Human mesenchymal stem cells from the umbilical cord matrix: successful isolation and ex vivo expansion using serum-/xeno-free culture media

Translating mesenchymal stem cell and their exosome research into GMP compliant advanced therapy products: Promises, problems and prospects

Mesenchymal stem cells (MSCs) are one of the few stem cell types used in clinical practice as therapeutic agents for immunomodulation and ischemic tissue repair, due to their unique paracrine capacity, multiple differentiation potential, active components in exosomes, and effective mitochondria donation. At present, MSCs derived from tissues such as bone marrow and umbilical cord are widely applied in preclinical and clinical studies. Nevertheless, there remain challenges to the maintenance of consistently good quality MSCs derived from different donors or tissues, directly impacting their application as advanced therapy products. In this review, we discuss the promises, problems, and prospects associated with translation of MSC research into a pharmaceutical product. We review the hurdles encountered in translation of MSCs and MSC-exosomes from the research bench to an advanced therapy product compliant with good manufacturing practice (GMP). These difficulties include how to set up GMP-compliant protocols, what factors affect raw material selection, cell expansion to product formulation, establishment of quality control (QC) parameters, and quality assurance to comply with GMP standards. To avoid human error and reduce the risk of contamination, an automatic, closed system that allows real-time monitoring of QC should be considered. We also highlight potential advantages of pluripotent stem cells as an alternative source for MSC and exosomes generation and manufacture.

Serum- and xeno-free culture of human umbilical cord perivascular cells for pediatric heart valve tissue engineering

BACKGROUND

Constructs currently used to repair or replace congenitally diseased pediatric heart valves lack a viable cell population capable of functional adaptation in situ, necessitating repeated surgical intervention. Heart valve tissue engineering (HVTE) can address these limitations by producing functional living tissue in vitro that holds the potential for somatic growth and remodelling upon implantation. However, clinical translation of HVTE strategies requires an appropriate source of autologous cells that can be non-invasively harvested from mesenchymal stem cell (MSC)-rich tissues and cultured under serum- and xeno-free conditions. To this end, we evaluated human umbilical cord perivascular cells (hUCPVCs) as a promising cell source for in vitro production of engineered heart valve tissue.

METHODS

The proliferative, clonogenic, multilineage differentiation, and extracellular matrix (ECM) synthesis capacities of hUCPVCs were evaluated in a commercial serum- and xeno-free culture medium (StemMACS™) on tissue culture polystyrene and benchmarked to adult bone marrow-derived MSCs (BMMSCs). Additionally, the ECM synthesis potential of hUCPVCs was evaluated when cultured on polycarbonate polyurethane anisotropic electrospun scaffolds, a representative biomaterial for in vitro HVTE.

RESULTS

hUCPVCs had greater proliferative and clonogenic potential than BMMSCs in StemMACS™ (p < 0.05), without differentiation to osteogenic and adipogenic phenotypes associated with valve pathology. Furthermore, hUCPVCs cultured with StemMACS™ on tissue culture plastic for 14 days synthesized significantly more total collagen, elastin, and sulphated glycosaminoglycans (p < 0.05), the ECM constituents of the native valve, than BMMSCs. Finally, hUCPVCs retained their ECM synthesizing capacity after 14 and 21 days in culture on anisotropic electrospun scaffolds.

CONCLUSION

Overall, our findings establish an in vitro culture platform that uses hUCPVCs as a readily-available and non-invasively sourced autologous cell population and a commercial serum- and xeno-free culture medium to increase the translational potential of future pediatric HVTE strategies. This study evaluated the proliferative, differentiation and extracellular matrix (ECM) synthesis capacities of human umbilical cord perivascular cells (hUCPVCs) when cultured in serum- and xeno-free media (SFM) against conventionally used bone marrow-derived MSCs (BMMSCs) and serum-containing media (SCM). Our findings support the use of hUCPVCs and SFM for in vitro heart valve tissue engineering (HVTE) of autologous pediatric valve tissue. Figure created with BioRender.com.

A Three-Dimensional Printed Polycaprolactone–Biphasic-Calcium-Phosphate Scaffold Combined with Adipose-Derived Stem Cells Cultured in Xenogeneic Serum-Free Media for the Treatment of Bone Defects

The efficacy of a three-dimensional printed polycaprolactone–biphasic-calcium-phosphate scaffold (PCL–BCP TDP scaffold) seeded with adipose-derived stem cells (ADSCs), which were cultured in xenogeneic serum-free media (XSFM) to enhance bone formation, was assessed in vitro and in animal models. The ADSCs were isolated from the buccal fat tissue of six patients using enzymatic digestion and the plastic adherence method. The proliferation and osteogenic differentiation of the cells cultured in XSFM when seeded on the scaffolds were assessed and compared with those of cells cultured in a medium containing fetal bovine serum (FBS). The cell–scaffold constructs were cultured in XSFM and were implanted into calvarial defects in thirty-six Wistar rats to assess new bone regeneration. The proliferation and osteogenic differentiation of the cells in the XSFM medium were notably better than that of the cells in the FBS medium. However, the efficacy of the constructs in enhancing new bone formation in the calvarial defects of rats was not statistically different to that achieved using the scaffolds alone. In conclusion, the PCL–BCP TDP scaffolds were biocompatible and suitable for use as an osteoconductive framework. The XSFM medium could support the proliferation and differentiation of ADSCs in vitro. However, the cell–scaffold constructs had no benefit in the enhancement of new bone formation in animal models.

A Robust and Highly Efficient Approach for Isolation of Mesenchymal Stem Cells From Wharton's Jelly for Tissue Repair

Mesenchymal stem cells derived from umbilical cord Wharton's Jelly (WJ-MSCs) are emerging as promising therapeutics for a variety of diseases due to their ability of regeneration and immunomodulation, and their non-tumorigenic and non-immunogenic properties. Although multiple protocols have been developed for WJ-MSC isolation, insufficient cell numbers, heterogeneous cell population, and variations in procedures between different laboratories impede further clinical applications. Here, we compared six widely used WJ-MSC isolation methods regarding cell morphology, yield, purity, proliferation rate, and differentiation potential. Based on these analyses, we identified that the inefficiency of the extracellular matrix digestion results in low cell yield. Thus, we developed a new method called "Mince-Soak-Digest (MSD)" to isolate MSCs from WJ by incorporating a soaking step to facilitate the digestion of the extracellular matrix and release of the cells. Our newly developed method generates significantly higher cell yield (4- to 10-fold higher) than six widely used methods that we tested with high purity and consistency. Importantly, by transplantation of WJ-MSCs to the rat uterus, we repair the endometrial injury and restore the fertility of the rats. In conclusion, our results provide a robust and highly efficient approach for the isolation of WJ-MSCs to restore injured tissue. The higher efficiency of MSD assures the abundance of WJ-MSCs for clinical applications. Furthermore, the reliability of MSD contributes to the standardization of WJ-MSC isolation, which eliminates the discrepancies due to isolation procedures, thus facilitating the evaluation of the efficacy of WJ-MSCs across various human clinical applications.

Culturing and Scaling up Stem Cells of Dental Pulp Origin Using Microcarriers

Ectomesenchymal stem cells derived from the dental pulp are of neural crest origin, and as such are promising sources for cell therapy and tissue engineering. For safe upscaling of these cells, microcarrier-based culturing under dynamic conditions is a promising technology. We tested the suitability of two microcarriers, non-porous Cytodex 1 and porous Cytopore 2, for culturing well characterized dental pulp stem cells (DPSCs) using a shake flask system. Human DPSCs were cultured on these microcarriers in 96-well plates, and further expanded in shake flasks for upscaling experiments. Cell viability was measured using the alamarBlue assay, while cell morphology was observed by conventional and two-photon microscopies. Glucose consumption of cells was detected by the glucose oxidase/Clark-electrode method. DPSCs adhered to and grew well on both microcarrier surfaces and were also found in the pores of the Cytopore 2. Cells grown in tissue culture plates (static, non-shaking conditions) yielded 7 × 105 cells/well. In shake flasks, static preincubation promoted cell adhesion to the microcarriers. Under dynamic culture conditions (shaking) 3 × 107 cells were obtained in shake flasks. The DPSCs exhausted their glucose supply from the medium by day seven even with partial batch-feeding. In conclusion, both non-porous and porous microcarriers are suitable for upscaling ectomesenchymal DPSCs under dynamic culture conditions.

