Characterization of mesenchymal progenitor cells isolated from human bone marrow by negative selection

Chemokine‑like receptor 1‑positive cells are present in the odontoblast layer in tooth tissue in rats and humans

Cluster of differentiation (CD)44 is a marker of dental pulp stem cells and is involved in odontoblast differentiation and calcification. Chemokine-like receptor 1 (CMKLR1), also known as chemerin receptor 23 (ChemR23) is also expressed in odontoblasts and dental pulp stem cells and is involved in inflammation suppression and tooth regeneration. Resolvin E1, a bioactive lipid, is a CMKLR1 ligand that mediates the chemerin-CMKLR1 interaction and suppresses pulpal inflammation. The present study clarified the intracellular and tissue localization of CD44 and CMKLR1 by immunohistochemical staining of normal pulp and pulp with pulpitis from 12-week-old male Wistar rat teeth or human teeth. In addition, the localization of CD44 and CMKLR1 in human dental pulp stem cells was observed by immunofluorescence staining. The present study also examined the involvement of resolvin E1 in inhibiting inflammation and calcification by western blotting. CD44- and CMKLR1-positive cells were confirmed in the odontoblast layer in normal dental pulp of rats and humans. CD44 was mainly localized in the cell membrane and CMKLR1 was mainly found in the cytoplasm of human dental pulp stem cells. CMKLR1 was also confirmed in the odontoblast layer in rats and humans with pulpitis but CD44 was not present. Following treatment of dental pulp stem cells with lipoteichoic acid, which imitates Gram-positive bacterial infection, resolvin E1 did not suppress the expression of cyclooxygenase-2 or of the odontoblast differentiation marker, dentin sialophosphoprotein. Furthermore, resolvin E1 induced the differentiation of dental pulp stem cells into odontoblasts even in the presence of the inflammatory stimulus.

Suppressive function of bone marrow-derived mesenchymal stem cell-derived exosomal microRNA-187 in prostate cancer

Application of bone marrow-derived mesenchymal stem cell-derived exosomes (BMSC-exos) in cancer treatment has been widely studied. Here, we elaborated the function of BMSC-exos containing microRNA-187 (miR-187) in prostate cancer. Differentially expressed miRs and genes were screened with microarray analysis. The relationship between CD276 and miR-187 in prostate cancer was evaluated. Following miR-187 mimic/inhibitor or CD276 overexpression transfection, their actions in prostate cancer cell biological processes were analyzed. Prostate cancer cells were then exposed to BMSC-exos that were treated with either miR-187 mimic/inhibitor or CD276 overexpression for pinpointing the in vitro and in vivo effects of exosomal miR-187. miR-187 was poorly expressed while CD276 was significantly upregulated in prostate cancer. Additionally, restoring miR-187 inhibited the prostate cancer cell malignant properties by targeting CD276. Upregulation of miR-187 led to declines in CD276 expression and the JAK3-STAT3-Slug signaling pathway. Next, BMSC-exos carrying miR-187 contributed to repressed cell malignant features as well as limited tumorigenicity and tumor metastasis. Collectively, this study demonstrated that BMSC-derived exosomal miR-187 restrained prostate cancer by reducing CD276/JAK3-STAT3-Slug axis.

Lithium chloride inhibits the migration and invasion of osteosarcoma cells by blocking nuclear translocation of phospho-Erk

Lithium chloride (LiCl) is an important mood-stabilizing therapeutic agent for bipolar disorders, which has also been shown to inhibit cancer cell metastasis. Investigations of LiCl-induced signaling have focused mainly on extracellular signal regulated kinase 1/2 (ERK1/2) and glycogen synthase kinase 3 (GSK-3). However, little is known about the differences in cellular activities resulting from specific signaling via each of these pathways. In this study, we investigated the difference in responses between the Wnt/β-catenin and ERK pathways by LiCl or epidermal growth factor (EGF) treatment of osteosarcoma cells. In particular, we analyzed the mechanisms responsible for differences in cell mobility and cell proliferation when pERK or β-catenin is activated. In osteosarcoma cells treated with LiCl or EGF, active β-catenin and p-ERK protein levels were significantly increased compared to those in the control group. However, in wound healing and transwell invasion assays, U2OS and SaOS2 cell migration was significantly reduced by LiCl treatment but increased by EGF treatment. In addition, the proliferation of U2OS cells was reduced by LiCl treatment but increased by EGF treatment. Using immunofluorescence microscopy, we observed nuclear accumulation of phosphorylated ERK (pERK) with EGF treatment, but pERK was restricted to the perinuclear area with LiCl treatment. These results were confirmed using immunoblot assays after subcellular fractionation. Together, these data suggest that LiCl interferes with the translocation of pERK from the cytoplasm to the nucleus.

Circulating Progenitor Cells and Cognitive Impairment in Men and Women with Coronary Artery Disease

BACKGROUND

Circulating progenitor cells (CPC) have been associated with memory function and cognitive impairment in healthy adults. However, it is unclear whether such associations also exist in patients with coronary artery disease (CAD).

OBJECTIVE

To assess the association between CPCs and memory performance among individuals with CAD.

METHODS

We assessed cognitive function in 509 patients with CAD using the verbal and visual Memory subtests of the Wechsler memory scale-IV and the Trail Making Test parts A and B. CPCs were enumerated with flow cytometry as CD45med/CD34+ blood mononuclear cells, those co-expressing other epitopes representing populations enriched for hematopoietic and endothelial progenitors.

