Functional and immunophenotypic characteristics of isolated CD105(+) and fibroblast(+) stromal cells from AML: implications for their plasticity along endothelial lineage

Identification and characterisation of maternal perivascular SUSD2+ placental mesenchymal stem/stromal cells

Mesenchymal stem cells (MSCs) that meet the International Society for Cellular Therapy (ISCT) criteria are obtained from placental tissue by plastic adherence. Historically, no known single marker was available for isolating placental MSCs (pMSCs) from the decidua basalis. As the decidua basalis is derived from the regenerative endometrium, we hypothesised that SUSD2, an endometrial perivascular MSC marker, would purify maternal perivascular pMSC. Perivascular pMSCs were isolated from the maternal placenta using SUSD2 magnetic bead sorting and assessed for the colony-forming unit-fibroblasts (CFU-F), surface markers, and in vitro differentiation into mesodermal lineages. Multi-colour immunofluorescence was used to colocalise SUSD2 and α-SMA, a perivascular marker in the decidua basalis. Placental stromal cell suspensions comprised 5.1%SUSD2⁺ cells. SUSD2 magnetic bead sorting of the placental stromal cells increased their purity approximately two-fold. SUSD2⁺ pMSCs displayed greater CFU-F activity than SUSD2^- stromal fibroblasts (pSFs). However, both SUSD2⁺ pMSC and SUSD2^- pSF underwent mesodermal differentiation in vitro, and both expressed the ISCT surface markers. Higher percentages of cultured SUSD2⁺ pMSCs expressed the perivascular markers CD146, CD140b, and SUSD2 than SUSD2^- pSFs. These findings suggest that SUSD2 is a single marker that enriches maternal pMSCs, suggesting they may originate from eMSC. Placental decidua basalis can be used as an alternative source of MSC for clinical translation in situations where there is no access to endometrial tissue.

Alteration Analysis of Bone Marrow Mesenchymal Stromal Cells from De Novo Acute Myeloid Leukemia Patients at Diagnosis

Bone marrow (BM)-derived mesenchymal stromal cells (MSCs) frequently display alterations in several hematologic disorders, such as acute lymphoid leukemia, acute myeloid leukemia (AML), and myelodysplastic syndromes. In acute leukemias, it is not clear whether MSC alterations contribute to the development of the malignant clone or whether they are simply the effect of tumor expansion on the microenvironment. We extensively investigated the characteristics of MSCs isolated from the BM of patients with de novo AML at diagnosis (L-MSCs) in terms of phenotype (gene and protein expression, apoptosis and senescence levels, DNA double-strand break formation) and functions (proliferation and clonogenic potentials, normal and leukemic hematopoiesis-supporting activity). We found that L-MSCs show reduced proliferation capacity and increased apoptosis levels compared with MSCs from healthy controls. Longer population doubling time in L-MSCs was not related to the AML characteristics at diagnosis (French-American-British type, cytogenetics, or tumor burden), but was related to patient age and independently associated with poorer patient outcome, as was cytogenetic prognostic feature. Analyzing, among others, the expression of 93 genes, we found that proliferative deficiency of L-MSCs was associated with a perivascular feature at the expense of the osteo-chondroblastic lineage with lower expression of several niche factors, such as KITLG, THPO, and ANGPT1 genes, the cell adhesion molecule VCAM1, and the developmental/embryonic genes, BMI1 and DICER1. L-MSC proliferative capacity was correlated positively with CXCL12, THPO, and ANGPT1 expression and negatively with JAG1 expression. Anyway, these changes did not affect their in vitro capacity to support normal hematopoiesis and to modify leukemic cell behavior (protection from apoptosis and quiescence induction). Our findings indicate that BM-derived MSCs from patients with newly diagnosed AML display phenotypic and functional alterations such as proliferative deficiency that could be attributed to tumor progression, but does not seem to play a special role in the leukemic process.

Mesenchymal Stem and Progenitor Cells in Normal and Dysplastic Hematopoiesis-Masters of Survival and Clonality?