Differential Development of Umbilical Cord-Derived Mesenchymal Stem Cells During Long-Term Maintenance in Fetal Bovine Serum-Supplemented Medium and Xeno- and Serum-Free Culture Medium

Umbilical cord-derived mesenchymal stem/stromal cells (UC-MSCs) are believed to have potential for the treatment of various diseases; thus, many scientists have investigated the molecular mechanisms underlying the function of UC-MSCs and, for example, the appropriate media for large-scale UC-MSC expansion to prepare cells for real-world application. In this study, we investigated the cellular morphology, proliferation capacity, surface markers, cellular senescence signals, clonogenic potential, trilineage differentiation capacity, and secreted factors of human primary UC-MSCs in long-term culture from passage 2 (P2) to passage 10 (P10) with either conventional fetal bovine serum (FBS)-supplemented medium or commercial xeno- and serum-free medium (StemMACS™). We found that the cells cultured in both media had similar morphology and marker expression. However, the proliferation kinetics as measured by the cell population doubling time differed in a passage (P2-P10)-dependent manner between the cells cultured in the two media; sustainable growth was observed in cells maintained in xeno- and serum-free medium. Moreover, significant differences in cellular senescence signals were observed, with more aging cells in the cell population cultured in FBS-containing medium. Colony numbers and the day that the first colony appeared were similar; however, UC-MSC colony sizes were smaller when cultured in FBS-containing medium. In addition, the multidifferentiation potential of UC-MSCs cultured in xeno- and serum-free StemMACS medium was maintained during long-term culture, but this potential was lost for adipogenic differentiation at P9. Moreover, secreted epidermal growth factor and vascular endothelial growth factor (VEGF)-A were detected in the conditioned media from UC-MSCs, whereas platelet-derived growth factor was not. Similar expression of these factors was observed in conditioned media of UC-MSCs cultured in StemMACS, but the VEGF level was higher in young UC-MSCs (P6) than in aged UC-MSCs cultured in FBS-supplemented Dulbecco's modified Eagle's medium/F12. Thus, StemMACS is better for UC-MSC expansion than conventional FBS-supplemented culture medium, especially when culturing UC-MSCs for real-world applications.

Influence of the mesenchymal stromal cell source on the hematopoietic supportive capacity of umbilical cord blood-derived CD34+-enriched cells

Background

Umbilical cord blood (UCB) is a clinically relevant alternative source of hematopoietic stem/progenitor cells (HSPC). To overcome the low cell number per UCB unit, ex vivo expansion of UCB HSPC in co-culture with mesenchymal stromal cells (MSC) has been established. Bone marrow (BM)-derived MSC have been the standard choice, but the use of MSC from alternative sources, less invasive and discardable, could ease clinical translation of an expanded CD34⁺ cell product. Here, we compare the capacity of BM-, umbilical cord matrix (UCM)-, and adipose tissue (AT)-derived MSC, expanded with/without xenogeneic components, to expand/maintain UCB CD34⁺-enriched cells ex vivo.

Methods

UCB CD34⁺-enriched cells were isolated from cryopreserved mononuclear cells and cultured for 7 days over an established feeder layer (FL) of BM-, UCM-, or AT-derived MSC, previously expanded using fetal bovine serum (FBS) or fibrinogen-depleted human platelet lysate (HPL) supplemented medium. UCB cells were cultured in serum-free medium supplemented with SCF/TPO/FLT3-L/bFGF. Fold increase in total nucleated cells (TNC) as well as immunophenotype and clonogenic potential (cobblestone area-forming cells and colony-forming unit assays) of the expanded hematopoietic cells were assessed.

Results

MSC from all sources effectively supported UCB HSPC expansion/maintenance ex vivo, with expansion factors (in TNC) superior to 50x, 70x, and 80x in UCM-, BM-, and AT-derived MSC co-cultures, respectively. Specifically, AT-derived MSC co-culture resulted in expanded cells with similar phenotypic profile compared to BM-derived MSC, but resulting in higher total cell numbers. Importantly, a subpopulation of more primitive cells (CD34⁺CD90⁺) was maintained in all co-cultures. In addition, the presence of a MSC FL was essential to maintain and expand a subpopulation of progenitor T cells (CD34⁺CD7⁺). The use of HPL to expand MSC prior to co-culture establishment did not influence the expansion potential of UCB cells.

Conclusions

AT represents a promising alternative to BM as a source of MSC for co-culture protocols to expand/maintain HSPC ex vivo. On the other hand, UCM-derived MSC demonstrated inferior hematopoietic supportive capacity compared to MSC from adult tissues. Despite HPL being considered an alternative to FBS for clinical-scale manufacturing of MSC, further studies are needed to determine its impact on the hematopoietic supportive capacity of these cells.

Three-Dimensional Culture of Ameloblast-Originated HAT-7 Cells for Functional Modeling of Defective Tooth Enamel Formation

Background: Amelogenesis, the formation of dental enamel, is well understood at the histomorphological level but the underlying molecular mechanisms are poorly characterized. Ameloblasts secrete enamel matrix proteins and Ca²⁺, and also regulate extracellular pH as the formation of hydroxyapatite crystals generates large quantities of protons. Genetic or environmental impairment of transport and regulatory processes (e.g. dental fluorosis) leads to the development of enamel defects such as hypomineralization.

Aims: Our aims were to optimize the culture conditions for the three-dimensional growth of ameloblast-derived HAT-7 cells and to test the effects of fluoride exposure on HAT-7 spheroid formation.

Methods: To generate 3D HAT-7 structures, cells were dispersed and plated within a Matrigel extracellular matrix scaffold and incubated in three different culture media. Spheroid formation was then monitored over a two-week period. Ion transporter and tight-junction protein expression was investigated by RT-qPCR. Intracellular Ca²⁺ and pH changes were measured by microfluorometry using the fluorescent dyes fura-2 and BCECF.

Results: A combination of Hepato-STIM epithelial cell differentiation medium and Matrigel induced the expansion and formation of 3D HAT-7 spheroids. The cells retained their epithelial cell morphology and continued to express both ameloblast-specific and ion transport-specific marker genes. Furthermore, like two-dimensional HAT-7 monolayers, the HAT-7 spheroids were able to regulate their intracellular pH and to show intracellular calcium responses to extracellular stimulation. Finally, we demonstrated that HAT-7 spheroids may serve as a disease model for studying the effects of fluoride exposure during amelogenesis.

Conclusion: In conclusion, HAT-7 cells cultivated within a Matrigel extracellular matrix form three-dimensional, multi-cellular, spheroidal structures that retain their functional capacity for pH regulation and intracellular Ca²⁺ signaling. This new 3D model will allow us to gain a better understanding of the molecular mechanisms involved in amelogenesis, not only in health but also in disorders of enamel formation, such as those resulting from fluoride exposure.

Minicircle-based expression of vascular endothelial growth factor in mesenchymal stromal cells from diverse human tissues

BACKGROUND

Mesenchymal stromal cells (MSC) have been exploited for the treatment of ischemic diseases given their angiogenic potential. Despite bone marrow (BM) being the most studied tissue source, cells with similar intrinsic properties can be isolated from adipose tissue (AT) and umbilical cord matrix (UCM). The present study aims to compare the angiogenic potential of MSC obtained from BM, AT and UCM that were genetically modified with vascular endothelial growth factor (VEGF)-encoding minicircle (MC) vectors. The overexpression of VEGF combined with the intrinsic properties of MSC could represent a promising strategy towards angiogenic therapies.