RESULTS

After adjusting for demographic and cardiovascular risk factors, lower number of endothelial progenitor cell counts were independently associated with lower visual and verbal memory scores (p for all < 0.05). There was a significant interaction in the magnitude of this association with race (p < 0.01), such that the association of verbal memory scores with endothelial progenitor subsets was present in Black but not in non-Black participants. No associations were present with the hematopoietic progenitor-enriched cells or with the Trail Making Tests.

CONCLUSION

Lower numbers of circulating endothelial progenitor cells are associated with cognitive impairment in patients with CAD, suggesting a protective effect of repair/regeneration processes in the maintenance of cognitive status. Impairment of verbal memory function was more strongly associated with lower CPC counts in Black compared to non-Black participants with CAD. Whether strategies designed to improve regenerative capacity will improve cognition needs further study.

The Crossroads between Infection and Bone Loss

Bone homeostasis, based on a tight balance between bone formation and bone degradation, is affected by infection. On one hand, some invading pathogens are capable of directly colonizing the bone, leading to its destruction. On the other hand, immune mediators produced in response to infection may dysregulate the deposition of mineral matrix by osteoblasts and/or the resorption of bone by osteoclasts. Therefore, bone loss pathologies may develop in response to infection, and their detection and treatment are challenging. Possible biomarkers of impaired bone metabolism during chronic infection need to be identified to improve the diagnosis and management of infection-associated osteopenia. Further understanding of the impact of infections on bone metabolism is imperative for the early detection, prevention, and/or reversion of bone loss. Here, we review the mechanisms responsible for bone loss as a direct and/or indirect consequence of infection.

Circulating Progenitor Cells and Racial Differences

RATIONALE

Blacks compared with whites have a greater risk of adverse cardiovascular outcomes. Impaired regenerative capacity, measured as lower levels of circulating progenitor cells (CPCs), is a novel determinant of adverse outcomes; however, little is known about racial differences in CPCs.

OBJECTIVE

To investigate the number of CPCs, PC-mobilizing factors, PC mobilization during acute myocardial infarction and the predictive value of CPC counts in blacks compared with whites.

METHODS AND RESULTS

CPCs were enumerated by flow cytometry as CD45med+ blood mononuclear cells expressing CD34+, CD133+, VEGF2R+, and CXCR4+ epitopes in 1747 subjects, mean age 58.4±13, 55% male, and 26% self-reported black. Patients presenting with acute myocardial infarction (n=91) were analyzed separately. Models were adjusted for relevant clinical variables. SDF-1α (stromal cell-derived factor-1α), VEGF (vascular endothelial growth factor), and MMP-9 (matrix metallopeptidase-9) levels were measured (n=561), and 623 patients were followed for median of 2.2 years for survival analysis. Blacks were younger, more often female, with a higher burden of cardiovascular risk, and lower CPC counts. Blacks had fewer CD34+ cells (-17.6%; [95% confidence interval (CI), -23.5% to -11.3%]; P<0.001), CD34+/CD133+ cells (-15.5%; [95% CI, -22.4% to -8.1%]; P<0.001), CD34+/CXCR4+ cells (-17.3%; [95% CI, -23.9% to -10.2%]; P<0.001), and CD34+/VEGF2R+ cells (-27.9%; [95% CI, -46.9% to -2.0%]; P=0.04) compared with whites. The association between lower CPC counts and black race was not affected by risk factors or cardiovascular disease. Results were validated in a separate cohort of 411 patients. Blacks with acute myocardial infarction had significantly fewer CPCs compared with whites ( P=0.02). Blacks had significantly lower plasma MMP-9 levels ( P<0.001) which attenuated the association between low CD34+ and black race by 19% (95% CI, 13%-33%). However, VEGF and SDF-1α levels were not significantly different between the races. Lower CD34+ counts were similarly predictive of mortality in blacks (hazard ratio, 2.83; [95% CI, 1.12-7.20]; P=0.03) and whites (hazard ratio, 1.79; [95% CI, 1.09-2.94]; P=0.02) without significant interaction.

CONCLUSIONS

Black subjects have lower levels of CPCs compared with whites which is partially dependent on lower circulating MMP-9 levels. Impaired regenerative capacity is predictive of adverse outcomes in blacks and may partly account for their increased risk of cardiovascular events.

Bacterial nanocellulose stimulates mesenchymal stem cell expansion and formation of stable collagen-I networks as a novel biomaterial in tissue engineering

Biomimetic scaffolds are of great interest to tissue engineering (TE) and tissue repair as they support important cell functions. Scaffold coating with soluble collagen-I has been used to achieve better tissue integration in orthopaedy, however, as collagen persistence was only temporary such efforts were limited. Adequate coverage with cell-derived ECM collagen-I would promise great success, in particular for TE of mechanically challenged tissues. Here, we have used label-free, non-invasive multiphoton microscopy (MPM) to characterise bacterial nanocellulose (BNC) - a promising biomaterial for bone TE - and their potency to stimulate collagen-I formation by mesenchymal stem cells (MSCs). BNC fleeces were investigated by Second Harmonic Generation (SHG) imaging and by their characteristic autofluorescence (AF) pattern, here described for the first time. Seeded MSCs adhered fast, tight and very stable, grew to multilayers and formed characteristic, wide-spread and long-lasting collagen-I. MSCs used micron-sized lacunae and cracks on the BNC surface as cell niches. Detailed analysis using a collagen-I specific binding protein revealed a highly ordered collagen network structure at the cell-material interface. In addition, we have evidence that BNC is able to stimulate MSCs towards osteogenic differentiation. These findings offer new options for the development of engineered tissue constructs based on BNC.

