Human bone marrow native mesenchymal stem cells

Clinical Radiobiology for Radiation Oncology

This chapter is focused on radiobiological aspects at the molecular, cellular, and tissue level which are relevant for the clinical use of ionizing radiation (IR) in cancer therapy. For radiation oncology, it is critical to find a balance, i.e., the therapeutic window, between the probability of tumor control and the probability of side effects caused by radiation injury to the healthy tissues and organs. An overview is given about modern precision radiotherapy (RT) techniques, which allow optimal sparing of healthy tissues. Biological factors determining the width of the therapeutic window are explained. The role of the six typical radiobiological phenomena determining the response of both malignant and normal tissues in the clinic, the 6R’s, which are Reoxygenation, Redistribution, Repopulation, Repair, Radiosensitivity, and Reactivation of the immune system, is discussed. Information is provided on tumor characteristics, for example, tumor type, growth kinetics, hypoxia, aberrant molecular signaling pathways, cancer stem cells and their impact on the response to RT. The role of the tumor microenvironment and microbiota is described and the effects of radiation on the immune system including the abscopal effect phenomenon are outlined. A summary is given on tumor diagnosis, response prediction via biomarkers, genetics, and radiomics, and ways to selectively enhance the RT response in tumors. Furthermore, we describe acute and late normal tissue reactions following exposure to radiation: cellular aspects, tissue kinetics, latency periods, permanent or transient injury, and histopathology. Details are also given on the differential effect on tumor and late responding healthy tissues following fractionated and low dose rate irradiation as well as the effect of whole-body exposure.

Cyclosporin A inhibits adipogenic differentiation and regulates immunomodulatory functions of murine mesenchymal stem cells

Aplastic anemia (AA) is generally considered as an immune-mediated bone marrow failure syndrome. Several studies show that bone marrow mesenchymal stem cells (BM-MSCs), as key cellular components of the bone marrow microenvironment, are also involved in the pathogenic mechanism of AA. Cyclosporin A (CsA) is a classic immunosuppressive drug for AA, and it specifically inhibits mammalian T cells by preventing activation of transcription factors involved in cytokine gene expression. However, little is known about the effect of CsA on the BM-MSCs. In this study, murine BM-MSCs were stimulated in the presence of CsA. Further, we found that CsA could inhibit murine BM-MSC proliferation and promote BM-MSC apoptosis, what's more CsA could inhibit adipogenic differentiation. Our study also showed that CsA could inhibit interleukin-6 expression in BM-MSCs, while promoting programmed death-ligand 2 expression. In conclusion, our results proposed that CsA may exert an effect on regulating the bone marrow environment by influencing BM-MSCs, which have a beneficial effect on treating AA.

Screening and Identification of Highly Specific MAbs for Discovering Novel Biomarkers of Bone Marrow Stromal Cells

Bone marrow stromal cells (BMSCs) are very useful model systems for a better understanding of cell behavior and differential gene expression. Up to now, there have not been specific markers and MAbs for BMSCs that hamper the identification and isolation of BMSCs populations. In this study, chicken BMSCs were isolated from 1-day-old Beijing fatty chickens by adherent culture. After biological characteristics were detected, the chicken BMSCs were used to immunize BALB/c mice to prepare BMSCs-specific monoclonal antibodies (MAbs) by the routine hybridoma technique. These MAbs were characterized by FACS analysis, immunocytochemistry, immunohistochemistry, subtype identification, and Western blotting assay and were used to explore markers of chicken BMSCs. Our data showed that BMSCs expressing antigens CD29, CD44, and CD105, but not expressing antigens CD34, CD45, and CD11b, could be isolated from postnatal chicken bone marrow and hold great potential for multiline age differentiation. Meanwhile, we obtained two hybridoma cell lines secreting chicken BMSCs-specific MAbs (named CHK1 and CHK2), which specifically recognized the surface antigens expressed on chicken BMSCs. According to our subtype identification, heavy chains of CHK1 and CHK2 were typed as IgG1 and IgG2b, respectively; all the light strands were kappa subtype. MAbs CHK1 and CHK2 can be used to develop the detection assay and to discover novel biomarkers of chicken BMSCs.