METHODS

We established a microporation-based protocol to transfect human MSC using VEGF-encoding MC (MC-VEGF). VEGF production levels were measured by an enzyme-linked immunosorbent assay and a quantitative polymerase chain reaction. The in vitro angiogenic potential of transfected cells was quantified using cell tube formation and migration functional studies.

RESULTS

MSC isolated from BM, AT or UCM showed similar levels of VEGF secretion after transfection with MC-VEGF. Those values were significantly higher when compared to non-transfected cells, indicating an effective enhancement of VEGF production. Transfected cells displayed higher in vitro angiogenic potential than non-transfected controls, as demonstrated by functional in vitro assays. No significant differences were observed among cells from different sources.

CONCLUSIONS

Minicircles can be successfully used to transiently overexpress VEGF in human MSC, regardless of the cell tissue source, representing an important advantage in a clinical context (i.e., angiogenic therapy) because a standard protocol might be applied to MSC of different tissue sources, which can be differentially selected according to the application (e.g., autologous versus allogeneic settings).

Nasal Turbinate Mesenchymal Stromal Cells Preserve Characteristics of Their Neural Crest Origin and Exert Distinct Paracrine Activity

The sources of mesenchymal stromal cells (MSCs) for cell therapy trials are expanding, increasing the need for their characterization. Here, we characterized multi-donor, turbinate-derived MSCs (TB-MSCs) that develop from the neural crest, and compared them to bone marrow-derived MSCs (BM-MSCs). TB-MSCs had higher proliferation potential and higher self-renewal of colony forming cells, but lower potential for multi-lineage differentiation than BM-MSCs. TB-MSCs expressed higher levels of neural crest markers and lower levels of pericyte-specific markers. These neural crest-like properties of TB-MSCs were reflected by their propensity to differentiate into neuronal cells and proliferative response to nerve growth factors. Proteomics (LC-MS/MS) analysis revealed a distinct secretome profile of TB-MSCs compared to BM and adipose tissue-derived MSCs, exhibiting enrichments of factors for cell-extracellular matrix interaction and neurogenic signaling. However, TB-MSCs and BM-MSCs exhibited comparable suppressive effects on the allo-immune response and comparable stimulatory effects on hematopoietic stem cell self-renewal. In contrast, TB-MSCs stimulated growth and metastasis of breast cancer cells more than BM-MSCs. Altogether, our multi-donor characterization of TB-MSCs reveals distinct cell autonomous and paracrine properties, reflecting their unique developmental origin. These findings support using TB-MSCs as an alternative source of MSCs with distinct biological characteristics for optimal applications in cell therapy.

Isolation and Characterization of Feline Wharton's Jelly-Derived Mesenchymal Stem Cells

Wharton’s jelly is a well-known mesenchymal stem cell source in many species, including humans. However, there have been no reports confirming the presence of mesenchymal stem cells in Wharton’s jelly in cats. The purpose of this study was to isolate mesenchymal stem cells (MSCs) from the Wharton’s jelly of cats and to characterize stem cells. In this study, feline Wharton’s jelly-derived mesenchymal stem cells (fWJ-MSCs) were isolated and successfully cultured. fWJ-MSCs were maintained and the proliferative potential was measured by cumulative population doubling level (CPDL) test, scratch test, and colony forming unit (CFU) test. Stem cell marker, karyotyping and immunophenotyping analysis by flow cytometry showed that fWJ-MSCs possessed characteristic mesenchymal stem cell markers. To confirm the differentiation potential, we performed osteogenic, adipogenic and chondrogenic induction under each differentiation condition. fWJ-MSCs has the ability to differentiate into multiple lineages, including osteogenic, adipogenic and chondrogenic differentiation. This study shows that Wharton’s jelly of cat can be a good source of mesenchymal stem cells. In addition, fWJ-MSCs may be useful for stem cell-based therapeutic applications in feline medicine.

Influences of Xeno-Free Media on Mesenchymal Stem Cell Expansion for Clinical Application

Mesenchymal stem/stromal cells (MSCs) are multipotent somatic stem/progenitor cells that can be isolated from various tissues and have attracted increasing attention from the scientific community. This is due to MSCs showing great potential for incurable disease treatment, and most applications of MSCs involve tissue degeneration and treatment of immune- and inflammation-mediated diseases. Conventional MSC cultures contain fetal bovine serum (FBS), which is a common supplement for cell development but is also a risk factor for exposure to animal-derived pathogens. To avoid the risks resulting from the xenogeneic origin and animal-derived pathogens of FBS, xeno-free media have been developed and commercialized to satisfy MSC expansion demands for human clinical applications. This review summarized and provided an overview of xeno-free media that are currently used for MSC expansion. Additionally, we discussed the influences of different xeno-free media on MSC biology with particular regard to cell morphology, surface marker expression, proliferation, differentiation and immunomodulation. The xeno-free media can be serum-free and xeno-free media or media supplemented with some human-originating substances, such as human serum, human platelet lysates, human umbilical cord serum/plasma, or human plasma-derived supplements for cell culture medium. These media have capacity to maintain a spindle-shaped morphology, the expression of typical surface markers, and the capacity of multipotent differentiation and immunomodulation of MSCs. Xeno-free media showed potential for safe use for human clinical treatment. However, the influences of these xeno-free media on MSCs are various and any xeno-free medium should be examined prior to being used for MSC cultures.

Serum-Free Medium Enhances the Therapeutic Effects of Umbilical Cord Mesenchymal Stromal Cells on a Murine Model for Acute Colitis

The usage of animal serum may ultimately prevent the application of ex vivo cultured mesenchymal stromal cells (MSCs) in a clinical setting due to safety concerns and batch-to-batch variability. Increasing regulatory pressure to limit use of animal serum has been issued and serum-free, xeno-free, and chemically defined media (S&XFM-CD) is encouraged to replace serum-containing media (SCM) in the stem cell preparation process. We previously developed a S&XFM-CD for the expansion of umbilical cord-derived MSCs (UCMSCs). Different culture conditions affect the function of MSCs, which may further affect the therapeutic efficiency and mechanisms of action. In this study, we compared the therapeutic effect and mechanism of UCMSCs in S&XFM-CD (UCMSC^S&XFM−CD) in experimental colitis with those in SCM (UCMSC^SCM). UCMSC^S&XFM−CD exhibited better therapeutic effects than UCMSC^SCM by body weight, disease activity index, and histological colitis score. UCMSC^S&XFM−CD or UCMSC^SCM migrated to the inflammation site of injured colon, but exhibited low levels of recruitment and persistence. Systemic depletion of endogenous macrophages impaired the therapeutic effects of UCMSC^SCM and UCMSC^S&XFM−CD. Furthermore, UCMSC^S&XFM−CD more markedly promoted intestinal macrophage polarisation from M1 to M2 phenotype to produce higher levels of IL-10 and lower levels of TNF-α in colon tissue than UCMSC^SCM, while a higher level of IL-4 was produced in UCMSC^SCM-treated group. UCMSC^S&XFM−CD cocultured with RAW264.7 cells in a transwell system promoted the release of TSG-6 and IL-6, whereas UCMSC^SCM increased PGE₂ levels. Taken together, we demonstrated that UCMSCs in S&XFM-CD exhibited improved therapeutic effects with altered cytokine secretion in an experimental acute colitis model.