Concise Review: Stem Cells in Osteoimmunology

Bone remodeling is a lifelong process in which mature bone tissue is removed from the skeleton by bone resorption and is replenished by new during ossification or bone formation. The remodeling cycle requires both the differentiation and activation of two cell types with opposing functions; the osteoclast, which orchestrates bone resorption, and the osteoblast, which orchestrates bone formation. The differentiation of these cells from their respective precursors is a process which has been overshadowed by enigma, particularly because the precise osteoclast precursor has not been identified and because the identification of skeletal stem cells, which give rise to osteoblasts, is very recent. Latest advances in the area of stem cell biology have enabled us to gain a better understanding of how these differentiation processes occur in physiological and pathological conditions. In this review we postulate that modulation of stem cells during inflammatory conditions is a necessary prerequisite of bone remodeling and therefore an essential new component to the field of osteoimmunology. In this context, we highlight the role of transcription factor nuclear factor of activated T cells cytoplasmic 1 (NFATc1), because it directly links inflammation with differentiation of osteoclasts and osteoblasts. Stem Cells 2017;35:1461-1467.

Comparison of in vitro-cultivation of human mesenchymal stroma/stem cells derived from bone marrow and umbilical cord

Cell-mediated therapy is currently considered as a novel approach for many human diseases. Potential uses range from topic applications with the regeneration of confined tissue areas to systemic applications. Stem cells including mesenchymal stroma/stem cells (MSCs) represent a highly attractive option. Their potential to cure or alleviate human diseases is investigated in a number of clinical trials. A wide variety of methods has been established in the past years for isolation, cultivation and characterization of human MSCs as expansion is presently deemed a prerequisite for clinical application with high numbers of cells carrying reproducible properties. MSCs have been retrieved from various tissues and used in a multitude of settings whereby numerous experimental protocols are available for expansion of MSCs in vitro. Accordingly, different isolation, culture and upscaling techniques contribute to the heterogeneity of MSC characteristics and the, sometimes, controversial results. Therefore, this review discusses and summarizes certain experimental conditions for MSC in vitro culture focusing on adult bone marrow-derived and neonatal umbilical cord-derived MSCs in order to enhance our understanding for MSC tissue sources and to stratify different procedures. Copyright © 2016 John Wiley & Sons, Ltd.

Mesangiogenic Progenitor Cells Derived from One Novel CD64(bright)CD31(bright)CD14(neg) Population in Human Adult Bone Marrow

Mesenchymal stromal cells (MSCs) have been the object of extensive research for decades, due to their intrinsic clinical value. Nonetheless, the unambiguous identification of a unique in vivo MSC progenitor is still lacking, and the hypothesis that these multipotent cells could possibly arise from different in vivo precursors has been gaining consensus in the last years. We identified a novel multipotent cell population in human adult bone marrow that we first named Mesodermal Progenitor Cells (MPCs) for the ability to differentiate toward the mesenchymal lineage, while still retaining angiogenic potential. Despite extensive characterization, MPCs positioning within the differentiation pathway and whether they can be ascribed as possible distinctive progenitor of the MSC lineage is still unclear. In this study, we describe the ex vivo isolation of one novel bone marrow subpopulation (Pop#8) with the ability to generate MPCs. Multicolor flow cytometry in combination with either fluorescence-activated cell sorting or magnetic-activated cell sorting were applied to characterize Pop#8 as CD64(bright)CD31(bright)CD14(neg). We defined Pop#8 properties in culture, including the potential of Pop#8-derived MPCs to differentiate into MSCs. Gene expression data were suggestive of Pop#8 in vivo involvement in hematopoietic stem cell niche constitution/maintenance. Pop#8 resulted over three logs more frequent than other putative MSC progenitors, corroborating the idea that most of the controversies regarding culture-expanded MSCs could be the consequence of different culture conditions that select or promote particular subpopulations of precursors.

Ability of circulating human hematopoietic lineage negative cells to support hematopoiesis

Hematopoietic stem cell (HSC) self-renewal is regulated by osteoblast and/or endothelial cells within the hematopoietic niche. However, the true identity of the supporting cells and the nature of the secreted factors remain uncertain. We developed a novel mouse model and analyzed whether circulating human peripheral hematopoietic lineage negative/AP+ (lin-/AP+) cells support hematopoiesis in vivo. Thus, immunocompromised (Rag) mice expressing thymidine kinase (Tk) under the control of the 3.6Col1α1 promoter (Tk-Rag) were treated with ganciclovir, resulting in osteoblast progenitor cell ablation and subsequent loss of hematopoiesis (evaluated by measuring mouse Ter119+ erythroid cells). Following hematopoietic cell depletion, human bone marrow-derived marrow stromal cells (MSCs) or lin-/AP+ cells were infused into Tk-Rag mice and compared with saline infusions. Ganciclovir significantly reduced (7.4-fold) Ter119+ cells in the bone marrow of Tk-Rag mice compared to saline injections. Infusion of either MSCs or lin-/AP+ cells into ganciclovir-treated mice resulted in a 3.3-fold and 2.7-fold increase (P < 0.01), respectively, in Ter119+ cells compared to mice receiving saline. Relative to lin-/AP- cells, lin-/AP+ cells expressed high levels of mesenchymal, endothelial, and hematopoiesis supporting genes. Thus, human peripheral blood lin-/AP+ cells represent a novel cell type capable of supporting hematopoiesis in a manner comparable to MSCs.

