Proteome analysis of rat bone marrow mesenchymal stem cell differentiation

TMT-based quantitative proteomic analysis revealed that FBLN2 and NPR3 are involved in the early osteogenic differentiation of mesenchymal stem cells (MSCs)

The delicate equilibrium between osteoblast and adipocyte differentiation of MSCs is highly regulated. We screened for early-stage osteogenesis- or adipogenesis-based MSCs protein expression profiles using TMT-based quantitative proteomic analysis to identify novel participating molecules. Protein annotation, hierarchical clustering, functional stratification, and protein-protein association assessments were performed. Moreover, two upregulated proteins, namely, FBLN2 and NPR3, were validated to participate in the osteogenic differentiation process of MSCs. After that, we independently downregulated FBLN2 and NPR3 over seven days of osteogenic differentiation, and we performed quantitative proteomics analysis to determine how different proteins were regulated in knockdown vs. control cells. Based on gene ontology (GO) and network analyses, FBLN2 deficiency induced functional alterations associated with biological regulation and stimulus-response, whereas NPR3 deficiency induced functional alterations related to cellular and metabolic processes, and so on. These findings suggested that proteomics remains a useful method for an in-depth study of the MSCs differentiation process. This will assist in comprehensively evaluating its role in osteoporosis and provide additional approaches for identifying as-yet-unidentified effector molecules.

On-demand retrieval of cells three-dimensionally seeded in injectable thioester-based hydrogels

Scaffold systems that can easily encapsulate cells and safely retrieve them at the desired time are important for the advancement of cell-based medicine. In this study, we designed and fabricated thioester-based poly(ethylene glycol) (PEG) hydrogels with injectability and on-demand degradability as new scaffold materials for cells. Hydrogels can be formed in situ within minutes via thioester cross-linking between PEG molecules and can be degraded under mild conditions in response to l-cysteine molecules through thiol exchange occurring at the thioester linkage. Various cell experiments, especially with sucrose, which enables the adjustment of the osmotic pressure around the cells, showed that the damage to the cells during encapsulation and degradation was minimal, indicating the capability of on-demand retrieval of intact cells. This hydrogel system is a versatile tool in the field of cell-based research and applications such as tissue regeneration and regenerative medicine.

Human mesenchymal stem/stromal cells can be three-dimensionally encapsulated in hydrogels cross-linked with thioester linkages. Degrading the cell-embedded hydrogels by l-cysteine molecules enables safe on-demand retrieval of the cells.

Preliminary assessment of an injectable extracellular matrix from decellularized bovine myocardial tissue

The goal of this study was to develop an injectable form of decellularized bovine myocardial tissue matrix which could retain high levels of functional ECM molecules, and could gel at physiological temperature. Dissected ventricular tissue was processed by a detergent-based protocol, lyophilized, enzymatically-digested, and neutralized to form the injectable myocardial matrix (IMM). Histochemical analysis, DNA quantification, and agarose gel electrophoresis demonstrated the efficiency of the applied protocol. Chemical, thermal, morphological, and rheological characterization; protein and sulfated glycosaminoglycan (sGAG) content analysis were performed, in vitro biological properties were evaluated. An in vivo histocompatibility and biodegradability study was performed. Histochemistry revealed complete removal of myocardial cells. DNA content analysis revealed a significant decrease (87%) in the nuclear material, while protein and sGAG contents were highly preserved following decellularization. Soluble IMM was capable of turning into gel form at ∼37 °C, indicating selfassembling property. In vitro findings showed the biomaterial was noncytotoxic, nonhemolytic, and supported the attachment and proliferation of mesenchymal stem cells. In vivo study demonstrated IMM was well-tolerated by rats receiving subcutaneous injection. This work demonstrates that the IMM from decellularized bovine myocardial tissue has the potential for use as a feasible regenerative biomaterial in prospective tissue engineering and regenerative medicine studies.

miR-101-loaded exosomes secreted by bone marrow mesenchymal stem cells requires the FBXW7/HIF1α/FOXP3 axis, facilitating osteogenic differentiation