Derivation of clinical-grade mesenchymal stromal cells from umbilical cord under chemically defined culture condition - platform for future clinical application

The use of animal serum in culture medium brings safety concerns and batch-to-batch variability, and thus may restrict the clinical use of ex vivo expanded mesenchymal stromal cells (MSCs). Clinically compliant MSCs should be developed in adherence to serum-free, xeno-free and chemically defined medium (S&XFM-CD). In this study, we develop a S&XFM-CD by replacing all serum components with synthetic alternatives for the derivation of clinical-grade umbilical cord-derived MSCs (UCMSCs). The critical aspects including characterization, safety concerns, potency and exogenous factors contamination risk of UCMSCs in S&XFM-CD are compared with serum-containing medium (SCM). UCMSCs in S&XFM-CD retain fibroblastic-like morphology and immunophenotype of MSCs, and exhibit superior clone efficiency, proliferation capacity, and osteogenic and chondrogenic differentiation potential compared with SCM. Moreover, UCMSCs in S&XFM-CD retain similar immunosuppressive potential, and exhibit superior secretion levels of bFGF, PDGF-BB and IGF-1 compared with SCM. In addition, UCMSCs in S&XFM-CD do not undergo transformation, preserve the normal karyotypes and genomic stability, and are less prone to senescence process after long-term in vitro culture, which conforms to the current guidance of international and national evaluation standard. The S&XFM-CD developed here may serve as a GMP-grade production platform of UCMSCs for future clinical application.

Mesenchymal stromal cells induce regulatory T cells via epigenetic conversion of human conventional CD4 T cells in vitro

Regulatory T cells (Treg) play a critical role in immune tolerance. The scarcity of Treg therapy clinical trials in humans has been largely due to the difficulty in obtaining sufficient Treg numbers. We performed a preclinical investigation on the potential of mesenchymal stromal cells (MSCs) to expand Treg in vitro to support future clinical trials. Human peripheral blood mononuclear cells from healthy donors were cocultured with allogeneic bone marrow‐derived MSCs expanded under xenogeneic‐free conditions. Our data show an increase in the counts and frequency of CD4⁺ CD25^high Foxp3⁺ CD127^low Treg cells (4‐ and 6‐fold, respectively) after a 14‐day coculture. However, natural Treg do not proliferate in coculture with MSCs. When purified conventional CD4 T cells (Tcon) are cocultured with MSCs, only cells that acquire a Treg‐like phenotype proliferate. These MSC‐induced Treg‐like cells also resemble Treg functionally, since they suppress autologous Tcon proliferation. Importantly, the DNA methylation profile of MSC‐induced Treg‐like cells more closely resembles that of natural Treg than of Tcon, indicating that this population is stable. The expression of PD‐1 is higher in Treg‐like cells than in Tcon, whereas the frequency of PDL‐1 increases in MSCs after coculture. TGF‐β levels are also significantly increased MSC cocultures. Overall, our data suggest that Treg enrichment by MSCs results from Tcon conversion into Treg‐like cells, rather than to expansion of natural Treg, possibly through mechanisms involving TGF‐β and/or PD‐1/PDL‐1 expression. This MSC‐induced Treg population closely resembles natural Treg in terms of phenotype, suppressive ability, and methylation profile.

Modulation of the in vitro angiogenic potential of human mesenchymal stromal cells from different tissue sources

Mesenchymal stromal cells (MSCs) have been widely exploited for the treatment of several conditions due to their intrinsic regenerative and immunomodulatory properties. MSC have demonstrated to be particularly relevant for the treatment of ischemic diseases, where MSC-based therapies can stimulate angiogenesis and induce tissue regeneration. Regardless of the condition targeted, recent analyses of MSC-based clinical trials have demonstrated limited benefits indicating a need to improve the efficacy of this cell product. Preconditioning MSC ex vivo through microenvironment modulation was found to improve MSC survival rate and thus prolong their therapeutic effect. This workstudy aims at enhancing the in vitro angiogenic capacity of a potential MSC-based medicinal product by comparing different sources of MSC and culture conditions. MSC from three different sources (bone marrow [BM], adipose tissue [AT], and umbilical cord matrix [UCM]) were cultured with xenogeneic-/serum-free culture medium under static conditions and their angiogenic potential was studied. Results indicated a higher in vitro angiogenic capacity of UCM MSC, compared with cells derived from BM and AT. Physicochemical preconditioning of UCM MSC through a microcarrier-based culture platform and low oxygen concentration (2% O₂ , compared with atmospheric air) increased the in vitro angiogenic potential of the cultured cells. Envisaging the clinical manufacturing of an allogeneic, off-the-shelf MSC-based product, preconditioned UCM MSC maintain the angiogenic gene expression profile upon cryopreservation and delivery processes in the conditions of our study. These results are expected to contribute to the development of MSC-based therapies in the context of angiogenesis.

Mesenchymal stem cells combined with traditional Chinese medicine (qi-fang-bi-min-tang) alleviates rodent allergic rhinitis

Mesenchymal stem cells (MSCs) have been proved to exert anti-inflammatory effects and regulate immune reactions. Traditional Chinese medicine (TCM), qi-fang-bi-min-tang, is effective for some patients with allergic diseases. However, it remains unclear whether MSCs combined with TCM could benefit the treatment of allergic rhinitis (AR). In this study, we reported an additional effect of TCM (qi-fang-bi-min-tang) on the therapy of AR under MSCs treatment. Intriguingly, we observed that TCM-treated MSCs significantly inhibited the symptoms of AR and reduced the pathological changes of nasal mucosa in ovalbumin (OVA)-induced rats. The expression levels of interferon γ (IFN-γ), interleukin-17 (IL-17), and IL-4 were significantly decreased in the plasma of AR rats after injection of TCM-treated MSCs. TCM-treated MSCs reduced the levels of histamine secreted by mast cells and immunoglobulin E (IgE) secreted by plasma cells. In addition, we found that MSCs combined with TCM had a better therapeutic effect than TCM alone on AR in an OVA-induced mouse model. After OVA induction, MSCs combined with TCM significantly reduced the ratio of T helper type 1 (Th1), Th2, and Th17, but increased the proportion of Treg in the spleen of mice. Consistently, the expression levels of IFN-γ, IL-4, and IL-17 were significantly decreased, but transforming growth factor-β1 was significantly increased in the plasma of AR mice after treated with TCM and MSCs. Our results from both rats and mice indicated that the effects of TCM combined with MSCs on the AR might be through regulating the secretion of Th1, Th2, and Th17 cytokines. This study suggested that TCM (qi-fang-bi-min-tang)-treated MSCs could be used in the clinical therapy of AR.

Impact of the type of microcarrier and agitation modes on the expansion performances of mesenchymal stem cells derived from umbilical cord

The present study proposed to compare the impact of agitation mode (static, orbital, and mechanical) on the culture of mesenchymal stem cells extracted from the Wharton's jelly of umbilical cords (WJ-MSC), in a clinical grade culture medium, using human platelet lysate and different xeno-free microcarriers. Attachment, expansion, and detachment performances were characterized by a new dedicated tool of microscopic image posttreatment, allowing an in situ cell counting without detachment step. Results showed that performances in static mode were not necessarily representative of those obtained in dynamic mode. Moreover, impacts on nutrient consumptions and metabolite productions were identified, such as a higher glutamine consumption when Cytodex-1 microcarriers were used. The detachment strategy used was relatively efficient for Star-Plus, Plastic-Plus, and Hillex II, but not sufficient for Cytodex-1. Despite Cytodex-1 presented promising attachment and expansion performances, Star-Plus and Plastic-Plus showed a better compromise, respectively, for the orbital and the mechanical agitation modes.

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.

Addressing the Manufacturing Challenges of Cell-Based Therapies

Exciting developments in the cell therapy field over the last decades have led to an increasing number of clinical trials and the first cell products receiving marketing authorization. In spite of substantial progress in the field, manufacturing of cell-based therapies presents multiple challenges that need to be addressed in order to assure the development of safe, efficacious, and cost-effective cell therapies.The manufacturing process of cell-based therapies generally requires tissue collection, cell isolation, culture and expansion (upstream processing), cell harvest, separation and purification (downstream processing), and, finally, product formulation and storage. Each one of these stages presents significant challenges that have been the focus of study over the years, leading to innovative and groundbreaking technological advances, as discussed throughout this chapter.Delivery of cell-based therapies relies on defining product targets while controlling process variable impact on cellular features. Moreover, commercial viability is a critical issue that has had damaging consequences for some therapies. Implementation of cost-effectiveness measures facilitates healthy process development, potentially being able to influence end product pricing.Although cell-based therapies represent a new level in bioprocessing complexity in every manufacturing stage, they also show unprecedented levels of therapeutic potential, already radically changing the landscape of medical care.

