Epidermal Growth Factor as a Candidate for Ex Vivo Expansion of Bone Marrow-Derived Mesenchymal Stem Cells

Transplantation of autologous bone marrow-derived mononuclear cells into cerebrospinal fluid in a canine model of spinal cord injury

Introduction

Spinal cord injury (SCI) is associated with severe dysfunction of nervous tissue, and repair via the transplantation of bone marrow-derived mononuclear cells (BM-MNCs) into cerebrospinal fluid yields promising results. It is essential to understand the underlying mechanisms; therefore, this study aimed to evaluate the regenerative potential of autologous BM-MNC transplantation in a canine model of acute SCI.

Methods

Six dogs were included in this study, and SCI was induced using an epidural balloon catheter between L2 and L3, particularly in the area of the anterior longitudinal ligament. BM-MNC transplantation was performed, and T2-weighted magnetic resonance imaging (MRI) was conducted at specific time points (i.e., immediately after inducing SCI and at 1, 2, and 4 weeks after inducing SCI); moreover, the expression of growth-associated protein 43 (GAP-43) was evaluated.

Results

MRI revealed that the signal intensity reduced over time in both BM-MNC-treated and control groups. However, the BM-MNC-treated group exhibited a significantly faster reduction than the control group during the early stages of SCI induction (BM-MNC-treated group: 4.82 ± 0.135 cm [day 0], 1.71 ± 0.134 cm [1 week], 1.37 ± 0.036 cm [2 weeks], 1.21 cm [4 weeks]; control group: 4.96 ± 0.211 cm [day 0], 2.49 ± 0.570 cm [1 week], 1.56 ± 0.045 cm [2 weeks], 1.32 cm [4 weeks]). During the early stages of treatment, GAP-43 was significantly expressed at the proximal end of the injured spinal cord in the BM-MSC-treated group, whereas it was scarcely expressed in the control group.

Conclusions

In SCI, transplanted BM-MNCs can activate the expression of GAP-43, which is involved in axonal elongation (an important process in spinal cord regeneration). Thus, cell therapy with BM-MNCs can provide favorable outcomes in terms of better regenerative capabilities compared with other therapies.

Biodegradable and Non-Biodegradable Biomaterials and Their Effect on Cell Differentiation

Biomaterials for tissue scaffolds are key components in modern tissue engineering and regenerative medicine. Targeted reconstructive therapies require a proper choice of biomaterial and an adequate choice of cells to be seeded on it. The introduction of stem cells, and the transdifferentiation procedures, into regenerative medicine opened a new era and created new challenges for modern biomaterials. They must not only fulfill the mechanical functions of a scaffold for implanted cells and represent the expected mechanical strength of the artificial tissue, but furthermore, they should also assure their survival and, if possible, affect their desired way of differentiation. This paper aims to review how modern biomaterials, including synthetic (i.e., polylactic acid, polyurethane, polyvinyl alcohol, polyethylene terephthalate, ceramics) and natural (i.e., silk fibroin, decellularized scaffolds), both non-biodegradable and biodegradable, could influence (tissue) stem cells fate, regulate and direct their differentiation into desired target somatic cells.

Epidermal growth factor signalling pathway in endochondral ossification: an evidence-based narrative review

During endochondral bone development, a complex process that leads to the formation of the majority of skeletal elements, mesenchymal cells condense, differentiating into chondrocytes and producing the foetal growth plate. Chondrocytes progressively hypertrophy, induce angiogenesis and are then gradually replaced by bone. Epidermal Growth Factor (EGF), one of many growth factors, is the prototype of the EGF-ligand family, which comprises several proteins involved in cell proliferation, migration and survival. In bone, EGF pathway signalling finely tunes the first steps of chondrogenesis by maintaining mesenchymal cells in an undifferentiated stage, and by promoting hypertrophic cartilage replacement. Moreover, EGF signalling modulates bone homeostasis by stimulating osteoblast and osteoclast proliferation, and by regulating osteoblast differentiation under specific spatial and temporal conditions. This evidence-based narrative review describes the EGF pathway in bone metabolism and endochondral bone development. This comprehensive description may be useful in light of possible clinical applications in orthopaedic practice. A deeper knowledge of the role of EGF in bone may be useful in musculoskeletal conditions which may benefit from the modulation of this signalling pathway.Key messagesThe EGF pathway is involved in bone metabolism.EGF signalling is essential in the very early stages of limb development by maintaining cells in an undifferentiated stage.EGF pathway positively regulates chondrocyte proliferation, negatively modulates hypertrophy, and favours cartilage replacement by bone.EGF and EGF-like proteins finely tune the proliferation and differentiation of bone tissue cells, and they also regulate the initial phases of endochondral ossification.

miRNA-126 Inhibits Osteogenic Differentiation of Rat Bone Marrow Mesenchymal Stem Cells (BMSCs)

This study was to determine whether microRNA (miRNA)-126 regulates osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs). Rat BMSCs were extracted and stimulated for osteogenic differentiation. Functional experiments were conducted to assess miR-126’s impact on BMSCs differentiation. Western blot and RT-qPCR determined miR-126 expression. ALP activity detection and alizarin red staining detection were also performed. After osteogenic differentiation of BMSCs, miR-126 expression was gradually decreased over time. Overexpression of miR-26 decreased ALP activity, Notch signaling activity as well as declined Runx2 expression and calcium Salt nodules after treatment. Importantly, we found that Smad4 serves as a target of miR-126 while upregulation of the miRNA was accompanied with the decreased Smad4 protein expression without affecting the Smad4 mRNA level. In conclusion, miR-126 restrains osteogenic differentiation through inhibition of SMAD4 signaling, providing a novel insight into the mechanism.

Transcriptome Sequencing Reveals Key Genes in Three Early Phases of Osteogenic, Adipogenic, and Chondrogenic Differentiation of Bone Marrow Mesenchymal Stem Cells in Rats

Bone mesenchymal stem cells (BMSCs) of multi-directional differentiation and reproductive activity are attractive candidates for bone and cartilage repair. However, the molecular mechanisms underlying the early phase of osteogenesis, adipogenesis, and chondrogenesis of BMSCs are still far from understood. In the current study, BMSCs are isolated from rats, and the gene expressions during the initiation of differentiation (phase I), lineage acquisition (phase II), and early lineage progression (phase III) of three-directional differentiation of BMSCs were detected by using high-throughput sequencing. Then, 356, 540, and 299 differentially expressed genes (DEGs) were identified in phases I, II, and III of osteogenesis, respectively. The numbers are 507, 287, and 428 for adipogenesis, respectively, and 412, 336, and 513 for chondrogenesis, respectively. Time-dependent expression patterns of genes were also validated during three-directional differentiation in BMSCs. Hub genes including Ccna2, Cdc20, and Il6 may act as common participants in initiating osteogenesis, adipogenesis, and chondrogenesis. Mex3b, Sertad1, and Hopx showed an enhanced expression throughout three early phases during the osteogenic differentiation but no significant change in other two-directional differentiation. A similar pattern of Dtx4 and Ibsp expression occurred in adipogenesis and chondrogenesis, respectively. Our findings will help understand the underlying mechanism determining the differentiation fate of BMSCs and provide theoretical support for the clinical treatment of osteoporosis, osteoarthritis, and other age-related bone diseases.

Transcriptome Sequencing Reveals Key Genes in Three Early Phases of Osteogenic, Adipogenic, and Chondrogenic Differentiation of Bone Marrow Mesenchymal Stem Cells in Rats

Bone mesenchymal stem cells (BMSCs) of multi-directional differentiation and reproductive activity are attractive candidates for bone and cartilage repair. However, the molecular mechanisms underlying the early phase of osteogenesis, adipogenesis, and chondrogenesis of BMSCs are still far from understood. In the current study, BMSCs are isolated from rats, and the gene expressions during the initiation of differentiation (phase I), lineage acquisition (phase II), and early lineage progression (phase III) of three-directional differentiation of BMSCs were detected by using high-throughput sequencing. Then, 356, 540, and 299 differentially expressed genes (DEGs) were identified in phases I, II, and III of osteogenesis, respectively. The numbers are 507, 287, and 428 for adipogenesis, respectively, and 412, 336, and 513 for chondrogenesis, respectively. Time-dependent expression patterns of genes were also validated during three-directional differentiation in BMSCs. Hub genes including Ccna2, Cdc20, and Il6 may act as common participants in initiating osteogenesis, adipogenesis, and chondrogenesis. Mex3b, Sertad1, and Hopx showed an enhanced expression throughout three early phases during the osteogenic differentiation but no significant change in other two-directional differentiation. A similar pattern of Dtx4 and Ibsp expression occurred in adipogenesis and chondrogenesis, respectively. Our findings will help understand the underlying mechanism determining the differentiation fate of BMSCs and provide theoretical support for the clinical treatment of osteoporosis, osteoarthritis, and other age-related bone diseases.

