDGF-C mRNA levels were attenuated by an ERK inhibitor. Subcutaneous injection of CXCL1, PD-ECGF, or PDGF-C enhanced anagen induction in mice, and both CXCL1 and PDGF-C increased hair length in ex vivo organ culture. Treatment with CXCL1, PD-ECGF, or PDGF-C also increased the proliferation index in DP cells. Finally, topical application of CXCL1, PD-ECGF, or PDGF-C with 2% minoxidil enhanced anagen induction when compared to minoxidil alone. Minoxidil stimulates ASC motility and increases paracrine growth factor signaling. Minoxidil-stimulated secretion of growth factors by ASCs may enhance hair growth by promoting DP proliferation. Therefore, minoxidil can be used as an ASC preconditioning agent for hair regeneration.

Immunomodulatory mechanisms of mesenchymal stem cells and their therapeutic applications

In the recent years, many studies have shown that MSCs must be stimulated by pro-inflammatory cytokines or other immune mediators before they can modulate immune cells in inflamed and damaged tissues. MSCs appear to be involved in inducing several regulatory immune cells, such as Tregs, Bregs, and regulatory NK cells. This new immune milieu created by MSCs may establish a tolerogenic environment that leads to an optimal condition for the treatment of immune diseases. The mechanisms of MSC action to treat immune disorders need to be further investigated in more detail. Since there have been some contradictory outcomes of clinical trials, it is necessary to perform large-scale and randomized clinical studies, such as a phase 3 placebo-controlled double-blind study of a third party MSCs to optimize MSC administration and to prove safety and efficacy of MSC treatment. MSCs offer great therapeutic promise, especially for the treatment of difficult-to-treat immune diseases.

Transplantation of human bone marrow-derived clonal mesenchymal stem cells reduces fibrotic scar formation in a rat spinal cord injury model

This study aimed to evaluate the therapeutic effect on tissue repair and scar formation of human bone marrow-derived clonal mesenchymal stem cells (hcMSCs) homogeneously isolated by using a subfractionation culturing method, in comparison with the non-clonal MSCs (hMSCs), in a rat spinal cord injury (SCI) model. The SCI was made using a vascular clip at the T9 level. Cells were transplanted into the lesion site 3 days after injury. A functional test was performed over 4 weeks employing a BBB score. Rats were killed for histological analysis at 3 days, 1 week and 4 weeks after injury. The transplantation of hMSCs and hcMSCs significantly reduced lesion size and the fluid-filled cavity at 4 weeks in comparison with the control group injected with phosphate buffered saline (PBS) (p < 0.01). Transplantation of hcMSCs showed more axons reserved than that of hMSCs in the lesion epicentre filled with non-neuronal tissues. In addition, hMSCs and hcMSCs clearly reduced the inflammatory reaction and intraparenchymal hemorrhaging, compared with the PBS group. Interestingly, hcMSCs largely decreased Col IV expression, one of the markers of fibrotic scars. hcMSCs yielded therapeutic effects more than equal to those of hMSCs on the SCI. Both hMSCs and hcMSCs created an increase in axon regeneration and reduced scar formation around the SCI lesion. Copyright © 2017 John Wiley & Sons, Ltd.

ICOSL expression in human bone marrow-derived mesenchymal stem cells promotes induction of regulatory T cells

Mesenchymal stem cells (MSCs) can modulate lymphocyte proliferation and function. One of the immunomodulatory functions of MSCs involves CD4⁺CD25⁺FoxP3⁺ regulatory T cells (Tregs), which negatively regulate inflammatory responses. MSC-mediated Treg induction is supposed to be regulated by mechanisms requiring both soluble and cell contact-dependent factors. Although the involvement of soluble factors has been revealed, the contact-dependent mechanisms in MSC-mediated Treg induction remain unclear. We attempted to identify molecule(s) other than secreted factors that are responsible for MSC-mediated Treg induction and to uncover the underlying mechanisms. Under in vitro Treg-inducing conditions, ICOSL expression in MSCs coincided with Treg induction in co-cultures of MSCs with CD4⁺ T cells. When cultured in a transwell plate, MSCs failed to induce Tregs. Neutralization or knockdown of ICOSL significantly reduced Tregs and their IL-10 release. ICOSL overexpression in MSCs promoted induction of functional Tregs. ICOSL-ICOS signaling promoted Treg differentiation from CD4⁺ T cells through activation of the phosphoinositide 3-kinase-Akt pathway. MSCs primed with Interleukin-1β significantly induced Tregs through ICOSL upregulation. We demonstrated that the Treg-inducing activity of MSCs is proportionate to their basal ICOSL expression. This study provides evidence that ICOSL expression in human MSCs plays an important role in contact-dependent regulation of MSC-mediated Treg induction.