Exosomes derived from mesenchymal stem cells (MSCs) have emerged as significant mediators of intercellular communication, with studies highlighting their role in the transmission of biological signals between cells. Dominant microRNA (miRNA)-mediated translational repression of messenger RNAs has been extensively investigated in regard to its influence in orchestrating osteogenic differentiation. In the current study, we sought to ascertain the contributory role of miRNA-101 (miR-101) encapsulated in the process of bone marrow mesenchymal stem cell (BMSC)-derived exosomes in osteogenic differentiation. Exosomes were initially extracted from BMSCs at Days 0, 3, 12, and 21 of osteogenic differentiation by ultracentrifugation. Artificial modulation of miR-101 and FBXW7 (silencing and overexpression) were performed in the BMSCs to identify its effects on osteogenic factors, alkaline phosphatase activity, and osteogenic differentiation. Mechanistic exploration was performed to evaluate the binding affinity between miR-101 and FBXW7, the FBXW7-mediated HIF1α ubiquitination, and the HIF1α enrichment in the FOXP3 promoter region. Exosomes from MSCs in the late stage of osteogenic differentiation exhibited enhanced osteogenic differentiation. Upregulated miR-101 in MSC-derived exosomes was detected during osteogenic differentiation, while diminished levels of FBXW7 expression was noted. Importantly, miR-101 was found to specifically bind to the 3'-untranslated region of FBXW7. Meanwhile, data was obtained indicating that FBXW7 could ubiquitinate and degrade HIF1α to repress its upregulation during osteogenic differentiation. HIF1α bound to the promoter region of FOXP3 to facilitate osteogenic differentiation. Ultimately, the findings of the current study demonstrate that BMSC-derived exosomal miR-101 augments osteogenic differentiation in MSCs by inhibiting FBXW7 to regulate the HIF1α/FOXP3 axis.

Evaluation of the biofilm formation of Staphylococcus aureus and Pseudomonas aeruginosa on human umbilical cord CD146+ stem cells and stem cell-based decellularized matrix

This study aims to evaluate the CD146+ stem cells obtained from the human umbilical cord and their extracellular matrix proteins on in vitro Pseudomonas aeruginosa and Staphylococcus aureus biofilms to understand their possible antimicrobial activity. CD146+ stem cells were determined according to cell surface markers and differentiation capacity. Characterization of the decellularized matrix was done with DAPI, Masson's Trichrome staining and proteome analysis. Cell viability/proliferation of cells in co-cultures was evaluated by WST-1 and crystal-violet staining. The effects of cells and decellularized matrix proteins on biofilms were investigated on a drip flow biofilm reactor and their effects on gene expression were determined by RT-qPCR. We observed that CD146/105+ stem cells could differentiate adipogenically and decellularized matrix showed negative DAPI and positive collagen staining with Masson' s Trichrome. Proteome analysis of the decellularized matrix revealed some matrix components and growth factors. Although the decellularized matrix significantly reduced the cell counts of P. aeruginosa, no significant difference was observed for S. aureus cells in both groups. Supporting data was obtained from the gene expression results of P. aeruginosa with the significant down-regulation of rhlR and lasR. For S. aureus, icaADBC genes were significantly up-regulated when grown on the decellularized matrix.

Proteomic Analysis of Morphologically Changed Tissues after Prolonged Dexamethasone Treatment

Prolonged dexamethasone (Dex) administration leads to serious adverse and decrease brain and heart size, muscular atrophy, hemorrhagic liver, and presence of kidney cysts. Herein, we used an untargeted proteomic approach using liquid chromatography-tandem mass spectrometry (LC-MS/MS) for simultaneous identification of changes in proteomes of the major organs in Sprague–Dawley (SD rats post Dex treatment. The comparative and quantitative proteomic analysis of the brain, heart, muscle, liver, and kidney tissues revealed differential expression of proteins (n = 190, 193, 39, 230, and 53, respectively) between Dex-treated and control rats. Functional network analysis using ingenuity pathway analysis (IPA revealed significant differences in regulation of metabolic pathways within the morphologically changed organs that related to: (i) brain—cell morphology, nervous system development, and function and neurological disease; (ii) heart—cellular development, cellular function and maintenance, connective tissue development and function; (iii) skeletal muscle—nucleic acid metabolism, and small molecule biochemical pathways; (iv) liver—lipid metabolism, small molecular biochemistry, and nucleic acid metabolism; and (v) kidney—drug metabolism, organism injury and abnormalities, and renal damage. Our study provides a comprehensive description of the organ-specific proteomic profilesand differentially altered biochemical pathways, after prolonged Dex treatement to understand the molecular basis for development of side effects.

Proteome analysis of human mesenchymal stem cells undergoing chondrogenesis when exposed to the products of various magnesium-based materials degradation

Treatment of physeal fractures (15%–30% of all paediatric fractures) remains a challenge as in approximately 10% of the cases, significant growth disturbance may occur. Bioresorbable Magnesium-based implants represent a strategy to minimize damage (i.e., load support until bone healing without second surgery). Nevertheless, the absence of harmful effects of magnesium-implants and their degradation products on the growth plate should be confirmed. Here, the proteome of human mesenchymal stem cells undergoing chondrogenesis was evaluated when exposed to the products of various Magnesium-based materials degradation. The results of this study indicate that the materials induced regulation of proteins associated with cell chondrogenesis and cartilage formation, which should be beneficial for cartilage regeneration.