Serum-free media formulations are cell line-specific and require optimization for microcarrier culture

BACKGROUND AIMS

Mesenchymal stromal cells (MSCs) are being investigated as potential cell therapies for many different indications. Current methods of production rely on traditional monolayer culture on tissue-culture plastic, usually with the use of serum-supplemented growth media. However, the monolayer culturing system has scale-up limitations and may not meet the projected hundreds of billions to trillions batches of cells needed for therapy. Furthermore, serum-free medium offers several advantages over serum-supplemented medium, which may have supply and contaminant issues, leading to many serum-free medium formulations being developed.

METHODS

We cultured seven MSC lines in six different serum-free media and compared their growth between monolayer and microcarrier culture.

RESULTS

We show that (i) expansion levels of MSCs in serum-free monolayer cultures may not correlate with expansion in serum-containing media; (ii) optimal culture conditions (serum-free media for monolayer or microcarrier culture) differ for each cell line; (iii) growth in static microcarrier culture does not correlate with growth in stirred spinner culture; (iv) and that early cell attachment and spreading onto microcarriers does not necessarily predict efficiency of cell expansion in agitated microcarrier culture.

CONCLUSIONS

Current serum-free media developed for monolayer cultures of MSCs may not support MSC proliferation in microcarrier cultures. Further optimization in medium composition will be required for microcarrier suspension culture for each cell line.

Mesenchymal stem cell therapy for the treatment of amyotrophic lateral sclerosis: signals for hope?

Based on the distinctive cellular, molecular and immunomodulatory traits of mesenchymal stem cells (MSC), it has been postulated that these cells may play a critical role in regenerative medicine. In addition to the participation of MSC in the repair of mesodermal-derived tissues (bone, cartilage), robust data have suggested that MSC may also play a reparative role in conditions involving damage of cells of ectodermal origin. The above content has been supported by the capability of MSC to differentiate into neuron-like cells as well as by a competence to generate a ‘neuroprotective’ environment. In turn, several preclinical studies have put forward the concept that MSC therapy may represent an option for the treatment of several neurological disorders and injuries, including amyotrophic lateral sclerosis. We expect that the above foundations, which have inspired this review, may result in the founding of an effective and/or palliative therapy for amyotrophic lateral sclerosis.

Mesenchymal stem cells in immune-mediated bone marrow failure syndromes

Immune-mediated bone marrow failure syndromes (BMFS) are characterized by ineffective marrow haemopoiesis and subsequent peripheral cytopenias. Ineffective haemopoiesis is the result of a complex marrow deregulation including genetic, epigenetic, and immune-mediated alterations in haemopoietic stem/progenitor cells, as well as abnormal haemopoietic-to-stromal cell interactions, with abnormal release of haemopoietic growth factors, chemokines, and inhibitors. Mesenchymal stem/stromal cells (MSCs) and their progeny (i.e., osteoblasts, adipocytes, and reticular cells) are considered as key cellular components of the bone marrow haemopoietic niche. MSCs may interfere with haemopoietic as well as immune regulation. Evidence suggests that bone marrow MSCs may be involved in immune-mediated BMFS underlying pathophysiology, harboring either native abnormalities and/or secondary defects, caused by exposure to activated marrow components. This review summarizes previous as well as more recent information related to the biologic/functional characteristics of bone marrow MSCs in myelodysplastic syndromes, acquired aplastic anemia, and chronic idiopathic neutropenia.

Bone marrow mesenchymal stem cells stimulated by bFGF up-regulated protein expression in comparison with periodontal fibroblasts in vitro

OBJECTIVE

The aim of this study was to evaluate, in vitro, the role of bFGF in the proliferation and expression of collagen type I and fibronectin of dog bone marrow mesenchymal stem cells (dBMMSCs) in comparison with the expression of the same proteins in dog periodontal fibroblasts (dPLFs).

DESIGN

dBMMSCs from the iliac crest were cultivated in Dulbecco's Modified Eagle's Medium (DMEM). Flow cytometry analysis (FCA) was used to characterize dBMMSC. Cells were stimulated with bFGF (1, 5 and 10 ng/mL) after 24 and 48 h. Real time RT-PCR was performed to verify collagen type I and fibronectin expressions. MTT assay was used to confirm cellular proliferation. Statistical analyses were performed (ANOVA and Kruskal-Wallis tests; p<0.05).