Global transcriptional profiling using RNA sequencing and DNA methylation patterns in highly enriched mesenchymal cells from young versus elderly women

Age-related bone loss in humans is associated with a decrease in bone formation relative to bone resorption, although the mechanisms for this impairment in bone formation with aging are not well understood. It is known that the precursors for the bone-forming osteoblasts reside in the mesenchymal cell population in bone marrow. Thus, in an effort to identify relevant genetic pathways that are altered with aging, we examined the gene expression and DNA methylation patterns from a highly enriched bone marrow mesenchymal cell population from young (mean age, 28.7 years) versus old (mean age, 73.3 years) women. Bone marrow mononuclear cells from these women were depleted of hematopoietic lineage (lin) and endothelial cells using a combination of magnetic- and fluorescence-activated cell sorting, yielding a previously characterized mesenchymal cell population (lin-/CD34-/CD31- cells) that is capable of osteoblast differentiation. Whole transcriptome RNA sequencing (RNAseq) of freshly isolated cells (without in vitro culture) identified 279 differentially expressed genes (p < 0.05, false discovery rate [q]< 0.10) between the young and old subjects. Pathway analysis revealed statistically significant (all p < 0.05) alterations in protein synthesis and degradation pathways, as well as mTOR, gap junction, calcium, melatonin and NFAT signaling pathways. Further, Reduced Representational Bisulphite sequencing (RRBS DNA methylation sequencing) revealed significant differences in methylation between the young and old subjects surrounding the promoters of 1528 target genes that also exhibited significant differences in gene expression by RNAseq. In summary, these studies provide novel insights into potential pathways affected by aging in a highly enriched human mesenchymal cell population analyzed without the confounding effects of in vitro culture. Specifically, our finding of alterations in several genes and pathways leading to impaired protein synthesis and turnover with aging in bone marrow mesenchymal cells points to the need for further studies examining how these changes, as well as the other alterations with aging that we identified, may contribute to the age-related impairment in osteoblast formation and/or function.

Cancer stem cells and mesenchymal stem cells in the hypoxic tumor niche: two different targets for one only drug

Putative cancer stem cells (CSCs) reside in a hypoxic microenvironment where mesenchymal stem cells (MSCs) are also present. In this niche MSCs seem to promote the generation of CSCs and sustain tumor progression. Therefore, it may assume clinical relevance to produce a drug which kills not only CSCs but also MSCs. We hypothesized that bifunctional nanoparticles, loaded with a HIF-1α inhibitor and conjugated with an aptamer targeting a common receptor of CSCs and MSCs, may fulfill this strategy. The nanoparticle should ensure that: (1) the conveyed drug is less susceptible to degradation, (2) the common receptor of CSCs and MSCs is recognized by a superselective aptamer, and (3) receptor-mediated internalization is the main process to enter target cells. Small RNA or DNA aptamers represent an advantage over antibodies because do not cause immune reactions, are better internalized into the target cell, are more resistant to degradation, their cost of production are lower, and the purity of the oligonucleotide ligand is extremely elevated. Concerning the drugs to be delivered, we suggest to employ those exerting an anti-HIF-1α activity because they should be harmful for hypoxic CSCs and MCSs in their tumor niche but provide very limited toxicity, or even none, to well-oxygenated normal cells. Corresponding experimental approaches to perform pre-clinical studies and verify this hypothesis are also addressed.

The use of total human bone marrow fraction in a direct three-dimensional expansion approach for bone tissue engineering applications: focus on angiogenesis and osteogenesis

Current approaches in bone tissue engineering have shown limited success, mostly owing to insufficient vascularization of the construct. A common approach consists of co-culture of endothelial cells and osteoblastic cells. This strategy uses cells from different sources and differentiation states, thus increasing the complexity upstream of a clinical application. The source of reparative cells is paramount for the success of bone tissue engineering applications. In this context, stem cells obtained from human bone marrow hold much promise. Here, we analyzed the potential of human whole bone marrow cells directly expanded in a three-dimensional (3D) polymer matrix and focused on the further characterization of this heterogeneous population and on their ability to promote angiogenesis and osteogenesis, both in vitro and in vivo, in a subcutaneous model. Cellular aggregates were formed within 24 h and over the 12-day culture period expressed endothelial and bone-specific markers and a specific junctional protein. Ectopic implantation of the tissue-engineered constructs revealed osteoid tissue and vessel formation both at the periphery and within the implant. This work sheds light on the potential clinical use of human whole bone marrow for bone regeneration strategies, focusing on a simplified approach to develop a direct 3D culture without two-dimensional isolation or expansion.

Sclerostin: recent advances and clinical implications

PURPOSE OF REVIEW

Discovery of the Wnt signaling pathway and understanding the central role of osteocyte in skeletal homeostasis have been the major advances in skeletal biology over the past decade. Sclerostin, secreted mainly (but not exclusively) by osteocytes, has emerged as a key player in skeletal homeostasis. This review highlights the most relevant recent advances.

RECENT FINDINGS

Sclerostin by inhibiting Wnt signaling pathway decreases bone formation and osteoblast differentiation and promotes osteoblast apoptosis. Ability to measure serum sclerostin levels better clarified the role of sclerostin in various physiologic and pathologic states. Early clinical trials with antibodies to sclerostin have produced robust increases in bone mineral density, and fracture prevention trials are underway.

SUMMARY

Since the discovery of Wnt signaling pathway and sclerostin's association with high bone mass, there has been a remarkable progress. Clinical trials with fracture endpoints, already underway, should expand osteoanabolic therapeutic horizon in the very near future. Measurement of sclerostin levels in a number of conditions has advanced our knowledge about pathophysiology of skeletal and nonskeletal disorders in an altogether new light.