Cytological Effects of Serum Isolated from Polytraumatized Patients on Human Bone Marrow-Derived Mesenchymal Stem Cells

Due to their immunomodulatory and regenerative capacity, human bone marrow-derived mesenchymal stem cells (hBMSCs) are promising in the treatment of patients suffering from polytrauma. However, few studies look at the effects of sera from polytraumatized patients on hBMSCs. The aim of this study was to explore changes in hBMSC properties in response to serum from polytrauma patients taken at different time points after the trauma incident. For this, sera from 84 patients with polytrauma (collected between 2010 and 2020 in our department) were used. In order to test the differential influence on hBMSC, sera from the 1^st (D1), 5^th (D5), and 10^th day (D10) after polytrauma were pooled, respectively. As a control, sera from three healthy donors (HS), matched with respect to age and gender to the polytrauma group, were collected. Furthermore, hBMSCs from four healthy donors were used in the experiments. The pooled sera of HS, D1, D5, and D10 were analyzed by multicytokine array for pro-/anti-inflammatory cytokines. Furthermore, the influence of the different sera on hBMSCs with respect to cell proliferation, colony forming unit-fibroblast (CFU-F) assay, cell viability, cytotoxicity, cell migration, and osteogenic and chondrogenic differentiation was analyzed. The results showed that D5 serum significantly reduced hBMSC cell proliferation capacity compared with HS and increased the proportion of dead cells compared with D1. However, the frequency of CFU-F was not reduced in polytrauma groups compared with HS, as well as the other parameters. The serological effect of polytrauma on hBMSCs was related to the time after trauma. It is disadvantageous to use BMSCs in polytraumatized patients at least until the fifth day after polytrauma as obvious cytological changes could be found at that time point. However, it is promising to use hBMSCs to treat polytrauma after five days, combined with the concept of “Damage Control Orthopedics” (DCO).

Dermal Mesenchymal Stem Cells from Psoriatic Lesions Stimulate HaCaT Cell Proliferation, Differentiation, and Migration via Activating the PI3K/AKT Signaling Pathway

BACKGROUND

Psoriasis is a chronic inflammatory skin disease characterized by excessive proliferation and abnormal differentiation of keratinocytes. Dermal mesenchymal stem cells (DMSCs) are not only involved in the regeneration of skin tissue, but also can regulate skin microenvironment by secreting cytokines. However, whether and how psoriatic DMSCs regulate proliferation and differentiation of keratinocytes remains unknown.

OBJECTIVE

To study the effects of psoriatic DMSCs on the proliferation, differentiation, and migration of keratinocytes and the underlying mechanisms.

METHODS

Following co-cultures of HaCaT cells with either psoriatic DMSCs (p-DMSCs) or DMSCs from normal volunteers (n-DMSCs), HaCaT cell proliferation was assessed using CCK-8 and EDU incorporation assay, while scratch assay and transwell assay were used to assess cell migration. qRT-PCR was used to determine expression levels of mRNA for cell proliferation (Ki-67) and differentiation (keratin 5, involucrin, and filaggrin). Western blot was used to measure expression levels of proteins associated with keratinocyte proliferation and differentiation in cultured HaCaT cells treated with or without PI3K inhibitor. ELISA assay was used to measure expression profile of stem cell factor (SCF), epidermal growth factor (EGF), and interleukin-11 (IL-11) within the co-culture supernatants.

RESULTS

The results showed that p-DMSCs displayed a higher potency than n-DMSCs in stimulating proliferation, differentiation, and migration of HaCaT cells. Expression levels of PI3K and AKT proteins were markedly increased in HaCaT cells co-cultured with DMSCs versus HaCaT cell culture alone. Moreover, inhibition of the PI3K/AKT signaling pathway reversed the effect of p-DMSCs on proliferation, differentiation, and migration of HaCaT cells. Compared with n-DMSCs, the p-DMSCs showed increased secretion of IL-11, EGF, and SCF.

CONCLUSION

p-DMSCs stimulate HaCaT cell proliferation, differentiation and migration via activating the PI3K/AKT signaling pathway, providing a new insight into the pathogenesis of psoriasis.

Comparative analysis of canine mesenchymal stem cells and bone marrow-derived mononuclear cells

Background and aim:

Mesenchymal stem cells (MSCs), which have multi-lineage differentiation potentials, are a promising source for regenerative medicine. However, the focus of study of MSCs is shifting from the characterization of the differentiation potential to their secretion potential for cell transplantation. Tissue regeneration and the attenuation of immune responses are thought to be affected by the secretion of multiple growth factors and cytokines by MSCs. However, the secretion potential of MSCs profiling remains incompletely characterized. In this study, we focused on the secretion ability related and protein mRNA expression of dog adipose tissue-derived MSCs (AT-MSC), bone marrow (BM)-derived MSCs, and BM-derived mononuclear cells (BM-MNC).

Materials and Methods:

Real-time polymerase chain reaction analyses revealed mRNA expression of nine growth factors and seven interleukins in these types of cells and three growth factors protein expression were determined using Enzyme-linked immunosorbent assay.

Results:

For the BM-MNC growth factors, the mRNA expression of transforming growth factor-β (TGF-β) was the highest. For the BM-derived MSC (BM-MSC) and AT-MSC growth factors, the mRNA expression of vascular endothelial growth factor (VEGF) was highest. BM-MSCs and AT-MSCs showed similar expression profiles. In contrast, BM-MNCs showed unique expression profiles for hepatocyte growth factor and epidermal growth factor. The three types of cells showed a similar expression of TGF-β.

Conclusion:

We conclude that expression of cytokine proteins and mRNAs suggests involvement in tissue repair and protection.

Potential Osteoinductive Effects of Hydroxyapatite Nanoparticles on Mesenchymal Stem Cells by Endothelial Cell Interaction

Nano-hydroxyapatite (nano-HA) has attracted substantial attention in the field of regenerative medicine. Endothelial cell (EC)-mesenchymal stem cell (MSC) interactions are necessary for bone reconstruction, but the manner in which nano-HA interacts in this process remains unknown. Herein, we investigated the cytotoxicity and osteoinductive effects of HA nanoparticles (HANPs) on MSCs using an indirect co-culture model mediated by ECs and highlighted the underlying mechanisms. It was found that at a subcytotoxic dose, HANPs increased the viability and expression of osteoblast genes, as well as mineralized nodules and alkaline phosphatase production of MSCs. These phenomena relied on HIF-1α secreted by ECs, which triggered the ERK1/2 signaling cascade. In addition, a two-stage cell-lineage mathematical model was established to quantitatively analyze the impact of HIF-1α on the osteogenic differentiation of MSCs. It demonstrated that HIF-1α exerted a dose-dependent stimulatory effect on the osteogenic differentiation rate of MSCs up to 1500 pg/mL, which was in agreement with the above results. Our data implied that cooperative interactions between HANPs, ECs, and MSCs likely serve to stimulate bone regeneration. Furthermore, the two-stage cell-lineage model is helpful in vitro system for assessing the potential influence of effector molecules in bone tissue engineering.

Towards Physiologic Culture Approaches to Improve Standard Cultivation of Mesenchymal Stem Cells

Mesenchymal stem cells (MSCs) are of great interest for their use in cell-based therapies due to their multipotent differentiation and immunomodulatory capacities. In consequence of limited numbers following their isolation from the donor tissue, MSCs require extensive expansion performed in traditional 2D cell culture setups to reach adequate amounts for therapeutic use. However, prolonged culture of MSCs in vitro has been shown to decrease their differentiation potential and alter their immunomodulatory properties. For that reason, preservation of these physiological characteristics of MSCs throughout their in vitro culture is essential for improving the efficiency of therapeutic and in vitro modeling applications. With this objective in mind, many studies already investigated certain parameters for enhancing current standard MSC culture protocols with regard to the effects of specific culture media components or culture conditions. Although there is a lot of diversity in the final therapeutic uses of the cells, the primary stage of standard isolation and expansion is imperative. Therefore, we want to review on approaches for optimizing standard MSC culture protocols during this essential primary step of in vitro expansion. The reviewed studies investigate and suggest improvements focused on culture media components (amino acids, ascorbic acid, glucose level, growth factors, lipids, platelet lysate, trace elements, serum, and xenogeneic components) as well as culture conditions and processes (hypoxia, cell seeding, and dissociation during passaging), in order to preserve the MSC phenotype and functionality during the primary phase of in vitro culture.

A Shaking-Culture Method for Generating Bone Marrow Derived Mesenchymal Stromal/Stem Cell-Spheroids With Enhanced Multipotency in vitro

Mesenchymal stromal/stem cells (MSCs), which generally expand into adherent monolayers, readily lose their proliferative and multilineage potential following repeated passages. Floating culture systems can be used to generate MSC spheroids, which are expected to overcome limitations associated with conventional adherent cultures while facilitating scaffold-free cell transplantation. However, the phenotypic characteristics of spheroids after long-term culture are unknown. In addition, regenerative therapies require new culture systems to maintain their undifferentiated state. In this study, we established a novel culture method employing three-dimensional (3D) “shaking” to generate MSC spheroids using bone marrow derived MSCs. Floating 3D cultures of mouse or human MSCs formed spheroids after shaking (85–95 rpm), within 1 month. These spheroids maintained their osteogenic-, adipogenic-, and chondrogenic-differentiation capacity. The adipogenic-differentiation capacity of adherent cultured mouse and human MSCs, which is lost following several passages, was remarkedly restored by shaking-culture. Notably, human MSC spheroids exhibited a renewable “undifferentiated MSC-pool” property, wherein undifferentiated MSCs grew from spheroids seeded repeatedly on a plastic culture dish. These data suggest that the shaking-culture method maintains and restores multipotency that is lost following monolayer expansion and thereby shows potential as a promising strategy for regenerative therapies with mesenchymal tissues.