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Degradation products from Mg-based materials generated changes in protein expression.

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Relevant proteins involved in cartilage formation were upregulated.

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Potential application of especially Pure-Mg and Mg-10Gd for cartilage regeneration.

Mesenchymal stem cell transplantation in polytrauma: Evaluation of bone and liver healing response in an experimental rat model

PURPOSE

Trauma is the most common cause of death of young people in the world. As known, mesenchymal stem cells (MSCs) accelerate tissue regeneration mechanisms. In our study, we aimed to investigate the effects of MSCs transplantation on the healing of liver and bone tissue by considering trauma secondary inflammatory responses.

METHODS

56 adult Wistar-albino rats were divided into two groups: the polytrauma (liver and bone) (n = 28), and the liver trauma group (n = 28). At 36 h and 5th day after surgery, both rats with polytrauma and with isolated liver injury received either intravenous (IV) or intraperitoneal (IP) injections of MSCs (one million cells per kg body weight). Untreated groups received IV and IP saline injections. At day 21 after surgery, liver, tibia and fibula of the subjects were excised and evaluated for histopathologic and histomorphometric examination. Additionally, whole blood count (white blood cells, hemoglobin and platelets), C-reactive protein (CRP), glucose, alanine aminotransferase (ALT), aspartate aminotransferase (AST), albumin, blood gas, and trauma markers interleukin-1B (IL-1B), interleukin-6 (IL-6), and tumor necrosis factor alpha (TNF alpha) levels were investigated.

RESULTS

In general, MSC transplantations were well tolerated by the subjects. It was found that ALT, CRP, albumin were significantly lower in rats which received MSCs (p < 0.001). Inflammation of the liver and bone tissue in the MSC-injected rats were significantly lower than that of the untreated groups.

CONCLUSIONS

Herewith we have shown that MSC infusion in posttraumatic rats leads to less aggressive and more effective consequences on liver and bone tissue healing. Human MSC treatment for trauma is still in early stages of development; thus standard protocols, and patient inclusion criteria should be established beforehand clinical trials.

Comparative study of mesenchymal stem cells from rat bone marrow and adipose tissue

Several therapeutic products based on mesenchymal stem cells (MSCs) have been translated into clinical applications. MSCs should undergo in vitro culture before a sufficient quantity can be achieved. Hence, both expansion kinetics and the biological characteristics of derived cells from primary culture are pertinent to their applications. In the present study, MSCs were isolated from rat bone marrow and adipose tissue (designated as bMSCs and aMSCs, respectively) and cells were comparatively analyzed regarding cell morphology, proliferation, colony formation, differentiation potential, and immunophenotype following the long-term subculture. No apparent differences could be noticed concerning the morphology between bMSCs and aMSCs. The long-term subculture made both types of cells smaller, weakened their colony-forming ability, and stimulated the proliferation rate. However, bMSCs demonstrated better proliferation and colony-forming ability than aMSCs. No significant difference was observed about the expression of some immunophenotypes (i.e. CD29+/CD90+/CD34-/CD45-) regardless of cell types or population doublings. Notably, bMSCs, but not aMSCs, maintained the differentiation potential well after the long-term subculture. The present study demonstrates that MSCs derived from different tissues can be well expanded for the long term, although cells display gradually declined self-renewal and differentiation potentials to different extents depending on the tissue origins.

Encapsulation of bone marrow-MSCs in PRP-derived fibrin microbeads and preliminary evaluation in a volumetric muscle loss injury rat model: modular muscle tissue engineering

Repair of volumetric muscle loss (VML) injuries is a complicated endeavour which necessitates the collaborative use of different regenerative approaches and technologies. Herein is proposed the development of fibrin-based microbeads (FMs) alone or as a bone marrow mesenchymal stem cell (MSC) encapsulation matrix for modular muscle engineering. FMs were generated through the ionotropic gelation of alginate and fibrinogen obtained from the platelet-rich plasma of whole blood, and then removing the alginate by citrate treatment. FMs were first characterized by FT-IR, SEM and water uptake tests. Then, the stability of FMs and the mitochondrial dehydrogenase activity of the MSCs encapsulated in FMs were evaluated under in vitro culture conditions. Eventually, the regenerative capacity of the cell-devoid and MSCs-encapsulated FMs was evaluated in a rat VML injury model involving 8 × 4×4 mm³-size bilateral defects in the biceps femoris muscles. The histochemical, immunohistochemical and semi-quantitative histomorphological scoring results retrieved at 30, 60 and 180 days demonstrated that the cell-devoid FMs supported muscle regeneration to a great extent. Moreover, MSCs-encapsulated FMs were more effective in shortening the regeneration period of the injured tissue of the rat VML, resulting in good myofibre orientation, while the Sham group resulted in incomplete repair with fibrotic scar tissue formations.