NOTCH-Mediated Maintenance and Expansion of Human Bone Marrow Stromal/Stem Cells: A Technology Designed for Orthopedic Regenerative Medicine

Human bone marrow-derived stromal/stem cells (BMSCs) have great therapeutic potential for treating skeletal disease and facilitating skeletal repair, although maintaining their multipotency and expanding these cells ex vivo have proven difficult. Because most stem cell-based applications to skeletal regeneration and repair in the clinic would require large numbers of functional BMSCs, recent research has focused on methods for the appropriate selection, expansion, and maintenance of BMSC populations during long-term culture. We describe here a novel biological method that entails selection of human BMSCs based on NOTCH2 expression and activation of the NOTCH signaling pathway in cultured BMSCs via a tissue culture plate coated with recombinant human JAGGED1 (JAG1) ligand. We demonstrate that transient JAG1-mediated NOTCH signaling promotes human BMSC maintenance and expansion while increasing their skeletogenic differentiation capacity, both ex vivo and in vivo. This study is the first of its kind to describe a NOTCH-mediated methodology for the maintenance and expansion of human BMSCs and will serve as a platform for future clinical or translational studies aimed at skeletal regeneration and repair.

A critical role of autocrine sonic hedgehog signaling in human CD138+ myeloma cell survival and drug resistance

Hedgehog (Hh) signaling plays an important role in the oncogenesis of B-cell malignancies such as multiple myeloma (MM). However, the source of Hh ligand sonic hedgehog (SHH) and its target cells remains controversial. Previous studies showed that stromally induced Hh signaling is essential for the tumor cells and that CD19(+)CD138(-) MM stem cells are the target cells of Hh signaling. Here we demonstrate that SHH was mainly secreted by human myeloma cells but not by stromal cells in MM bone marrow. Autocrine SHH enhanced CD138(+) myeloma cell proliferation and protected myeloma cells from spontaneous and stress-induced apoptosis. More importantly, autocrine SHH protected myeloma cells against chemotherapy-induced apoptosis in vitro and in vivo. Combinational treatment with chemotherapy and SHH-neutralizing antibody displayed synergistic antimyeloma effects. Mechanistic studies showed that SHH signaling activated the SHH/GLI1/BCL-2 axis, leading to the inhibition of myeloma cell apoptosis. Thus, this study identifies the myeloma autocrine Hh signaling pathway as a potential target for the treatment of MM. Targeting this pathway may improve the efficacy of chemotherapy in MM patients.

Comparison of the efficacy of bone marrow mononuclear cells and bone mesenchymal stem cells in the treatment of osteoarthritis in a sheep model

OBJECTIVE

To evaluate the therapeutic efficacy of uncultured bone marrow mononuclear cells (BMMCs) and bone mesenchymal stem cells in an osteoarthritis (OA) model of sheep.

METHODS

Induction of sheep OA was performed surgically through anterior cruciate ligament transection and medial meniscectomy. After 12 weeks, concentrated BMMCs obtained from autologous bone marrow harvested from anterior iliac crest or a single dose of 10 million autologous bone mesenchymal stem cells (BMSCs) suspended in phosphate-buffered saline (PBS) was delivered to the injured knee via direct intra-articular injection. Animals of the PBS group received vehicle alone. The contra-lateral joints were selected randomly as the control group. Knees of the four groups were compared macroscopically and histologically, and glycosaminoglycan (GAG) contents normalized to cartilage wet weight were measured at lesions of cartilage from medial condyle of the femur head. Gene expression levels of type II collagen (Col2A1), Aggrecan and matrix metalloproteinase-13 (MMP-13) in cartilage were measured based on RT-PCR and prostaglandin E2 (PGE2), Tumor Necrosis Factor-α (TNF-α) and Transforming Growth Factor beta (TGF-β) concentrations in synovial fluid were determined with ELISA assays at 8 weeks after injection.

RESULTS

At 8 weeks post cell transplantation, partial cartilage repair was observed in the cell therapy, but not the PBS group (P<0.05). The BMSCs group showed higher regeneration of cartilage and lower proteoglycan loss than the BMMCs group (P<0.05). Concentrated BMMCs injection led to a weaker treatment effect, but also inhibited PGE2, TNF-α and TGF-β levels in synovial fluid and promoted higher levels of Aggrecan and Col2A1 and downregulation of MMP-13 in sheep chondrocytes in a similar manner to BMSCs, compared with the PBS group.

CONCLUSIONS

Bone marrow cells showed therapeutic efficacy in a sheep model of OA. Despite similar therapeutic potential, the easier and faster process of collection and isolation of BMMCs supports their utility as an effective alternative for OA treatment in the clinic.

Isolation and characterization of human osteoblasts from needle biopsies without in vitro culture

SUMMARY

We isolate and characterize osteoblasts from humans without in vitro culture. These techniques should be broadly applicable to studying the pathogenesis of osteoporosis and other bone disorders.

INTRODUCTION

There is currently no data regarding the expression of specific genes or pathways in human osteoblasts that have not been subjected to extensive in vitro culture. Thus, we developed methods to rapidly isolate progressively enriched osteoblast populations from humans and characterized these cells.

METHODS

Needle bone biopsies of the posterior iliac crest were subjected to sequential collagenase digests. The cells from the second digest were stained with an alkaline phosphatase (AP) antibody, and the AP+ cells were isolated using magnetic cell sorting.