Myelodysplastic syndromes (MDS) are malignant hematopoietic stem cell disorders that have the capacity to progress to acute myeloid leukemia (AML). Accumulating evidence suggests that the altered bone marrow (BM) microenvironment in general, and in particular the components of the stem cell niche, including mesenchymal stem cells (MSCs) and their progeny, play a pivotal role in the evolution and propagation of MDS. We here present an overview of the role of MSCs in the pathogenesis of MDS, with emphasis on cellular interactions in the BM microenvironment and related stem cell niche concepts. MSCs have potent immunomodulatory capacities and communicate with diverse immune cells, but also interact with various other cellular components of the microenvironment as well as with normal and leukemic stem and progenitor cells. Moreover, compared to normal MSCs, MSCs in MDS and AML often exhibit altered gene expression profiles, an aberrant phenotype, and abnormal functional properties. These alterations supposedly contribute to the “reprogramming” of the stem cell niche into a disease-permissive microenvironment where an altered immune system, abnormal stem cell niche interactions, and an impaired growth control lead to disease progression. The current article also reviews molecular targets that play a role in such cellular interactions and possibilities to interfere with abnormal stem cell niche interactions by using specific targeted drugs.

Endothelial Progenitor Cell Fraction Contained in Bone Marrow-Derived Mesenchymal Stem Cell Populations Impairs Osteogenic Differentiation

In bone tissue engineering (TE) endothelial cell-osteoblast cocultures are known to induce synergies of cell differentiation and activity. Bone marrow mononucleated cells (BMCs) are a rich source of mesenchymal stem cells (MSCs) able to develop an osteogenic phenotype. Endothelial progenitor cells (EPCs) are also present within BMC. In this study we investigate the effect of EPCs present in the BMC population on MSCs osteogenic differentiation. Human BMCs were isolated and separated into two populations. The MSC population was selected through plastic adhesion capacity. EPCs (CD34⁺ and CD133⁺) were removed from the BMC population and the resulting population was named depleted MSCs. Both populations were cultured over 28 days in osteogenic medium (Dex⁺) or medium containing platelet lysate (PL). MSC population grew faster than depleted MSCs in both media, and PL containing medium accelerated the proliferation for both populations. Cell differentiation was much higher in Dex⁺ medium in both cases. Real-time RT-PCR revealed upregulation of osteogenic marker genes in depleted MSCs. Higher values of ALP activity and matrix mineralization analyses confirmed these results. Our study advocates that absence of EPCs in the MSC population enables higher osteogenic gene expression and matrix mineralization and therefore may lead to advanced bone neoformation necessary for TE constructs.

Optimization of the isolation and expansion method of human mediastinal-adipose tissue derived mesenchymal stem cells with virally inactivated GMP-grade platelet lysate

Mesenchymal stem cells (MSCs) are adult multipotent cells currently employed in several clinical trials due to their immunomodulating, angiogenic and repairing features. The adipose tissue is certainly considered an eligible source of MSCs. Recently, putative adipose tissue derived MSCs (ADMSCs) have been isolated from the mediastinal depots. However, very little is known about the properties, the function and the potential of human mediastinal ADMSCs (hmADMSCs). However, the lack of standardized methodologies to culture ADMSCs prevents comparison across. Herein for the first time, we report a detailed step by step description to optimize the isolation and the expansion methodology of hmADMSCs using a virally inactivated good manufacturing practice (GMP)-grade platelet lysate, highlighting the critical aspects of the procedure and providing useful troubleshooting suggestions. Our approach offers a reproducible system which could provide standardization across laboratories. Moreover, our system is time and cost effective, and it can provide a reproducible source of adipose stem cells to enable future studies to unravel new insights regard this promising stem cell population.

Differentiation of synovial CD-105(+) human mesenchymal stem cells into chondrocyte-like cells through spheroid formation

