Epidermal growth factor (EGF) treatment on multipotential stromal cells (MSCs). Possible enhancement of therapeutic potential of MSC

Hedgehog signaling directs cell differentiation and plays a critical role in tendon enthesis healing

A high prevalence of rotator cuff tears presents a major clinical challenge. A better understanding of the molecular mechanisms underlying enthesis development and healing is needed for developing treatments. We recently identified hedgehog (Hh)-lineage cells critical for enthesis development and repair. This study revealed cell-cell communication within the Hh-lineage cell population. To further characterize the role of Hh signaling, we used mouse models to activate and inactivate the Hh pathway in enthesis progenitors. Activation of Hh target genes during enthesis development increased its mineralization and mechanical properties. Activation of Hh signaling at the injured mature enthesis promoted fibrocartilage formation, enhanced mineralization, and increased expression of chondrogenic and osteogenic markers, which implies that Hh signaling drives cell differentiation to regenerate the damaged enthesis. Conversely, deletion of Hh target genes impaired enthesis healing. In summary, this study revealed a new strategy for enthesis repair via activation of Hh signaling in endogenous cells.

Efficacy of chemically induced human hepatic progenitor cells from diseased liver against nonalcoholic steatohepatitis model

BACKGROUND

Numerous chemical reprogramming techniques have been reported, rendering them applicable to regenerative medicine research. The aim of our study was to evaluate the therapeutic potential of human CLiP derived from clinical specimens transplanted into a nonalcoholic steatohepatitis (NASH) mouse model of liver fibrosis.

METHODS

We successfully generated chemically induced liver progenitor (CLiP), which exhibited progenitor-like characteristics, through stimulation with low-molecular-weight compounds. We elucidated their cell differentiation ability and therapeutic effects. However, the therapeutic efficacy of human CLiP generated from clinical samples on liver fibrosis, such as liver cirrhosis, remains unproven.

RESULTS

Following a 4 week period, transplanted human CLiP in the NASH model differentiated into mature hepatocytes and demonstrated suppressive effects on liver injury markers (i.e., aspartate transaminase and alanine transaminase). Although genes related to inflammation and fat deposition did not change in the human CLiP transplantation group, liver fibrosis-related factors (Acta2 and Col1A1) showed suppressive effects on gene expression following transplantation, with approximately a 60% reduction in collagen fibers. Importantly, human CLiP could be efficiently induced from hepatocytes isolated from the cirrhotic liver, underscoring the feasibility of using autologous hepatocytes to produce human CLiP.

CONCLUSION

Our findings demonstrate the effectiveness of human CLiP transplantation as a viable cellular therapy for liver fibrosis, including NASH liver. These results hold promise for the development of liver antifibrosis therapy utilizing human CLiP within the field of liver regenerative medicine.

A distinct "repair" role of regulatory T cells in fracture healing

Regulatory T cells (Tregs) suppress immune responses and inflammation. Here, we described the distinct nonimmunological role of Tregs in fracture healing. The recruitment from the circulation pool, peripheral induction, and local expansion rapidly enriched Tregs in the injured bone. The Tregs in the injured bone displayed superiority in direct osteogenesis over Tregs from lymphoid organs. Punctual depletion of Tregs compromised the fracture healing process, which leads to increased bone nonunion. In addition, bone callus Tregs showed unique T-cell receptor repertoires. Amphiregulin was the most overexpressed protein in bone callus Tregs, and it can directly facilitate the proliferation and differentiation of osteogenic precursor cells by activation of phosphatidylinositol 3-kinase/protein kinase B signaling pathways. The results of loss- and gain-function studies further evidenced that amphiregulin can reverse the compromised healing caused by Treg dysfunction. Tregs also enriched in patient bone callus and amphiregulin can promote the osteogenesis of human pre-osteoblastic cells. Our findings indicate the distinct and nonredundant role of Tregs in fracture healing, which will provide a new therapeutic target and strategy in the clinical treatment of fractures.

Fabricating Composite Cell Sheets for Wound Healing: Cell Sheets Based on the Communication Between BMSCs and HFSCs Facilitate Full-Thickness Cutaneous Wound Healing

BACKGROUND

Insufficient angiogenesis and the lack of skin appendages are critical challenges in cutaneous wound healing. Stem cell-fabricated cell sheets have become a promising strategy, but cell sheets constructed by a single cell type are inadequate to provide a comprehensive proregenerative microenvironment for wound tissue.

METHODS

Based on the communication between cells, in this study, bone marrow mesenchymal stem cells (BMSCs) and hair follicle stem cells (HFSCs) were cocultured to fabricate a composite cell sheet (H/M-CS) for the treatment of full-thickness skin wounds in mice.

RESULTS

Experiments confirmed that there is cell-cell communication between BMSCs and HFSCs, which enhances the cell proliferation and migration abilities of both cell types. Cell-cell talk also upregulates the gene expression of pro-angiogenic-related cytokines in BMSCs and pro-hair follicle-related cytokines in HFSCs, as well as causing changes in the properties of secreted extracellular matrix components.

CONCLUSIONS

Therefore, the composite cell sheet is more conducive for cutaneous wound healing and promoting the regeneration of blood vessels and hair follicles.

Investigation of the efficacy of epidermal growth factor, boric acid and their combination in cartilage injury in rats: An experimental study

OBJECTIVES

In this study, we aimed to determine the bioefficacy of epidermal growth factor (EGF), boric acid (BA), and their combination on cartilage injury in rats.

MATERIALS AND METHODS

In in vitro setting, the cytotoxic effects of BA, EGF, and their combinations using mouse fibroblast cell (L929), human bone osteosarcoma cell (Saos-2), and human adipose derived mesenchymal stem cells (hAD-MSCs) were determined by applying MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide] test. In in vivo setting, 72 rats were randomly divided into four groups. A standard chondral defect was created and microfracture was performed in all groups. Group A was determined as the control group. In addition to the standard procedure, Group B received 100 ng/mL of EGF, Group C received a combination of 100 ng/mL of EGF and 10 µg/mL of BA combination, and Group D 20 µg/mL of BA.

RESULTS

The cytotoxic effect of the combinations of EGF dilutions (1, 5, 10, 25, 50, 100, 200 ng/mL) with BA (100, 300, 500 µg/mL) was observed only in the 72-h application period and in Saos-2. The cytotoxic effect of BA was reduced when combined with EGF. There was no significant difference in the histopathological scores among the groups (p=0.13).

CONCLUSION

Our study showed that EGF and low-dose BA application had a positive effect on cartilage healing in rats. Significant decreases in recovery scores were observed in the other groups. The combination of EGF and BA promoted osteoblast growth. Detection of lytic lesions in the group treated with 20 µg/mL of BA indicates that BA may have a cytotoxic effect.