RESULTS

Relative to AP- cells, the AP+ cells contained virtually all of the mineralizing cells and were enriched for key osteoblast marker genes. The AP+ cells were further purified by depletion of cells expressing CD45, CD34, or CD31 (AP+/CD45/34/31- cells), which represented a highly enriched human osteoblast population devoid of hematopoietic/endothelial cells. These cells expressed osteoblast marker genes but very low to undetectable levels of SOST. We next used high-throughput RNA sequencing to compare the transcriptome of the AP+/CD45/34/31- cells to human fibroblasts and identified genes and pathways expressed only in human osteoblasts in vivo, but not in fibroblasts, including 448 genes unique to human osteoblasts.

CONCLUSIONS

We provide a detailed characterization of highly enriched human osteoblast populations without in vitro culture. These techniques should be broadly applicable to studying the pathogenesis of osteoporosis and other bone disorders.

Comparative analysis of mesenchymal stem cell surface marker expression for human dental mesenchymal stem cells

AIM

Human dental mesenchymal stem cells (hDMSCs) have been isolated from extracted human teeth and proven to have different proliferation and differentiation abilities among the subtypes. Despite increasing interest in the clinical use of hDMSCs, a well-defined specific marker has been absent for these stem cells. In this study, a comparative analysis with known mesenchymal stem cell surface markers such as STRO-1, CD90, CD146, CD34 and TfR (CD71) was performed.

MATERIALS & METHODS

Four subtypes of the hDMSCs were obtained and cultured. The hDMSCs were processed by flow cytometric analysis, fluorescence immunocytostaining for in vitro study and in situ immunohistochemical staining for in vivo study.

RESULTS & CONCLUSION

The previously known positive and negative MSC markers, such as STRO-1, CD90, CD146 and CD34 showed comparative expression profiles of hDMSC subtypes. TfR was highly positive in hDMSCs compared with the control cells; therefore, TfR was suggested as a new marker for hDMSCs in this study.

Effects of age on bone mRNA levels of sclerostin and other genes relevant to bone metabolism in humans

Although aging is associated with a decline in bone formation in humans, the molecular pathways contributing to this decline remain unclear. Several previous clinical studies have shown that circulating sclerostin levels increase with age, raising the possibility that increased production of sclerostin by osteocytes leads to the age-related impairment in bone formation. Thus, in the present study, we examined circulating sclerostin levels as well as bone mRNA levels of sclerostin using quantitative polymerase chain reaction (QPCR) analyses in needle bone biopsies from young (mean age, 30.0years) versus old (mean age, 72.9years) women. In addition, we analyzed the expression of genes in a number of pathways known to be altered with skeletal aging, based largely on studies in mice. While serum sclerostin levels were 46% higher (p<0.01) in the old as compared to the young women, bone sclerostin mRNA levels were no different between the two groups (p=0.845). However, genes related to notch signaling were significantly upregulated (p=0.003 when analyzed as a group) in the biopsies from the old women. In an additional analysis of 118 genes including those from genome-wide association studies related to bone density and/or fracture, BMP/TGFβ family genes, selected growth factors and nuclear receptors, and Wnt/Wnt-related genes, we found that mRNA levels of the Wnt inhibitor, SFRP1, were significantly increased (by 1.6-fold, p=0.0004, false discovery rate [q]=0.04) in the biopsies from the old as compared to the young women. Our findings thus indicate that despite increases in circulating sclerostin levels, bone sclerostin mRNA levels do not increase in elderly women. However, aging is associated with alterations in several key pathways and genes in humans that may contribute to the observed impairment in bone formation. These include notch signaling, which represents a potential therapeutic target for increasing bone formation in humans. Our studies further identified mRNA levels of SFRP1 as being increased in aging bone in humans, suggesting that this may also represent a viable target for the development of anabolic therapies for age-related bone loss and osteoporosis.

Effects of estrogen on bone mRNA levels of sclerostin and other genes relevant to bone metabolism in postmenopausal women

CONTEXT

Studies in postmenopausal women have shown that estrogen reduces circulating sclerostin levels, but effects of estrogen on skeletal sclerostin mRNA levels are unknown.

OBJECTIVE

The objective of the study was to evaluate the effects of short-term estrogen treatment on bone mRNA levels of sclerostin and other genes relevant to bone metabolism.

DESIGN, SETTING, AND PATIENTS

Needle bone biopsies were obtained from 20 postmenopausal women treated with transdermal estrogen for 3 weeks and 20 untreated controls. Quantitative PCR analyses were used to examine the expression of sclerostin and other genes related to bone metabolism, including 71 additional genes linked to bone density/fracture from genome-wide association studies.

RESULTS

Estrogen treatment was associated with lower bone sclerostin mRNA levels (by 48%, P<.05) and with lower (by 54%, P<.01) mRNA levels of the sclerostin-related protein, sclerostin domain-containing protein 1 (SOSTDC1), which is also a Wnt/bone morphogenetic protein inhibitor. Consistent with studies in mice showing that ovariectomy increased nuclear factor-κB (NF-κB) activation, we found that estrogen treatment was associated with a significant reduction in inflammatory genes as a group (P=.028), with bone mRNA levels of NFKB2 and RELB (both encoding proteins in the NF-κB transcription factor complex) being significantly reduced individual genes. Eight of the 71 genome-wide association study-related genes examined were modulated by estrogen (P<.05, false discovery rate<0.10).

CONCLUSION

In humans, estrogen-induced decreases in two key inhibitors of Wnt/bone morphogenetic protein signaling, sclerostin and SOSTDC1, along with reductions in NF-κB signaling, may be responsible for at least part of the protective effects of estrogen on bone.

