Quantitative proteomics analysis of chondrogenic differentiation of C3H10T1/2 mesenchymal stem cells by iTRAQ labeling coupled with on-line two-dimensional LC/MS/MS

Basic Transcription Factor 3 Like 4 Enhances Malignant Phenotypes through Modulating Tumor Cell Function and Immune Microenvironment in Glioma

Recent investigations into the tumor microenvironment have provided insights into the limited response of glioma progression to immunotherapy. However, the specific involvement of basic transcription factor 3 like 4 (BTF3L4) in glioma progression and its correlation with immune cell infiltration remain areas of uncertainty that require further exploration. In the current study, BTF3L4 expression was delineated by using gene expression profiling/interactive analysis and multiplex-immunohistologic staining of tissue microarrays. The prognostic value of BTF3L4 was then assessed by using Cox regression models and Kaplan-Meier methods, and in vitro experiments were conducted to investigate how BTF3L4 protein affects the proliferation, migration, and invasion capabilities of glioma cells. Furthermore, the CIBERSORT and ESTIMATE methods were used to quantify immune cells that correlate to BTF3L4 expression, and multiplex-immunohistologic staining was applied to investigate its correlation with infiltrated immune cells in glioma tissues. These findings revealed higher BTF3L4 expression in glioma tissues compared with non-tumor brain tissues, which correlated with clinical characteristics and worse patient prognosis. Furthermore, the down-regulation of BTF3L4 protein in the glioma cell line had a detrimental effect on cell migration, invasion, and proliferation. In addition, the association between BTF3L4 and key immune molecules in glioma, particularly with the infiltration of CD66B+ neutrophils and programmed death ligand 1 expression, was identified. These results highlight the prognostic significance of BTF3L4 and propose BTF3L4 as a potential target for glioma immune therapy.

PEDF peptide plus hyaluronic acid stimulates cartilage regeneration in osteoarthritis via STAT3-mediated chondrogenesis

Aims

Pigment epithelium-derived factor (PEDF) is known to induce several types of tissue regeneration by activating tissue-specific stem cells. Here, we investigated the therapeutic potential of PEDF 29-mer peptide in the damaged articular cartilage (AC) in rat osteoarthritis (OA).

Methods

Mesenchymal stem/stromal cells (MSCs) were isolated from rat bone marrow (BM) and used to evaluate the impact of 29-mer on chondrogenic differentiation of BM-MSCs in culture. Knee OA was induced in rats by a single intra-articular injection of monosodium iodoacetate (MIA) in the right knees (set to day 0). The 29-mer dissolved in 5% hyaluronic acid (HA) was intra-articularly injected into right knees at day 8 and 12 after MIA injection. Subsequently, the therapeutic effect of the 29-mer/HA on OA was evaluated by the Osteoarthritis Research Society International (OARSI) histopathological scoring system and changes in hind paw weight distribution, respectively. The regeneration of chondrocytes in damaged AC was detected by dual-immunostaining of 5-bromo-2'-deoxyuridine (BrdU) and chondrogenic markers.

Results

The 29-mer promoted expansion and chondrogenic differentiation of BM-MSCs cultured in different defined media. MIA injection caused chondrocyte death throughout the AC, with cartilage degeneration thereafter. The 29-mer/HA treatment induced extensive chondrocyte regeneration in the damaged AC and suppressed MIA-induced synovitis, accompanied by the recovery of cartilage matrix. Pharmacological inhibitors of PEDF receptor (PEDFR) and signal transducer and activator of transcription 3 (STAT3) signalling substantially blocked the chondrogenic promoting activity of 29-mer on the cultured BM-MSCs and injured AC.

Conclusion

The 29-mer/HA formulation effectively induces chondrocyte regeneration and formation of cartilage matrix in the damaged AC.