Mesenchymal stromal cells, metabolism, and mitochondrial transfer in bone marrow normal and malignant hematopoiesis

Hematopoietic stem cell (HSC) transplantation-based treatments are in different phases of clinical development, ranging from current therapies to a promise in the repair and regeneration of diseased tissues and organs. Mesenchymal stromal/stem cells (MSCs), which are fibroblast-like heterogeneous progenitors with multilineage differentiation (osteogenic, chondrogenic, and adipogenic) and self-renewal potential, and exist in the bone marrow (BM), adipose, and synovium, among other tissues, represent one of the most widely used sources of stem cells in regenerative medicine. MSCs derived from bone marrow (BM-MSCs) exhibit a variety of traits, including the potential to drive HSC fate and anti-inflammatory and immunosuppressive capabilities via paracrine activities and interactions with the innate and adaptive immune systems. The role of BM-MSC-derived adipocytes is more controversial and may act as positive or negative regulators of benign or malignant hematopoiesis based on their anatomical location and functional crosstalk with surrounding cells in the BM microenvironment. This review highlights the most recent clinical and pre-clinical findings on how BM-MSCs interact with the surrounding HSCs, progenitors, and immune cells, and address some recent insights on the mechanisms that mediate MSCs and adipocyte metabolic control through a metabolic crosstalk between BM microenvironment cells and intercellular mitochondrial transfer in normal and malignant hematopoiesis.

EGF, TGF-α and Amphiregulin Differently Regulate Endometrium-Derived Mesenchymal Stromal/Stem Cells

The prototypical receptor tyrosine kinase epidermal growth factor receptor (EGFR) is regulated by a set of its ligands, which determines the specificity of signaling and intracellular fate of the receptor. The EGFR signaling system is well characterized in immortalized cell lines such as HeLa derived from tumor tissues, but much less is known about EGFR function in untransformed multipotent stromal/stem cells (MSCs). We compared the effect of epidermal growth factor (EGF), transforming growth factor-α (TGF-α) and amphiregulin (AREG) on physiological responses in endometrial MSCs (enMSC) and HeLa cells. In addition, using Western blotting and confocal microscopy, we studied the internalization and degradation of EGFR stimulated by the three ligands in these cell lines. We demonstrated that unlike HeLa, EGF and TGF-α, but not AREG, stimulated enMSC proliferation and prevented decidual differentiation in an EGFR-dependent manner. In HeLa cells, EGF targeted EGFR for degradation, while TGF-α stimulated its recycling. Surprisingly, in enMSC, both ligands caused EGFR degradation. In both cell lines, AREG-EGFR internalization was not registered. In HeLa cells, EGFR was degraded within 2 h, restoring its level in 24 h, while in enMSC, degradation took more than 4-8 h, and the low EGFR level persisted for several days. This indicates that EGFR homeostasis in MSCs may differ significantly from that in immortalized cell lines.

Renal cancer secretome induces migration of mesenchymal stromal cells

BACKGROUND

Advanced renal cell carcinoma (RCC) is therapeutically challenging. RCC progression is facilitated by mesenchymal stem/stromal cells (MSCs) that exert remarkable tumor tropism. The specific mechanisms mediating MSCs' migration to RCC remain unknown. Here, we aimed to comprehensively analyze RCC secretome to identify MSCs attractants.

METHODS

Conditioned media (CM) were collected from five RCC-derived cell lines (Caki-1, 786-O, A498, KIJ265T and KIJ308T) and non-tumorous control cell line (RPTEC/TERT1) and analyzed using cytokine arrays targeting 274 cytokines in addition to global CM proteomics. MSCs were isolated from bone marrow of patients undergoing standard orthopedic surgeries. RCC CM and the selected recombinant cytokines were used to analyze their influence on MSCs migration and microarray-targeted gene expression. The expression of genes encoding cytokines was evaluated in 100 matched-paired control-RCC tumor samples.

RESULTS

When compared with normal cells, CM from advanced RCC cell lines (Caki-1 and KIJ265T) were the strongest stimulators of MSCs migration. Targeted analysis of 274 cytokines and global proteomics of RCC CM revealed decreased DPP4 and EGF, as well as increased AREG, FN1 and MMP1, with consistently altered gene expression in RCC cell lines and tumors. AREG and FN1 stimulated, while DPP4 attenuated MSCs migration. RCC CM induced MSCs' transcriptional reprogramming, stimulating the expression of CD44, PTX3 and RAB27B. RCC cells secreted hyaluronic acid (HA), a CD44 ligand mediating MSCs' homing to the kidney. AREG emerged as an upregulator of MSCs' transcription.

CONCLUSIONS

Advanced RCC cells secrete AREG, FN1 and HA to induce MSCs migration, while DPP4 loss prevents its inhibitory effect on MSCs homing. RCC secretome induces MSCs' transcriptional reprograming to facilitate their migration. The identified components of RCC secretome represent potential therapeutic targets.

Biopotentials of Collagen Scaffold Impregnated with Plant-Cell-Derived Epidermal Growth Factor in Defective Bone Healing

The combination of scaffolds with recombinant human epidermal growth factor (rhEGF) protein can enhance defective bone healing via synergistic activation to stimulate cellular growth, differentiation, and survival. We examined the biopotentials of an rhEGF-loaded absorbable collagen scaffold (ACS) using a mouse model of calvarial defects, in which the rhEGF was produced from a plant cell suspension culture system because of several systemic advantages. Here, we showed a successful and large-scale production of plant-cell-derived rhEGF protein (p-rhEGF) by introducing an expression vector that cloned with its cDNA under the control of rice α-amylase 3D promoter into rice calli (Oryza sativa L. cv. Dongjin). Implantation with p-rhEGF (5 μg)-loaded ACSs into critical-sized calvarial defects enhanced new bone formation and the expression of osteoblast-specific markers in the defected regions greater than implantation with ACSs alone did. The potency of p-rhEGF-induced bone healing was comparable with that of Escherichia coli-derived rhEGF protein. The exogenous addition of p-rhEGF increased the proliferation of human periodontal ligament cells and augmented the induction of interleukin 8, bone morphogenetic protein 2, and vascular endothelial growth factor in the cells. Collectively, this study demonstrates the successful and convenient production of p-rhEGF, as well as its potency to enhance ACS-mediated bone regeneration by activating cellular responses that are required for wound healing.

Hsa_circ_0008500 inhibits apoptosis of adipose-derived stem cells under high glucose through hsa-miR-1273h-5p/ELK1 axis

Preliminary researches have confirmed that the number of apoptosis of adipose tissue-derived stem cells (ADSCs) in patients with diabetes is significantly increased, leading to a difficult healing wound. Increasing researches revealed that circular RNAs (circRNAs) can control apoptosis. However, it is still unclear whether and how circRNAs are critical for regulating ADSCs apoptosis. In this study, we utilized in vitro model in which ADSCs were cultivated with normal glucose (NG) (5.5 mM) or high glucose (HG) (25 mM) medium, respectively, and found that more apoptotic ADSCs were observed in HG medium comparing to ADSCs in NG medium. Furthermore, we found that hsa_circ_0008500 attenuated HG-mediated ADSCs apoptosis. In addition, Hsa_circ_0008500 could directly interact with hsa-miR-1273h-5p, acting as a miRNA sponge, which subsequently suppressed Ets-like protein-1(ELK1) expression, the downstream target of hsa-miR-1273h-5p. Thus, these results indicated that targeting the hsa_circ_0008500/hsa-miR-1273h-5p/ELK1 signaling pathway in ADSCs may be a potential target for repairing diabetic wounds.