RESULTS

FCA showed 55.98% of CD34+ and 32.67% of CD90+ after bone marrow aspiration; 3.33% of CD34+ and 33.0% of CD90+ before P1. After P2, 10.54% of dBMMSCs expressed CD90, whereas after P3, this number decreased to 1.58%. dPLFs presented 4.04% of CD90+ and 1.05% of CD34+ after P3. MTT evaluation showed increase in dBMSC proliferation with 5 ng/mL bFGF-stimulus after 24-h. Both collagen I and fibronectin expression were very similar between the two cells groups after 24-h stimulation with 1 ng/mL bFGF concentration. Fibronectin and collagen I expressions were higher after 24-h stimulation with 5 ng/mL bFGF.

CONCLUSION

dBMMSCs (1 ng/mL-bFGF stimulus after 24 h) are very similar to dPLFs as regards morphological and immunostaining characteristics, and collagen and/or fibronectin production. The dBMMSCs presented the highest protein expression rates with 5 ng/mL-bFGF stimulus after 24-h.

Mesenchymal stem cells and the treatment of conditions and diseases: the less glittering side of a conspicuous stem cell for basic research

Not too long ago, several motivated and forward-looking articles were published describing the cellular and molecular properties of mesenchymal stem cells (MSCs), specially highlighting their potential for self-renewal, commitment, differentiation, and maturation into specific mesoderm-derived lineages. A very influential publication of that period entitled "Mesenchymal stem cells: No longer second class marrow citizens" [1] raised the point of view that "…challenges to harness MSC cell therapy to treat diseases … need to wait for the full comprehension that marrow is a rich source of mesenchyme-derived cells whose potential is still far from fully appreciated." Whether or not the prophecy of Gerson was fulfilled, in the last 8 years it has become evident that infusing MSCs into patients suffering a variety of disorders represents a viable option for medical treatment. Accordingly, a vast number of articles have explored the privileged cellular and molecular features of MSCs prepared from sources other than the canonical, represented by the bone marrow. This review will provide more information neither related to the biological attractiveness of MSCs nor to the success after their clinical use. Rather, we would like to underscore several "critical and tangential" issues, not always discussed in biomedical publications, but relevant to the clinical utilization of bone-marrow-derived MSCs.

Same or not the same? Comparison of adipose tissue-derived versus bone marrow-derived mesenchymal stem and stromal cells

Mesenchymal stem/stromal cells (MSCs) comprise a heterogeneous population of cells with multilineage differentiation potential, the ability to modulate oxidative stress, and secrete various cytokines and growth factors that can have immunomodulatory, angiogenic, anti-inflammatory and anti-apoptotic effects. Recent data indicate that these paracrine factors may play a key role in MSC-mediated effects in modulating various acute and chronic pathological conditions. MSCs are found in virtually all organs of the body. Bone marrow-derived MSCs (BM-MSCs) were discovered first, and the bone marrow was considered the main source of MSCs for clinical application. Subsequently, MSCs have been isolated from various other sources with the adipose tissue, serving as one of the alternatives to bone marrow. Adipose tissue-derived MSCs (ASCs) can be more easily isolated; this approach is safer, and also, considerably larger amounts of ASCs can be obtained compared with the bone marrow. ASCs and BM-MSCs share many biological characteristics; however, there are some differences in their immunophenotype, differentiation potential, transcriptome, proteome, and immunomodulatory activity. Some of these differences may represent specific features of BM-MSCs and ASCs, while others are suggestive of the inherent heterogeneity of both BM-MSC and ASC populations. Still other differences may simply be related to different isolation and culture protocols. Most importantly, despite the minor differences between these MSC populations, ASCs seem to be as effective as BM-MSCs in clinical application, and, in some cases, may be better suited than BM-MSCs. In this review, we will examine in detail the ontology, biology, preclinical, and clinical application of BM-MSCs versus ASCs.

5-Aza-2'-deoxycytidine increases the sensitivity of human bone marrow mesenchymal stem cells to chemotherapeutic agents by demethylation of p73

