Isolation and Characterization of Multipotential Mesenchymal Stromal Cells from Congenital Pseudoarthrosis of the Tibia: Case Report

Congenital pseudoarthrosis of the tibia (CPT) is an uncommon disease whose etiology and pathogenesis is unknown. Several evidences suggest that decreased osteogenic capacities, impaired local vascularization, and microenvironment alterations may play a role in the pathogenesis of CPT. Additionally, it is not clear if the pathogenesis of this disease is related to the absence of cells with osteogenic capacity of differentiation. In this work, a two‐year‐old patient diagnosed with CPT underwent an orthopedic surgery to promote bone union in a pseudoarthrosis lesion. Tissue from CPT lesion was excised, and histological evaluation and tissue culture were performed. Histologic analysis of the soft CPT lesion showed the presence of highly cellular fibrous tissue, vascularization, and abundant extracellular matrix. Fusiform cells of mesenchymal appearance were observed but osteoblasts, osteoclasts, chondrocytes, and adipose cells were not found. There was no evidence of osteogenesis. CPT tissue cultured as explants showed, after one month of culture, evidence of osteogenesis, chondrogenesis, and adipogenesis. Cells isolated from explants of CPT tissue showed a fibroblast‐like morphology and expressed the mesenchymal stromal cell (MSC) markers: CD105, CD73, and CD90 (CPT‐MSC). Functional analysis showed that CPT‐MSC differentiate, in vitro, into osteogenic, chondrogenic, and adipocytic cells. CPT‐MSC expressed osteocalcin and agrecan. CPT‐MSC produced collagen in the presence of ascorbic acid. MSC from BM of normal individuals were used as control. In summary, our results indicate that CPT tissue contains MSC with osteogenic capacity of differentiation. It is possible that CPT microenvironment may contribute to impair the osteogenic capacity of differentiation of CPT‐MSC. Anat Rec, 298:1804–1814, 2015. © 2015 Wiley Periodicals, Inc.     

Homing Pathways of Mesenchymal Stromal Cells (MSCs) and Their Role in Clinical Applications

Mesenchymal stromal cells (MSCs) have come into focus for an increasing number of cellular therapies. Since most clinical protocols use intravenous application of MSCs, it has become important to understand their trafficking in the bloodstream. Moreover, since relatively little is known where the transplanted MSCs might locate, a better understanding of involved homing mechanisms will likely shed light on how MSCs exert their therapeutic effects. This review focuses on the current knowledge of homing pathways of transplanted MSCs. We describe regulatory signalling molecules and receptors involved. An outlook is given on significance of these findings for the future use of MSCs as a cellular therapeutic.     

Comparison of Mesenchymal Stem Cells Obtained from Different Human Tissues

We studied mesenchymal stem cells from human bone marrow, adipose tissue, skin, placenta, and thymus. Morphological study and cytofluorometrical analysis by the main marker genes (CD10, CD13, CD31, CD44, CD90, CD105) were carried out. Mesemchymal stem cells of the studied tissues during isolation and culturing were morphologically similar and did not differ by the expression of the main marker genes.__________Translated from Kletochnye Tekhnologii v Biologii i Meditsine, No. 2, pp. 89–94, 2005     

Proliferative Potential of Multipotent Mesenchymal Stromal Cells from Human Bone Marrow

We studied the capacity of multipotent mesenchymal stromal cells isolated from human bone marrow (BM) to long-term passaging, cloning, and re-cloning. Initial multipotent mesenchymal stromal cells and cells after gene labeling were studied. Multipotent mesenchymal stromal cells were obtained from donors (13–59 years) and cultured for 7 passages. Third generation lentivector was used for delivery of green fluorescent protein marker gene. The procedure of infection revealed reduced proliferative potential of multipotent mesenchymal stromal cells from elder donors. Hierarchy of precursor cells differing by their proliferative potential was demonstrated in the culture of multipotent mesenchymal stromal cells. Three categories of multipotent mesenchymal stromal cells were identified: mature cells incapable of proliferation (75.7 ± 2.4% population) and cells with low and high proliferative potential (17.6 ± 2.1 and 6.7 ± 0.3%, respectively). The relative content of these cells insignificantly differed from passage to passage. The efficiency of cloning also remains stable, but re-cloning capacity sharply decreased after passage 3 and completely disappeared in multipotent mesenchymal stromal cells after cryopreservation. Thus, cultured multipotent mesenchymal stromal cells represent a heterogeneous and hierarchically organized population and the characteristics of this population depend of the duration of culturing and age of BM donor. This should be taken into account when using multipotent mesenchymal stromal cells in clinical practice.     

Mesenchymal Stromal Cells Protect Endothelial Cells from Cytotoxic T Lymphocyte‐Induced Lysis

The integrity of the vasculature plays an important role in the success of allogeneic organ and haematopoietic stem cell transplantation. Endothelial cells (EC) have previously been shown to be the target of activated cytotoxic T lymphocytes (CTL) resulting in extensive cell lysis. Mesenchymal stromal cells (MSC) are multipotent cells which can be isolated from multiple sites, each demonstrating immunomodulatory capabilities. They are explored herein for their potential to protect EC from CTL‐targeted lysis. CD8⁺ T cells isolated from human PBMC were stimulated with mitotically inactive cells of a human microvascular endothelial cell line (CDC/EU.HMEC‐1, further referred to as HMEC) for 7 days. Target HMEC were cultured in the presence or absence of MSC for 24 h before exposure to activated allogeneic CTL for 4 h. EC were then analysed for cytotoxic lysis by flow cytometry. Culture of HMEC with MSC in the efferent immune phase (24 h before the assay) led to a decrease in HMEC lysis. This lysis was determined to be MHC Class I restricted linked and further analysis suggested that MSC contact is important in abrogation of lysis, as protection is reduced where MSC are separated in transwell experiments. The efficacy of multiple sources of MSC was also confirmed, and the collaborative effect of MSC and the endothelium protective drug defibrotide were determined, with defibrotide enhancing the protection provided by MSC. These results support the use of MSC as an adjuvant cellular therapeutic in transplant medicine, alone or in conjunction with EC protective agents such as defibrotide.     

Characteristics of Mesenchymal Stromal Precursor Cells Labeled with Lentiviral Vector in Long-Term Bone Marrow Culture

Mouse mesenchymal stromal precursor cells were labeled with lentiviral vector in long-term bone marrow culture. We studied the fate of labeled cells in the stromal sublayer of the longterm bone marrow culture and in ectopic hemopoiesis foci formed from the labeled cultures. The incidence of labeled polypotent fibroblast CFU in sublayers of long-term bone marrow culture and in ectopic hemopoiesis foci formed from these sublayers under the renal capsule of syngeneic mice was also analyzed. It was shown that the marker gene was present in about 40% cells of the stromal sublayer and 30% fibroblast CFU and that effective gene transfer did not affect the total production of hemopoietic cells. The size of ectopic hemopoietic foci formed after implantation of labeled sublayers of the long-term bone marrow culture under the renal capsule did not differ from the control. Differentiated cells of the osseous shell in these foci carried the marker gene in 40% cases. Analysis of fibroblast CFU in these foci showed that despite the total concentration of fibroblast CFU was comparable to that in the bone marrow, the concentration of labeled fibroblast CFU was about 6%, which suggests that one more class of precursors probably exists in the hierarchy of stromal cells presumably between mesenchymal stem cells and fibroblast CFU. Our findings demonstrate the capacities of mesenchymal stem cells to self-maintenance and differentiation without loosing the marker gene integrated into the genome.