Administration of stem cells against cardiovascular diseases with a focus on molecular mechanisms: Current knowledge and prospects

Cardiovascular diseases (CVDs) are a serious global concern for public and human health. Despite the emergence of significant therapeutic advances, it is still the leading cause of death and disability worldwide. As a result, extensive efforts are underway to develop practical therapeutic approaches. Stem cell-based therapies could be considered a promising strategy for the treatment of CVDs. The efficacy of stem cell-based therapeutic approaches is demonstrated through recent laboratory and clinical studies due to their inherent regenerative properties, proliferative nature, and their capacity to differentiate into different cells such as cardiomyocytes. These properties could improve cardiovascular functioning leading to heart regeneration. The two most common types of stem cells with the potential to cure heart diseases are induced pluripotent stem cells (iPSCs) and mesenchymal stem cells (MSCs). Several studies have demonstrated the use, efficacy, and safety of MSC and iPSCs-based therapies for the treatment of CVDs. In this study, we explain the application of stem cells, especially iPSCs and MSCs, in the treatment of CVDs with a focus on cellular and molecular mechanisms and then discuss the advantages, disadvantages, and perspectives of using this technology in the treatment of these diseases.

Managing the Heterogeneity of Mesenchymal Stem Cells for Cartilage Regenerative Therapy: A Review

Articular cartilage defects commonly result from trauma and are associated with significant morbidity. Since cartilage is an avascular, aneural, and alymphatic tissue with a poor intrinsic healing ability, the regeneration of functional hyaline cartilage remains a difficult clinical problem. Mesenchymal stem cells (MSCs) are multipotent cells with multilineage differentiation potential, including the ability to differentiate into chondrocytes. Due to their availability and ease of ex vivo expansion, clinicians are increasingly applying MSCs in the treatment of cartilage lesions. However, despite encouraging pre-clinical and clinical data, inconsistencies in MSC proliferative and chondrogenic potential depending on donor, tissue source, cell subset, culture conditions, and handling techniques remain a key barrier to widespread clinical application of MSC therapy in cartilage regeneration. In this review, we highlight the strategies to manage the heterogeneity of MSCs ex vivo for more effective cartilage repair, including reducing the MSC culture expansion period, and selecting MSCs with higher chondrogenic potential through specific genetic markers, surface markers, and biophysical attributes. The accomplishment of a less heterogeneous population of culture-expanded MSCs may improve the scalability, reproducibility, and standardisation of MSC therapy for clinical application in cartilage regeneration.

Recent progress in the manipulation of biochemical and biophysical cues for engineering functional tissues

Tissue engineering (TE) is currently considered a cutting-edge discipline that offers the potential for developing treatments for health conditions that negatively affect the quality of life. This interdisciplinary field typically involves the combination of cells, scaffolds, and appropriate induction factors for the regeneration and repair of damaged tissue. Cell fate decisions, such as survival, proliferation, or differentiation, critically depend on various biochemical and biophysical factors provided by the extracellular environment during developmental, physiological, and pathological processes. Therefore, understanding the mechanisms of action of these factors is critical to accurately mimic the complex architecture of the extracellular environment of living tissues and improve the efficiency of TE approaches. In this review, we recapitulate the effects that biochemical and biophysical induction factors have on various aspects of cell fate. While the role of biochemical factors, such as growth factors, small molecules, extracellular matrix (ECM) components, and cytokines, has been extensively studied in the context of TE applications, it is only recently that we have begun to understand the effects of biophysical signals such as surface topography, mechanical, and electrical signals. These biophysical cues could provide a more robust set of stimuli to manipulate cell signaling pathways during the formation of the engineered tissue. Furthermore, the simultaneous application of different types of signals appears to elicit synergistic responses that are likely to improve functional outcomes, which could help translate results into successful clinical therapies in the future.

Mechanobiology of MicroRNAs in Intervertebral Disk Degeneration

Intervertebral disk degeneration (IDD) is an intricate pathological process contributing to one of the major causes of low back pain. The degradation of the extracellular matrix (ECM), inflammation, and apoptosis have all been investigated as critical factors involved in the pathology of degenerative disk disease. Additionally, the presence of aberrant microRNAs (miRNAs), conserved molecules that regulate the amount protein post-transcriptionally, may play a crucial role in the pathogenesis of IDD. Research regarding the dysfunction of miRNAs in IDD has been well researched over the past five years. Here, we provide a critical overview of the current knowledge of miRNAs, emphasizing the processes involved in the degenerative disk pathology.

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.

An update of current therapeutic approach for Intervertebral Disc Degeneration: A review article

Intervertebral disc degeneration is a natural process of aging. It can cause physical, psychological, and socioeconomic impact due to the decreasing function of the spine and pain manifestation. Conservative and surgical treatment to correct symptoms and structural anomalies does not fully recover the degenerated disc. Several therapeutic approaches have been developed to improve the clinical result and patient's quality of life. This paper aims to review previous studies that discussed potential novel approach in order to make effective degenerated disc restoration. We tried to briefly describe IVD, IDD, also review several promising current therapeutic approaches for degenerated disc treatment, including its relevance to the degeneration process and limitation to be applied in a clinical setting. There are generally four current therapeutic approaches that we reviewed; growth factors, small molecules, gene therapy, and stem cells. These new approaches aim to not only correct the symptoms but also restore and delay the degeneration process.

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Intervertebral Disc Degeneration.

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Current Therapeutic Approach.

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Stem Cell Therapy.

Electromagnetic field exposure as a plausible approach to enhance the proliferation and differentiation of mesenchymal stem cells in clinically relevant scenarios

Mesenchymal stem/stromal cell (MSC)‍-based therapy has been regarded as one of the most revolutionary breakthroughs in the history of modern medicine owing to its myriad of immunoregulatory and regenerative properties. With the rapid progress in the fields of osteo- and musculoskeletal therapies, the demand for MSC-based treatment modalities is becoming increasingly prominent. In this endeavor, researchers around the world have devised new and innovative techniques to support the proliferation of MSCs while minimizing the loss of hallmark features of stem cells. One such example is electromagnetic field (EMF) exposure, which is an alternative approach with promising potential. In this review, we present a critical discourse on the efficiency, practicability, and limitations of some of the relevant methods, with insurmountable evidence backing the implementation of EMF as a feasible strategy for the clinically relevant expansion of MSCs.

Regulating the fate of stem cells for regenerating the intervertebral disc degeneration

Lower back pain is a leading cause of disability and is one of the reasons for the substantial socioeconomic burden. The etiology of intervertebral disc (IVD) degeneration is complicated, and its mechanism is still not completely understood. Factors such as aging, systemic inflammation, biochemical mediators, toxic environmental factors, physical injuries, and genetic factors are involved in the progression of its pathophysiology. Currently, no therapy for restoring degenerated IVD is available except pain management, reduced physical activities, and surgical intervention. Therefore, it is imperative to establish regenerative medicine-based approaches to heal and repair the injured disc, repopulate the cell types to retain water content, synthesize extracellular matrix, and strengthen the disc to restore normal spine flexion. Cellular therapy has gained attention for IVD management as an alternative therapeutic option. In this review, we present an overview of the anatomical and molecular structure and the surrounding pathophysiology of the IVD. Modern therapeutic approaches, including proteins and growth factors, cellular and gene therapy, and cell fate regulators are reviewed. Similarly, small molecules that modulate the fate of stem cells for their differentiation into chondrocytes and notochordal cell types are highlighted.