Silencing of RB1 and RB2/P130 during adipogenesis of bone marrow stromal cells results in dysregulated differentiation

Bone marrow adipose tissue (BMAT) is different from fat found elsewhere in the body, and only recently have some of its functions been investigated. BMAT may regulate bone marrow stem cell niche and plays a role in energy storage and thermogenesis. BMAT may be involved also in obesity and osteoporosis onset. Given the paramount functions of BMAT, we decided to better clarify the human bone marrow adipogenesis by analyzing the role of the retinoblastoma gene family, which are key players in cell cycle regulation. Our data provide evidence that the inactivation of RB1 or RB2/P130 in uncommitted bone marrow stromal cells (BMSC) facilitates the first steps of adipogenesis. In cultures with silenced RB1 or RB2/P130, we observed an increase of clones with adipogenic potential and a higher percentage of cells accumulating lipid droplets. Nevertheless, the absence of RB1 or RB2/P130 impaired the terminal adipocyte differentiation and gave rise to dysregulated adipose cells, with alteration in lipid uptake and release. For the first time, we evidenced that RB2/P130 plays a role in bone marrow adipogenesis. Our data suggest that while the inactivation of retinoblastoma proteins may delay the onset of last cell division and allow more BMSC to be committed to adipocyte, it did not allow a permanent cell cycle exit, which is a prerequisite for adipocyte terminal maturation.

Identification of Rorβ targets in cultured osteoblasts and in human bone

Control of osteoblastic bone formation involves the cumulative action of numerous transcription factors, including both activating and repressive functions that are important during specific stages of differentiation. The nuclear receptor retinoic acid receptor-related orphan receptor β (Rorβ) has been recently shown to suppress the osteogenic phenotype in cultured osteoblasts, and is highly upregulated in bone marrow-derived osteogenic precursors isolated from aged osteoporotic mice, suggesting Rorβ is an important regulator of osteoblast function. However the specific gene expression patterns elicited by Rorβ are unknown. Using microarray analysis, we identified 281 genes regulated by Rorβ in an MC3T3-E1 mouse osteoblast cell model (MC3T3-Rorβ-GFP). Pathway analysis revealed alterations in genes involved in MAPK signaling, genes involved in extracellular matrix (ECM) regulation, and cytokine-receptor interactions. Whereas the identified Rorβ-regulated ECM genes normally decline during osteoblastic differentiation, they were highly upregulated in this non-mineralizing MC3T3-Rorβ-GFP model system, suggesting that Rorβ may exert its anti-osteogenic effects through ECM disruption. Consistent with these in vitro findings, the expression of both RORβ and a subset of RORβ-regulated genes were increased in bone biopsies from postmenopausal women (73±7 years old) compared to premenopausal women (30±5 years old), suggesting a role for RORβ in human age-related bone loss. Collectively, these data demonstrate that Rorβ regulates known osteogenic pathways, and may represent a novel therapeutic target for age-associated bone loss.

Comparison of uncultured marrow mononuclear cells and culture-expanded mesenchymal stem cells in 3D collagen-chitosan microbeads for orthopedic tissue engineering

Stem cell-based therapies have shown promise in enhancing repair of bone and cartilage. Marrow-derived mesenchymal stem cells (MSC) are typically expanded in vitro to increase cell number, but this process is lengthy, costly, and there is a risk of contamination and altered cellular properties. Potential advantages of using fresh uncultured bone marrow mononuclear cells (BMMC) include heterotypic cell and paracrine interactions between MSC and other marrow-derived cells including hematopoietic, endothelial, and other progenitor cells. In the present study, we compared the osteogenic and chondrogenic potential of freshly isolated BMMC to that of cultured-expanded MSC, when encapsulated in three-dimensional (3D) collagen-chitosan microbeads. The effect of low and high oxygen tension on cell function and differentiation into orthopedic lineages was also examined. Freshly isolated rat BMMC (25 × 10(6) cells/mL, containing an estimated 5 × 10(4) MSC/mL) or purified and culture-expanded rat bone marrow-derived MSC (2 × 10(5) cells/mL) were added to a 65-35 wt% collagen-chitosan hydrogel mixture and fabricated into 3D microbeads by emulsification and thermal gelation. Microbeads were cultured in control MSC growth media in either 20% O2 (normoxia) or 5% O2 (hypoxia) for an initial 3 days, and then in control, osteogenic, or chondrogenic media for an additional 21 days. Microbead preparations were evaluated for viability, total DNA content, calcium deposition, and osteocalcin and sulfated glycosaminoglycan expression, and they were examined histologically. Hypoxia enhanced initial progenitor cell survival in fresh BMMC-microbeads, but it did not enhance osteogenic potential. Fresh uncultured BMMC-microbeads showed a similar degree of osteogenesis as culture-expanded MSC-microbeads, even though they initially contained only 1/10th the number of MSC. Chondrogenic differentiation was not strongly supported in any of the microbead formulations. This study demonstrates the microbead-based approach to culturing and delivering cells for tissue regeneration, and suggests that fresh BMMC may be an alternative to using culture-expanded MSC for bone tissue engineering.