Mesenchymal stem cells in preclinical cancer cytotherapy: a systematic review

Mesenchymal stem cells (MSC) comprise a heterogeneous population of rapidly proliferating cells that can be isolated from adult (e.g., bone marrow, adipose tissue) as well as fetal (e.g., umbilical cord) tissues (termed bone marrow (BM)-, adipose tissue (AT)-, and umbilical cord (UC)-MSC, respectively) and are capable of differentiation into a wide range of non-hematopoietic cell types. An additional, unique attribute of MSC is their ability to home to tumor sites and to interact with the local supportive microenvironment which rapidly conceptualized into MSC-based experimental cancer cytotherapy at the turn of the century. Towards this purpose, both naïve (unmodified) and genetically modified MSC (GM-MSC; used as delivery vehicles for the controlled expression and release of antitumorigenic molecules) have been employed using well-established in vitro and in vivo cancer models, albeit with variable success. The first approach is hampered by contradictory findings regarding the effects of naïve MSC of different origins on tumor growth and metastasis, largely attributed to inherent biological heterogeneity of MSC as well as experimental discrepancies. In the second case, although the anti-cancer effect of GM-MSC is markedly improved over that of naïve cells, it is yet apparent that some protocols are more efficient against some types of cancer than others. Regardless, in order to maximize therapeutic consistency and efficacy, a deeper understanding of the complex interaction between MSC and the tumor microenvironment is required, as well as examination of the role of key experimental parameters in shaping the final cytotherapy outcome. This systematic review represents, to the best of our knowledge, the first thorough evaluation of the impact of experimental anti-cancer therapies based on MSC of human origin (with special focus on human BM-/AT-/UC-MSC). Importantly, we dissect the commonalities and differences as well as address the shortcomings of work accumulated over the last two decades and discuss how this information can serve as a guide map for optimal experimental design implementation ultimately aiding the effective transition into clinical trials.

Human umbilical cord blood plasma as an alternative to animal sera for mesenchymal stromal cells in vitro expansion - A multicomponent metabolomic analysis

Mesenchymal Stromal cells (MSCs) have a potential role in cell-based therapies. Foetal bovine serum (FBS) is used to supplement the basal cell culture medium but presents several disadvantages and risks. Other alternatives have been studied, including human umbilical cord blood plasma (hUCBP), aiming at the development of xeno-free culturing protocols. A comparative characterization of multicomponent metabolic composition of hUCBP and commercial FBS based on Nuclear Magnetic Resonance (NMR) spectroscopy and multivariate statistical analysis was performed. The analysis of ¹H-NMR spectra revealed both similarities and differences between the two proposed supplements. Similar metabolites (amino acids, glucose, lipids and nucleotides) were found in the hUCBP and FBS NMR spectra. The results show that the major difference between the metabolic profiles of the two proposed supplements are due to the significantly higher levels of glucose and lower levels of lactate, glutamate, alanine and branched chain amino acids in hUCBP. Similar or slightly different levels of important proteinogenic amino acids, as well as of nucleotides, lipids were found in the hUCBP and FBS. In order to validate it’s suitability for cell culture, umbilical cord-MSCs (UC-MSCs) and dental pulp stem cells (DPSCs) were expanded using hUCBP. In both hMSCs, in vitro culture with hUCBP supplementation presented similar to improved metabolic performances when compared to FBS. The two cell types tested expressed different optimum hUCBP percentage content. For DPSCs, the optimum hUCBP content was 6% and for UC-MSCs, 4%. Cultured hMSCs displayed no changes in senescence indicators, as well as maintained characteristic surface marker’s expression. FBS substitution was associated with an increase in early apoptosis events, in a dose dependent manner, as well as to slight up- and down-regulation of targeted gene’s expression. Tri-lineage differentiation capacity was also influenced by the substitution of FBS by hUCBP.

Biomimetic matrices for rapidly forming mineralized bone tissue based on stem cell-mediated osteogenesis

Bone regeneration, following fracture, relies on autologous and allogenic bone grafts. However, majority of fracture population consists of older individuals with poor quality bone associated with loss and/or modification of matrix proteins critical for bone formation and mineralization. Allografts suffer from same limitations and carry the risk of delayed healing, infection, immune rejection and eventual fracture. In this work, we apply a synergistic biomimetic strategy to develop matrices that rapidly form bone tissue - a critical aspect of fracture healing of weight bearing bones. Collagen matrices, enhanced with two selected key matrix proteins, osteocalcin (OC) and/or osteopontin (OPN), increased the rate and quantity of synthesized bone matrix by increasing mesenchymal stem/stromal cell (MSC) proliferation, accelerating osteogenic differentiation, enhancing angiogenesis and showing a sustained bone formation response from MSC obtained from a variety of human tissue sources (marrow, fat and umbilical cord). In vivo assessment of OC/OPN mineralized scaffolds in a critical sized-defect rabbit long-bone model did not reveal any foreign body reaction while bone tissue was being formed. We demonstrate a new biomimetic strategy to rapidly form mineralized bone tissue and secure a sustained bone formation response by MSC from multiple sources, thus facilitating faster patient recovery and treatment of non-union fractures in aging and diseased population. Acellular biomimetic matrices elicit bone regeneration response from MSC, obtained from multiple tissue sources, and can be used in variety of scaffolds and made widely available.

[Repair effects of rat adipose-derived stem cells on DNA damage induced by ultraviolet in chondrocytes]

Objective

To explore the DNA repair effect of rat adipose-derived stem cells (ADSCs) on chond-rocytes exposed to ultraviolet (UV) radiation.

Methods

ADSCs were isolated and cultured from the inguinal adipose tissue of Sprague Dawley rat by digestion with collagenase type I. ADSCs cell phenotype was assayed with flow cytometry. Multiple differentiation capability of ADSCs at passage 3 was identified with osteogenic and adipogenic induction. The chondrocytes were obtained from rat articular cartilage by digestion with collagenase type II and were identified with toluidine blue staining. The chondrocytes at passage 3 were irradiated with 40 J/m ² UV and cultured with normal medium (irradiated group), and medium containing the ADSCs supernatant (ADSCs supernatant group) or ADSCs was used for co-culture (ADSCs group) for 24 hours; no irradiation chondrocytes served as control group. The cell proliferation was estimated by MTS method. The expression of phosphorylated histone family 2A variant (γH2AX) was detected by immunofluorescence and Western blot.

Results

ADSCs presented CD29(+), CD44(+), CD106(-), and CD34(-); and results of the alizarin red staining and oil red O staining were positive after osteogenic and adipogenic induction. Cell proliferation assay demonstrated the absorbance ( A) values were 2.20±0.10 (control group), 1.34±0.04 (irradiated group), and 1.57±0.06 (ADSCs supernatant group), showing significant difference between groups ( P<0.05). Immunofluorescence and Western blot showed that the γH2AX protein expression was significantly increased in irradiated group, ADSCs supernatant group, and ADSCs group when compared with control group ( P<0.05), and the expression was significantly decreased in ADSCs supernatant group and ADSCs group when compared with irradiated group ( P<0.05), but no significant difference was found between ADSCs supernatant group and ADSCs group ( P>0.05).

Conclusion

ADSCs can increase the cell proliferation and down-regulate the γH2AX protein expression of irradiated cells, indicating ADSCs contribute to the repair of irradiated chondrocyte.