Coculture of Endothelial and Stromal Cells to Promote Concurrent Osteogenesis and Vasculogenesis

A key challenge in the treatment of large bone defects is the need to provide an adequate and stable vascular supply as new tissue develops. Bone tissue engineering applies selected biomaterials and cell types to create an environment that promotes tissue formation, maturation, and remodeling. Mesenchymal stromal cells (MSCs) have been widely used in these strategies because of their established effects on bone formation, and their ability to act as stabilizing pericytes that support vascular regeneration by endothelial cells (ECs). However, the creation of vascularized bone tissue in vitro requires coupling of osteogenesis and vasculogenesis in a three-dimensional (3D) biomaterial environment. In the present study, 3D fibrin hydrogels containing MSCs and ECs were prevascularized in vitro for 7 days to create an endothelial network in the matrix, and were subsequently cultured for a further 14 days under either continued vasculogenic stimulus, a combination of vasculogenic and osteogenic (hybrid) stimulus, or only osteogenic stimulus. It was found that ECs produced robust vessel networks in 3D fibrin matrices over 7 days of culture, and these networks continued to expand over the 14-day treatment period under vasculogenic conditions. Culture in hybrid medium resulted in maintenance of vessel networks for 14 days, while osteogenic culture abrogated vessel formation. These trends were mirrored in data representing overall cell viability and cell number in the 3D fibrin constructs. MSCs were found to colocalize with EC networks under vasculogenic and hybrid conditions, suggesting pericyte-like function. The bone marker alkaline phosphatase increased over time in hybrid and osteogenic media, but mineral deposition was evident only under purely osteogenic conditions. These results suggest that hybrid media compositions can support some aspects of multiphase tissue formation, but that alternative strategies are needed to obtain robust, concomitant vascularization, and osteogenesis in engineered tissues in vitro. Impact statement The combined use of mesenchymal stromal cells (MSCs) and endothelial cells to concomitantly produce mature bone and a nourishing vasculature is a promising tissue engineering approach to treating large bone defects. However, it is challenging to create and maintain vascular networks in the presence of osteogenic cues. This study used a 3D fibrin matrix to demonstrate that prevascularization of the construct can lead to maintenance of vessel structures over time, but that osteogenesis is compromised under these conditions. This work illuminates the capacity of MSCs to serve as both supportive pericytes and as osteoprogenitor cells, and motivates new strategies for coupling osteogenesis and vasculogenesis in engineered bone tissues.

Depletion of EREG enhances the osteo/dentinogenic differentiation ability of dental pulp stem cells via the p38 MAPK and Erk pathways in an inflammatory microenvironment

BACKGROUND

Epiregulin (EREG) is an important component of EGF and was demonstrated to promote the osteo/dentinogenic differentiation of stem cells from dental apical papilla (SCAPs). Whether EREG can stimulate the osteo/dentinogenic differentiation of dental pulp stem cells (DPSCs) in inflammatory environment is not clear. The purpose of the present study is to investigate the role of EREG on the osteo/dentinogenic differentiation ability of DPSCs in inflammatory environment.

METHODS

DPSCs were isolated from human third molars. Short hairpin RNAs (shRNAs) were used to knock down EREG expression in DPSCs. Recombinant human EREG (rhEREG) protein was used in the rescue experiment. TNF-α was employed to mimic the inflammatory environment in vitro. Alkaline phosphatase (ALP) staining, Alizarin red staining, quantitative calcium analysis, and real-time RT-PCR were performed to detect osteo/dentinogenic differentiation markers and related signalling pathways under normal and inflammatory conditions.

RESULTS

EREG depletion promoted the ALP activity and mineralization ability of DPSCs. The expression of BSP, DMP-1, and DSPP was also enhanced. Moreover, 50 ng/mL rhEREG treatment decreased the osteo/dentinogenic differentiation potential of DPSCs, while treatment with 10 ng/mL TNF-α for 4 h increased the expression of EREG in DPSCs. Conversely, EREG knockdown rescued the impaired osteo/dentinogenic differentiation ability caused by TNF-α treatment. Further mechanistic studies showed that EREG depletion activated the p38 MAPK and Erk signalling pathways in DPSCs under normal and inflammatory conditions.

CONCLUSIONS

Our results demonstrated that EREG could inhibit the osteo/dentinogenic differentiation potential of DPSCs via the p38 MAPK and Erk signalling pathways. Under inflammatory environment, EREG depletion enhanced osteo/dentinogenic differentiation potential of DPSCs by improving the expression of p-p38 MAPK and p-Erk.

Modular cell-assembled adipose matrix-derived bead foams as a mesenchymal stromal cell delivery platform for soft tissue regeneration

With the goal of establishing a new clinically-relevant bioscaffold format to enable the delivery of high densities of human adipose-derived stromal cells (ASCs) for applications in soft tissue regeneration, a novel "cell-assembly" method was developed to generate robust 3-D scaffolds comprised of fused networks of decellularized adipose tissue (DAT)-derived beads. In vitro studies confirmed that the assembly process was mediated by remodelling of the extracellular matrix by the seeded ASCs, which were well distributed throughout the scaffolds and remained highly viable after 8 days in culture. The ASC density, sulphated glycosaminoglycan content and scaffold stability were enhanced under culture conditions that included growth factor preconditioning. In vivo testing was performed to compare ASCs delivered within the cell-assembled DAT bead foams to an equivalent number of ASCs delivered on a previously-established pre-assembled DAT bead foam platform in a subcutaneous implant model in athymic nude mice. Scaffolds were fabricated with human ASCs engineered to stably co-express firefly luciferase and tdTomato to enable long-term cell tracking. Longitudinal bioluminescence imaging showed a significantly stronger signal associated with viable human ASCs at timepoints up to 7 days in the cell-assembled scaffolds, although both implant groups were found to retain similar densities of human ASCs at 28 days. Notably, the infiltration of CD31⁺ murine endothelial cells was enhanced in the cell-assembled implants at 28 days. Moreover, microcomputed tomography angiography revealed that there was a marked reduction in vascular permeability in the cell-assembled group, indicating that the developing vascular network was more stable in the new scaffold format. Overall, the novel cell-assembled DAT bead foams represent a promising platform to harness the pro-regenerative paracrine functionality of human ASCs and warrant further investigation as a clinically-translational approach for volume augmentation.

Priming human adipose-derived mesenchymal stem cells for corneal surface regeneration

Limbal stem cells (LSC) maintain the transparency of the corneal epithelium. Chemical burns lead the loss of LSC inducing an up-regulation of pro-inflammatory and pro-angiogenic factors, triggering corneal neovascularization and blindness. Adipose tissue-derived mesenchymal stem cells (AT-MSC) have shown promise in animal models to treat LSC deficiency (LSCD), but there are not studies showing their efficacy when primed with different media before transplantation. We cultured AT-MSC with standard medium and media used to culture LSC for clinical application. We demonstrated that different media changed the AT-MSC paracrine secretion showing different paracrine effector functions in an in vivo model of chemical burn and in response to a novel in vitro model of corneal inflammation by alkali induction. Treatment of LSCD with AT-MSC changed the angiogenic and inflammatory cytokine profile of mice corneas. AT-MSC cultured with the medium that improved their cytokine secretion, enhanced the anti-angiogenic and anti-inflammatory profile of the treated corneas. Those corneas also presented better outcome in terms of corneal transparency, neovascularization and histologic reconstruction. Priming human AT-MSC with LSC specific medium can potentiate their ability to improve corneal wound healing, decrease neovascularization and inflammation modulating paracrine effector functions in an in vivo optimized rat model of LSCD.