Hypoxia Suppresses Spontaneous Mineralization and Osteogenic Differentiation of Mesenchymal Stem Cells via IGFBP3 Up-Regulation

Hypoxia has diverse stimulatory effects on human adipose-derived stem cells (ASCs). In the present study, we investigated whether hypoxic culture conditions (2% O₂) suppress spontaneous mineralization and osteogenic differentiation of ASCs. We also investigated signaling pathways and molecular mechanisms involved in this process. We found that hypoxia suppressed spontaneous mineralization and osteogenic differentiation of ASCs, and up-regulated mRNA and protein expression of Insulin-like growth factor binding proteins (IGFBPs) in ASCs. Although treatment with recombinant IGFBPs did not affect osteogenic differentiation of ASCs, siRNA-mediated inhibition of IGFBP3 attenuated hypoxia-suppressed osteogenic differentiation of ASCs. In contrast, overexpression of IGFBP3 via lentiviral vectors inhibited ASC osteogenic differentiation. These results indicate that hypoxia suppresses spontaneous mineralization and osteogenic differentiation of ASCs via intracellular IGFBP3 up-regulation. We determined that reactive oxygen species (ROS) generation followed by activation of the MAPK and PI3K/Akt pathways play pivotal roles in IGFBP3 expression under hypoxia. For example, ROS scavengers and inhibitors for MAPK and PI3K/Akt pathways attenuated the hypoxia-induced IGFBP3 expression. Inhibition of Elk1 and NF-κB through siRNA transfection also led to down-regulation of IGFBP3 mRNA expression. We next addressed the proliferative potential of ASCs with overexpressed IGFBP3, but IGFBP3 overexpression reduced the proliferation of ASCs. In addition, hypoxia reduced the osteogenic differentiation of bone marrow-derived clonal mesenchymal stem cells. Collectively, our results indicate that hypoxia suppresses the osteogenic differentiation of mesenchymal stem cells via IGFBP3 up-regulation.

Characterization of adipose tissue mesenchymal stromal cell subsets with distinct plastic adherence

Mesenchymal stromal cells (MSCs) established by in-vitro adherence culture have been widely utilized for various cell therapeutic trials, but potential heterogeneity that can be caused by preparation methods are poorly characterized. In this study, we show that at least two distinct subsets of MSCs with different adherence to plastic surface exist in human adipose tissue-derived stromal vascular fraction (SVF); while 69% of total colony forming units in SVF adhere to the surface before 3 hrs of plating, 13-17% of colonogenic cells adhered to the surface at later period of 15 hr to 1 week after plating. Of note, the late adherent MSCs exhibited higher self-renewal of colony forming cells and higher proliferating potential with comparable level of osteogenic or adipogenic differentiation potential to the early adherence subsets. Moreover, late adherent cells exhibited distinct pattern of paracrine secretome including higher level secretion of cytokines than the early adherent subsets. Taken together, these results suggest the possibility that distinct adherence properties of MSCs can be another parameter of clonal heterogeneity in the subpopulations of adipose tissue MSCs and that it can be an important factor for optimization of MSC preparation for cell therapeutic trials.

Allogeneic clonal mesenchymal stem cell therapy for refractory graft-versus-host disease to standard treatment: a phase I study

Severe graft-versus-host disease (GVHD) is an often lethal complication of allogeneic hematopoietic stem cell transplantation (HSCT). The safety of clinical-grade mesenchymal stem cells (MSCs) has been validated, but mixed results have been obtained due to heterogeneity of the MSCs. In this phase I study, the safety of bone marrow-derived homogeneous clonal MSCs (cMSCs) isolated by a new subfractionation culturing method was evaluated. cMSCs were produced in a GMP facility and intravenously administered to patients who had refractory GVHD to standard treatment resulting after allogeneic HSCT for hematologic malignancies. After administration of a single dose (1×10⁶ cells/kg), 11 patients were evaluated for cMSC treatment safety and efficacy. During the trial, nine patients had 85 total adverse events and the rate of serious adverse events was 27.3% (3/11 patients). The only one adverse drug reaction related to cMSC administration was grade 2 myalgia in one patient. Treatment response was observed in four patients: one with acute GVHD (partial response) and three with chronic GVHD. The other chronic patients maintained stable disease during the observation period. This study demonstrates single cMSC infusion to have an acceptable safety profile and promising efficacy, suggesting that we can proceed with the next stage of the clinical trial.

Intracavernous delivery of clonal mesenchymal stem cells rescues erectile function in the streptozotocin-induced diabetic mouse

The major hurdle for the clinical application of stem cell therapy is the heterogeneous nature of the isolated cells, which may cause different treatment outcomes. The aim of this study was to examine the effectiveness of mouse clonal bone marrow-derived stem cells (BMSCs) obtained from a single colony by using subfractionation culturing method for erectile function in diabetic animals. Twelve-week-old C57BL/6J mice were divided into four groups: controls, diabetic mice, and diabetic mice treated with a single intracavernous injection of PBS (20 μL) or clonal BMSCs (3 × 10(5) cells/20 μL). Clonal BMSCs were isolated from 5-week-old C3H mice. Two weeks after treatment, erectile function was measured by electrical stimulation of the cavernous nerve. The penis was stained with antibodies to PECAM-1, smooth muscle α-actin, neuronal nitric oxide synthase (nNOS), neurofilament, and phosphorylated endothelial NOS (phospho-eNOS). We also performed Western blot for phospho-eNOS, and eNOS in the corpus cavernosum tissue. Local delivery of clonal BMSCs significantly restored cavernous endothelial and smooth muscle cell contents, and penile nNOS and neurofilament contents, and induced eNOS phosphorylation (Ser1177) in diabetic mice. Intracavernous injection of clonal BMSCs induced significant recovery of erectile function, which reached 80-90% of the control values. Clonal BMSCs successfully restored erectile function through dual angiogenic and neurotrophic effects in diabetic mice. The homogenous nature of clonal mesenchymal stem cells may allow their clinical applications and open a new avenue through which to treat diabetic erectile dysfunction.