Sensory and motor fibroblasts have different protein expression patterns and exert different growth promoting effects on sensory and motor neurons

Functional reconstruction after peripheral nerve injury depends on the ability of the regenerated sensory and motor axons to re-innervate the suitable target organs. Therefore, it is essential to explore the cellular mechanisms of peripheral nerve-specific regeneration. In a previous study, we found that sensory and motor fibroblasts can guide Schwann cells to migrate towards the same phenotype. In the present paper, we analyzed the different effects of sensory and motor fibroblasts on sensory or motor neurons. The fibroblasts and neurons co-culture assay showed that compared with motor fibroblasts, sensory fibroblasts promote the neurite outgrowth of sensory neurons on a larger scale, and vice versa. Furthermore, a higher proportion of sensory or motor fibroblasts migrated towards their respective (sensory or motor) neurons. Meanwhile, a comparative proteomic approach was applied to obtain the protein expression profiles of sensory and motor fibroblasts. Among a total of 2597 overlapping proteins identified, we counted 148 differentially expressed items, of those 116 had a significantly higher expression in sensory fibroblasts, and 32 had a significantly greater expression in motor fibroblasts. Functional categorization revealed that differentially expressed proteins were involved in regeneration, axon guidance and cytoskeleton organization, all of which might play a critical role in peripheral nerve-specific regeneration. After nerve crush injury, ITB1 protein expression decreased significantly in motor nerves and increased in sensory nerves. In vitro, ITB1 significantly promoted axonal regeneration of sensory neurons, but had no significant effect on motor neurons. Overall, sensory and motor fibroblasts express different proteins and exert different growth promoting effects on sensory and motor neurons. This comparative proteomic database of sensory and motor fibroblasts could provide future directions for in-depth research on peripheral nerve-specific regeneration. Data are available via ProteomeXchange with identifier PXD034827.

Engineering cartilage graft using mesenchymal stem cell laden polyacrylamide-galactoxyloglucan hydrogel for transplantation

Hydrogels are reported to have various biomedical field applications, and many reports also suggest that soft gels promote stem cell differentiation. Chondrogenic differentiation of mesenchymal stem cells (MSC) is significant in articular cartilage repair. This study focuses on polysaccharide-based hydrogels which enhance chondrocyte lineage differentiation of MSC when grown in the hydrogels. This study implies that the prepared hydrogels promote specific lineage without any external chemical induction factors. The techniques, including immunofluorescence and functional assays to assess the differentiation and in vivo implantation, were employed. All observations paved the way towards confirmation that the galactoxyloglucan-based hydrogel is an attractive candidate for supporting stem cell growth and cartilaginous differentiation.

Comparative antler proteome of sika deer from different developmental stages

Antler is a special bone tissue that has the ability to regenerate completely periodically. It is the fastest growing bone in the animal kingdom. Antler provides a valuable research model for bone growth and mineralization. Antler grows longitudinally by endochondral ossification with their growth center located in its tip. Many scholars have carried out detailed studies on morphology and gene expression of antler tip. However, few scholars have analyzed the protein expression patterns of antler tip at different development stages. This study used label-free proteomics approach to analyze the protein expression dynamics of the antler tip in six developmental periods (15, 25, 45, 65, 100 and 130 days after the previous antler cast) and costal cartilage. In result, 2052 proteins were confidently quantified, including 1937 antler proteins and 1044 costal cartilage proteins. Moreover, 913 antler core proteins and 132 antler-special proteins were obtained. Besides, the stages special proteins and differentially expressed proteins (DEPs) in different development stages were analyzed. A total of 875 DEPs were determined by one-way AVOVA. It is found that the growth period (15, 25, 45 and 65 days) showed more up-regulated protein including several chondrogenesis-associated proteins (collagen types II, collagen types XI, HAPLN1, PAPSS1 and PAPSS2). In ossification stages, the up-regulated proteins related with lysosome (CTSD, CTSB, MMP9, CAII) indicated that the antler has higher bone remodeling activity. Given the up-regulated expression of immune-related molecules (S100A7, CATHL7, LTF, AZU1, ELANE and MPO), we speculate that the local immune system may contribute to the ossification of antler tip. In conclusion, proteomics technology was used to deeply analyze the protein expression patterns of antler at different development stages. This provides a strong support for the research on the molecular regulation mechanism of rapid growth and ossification of velvet antler.