Biophysical and Biochemical Cues of Biomaterials Guide Mesenchymal Stem Cell Behaviors

Mesenchymal stem cells (MSCs) have been widely used in the fields of tissue engineering and regenerative medicine due to their self-renewal capabilities and multipotential differentiation assurance. However, capitalizing on specific factors to precisely guide MSC behaviors is the cornerstone of biomedical applications. Fortunately, several key biophysical and biochemical cues of biomaterials that can synergistically regulate cell behavior have paved the way for the development of cell-instructive biomaterials that serve as delivery vehicles for promoting MSC application prospects. Therefore, the identification of these cues in guiding MSC behavior, including cell migration, proliferation, and differentiation, may be of particular importance for better clinical performance. This review focuses on providing a comprehensive and systematic understanding of biophysical and biochemical cues, as well as the strategic engineering of these signals in current scaffold designs, and we believe that integrating biophysical and biochemical cues in next-generation biomaterials would potentially help functionally regulate MSCs for diverse applications in regenerative medicine and cell therapy in the future.

Evaluation of a peptide motif designed for protein tethering to polymer surfaces

In search for peptide motifs that allow us to efficiently tether fusion proteins onto polymer surfaces, we designed a KLKLKLKLKL (KL5) decapeptide in which basic and hydrophobic amino acids were alternately linked. By means of genetic engineering technology together with a bacterial expression system, the KL5 fusions of epidermal growth factor (EGF), basic fibroblast growth factor, and stromal cell-derived factor-1α were prepared together with their control counterparts without KL5. The adsorption experiments were performed for these fusion proteins on the surface of polystyrene, hydrophilized polystyrene, and polycaprolactone by surface plasmon resonance analysis. To understand the results of the binding assays, the structure of the fusion proteins was predicted by ab initio computer simulation and analyzed empirically by circular dichroism spectroscopy. The result of structural analyses suggested that the KL5 peptide is exposed to the outside and has a negligible effect on the structure of the protein partners. However, it was found that the efficiency of KL5 as a peptide motif greatly depends on protein partners. Our results showed that KL5 exerts most effectively its function as a peptide motif when fused to acidic proteins such as EGF. Indeed, the number of living human mesenchymal stem cells determined after 7-day culture was larger on the polystyrene and polycaprolactone surfaces with EGF tethered through the KL5 peptide than control surfaces. According to the results obtained in this study, we conclude that KL5 is useful as a peptide motif for tethering a specific class of protein partners.

Influence of culture media on the derivation and phenotype of fetal-derived placental mesenchymal stem/stromal cells across gestation

INTRODUCTION

Derivation of pure fetal placental mesenchymal stem/stromal cells (pMSCs) is key to understand their role in placental development. However, isolated pMSCs are often contaminated by maternal-derived decidual MSCs (dMSCs). EGM-2 medium promotes the derivation of term fetal pMSCs, but the extent of first-trimester maternal pMSC contamination remains unclear. Culture media can also affect MSC phenotype. Here, we examined the effects of culture media on maternal pMSC contamination and fetal pMSC phenotype across gestation.

METHODS

pMSCs were derived from first-trimester or term placentae in advanced-DMEM/F12 medium or EGM-2 medium. Proportions of maternal (XX) and fetal (XY) cells in male pMSC cultures were determined by fluorescence in-situ hybridization. pMSC phenotype was analysed by flow cytometry, immunohistochemistry and Alamar blue proliferation assays.

RESULTS

When derived in advanced-DMEM/F12, all first trimester pMSC isolates exhibited maternal contamination (>72% XX cells, n = 5), whilst 7/9 term pMSC isolates were >98% fetal. When derived in EGM-2, all first trimester (n = 4) and term (n = 9) pMSC isolates contained 95-100% fetal cells. Fetal pMSCs in EGM-2 proliferated 2-fold (first-trimester) or 4-fold (term) faster than those in advanced-DMEM/F12 (p < 0.05, n = 3). Fetal pMSCs in both media expressed the generic MSC marker profile (CD90⁺, CD105+, CD73⁺, CD31-, CD34-, CD144-). However, pMSCs transferred from EGM-2 to advanced-DMEM/F12 increased expression of smooth muscle cell markers calponin and α-smooth muscle actin, and decreased expression of the vascular cell marker VEGFR2 (n = 3).

CONCLUSIONS

Deriving first-trimester pMSC in EGM-2 dramatically reduces maternal dMSC contamination. Media affects fetal pMSC phenotype, and careful consideration should be given to application specific culture conditions.

Insight into the proteomic profiling of exosomes secreted by human OM-MSCs reveals a new potential therapy

Mesenchymal stromal cells (MSCs) have been used for the treatment of neuronal injury and neurodegenerative diseases. Their underlying mechanism may involve increased secretion of paracrine factors, which promotes tissue repair. Presently, exosomes have been regarded as important components of paracrine secretion and paracrine factors. MSC exosomes represent a promising opportunity to develop novel cell-free therapy approaches. In this study, exosomes from nasal olfactory mucosa MSCs (OM-MSCs) were extracted and purified using ultracentrifugation, resulting in exosome diameters of 40-130 nm. Similar to other exosomes, OM-MSC exosomes were CD63- and CD81-positive and calnexin-negative. Functionally, OM-MSC exosomes promoted human brain microvascular endothelial cell (HBMEC) proliferation and migration. The present study analyzed the OM-MSC exosome paracrine proteome. A total of 304 exosome-associated proteins were identified by LC-MS/MS, including plasminogen activator inhibitor 1 (SERPINE 1), insulin-like growth factor binding protein family members (IGFBP 4 and 5), epidermal growth factor receptor (EGFR), neurogenic locus notch homolog protein 2 (NOTCH 2), apolipoprotein E (APOE), and heat shock protein HSP90-beta (HSP90AB1). These molecules are known to be important in neurotrophic, angiogenesis, cell growth, differentiation, apoptosis, and inflammation and are highly correlated with the mechanism of tissue repair and neural restoration. These observations may provide a basis for further evaluation of OM-MSC exosome potential as a novel therapeutic modality.

Mesenchymal Stem/Progenitor Cells: The Prospect of Human Clinical Translation

Mesenchymal stem/progenitor cells (MSCs) are key players in regenerative medicine, relying principally on their differentiation/regeneration potential, immunomodulatory properties, paracrine effects, and potent homing ability with minimal if any ethical concerns. Even though multiple preclinical and clinical studies have demonstrated remarkable properties for MSCs, the clinical applicability of MSC-based therapies is still questionable. Several challenges exist that critically hinder a successful clinical translation of MSC-based therapies, including but not limited to heterogeneity of their populations, variability in their quality and quantity, donor-related factors, discrepancies in protocols for isolation, in vitro expansion and premodification, and variability in methods of cell delivery, dosing, and cell homing. Alterations of MSC viability, proliferation, properties, and/or function are also affected by various drugs and chemicals. Moreover, significant safety concerns exist due to possible teratogenic/neoplastic potential and transmission of infectious diseases. Through the current review, we aim to highlight the major challenges facing MSCs' human clinical translation and shed light on the undergoing strategies to overcome them.