Manufacture of Clinical-Grade Human Clonal Mesenchymal Stem Cell Products from Single Colony Forming Unit-Derived Colonies Based on the Subfractionation Culturing Method

Stem cell products derived from mesenchymal stem cells (MSCs) have been widely used in clinical trials, and a few products have been already commercialized. However, the therapeutic effects of clinical-grade MSCs are still controversial owing to mixed results from recent clinical trials. A potential solution to overcome this hurdle may be to use clonal stem cells as the starting cell material to increase the homogeneity of the final stem cell products. We have previously developed an alternative isolation and culture protocol for establishing a population of clonal MSCs (cMSCs) from single colony forming unit (CFU)-derived colonies. In this study, we established a good manufacturing practice (GMP)-compatible procedure for the clinical-grade production of human bone marrow-derived cMSCs based on the subfractionation culturing method. We optimized the culture procedures to expand and obtain a clonal population of final MSC products from single CFU-derived colonies in a GMP facility. The characterization results of the final cMSC products met our preset criteria. Animal toxicity tests were performed in a good laboratory practice facility, and showed no toxicity or tumor formation in vivo. These tests include single injection toxicity, multiple injection toxicity, biodistribution analysis, and tumorigenicity tests in vivo. No chromosomal abnormalities were detected by in situ karyotyping using oligo-fluorescence in situ hydridization (oligo-FISH), providing evidence of genetic stability of the clinical-grade cMSC products. The manufacture and quality control results indicated that our GMP methodology could produce sufficient clonal population of MSC products from a small amount of bone marrow aspirate to treat a number of patients.

Galectin-9 is Involved in Immunosuppression Mediated by Human Bone Marrow-derived Clonal Mesenchymal Stem Cells

Bone marrow-derived mesenchymal stem cells (MSCs) have immunomodulatory properties and can suppress exaggerated pro-inflammatory immune responses. Although the exact mechanisms remain unclear, a variety of soluble factors are known to contribute to MSC-mediated immunosuppression. However, functional redundancy in the immunosuppressive properties of MSCs indicates that other uncharacterized factors could be involved. Galectin-9, a member of the β-galactoside binding galectin family, has emerged as an important regulator of innate and adaptive immunity. We examined whether galectin-9 contributes to MSC-mediated immunosuppression. Galectin-9 was strongly induced and secreted from human MSCs upon stimulation with pro-inflammatory cytokines. An in vitro immunosuppression assay using a knockdown approach revealed that galectin-9-deficient MSCs do not exert immunosuppressive activity. We also provided evidence that galectin-9 may contribute to MSC-mediated immunosuppression by binding to its receptor, TIM-3, expressed on activated lymphocytes, leading to apoptotic cell death of activated lymphocytes. Taken together, our findings demonstrate that galectin-9 is involved in MSC-mediated immunosuppression and represents a potential therapeutic factor for the treatment of inflammatory diseases.

Therapeutic effects of mouse bone marrow-derived clonal mesenchymal stem cells in a mouse model of inflammatory bowel disease

Mouse bone marrow-derived clonal mesenchymal stem cells (mcMSCs), which were originated from a single cell by a subfractionation culturing method, are recognized as new paradigm for stem cell therapy featured with its homogenous cell population. Next to proven therapeutic effects against pancreatitis, in the current study we demonstrated that mcMSCs showed significant therapeutic effects in dextran sulfate sodium (DSS)-induced experimental colitis model supported with anti-inflammatory and restorative activities. mcMSCs significantly reduced the disease activity index (DAI) score, including weight loss, stool consistency, and intestinal bleeding and significantly increased survival rates. The pathological scores were also significantly improved with mcMSC. We have demonstrated that especial mucosal regeneration activity accompanied with significantly lowered level of apoptosis as beneficiary actions of mcMSCs in UC models. The levels of inflammatory cytokines including TNF-α, IFN-γ, IL-1β, IL-6, and IL-17 were all significantly concurrent with significantly repressed NF-κB activation compared to the control group and significantly decreased infiltrations of responsible macrophage and neutrophil. Conclusively, our findings provide the rationale that mcMSCs are applicable as a potential source of cell-based therapy in inflammatory bowel diseases, especially contributing either to prevent relapse or to accelerate healing as solution to unmet medical needs in IBD therapy.

Functional regulation of adipose-derived stem cells by PDGF-D

Platelet-derived growth factor-D (PDGF-D) was recently identified, and acts as potent mitogen for mesenchymal cells. PDGF-D also induces cellular transformation and promotes tumor growth. However, the functional role of PDGF-D in adipose-derived stem cells (ASCs) has not been identified. Therefore, we primarily investigated the autocrine and paracrine roles of PDGF-D in this study. Furthermore, we identified the signaling pathways and the molecular mechanisms involved in PDGF-D-induced stimulation of ASCs. It is of interest that PDGF-B is not expressed, but PDGF-D and PDGF receptor-β are expressed in ASCs. PDGF-D showed the strongest mitogenic effect on ASCs, and PDGF-D regulates the proliferation and migration of ASCs through the PI3K/Akt pathways. PDGF-D also increases the proliferation and migration of ASCs through generation of mitochondrial reactive oxygen species (mtROS) and mitochondrial fission. mtROS generation and fission were mediated by p66Shc phosphorylation, and BCL2-related protein A1 and Serpine peptidase inhibitor, clade E, member 1 mediated the proliferation and migration of ASCs. In addition, PDGF-D upregulated the mRNA expression of diverse growth factors such as vascular endothelial growth factor A, fibroblast growth factor 1 (FGF1), FGF5, leukemia inhibitory factor, inhibin, beta A, interleukin 11, and heparin-binding EGF-like growth factor. Therefore, the preconditioning of PDGF-D enhanced the hair-regenerative potential of ASCs. PDGF-D-induced growth factor expression was attenuated by a pharmacological inhibitor of mitogen-activated protein kinase pathway. In summary, PDGF-D is highly expressed by ASCs, where it acts as a potent mitogenic factor. PDGF-D also upregulates growth factor expression in ASCs. Therefore, PDGF-D can be considered a novel ASC stimulator, and used as a preconditioning agent before ASC transplantation.