Comparative Serum Analyses Identify Cytokines and Hormones Commonly Dysregulated as Well as Implicated in Promoting Osteolysis in MMP-2-Deficient Mice and Children

Deficiency of matrix metalloproteinase 2 (MMP-2) causes a complex syndrome characterized by multicentric osteolysis, nodulosis, and arthropathy (MONA) as well as cardiac valve defects, dwarfism and hirsutism. MMP-2 deficient (Mmp2 ^-/-) mice are a model for this rare multisystem pediatric syndrome but their phenotype remains incompletely characterized. Here, we extend the phenotypic characterization of MMP-2 deficiency by comparing the levels of cytokines and chemokines, soluble cytokine receptors, angiogenesis factors, bone development factors, apolipoproteins and hormones in mice and humans. Initial screening was performed on an 8-year-old male presenting a previously unreported deletion mutation c1294delC (Arg432fs) in the MMP2 gene and diagnosed with MONA. Of eighty-one serum biomolecules analyzed, eleven were upregulated (>4-fold), two were downregulated (>4-fold) and sixty-eight remained unchanged, compared to unaffected controls. Specifically, Eotaxin, GM-CSF, M-CSF, GRO-α, MDC, IL-1β, IL-7, IL-12p40, MIP-1α, MIP-1β, and MIG were upregulated and epidermal growth factor (EGF) and ACTH were downregulated in this patient. Subsequent analysis of five additional MMP-2 deficient patients confirmed the upregulation in Eotaxin, IL-7, IL-12p40, and MIP-1α, and the downregulation in EGF. To establish whether these alterations are bona fide phenotypic traits of MMP-2 deficiency, we further studied Mmp2 ^-/- mice. Among 32 cytokines measured in plasma of Mmp2 ^-/- mice, the cytokines Eotaxin, IL-1β, MIP-1α, and MIG were commonly upregulated in mice as well as patients with MMP-2 deficiency. Moreover, bioactive cortisol (a factor that exacerbates osteoporosis) was also elevated in MMP-2 deficient mice and patients. Among the factors we have identified to be dysregulated in MMP-2 deficiency many are osteoclastogenic and could potentially contribute to bone disorder in MONA. These new molecular phenotypic traits merit being targeted in future research aimed at understanding the pathological mechanisms elicited by MMP-2 deficiency in children.

The Role of the Microenvironment in Controlling the Fate of Bioprinted Stem Cells

The field of tissue engineering and regenerative medicine has made numerous advances in recent years in the arena of fabricating multifunctional, three-dimensional (3D) tissue constructs. This can be attributed to novel approaches in the bioprinting of stem cells. There are expansive options in bioprinting technology that have become more refined and specialized over the years, and stem cells address many limitations in cell source, expansion, and development of bioengineered tissue constructs. While bioprinted stem cells present an opportunity to replicate physiological microenvironments with precision, the future of this practice relies heavily on the optimization of the cellular microenvironment. To fabricate tissue constructs that are useful in replicating physiological conditions in laboratory settings, or in preparation for transplantation to a living host, the microenvironment must mimic conditions that allow bioprinted stem cells to proliferate, differentiate, and migrate. The advances of bioprinting stem cells and directing cell fate have the potential to provide feasible and translatable approach to creating complex tissues and organs. This review will examine the methods through which bioprinted stem cells are differentiated into desired cell lineages through biochemical, biological, and biomechanical techniques.

Designing topographically textured microparticles for induction and modulation of osteogenesis in mesenchymal stem cell engineering

Mesenchymal stem cells are the focus of intense research in bone development and regeneration. The potential of microparticles as modulating moieties of osteogenic response by utilizing their architectural features is demonstrated herein. Topographically textured microparticles of varying microscale features are produced by exploiting phase-separation of a readily soluble sacrificial component from polylactic acid. The influence of varying topographical features on primary human mesenchymal stem cell attachment, proliferation and markers of osteogenesis is investigated. In the absence of osteoinductive supplements, cells cultured on textured microparticles exhibit notably increased expression of osteogenic markers relative to conventional smooth microparticles. They also exhibit varying morphological, attachment and proliferation responses. Significantly altered gene expression and metabolic profiles are observed, with varying histological characteristics in vivo. This study highlights how tailoring topographical design offers cell-instructive 3D microenvironments which allow manipulation of stem cell fate by eliciting the desired downstream response without use of exogenous osteoinductive factors.

Endogenous cell recruitment strategy for articular cartilage regeneration

In the absence of timely and proper treatments, injuries to articular cartilage (AC) can lead to cartilage degeneration and ultimately result in osteoarthritis. Regenerative medicine and tissue engineering techniques are emerging as promising approaches for AC regeneration and repair. Although the use of cell-seeded scaffolds prior to implantation can regenerate and repair cartilage lesions to some extent, these approaches are still restricted by limited cell sources, excessive costs, risks of disease transmission and complex manufacturing practices. Recently developed acellular scaffold approaches that rely on the recruitment of endogenous cells to the injured sites avoid these drawbacks and offer great promise for in situ AC regeneration. Multiple endogenous stem/progenitor cells (ESPCs) are found in joint-resident niches and have the capability to migrate to sites of injury to participate in AC regeneration. However, the natural recruitment of ESPCs is insufficient, and the local microenvironment is hostile after injury. Hence, an endogenous cell recruitment strategy based on the combination of chemoattractants and acellular scaffolds to effectively and specifically recruit ESPCs and improve local microenvironment may provide new insights into in situ AC regeneration. This review provides a brief overview of: (1) the status of endogenous cell recruitment strategy; (2) the subpopulations, potential migration routes (PMRs) of joint-resident ESPCs and their immunomodulatory and reparative effects; (3) chemoattractants and their potential adverse effects; (4) scaffold-based drug delivery systems (SDDSs) that are utilized for in situ AC regeneration; and (5) the challenges and future perspectives of endogenous cell recruitment strategy for AC regeneration. STATEMENT OF SIGNIFICANCE: Although the endogenous cell recruitment strategy for articular cartilage (AC) regeneration has been investigated for several decades, much work remains to be performed in this field. Future studies should have the following aims: (1) reporting the up-to-date progress in the endogenous cell recruitment strategies; (2) determining the subpopulations of ESPCs, the cellular and molecular mechanisms underlying the migration of these cells and their anti-inflammatory, immunomodulatory and reparative effects; (3) elucidating the chemoattractants that enhance ESPC recruitment and their potential adverse effects; and (4) developing advanced SDDSs for chemoattractant dispatch. Herein, we present a systematic overview of the aforementioned issues to provide a better understanding of endogenous cell recruitment strategies for AC regeneration and repair.

Extrinsic modulation of integrin α6 and progenitor cell behavior in mesenchymal stem cells

Mesenchymal stem cells (MSC) are heterogeneous cells of complex nature that show different potentials while different culture conditions can modify their functionalities through interactions with the microenviroment. Here, we found that bone marrow (BM) MSC from different donor sources and passages that expressed higher levels of α6 integrin subunit (ITGA6), showed higher clonogenicity, migration and differentiation potential. ITGA6 showed important roles improving these potentials and regulating proliferation through protein kinase B (AKT) pathway and cell cycle inhibitor proteins p53 and p21. Moreover, ITGA6 downregulation impaired migration. Cell confluence regulated ITGA6, increasing its expression in low density cultures and decreasing in high density cultures. Besides, ITGA6- cells expressed ITGA6 when seeded at low densities. We found higher ITGA6 expression on fibronectin substrates at lower confluency. Fibronectin increased proliferation, clonogenicity, activation of AKT, decreased cell cycle inhibitor proteins and augmented growth factors expression. Spheres-derived MSC showed higher ITGA6 expression and enhanced potentials for migration, clonogenicity and proliferation. In conclusion, though there is an intrinsic regulation of ITGA6 expression, associated to the progenitor potential of BM-MSC, this expression is regulated by culture conditions and is translated in changes in cell behavior and proliferation. This knowledge could be used to enhance the potential of BM-MSC for clinical application.

BMP9 is a potential therapeutic agent for use in oral and maxillofacial bone tissue engineering

Oral and maxillofacial surgery is often challenging due to defective bone healing owing to the microbial environment of the oral cavity, the additional involvement of teeth and esthetic concerns. Insufficient bone volume as a consequence of aging and some oral and maxillofacial surgical procedures, such as tumor resection of the jaw, may further impact facial esthetics and cause the failure of certain procedures, such as oral and maxillofacial implantation. Bone morphogenetic protein (BMP) 9 (BMP9) is one of the most effective BMPs to induce the osteogenic differentiation of different stem cells. A large cross-talk network that includes the BMP9, Wnt/β, Hedgehog, EGF, TGF-β and Notch signaling pathways finely regulates osteogenesis induced by BMP9. Epigenetic control during BMP9-induced osteogenesis is mainly dependent on histone deacetylases (HDACs), microRNAs (miRNAs) and long noncoding RNAs (lncRNAs), which adds another layer of complexity. As a result, all these factors work together to orchestrate the molecular and cellular events underlying BMP9-related tissue engineering. In this review, we summarize our current understanding of the SMAD-dependent and SMAD-independent BMP9 pathways, with a particular focus on cross-talk and cross-regulation between BMP9 and other major signaling pathways in BMP9-induced osteogenesis. Furthermore, recently discovered epigenetic regulation of BMP9 pathways and the molecular and cellular basis of the application of BMP9 in tissue engineering in current oral and maxillofacial surgery and other orthopedic-related clinical settings are also discussed.