Human mesenchymal stromal cells and derived extracellular vesicles: Translational strategies to increase their proangiogenic potential for the treatment of cardiovascular disease

Mesenchymal stromal cells (MSCs) offer great potential for the treatment of cardiovascular diseases (CVDs) such as myocardial infarction and heart failure. Studies have revealed that the efficacy of MSCs is mainly attributed to their capacity to secrete numerous trophic factors that promote angiogenesis, inhibit apoptosis, and modulate the immune response. There is growing evidence that MSC‐derived extracellular vesicles (EVs) containing a cargo of lipids, proteins, metabolites, and RNAs play a key role in this paracrine mechanism. In particular, encapsulated microRNAs have been identified as important positive regulators of angiogenesis in pathological settings of insufficient blood supply to the heart, thus opening a new path for the treatment of CVD. In the present review, we discuss the current knowledge related to the proangiogenic potential of MSCs and MSC‐derived EVs as well as methods to enhance their biological activities for improved cardiac tissue repair. Increasing our understanding of mechanisms supporting angiogenesis will help optimize future approaches to CVD intervention.

Challenges in Clinical Development of Mesenchymal Stromal/Stem Cells: Concise Review

Identified 50 years ago, mesenchymal stromal/stem cells (MSCs) immediately generated a substantial interest among the scientific community because of their differentiation plasticity and hematopoietic supportive function. Early investigations provided evidence of a relatively low engraftment rate and a transient benefit for challenging congenital and acquired diseases. The reasons for these poor therapeutic benefits forced the entire field to reconsider MSC mechanisms of action together with their ex vivo manipulation procedures. This phase resulted in advances in MSCs processing and the hypothesis that MSC‐tissue supportive functions may be prevailing their differentiation plasticity, broadening the spectrum of MSCs therapeutic potential far beyond their lineage‐restricted commitments. Consequently, an increasing number of studies have been conducted for a variety of clinical indications, revealing additional challenges and suggesting that MSCs are still lagging behind for a solid clinical translation. For this reason, our aim was to dissect the current challenges in the development of still promising cell types that, after more than half a century, still need to reach their maturity. stem cells translational medicine2019;8:1135–1148

A serum-free medium formulation efficiently supports isolation and propagation of canine adipose-derived mesenchymal stem/stromal cells

Medium containing Fetal Bovine Serum (FBS) provides a supportive environment for isolation and expansion of mesenchymal stromal/stem cells (MSCs); however, the inherent variability of FBS may contribute to inconsistencies in cell growth and yield between batches of stem cell products. For this reason, we set out to develop a serum-free medium capable of supporting the in vitro expansion of MSCs. First a naïve serum-free medium was formulated by Sato's approach. Once it was established that the naïve serum-free medium supported the expansion of canine adipose-derived MSCs (Ad-MSCs), the serum-free medium was optimized by addition of growth factors. Combinations of growth factors were chosen and compared by their effect on cell proliferation and colony formation. Growth characteristics of canine adipose-derived MSCs cultured in the serum-free medium were comparable to those cultured in standard FBS containing medium. In addition, cell surface marker expression and differentiation potential of serum-free and FBS-based cultures were also comparable. However, a commercial serum-free medium developed for human MSC culture did not support growth of canine Ad-MSCs. In summary, canine Ad-MSCs isolated and cultured in serum-free medium retained the basic characteristics of MSCs cultured in FBS containing medium.

Controlled release of dextrin-conjugated growth factors to support growth and differentiation of neural stem cells

An essential aspect of stem cell in vitro culture and in vivo therapy is achieving sustained levels of growth factors to support stem cell survival and expansion, while maintaining their multipotency and differentiation potential. This study investigated the ability of dextrin (~74,000 g/mol; 27.8 mol% succinoylation) conjugated to epidermal growth factor (EGF) and basic fibroblast growth factor (bFGF; or FGF-2) (3.9 and 6.7% w/w protein loading, respectively) to support the expansion and differentiation of stem cells in vitro via sustained, controllable growth factor release. Supplementation of mouse neural stem cells (mNSCs) with dextrin-growth factor conjugates led to greater and prolonged proliferation compared to unbound EGF/bFGF controls, with no detectable apoptosis after 7 days of treatment. Immunocytochemical detection of neural precursor (nestin) and differentiation (Olig2, MAP2, GFAP) markers verified that controlled release of dextrin-conjugated growth factors preserves stem cell properties of mNSCs for up to 7 days. These results show the potential of dextrin-growth factor conjugates for localized delivery of bioactive therapeutic agents to support stem cell expansion and differentiation, and as an adjunct to direct neuronal repair.

Immunomodulatory effects of rhesus monkey bone marrow-derived mesenchymal stem cells in serum-free conditions

Mesenchymal stem cells (MSCs) have generated tremendous interest for treating various diseases due to their self-renewal and differentiation capacities. Many studies have demonstrated the immunoregulatory capability of MSCs; however, most of these studies were conducted with fetal bovine serum (FBS), which has an uncertain composition. In this study, we established a serum-free, xeno-free, completely chemically defined medium for the proliferation and expansion of rhesus monkey bone marrow (BM)-derived MSCs (rBMSCs) in vitro. The growth kinetics, characteristics, immunophenotype, and immunosuppressive abilities of rBMSCs grown in serum-free media (SFM) were evaluated and compared with those of cells grown in serum-containing media (SCM). Moreover, we employed RNA sequencing to evaluate the expression pattern of genes related to immune responses in both culture conditions. Compared to cells grown in SCM, rBMSCs grown in SFM exhibited better biological characteristics regarding cell proliferation and immunosuppressive abilities. Cells from both media types exhibited similar immunophenotypic expression patterns for CD29, CD34, CD45, HLA-DR, CD73, CD90, and CD105. Gene Ontology (GO) terms, Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment, and Gene Set Enrichment Analysis (GSEA) revealed that CXCL8 was downregulated by 4.1 fold in SFM-cultured rBMSCs compared with those in SCM. Furthermore, the mixed lymphocyte culture revealed that the proliferation activity and the expression levels of inflammatory factors of peripheral blood mononuclear cells (PBMCs) were significantly decreased after the addition of the CXCL8 neutralizing antibody, which was related to the elevated immunosuppressive abilities of SFM-suspended rBMSCs. These results suggest a possible cell culture method as well as immunoregulatory mechanisms for clinical cell therapies requiring nonanimal-derived components.

Epiregulin promotes the migration and chemotaxis ability of adipose-derived mesenchymal stem cells via mitogen-activated protein kinase signaling pathways

To investigate the function of epiregulin (EREG) in the migration and chemotaxis ability of mesenchymal stem cells. Adipose-derived stem cells (ADSCs) were used in this investigation. Lentiviral EREG short hairpin RNA was applied to silence EREG expression in ADSCs. Human recombinant EREG protein (rhEREG) was used to perform a gain-of-function study. Scratch-simulated wound migration and transwell chemotaxis assays were used to examine the migration and chemotaxis capacity of ADSCs in vitro. Using a Western blot assay, the expressions of p38 mitogen-activated protein kinase (p38 MAPK), c-Jun N-terminal kinase (JNK), extracellular signal-regulated protein kinases 1 and 2 (Erk1/2), and protein kinase B were detected. Depletion of EREG caused by specific short hairpin RNA restrained the migration and chemotaxis ability of ADSCs and inhibited the expressions of phosphorylated p38 MAPK, JNK, and Erk1/2. rhEREG improved ADSCs migration and chemotaxis capacity, which was repressed by knockdown of EREG and rescued the expressions of phosphorylated p38 MAPK, JNK, and Erk1/2 impaired by silencing EREG. Furthermore, rhEREG-improved migration and chemotaxis ability in EREG-depleted-ADSCs was restricted by a specific inhibitor, SB203580, for blocking p38 MAPK signaling, PD98059 for blocking Erk1/2 signaling, or SP600125 for blocking JNK signaling in ADSCs separately. EREG promotes migration and chemotaxis ability of ADSCs through MAPK signaling pathways.