Pharmacokinetics and in vivo fate of intra-articularly transplanted human bone marrow-derived clonal mesenchymal stem cells

In this study, we report the pharmacokinetics and in vivo fate of intra-articularly transplanted human mesenchymal stem cells (MSCs) in comparison with those of intravenously administered cells. Bone marrow-derived human clonal mesenchymal stem cells (hcMSCs) were transplanted to nude mice through intravenous or intra-articular routes. The numbers of hcMSCs in blood and tissue samples were measured by the quantitative real-time-polymerase chain reaction (qPCR) with human Alu (hAlu) as a detection marker. Following intra-articular transplantation, the blood levels of hcMSCs peaked 8 h postdose and gradually diminished, showing a 95-fold higher mean residence time than hcMSCs delivered through the intravenous route. Unlike intravenously administered hcMSCs, intra-articularly injected hcMSCs were mainly retained at injection joint sites where their levels 8 h postdose were 116-fold higher than those in muscle tissues. Regardless of injection routes, biodistribution patterns did not significantly differ between normal and osteoarthritis-induced mice. Quantitative analysis using hAlu-specific qPCR revealed that hcMSC levels in joint tissues were significantly higher than those in muscle tissues 120 days postdose. These dramatic differences in kinetic behavior and fate of intra-articularly transplanted hcMSCs compared with intravenously administered hcMSCs may provide insights useful for the development of human MSCs for arthritis therapeutics.

Non-invasive characterization of the adipogenic differentiation of human bone marrow-derived mesenchymal stromal cells by HS-SPME/GC-MS

A non-invasive method to characterize human mesenchymal stromal cells during adipogenic differentiation was developed for the first time. Seven fatty acid methyl esters (FAMEs), including methyl laurate, methyl myristate, methyl palmitate, methyl linoleate, methyl oleate, methyl elaidate and methyl stearate, were used for characterizing adipogenic differentiation using headspace solid-phase microextraction (HS-SPME) which is a very simple and non-invasive method for the extraction of volatile compounds. Glassware was used for culturing mesenchymal stromal cells rather than the common plasticware to minimize contamination by volatile impurities. The optimal SPME fiber was selected by comparing diverse fibers containing two pure liquid polymers (PDMS and PA) and two porous solids (PDMS/DVB and CAR/PDMS). Using optimized procedures, we discovered that seven FAMEs were only detected in adipogenic differentiated mesenchymal stromal cells and not in the mesenchymal stromal cells before differentiation. These data could support the quality control of clinical mesenchymal stromal cell culture in the pharmaceutical industry in addition to the development of many clinical applications using mesenchymal stromal cells.

Therapeutic effect of human clonal bone marrow-derived mesenchymal stem cells in severe acute pancreatitis

Severe acute pancreatitis (SAP), a common necroinflammatory disease initiated by the premature activation of digestive enzymes within the pancreatic acinar cells, is associated with significant morbidity and mortality. In this study, we investigated whether human bone marrow-derived clonal mesenchymal stem cells (hcMSCs), isolated from human bone marrow aspirate according to our newly established isolation protocol, have potential therapeutic effects in SAP. SAP was induced by three intraperitoneal (i.p.) injections of cerulein (100 μg/kg) and sequential LPS (10 mg/kg) in Sprague-Dawley (SD) rats. hcMSCs (1 × 10(6)/head) were infused on 24 h after LPS injection via the tail vein. The rats were sacrificed 3 days after infusion of hcMSCs. We observed that infused hcMSCs reduced the levels of serum amylase and lipase. Infused hcMSCs ameliorated acinar cell necrosis, pancreatic edema, and inflammatory infiltration. Also, infused hcMSCs decreased the level of malondialdehyde, and increased the levels of glutathione peroxidase and superoxide dismutase. The number of TUNEL positive acinar cells was reduced after hcMSCs infusion. In addition, hcMSCs reduced the expression levels of pro-inflammation mediators and cytokines, and increased the expression of SOX9 in SAP. Taken together, hcMSCs could effectively relieve injury of pancreatitis as a promising therapeutics for SAP.

Bone marrow-derived clonal mesenchymal stem cells inhibit ovalbumin-induced atopic dermatitis

Mesenchymal stem cells (MSCs) possess immunomodulatory activities, including suppression of T- and B-cell activation. However, their effects on atopic dermatitis (AD) have not yet been studied. Using an ovalbumin-induced AD mouse model, we investigated whether MSCs can be used as therapeutics in AD. We isolated both allogeneic and syngeneic clonal MSCs (cMSCs) from mouse bone marrow according to the subfractionation culturing method. Our cMSCs suppressed both T- and B-cell activation. T-cell proliferation and cytokine production, including interferon (IFN)-γ and interleukin (IL)-4, were suppressed by inhibition of transcription factors, such as T-bet, GATA-3, and c-Maf. Those transcription factors were nitric oxide dependent. Immunoglobulin E (IgE) suppression occurred through downregulation of AID and BLIMP-1, important regulators for isotype class switch and B-cell differentiation. The cMSCs were injected intravenously into ovalbumin-induced AD mouse model, and the therapeutic effects were analyzed. Injection of both allogeneic and syngeneic cMSCs in an AD mouse model inhibited cell infiltration in skin lesions and decreased the serum level of IgE. IL-4 expression was also suppressed by cMSCs in both the lymph node and skin. The cMSCs migrated to skin lesions and draining lymph nodes. Taken together, these data demonstrated that cMSCs, which suppressed T- and B-cell functions, can be used for the treatment of AD in mice.