Culture Medium Supplements Derived from Human Platelet and Plasma: Cell Commitment and Proliferation Support

Present cell culture medium supplements, in most cases based on animal sera, are not fully satisfactory especially for the in vitro expansion of cells intended for human cell therapy. This paper refers to (i) an heparin-free human platelet lysate (PL) devoid of serum or plasma components (v-PL) and (ii) an heparin-free human serum derived from plasma devoid of PL components (Pl-s) and to their use as single components or in combination in primary or cell line cultures. Human mesenchymal stem cells (MSC) primary cultures were obtained from adipose tissue, bone marrow, and umbilical cord. Human chondrocytes were obtained from articular cartilage biopsies. In general, MSC expanded in the presence of Pl-s alone showed a low or no proliferation in comparison to cells grown with the combination of Pl-s and v-PL. Confluent, growth-arrested cells, either human MSC or human articular chondrocytes, treated with v-PL resumed proliferation, whereas control cultures, not supplemented with v-PL, remained quiescent and did not proliferate. Interestingly, signal transduction pathways distinctive of proliferation were activated also in cells treated with v-PL in the absence of serum, when cell proliferation did not occur, indicating that v-PL could induce the cell re-entry in the cell cycle (cell commitment), but the presence of serum proteins was an absolute requirement for cell proliferation to happen. Indeed, Pl-s alone supported cell growth in constitutively activated cell lines (U-937, HeLa, HaCaT, and V-79) regardless of the co-presence of v-PL. Plasma- and plasma-derived serum were equally able to sustain cell proliferation although, for cells cultured in adhesion, the Pl-s was more efficient than the plasma from which it was derived. In conclusion, the cells expanded in the presence of the new additives maintained their differentiation potential and did not show alterations in their karyotype.

Recent Progress in Translation from Bench to a Pilot Clinical Study on Total Pulp Regeneration

Based on a preclinical bench study in dogs, a pilot clinical study was completed. Dental pulp stem cell (DPSC) subsets were isolated by mobilization by granulocyte colony-stimulating factor and expanded in good manufacturing practice conditions. The safety and efficacy of their autologous transplantation for total pulp regeneration was assessed in 5 patients with irreversible pulpitis. The quality control of the DPSC subsets was ensured by the absence of contamination and karyotype aberrations, and positive expression of stem cell markers. The clinical safety assessment was based on laboratory and radiographic evaluations, demonstrating no evidence of toxicity and adverse events. The efficacy was determined by the recovery of a sound positive response to the electric pulp test within 4 weeks and by the robust signal intensity of magnetic resonance imaging in the root canal at 24 weeks. The functional recovery of pulp tissue was determined by lateral mineralized tissue formation detected by cone beam computed tomography. This review presents a summary of the accumulating data in translation from bench to a pilot clinical study, demonstrating potential clinical utility of DPSC subsets for total pulp regeneration in endodontics.

Human mesenchymal stem cells maintain their phenotype, multipotentiality, and genetic stability when cultured using a defined xeno-free human plasma fraction

Background

Mesenchymal stem cells (MSCs) show promising characteristics for their use in advanced therapy medicinal products. However, there are some unresolved concerns, such as the use of animal components for their expansion.

In this study we assessed the suitability of a xeno-free supplement for cell culture (SCC) derived from human plasma, to culture and expand human MSCs (hMSCs) from different origins. Characteristics of viable cultured hMSCs such as genetic stability, phenotype and multipotentiality were qualitatively evaluated.

Methods

hMSCs from adipose tissue (AT), bone marrow (BM) and umbilical cord (UC) and supplier sources (commercial/non-commercial) were used. After hMSCs expansion in a xeno-free medium, classical hMSCs markers were studied by immunocytochemistry, and genetic stability was tested by classic karyotyping. The capacity of hMSCs to differentiate into adipogenic, osteogenic, and chondrogenic cells in differentiation media was assessed using different staining. Different lots of SCC were used to assure consistency between batches.

Results

All hMSCs tested maintained their morphology and adherence to plastic during their expansion, and preserved their genetic stability, phenotype and differentiation potential. No differences were observed when using different lots of SCC. Moreover, the proliferation rate, evaluated as population doubling time (PDT) of commercial BM and AT hMSCs, was higher in the xeno-free medium than in the control media provided by the suppliers of the cells (PDT of 4.6 for BM-hMSC and 6.4 for AT-hMSC in xeno-free medium, and 7.0 and 14.7 respectively in the commercial media). UC-hMSCs PDT was similar in all the media tested. When using non-commercial BM-hMSCs, PDT was lower in the xeno-free medium, but reverted to the control level with the addition of growth factors.

Conclusions

SCC-containing medium can be a feasible xeno-free alternative to expand hMSCs for advanced therapies.

Characterization of Human AB Serum for Mesenchymal Stromal Cell Expansion

BACKGROUND

So far, using human blood-derived components appears to be the most efficient and safest approach available for mesenchymal stromal cell (MSC) expansion. In this paper, we report on the characterization of human AB serum (AB HS) produced by using different plasma sources, and its use as an alternative supplement to MSC expansion.

METHODS

Two plasma sources were used for AB HS production: plasma removed from whole blood after 24 h of collection (PC > 24 h) and plasma, cryoprecipitate reduced (PCryoR). The biochemical profile and quality of the produced AB HS batches were analyzed and their ability to support MSC cell growth after different storage times (0, 3, 6, 9 and 12 months) was evaluated.

RESULTS

The two plasma sources used showed similar characteristics regarding biochemical constituents and quality parameters and were effective in promoting MSC growth. MSCs cultured in medium supplemented with 10% AB HS presented similar doubling times and cumulative population doublings when compared to the 10% fetal bovine serum(FBS)-supplemented culture while maintaining immunophenotype, functional features, and cytogenetic profile.

CONCLUSION

Overall, the results indicate that AB HS is an efficient FBS substitute and can be used for at least 12 months after production without impairing cell proliferation and quality.

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.

Serum and xeno-free, chemically defined, no-plate-coating-based culture system for mesenchymal stromal cells from the umbilical cord

OBJECTIVES

Umbilical cord mesenchymal stromal cells (UCMSCs) can be considered to become a new gold standard for MSC-based therapies. A serum and xeno-free, chemically defined and no-plate-coating-based culture system will greatly facilitate development of robust, clinically acceptable bioprocesses for reproducibly generating quality-assured UCMSCs.

MATERIALS AND METHODS

In this study, we report for the first time, such a serum-free, xeno-free, completely chemically defined and no-plate-coating-based culture system for the isolation and expansion of UCMSCs, whose biological characteristics were evaluated and compared with serum-containing medium (SCM) methods.

RESULTS

This culture system not only supported UCMSC primary cultures but also allowed for their expansion at low seeding density. Compared to SCM, UCMSCs in SFM exhibited (i) higher proliferative and colony-forming capacities; (ii) distinctly different morphologies; (iii) similar phenotype; (iv) similar pluripotency-associated marker expression; (v) superior osteogenic, but reduced adipogenic differentiation capacitities. In addition, UCMSCs cultured in SFM retained similar immunomodulatory properties to those in SCM.

CONCLUSIONS

Our findings demonstrate the feasibility of isolating and expanding UCMSCs in a completely serum-free, xeno-free, chemically defined and no-plate-coating-based culture system and represent an important step forward for development of robust, clinically acceptable bioprocesses for UCMSCs. Further, this provides a superior study platform for UCMSCs biology in a controlled environment.

Stirred tank bioreactor culture combined with serum-/xenogeneic-free culture medium enables an efficient expansion of umbilical cord-derived mesenchymal stem/stromal cells

Mesenchymal stem/stromal cells (MSC) are being widely explored as promising candidates for cell-based therapies. Among the different human MSC origins exploited, umbilical cord represents an attractive and readily available source of MSC that involves a non-invasive collection procedure. In order to achieve relevant cell numbers of human MSC for clinical applications, it is crucial to develop scalable culture systems that allow bioprocess control and monitoring, combined with the use of serum/xenogeneic (xeno)-free culture media. In the present study, we firstly established a spinner flask culture system combining gelatin-based Cultispher(®) S microcarriers and xeno-free culture medium for the expansion of umbilical cord matrix (UCM)-derived MSC. This system enabled the production of 2.4 (±1.1) x10(5) cells/mL (n = 4) after 5 days of culture, corresponding to a 5.3 (±1.6)-fold increase in cell number. The established protocol was then implemented in a stirred-tank bioreactor (800 mL working volume) (n = 3) yielding 115 million cells after 4 days. Upon expansion under stirred conditions, cells retained their differentiation ability and immunomodulatory potential. The development of a scalable microcarrier-based stirred culture system, using xeno-free culture medium that suits the intrinsic features of UCM-derived MSC represents an important step towards a GMP compliant large-scale production platform for these promising cell therapy candidates.