Comparative Proteomic Analysis of Differentially Expressed Proteins between Injured Sensory and Motor Nerves after Peripheral Nerve Transection

Peripheral nerve repair and functional recovery depend on the rate of nerve regeneration and the quality of target reinnervation. It is important to fully understand the cellular and molecular basis underlying the specificity of peripheral nerve regeneration, which means achieving corresponding correct pathfinding and accurate target reinnervation for regrowing motor and sensory axons. In this study, a quantitative proteomic technique, based on isobaric tags for relative and absolute quantitation (iTRAQ), was used to profile the protein expression pattern between single motor and sensory nerves at 14 days after peripheral nerve transection. Among a total of 1259 proteins identified, 176 proteins showed the differential expressions between injured motor and sensory nerves. Quantitative RT-PCR and western blot analysis were applied to validate the proteomic data on representative differentially expressed proteins. Functional categorization indicated that differentially expressed proteins were linked to a diverse array of molecular functions, including axonogenesis, response to axon injury, tissue remodeling, axon ensheathment, cell proliferation and adhesion, vesicle-mediated transport, response to oxidative stress, internal signal cascade, and macromolecular complex assembly, which might play an essential role in peripheral motor and sensory nerve regeneration. Overall, we hope that the proteomic database obtained in this study could serve as a solid foundation for the comprehensive investigation of differentially expressed proteins between injured motor and sensory nerves and for the mechanism elucidation of the specificity of peripheral nerve regeneration. Data are available via ProteomeXchange with identifier PXD022097.

Targeted Proteomic Analysis of Small GTPases in Murine Adipogenesis

Small GTPases are essential signaling molecules for regulating glucose uptake in adipose tissues upon insulin stimulation, and this regulation maintains an appropriate range of glycemia. The involvement of small GTPases in adipogenesis, however, has not been systemically investigated. In this study, we applied a high-throughput scheduled multiple-reaction monitoring (MRM) method, along with the use of synthetic stable isotope-labeled peptides, to identify differentially expressed small GTPase proteins during adipogenesis of cultured murine cells. We were able to quantify the relative levels of expression of 55 and 49 small GTPases accompanied by adipogenic differentiation in 3T3-L1 and C3H10T1/2 cells, respectively. When compared with analysis conducted in the data-dependent acquisition (DDA) mode, the MRM-based proteomic platform substantially increased the coverage of the small GTPase proteome. Western blot analysis further corroborated the MRM quantification results for selected small GTPases. Interestingly, overall a significant number of small GTPases were down-regulated during adipogenesis. Among them, the expression levels of Rab32 protein were consistently lower in differentiated adipocytes than the corresponding undifferentiated precursors in both cell lines. Overexpression of Rab32 in 3T3-L1 and C3H10T1/2 cells prior to adipogenesis induction suppressed their differentiation. Together, this is the first comprehensive analysis of the alterations in small GTPase proteome during adipogenesis, and we reveal a previously unrecognized role of Rab32 in adipogenic differentiation.

Isolation and Characterization of Extraocular Muscle-Derived Muscle Progenitor Cells from Normal and Graves' Orbitopathy Patients