Many reports have demonstrated that human bone marrow mesenchymal stem cells (BMMSCs) are resistant to several chemotherapeutic agents or ionic radiation when compared with sensitive tumor cell lines; however, the underlying molecular mechanism is rarely known. In our previous studies, we found that p53 family member p73 was not expressed in BMMSCs with or without the treatment of chemotherapeutic drugs, and the exogenous induction of p73 protein could reduce the resistance of BMMSCs to the drugs. In order to elucidate which factor leads to the inhibition of p73 expression, we used a methylation-specific polymerase chain reaction to investigate the epigenetic methylation status of the p73 gene promoter CpG region. Our data showed that the p73 gene promoter was hypermethylated in BMMSCs but not in tumor cell lines, which were sensitive toward chemotherapeutic agents. Using the demethylation agent 5-aza-2'-deoxycytidine significantly reactivated p73 expression both at the transcriptional and at the protein level. In addition, the treatment of 5-aza-2'-deoxycytidine rendered BMMSCs more sensitive to chemotherapeutic agents through the process of enhanced apoptosis cell death. Taken together, our results suggest that the silencing of the p73 gene mediated by promoter hypermethylation may play a crucial role in leading to the high resistance of BMMSCs to chemotherapeutic drugs and thus we conclude that the p73 gene may be an important element regulating human BMMSCs in response to DNA damage.

Bone marrow mesenchymal stem cells in myelodysplastic syndromes: cytogenetic characterization

AIM

This study compared genetic aberrations in hematopoietic cells (HCs) and mesenchymal stem cells of myelodysplastic syndrome (MDS-MSCs) patients.

METHODS

We obtained chromosomes with aberrations from 22 patients with MDS and chromosomes from 7 healthy individuals. Chromosomal aberrations in both HCs and MSCs were identified using G-banding. We then performed DNA content analysis of the HCs and MSCs.

RESULTS

Cytogenetic aberrations were detected in HCs from 13 of the 22 MDS patients (59%). Chromosomal aberrations in MSCs were detected in 15 of the 22 MDS patients (68%). No chromosomal abnormalities were identified in MSCs of the 7 healthy volunteers. We demonstrate herein that MSCs have distinct genetic abnormalities compared to HCs from the same individual. We observed a random loss of chromosomal material in significant proportions of MSCs. A high proportion of random loss may be a marker of chromosomal instability of MDS-MSCs. However, two case results showed that HCs and MSCs have different altered structural changes.

CONCLUSION

Our results suggest enhanced genetic susceptibility of these cells in MDS patients. Our data indicates that the genetic alterations in MSCs may constitute a particular biological mechanism of MDS pathogenesis.

Bone marrow mesenchymal stem cells: biological properties and their role in hematopoiesis and hematopoietic stem cell transplantation

Mesenchymal stem cells (MSCs) are multipotent adult stem cells that are present in practically all tissues as a specialized population of mural cells/pericytes that lie on the abluminal side of blood vessels. Originally identified within the bone marrow (BM) stroma, not only do they provide microenvironmental support for hematopoietic stem cells (HSCs), but can also differentiate into various mesodermal lineages. MSCs can easily be isolated from the BM and subsequently expand in vitro and in addition they exhibit intriguing immunomodulatory properties, thereby emerging as attractive candidates for various therapeutic applications. This review addresses the concept of BM MSCs via a hematologist's point of view. In this context it discusses the stem cell properties that have been attributed to BM MSCs, as compared to those of the prototypic hematopoietic stem cell model and then gives a brief overview of the in vitro and vivo features of the former, emphasizing on their immunoregulatory properties and their hematopoiesis-supporting role. In addition, the qualitative and quantitative characteristics of BM MSCs within the context of a defective microenvironment, such as the one characterizing Myelodysplastic Syndromes are described and the potential involvement of these cells in the pathophysiology of the disease is discussed. Finally, emerging clinical applications of BM MSCs in the field of hematopoietic stem cell transplantation are reviewed and potential hazards from MSC use are outlined.

Human adipose-derived stem cells impair natural killer cell function and exhibit low susceptibility to natural killer-mediated lysis

Human adipose-derived stem cells (hASCs) have been successfully used in treating numerous diseases. However, several aspects need to be considered, particularly in the context of allogeneic cell therapy. To better understand hASCs-host interactions, we studied the phenotype of hASCs and their modulatory effect on natural killer (NK) cells by using bone marrow-mesenchymal stem cells (hBM-MSCs) as a reference. The hASCs displayed a lower susceptibility to NK cell-mediated lysis and a lower expression of ligands for DNAM-1 when compared with hBM-MSCs. Moreover, here we demonstrated that hASCs and hBM-MSCs can modulate NK cells through the action of soluble factors such as indoleamine 2,3-dioxygenase. Altogether, these results suggest that for an adoptive cell therapy based on the transfer of allogeneic hASCs, the NK-hASCs crosstalk will not result in an immediate recognition of the transferred cells. Thus, hASCs may remain in the tissue long enough to balance the immune response before being cleared.