Advances in the Treatment of Ischemic Diseases by Mesenchymal Stem Cells

Ischemic diseases are a group of diseases, including ischemic cerebrovascular disease, ischemic cardiomyopathy (ICM), and diabetic foot as well as other diseases which are becoming a leading cause of morbidity and mortality in the whole world. Mesenchymal stem cells (MSCs) have been used to treat a variety of ischemic diseases in animal models and clinical trials. Lots of recent publications demonstrated that MSCs therapy was safe and relieved symptoms in patients of ischemic disease. However, many factors could influence therapeutic efficacy including route of delivery, MSCs' survival and residential rate in vivo, timing of transplantation, particular microenvironment, and patient's clinical condition. In this review, the current status, therapeutic potential, and the detailed factors of MSCs-based therapeutics for ischemic cerebrovascular disease, ICM, and diabetic foot are presented and discussed. We think that MSCs transplantation would constitute an ideal option for patients with ischemic diseases.

Magnetic induction heating of superparamagnetic nanoparticles during rewarming augments the recovery of hUCM-MSCs cryopreserved by vitrification

Cryopreservation by vitrification has been recognized as a promising strategy for long-term banking of living cells. However, the difficulty to generate a fast enough heating rate to minimize devitrification and recrystallization-induced intracellular ice formation during rewarming is one of the major obstacles to successful vitrification. We propose to overcome this hurdle by utilizing magnetic induction heating (MIH) of magnetic nanoparticles to enhance rewarming. In this study, superparamagnetic (SPM) Fe3O4 nanoparticles were synthesized by a chemical coprecipitation method. We successfully applied the MIH of Fe3O4 nanoparticles for rewarming human umbilical cord matrix mesenchymal stem cells (hUCM-MSCs) cryopreserved by vitrification. Our results show that extracellular Fe3O4 nanoparticles with MIH may efficiently suppress devitrification and/or recrystallization during rewarming and significantly improve the survival of vitrified cells. We further optimized the concentration of Fe3O4 nanoparticles and the current of an alternating current (AC) magnetic field for generating the MIH to maximize cell viability. Our results indicate that MIH in an AC magnetic field with 0.05% (w/v) Fe3O4 nanoparticles significantly facilitates rewarming and improves the cryopreservation outcome of hUCM-MSCs by vitrification. The application of MIH of SPM nanoparticles to achieve rapid and spatially homogeneous heating is a promising strategy for enhanced cryopreservation of stem cells by vitrification.

STATEMENT OF SIGNIFICANCE

Here we report the successful synthesis and application of Fe3O4 nanoparticles for magnetic induction heating (MIH) to enhance rewarming of vitrification-cryopreserved human umbilical cord matrix mesenchymal stem cells (hUCM-MSCs). We found that MIH-enhanced rewarming greatly improves the survival of vitrification-cryopreserved hUCM-MSCs. Moreover, the hUCM-MSCs retain their intact stemness and multilineage potential of differentiation post cryopreservation by vitrification with the MIH-enhanced rewarming. Therefore, the novel MIH-enhanced cell vitrification is valuable to facilitate the long-term storage of hUCM-MSCs and possibly many other important cells to meet their ever-increasing demand by the burgeoning cell-based medicine.

In vitro induction and differentiation of umbilical cord mesenchymal stem cells into neuron-like cells by all-trans retinoic acid

AIM

To determine the optimal concentration for inducing the differentiation of human umbilical cord-derived mesenchymal stem cells (hUC-MSCs) into neuron-like cells, although it is understood that all-trans retinoic acid (ATRA) regulates cell proliferation in the nervous system by modulating the balance between mitosis and apoptosis.

METHODS

The abilities of ATRA to promote apoptosis as well as neural differentiation were assessed in cultured hUC-MSCs by morphological observation, MTT assay, annexin V-FITC/PI flow cytometry and immunocytochemistry.

RESULTS

The data showed that low concentrations of ATRA (0.5 µmol, 0.25 µmol) had no effect on the number of cells. However, treatment with 1.0 µmol or 2.0 µmol ATRA induced a 24.16% and 52.67% reduction in cell number, respectively, compared with vehicle-treated cultures. Further, 4.0 µmol ATRA had a potent effect on cell number, with almost no adherent cells recovered after 24h. We further showed that 0.5 µmol ATRA caused these cells to express characteristic markers of neuronal progenitor cells.

CONCLUSION

Taken together, we conclude that ATRA has a dose-dependent influence on the neural differentiation and apoptosis of hUC-MSCs. These findings have implications on the use of ATRA-differentiated hUC-MSCs for the study of neural degeneration diseases.

Culture of human mesenchymal stem cells using a candidate pharmaceutical grade xeno-free cell culture supplement derived from industrial human plasma pools

INTRODUCTION

Fetal bovine serum (FBS) is an animal product used as a medium supplement. The animal origin of FBS is a concern if cultured stem cells are to be utilized for human cell therapy. Therefore, a substitute for FBS is desirable. In this study, an industrial, xeno-free, pharmaceutical-grade supplement for cell culture (SCC) under development at Grifols was tested for growth of human mesenchymal stem cells (hMSCs), cell characterization, and differentiation capacity.

METHODS

SCC is a freeze-dried product obtained through cold-ethanol fractionation of industrial human plasma pools from healthy donors. Bone marrow-derived hMSC cell lines were obtained from two commercial suppliers. Cell growth was evaluated by culturing hMSCs with commercial media or media supplemented with SCC or FBS. Cell viability and cell yield were assessed with an automated cell counter. Cell surface markers were studied by indirect immunofluorescence assay. Cells were cultured then differentiated into adipocytes, chondrocytes, osteoblasts, and neurons, as assessed by specific staining and microscopy observation.

RESULTS

SCC supported the growth of commercial hMSCs. Starting from the same number of seeded cells in two consecutive passages of culture with medium supplemented with SCC, hMSC yield and cell population doubling time were equivalent to the values obtained with the commercial medium and was consistent among lots. The viability of hMSCs was higher than 90%, while maintaining the characteristic phenotype of undifferentiated hMSCs (positive for CD29, CD44, CD90, CD105, CD146, CD166 and Stro-1; negative for CD14 and CD19). Cultured hMSCs maintained the potential for differentiation into adipocytes, chondrocytes, osteoblasts, and neurons.

CONCLUSIONS

The tested human plasma-derived SCC sustains the adequate growth of hMSCs, while preserving their differentiation capacity. SCC can be a potential candidate for cell culture supplement in advanced cell therapies.

Optimization of pre-transplantation conditions to enhance the efficacy of mesenchymal stem cells

Mesenchymal stem cells (MSCs) are considered a potential tool for cell based regenerative therapy due to their immunomodulatory property, differentiation potentials, trophic activity as well as large donor pool. Poor engraftment and short term survival of transplanted MSCs are recognized as major limitations which were linked to early cellular ageing, loss of chemokine markers during ex vivo expansion, and hyper-immunogenicity to xeno-contaminated MSCs. These problems can be minimized by ex vivo expansion of MSCs in hypoxic culture condition using well defined or xeno-free media i.e., media supplemented with growth factors, human serum or platelet lysate. In addition to ex vivo expansion in hypoxic culture condition using well defined media, this review article describes the potentials of transient adaptation of expanded MSCs in autologous serum supplemented medium prior to transplantation for long term regenerative benefits. Such transient adaptation in autologous serum supplemented medium may help to increase chemokine receptor expression and tissue specific differentiation of ex vivo expanded MSCs, thus would provide long term regenerative benefits.