Mesenchymal stem cells (MSCs) are useful for various purposes, including tissue engineering, regeneration, and gene therapy. MSCs isolated from extraocular muscles (EOMs) can be easily expanded in vitro, and can undergo multilineage differentiations involving adipogenesis, chondrogenesis, osteogenesis, and even neuronal or myogenic differentiation. This study aimed to isolate, characterize, and compare extraocular muscle-derived muscle progenitor cells (EOM-MPCs) from normal subjects and patients with Graves' orbitopathy (GO). EOM was obtained during strabismus surgery. Flow cytometry was conducted to identify CD surface antigens such as CD34, CD45, CD44, CD59, CD73, and CD90. We quantitated various cytokines secreted from MSCs, including interleukin (IL)-1α, IL-2, IL-6, IL-8, IL-10, IL-12, IL17A, tumor necrosis factor (TNF)-α, and interferon (IFN)-γ, using a multi-analysis enzyme-linked immunosorbent assay array kit. We performed Oil Red O staining for adipogenesis, Alzarin Red staining for osteogenesis, Alcian blue staining for chondrogenesis, and polymerase chain reaction to measure messenger RNA expression during myogenesis. Our results show that EOM-MPCs from normal subjects and GO patients had similar levels of surface antigen expression and cytokine secretion. There was also no significant difference in the multilineage differentiation of adipocytes, chondrocytes, osteocytes, and myoblasts from EOM-MPCs taken from normal subjects and GO patients. However, hyaluronic acid synthetase 2 expression was higher after induction with tafluprost in EOM-MPCs from GO patients when compared with normal subjects. Together, these results show that EOM-MPCs derived from normal subjects are a good source for stem cell-based therapy for various disorders.

Vagus Nerve Stimulation Alleviates Hepatic Ischemia and Reperfusion Injury by Regulating Glutathione Production and Transformation

Inflammation and oxidative stress are pivotal mechanisms for the pathogenesis of ischemia and reperfusion injury (IRI). Vagus nerve stimulation (VNS) may participate in maintaining oxidative homeostasis and response to external stimulus or injury. We investigated whether the in vivo VNS can protect the liver from IRI. In this study, hepatic IRI were induced by ligating the vessels supplying the left and middle lobes of the liver, which underwent 1 h occlusion followed with 24 h reperfusion. VNS was initiated 15 min after ischemia and continued 30 min. Hepatic function, histology, and apoptosis rates were evaluated after 24 h reperfusion. Compared with the IRI group, VNS significantly improved hepatic function. The protective effect was accompanied by a reduction in histological damage in the ischemic area, and the apoptosis rate of hepatocytes has considerable reduction. To find the underlying mechanism, proteomic analysis was performed and differential expression of glutathione synthetase (GSS) and glutathione S-transferase (GST) was observed. Subsequently, test results indicated that VNS upregulated the expression of mRNA and protein of GSS and GST. Meanwhile, VNS increased the plasma levels of glutathione and glutathione peroxidases. We found that VNS alleviated hepatic IRI by upregulating the antioxidant glutathione via the GSS/glutathione/GST signaling pathway.

Exploring the roles of MACIT and multiplexin collagens in stem cells and cancer

The extracellular matrix (ECM) is ubiquitously involved in neoplastic transformation, tumour growth and metastatic dissemination, and the interplay between tumour and stromal cells and the ECM is now considered crucial for the formation of a tumour-supporting microenvironment. The 28 different collagens (Col) form a major ECM protein family and display extraordinary functional diversity in tissue homeostasis as well as in pathological conditions, with functions ranging from structural support for tissues to regulatory binding activities and storage of biologically active cryptic domains releasable through ECM proteolysis. Two subfamilies of collagens, namely the plasma membrane-associated collagens with interrupted triple-helices (MACITs, including ColXIII, ColXXIII and ColXXV) and the basement membrane-associated collagens with multiple triple-helix domains with interruptions (multiplexins, including ColXV and ColXVIII), have highly interesting regulatory functions in tissue and organ development, as well as in various diseases, including cancer. An increasing, albeit yet sparse, data suggest that these collagens play crucial roles in conveying regulatory signals from the extracellular space to cells. We summarize here the current knowledge about MACITs and multiplexins as regulators of stemness and oncogenic processes, as well as their roles in influencing cell fate decisions in healthy and cancerous tissues. In addition, we present a bioinformatic analysis of the impacts of MACITs and multiplexins transcript levels on the prognosis of patients representing a wide array of malignant diseases, to aid future diagnostic and therapeutic efforts.