Generation of human umbilical cord vein CD146+ perivascular cell origined three-dimensional vascular construct

Small-diameter vascular grafts are needed for the treatment of coronary artery diseases in the case of limited accessibility of the autologous vessels. Synthetic scaffolds have many disadvantages so in recent years vascular constructs (VCs) made from cellularized natural scaffolds was seen to be very promising but number of studies comprising this area is very limited. In our study, our aim is to generate fully natural triple-layered VC that constitutes all the layers of blood vessel with vascular cells. CD146+ perivascular cells (PCs) were isolated from human umbilical cord vein (HUCV) and differentiated into smooth muscle cells (SMCs) and fibroblasts. They were then combined with collagen type I/elastin/dermatan sulfate and collagen type I/fibrin to form tunica media and tunica adventitia respectively. HUCV endothelial cells (ECs) were seeded on the construct by cell sheet engineering method after fibronectin and heparin coating. Characterization of the VC was performed by immunolabeling, histochemical staining and electron microscopy (SEM and TEM). Differentiated cells were identified by means of immunofluorescent (IF) labeling. SEM and TEM analysis of VCs revealed the presence of three histologic tunicae. Collagen and elastic fibers were observed within the ECM by histochemical staining. The vascular endothelial growth factor receptor expressing ECs in tunica intima; α-SMA expressing SMCs in tunica media and; the tenascin expressing fibroblasts in tunica adventitia were detected by IF labeling. In conclusion, by combining natural scaffolds and vascular cells differentiated from CD146+ PCs, VCs can be generated layer by layer. This study will provide a preliminary blood vessel model for generation of fully natural small-diameter vascular grafts.

Proteomic analysis of porcine mesenchymal stem cells derived from bone marrow and umbilical cord: implication of the proteins involved in the higher migration capability of bone marrow mesenchymal stem cells

INTRODUCTION

Mesenchymal stem cells (MSCs) have the ability to proliferate in vivo with a large variety of differentiation potentials and therefore are widely used as an ideal material for cell therapy. MSCs derived from pig and human sources are similar in many aspects, such as cell immunophenotype and functional characteristics. However, differences in proteomics and the molecular mechanisms of cell functions between porcine bone marrow MSCs (BM-MSCs) and umbilical cord MSCs (UC-MSCs) are largely unknown. To the best of our knowledge, MSCs collected from different tissue have specific phenotype and differentiation ability in response to microenvironment, known as a niche.

METHODS

Porcine BM-MSCs and UC-MSCs were evaluated with flow cytometric and adipogenic and osteogenic differentiation analyses. We used isobaric tagging for relative and absolute quantitation (iTRAQ), combined with liquid chromatography-tandem mass spectrometry, to identify differentially expressed proteins (DEPs) between these two types of MSCs. Kyoto Encyclopedia of Genes and Genomes pathway and phenotype analyses were used to understand the links between cell migration ability and DEPs.

RESULTS

Two separate iTRAQ experiments were conducted, identifying 95 DEPs (95% confidence interval). Five of these proteins were verified by Western blotting. These 95 DEPs were classified in terms of biological regulation, metabolic process, developmental process, immune system process, reproduction, death, growth, signaling, localization, response to stimulus, biological adhesion, and cellular component organization. Our study is the first to show results indicating that porcine BM-MSCs have a higher migration capability than UC-MSCs. Finally, one of the DEPs, Vimentin, was verified to have a positive role in MSC migration.

CONCLUSIONS

These results represent the first attempt to use proteomics specifically targeted to porcine MSCs of different tissues. The identified components should help reveal a variety of tissue-specific functions in tissue-derived MSC populations and could serve as important tools for the regeneration of particular tissues in future stem cell-based tissue engineering studies using animal models.

Effects of arsenic on osteoblast differentiation in vitro and on bone mineral density and microstructure in rats

BACKGROUND

Arsenic is a ubiquitous toxic element and is known to contaminate drinking water in many countries. Several epidemiological studies have shown that arsenic exposure augments the risk of bone disorders. However, the detailed effect and mechanism of inorganic arsenic on osteoblast differentiation of bone marrow stromal cells and bone loss still remain unclear.

OBJECTIVES

We investigated the effects and mechanism of arsenic on osteoblast differentiation in vitro and evaluated bone mineral density (BMD) and bone microstructure in rats at doses relevant to human exposure from drinking water.

METHODS

We used a cell model of rat primary bone marrow stromal cells (BMSCs) and a rat model of long-term exposure with arsenic-contaminated drinking water, and determined bone microstructure and BMD in rats by microcomputed tomography (μCT).