Mesenchymal stem cells infected with Mycoplasma arginini secrete complement C3 to regulate immunoglobulin production in B lymphocytes

Mesenchymal stem cells (MSCs) have immunomodulatory functions such as the suppression of T and B cells. MSCs suppress immunoglobulin (Ig) production by B cells via cell–cell contact as well as via secretion of soluble factors. Our study showed that the conditioned medium (CM) of MSCs infected with a mycoplasma strain, Mycoplasma arginini, has marked inhibitory effects on Ig production by lipopolysaccharide/interleukin-4-induced B cells compared with mycoplasma-free MSC-CM. We analyzed mycoplasma-infected MSC-CM by fast protein liquid chromatography and liquid chromatography to screen the molecules responsible for Ig inhibition. Complement C3 (C3) was the most critical molecule among the candidates identified. C3 was shown to be involved in the suppression of the Ig production of B cells. C3 was secreted by mycoplasma-infected MSCs, but not by mycoplasma-free MSCs or B cells. It was able to directly inhibit Ig production by B cells. In the presence of a C3 inhibitor, Ig inhibition by MSC-CM was abrogated. This inhibitory effect was concomitant with the downregulation of B-cell-induced maturation protein-1, which is a regulator of the differentiation of antibody-secreting plasma cells. These results suggest that C3 secreted from mycoplasma-infected MSCs has an important role in the immunomodulatory functions of MSCs. However, its role in vivo needs to be explored.

Molecular Characterization of Neurally Differentiated Human Bone Marrow-derived Clonal Mesenchymal Stem Cells

Bone marrow-derived mesenchymal stem cells (MSCs) are multipotent, with the ability to differentiate into different cell types. Additionally, the immunomodulatory activity of MSCs can downregulate inflammatory responses. The use of MSCs to repair injured tissues and treat inflammation, including in neuroimmune diseases, has been extensively explored. Although MSCs have emerged as a promising resource for the treatment of neuroimmune diseases, attempts to define the molecular properties of MSCs have been limited by the heterogeneity of MSC populations. We recently developed a new method, the subfractionation culturing method, to isolate homogeneous human clonal MSCs (hcMSCs). The hcMSCs were able to differentiate into fat, cartilage, bone, neuroglia, and liver cell types. In this study, to better understand the properties of neurally differentiated MSCs, gene expression in highly homogeneous hcMSCs was analyzed. Neural differentiation of hcMSCs was induced for 14 days. Thereafter, RNA and genomic DNA was isolated and subjected to microarray analysis and DNA methylation array analysis, respectively. We correlated the transcriptome of hcMSCs during neural differentiation with the DNA methylation status. Here, we describe and discuss the gene expression profile of neurally differentiated hcMSCs. These findings will expand our understanding of the molecular properties of MSCs and contribute to the development of cell therapy for neuroimmune diseases.

Effects of bone marrow-derived mesenchymal stem cells and platelet-rich plasma on bone regeneration for osseointegration of dental implants: preliminary study in canine three-wall intrabony defects

Tissue engineering has been applied to overcome the obstacles encountered with bone regeneration for the placement of dental implants. The purpose of this study was to determine the bone formation ability of human bone marrow-derived mesenchymal stem cells (BMMSCs) and platelet-rich plasma (PRP) when applied separately or together to the intrabony defect around dental implants with a porous hydroxyapatite (HA) scaffold. Standardized three-wall intrabony defects (4 × 4 × 4 mm) were created at the mesial of each dental implant site in four mongrel dogs. Defects were then grafted with the following materials: HA + BMMSCs (HS group), HA + PRP (HP group), HA + BMMSCs + PRP (HSP group), and HA scaffold alone (HA group). The level of bone formation (bone density) and osseointegration (bone-to-implant contact [BIC]) in bone defects around the implants were evaluated by histological and histometric analysis at 6 and 12 weeks after the placement of implants. HA, HS, HP, and HSP groups generally showed an increase in bone density and BIC between 6 and 12 weeks, except BIC in the HS group. Although no statistically significant differences were found among HA, HS, HP, and HSP groups (p > 0.05), the highest level of bone density and BIC were observed in the HSP group after the 12-week healing period. Furthermore, the level of bone maturation was higher in the HSP group than in the other groups as determined histologically. The findings of this preliminary study suggest that BMMSCs and PRP combined with HA scaffold may provide additional therapeutic effects on bone regeneration and improve osseointegration in bone defects around dental implants.

Intracavernous delivery of clonal mesenchymal stem cells restores erectile function in a mouse model of cavernous nerve injury

INTRODUCTION

Recently, much attention has focused on stem cell therapy; bone marrow-derived stem cells (BMSCs) are one of the most studied mesenchymal stem cells used in the field of erectile dysfunction (ED). However, a major limitation for the clinical application of stem cell therapy is the heterogeneous nature of the isolated cells, which may cause different treatment outcomes.