Mesenchymal stem cells (MSCs) have the capacity to differentiate into several cell lineages, some of which can generate bone, cartilage, or adipose tissue. The presence of MSCs in the synovial membrane was recently reported. Data from comparative studies of MSCs derived from various mesenchymal tissues suggest that MSCs from synovial membranes have a superior chondrogenesis capacity. Previous chondrogenic differentiation studies have used the total population of MSCs, including cells with several MSC markers, such as CD44, CD90, CD105, or CD73. However the chondrogenic capacity of an individual population of MSCs has not been examined. Our aim was to study the chondrogenic capacity of the cellular MSC subset, CD105(+), derived from synovial membrane tissues of patients with osteoarthritis (OA) and normal donors. The tissues were digested with a cocktail of collagenase/dispase and the isolated MSCs were seeded into plates. The subpopulation of CD105(+)-MSCs was separated using a magnetic separator. The MSCs were then differentiated towards chondrocyte-like cells using a specific medium to promote spheroid formation. Spheroids were collected after 14, 28, and 46 days in chondrogenic medium and stained with hematoxylin, eosin, Safranin O or Alcian blue to evaluate the extracellular matrix. Immunohistochemistry was performed to study collagen types I (COLI) and II (COLII) and aggrecan expression. Phenotypic characterization of the isolated CD105(+)-MSCs shows that these cells are also positive for CD90 and CD44, but negatives for CD34 and CD45. In addition, this cellular subset expressed Sox-9. Spheroids appeared after 7 days in culture in the presence of chondrogenic medium. Our studies show no differences between MSCs obtained from OA and normal synovial membranes during chondrogenesis. The morphological analysis of spheroids revealed characteristics typical of chondrocyte cells. The intensity of Safranin O, Alcian blue and aggrecan staining was positive and constant throughout the culture period. However, the intensity of COL2 staining was higher at 28 days (84.29 +/- 0.1 U) than at 46 days (61.28 +/- 01 U), while COL1 staining was not detected in any samples analyzed. These results were confirmed by reverse transcriptase-polymerase chain reaction assays. We conclude that the cellular subset of CD105(+)-MSCs has chondrogenic capacity. The study also show the similar chondrogenic capacity of CD105(+)-MSCs cultured from normal and OA synovial membranes.

Isolation of human mesenchymal stromal cells is more efficient by red blood cell lysis

BACKGROUND

Human mesenchymal stromal cells (MSC) have raised high hopes for tissue engineering and clinical therapy. Their isolation usually involves density fractionation of mononuclear cells (MNC) but this is difficult to standardize, especially under good manufacturing practice (GMP) conditions. MSC represent a heterogeneous mixture of cell types and the composition of subpopulations is affected by the initial steps of cell preparation.

METHODS

This study describes a straightforward method for isolation of human MSC based on red blood cell (RBC) lysis with ammonium chloride. Colony formation was compared directly with Ficoll density fractionation and culture of an untreated whole bone marrow (BM) aspirate.

RESULTS

After 7 days the number of fibroblastic colony-forming units (CFU-F) per milliliter of BM aspirate was slightly higher upon RBC lysis and the colonies were significantly larger compared with density fractionation, possibly because of maintenance of platelets. In contrast, colony formation was much lower in untreated BM. The heterogeneous composition of subpopulations was reflected by differences between the initial colonies with regard to growth pattern (tight or disperse) and cell morphology (round or elongated). This heterogeneous composition was not affected by the three different isolation methods. Furthermore, enrichment of CD271(+) cells resulted in the same morphologic heterogeneity. All cell preparations demonstrated the same immunophenotype using a panel of surface markers and displayed adipogenic and osteogenic differentiation potential.

DISCUSSION

This study demonstrates that human MSC can be efficiently isolated by RBC lysis. This technique is faster and can be standardized more easily for clinical application of MSC.

Co-expression of two perivascular cell markers isolates mesenchymal stem-like cells from human endometrium

BACKGROUND

Human endometrium has immense regenerative capacity, growing ~5 mm in 7 days every month. We have previously identified a small population of colony-forming endometrial stromal cells which we hypothesize are mesenchymal stem cells (MSC). The aim of this study was to determine if the co-expression of two perivascular cell markers, CD146 and platelet-derived growth factor-receptor beta (PDGF-Rbeta), will prospectively isolate endometrial stromal cells which exhibit MSC properties, and determine their location in human endometrium.

METHODS

Single cell suspensions of human endometrial stromal cells were fluorescence activated cell sorting (FACS) sorted into CD146(+)PDGF-Rbeta(+) and CD146(-)PDGF-Rbeta(-) populations and analysed for colony-forming ability, in vitro differentiation and expression of typical MSC markers. Full thickness human endometrial sections were co-stained for CD146 and PDGF-Rbeta.