RESULTS

We observed significant attenuation of osteoblast differentiation after exposure of BMSCs to arsenic trioxide (0.5 or 1 μM). After arsenic treatment during differentiation, expression of runt-related transcription factor-2 (Runx2), bone morphogenetic protein-2 (BMP-2), and osteocalcin in BMSCs was inhibited and phosphorylation of enhanced extracellular signal-regulated kinase (ERK) was increased. These altered differentiation-related molecules could be reversed by the ERK inhibitor PD98059. Exposure of rats to arsenic trioxide (0.05 or 0.5 ppm) in drinking water for 12 weeks altered BMD and microstructure, decreased Runx2 expression, and increased ERK phosphorylation in bones. In BMSCs isolated from arsenic-treated rats, osteoblast differentiation was inhibited.

CONCLUSIONS

Our results suggest that arsenic is capable of inhibiting osteoblast differentiation of BMSCs via an ERK-dependent signaling pathway and thus increasing bone loss.

Proteomic analysis of mesenchymal stem cells from normal and deep carious dental pulp

Dental pulp stem cells (DPSCs), precursor cells of odontoblasts, are ideal seed cells for tooth tissue engineering and regeneration. Our previous study has demonstrated that stem cells exist in dental pulp with deep caries and are called carious dental pulp stem cells (CDPSCs). The results indicated that CDPSCs had a higher proliferative and stronger osteogenic differentiation potential than DPSCs. However, the molecular mechanisms responsible for the biological differences between DPSCs and CDPSCs are poorly understood. The aim of this study was to define the molecular features of DPSCs and CDPSCs by comparing the proteomic profiles using two-dimensional fluorescence difference gel electrophoresis (2-D DIGE) in combination with matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS). Our results revealed that there were 18 protein spots differentially expressed between DPSCs and CDPSCs in a narrow pH range of 4 to 7. These differently expressed proteins are mostly involved in the regulation of cell proliferation, differentiation, cell cytoskeleton and motility. In addition, our results suggested that CDPSCs had a higher expression of antioxidative proteins that might protect CDPSCs from oxidative stress. This study explores some potential proteins responsible for the biological differences between DPSCs and CDPSCs and expands our understanding on the molecular mechanisms of mineralization of DPSCs in the formation of the dentin-pulp complex.

Medium conditioned with mesenchymal stromal cell-derived osteoblasts improves the expansion and engraftment properties of cord blood progenitors

Strategies to enhance the expansion of umbilical cord blood hematopoietic stem and progenitor cells (HSPCs) are crucial to enable their widespread application to adults and to overcome important limitations, such as delayed engraftment. Osteoblasts regulate HSPCs under steady-state and also under stress conditions, when HSPCs undergo numerous cycles of expansion. We hypothesized that osteoblasts could provide better stimulation for the expansion of multipotent HSPCs and subsequent hematopoietic recovery than mesenchymal stromal cells. Hence, we assessed the growth and engraftment modulatory activities of mesenchymal stromal cell-derived osteoblasts (M-OSTs) on hematopoietic progenitors. Mesenchymal stromal cells and M-OSTs favored the maintenance of CD34(+) cells. The expansion of cord blood CD34(+) cells and myeloid progenitors was highest in cultures supplemented with unfiltered M-OST-conditioned medium (M-OST CM). In addition, increased expression of cell surface receptors important for the homing of progenitors to the bone marrow, C-X-C chemokine receptor type 4 and lymphocyte function-associated antigen 1, was observed in CM-based cultures. Additionally, M-OST CM positively modulated the engraftment properties of expanded progenitors. Most notably, although human platelet levels remained steady in the first 2 weeks in mice transplanted with HSPCs expanded in standard medium, levels in mice transplanted with M-OST CM HSPCs rose continuously. Consistent with this, short-term human progenitor reconstitution was consistently greater in M-OST recipients. Finally, cytokine array-based profiling revealed increases in insulin-like growth factor binding protein 2, chemokines, and myeloid stimulating cytokines in M-OST CM. In conclusion, this study suggests that M-OSTs represent a new underappreciated source of feeder cells for the expansion of HSPCs with enhanced thrombopoietic activity.