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.

Differential effects of amnion and chorion membrane extracts on osteoblast-like cells due to the different growth factor composition of the extracts

Human amniotic membrane extracts contain numerous growth factors and bioactive substances. However, osteogenic effects of amnion and chorion membrane extracts (AME and CME, respectively) on osteoblasts are unclear. In this study, we explored the ability of AME and CME to promote the osteogenic differentiation of osteoblast-like MG-63 cells. MG-63 cells were cultured in osteogenic induction medium (OIM) with or without exogenous AME and CME. CME enhanced the osteogenic differentiation of MG-63 cells compared with AME, as indicated by increased mineralization; alkaline phosphatase activity; and mRNA expression of osteogenic marker genes encoding integrin-binding sialoprotein (IBSP), RUNX2, OSTERIX, and osteocalcin (OCN). Interestingly, AME and CME contained different combinations of osteogenesis-related growth factors, including basic fibroblast growth factor (bFGF), transforming growth factor beta-1 (TGFβ-1), and epidermal growth factor (EGF), which differentially regulated the osteogenic differentiation of MG-63 cells. bFGF and TGFβ-1 present in CME positively regulated the osteogenic differentiation of MG-63 cells, whereas EGF present in AME negatively regulated the differentiation of MG-63 cells. Moreover, exogenous treatment of EGF antagonized CME-induced mineralization of extracellular matrix on MG-63 cells. We compared the osteogenic efficacy of CME with that of BMP2, bFGF, and TGFβ-1 alone or their combinations. We observed that CME greatly enhanced osteogenesis by providing a conductive environment for the differentiation of MG-63 cells. Together, our results indicated that human AME and CME exerted differential effects on osteogenesis because of the presence of different compositions of growth factors. In addition, our results highlighted a new possible strategy of using CME as a biocompatible therapeutic material for bone regeneration.

TGF-β1 Pretreatment Improves the Function of Mesenchymal Stem Cells in the Wound Bed

The wound healing process initiates after injury to a tissue and involves a series of orchestrated events to minimize the invasion of foreign matters such as bacteria and efficiently regenerate the damaged tissue. A variety of cells must be recruited to the tissue during wound healing. However, this process is severely disrupted in patients suffering from chronic illness, including diabetes, leading to impaired healing or non-healing wounds. Current avenues of treatment include negative-pressure therapy, wound debridement, growth factor replacement, and cell-based therapies. Among these therapies, mesenchymal stem cells (MSCs) delivery to the wound holds a very high promise due to the innate abilities of MSCs that include immunogenicity, plasticity, and self-renewal. Bone marrow derived MSCs have been shown to promote more rapid wound healing by increased cytokine production in diabetic mice. However, the lack of understanding of the mechanical and chemical interaction of the transplanted MSCs with the factors present in the regenerative niches limits their efficacy in the wound bed. In this study, we sought to understand how the changes in MSC biochemical and biophysical properties can affect their function in vitro and in vivo. We demonstrate that pretreatment of MSCs with the mechano-stimulatory soluble factor transforming growth factor (TGF-β1), which is highly expressed in injury sites, improves wound closure in a syngeneic murine wound model. This improved wound closure correlated with increased invasion into the wound bed. In vitro studies demonstrated that TGF-β1 pretreatment expedited wound closure by increasing adhesion, traction force, and migration even after removal of the stimulus. Furthermore, this response was mediated by the cytoskeletal protein focal adhesion kinase. Taken together, this study suggests that defined chemical stimuli can benefit site specific adaptability of MSCs to improve their function and therapeutic usefulness.

Avoidance of Maternal Cell Contamination and Overgrowth in Isolating Fetal Chorionic Villi Mesenchymal Stem Cells from Human Term Placenta

Human placenta is rich in mesenchymal stem/stromal cells (MSC), with their origin widely presumed fetal. Cultured placental MSCs are confounded by a high frequency of maternal cell contamination. Our recent systematic review concluded that only a small minority of placental MSC publications report fetal/maternal origin, and failed to discern a specific methodology for isolation of fetal MSC from term villi. We determined isolation conditions to yield fetal and separately maternal MSC during ex vivo expansion from human term placenta. MSCs were isolated via a range of methods in combination; selection from various chorionic regions, different commercial media, mononuclear cell digest and/or explant culture. Fetal and maternal cell identities were quantitated in gender‐discordant pregnancies by XY chromosome fluorescence in situ hybridization. We first demonstrated reproducible maternal cell contamination in MSC cultures from all chorionic anatomical locations tested. Cultures in standard media rapidly became composed entirely of maternal cells despite isolation from fetal villi. To isolate pure fetal cells, we validated a novel isolation procedure comprising focal dissection from the cotyledonary core, collagenase/dispase digestion and explant culture in endothelial growth media that selected, and provided a proliferative environment, for fetal MSC. Comparison of MSC populations within the same placenta confirmed fetal to be smaller, more osteogenic and proliferative than maternal MSC. We conclude that in standard media, fetal chorionic villi‐derived MSC (CV‐MSC) do not grow readily, whereas maternal MSC proliferate to result in maternal overgrowth during culture. Instead, fetal CV‐MSCs require isolation under specific conditions, which has implications for clinical trials using placental MSC. Stem Cells Translational Medicine2017;6:1070–1084

Retention of Human-Induced Pluripotent Stem Cells (hiPS) With Injectable HA Hydrogels for Vocal Fold Engineering

Objective:

One prospective treatment option for vocal fold scarring is regeneration with an engineered scaffold containing induced pluripotent stem cells (iPS). In the present study, we investigated the feasibility of utilizing an injectable hyaluronic acid (HA) scaffold encapsulated with human-iPS cell (hiPS) for regeneration of vocal folds.

Methods:

Thirty athymic nude rats underwent unilateral vocal fold injury. Contralateral vocal folds served as uninjured controls. Hyaluronic acid hydrogel scaffold, HA hydrogel scaffold containing hiPS, and HA hydrogel scaffold containing hiPS with epidermal growth factor (EGF) were injected in both vocal folds immediately after surgery. One and 2 weeks after injection, larynges were excised for histology, immunohistochemistry, and fluorescence in situ hybridization (FISH).

Results:

Presence of HA hydrogel was confirmed in vocal folds 1 and 2 weeks post injection. The FISH analysis confirmed the presence and viability of hiPS in the injected vocal folds. Histological results demonstrated that vocal folds injected with HA hydrogel scaffold containing EGF demonstrated less fibrosis than those with HA hydrogel only.

Conclusions:

Human-iPS survived in injured rat vocal folds. The HA hydrogel with hiPS and EGF ameliorated the fibrotic response. Additional work is necessary to optimize hiPS differentiation and further confirm the safety of hiPS for clinical applications.

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.

Self-Renewal of Bone Marrow Stem Cells by Nanovesicles Engineered from Embryonic Stem Cells

Extracellular vesicles can enhance cell proliferation by stimulating signal transduction and delivering genetic materials, and thus may have applications in regenerative medicine and other therapeutic applications. The processes employed to isolate extracellular vesicles, however, are complex and achieve low yield. To overcome these obstacles, a large-scale, micropore device for generating extracellular vesicle-mimetic nanovesicles that have characteristics similar to those of extracellular vesicles is fabricated. The nanovesicles are generated through the self-assembly capability of cell membrane fragments in an aqueous solution. The nanovesicles enhance the proliferation of murine mesenchymal stem cells (MSCs), stimulate the signal pathway related to cell proliferation, and do not influence the characteristics of murine MSCs. Therefore, these nanovesicles could provide stable MSCs for regenerative medicine and other therapeutic applications.