Osteogenesis and expression of the bone marrow niche in endothelial cell-depleted HipOPs

The identification and purification of murine multipotent mesenchymal stem cells (MSCs) have been difficult due to their low frequency, the presence of contaminating cell types and lack of unambiguous markers. Using a magnetic micro-beads negative selection technique to remove hematopoietic cells from mouse bone marrow stromal cells (BMSCs), our lab recently isolated a highly purified osteoprogenitor (HipOP) population that was also enriched for other mesenchymal precursors, including MSCs [Itoh and Aubin, 2009]. We now report that HipOPs are also highly enriched in vascular endothelial cells (VECs), which we hypothesized were an accessory cell type regulating osteogenesis. However, when VECs were immunodepleted from HipOPs with anti-CD31 antibodies, the resulting CD31(-) HipOP population had equal osteogenic capacity to the HipOPs in vitro and in vivo. Analysis of gene expression of Ncad, Pth1r, Ang1, Cxcl12, Jag1, Pdgfr-β, α-sma, Desmin, and Ng2 suggested that both HipOPs and CD31(-) HipOPs are hemopoietic stem cell (HSC) niche populations. However, the data support the view that osteoblast differentiation and depletion of VECs modulate the HSC niche.

The changing balance between osteoblastogenesis and adipogenesis in aging and its impact on hematopoiesis

Osteoblasts (OBs) and adipocytes (APs) share a common mesenchymal ancestor. It is now clear that mesenchymal stem cell (MSC) maturation along the OB lineage comes at the expense of adipogenesis and vice versa. During aging, this balance increasingly favors the formation of APs. Hematopoiesis also slowly declines during the aging process. The role of OB lineage cells in hematopoiesis has been studied, but less is known about how APs regulate hematopoiesis. A few studies have demonstrated a negative relationship between APs and hematopoiesis; however, there is also evidence that brown adipose tissue (BAT) may promote hematopoiesis. This review will examine the current knowledge of how adipogenesis and osteogenesis change with aging and the implications of this changing environment on hematopoeisis.

Evaluation of a novel non-destructive catch and release technology for harvesting autologous adult stem cells

BACKGROUND

Cell based therapies are required now to meet the critical care needs of paediatrics and healthy ageing in an increasingly long-lived human population. Repair of compromised tissue by supporting autologous regeneration is a life changing objective uniting the fields of medical science and engineering. Adipose stem cells (adSCs) are a compelling candidate for use in cell based medicine due to their plasticity and residence in numerous tissues. Adipose found in all animals contains a relatively high concentration of stem cells and is easily isolated by a minimally invasive clinical intervention; such as liposuction.

METHODS

This study utilised primary rat adipose to validate a novel strategy for selecting adult stem cells. Experiments explored the use of large, very dense cell-specific antibody loaded isolation beads (diameter 5x-10x greater than target cells) which overcome the problem of endocytosis and have proved to be very effective in cell isolation from minimally processed primary tissue. The technique also benefited from pH mediated release, which enabled elution of captured cells using a simple pH shift.

RESULTS

Large beads successfully captured and released adSCs from rat adipose, which were characterised using a combination of microscopy, flow cytometry and PCR. The resultant purified cell population retains minimal capture artefact facilitating autologous reperfusion or application in in vitro models.

CONCLUSION

Although evidenced here for adSCs, this approach provides a technological advance at a platform level; whereby it can be applied to isolate any cell population for which there is a characterised surface antigen.

Mesenchymal stem cells and nano-structured surfaces

Mesenchymal stem cells (MSCs) represent multipotent stromal cells that can differentiate into a variety of cell types, including osteoblasts (bone cells), chondrocytes (cartilage cells), and adipocytes (fat cells). Their multi-potency provides a great promise as a cell source for tissue engineering and cell-based therapy for many diseases, particularly bone diseases and bone formation. To be able to direct and modulate the differentiation of MSCs into the desired cell types in situ in the tissue, nanotechnology is introduced and used to facilitate or promote cell growth and differentiation. These nano-materials can provide a fine structure and tuneable surface in nanoscales to help the cell adhesion and promote the cell growth and differentiation of MSCs. This could be a dominant direction in future for stem cells based therapy or tissue engineering for various diseases. Therefore, the isolation, manipulation, and differentiation of MSCs are very important steps to make meaningful use of MSCs for disease treatments. In this chapter, we have described a method of isolating MSC from human bone marrow, and how to culture and differentiate them in vitro. We have also provided research methods on how to use MSCs in an in vitro model and how to observe MSC biological response on the surface of nano-scaled materials.

Effects of bisphosphonate treatment on circulating osteogenic endothelial progenitor cells in postmenopausal women

OBJECTIVE

To evaluate whether bisphosphonates modulate vascular calcification by a modification in endothelial progenitor cells (EPCs) coexpressing osteoblastic surface markers and genes.

PATIENTS AND METHODS

We performed a double-blind, randomized study of 20 healthy, early postmenopausal women (from February 1, 2008, through July 31, 2008) treated with placebo or risedronate sodium (35 mg/wk) for 4 months. Peripheral blood was collected at baseline and 4 months to determine serum inflammatory markers, osteoprotegerin, and receptor activator of nuclear factor-κB ligand levels and bone turnover markers. Peripheral blood mononuclear cells were stained for EPC surface markers (CD34, CD133, and vascular endothelial growth factor receptor/kinase insert domain receptor) and osteoblast markers (osteocalcin, alkaline phosphatase, and Stro-1).

RESULTS

Risedronate treatment resulted in a significant down-regulation of gene sets for osteoblast differentiation and proliferation in EPCs with a trend of decreasing EPCs coexpressing osteocalcin.

CONCLUSION

Our findings indicate that bisphosphonate treatment down-regulates the expression of osteogenic genes in EPCs and suggest a possible mechanism by which bisphosphonates may inhibit vascular calcification.