Comparison of Gene Expression in Human Embryonic Stem Cells, hESC-Derived Mesenchymal Stem Cells and Human Mesenchymal Stem Cells

We present a strategy to identify developmental/differentiation and plasma membrane marker genes of the most primitive human Mesenchymal Stem Cells (hMSCs). Using sensitive and quantitative TaqMan Low Density Arrays (TLDA) methodology, we compared the expression of 381 genes in human Embryonic Stem Cells (hESCs), hESC-derived MSCs (hES-MSCs), and hMSCs. Analysis of differentiation genes indicated that hES-MSCs express the sarcomeric muscle lineage in addition to the classical mesenchymal lineages, suggesting they are more primitive than hMSCs. Transcript analysis of membrane antigens suggests that IL1R1^low, BMPR1B^low, FLT4^low, LRRC32^low, and CD34 may be good candidates for the detection and isolation of the most primitive hMSCs. The expression in hMSCs of cytokine genes, such as IL6, IL8, or FLT3LG, without expression of the corresponding receptor, suggests a role for these cytokines in the paracrine control of stem cell niches. Our database may be shared with other laboratories in order to explore the considerable clinical potential of hES-MSCs, which appear to represent an intermediate developmental stage between hESCs and hMSCs.

Development of novel monoclonal antibodies that define differentiation stages of human stromal (mesenchymal) stem cells

Human mesenchymal stem cells (hMSC) are currently being introduced for cell therapy, yet, antibodies specific for native and differentiated MSCs are required for their identification prior to clinical use. Herein, high quality antibodies against MSC surface proteins were developed by immunizing mice with hMSC, and by using a panel of subsequent screening methods. Flow cytometry analysis revealed that 83.5, 1.1, and 8.5% of primary cultures of hMSC were double positive for STRO-1 and either of DJ 3, 9, and 18, respectively. However, none of the three DJ antibodies allowed enrichment of clonogenic hMSC from BMMNCs as single reagents. Using mass-spectrometric analysis, we identified the antigen recognised by DJ3 as CD44, whereas DJ9 and DJ18 recognized HLA-DRB1 and Collagen VI, respectively. The identified proteins were highly expressed throughout in vitro osteogenic- and adipogenic differentiation. Interestingly, undifferentiated cells revealed a sole cytoplasmic distribution pattern of Collagen VI, which however changed to an extracellular matrix appearance upon osteogenic- and adipogenic differentiation. In relation to this, we found that STRO-1(+/-)/Collagen VI(-) sorted hMSC contained fewer differentiated alkaline phosphatase(+) cells compared to STRO-1(+/-)/Collagen VI(+) hMSC, suggesting that Collagen VI on the cell membrane exclusively defines differentiated MSCs. In conclusion, we have generated a panel of high quality antibodies to be used for characterization of MSCs, and in addition our results may suggest that the DJ18 generated antibody against Collagen VI can be used for negative selection of cultured undifferentiated MSCs.

Distinct roles of Bcl-2 and Bcl-Xl in the apoptosis of human bone marrow mesenchymal stem cells during differentiation

Background

Adult mesenchymal stem cells (MSCs) can be maintained over extended periods of time before activation and differentiation. Little is known about the programs that sustain the survival of these cells.

Principal Findings

Undifferentiated adult human MSCs (hMSCs) did not undergo apoptosis in response to different cell death inducers. Conversely, the same inducers can readily induce apoptosis when hMSCs are engaged in the early stages of differentiation. The survival of undifferentiated cells is linked to the expression of Bcl-Xl and Bcl-2 in completely opposite ways. Bcl-Xl is expressed at similar levels in undifferentiated and differentiated hMSCs while Bcl-2 is expressed only in differentiated cells. In undifferentiated hMSCs, the down-regulation of Bcl-Xl is associated with an increased sensitivity to apoptosis while the ectopic expression of Bcl-2 induced apoptosis. This apoptosis is linked to the presence of cytoplasmic Nur 77 in undifferentiated hMSCs.

Significance

In hMSCs, the expression of Bcl-2 depends on cellular differentiation and can be either pro- or anti-apoptotic. Bcl-Xl, on the other hand, exhibits an anti-apoptotic activity under all conditions.