RESULTS

FACS stromal CD146(+)PDGF-Rbeta(+) stromal cells (1.5% of sorted population) were enriched for colony-forming cells compared with CD146(-)PDGF-Rbeta(-) cells (7.7 +/- 1.7 versus 0.7 +/- 0.2% P <0.0001), and also underwent differentiation into adipogenic, osteogenic, myogenic and chondrogenic lineages. They expressed MSC phenotypic surface markers and were located near blood vessels.

CONCLUSION

This study shows that human endometrium contains a small population of MSC-like cells that may be responsible for its cyclical growth, and may provide a readily available source of MSC for tissue engineering applications.

The role of mesenchymal stem cells in maintenance and repair of bone

The maintenance of stable bone mass during adult life, following rapid skeletal growth during childhood, is the result of a carefully controlled balance between the activities of bone forming (osteoblast) and bone resorbing (osteoclast) cells. Although skeletal turnover continues throughout adult life, the net effect of formation and resorption on bone mass is zero in healthy individuals. Later in life, bone mass begins to fall as resorption outpaces formation, particularly in post-menopausal women, which leads to increased fracture risk. The opposing actions of these two cell types are coupled by molecular interactions between them that are thought to be influenced by the actions of the precursor cells of the osteoblast lineage, mesenchymal stem cells (MSCs). In addition to regulating normal skeletal homeostasis, MSCs also play an important role in fracture repair. Bone fracture or injury initiates a series of cellular and molecular pathways that commence with hematoma formation and an inflammatory cascade that regulates MSCs activity leading to fracture healing and the reestablishment of skeletal integrity. Although tremendous strides have been made in increasing our understanding of bone biology, there is surprisingly little data about the role of MSCs in vivo in the maintenance of skeletal integrity or fracture repair. In recent years, the pivotal importance of anabolic therapies in the setting of osteoporosis in which bone mass is substantially increased above and beyond what is attainable with the bisphosphonate class of drugs has put MSC biology firmly on the scientific agenda. Although the biology of cultured MSCs is reasonably well understood, the biology of MSCs in vivo in both bone turnover and fracture repair remains poorly understood. The recent phenotypic characterization of in vivo MSCs and the ability to prospectively purify such cells will open up new avenues of research into a better understanding of the role of MSCs in bone turnover. The purpose of this article is to review bone and fracture biology from the perspective of recent advances in our understanding of MSCs and to highlight the major deficiencies in our current knowledge.

Optimization of a flow cytometry-based protocol for detection and phenotypic characterization of multipotent mesenchymal stromal cells from human bone marrow

BACKGROUND

To study the biology of rare bone marrow (BM) multipotent mesenchymal stromal cells (MSCs), recognized protocols are needed. Colony-forming unit-fibroblast (CFU-F) assays have historically been used for the enumeration of MSCs. However, the need to isolate and further analyze MSCs requires new strategies based on cell surface markers. The purpose of this work was to verify the phenotype of BM MSCs in vivo and to develop flow cytometry-based methods for their evaluation.

METHODS

Pre-enrichment with D7-FIB-conjugated microbeads, cell sorting for CD45low D7-FIB+ LNGFR+ cells, and CFU-F assay were used to confirm the phenotype of BM MSCs in vivo. Further phenotypic characterization of MSCs was performed using three-color flow cytometry following pre-enrichment or by direct four-color flow cytometry. The sensitivity of direct flow cytometry/rare event analysis for the accurate enumeration of MSCs was validated using 85 samples from patients with neoplastic BM diseases.

RESULTS

In normal BM, a significant correlation was found between the frequencies of CFU-Fs and CD45low D7-FIB+ LNGFR+ cells (n = 19, R = 0.719, P = 0.001). Following cell sorting, 15% of these cells were clonogenic. The same cells were enriched using LNGFR-based positive selection, CD45/Glycophorin A-based depletion, or plastic adherence. CD45low D7-FIB+ LNGFR+ cells expressed classic makers of cultured MSCs CD73/SH3 and CD105/SH2 and markers of stromal reticular cells CD106/VCAM and alkaline phosphatase. Novel markers were identified including leukemia inhibitory factor receptor and gp130. CD45low D7-FIB+ LNGFR+ cells were increased fourfold in the floating fat fraction of normal BM aspirates. Their frequency was decreased in chronic lymphocytic leukemia (threefold, n = 13, P = 0.049) and chronic myelogenous leukemia (ninefold, n = 11, P = 0.001) compared with that in age-matched controls (n = 26 and n = 31, respectively).