AIM

We investigated the effectiveness of mouse clonal BMSCs obtained from a single colony by using subfractionation culturing method (SCM) for erectile function in a mouse model of cavernous nerve injury (CNI).

METHODS

Twelve-week-old C57BL/6J mice were divided into four groups: sham operation group, bilateral CNI group receiving a single intracavernous (IC) injection of phosphate-buffered saline (20 μL) or clonal BMSCs (3 × 10(5) cells/20 μL), and receiving a single intraperitoneal (IP) injection of clonal BMSCs (3 × 10(5) cells/20 μL).

MAIN OUTCOME MEASURES

The clonal BMSC line was analyzed for cell-surface epitopes by using fluorescence-activated cell sorting and for differentiation potential. Two weeks after CNI and treatment, erectile function was measured by electrically stimulating the cavernous nerve. The penis was harvested for histologic examinations and Western blot analysis.

RESULTS

Clonal BMSCs expressed cell surface markers for mesenchymal stem cells and were capable of differentiating into several lineages, including adipogenic, osteogenic, and chondrogenic cells. Both IC and IP injections of clonal BMSCs significantly restored cavernous endothelial and smooth muscle content, and penile nNOS and neurofilament content in CNI mice. IC injection of clonal BMSCs induced significant recovery of erectile function, which reached 90-100% of the sham control values, whereas IP injection of clonal BMSCs partially restored erectile function.

CONCLUSION

We established a homogeneous population of mouse clonal BMSCs using SCM; clonal BMSCs successfully restored erectile function in CNI mice. The homogeneous nature of clonal mesenchymal stem cells may allow their clinical applications.

Mesenchymal Stem Cell Lines Isolated by Different Isolation Methods Show Variations in the Regulation of Graft-versus-host Disease

Since the discovery of the immunomodulation property of mesenchymal stem cells (MSCs) about a decade ago, it has been extensively investigated whether MSCs can be used for the treatment of immune-related diseases, such as graft-versus-host disease (GvHD). However, how to evaluate the efficacy of human MSCs for the clinical trial is still unclear. We used an MHC-mismatched model of GvHD (B6 into BALB/c). Surprisingly, the administration of the human MSCs (hMSCs) could reduce the GvHD-related mortality of the mouse recipients and xenogeneically inhibit mouse T-cell proliferation and IFN-γ production in vitro. We recently established a new protocol for the isolation of a homogeneous population of MSCs called subfractionation culturing methods (SCM), and established a library of clonal MSC lines. Therefore, we also investigated whether MSCs isolated by the conventional gradient centrifugation method (GCM) and SCM show different efficacy in vivo. Intriguingly, clonal hMSCs (hcMSCs) isolated by SCM showed better efficacy than hMSCs isolated by GCM. Based on these results, the MHC-mismatched model of GvHD may be useful for evaluating the efficacy of human MSCs before the clinical trial. The results of this study suggest that different MSC lines may show different efficacy in vivo and in vitro.

Bone marrow-derived clonal mesenchymal stem cells as a source of cell therapy for promoting vocal fold wound healing

OBJECTIVES

We investigated whether mouse bone marrow-derived clonal mesenchymal stem cells (BM-cMSCs) could promote vocal fold (VF) wound healing by using a xenograft animal model.

METHODS

Homogeneous BM-cMSCs isolated by a subfractionation culturing method from the bone marrow aspirates of green fluorescent protein transgenic mice were injected into the VFs of rabbits immediately after direct mechanical injury. Macroscopic, biomechanical (rheometric), histologic, immunohistochemical, and transcriptional evaluations were performed on the scarred VFs 1 to 3 months after injury. Engraftment of the implanted BM-cMSCs was determined by detection of green fluorescent protein cells in the recipient VF by confocal microscopy.

RESULTS

The BM-cMSC-treated VFs showed improved morphological properties and viscoelasticity as compared to control VFs injected with phosphate-buffered saline solution. Histologic and immunohistochemical evaluations showed less excessive collagen deposition and increased density of glycosaminoglycans in the BM-cMSC-treated VFs as compared to the control VFs at 3 months after injury (p = 0.003 and p = 0.037, respectively). BM-cMSC transplantation led to a significant attenuation of fibronectin (p = 0.036) and transforming growth factor beta1 (p = 0.042) messenger RNA expression at 1 month after injury. Green fluorescent protein-expressing BM-cMSCs engrafted in recipient VFs were found at 1 month after implantation.

CONCLUSIONS

BM-cMSCs appeared to survive in the injured xenogeneic VFs after transplantation for up to 1 month and favorably enhanced the wound healing of VFs after injury. We conclude that BM-cMSCs are a possible source of cell therapy for vocal fold regeneration.

Interplay between mesenchymal stem cells and lymphocytes: implications for immunotherapy and tissue regeneration

In addition to their potential for replacing damaged and diseased tissues by differentiating into tissue-specific cells, mesenchymal stem cells (MSCs) have been found to interact closely with immune cells, such as lymphocytes. In this review, we will discuss current research regarding the immunomodulatory properties of MSCs and the effects of lymphocytes on MSCs. We will suggest how these findings could be translated to potential clinical treatment. MSCs can regulate immune response by inducing activated T-cell apoptosis through the FAS ligand (FASL)/FAS-mediated death pathway via cell-cell contact, leading to up-regulation of regulatory T-cells (Tregs), which ultimately results in immune tolerance. Conversely, lymphocytes can impair survival and osteogenic differentiation of implanted MSCs by secreting the pro-inflammatory cytokines IFN-γ and TNF-α and/or through the FASL/FAS-mediated death pathway, thereby negatively affecting MSC-mediated tissue regeneration. One novel strategy to improve MSC-based tissue engineering involves the reduction of IFN-γ and TNF-α concentration by systemic infusion of Tregs or local application of aspirin. Further understanding of the mechanisms underlying the interplay between lymphocytes and MSCs may be helpful in the development of promising approaches to improve cell-based regenerative medicine and immune therapies.