A novel role of angiotensin II in epidermal cell lineage determination: Angiotensin II promotes the differentiation of mesenchymal stem cells into keratinocytes through the p38 MAPK, JNK and JAK2 signalling pathways

BACKGROUND

Recent evidence suggests that angiotensin II (Ang II) plays a role in cutaneous wound healing. Mesenchymal stem cells (MSCs) are known as a rich source of cells that re-establish healed skin. However, the potential impact of Ang II on MSC differentiation into keratinocytes is still unknown.

OBJECTIVE

The present study was conducted to explore the effect of Ang II on the differentiation of bone marrow-derived MSCs (BM-MSCs) into keratinocytes.

METHODS

Bone marrow-derived MSCs were isolated from rat bone marrow and cultured. The expression of Ang II type 1 (AT₁ ) and type 2 (AT₂ ) receptors was examined by immunofluorescence staining. The differentiation of BM-MSCs into keratinocytes was investigated by flow cytometry or/and histological observation.

RESULTS

The BM-MSCs constitutively expressed both AT₁ and AT₂ receptors. The differentiation of BM-MSCs into keratinocytes was successfully induced. Interestingly, incubation of BM-MSCs with Ang II further promoted the differentiation of BM-MSCs into keratinocyte, which was abolished by pretreament with losartan, an AT₁ receptor antagonist, but not by PD123319, an AT₂ receptor antagonist. Moreover, the p38 mitogen-activated protein kinase (MAPK) inhibitor SB203580, the c-Jun N-terminal kinase (JNK) inhibitor SP600125 and the Janus-activated kinase (JAK)2 inhibitor AG490 suppressed Ang II-induced differentiation of BM-MSCs into keratinocytes. The phosphoinositide-3 kinase (PI3K) inhibitor wortmannin and MEK1/2 inhibitor U0126 had no effect on BM-MSC differentiation into keratinocytes.

CONCLUSIONS

Our data demonstrated for the first time that Ang II plays a promotive role in the differentiation of BM-MSC into keratinocytes through the AT₁ receptor, and that the p38 MAPK, JNK and JAK2 signalling pathways are involved in this process.

A Small-Sized Population of Human Umbilical Cord Blood-Derived Mesenchymal Stem Cells Shows High Stemness Properties and Therapeutic Benefit

Mesenchymal stem cells (MSCs) represent a promising means to promote tissue regeneration. However, the heterogeneity of MSCs impedes their use for regenerative medicine. Further investigation of this phenotype is required to develop cell therapies with improved clinical efficacy. Here, a small-sized population of human umbilical cord blood-derived MSCs (UCB-MSCs) was isolated using a filter and centrifuge system to analyze its stem cell characteristics. Consequently, this population showed higher cell growth and lower senescence. Additionally, it exhibited diverse stem cell properties including differentiation, stemness, and adhesion, as compared to those of the population before isolation. Using cell surface protein array or sorting analysis, both EGFR and CD49f were identified as markers associated with the small-sized population. Accordingly, suppression of these surface proteins abolished the superior characteristics of this population. Moreover, compared to that with large or nonisolated populations, the small-sized population showed greater therapeutic efficacy by promoting the engraftment potential of infused cells and reducing lung damage in an emphysema mouse model. Therefore, the isolation of this small-sized population of UCB-MSCs could be a simple and effective way to enhance the efficacy of cell therapy.

Advances of Stem Cell-Laden Hydrogels With Biomimetic Microenvironment for Osteochondral Repair

Osteochondral damage from trauma or osteoarthritis is a general joint disease that can lead to an increased social and economic burden in the modern society. The inefficiency of osteochondral defects is mainly due to the absence of suitable tissue-engineered substrates promoting tissue regeneration and replacing damaged areas. The hydrogels are becoming a promising kind of biomaterials for tissue regeneration. The biomimetic hydrogel microenvironment can be tightly controlled by modulating a number of biophysical and biochemical properties, including matrix mechanics, degradation, microstructure, cell adhesion, and intercellular interactions. In particular, advances in stem cell-laden hydrogels have offered new ideas for the cell therapy and osteochondral repair. Herein, the aim of this review is to underpin the importance of stem cell-laden hydrogels on promoting the development of osteochondral regeneration, especially in the field of manipulation of biomimetic microenvironment and utilization growth factors with various delivery methods.

Different approaches for transformation of mesenchymal stem cells into hepatocyte-like cells

Due to the prominent role of the liver in the body and detoxification, its functionality can be affected in an irreversible manner by diseases. This phenomenon renders the liver to stop working, leading to morbidity and mortality. Therefore, liver transplantation is the only way to tackle this issue.In order to compensate for the lack of adequate healthy liver tissue for transplantation, therapeutic approaches such as hepatocyte transplantation have been proposed as an alternative. Recognizing the fact that mesenchymal stem cells are adult stem cells with the capacity to differentiate into several cell types, different methods have been invented to produce hepatocyte-like cells from mesenchymal stem cells. They can be divided into three main categories, such as addition of cytokines and growth factors, genetic modifications, and adjustment of microenvironment as well as physical parameters.In this review, we attempted to introduce diverse efficient methods for differentiating mesenchymal stem cells and their capability for transformation into hepatocyte-like cells.

The superiority of conditioned medium derived from rapidly expanded mesenchymal stem cells for neural repair

Background

Spinal cord injury (SCI) is a complex and severe neurological condition. Mesenchymal stem cells (MSCs) and their secreted factors show promising potential for regenerative medicine. Many studies have investigated MSC expansion efficacy of all kinds of culture medium formulations, such as growth factor-supplemented or xeno-free medium. However, very few studies have focused on the potential of human MSC (hMSC) culture medium formulations for injured spinal cord repair. In this study, we investigated the effect of hMSC-conditioned medium supplemented with bFGF, EGF, and patient plasma, namely, neural regeneration laboratory medium (NRLM), on SCI in vitro and in vivo.

Methods

Commercial and patient bone marrow hMSCs were obtained for cultivation in standard medium and NRLM separately. Several characteristics, including CD marker expression, differentiation, and growth curves, were compared between MSCs cultured in standard medium and NRLM. Additionally, we investigated the effect of the conditioned medium (referred to as NRLM-CM) on neural repair, including inflammation inhibition, neurite regeneration, and spinal cord injury (SCI), and used a coculture system to detect the neural repair function of NRLM-MSCs.

Results

Compared to standard culture medium, NRLM-CM had superior in inflammation reduction and neurite regeneration effects in vitro and improved functional restoration in SCI rats in vivo. In comparison with standard culture medium MSCs, NRLM-MSCs proliferated faster regardless of the age of the donor. NRLM-MSCs also showed increased adipose differentiative potential and reduced CD90 expression. Both types of hMSC CM effectively enhanced injured neurite outgrowth and protected against H₂O₂ toxicity in spinal cord neuron cultures. Cytokine arrays performed in hMSC-CM further revealed the presence of at least 120 proteins. Among these proteins, 6 demonstrated significantly increased expression in NRLM-CM: adiponectin (Acrp30), angiogenin (ANG), HGF, NAP-2, uPAR, and IGFBP2.

Conclusions

The NRLM culture system provides rapid expansion effects and functional hMSCs. The superiority of the derived conditioned medium on neural repair shows potential for future clinical applications.