APPLICATION OF DENDRIMER/PLASMID hBMP-2 COMPLEXES LOADED INTO β-TCP/COLLAGEN SCAFFOLD IN THE TREATMENT OF FEMORAL DEFECTS IN RATS

Purpose: Plasmid loading into scaffolds to enhance sustained release of growth factors is an important focus of regenerative medicine. The aim of this study was to build gene-activated matrices (GAMs) and examine the bone augmentation properties. Methods: Generation 5 polyamidoamine dendrimers (G5 dPAMAM)/plasmid recombinant human bone morphogenetic protein-2 (rhBMP-2) complexes were immobilized into beta-tricalcium phosphate (β-TCP)/type I collagen porous scaffolds. After cultured with rat mesenchymal stem cells (rMSCs), transfection efficiencies were examined. The secretion of rhBMP-2 and alkaline phosphatase (ALP) were detected to evaluate the osteogenic properties. Scanning electron microscopy (SEM) was used to observe attachment and proliferation. Moreover, we applied these GAMs directly into freshly created segmental bone defects in rat femurs, and their osteogenic efficiencies were evaluated. Results: Released plasmid complexes were transfected into stem cells and were expressed, which caused osteogenic differentiations of rat mesenchymal stem cells (rMSCs). SEM analysis showed excellent cell attachment. Bioactivity of plasmid rhBMP-2 was maintained in vivo, and the X-ray observation, histological analysis and immunohistochemistry (IHC) of bone tissue demonstrated that the bone healing in segmental femoral defects was enhanced by implantation of GAMs. Conclusions: Such biomaterials offer therapeutic opportunities in critical-sized bone defects.

COMP-Ang1 promotes chondrogenic and osteogenic differentiation of multipotent mesenchymal stem cells through the Ang1/Tie2 signaling pathway

Mesenchymal stem cells (MSCs) are pleiotrophic cells that differentiate to chondrocytes, osteoblasts, or adipocytes, as a result of crosstalk by specific signaling pathways including MAPK pathway. Recently cartilage oligomeric matrix protein angiopoietin1 (COMP-Ang1), an Ang1 variant which is more potent than native Ang1 in phosphorylating Tie2 receptor was developed. The Ang1/Tie2 signaling system not only plays a pivotal role in vessel growth, remodeling, and maturation, but also protective and recruit effect on MSCs. Thus, the aim of the present study was to investigate the differentiate effect of Ang1/Tie2 signaling on MSCs in the presence of chondrogenic, osteogenic and adipogenic induction medium, and to determine the possible mechanisms. Our results clearly demonstrated that MSCs cultured in each induction medium with COMP-Ang1 revealed strongly chondrogenic and osteogenic morphological change (3.5- and 2-fold, respectively) as well as up-regulate each gene, except for adipogenic differentiation. Accordingly, we found that phosphorylation of Tie2 expression lead to phosphorylation of p38 and AKT and then accelerating each differentiation of MSCs to chondrocytes and osteoblasts. Therefore, our findings suggest that COMP-Ang1 present a portal to promote MSCs differentiation to chondrocytes and osteoblasts through Ang1/Tie2 signaling pathway and provide insights into novel therapies for bone diseases.

Human placental alkaline phosphatase as a tracking marker for bone marrow mesenchymal stem cells

Currently, adult mesenchymal stem cells (MSCs) are being evaluated for a wide variety of therapeutic approaches. It has been suggested that MSCs possess regenerative properties when implanted or injected into damaged tissue. However, the efficacy of MSCs in several of the proposed treatments is still controversial. To further explore the therapeutic potential of these cells, it is necessary to trace the fate of individual donor or manipulated cells in the host organism. Recent studies from our lab showed that human placental alkaline phosphatase (hPLAP) is a marker with great potential for cell tracking. However, a potential concern related to this marker is its enzymatic activity, which might alter cell behavior and differentiation by hydrolyzing substrates in the extracellular space and thereby changing the cellular microenvironment. Therefore, the aim of this study was to characterize bone marrow MSCs (BMSCs) derived from hPLAP-transgenic inbred F344 rats (hPLAP-tg) in comparison to wild type (wt) BMSCs. Here, we show that BMSCs from wt and hPLAP-tg donors are indistinguishable in terms of cell morphology, viability, adhesion, immune phenotype, and proliferation as well as in their differentiation capacity over six passages. The expression of the hPLAP marker enzyme was not impaired by extensive in vitro cultivation, osteogenic, adipogenic, or chondrogenic differentiation, or seeding onto two- or three-dimensional biomaterials. Thus, our study underscores the utility of genetically labeled BMSCs isolated from hPLAP-tg donors for long-term tracking of the fate of transplanted MSCs in regenerative therapies.

Human elastin-based recombinant biopolymers improve mesenchymal stem cell differentiation

Elastin-based polypeptides are a class of smart biopolymers representing an important model in the design of biomaterials. The combination of biomimetic materials with cells that have great plasticity provides a promising strategy for the realization of highly engineered cell-based constructs for regenerative medicine and tissue repair applications. Two recombinant biopolymers inspired by human elastin are assessed as coating agents to prepare biomimetic surfaces for cell culture. These substrates are assayed for hBM MSC culture. The coated surfaces are also characterized with AFM to evaluate the topographical features of the deposited biopolymers. The results suggest that the elastin-derived biomimetic surfaces play a stimulatory role on osteogenic differentiation of MSCs.