MicroRNA-98 regulates osteogenic differentiation of human bone mesenchymal stromal cells by targeting BMP2

To study the effects of microRNA‐98 (miR‐98) on human bone mesenchymal stromal cells (hBMSCs). The patients undergoing hip arthroplasty were selected by inclusion/exclusion criteria for this study. The extracted hBMSCs were detected of osteogenic differentiation by alizarin red S staining, and of cell phenotype by flow cytometry. Bioinformatics, dual luciferase report, western blotting, RT‐PCR and immunoblotting were used in our study. The hBMSCs were divided into miR‐98 mimics, miR‐98 negative control (NC), miR‐98 inhibitors, Mock and miR‐98 inhibitors + siBMP2 groups. Human bone mesenchymal stromal cells were extracted and purified in vitro and had specific cytological morphology, surface markers and abilities of self‐renewal and differentiation. Compared with the NC group and Mock group, the miR‐98 mimics group showed increased miR‐98 level while the miR‐98 inhibitors group decreased miR‐98 level (both P < 0.01). Dual luciferase reporter showed BMP2 was the target gene of miR‐98. The levels of mRNA and protein expression of BMP2, protein expression of RUNX2, alkaline phosphatase activity and osteocalcin content significantly decreased in the miR‐98 mimics group while increased in the miR‐98 inhibitors group and showed no changes in the NC group and Mock group (all P < 0.05). The miR‐98 mimics group showed obviously declined stained red particles and the miR‐98 inhibitors group showed opposite result. After lowering the expression of miR‐98, osteogenic differentiation ability of hBMSCs rose, which was weakened by the transfection with siBMP2. miR‐98 may regulate osteogenic differentiation of hBMSCs by targeting BMP2.

The effects of culture conditions on the functionality of efficiently obtained mesenchymal stromal cells from human cord blood

BACKGROUND AIMS

Cord blood (CB) is an attractive source of mesenchymal stromal cells (MSCs) because of its abundant availability and ease of collection. However, the success rate of generating CB-MSCs is low. In this study, our aim was to demonstrate the efficiency of our previously described method to obtain MSCs from CB and further characterize them and to study the effects of different culture conditions on MSCs.

METHODS

CB-MSC cultures were established in low oxygen (3%) conditions on fibronectin in 10% fetal bovine serum containing culture medium supplemented with combinations of growth factors. Cells were characterized for their adipogenic, osteogenic and chondrogenic differentiation capacity; phenotype; and HOX gene expression profile. The functionality of the cells cultured in different media was tested in vitro with angiogenesis and T-cell proliferation assays.

RESULTS

We demonstrate 87% efficacy in generating MSCs from CB. The established cells had typical MSC characteristics with reduced adipogenic differentiation potential and a unique HOX gene fingerprint. Growth factor-rich medium and a 3% oxygen condition enhanced cell proliferation; however, the growth factor-rich medium had a negative effect on the expression of CD90. Dexamethasone-containing medium improved the capacity of the cells to suppress T-cell proliferation, whereas the cells grown without dexamethasone were more able to support angiogenesis.

CONCLUSIONS

Our results demonstrate that the composition of expansion medium is critical for the functionality of MSCs and should always be appropriately defined for each purpose.

Scalable microcarrier-based manufacturing of mesenchymal stem/stromal cells

Due to their unique features, mesenchymal stem/stromal cells (MSC) have been exploited in clinical settings as therapeutic candidates for the treatment of a variety of diseases. However, the success in obtaining clinically-relevant MSC numbers for cell-based therapies is dependent on efficient isolation and ex vivo expansion protocols, able to comply with good manufacturing practices (GMP). In this context, the 2-dimensional static culture systems typically used for the expansion of these cells present several limitations that may lead to reduced cell numbers and compromise cell functions. Furthermore, many studies in the literature report the expansion of MSC using fetal bovine serum (FBS)-supplemented medium, which has been critically rated by regulatory agencies. Alternative platforms for the scalable manufacturing of MSC have been developed, namely using microcarriers in bioreactors, with also a considerable number of studies now reporting the production of MSC using xenogeneic/serum-free medium formulations. In this review we provide a comprehensive overview on the scalable manufacturing of human mesenchymal stem/stromal cells, depicting the various steps involved in the process from cell isolation to ex vivo expansion, using different cell tissue sources and culture medium formulations and exploiting bioprocess engineering tools namely microcarrier technology and bioreactors.

Mesenchymal Stem/Stromal Cells in Regenerative Medicine: Can Preconditioning Strategies Improve Therapeutic Efficacy?

Mesenchymal stem/stromal cells (MSCs) are becoming increasingly important for the development of cell therapeutics in regenerative medicine. Featuring immunomodulatory potential as well as secreting a variety of trophic factors, MSCs showed remarkable therapeutic effects in numerous preclinical disease models. However, sustainable translation of MSC therapies to the clinic is hampered by heterogeneity of MSCs and non-standardized in vitro culture technologies. Moreover, potent MSC therapeutics require MSCs with maximum regenerative capacity. There is growing evidence that in vitro preconditioning strategies of MSCs can optimize their therapeutic potential. In the following we will discuss achievements and challenges of the development of MSC therapies in regenerative medicine highlighting specific in vitro preconditioning strategies prior to cell transplantation to increase their therapeutic efficacy.

Epidermal Growth Factor Tethered to β-Tricalcium Phosphate Bone Scaffolds via a High-Affinity Binding Peptide Enhances Survival of Human Mesenchymal Stem Cells/Multipotent Stromal Cells in an Immune-Competent Parafascial Implantation Assay in Mice

: Mesenchymal stem cells/multipotent stromal cells (MSCs) are attractive candidates for cell therapies owing to their ability to differentiate into many lineages. However, these cells often fail to survive when implanted into a harsh wound environment, limiting efficacy in vivo. To improve MSC survival, we previously found that tethered epidermal growth factor (tEGF) molecules that restrict epidermal growth factor receptor (EGFR) signaling to the cell surface provide resistance to death signals. To adapt this system to wound healing, we tethered epidermal growth factor (EGF) to tricalcium phosphate (TCP) particle scaffolds, clinically used in bone healing. Human primary MSCs seeded on TCP and mixed into a collagen-based gel were injected in the perifascial space of immunocompetent mice with or without tEGF attached to the surface. We found that tethering EGF to the TCP scaffolds yielded approximately a fourfold increase in MSC survival compared with non-EGF scaffolds at 21 days, as well as significant improvements in survival in the short term at 2 and 7 days after implantation. Overall, our approach to sustaining EGFR signaling reduced MSC death in vivo and may be useful for future cell therapies where MSCs typically die on implantation.

SIGNIFICANCE

Stem cells are limited as tissue replacements owing to rapid death induced in the hostile wound environment. It has been found that restricting epidermal growth factor (EGF) receptor signaling to the membrane provides a survival advantage. This report elucidates a method to tether EGF to bone induction material to improve the survival of mesenchymal stem cells/multipotent stromal cells in vivo.