MiR-33a Controls hMSCS Osteoblast Commitment Modulating the Yap/Taz Expression Through EGFR Signaling Regulation

Mesenchymal stromal cells (hMSCs) display a pleiotropic function in bone regeneration. The signaling involved in osteoblast commitment is still not completely understood, and that determines the failure of current therapies being used. In our recent studies, we identified two miRNAs as regulators of hMSCs osteoblast differentiation driving hypoxia signaling and cytoskeletal reorganization. Other signalings involved in this process are epithelial to mesenchymal transition (EMT) and epidermal growth factor receptor (EGFR) signalings through the regulation of Yes-associated protein (YAP)/PDZ-binding motif (TAZ) expression. In the current study, we investigated the role of miR-33a family as a (i) modulator of YAP/TAZ expression and (ii) a regulator of EGFR signaling during osteoblast commitments. Starting from the observation on hMSCs and primary osteoblast cell lines (Nh-Ost) in which EMT genes and miR-33a displayed a specific expression, we performed a gain and loss of function study with miR-33a-5p and 3p on hMSCs cells and Nh-Ost. After 24 h of transfections, we evaluated the modulation of EMT and osteoblast genes expression by qRT-PCR, Western blot, and Osteoimage assays. Through bioinformatic analysis, we identified YAP as the putative target of miR-33a-3p. Its role was investigated by gain and loss of function studies with miR-33a-3p on hMSCs; qRT-PCR and Western blot analyses were also carried out. Finally, the possible role of EGFR signaling in YAP/TAZ modulation by miR-33a-3p expression was evaluated. Human MSCs were treated with EGF-2 and EGFR inhibitor for different time points, and qRT-PCR and Western blot analyses were performed. The above-mentioned methods revealed a balance between miR-33a-5p and miR-33a-3p expression during hMSCs osteoblast differentiation. The human MSCs phenotype was maintained by miR-33a-5p, while the maintenance of the osteoblast phenotype in the Nh-Ost cell model was permitted by miR-33a-3p expression, which regulated YAP/TAZ through the modulation of EGFR signaling. The inhibition of EGFR blocked the effects of miR-33a-3p on YAP/TAZ modulation, favoring the maintenance of hMSCs in a committed phenotype. A new possible personalized therapeutic approach to bone regeneration was discussed, which might be mediated by customizing delivery of miR-33a in simultaneously targeting EGFR and YAP signaling with combined use of drugs.

Defective Proliferation and Osteogenic Potential with Altered Immunoregulatory phenotype of Native Bone marrow-Multipotential Stromal Cells in Atrophic Fracture Non-Union

Bone marrow-Multipotential stromal cells (BM-MSCs) are increasingly used to treat complicated fracture healing e.g., non-union. Though, the quality of these autologous cells is not well characterized. We aimed to evaluate bone healing-related capacities of non-union BM-MSCs. Iliac crest-BM was aspirated from long-bone fracture patients with normal healing (U) or non-united (NU). Uncultured (native) CD271highCD45low cells or passage-zero cultured BM-MSCs were analyzed for gene expression levels, and functional assays were conducted using culture-expanded BM-MSCs. Blood samples were analyzed for serum cytokine levels. Uncultured NU-CD271highCD45low cells significantly expressed fewer transcripts of growth factor receptors, EGFR, FGFR1, and FGRF2 than U cells. Significant fewer transcripts of alkaline phosphatase (ALPL), osteocalcin (BGLAP), osteonectin (SPARC) and osteopontin (SPP1) were detected in NU-CD271^highCD45^low cells. Additionally, immunoregulation-related markers were differentially expressed between NU- and U-CD271^highCD45^low cells. Interestingly, passage-zero NU BM-MSCs showed low expression of immunosuppressive mediators. However, culture-expanded NU and U BM-MSCs exhibited comparable proliferation, osteogenesis, and immunosuppression. Serum cytokine levels were found similar for NU and U groups. Collectively, native NU-BM-MSCs seemed to have low proliferative and osteogenic capacities; therefore, enhancing their quality should be considered for regenerative therapies. Further research on distorted immunoregulatory molecules expression in BM-MSCs could potentially benefit the prediction of complicated fracture healing.

Reactive Oxygen Species (ROS), Intimal Thickening, and Subclinical Atherosclerotic Disease

Arteriosclerosis causes significant morbidity and mortality worldwide. Central to this process is the development of subclinical non-atherosclerotic intimal lesions before the appearance of pathologic intimal thickening and advanced atherosclerotic plaques. Intimal thickening is associated with several risk factors, including oxidative stress due to reactive oxygen species (ROS), inflammatory cytokines and lipid. The main ROS producing systems in-vivo are reduced nicotinamide dinucleotide phosphate (NADPH) oxidase (NOX). ROS effects are context specific. Exogenous ROS induces apoptosis and senescence, whereas intracellular ROS promotes stem cell differentiation, proliferation, and migration. Lineage tracing studies using murine models of subclinical atherosclerosis have revealed the contributory role of medial smooth muscle cells (SMCs), resident vascular stem cells, circulating bone-marrow progenitors and endothelial cells that undergo endothelial-mesenchymal-transition (EndMT). This review will address the putative physiological and patho-physiological roles of ROS in controlling vascular cell fate and ROS contribution to vascular regeneration and disease progression.

Spermatogenesis Recovery Potentials after Transplantation of Adipose Tissue-Derived Mesenchymal Stem Cells Cultured with Growth Factors in Experimental Azoospermic Mouse Models

Objective

Approximately 1% of the male population suffers from obstructive or non-obstructive azoospermia. Previous in vitro studies have successfully differentiated mesenchymal stem cells (MSCs) into germ cells. Because of immune- modulating features, safety, and simple isolation, adipose tissue-derived MSCs (AT-MSCs) are good candidates for such studies. However, low availability is the main limitation in using these cells. Different growth factors have been investigated to overcome this issue. In the present study, we aimed to comparatively assess the performance of AT-MSCs cultured under the presence or absence of three different growth factors, epidermal growth factor (EGF), leukemia inhibitory factor (LIF) and glial cell line-derived neurotrophic factor (GDNF), following transplantation in testicular torsion-detorsion mice

Materials and Methods

This was an experimental study in which AT-MSCs were first isolated from male Naval Medical Research Institute (NMRI) mice. Then, the mice underwent testicular torsion-detorsion surgery and received bromodeoxyuridine (BrdU)-labeled AT-MSCs into the lumen of seminiferous tubules. The transplanted cells had been cultured in different conditioned media, containing the three growth factors and without them. The expression of germ cell-specific markers was evaluated with real-time polymerase chain reaction (PCR) and western-blot. Moreover, immunohistochemical staining was used to trace the labeled cells.

Results

The number of transplanted AT-MSCs resided in the basement membrane of seminiferous tubules significantly increased after 8 weeks. The expression levels of Gcnf and Mvh genes in the transplanted testicles by AT-MSCs cultured in the growth factors-supplemented medium was greater than those in the control group (P<0.001 and P<0.05, respectively). The expression levels of the c-Kit and Scp3 genes did not significantly differ from the control group.

Conclusion

Our findings showed that the use of EGF, LIF and GDNF to culture AT-MSCs can be very helpful in terms of MSC survival and localization.

The role of EGFR signaling in age-related osteoporosis in mouse cortical bone

So far, there has been no effective cure for osteoporotic cortical bone, the most significant change in long bone structure during aging and the main cause of bone fragility fractures, because its underlying molecular and cellular mechanisms remain largely unknown. We used 3- and 15-mo-old mice as well as 15-mo-old mice treated with vehicle and gefitinib to evaluate structural, cellular, and molecular changes in cortical bone. We found that the senescence of osteoprogenitors was increased, whereas the expression of phosphorylated epidermal growth factor receptor (EGFR) on the endosteal surface of cortical bone down-regulated in middle-aged 15-mo-old mice compared with young 3-mo-old mice. Further decreasing EGFR signaling by gefitinib treatment in middle-aged mice resulted in promoted senescence of osteoprogenitors and accelerated cortical bone degeneration. Moreover, inhibiting EGFR signaling suppressed the expression of enhancer of zeste homolog 2 (Ezh2), the repressor of cell senescence-inducer genes, through ERK1/2 pathway, thereby promoting senescence in osteoprogenitors. Down-regulated EGFR signaling plays a physiologically significant role during aging by reducing Ezh2 expression, leading to the senescence of osteoprogenitors and the decline in bone formation on the endosteal surface of cortical bone.-Liu, G., Xie, Y., Su, J., Qin, H., Wu, H., Li, K., Yu, B., Zhang, X. The role of EGFR signaling in age-related osteoporosis in mouse cortical bone.

Survival and immunomodulation of stem cells from human extracted deciduous teeth expanded in pooled human and foetal bovine sera

The immunomodulatory properties of mesenchymal stem cells (MSCs) from autologous and allogeneic sources are useful in stimulating tissue regeneration and repair. To obtain a high number of MSCs for transplantation requires extensive in vitro expansion with culture media supplements that can cause xeno-contamination of cells potentially compromising function and clinical outcomes. In this study stem cells from human extracted deciduous teeth (SHED) were cultured in Knockout™ DMEM supplemented with either pooled human serum (pHS) or foetal bovine serum (FBS) to compare their suitability in maintaining immunomodulatory properties of cells during in vitro expansion. No significant difference in cell survival of SHED grown in pHS (pHS-SHED) or FBS (FBS-SHED) was observed when co-cultured with complement, monocytes or lymphocytes. However, significant changes in the expression of sixteen paracrine factors involved in immunomodulation were observed in the supernatants of FBS-SHED co-cultures with monocytes or lymphocytes compared to that in pHS-SHEDs after both 24 and 120 h of incubation. Further analysis of changing protein levels of paracrine factors in co-cultures using biological pathway analysis software predicted upregulation of functions associated with immunogenicity in FBS-SHED and lymphocyte co-cultures compared to pHS-SHED co-cultures. Pathway analysis also predicted significant stimulation of HMGB1 and TREM1 signalling pathways in FBS-SHED co-cultures indicating activation of immune cells and inflammation. Though FBS supplementation does not impact survival of SHED, our combinatorial biological pathway analysis supports the idea that in vitro expansion of SHEDs in pHS provides optimal conditions to minimise xeno-contamination and inflammation and maintain their immunomodulatory properties.