CONCLUSIONS

This study demonstrates the usefulness of flow cytometry-based methods for the detection, enumeration and further phenotypic analysis of BM MSCs. These findings have broad applications for the future evaluation of BM MSCs in health and disease.

Human mesenchymal stem cells (hMSCs) expressing truncated soluble vascular endothelial growth factor receptor (tsFlk-1) following lentiviral-mediated gene transfer inhibit growth of Burkitt's lymphoma in a murine model

BACKGROUND

Efficient gene transfer to bone marrow derived mesenchymal stem cells (MSC) would provide an important opportunity to express potent anticancer agents in the tumour microenvironment because of their contribution to the tumour stroma.

METHODS

HIV-based lentiviral vectors were pseudotyped with four different envelope proteins; amphotropic murine leukaemia virus (ampho), murine leukaemia virus (10A1), feline endogenous virus (RD114), and the vesicular stomatitis virus glycoprotein (VSVG). These pseudotypes were examined for transduction efficiency in human bone marrow derived MSC. The effect of lentiviral expression of truncated soluble vascular endothelial growth factor decoy receptor (tsFlk-1) in MSC on growth of Raji cells was determined, both in vitro and in vivo.

RESULTS

All lentiviral vectors produced significant levels of transduction at an multiplicity of infection (MOI) of 1, those bearing the RD114 envelope glycoprotein consistently produced higher transduction levels (mean 70 +/- 6%) compared with the other pseudotyped lentiviral vectors, although there was significant inter-donor variation. Stable transgene expression was achieved after multiple rounds of transduction with VSVG-pseudotyped particles, without alteration in the differentiative capacity of transduced cells. Co-injection of MSC stably expressing tsFlk-1 with Raji Burkitt's lymphoma cells significantly impaired subcutaneous tumour growth in immunodeficient mice when compared to controls where either unmanipulated MSC or GFP-expressing MSC were used.

CONCLUSIONS

Human MSC are easily transduced by pseudotyped lentiviral particles but there is inter-donor variation in transduction efficiency. Gene-modified MSC expressing a gene of therapeutic potential can moderate growth of haematological malignancies.

Mesenchymal stem cells participating in ex vivo endothelium repair and its effect on vascular smooth muscle cells growth

BACKGROUND

Previous studies have shown that mesenchymal stem cells (MSCs) transplantation can promote neovascularization and regenerate damaged myocardium. However, it remains unknown whether MSCs seeding can be used to repair injured cellular components in vascular diseases. In this study we explored the feasibility of applying MSCs to endothelium repair in endothelial damage and vasoproliferative disorders.

METHODS

Ex vivo model of endothelium repair was developed in which rabbit vascular smooth muscle cells (SMCs) were inoculated into the upper chamber and rabbit endothelial cells (ECs)/human MSCs into the lower chamber of a co-culture system. 3H-TdR incorporation and PCNA protein expression were assayed and migrated number of SMCs was calculated to evaluate the effect of MSCs seeding on SMCs growth. Flk-1 and vWF protein expressions were observed to analyze the plasticity of the seeded MSCs along endothelial lineage.

RESULTS

In this co-culture system, no vWF protein but Flk-1 protein was observed in the 25.71% of MSCs after having been co-cultured with mature rabbit ECs for 5 days. Compared with the control group, the proliferation and migration of SMCs was significantly increased by proliferative ECs but decreased by confluent ECs (n=6, P<0.01). MSCs seeding decreased the proliferation and migration of SMCs compatible with the effect of proliferative ECs (n=6, P<0.001). However, no inhibition on SMCs growth was observed with MSCs seeding in comparison to the effect of confluent ECs.

CONCLUSIONS

MSCs seeding can inhibit the proliferation and migration of SMCs. MSCs co-cultured with mature ECs have the ability to undergo milieu-dependent differentiation toward ECs.