Immune and inflammatory pathways are involved in inherent bone marrow ossification

BACKGROUND

Bone marrow plays a key role in bone formation and healing. Although a subset of marrow explants ossifies in vitro without excipient osteoinductive factors, some explants do not undergo ossification. The disparity of outcome suggests a significant heterogeneity in marrow tissue in terms of its capacity to undergo osteogenesis.

QUESTIONS/PURPOSES

We sought to identify: (1) proteins and signaling pathways associated with osteogenesis by contrasting the proteomes of ossified and poorly ossified marrow explants; and (2) temporal changes in proteome and signaling pathways of marrow ossification in the early and late phases of bone formation.

METHODS

Explants of marrow were cultured. Media conditioned by ossified (n = 4) and poorly ossified (n = 4) subsets were collected and proteins unique to each group were identified by proteomic analysis. Proteomic data were processed to assess proteins specific to the early phase (Days 1-14) and late phase (Days 15-28) of the culture period. Pathways involved in bone marrow ossification were identified through bioinformatics.

RESULTS

Twenty-eight proteins were unique to ossified samples and eight were unique to poorly ossified ones. Twelve proteins were expressed during the early phase and 15 proteins were specific to the late phase. Several identified pathways corroborated those reported for bone formation in the literature. Immune and inflammatory pathways were specific to ossified samples.

CONCLUSIONS

The marrow explant model indicates the inflammatory and immune pathways to be an integral part of the osteogenesis process.

Temporal profiling and pulsed SILAC labeling identify novel secreted proteins during ex vivo osteoblast differentiation of human stromal stem cells

It is well established that bone forming cells (osteoblasts) secrete proteins with autocrine, paracrine, and endocrine function. However, the identity and functional role for the majority of these secreted and differentially expressed proteins during the osteoblast (OB) differentiation process, is not fully established. To address these questions, we quantified the temporal dynamics of the human stromal (mesenchymal, skeletal) stem cell (hMSC) secretome during ex vivo OB differentiation using stable isotope labeling by amino acids in cell culture (SILAC). In addition, we employed pulsed SILAC labeling to distinguish genuine secreted proteins from intracellular contaminants. We identified 466 potentially secreted proteins that were quantified at 5 time-points during 14-days ex vivo OB differentiation including 41 proteins known to be involved in OB functions. Among these, 315 proteins exhibited more than 2-fold up or down-regulation. The pulsed SILAC method revealed a strong correlation between the fraction of isotope labeling and the subset of proteins known to be secreted and involved in OB differentiation. We verified SILAC data using qRT-PCR analysis of 9 identified potential novel regulators of OB differentiation. Furthermore, we studied the biological effects of one of these proteins, the hormone stanniocalcin 2 (STC2) and demonstrated its autocrine effects in enhancing osteoblastic differentiation of hMSC. In conclusion, combining complete and pulsed SILAC labeling facilitated the identification of novel factors produced by hMSC with potential role in OB differentiation. Our study demonstrates that the secretome of osteoblastic cells is more complex than previously reported and supports the emerging evidence that osteoblastic cells secrete proteins with endocrine functions and regulate cellular processes beyond bone formation.

Reliable typing of systemic amyloidoses through proteomic analysis of subcutaneous adipose tissue

Considering the important advances in treating specific types of systemic amyloidoses, unequivocal typing of amyloid deposits is now essential. Subcutaneous abdominal fat aspiration is the easiest, most common diagnostic procedure. We developed a novel, automated approach, based on Multidimensional Protein Identification Technology, for typing amyloidosis. Fat aspirates were obtained from patients with the most common systemic amyloidoses (ALλ, ALκ, transthyretin, and reactive amyloidosis), with Congo red score more than or equal to 3+, and nonaffected controls. Peptides from extracted and digested proteins were analyzed by Multidimensional Protein Identification Technology. On semiquantitative differential analysis (patients vs controls) of mass spectrometry data, specific proteins up-represented in patients were identified and used as deposit biomarkers. An algorithm was developed to classify patients according to type and abundance of amyloidogenic proteins in samples; in all cases, proteomic characterization was concordant with fibril identification by immunoelectron microscopy and consistent with clinical presentation. Our approach allows reliable amyloid classification using readily available fat aspirates.