Continuous zebularine treatment enhances hepatic differentiation of mesenchymal stem cells under liver-specific factors induction in vitro

AIMS

To investigate the effect of zebularine, a stable inhibitor of DNA methylation, on hepatic differentiation of bone marrow-derived mesenchymal stem cells (BM-MSCs) under liver-specific factors induction in vitro.

MAIN METHODS

BM-MSCs were isolated from the mononuclear cell fraction of rabbit bone marrow samples. The identification of these cells was carried out by immunophenotype analysis. The three hepatic differentiation protocols of BM-MSCs were as follows: liver-specific factors (hepatocyte growth factor and epidermal growth factor) without zebularine, liver-specific factors combined with a 24 h zebularine pre-treatment, and liver-specific factors combined with continuous zebularine treatment. BM-MSCs cultured in basic medium without the differentiation stimuli were set as the control. Morphological features, liver-specific gene and protein expression, and functional analyses were assessed to evaluate hepatic differentiation of BM-MSCs. Global DNA methylation status was tested for investigating the underlying mechanism.

KEY FINDINGS

Flow cytometry immunophenotyping proved the isolated cells with plastic adherence and a spindle shape were CD29, CD90 positive and CD34, CD45 negative. Albumin (ALB) and alpha-fetoprotein (AFP) messenger RNA and protein expression, glycogen storage and urea production were significantly higher in the continuous zebularine-treated group than the other groups while the differences between the zebularine-untreated group and 24 h zebularine pre-treated group were not significant. Meanwhile, significant decrease of global DNA methylation was observed in the continuous zebularine-treated group.

SIGNIFICANCE

We conclude that continuous zebularine treatment can improve hepatic differentiation of BM-MSCs under liver-specific factors induction in vitro, and the decrease of global DNA methylation maybe involved in this process.

Improved ex vivo expansion of mesenchymal stem cells on solubilized acellular fetal membranes

Coatings produced from extracellular matrixes (ECMs) have emerged as promising surfaces for the improved ex vivo expansion of mesenchymal stem cells (MSCs). However, identifying a readily available source of ECM to generate these coatings is currently the bottleneck of this technology. In this study, we assessed if ECM coatings derived from decellularized fetal membranes were a suitable substrate for MSC expansion. We separated and decellularized the two main components of the fetal membranes, the amnion and the chorion. Characterization of the decellularized membranes revealed that each membrane component has a distinct composition, implying that coatings produced from these materials would have unique biological properties. The membranes were processed further to produce solubilized forms of the decellularized amniotic membrane (s-dAM) and decellularized chorionic membrane (s-dCM). On s-dAM coatings decidual MSCs (DMSC) were more proliferative than those cultured on tissue culture plastic alone or on Matrigel coatings; were smaller in size (a measure of MSC potency); exhibited greater adipogenic differentiation capacity; and improved osteogenic capacity. Additionally, long term culture studies showed late passage DMSCs (passage 8) cultured on s-dAM showed a decrease in cell diameter over three passages. These data support the use of s-dAM as a substrate for improved MSC expansion. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 107A: 232-242, 2019.

Epidermal growth factor can signal via β-catenin to control proliferation of mesenchymal stem cells independently of canonical Wnt signalling

Bone marrow mesenchymal stem/stromal cells (MSCs) maintain bone homeostasis and repair through the ability to expand in response to mitotic stimuli and differentiate into skeletal lineages. Signalling mechanisms that enable precise control of MSC function remain unclear. Here we report that by initially examining differences in signalling pathway expression profiles of individual MSC clones, we identified a previously unrecognised signalling mechanism regulated by epidermal growth factor (EGF) in primary human MSCs. We demonstrate that EGF is able to activate β-catenin, a key component of the canonical Wnt signalling pathway. EGF is able to induce nuclear translocation of β-catenin in human MSCs but does not drive expression of Wnt target genes or T cell factor (TCF) activity in MSC reporter cell lines. Using an efficient Design of Experiments (DoE) statistical analysis, with different combinations and concentrations of EGF and Wnt ligands, we were able to confirm that EGF does not influence the Wnt/β-catenin pathway in MSCs. We show that the effects of EGF on MSCs are temporally regulated to initiate early “classical” EGF signalling mechanisms (e.g via mitogen activated protein kinase) with delayed activation of β-catenin. By RNA-sequencing, we identified gene sets that were exclusively regulated by the EGF/β-catenin pathway, which were distinct from classical EGF-regulated genes. However, subsets of classical EGF gene targets were significantly influenced by EGF/β-catenin activation. These signalling pathways cooperate to enable EGF-mediated proliferation of MSCs by alleviating the suppression of cell cycle pathways induced by classical EGF signalling.

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Epidermal growth factor (EGF) controls mesenchymal stem cell (MSC) proliferation.

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EGF signals through β-catenin in MSCs but not in related fibroblastic cells.

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Classical EGF and EGF/β-catenin cooperatively regulate distinct gene sets in MSCs.

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EGF/β-catenin enables MSC proliferation by alleviating cell cycle suppression.

Effect of Different Preconditioning Regimens on the Expression Profile of Murine Adipose-Derived Stromal/Stem Cells

Stem cell-based therapies require cells with a maximum regenerative capacity in order to support regeneration after tissue injury and organ failure. Optimization of this regenerative potential of mesenchymal stromal/stem cells (MSC) or their conditioned medium by in vitro preconditioning regimens are considered to be a promising strategy to improve the release of regenerative factors. In the present study, MSC were isolated from inguinal adipose tissue (mASC) from C57BL/6 mice, cultured, and characterized. Then, mASC were either preconditioned by incubation in a hypoxic environment (0.5% O₂), or in normoxia in the presence of murine epidermal growth factor (EGF) or tumor necrosis factor α (TNFα) for 48 h. Protein expression was measured by a commercially available array. Selected factors were verified by PCR analysis. The expression of 83 out of 308 proteins (26.9%) assayed was found to be increased after preconditioning with TNFα, whereas the expression of 61 (19.8%) and 70 (22.7%) proteins was increased after incubation with EGF or in hypoxia, respectively. Furthermore, we showed the proliferation-promoting effects of the preconditioned culture supernatants on injured epithelial cells in vitro. Our findings indicate that each preconditioning regimen tested induced an individual expression profile with a wide variety of factors, including several growth factors and cytokines, and therefore may enhance the regenerative potential of mASC for cell-based therapies.

Reproductive stage and sex steroid hormone levels influence the expression of mesenchymal stromal cell (MSC) markers in the equine endometrium

Mesenchymal stem or stromal cells (MSCs) play key roles in tissue homeostasis. In the cyclic equine endometrium, this may be regulated by changes in serum concentrations of sex steroid hormones. This study was designed to investigate the changes in endometrial expression of MSC markers during reproductive cycles in mares and the influence of sex steroid hormones on endometrial MSC proliferation in vitro. Endometrial biopsies were collected from pony mares at different reproductive stages (estrus; day 5 and 13 after ovulation; seasonal anestrus; 20 h and 7days post-partum; n = 5 per stage) and were analyzed by RT-qPCR. MSC (CD29, CD44, CD73, CD90, CD105) and perivascular (CD146, NG2) markers were present in all samples irrespective of reproductive stage. Transcript levels of most markers were present at lowest levels on day 5 after ovulation and at 20 h post-partum. MSCs isolated from endometrial tissue (n = 6 mares) were cultured in the presence of progesterone (0.01-100 μM) and estradiol 17β (0.1-1 μM), and cell proliferation was analyzed using alamarBlue^® assay. Relative to cells incubated in steroid-depleted media, both progesterone and estradiol 17β moderately increased cell proliferation (1.1- and 1.2-fold, respectively) independently of the concentration used. In conclusion, our results suggest that levels of MSC markers in equine endometrium dynamically change across reproductive cycles and that MSC populations are in part regulated by sex steroids.

ErbB2 promotes endothelial phenotype of human left ventricular epicardial highly proliferative cells (eHiPC)

The adult human heart contains a subpopulation of highly proliferative cells. The role of ErbB receptors in these cells has not been studied. From human left ventricular (LV) epicardial biopsies, we isolated highly proliferative cells (eHiPC) to characterize the cell surface expression and function of ErbB receptors in the regulation of cell proliferation and phenotype. We found that human LV eHiPC express all four ErbB receptor subtypes. However, the expression of ErbB receptors varied widely among eHiPC isolated from different subjects. eHiPC with higher cell surface expression of ErbB2 reproduced the phenotype of endothelial cells and were characterized by endothelial cell-like functional properties. We also found that EGF/ErbB1 induces VEGFR2 expression, while ligands for both ErbB1 and ErbB3/4 induce expression of Tie2. The number of CD31posCD45neg endothelial cells is higher in LV biopsies from subjects with high ErbB2 (ErbB2high) eHiPC compared to low ErbB2 (ErbB2low) eHiPC. These findings have important implications for potential strategies to increase the efficacy of cell-based revascularization of the injured heart, through promotion of an endothelial phenotype in cardiac highly proliferative cells.

