Umbilical cord fibroblasts: Could they be considered as mesenchymal stem cells?

Characterization and therapeutic applications of mesenchymal stem cells for regenerative medicine

BACKGROUND

Mesenchymal stem cells (MSCs) are multipotent, genomic stable, self-renewable, and culturally expandable adult stem cells. MSCs facilitate tissue development, maintenance and repair, and produce secretory factors that support engraftment and trophic functions, marking them an attractive option in cell therapy, regenerative medicine and tissue engineering.

METHOD

In this review, we summarize the recent researches regarding the isolation and characterization of MSCs, therapeutic applications and advanced engineering techniques. We also discuss the advantages and limitations that remain to be overcome for MSCs based therapy.

RESULTS

It has been demonstrated that MSCs are able to modulate endogenous tissue and immune cells. Preclinical studies and early phase clinical trials have shown their great potential for tissue engineering of bone, cartilage, marrow stroma, muscle, fat, and other connective tissues.

CONCLUSIONS

MSC-based therapy show considerable promise to rebuild damaged or diseased tissues, which could be a promising therapeutic method for regeneration medicine.

A novel method to isolate mesenchymal stem cells from mouse umbilical cord

Mesenchymal stem cells (MSCs), derived from various tissues, are considered an ideal cell source for clinical use, among which MSCs from the umbilical cord exhibit advantages over those from adult tissues. In preclinical studies, mouse models and xenogeneic MSC treatment are most commonly used to imitate diseases and clinical practice, respectively. However, the efficiency of cross-species therapy remains controversial, making it difficult to elucidate the underlying mechanisms. Thus, allogeneic therapy may be more instructive and meaningful in clinical use. To confirm this hypothesis, the present study established a novel method for the isolation and expansion of MSCs from mouse umbilical cords (mUC-MSCs) to support in vivo experiments in mice. MSCs were isolated from mUCs and mouse bone marrow (mBM), and then identified by flow cytometry. The differences in mUC-MSCs and mBM-MSCs were analyzed using a growth curve and their differentiation ability. The results showed that the harvested cells exhibited general characteristics of MSCs and possessed the capacity for long-term culture. Despite having similar morphology and surface antigens to MSCs derived from mouse bone marrow, the mUC-MSCs showed differences in purification, proliferation, stem cell markers and differentiation. In addition to detailed characterization, the present study verified the presence of Toll-like receptor 3 (TLR3), an important component of immune responses, in mUC-MSCs. It was found that the activation of TLR3 upregulated the levels of stemness-related proteins, and enhanced the secretion and mRNA levels of inflammatory cytokines in the pre-treated mUC-MSCs. Collectively, the results of the present study provide further insight into the features of newly established mUC-MSCs, providing novel evidence for the selection of murine MSCs and their responses to TLR3 priming.

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.

Comparative studies of mesenchymal stem cells derived from different cord tissue compartments - The influence of cryopreservation and growth media

INTRODUCTION

We have identified some critical aspects concerning umbilical cord tissue mesenchymal stem cells: the lack of standards for cell isolation, expansion and cryopreservation, the lack of unanimous opinions upon their multilineage differentiation potential and the existence of very few results related to the functional characterization of the cells isolated from cryopreserved umbilical cord tissue. Umbilical cord tissue cryopreservation appears to be the optimal solution for umbilical cord tissue mesenchymal stem cells storage for future clinical use. Umbilical cord tissue cryopreservation allows mesenchymal stem cells isolation before expected use, according with the specific clinical applications, by different customized isolation and expansion protocols agreed by cell therapy institutions.

METHODS

Using an optimized protocol for umbilical cord tissue cryopreservation in autologous cord blood plasma, isolation explant method and growth media supplemented with FBS or human serum, we performed comparative studies with respect to the characteristics of mesenchymal stem cells (MSC) isolated from different compartments of the same umbilical cord tissue such as Wharton's jelly, vein, arteries, before cryopreservation (pre freeze) and after cryopreservation (post thaw).

RESULTS

Expression of histochemical and immunohistochemical markers as well as electron microscopy observations revealed similar adipogenic, chondrogenic and osteogenic differentiation capacity for cells isolated from pre freeze and corresponding post thaw tissue fragments of Wharton's jelly, vein or arteries of the same umbilical cord tissue, regardless growth media used for cells isolation and expansion.

DISCUSSION

Our efficient umbilical cord tissue cryopreservation protocol is reliable for clinical applicability of mesenchymal stem cells that could next be isolated and expanded in compliance with future accepted standards.

Mesenchymal stem cells in maxillary sinus augmentation: A systematic review with meta-analysis

AIM: To investigate the effectiveness of mesenchymal stem cells (MSCs) in maxillary sinus augmentation (MSA), with various scaffold materials.

METHODS: MEDLINE, EMBASE and SCOPUS were searched using keywords such as sinus graft, MSA, maxillary sinus lift, sinus floor elevation, MSC and cell-based, in different combinations. The searches included full text articles written in English, published over a 10-year period (2004-2014). Inclusion criteria were clinical/radiographic and histologic/ histomorphometric studies in humans and animals, on the use of MSCs in MSA. Meta-analysis was performed only for experimental studies (randomized controlled trials and controlled trials) involving MSA, with an outcome measurement of histologic evaluation with histomorphometric analysis reported. Mean and standard deviation values of newly formed bone from each study were used, and weighted mean values were assessed to account for the difference in the number of subjects among the different studies. To compare the results between the test and the control groups, the differences of regenerated bone in mean and 95% confidence intervals were calculated.

RESULTS: Thirty-nine studies (18 animal studies and 21 human studies) published over a 10-year period (between 2004 and 2014) were considered to be eligible for inclusion in the present literature review. These studies demonstrated considerable variation with respect to study type, study design, follow-up, and results. Meta-analysis was performed on 9 studies (7 animal studies and 2 human studies). The weighted mean difference estimate from a random-effect model was 9.5% (95%CI: 3.6%-15.4%), suggesting a positive effect of stem cells on bone regeneration. Heterogeneity was measured by the I² index. The formal test confirmed the presence of substantial heterogeneity (I² = 83%, P < 0.0001). In attempt to explain the substantial heterogeneity observed, we considered a meta-regression model with publication year, support type (animal vs humans) and follow-up length (8 or 12 wk) as covariates. After adding publication year, support type and follow-up length to the meta-regression model, heterogeneity was no longer significant (I² = 33%, P = 0.25).

CONCLUSION: Several studies have demonstrated the potential for cell-based approaches in MSA; further clinical trials are needed to confirm these results.