Intraglandular transplantation of bone marrow-derived clonal mesenchymal stem cells for amelioration of post-irradiation salivary gland damage

OBJECTIVES

External irradiation in head and neck cancers may induce irreversible hyposalivation and consequent xerostomia, stemming from radiation damage to salivary glands (SGs). As cell-based therapy has been reported to be able to repair or restore damaged SG tissues, we attempted to determine whether bone marrow-derived clonal mesenchymal stem cells (BM-cMSCs) can ameliorate irradiation-induced salivary gland damage via a murine model.

METHODS

External irradiation at a dose of 15Gy was delivered to the neck fields of C57BL/6 mice. We directly administered either homologous mouse BM-cMSCs labeled with PKH26 (treatment group) or PBS (control group) into SGs 24h after irradiation. Salivary flow rate (SFR) and lag time of salivation were measured at 12weeks after transplantation. At 4 and 12weeks post-transplantation, we performed morphological, histological, and immunofluorescent examinations. Transdifferentiation of administered BM-cMSCs into salivary epithelial cells was observed by confocal microscopy.

RESULTS

SFR was significantly increased in BM-cMSCs-transplanted mice compared with PBS-injected mice at 12weeks after transplantation. Administration of BM-cMSCs preserved the microscopic morphologies of SGs, with more functional acini in BM-cMSC-transplanted SGs than in PBS-injected SGs. Immunofluorescent staining revealed less apoptotic cells and increased microvessel density in BM-cMSC-transplanted SGs compared with PBS-injected SGs. PKH-26 labeled BM-cMSCs were detected in transplanted SGs at 4weeks after transplantation and in vivo transdifferentiation of BM-cMSCs into acinar cells was also observed.

CONCLUSION

This study suggests that BM-cMSCs can ameliorate salivary damage following irradiation and can be used as a source of cell-based therapy for restoration of irradiation-induced salivary hypofunction.

Gene expression profile reveals that STAT2 is involved in the immunosuppressive function of human bone marrow-derived mesenchymal stem cells

Emerging evidence of the potent immunosuppressive activity of mesenchymal stem cells (MSCs) by modulation of both innate and adaptive immune responses enables MSCs to be developed as a promising therapeutic modality for immune-related or inflammatory diseases. However, it is not clearly understood how MSCs exert their immunosuppressive effects on immune cells under inflammatory conditions. Using human bone marrow (BM)-derived clonal MSCs (hcMSCs), we obtained and analyzed a differentially expressed gene profile when stimulated with the inflammatory cytokines interferon-γ (IFN-γ) and tumor necrosis factor-α (TNF-α) to find novel candidate factors responsible for MSC immunomodulation. Microarray analysis showed that 5650 genes were upregulated and 5862 genes were downregulated with the cutoff of 2-fold expression change. Among these, the ICOSLG and STAT2 genes were drastically upregulated 173-fold and 154-fold, respectively. Reverse transcription-polymerase chain reaction analysis confirmed the microarray data. To evaluate whether their increased expression is related to MSC-mediated immunosuppression,siRNA-induced ICOSLG- or STAT2-knockdown hcMSCs were assessed for their T cell suppressive activity. We demonstrated that STAT2 but not ICOSLG is functionally involved in the immunosuppressive activity of hcMSCs as a novel regulator under inflammatory conditions. Gene ontology and pathway analyses further support the immunomodulatory function of hcMSCs when inflammatory stimulation was provided.Taken together, this study provides an informative genome-wide gene expression profile and molecular evidence for understanding the mechanisms underlying the modulation of immune cells by human BM-derived MSCs under inflammatory conditions.

Immunomodulatory properties of mesenchymal stem cells and their therapeutic applications

Mesenchymal stem cells (MSCs) are adult stem cells that can be isolated from most adult tissues, including bone marrow, adipose, liver, amniotic fluid, lung, skeletal muscle and kidney. The term MSC is currently being used to represent both mesenchymal stem cells and multipotent mesenchymal stromal cells. Numerous reports on systemic administration of MSCs leading to functional improvements based on the paradigm of engraftment and differentiation have been published. However, it is not only difficult to demonstrate extensive engraftment of cells, but also no convincing clinical results have been generated from phase 3 trials as of yet and prolonged responses to therapy have been noted after identification of MSCs had discontinued. It is now clear that there is another mechanism by which MSCs exert their reparative benefits. Recently, MSCs have been shown to possess immunomodulatory properties. These include suppression of T cell proliferation, influencing dendritic cell maturation and function, suppression of B cell proliferation and terminal differentiation, and immune modulation of other immune cells such as NK cells and macrophages. In terms of the clinical applications of MSCs, they are being tested in four main areas: tissue regeneration for cartilage, bone, muscle, tendon and neuronal cells; as cell vehicles for gene therapy; enhancement of hematopoietic stem cell engraftment; and treatment of immune diseases such as graft-versus-host disease, rheumatoid arthritis, experimental autoimmune encephalomyelitis, sepsis, acute pancreatitis and multiple sclerosis. In this review, the mechanisms of immunomodulatory effects of MSCs and examples of animal and clinical uses of their immunomodulatory effects are described.