Stem Cells from Human Extracted Deciduous Teeth Expanded in Foetal Bovine and Human Sera Express Different Paracrine Factors After Exposure to Freshly Prepared Human Serum

BACKGROUND

The response of stem cells to paracrine factors within the host's body plays an important role in the regeneration process after transplantation. The aim of this study was to determine the viability and paracrine factor profile of stem cells from human extracted deciduous teeth (SHED) pre-cultivated in media supplemented with either foetal bovine serum (FBS) or pooled human serum (pHS) in the presence of individual human sera (iHS).

METHODS

SHED (n = 3) from passage 4 were expanded in FBS (FBS-SHED) or pHS (pHS-SHED) supplemented media until passage 7. During expansion, the proliferation of SHED was determined. Cells at passage 7 were further expanded in human serum from four individual donors (iHS) for 120 h followed by assessment of cell viability and profiling of the secreted paracrine factors.

RESULTS

Proliferation of SHED was significantly higher (p < 0.05) in pHS supplemented media compared to FBS supplemented media. pHS-SHED also maintained their higher proliferation rate compared to FBS-SHED in the presence of iHS. In iHS supplemented media, FBS-SHED expressed significantly higher levels of SDF-1A (p < 0.05) after 24 h compared to pHS-SHED. Similar results were found for HGF (p < 0.01), LIF (p < 0.05), PDGF-BB (p < 0.05), SDF-1A (p < 0.01), and IL-10 (p < 0.05) when cell culture supernatants from FBS-SHED were profiled 120 h post-incubation.

CONCLUSION

SHED expanded in pHS instead of FBS have higher proliferative capacity and show an altered secretion profile. Further studies are needed to determine whether these differences could result in better engraftment and regeneration following transplantation.

Key-genes regulating the liposecretion process of mature adipocytes

White mature adipocytes (MAs) are plastic cells able to reversibly transdifferentiate toward fibroblast-like cells maintaining stem cell gene signatures. The main morphologic aspect of this transdifferentiation process, called liposecretion, is the secretion of large lipid droplets and the development of organelles necessary for exocrine secretion. There is a considerable interest in the adipocyte plastic properties involving liposecretion process, but the molecular details are incompletely explored. This review analyzes the gene expression of MAs isolated from human subcutaneous fat tissue with respect to bone marrow (BM)-derived mesenchymal stem cells (MSC) focusing on gene regulatory pathways involved into cellular morphology changes, cellular proliferation and transports of molecules through the membrane, suggesting potential ways to guide liposecretion. In particular, Wnt, MAPK/ERK, and AKT pathways were accurately described, studying up- and down-stream molecules involved. Moreover, adipogenic extra- and intra-cellular interactions were analyzed studying the role of CDH2, CDH11, ITGA5, E-Syt1, PAI-1, IGF1, and INHBB genes. Additionally, PLIN1 and PLIN2 could be key-genes of liposecretion process regulating molecules transport through the membrane. All together data demonstrated that liposecretion is regulated through a complex molecular networks that are able to respond to microenvironment signals, cytokines, and growth factors. Autocrine as well as external signaling molecules might activate liposecretion affecting adipocytes physiology.

Isolation and prolonged expansion of oral mesenchymal stem cells under clinical-grade, GMP-compliant conditions differentially affects "stemness" properties

Background

Development of clinical-grade cell preparations is central to meeting the regulatory requirements for cellular therapies under good manufacturing practice-compliant (cGMP) conditions. Since addition of animal serum in culture media may compromise safe and efficient expansion of mesenchymal stem cells (MSCs) for clinical use, this study aimed to investigate the potential of two serum/xeno-free, cGMP culture systems to maintain long-term “stemness” of oral MSCs (dental pulp stem cells (DPSCs) and alveolar bone marrow MSCs (aBMMSCs)), compared to conventional serum-based expansion.

Methods

DPSC and aBMMSC cultures (n = 6/cell type) were established from pulp and alveolar osseous biopsies respectively. Three culture systems were used: StemPro_MSC/SFM_XenoFree (Life Technologies); StemMacs_MSC/XF (Miltenyi Biotek); and α-MEM (Life Technologies) with 15% fetal bovine serum. Growth (population doublings (PDs)), immunophenotypic (flow cytometric analysis of MSC markers) and senescence (β-galactosidase (SA-β-gal) activity; telomere length) characteristics were determined during prolonged expansion. Gene expression patterns of osteogenic (ALP, BMP-2), adipogenic (LPL, PPAR-γ) and chondrogenic (ACAN, SOX-9) markers and maintenance of multilineage differentiation potential were determined by real-time PCR.

Results

Similar isolation efficiency and stable growth dynamics up to passage 10 were observed for DPSCs under all expansion conditions. aBMMSCs showed lower cumulative PDs compared to DPSCs, and when StemMacs was used substantial delays in cell proliferation were noted after passages 6–7. Serum/xeno-free expansion produced cultures with homogeneous spindle-shaped phenotypes, while serum-based expansion preserved differential heterogeneous characteristics of each MSC population. Prolonged expansion of both MSC types but in particular the serum/xeno-free-expanded aBMMSCs was associated with downregulation of CD146, CD105, Stro-1, SSEA-1 and SSEA-4, but not CD90, CD73 and CD49f, in parallel with an increase of SA-gal-positive cells, cell size and granularity and a decrease in telomere length. Expansion under both serum-free systems resulted in “osteogenic pre-disposition”, evidenced by upregulation of osteogenic markers and elimination of chondrogenic and adipogenic markers, while serum-based expansion produced only minor changes. DPSCs retained a diminishing (CCM, StemPro) or increasing (StemMacs) mineralization potential with passaging, while aBMMSCs lost this potential after passages 6–7 under all expansion conditions.

Conclusions

These findings indicate there is still a vacant role for development of qualified protocols for clinical-grade expansion of oral MSCs; a key milestone achievement for translation of research from the bench to clinics.

Electronic supplementary material

The online version of this article (doi:10.1186/s13287-017-0705-0) contains supplementary material, which is available to authorized users.

Omentin-1 effects on mesenchymal stem cells: proliferation, apoptosis, and angiogenesis in vitro

Background

Mesenchymal stem cells (MSCs) are emerging as an extremely promising therapeutic agent for tissue repair. However, limitations exist such as the low numbers of MSCs obtained from donors, and the poor survival and function of donor cells. Omentin-1, a new fat depot-specific secretory adipokine, exerts proproliferation, prosurvival, and proangiogenic functions in certain cells via an Akt-dependent mechanism; however, little is known about the influence of omentin-1 on MSCs.

Methods

MSCs were isolated from 60–80 g donor rats. Cell proliferation was assessed with CCK-8 and EdU assay. Cell cycle, apoptosis ratio, reactive oxygen species concentration, and mitochondrial membrane potential were detected by flow cytometry. Hoechst 33342 dye was used to assess morphological changes of apoptosis. Expression levels of Akt, FoxO3a, GSK-3β, and apoptosis- and cell cycle-associated proteins were detected by Western blotting. Tube formation assay was used to test the angiogenesis role of conditioned medium from MSCs in vitro. The cytokine secretion was assessed by ELISA.

Results

After treatment with omentin-1 (100–800 ng/ml), MSCs displayed a higher proliferative capacity with an increasing number of cells in the S and G2 phase of the cell cycle. Moreover, omentin-1 preconditioning for 1 h could protect MSCs against H₂O₂-induced apoptosis in a concentration-dependent manner. Furthermore, omentin-1 pretreatment reduced the excessive reactive oxygen species. Western blots revealed that increased Bcl-2 and decreased Bax appeared in MSCs after omentin-1 incubation, which inhibited the mitochondrial apoptosis pathways with evidence showing inhibition of caspase-3 cleavage and preservation of mitochondrial membrane potential. Omentin-1 could enhance angiogenic growth factor secretion and elevate the ability of MSCs to stimulate tube formation by human umbilical vein endothelial cells (HUVECs). Furthermore, omentin-1 enhanced Akt phosphorylation; however, blockade of the PI3K/Akt pathway with an inhibitor, LY294002 (20 μM), suppressed the above beneficial effects of omentin-1.

Conclusion

Omentin-1 can exert beneficial effects on MSCs by promoting proliferation, inhibiting apoptosis, increasing secretion of angiogenic cytokines, and enhancing the ability for stimulating tube formation by HUVECs via the PI3K/Akt signaling pathway. Thus, omentin-1 may be considered a candidate for optimizing MSC-based cell therapy.

Serum from CCl4-induced acute rat injury model induces differentiation of ADSCs towards hepatic cells and reduces liver fibrosis

Cellular therapies hold promise to alleviate liver diseases. This study explored the potential of allogenic serum isolated from rat with acute CCl₄ injury to differentiate adipose derived stem cells (ADSCs) towards hepatic lineage. Acute liver injury was induced by CCl₄ which caused significant increase in serum levels of VEGF, SDF1α and EGF. ADSCs were preconditioned with 3% serum isolated from normal and acute liver injury models. ADSCs showed enhanced expression of hepatic markers (AFP, albumin, CK8 and CK19). These differentiated ADSCs were transplanted intra-hepatically in CCl₄-induced liver fibrosis model. After one month of transplantation, fibrosis and liver functions (alkaline phosphatase, ALAT and bilirubin) showed marked improvement in acute injury group. Elevated expression of hepatic (AFP, albumin, CK 18 and HNF4a) and pro survival markers (PCNA and VEGF) and improvement in liver architecture as deduced from results of alpha smooth muscle actin, Sirius red and Masson's trichome staining was observed.