Mesenchymal stem cells contribute to the abnormal bone marrow microenvironment in patients with chronic idiopathic neutropenia by overproduction of transforming growth factor-β1

Chronic idiopathic neutropenia (CIN) is a granulopoiesis disorder associated with an inhibitory bone marrow (BM) microenvironment consisting of activated T-lymphocytes and pro-inflammatory mediators. In this study, we investigated the possible involvement of BM mesenchymal stem cells (MSCs) in the pathophysiology of CIN by assessing the frequency and function of BM MSCs in terms of the proliferative/clonogenic characteristics, the differentiation capacity, the potential to produce pro-inflammatory cytokines, and the ability to suppress T-cell proliferation. The frequency, differentiation capacity toward adipocytes, chondrocytes, or osteoblasts, and immunosuppressive potential to inhibit mitogen-induced T-cell proliferation did not differ significantly between patient (n = 14) and normal (n = 21) MSCs. Tumor necrosis factor-α, interleukin-1β, and interleukin-6 levels in MSC supernatants did not differ significantly between patients and controls; however, transforming growth factor (TGF)-β1 levels were significantly elevated in patients, particularly in those displaying the -509C/T TGF-β1 polymorphism. Patient MSCs displayed defective proliferative/clonogenic potential, which could not be attributed to altered cellular survival characteristics or to increased TGF-β1 production as TGF-β1 neutralization did not restore the impaired colony formation by patient MSCs. We conclude that although BM MSCs do not exert a significant role in the immune deregulation associated with CIN, they contribute to the inhibitory microenvironment by overproducing TGF-β1, at least in patients displaying the -509C/T polymorphism.

Purinergic stimulation of human mesenchymal stem cells potentiates their chemotactic response to CXCL12 and increases the homing capacity and production of proinflammatory cytokines

OBJECTIVE

Extracellular adenosine triphosphate (ATP) is a well-recognized mediator of cell-to-cell communication. Here we show ATP effects on bone marrow (BM)-derived human mesenchymal stem cell (hMSCs) functions.

MATERIALS AND METHODS

ATP-induced modification of hMSCs gene expression profile was assessed by Affymetrix technology. Clonogenic and migration assays in vitro, as well as xenotransplant experiments in vivo, were performed to evaluate the effects of ATP on hMSCs proliferation and BM homing. Enzyme-linked immunosorbent assays were used to assess hMSCs cytokines production, whereas T-cell cultures demonstrated the immunoregulatory activity of ATP-treated hMSCs.

RESULTS

hMSCs were resistant to the cytotoxic effects of ATP, as demonstrated by the lack of morphological and mitochondrial changes or release of intracellular markers of cell death. Gene expression profiling revealed that ATP-stimulated hMSCs underwent a downregulation of genes involved in cell proliferation, whereas those involved in cell migration were strongly upregulated. The inhibitory activity of ATP on hMSCs proliferation was confirmed by assessing clonogenic stromal progenitors. ATP potentiated the chemotactic response of hMSCs to the chemokine CXCL12, and increased their spontaneous migration. In vivo, the homing capacity of hMSCs to the BM of immunodeficient mice was significantly increased by pretreatment with ATP. Moreover, ATP increased the production of the proinflammatory cytokines interleukin-2, interferon-γ, and interleukin-12p70, while decreasing the anti-inflammatory cytokine interleukin-10, and this finding was associated with the reduced ability of MSCs to inhibit T-cell proliferation.

CONCLUSIONS

Our data show that purinergic signaling modulates hMSCs functions and highlights a role for extracellular nucleotides in hMSCs biology.

Periodontal tissue engineering after tooth replantation

BACKGROUND

Blood-derived products, platelet-poor plasma (PPP) and platelet-rich plasma (PRP), constitute an approach in the enhancement of tissue healing. PRP has also been used as a scaffold for bone marrow stem cells in tissue engineering. This study evaluates the effect of PPP, calcium chloride-activated PRP (PRP/Ca), calcium chloride- and thrombin-activated PRP (PRP/Thr/Ca), and bone marrow mononuclear cells and PRP/Ca (BMMCs/PRP/Ca) on the healing of replanted dog teeth.