Characterization of mouse clonal mesenchymal stem cell lines established by subfractionation culturing method

AIM

To characterize single-cell-derived mouse clonal mesenchymal stem cells (mcMSCs) established with bone marrow samples from three different mouse strains.

METHODS

We established mcMSC lines using subfractionation culturing method from bone marrow samples obtained from long bones. These lines were characterized by measuring cell growth, cell surface epitopes, differentiation potential, lineage-specific gene expression and T-cell suppression capability. Nonclonal MSCs isolated by the conventional gradient centrifugation method were used as controls.

RESULTS

All mcMSC lines showed typical nonclonal MSC-like spindle shape morphology. Lines differed in optimal growth density requirement. Cell surface epitope profiles of these mcMSC lines were similar to those of nonclonal MSCs. However, some lines exhibited different expression levels in a few epitopes, such as CD44 and CD105. Differentiation assays showed that 90% of the mcMSC lines were capable of differentiating into adipogenic and/or chondrogenic lineages, but only 20% showed osteogenic lineage differentiation. T-cell suppression analysis showed that 75% of the lines exhibited T-cell suppression capability.

CONCLUSION

mcMSC lines have similar cell morphology and cell growth rate but exhibit variations in their cell surface epitopes, differentiation potential, lineage-specific gene expression and T-cell suppression capability.

Human bone marrow-derived clonal mesenchymal stem cells inhibit inflammation and reduce acute pancreatitis in rats

BACKGROUND & AIMS

Acute pancreatitis (AP) has a high mortality rate; repetitive AP induces chronic AP and pancreatic adenocarcinoma. Mesenchymal stem cells (MSCs) have immunoregulatory effects and reduce inflammation. We developed a protocol to isolate human bone marrow-derived clonal MSCs (hcMSCs) from bone marrow aspirate and investigated the effects of these cells in rat models of mild and severe AP.

METHODS

Mild AP was induced in Sprague-Dawley rats by 3 intraperitoneal injections of cerulein (100 μg/kg), given at 2-hour intervals; severe AP was induced by intraparenchymal injection of 3% sodium taurocholate solution. hcMSCs were labeled with CM-1,1'-dioctadecyl-3,3,3'-tetramethylindo-carbocyanine perchloride and administered to rats through the tail vein.

RESULTS

hcMSCs underwent self-renewal and had multipotent differentiation capacities and immunoregulatory functions. Greater numbers of infused hcMSCs were detected in pancreas of rats with mild and severe AP than of control rats. Infused hcMSCs reduced acinar-cell degeneration, pancreatic edema, and inflammatory cell infiltration in each model of pancreatitis. The hcMSCs reduced expression of inflammation mediators and cytokines in rats with mild and severe AP. hcMSCs suppressed the mixed lymphocyte reaction and increased expression of Foxp3(+) (a marker of regulatory T cells) in cultured rat lymph node cells. Rats with mild or severe AP that were given infusions of hcMSCs had reduced numbers of CD3(+) T cells and increased expression of Foxp3(+) in pancreas tissues.

CONCLUSIONS

hcMSCs reduced inflammation and damage to pancreatic tissue in a rat model of AP; they reduced levels of cytokines and induced numbers of Foxp3(+) regulatory T cells. hcMSCs might be developed as a cell therapy for pancreatitis.

Mesenchymal stromal cells for steroid-refractory acute graft-versus-host disease: a report of two cases

Severe graft-versus-host disease (GVHD) is a lethal complication of allogeneic hematopoietic stem cell transplantation (HSCT). However, there have been only a few limited therapeutic options for the treatment of GVHD. Here we have reported two cases of the patients with acute steroid-refractory GVHD who underwent allogeneic HSCT. These patients received infusions of third-party clonal mesenchymal stem cells (cMSCs), which were isolated by a subfractionation culturing method (SCM) developed recently by our group, and showed marked improvement of the disease. MSCs represent a new potential therapeutic option in the treatment of steroid-refractory acute GVHD. They showed safety and improved clinical findings of the acute GVHD patients. However, further investigations are needed to understand the accurate mechanisms of MSCs and larger well-designed human clinical trials are necessary to prove further the safety and efficacy of the cMSCs for the treatment of acute GVHD patients.

Introducing transcription factors to multipotent mesenchymal stem cells: making transdifferentiation possible

Multipotent mesenchymal stem cells (MSCs) represent a promising autologous source for regenerative medicine. Because MSCs can be isolated from adult tissues, they represent an attractive cell source for autologous transplantation. A straightforward therapeutic strategy in the field of stem cell-based regenerative medicine is the transplantation of functional differentiated cells as cell replacement for the lost or defective cells affected by disease. However, this strategy requires the capacity to regulate stem cell differentiation toward the desired cell fate. This therapeutic approach assumes the capability to direct MSC differentiation toward diverse cell fates, including those outside the mesenchymal lineage, a process termed transdifferentiation. The capacity of MSCs to undergo functional transdifferentiation has been questioned over the years. Nonetheless, recent studies support that genetic manipulation can serve to promote transdifferentiation. Specifically, forced expression of certain transcription factors can lead to reprogramming and alter cell fate. Using such a method, fully differentiated lymphocytes have been reprogrammed to become macrophages and, remarkably, somatic cells have been reprogrammed to become embryonic stem-like cells. In this review, we discuss the past and current research aimed at transdifferentiating MSCs, a process with applications that could revolutionize regenerative medicine.