Proteomics approaches in the identification of molecular signatures of mesenchymal stem cells

Mesenchymal stem cells (MSCs) are undifferentiated, multi-potent stem cells with the ability to renew. They can differentiate into many types of terminal cells, such as osteoblasts, chondrocytes, adipocytes, myocytes, and neurons. These cells have been applied in tissue engineering as the main cell type to regenerate new tissues. However, a number of issues remain concerning the use of MSCs, such as cell surface markers, the determining factors responsible for their differentiation to terminal cells, and the mechanisms whereby growth factors stimulate MSCs. In this chapter, we will discuss how proteomic techniques have contributed to our current knowledge and how they can be used to address issues currently facing MSC research. The application of proteomics has led to the identification of a special pattern of cell surface protein expression of MSCs. The technique has also contributed to the study of a regulatory network of MSC differentiation to terminal differentiated cells, including osteocytes, chondrocytes, adipocytes, neurons, cardiomyocytes, hepatocytes, and pancreatic islet cells. It has also helped elucidate mechanisms for growth factor-stimulated differentiation of MSCs. Proteomics can, however, not reveal the accurate role of a special pathway and must therefore be combined with other approaches for this purpose. A new generation of proteomic techniques have recently been developed, which will enable a more comprehensive study of MSCs.

The Role of Collagen Type I on Hematopoietic and Mesenchymal Stem Cells Expansion and Differentiation

The three dimensional scaffold of the bone marrow (BM) niches is composed of various elements including extracellular matrix proteins and cell types, such as collagen type I (Col I) and stroma cells. Interaction of stem cells with their microenvironment is important for their regulation. In the marrow, Col I is mostly localized in the endosteal regions. The objective of this work was to investigate the role of Col I in the regulation of Hematopoietic Stem Cells (HSC) and Mesenchymal Stem Cells (MSC) growth. Col I was extracted from rat tail tendons and its purity confirmed. Human BM MSCs and umbilical cord blood (UCB) CD34+cells were used as Stem Cell sources. MSCs were cultured in medium with serum while CB CD34+cells were cultured without serum with cytokines. The impact of increasing concentrations of Col I (0-50 µg mL-1for coating) on the growth of Hematopoietic Progenitor Cells (HPC) and MSCs was investigated by cytometry, microscopy and clonogenic progenitor assays. Only a minority of CD34+cells expressed the Col I receptor α2β1prior to culture, while the opposite was observed when hematopoietic cells were placed in culture. Col I coated surfaces reduced the expansion of hematopoietic cells by 25% compared to control, while expansions of myeloid and MK progenitors were either unchanged or negatively affected by Col I, respectively. The differentiation of HPCs was also affected on Col I as demonstrated by differences in the frequencies of various cell lineages, such as CD34+cells, megakaryocytes (MK), erythrocytes and others. In contrast to HPCs, Col I surfaces increased MSCs proliferation but had little impact on osteoblasts derived from MSCs. Taken together, this study provides new insights into the regulatory activities of Col I on Stem Cells residing in the marrow.

Irradiated Mesenchymal Stem Cells improve the ex vivo expansion of Hematopoietic Progenitors by partly mimicking the bone marrow endosteal environment

Mesenchymal Stem Cells (MSCs) regulate the growth and differentiation of Hematopoietic Progenitor cells (HPCs) through the release of soluble factors or through their differentiation into osteoblasts. We recently demonstrated that expansion of megakaryocyte (MK) progenitors ex vivo had reached a plateau when CD34(+) cells were grown with two optimized cytokine cocktails developed for the growth of MK. Hence, we sought to determine whether co-culture of CD34(+) cells with Bone Marrow (BM) MSCs could further increase the expansion of myeloid and MK progenitors. First, we tested the impact of cell-cell contact and pre-irradiation treatment of the MSCs to identify the condition that best supports HPC expansion. This screen revealed that HPC expansions were generally greater in the non-contact conditions, and that pre-irradiation of the MSCs appeared to be of added benefits. Improved expansion of both myeloid and MK progenitors in co-culture with irradiated MSCs without contact was subsequently confirmed. Next, cytokine array profiling was carried out to investigate why irradiation promoted progenitor expansion. This revealed that the levels of as many as 33 factors were potentially altered. ELISA confirmed the significant up regulation of NT-3 and IGFBP-2. Since, these factors are known to be released by and important for osteogenic and endothelial cells, we investigated and confirmed that irradiation of MSCs induced their rapid differentiation into osteogenic-like cells, but not into endothelial-like cells. Supporting this finding, expansions of myeloid and MK progenitors were increased when CD34(+) cells were co-culture with MSCs-derived osteoblasts. Altogether, these results indicate that the improved expansion of HPCs obtained with irradiated MSCs is due in part to their differentiation into osteoblast-like cells, thereby recreating an endosteal-like environment that provides improved support for HPCs expansion.