METHODS

After 30 minutes of extraction, teeth were replanted with 1) no material (control); 2) PPP; 3) PRP/Ca; 4) PRP/Thr/Ca; or 5) BMMCs/PRP/Ca. Histologic, histomorphometric, and immunohistochemical analysis was assessed 120 days after replantation. Data from histomorphometric analysis were analyzed statistically (analysis of variance, Tukey; P <0.05). Quantitative immunohistochemical analysis was analyzed by Kruskal-Wallis and Dunn post hoc test (P <0.05).

RESULTS

Flow cytometry analysis showed 55.98% of CD34(+) and 32.67% of CD90/Thy-1 for BMMCs sample. BMMCs/PRP/Ca presented the largest areas of replacement resorption characterized by osseous ingrowth into cementum (P <0.05), with intense immunomarcation for tartrate-resistant acid phosphatase. The PRP/Ca group also showed areas of replacement resorption with significant immunomarcation for osteopontin. PRP/Thr/Ca presented no replacement resorption. PPP showed areas of inflammatory resorption, with immunomarcation for tartrate-resistant acid phosphatase.

CONCLUSIONS

The results suggest that platelets activated with thrombin play an important role in the healing of tissues after tooth replantation. Additional studies are necessary to test other materials, because PRP/Ca did not present an appropriate scaffold for undifferentiated cells in the treatment of avulsed teeth.

Individual fates of mesenchymal stem cells in vitro

Background

In vitro cultivated stem cell populations are in general heterogeneous with respect to their expression of differentiation markers. In hematopoietic progenitor populations, this heterogeneity has been shown to regenerate within days from isolated subpopulations defined by high or low marker expression. This kind of plasticity has been suggested to be a fundamental feature of mesenchymal stem cells (MSCs) as well. Here, we study MSC plasticity on the level of individual cells applying a multi-scale computer model that is based on the concept of noise-driven stem cell differentiation.

Results

By simulation studies, we provide detailed insight into the kinetics of MSC organisation. Monitoring the fates of individual cells in high and low oxygen culture, we calculated the average transition times of individual cells into stem cell and differentiated states. We predict that at low oxygen the heterogeneity of a MSC population with respect to differentiation regenerates from any selected subpopulation in about two days. At high oxygen, regeneration becomes substantially slowed down. Simulation results on the composition of the functional stem cell pool of MSC populations suggest that most of the cells that constitute this pool originate from more differentiated cells.

Conclusions

Individual cell-based models are well-suited to provide quantitative predictions on essential features of the spatio-temporal organisation of MSC in vitro. Our predictions on MSC plasticity and its dependence on the environment motivate a number of in vitro experiments for validation. They may contribute to a better understanding of MSC organisation in vitro, including features of clonal expansion, environmental adaptation and stem cell ageing.

Mesenchymal Stem or Stromal Cells: Toward a Better Understanding of Their Biology?

The adult bone marrow has been generally considered to be composed of hematopoietic tissue and the associated supporting stroma. Within the latter compartment, a subset of cells with multipotent differentiation capacity exists, usually referred to as mesenchymal stem cells. Mesenchymal stem cells can easily be expanded ex vivo and induced to differentiate into several cell types, including osteoblasts, adipocytes and chondrocytes. Up to now, mesenchymal stem cells have gained wide popularity. Despite the rapid growth in this field, irritations remain with respect to the defining characteristics of these cells, including their differentiation potency, self-renewal and in vivo properties. As a consequence, there is a growing tendency to challenge the term mesenchymal stem cell, especially with respect to the stem cell characteristics. Here, we revisit the experimental origins of mesenchymal stem cells, their classical differentiation capacity into mesodermal lineages and their immunophenotype in order to assess their stemness and function. Based on these essentials, it has to be revisited if the designation as a stem cell remains an appropriate term.

Morphological cell typing of osteoid clones derived from human bone marrow

OBJECTIVE

Bone Marrow Stem Cells (BMSC) are a 'reservoir' for bone regeneration. BMSC can be studied in vitro by cloning cells which are improperly named colonyforming units of fibroblasts (CFU-f). Thus we decided to study CFU-f organization and morphology to have (A) a parameter by which to compare normal and pathologic conditions and (B) to potentially select the most osteogenic clones.

METHODS

Two hundred and forty bone samples were collected from 109 patients and primary cultures performed.

RESULTS

After two weeks 9 cell types and 6 well organized types of colonies were detectable. Some have alkaline phosphatase (AP) activity.

CONCLUSION

These data could be relevant to estimate the potential regeneration of bone.