Enhanced Cell Growth of Adipocyte-Derived Mesenchymal Stem Cells Using Chemically-Defined Serum-Free Media

The multipotency and anti-inflammatory effects of mesenchymal stem cells (MSCs) make them attractive for cell therapy in regenerative medicine. A large number of MSCs is required for efficient therapy owing to the low homing efficiency of MSCs to target sites. Furthermore, owing to limitations in obtaining sufficient amounts of MSCs, in vitro expansion of MSCs that preserves their differentiation and proliferative potential is essential. The animal factor included in culture media also limits clinical application. In this study, adipose-derived MSCs showed a significantly higher proliferation rate in STK2, a chemically-defined medium, than in DMEM/FBS. The expression of MSC surface markers was increased in the culture using STK2 compared to that using DMEM/FBS. Tri-lineage differentiation analyses showed that MSCs cultured in STK2 were superior to those cultured in DMEM/FBS. In addition, MSCs cultured in STK2 showed a reduced senescence rate, small and homogenous cell size, and were more genetically stable compared to those cultured in DMEM/FBS. Furthermore, secretome analysis showed that the expression of factors related to proliferation/migration, anti-inflammation, and differentiation were increased in STK2 culture medium compared to DMEM/FBS. Taken together, these results suggest that culture using STK2 medium offers many advantages through which it is possible to obtain safer, superior, and larger numbers of MSCs.

Promising Therapeutic Strategies for Mesenchymal Stem Cell-Based Cardiovascular Regeneration: From Cell Priming to Tissue Engineering

The primary cause of death among chronic diseases worldwide is ischemic cardiovascular diseases, such as stroke and myocardial infarction. Recent evidence indicates that adult stem cell therapies involving cardiovascular regeneration represent promising strategies to treat cardiovascular diseases. Owing to their immunomodulatory properties and vascular repair capabilities, mesenchymal stem cells (MSCs) are strong candidate therapeutic stem cells for use in cardiovascular regeneration. However, major limitations must be overcome, including their very low survival rate in ischemic lesion. Various attempts have been made to improve the poor survival and longevity of engrafted MSCs. In order to develop novel therapeutic strategies, it is necessary to first identify stem cell modulators for intracellular signal triggering or niche activation. One promising therapeutic strategy is the priming of therapeutic MSCs with stem cell modulators before transplantation. Another is a tissue engineering-based therapeutic strategy involving a cell scaffold, a cell-protein-scaffold architecture made of biomaterials such as ECM or hydrogel, and cell patch- and 3D printing-based tissue engineering. This review focuses on the current clinical applications of MSCs for treating cardiovascular diseases and highlights several therapeutic strategies for promoting the therapeutic efficacy of MSCs in vitro or in vivo from cell priming to tissue engineering strategies, for use in cardiovascular regeneration.

Pooled Human Serum Increases Regenerative Potential of In Vitro Expanded Stem Cells from Human Extracted Deciduous Teeth

In regenerative therapy, in vitro expansion of stem cells is critical to obtain a significantly higher number of cells for successful engraftment after transplantation. However, stem cells lose its regenerative potential and enter senescence during in vitro expansion. In this study, the influence of foetal bovine serum (FBS) and pooled human serum (pHS) on the proliferation, morphology and migration of stem cells from human extracted deciduous teeth (SHED) was compared. SHED (n = 3) was expanded in KnockOut DMEM supplemented with either pHS (pHS-SM) or FBS (FBS-SM). pHS was prepared using peripheral blood serum of six healthy male adults, aged between 21 and 35 years old. The number of live SHED was significantly higher, from passage 5 to 7, when cultured in pHS-SM compared to those cultured in FBS-SM (p < 0.05). Number of cells having flattened morphology, characteristics of partially differentiated and senescent cells, was significantly lower (p < 0.05) in pHS-SM (3%) compared to those in FBS-SM (7%). Furthermore, migration of SHED in pHS-SM was found to be more directional. The presence of selected ten paracrine factors known for their proliferation and migration potential was detected in all six individual human sera, used to produce pHS, none of which were detected in FBS. Ingenuity Pathway Analysis showed the possible involvement of the 'ephrin receptor signalling pathway' to regulate the proliferation and migration of SHED in pHS-SM. In conclusion, pHS-SM showed significantly higher proliferation rate and could maintain significantly lower number of senescent cells and support directional migration of cells.

External factors influencing mesenchymal stem cell fate in vitro

Mesenchymal stem cells (MSCs) have extensive potentials, which make them attractive candidates for the developmental biology, drug discovery and regenerative medicine. However, the use of MSCs is limited by their scarceness in tissues and in culture conditions. They also exhibit various degrees of potency which subsequently influencing their applications. Nowadays, questions remain about how self-renewal and differentiation of MSCs can be controlled in vitro and in vivo, how they will behave and migrate to the right place and how they modulate the immune system. Therefore, identification of factors and culture conditions to affect the fate and function of MSCs may be effective to enhance their applications in clinical situations. Studies have indicated that the fate of MSCs in culture is influenced by various external factors, including the specific cell source, donor age, plating density, passage number and plastic surface quality. Some other factors such as cell culture media and their supplementary factors, O₂ concentration, mechano-/electro-stimuli and three-dimensional scaffolds are also shown to be influential. This review addresses the current state of MSC research for describing and discussing the findings about external factors that influence the fate and function of MSCs. Additionally, the new discoveries and suggestions regarding their molecular mechanisms will be explained.

EGFL7-overexpressing epidermal stem cells promotes fibroblast proliferation and migration via mediating cell adhesion and strengthening cytoskeleton

Epidermal growth factor (EGF)-like family members mediate a wide range of biological activities including cell proliferation and migration. Increasing evidence indicated that EGF plays an important role in the process of wound healing by stimulating fibroblast motility. The aim of this study was to see whether EGF-like domain 7 (EGFL7)-overexpressing epidermal stem cells (EGFL7-ESCs) would promote fibroblast proliferation and migration. We found that mRNA and protein levels of EGFL7 expression were significantly increased in EGFL7-ESCs. The protein expression of EGFL7 was significantly elevated in conditioned media (CM) of EGFL7-ESCs compared to ESCs CM or vector-ESCs CM. The cell count and cell viability of EGFL7-ESCs CM-treated fibroblasts were also significantly increased compared to control. In addition, EGFL7-ESCs CM-treated fibroblasts showed elevated migration compared with control. Moreover, the expressions of β1-integrin, β-tubulin, β-actin, and Vimentin were increased, while that of E-cadherin was decreased in EGFL7-ESCs CM-treated fibroblasts. These results indicate that EGFL7-ESCs contribute towards promoting fibroblast migration through enhancing cell adhesion, strengthening cytoskeleton, and reducing intercellular aggregation. These findings suggest that the stimulating effect of EGFL7-ESCs on fibroblast proliferation and migration may provide a useful strategy for wound healing.

Epidermal Growth Factor Induces Proliferation of Hair Follicle-Derived Mesenchymal Stem Cells Through Epidermal Growth Factor Receptor-Mediated Activation of ERK and AKT Signaling Pathways Associated with Upregulation of Cyclin D1 and Downregulation of p16

The maintenance of highly proliferative capacity and full differentiation potential is a necessary step in the initiation of stem cell-based regenerative medicine. Our recent study showed that epidermal growth factor (EGF) significantly enhanced hair follicle-derived mesenchymal stem cell (HF-MSC) proliferation while maintaining the multilineage differentiation potentials. However, the underlying mechanism remains unclear. Herein, we investigated the role of EGF in HF-MSC proliferation. HF-MSCs were isolated and cultured with or without EGF. Immunofluorescence staining, flow cytometry, cytochemistry, and western blotting were used to assess proliferation, cell signaling pathways related to the EGF receptor (EGFR), and cell cycle progression. HF-MSCs exhibited surface markers of mesenchymal stem cells and displayed trilineage differentiation potentials toward adipocytes, chondrocytes, and osteoblasts. EGF significantly increased HF-MSC proliferation as well as EGFR, ERK1/2, and AKT phosphorylation (p-EGFR, p-ERK1/2, and p-AKT) in a time- and dose-dependent manner, but not STAT3 phosphorylation. EGFR inhibitor (AG1478), PI3K-AKT inhibitor (LY294002), ERK inhibitor (U0126), and STAT3 inhibitor (STA-21) significantly blocked EGF-induced HF-MSC proliferation. Moreover, AG1478, LY294002, and U0126 significantly decreased p-EGFR, p-AKT, and p-ERK1/2 expression. EGF shifted HF-MSCs at the G1 phase to the S and G2 phase. Concomitantly, cyclinD1, phosphorylated Rb, and E2F1expression increased, while that of p16 decreased. In conclusion, EGF induces HF-MSC proliferation through the EGFR/ERK and AKT pathways, but not through STAT-3. The G1/S transition was stimulated by upregulation of cyclinD1 and inhibition of p16 expression.