MSCs conditioned media and umbilical cord blood plasma metabolomics and composition

Human mesenchymal stem cells (hMSCs) from umbilical cord (UC) blood (UCB) and matrix are tested clinically for a variety of pathologies but in vitro expansion using culture media containing fetal bovine serum (FBS) is essential to achieve appropriate cell numbers for clinical use. Human UCB plasma (hUCBP) can be used as a supplement for hMSCs culture, since UCB is rich in soluble growth factors and due to worldwide increased number of cryopreserved UCB units in public and private banks, without the disadvantages listed for FBS. On the other hand, the culture media enriched in growth factors produced by these hMSCs in expansion (Conditioned medium--CM) can be an alternative to hMSCs application. The CM of the hMSCs from the UC might be a better therapeutic option compared to cell transplantation, as it can benefit from the local tissue response to the secreted molecules without the difficulties and complications associated to the engraftment of the allo- or xeno-transplanted cells. These facts drove us to know the detailed composition of the hUCBP and CM, by 1H-NMR and Multiplexing LASER Bead Technology. hUCBP is an adequate alternative for the FBS and the CM and hUCBP are important sources of growth factors, which can be used in MSCs-based therapies. Some of the major proliferative, chemotactic and immunomodulatory soluble factors (TGF-β, G-CSF, GM-CSF, MCP-1, IL-6, IL-8) were detected in high concentrations in CM and even higher in hUCBP. The results from 1H-NMR spectroscopic analysis of CM endorsed a better understanding of hMSCs metabolism during in vitro culture, and the relative composition of several metabolites present in CM and hUCBP was obtained. The data reinforces the potential use of hUCBP and CM in tissue regeneration and focus the possible use of hUCBP as a substitute for the FBS used in hMSCs in vitro culture.

Strategies to improve homing of mesenchymal stem cells for greater efficacy in stem cell therapy

Stem/progenitor cell-based therapeutic approach in clinical practice has been an elusive dream in medical sciences, and improvement of stem cell homing is one of major challenges in cell therapy programs. Stem/progenitor cells have a homing response to injured tissues/organs, mediated by interactions of chemokine receptors expressed on the cells and chemokines secreted by the injured tissue. For improvement of directed homing of the cells, many techniques have been developed either to engineer stem/progenitor cells with higher amount of chemokine receptors (stem cell-based strategies) or to modulate the target tissues to release higher level of the corresponding chemokines (target tissue-based strategies). This review discusses both of these strategies involved in the improvement of stem cell homing focusing on mesenchymal stem cells as most frequent studied model in cellular therapies.

A serum-free medium developed for in vitro expansion of murine intestinal stem cells

Intestinal stem cells (ISCs) are located at the base of the intestinal crypts and have the ability to self-renew as well as to differentiate into mature epithelial cells. Recently, ISCs have received much attention for the treatment of many intestinal diseases. However, many challenges face those studying ISCs because insufficient ISCs are available. Therefore, the development of a culture medium for ISC expansion is an important necessity for basic research and clinical application. In this study, we described the technique used to develop a serum-free medium for expanding ISCs in vitro. Furthermore, five serum substitutes were selected and optimized in order to maintain the long-term proliferation and enteroid-forming ability of ISCs: (i) ethanolamine; (ii) ascorbic acid phosphate; (iii) transferrin; (iv) glutathione; and (v) sodium selenite. Analysis of gene expression of Lgr5, Bmi1, Msi1 and PTEN demonstrated that our serum-free medium sustained the expression of genes involved in ISC-related functions in the expanded ISCs. Additionally, the expression intensity of surface markers, including Lgr5, CD24 and CD44, on serum-free expanded cells in crypts was greatly increased. Taken together, our results demonstrate that the number of ISCs can be expanded and their functionality maintained in our serum-free medium, indicating the suitability of this serum-free expansion medium for increasing the numbers of ICSs available for basic research and clinical applications in the future.

Editorial: stem cell engineering - discovery, diagnostics and therapies

Stem cell engineering - discovery, diagnostics and therapies: This Special Issue is edited by Brenda Ogle and Sean Palecek and is based on presentations from the Third International Conference on Stem Cell Engineering, co-sponsored by the Society of Biological Engineering and the International Society for Stem Cell Research, held in Seattle, WA from April 29-May 2, 2012.

Alternative xeno-free biomaterials derived from human umbilical cord for the self-renewal ex-vivo expansion of mesenchymal stem cells

Mesenchymal stem cells (MSCs) are attractive candidates for novel cell-therapy applications. However, the in vitro expansion of MSCs typically depends on the presence of fetal bovine serum (FBS) and coating materials derived from animal sources, which may cause contamination in clinical applications. In this study, we investigated whether human umbilical cord extract (UCE) could serve as a serum replacement and whether collagen purified from umbilical cord (UC-collagen) could act as an extracellular matrix (ECM) for the in vitro culture of MSCs derived from human UC (UC-MSCs). A total of 5.61 ± 0.54 mg UCE and 18.41 ± 2.42 mg collagen were extracted, and 1.3 ± 0.2 × 10⁵ cells were isolated from 1 g of UC, as determined by the expression of typical MSC surface markers. Importantly, the proliferation and stemness of the UC-MSCs cultured with the UCE media were similar to those cultured under FBS conditions on UC-collagen-treated plates for eight passages. Based on these results, we suggest that UCs, which are discarded as medical waste, represent a viable alternative source of xeno-free biomaterials to replace animal-derived serum and ECM materials for the cultivation of various cell types, including UC-MSCs, adipose tissue-derived MSCs, bone marrow-derived MSCs, and fibroblasts. This innovative xeno-free MSCs culture system can overcome many of the problems associated with immunogenicity, and it will further contribute to the enhancement of treatment efficiency.

Isolation method and xeno-free culture conditions influence multipotent differentiation capacity of human Wharton's jelly-derived mesenchymal stem cells

Introduction

Human Wharton’s jelly (WJ) has become a preferred source of mesenchymal stem cells (MSCs) whose clinical applications are limited by the use of adequate xeno-free (XF), in vitro manipulation conditions. Therefore, the objective of our study was to characterize WJ-derived MSCs (WJ-MSCs), isolated by different methods and cultured in a commercially available, MSC XF medium, not least of all by investigating their endothelial differentiation capacity.

Methods

WJ explants and enzymatically dissociated WJ cells were cultured in a defined, XF medium for MSCs. Adherent cells at passages 2 and 5 were characterized as MSCs by flow cytometry, MTT, real-time quantitative reverse transcription PCR, and functional multipotent differentiation assays. The endothelial differentiation capacity of MSCs isolated and expanded until passage 2 in the MSC XF medium, and then subcultured for five passages in a commercially available endothelial growth medium (group A), was assessed over serial passages, as compared to adherent WJ-derived cells isolated and expanded for five consecutive passages in the endothelial medium (group B).

Results

The MSC phenotype of WJ explant- and pellet-derived cells, isolated and expanded in the MSC XF medium, was proven based on the expression of CD44/CD73/CD90/CD105 surface markers and osteo-/adipo-/chondrogenic multipotent differentiation potential, which differed according to the isolation method and/or passage number. Upon exposure to endothelial differentiation cues, cells belonging to group A did not exhibit endothelial cell characteristics over serial passages; by contrast, WJ pellet-derived cells belonging to group B expressed endothelial characteristics at gene, protein and functional levels, potentially due to culture conditions favoring the isolation of other stem/progenitor cell types than MSCs, able to give rise to an endothelial progeny.

Conclusions

The use of defined, MSC XF media for isolation and expansion of human WJ-MSCs is a prerequisite for the establishment of their real endothelial differentiation capacity, as candidates for clinical therapy applications. Thus, the standardization of WJ-MSCs isolation and culture expansion techniques in defined, MSC XF media, for their accurate characterization, would be a priority in the stem cell research field.