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.

Integrated Multi-Assay Culture Model for Stem Cell Chondrogenic Differentiation

Recent osteochondral repair strategies highlight the promise of mesenchymal progenitors, an accessible stem cell source with osteogenic and chondrogenic potential, used in conjunction with biomaterials for tissue engineering. For this, regenerative medicine approaches require robust models to ensure selected cell populations can generate the desired cell type in a reproducible and measurable manner. Techniques for in vitro chondrogenic differentiation are well-established but largely qualitative, relying on sample staining and imaging. To facilitate the in vitro screening of pro-chondrogenic treatments, a 3D micropellet culture combined with three quantitative GAG assays has been developed, with a fourth parallel assay measuring sample content to enable normalisation. The effect of transforming growth factor beta (TGF-β) used to validate this culture format produced a measurable increase in proteoglycan production in the parallel assays, in both 2D and 3D culture configurations. When compared to traditional micropellets, the monolayer format appeared less able to detect changes in cell differentiation, however in-well 3D cultures displayed a significant differential response. Effects on collagen 2 expression confirmed these observations. Based on these results, a microplate format was optimised for 3D culture, in a high-throughput in-well configuration. This model showed improved sensitivity and confirmed the 3D micropellet in-well quantitative assays as an effective differentiation format compatible with streamlined, high-throughput chondrogenic screens.

MicroRNA‑31 promotes chondrocyte proliferation by targeting C‑X‑C motif chemokine ligand 12

The present study aimed to investigate the biological function and underlying molecular mechanisms of miR-31 in osteoarthritis (OA). Reverse transcription-quantitative polymerase chain reaction was used to detect miR-31 expression, and it was found that miR-31 was downregulated in the cartilage tissues of OA patients. microRNA.org was used to predict the gene targets of miR-31, and dual luciferase reporter assays were used to verify that C-X-C motif chemokine ligand 12 (CXCL12) was a direct target of miR-31. The human chondrocyte cell line CHON-001 was used to perform MTT and cell migration assays. Western blotting was used to measure the protein expression of CXCL12, type I collagen and aggrecan. The results suggested that CXCL12 was a target of miR-31, and the expression of CXCL12 was negatively regulated by miR-31 in CHON-001 cells. miR-31 increased CHON-001 cell viability and migration, as well as the expression of type I collagen and aggrecan. Furthermore, the overexpression of CXCL12 eliminated the effects of miR-31 mimics on CHON-001 cells. In conclusion, the data indicated that miR-31 promoted chondrocyte viability and migration by directly targeting CXCL12, which provided evidence for CXCL12 as a potential target in OA therapy.

Label-Free Quantification Proteomics for the Identification of Mesenchymal Stromal Cell Matrisome Inside 3D Poly(Ethylene Glycol) Hydrogels

Cells modulate the functional properties of their environment by depositing extracellular matrix (ECM) proteins during biological processes in vivo and in vitro. Despite the ECMs central role in tissue formation, its quantification in hydrogels like Matrigel, which have a complex materials-inherent biopolymer composition is exceptionally challenging. Here, the use of protein-free, synthetic poly(ethylene glycol) hydrogels enables the analysis of deposited human bone marrow mesenchymal stromal cells ECM directly harvested from fresh 3D cell cultures by a tandem mass spectrometry (LC-MS/MS) method. In this study, it is proved that a label-free LC-MS/MS quantification method can selectively identify proteins deposited in 3D synthetic hydrogels following different growth factor (GF) treatments. Furthermore, it is shown that the sequence in which GFs are administered and the choice of stimuli significantly influences the number and abundance of ECM proteins. Therefore, this provides a versatile method to optimize GF treatments in synthetic hydrogel-based regenerative medicine and tissue engineering approaches.

Comparative Analysis of Human Adipose-Derived Mesenchymal Stem Cells from Orbital and Abdominal Fat

Adipose tissue contains abundant multipotent mesenchymal stem cells with strong proliferative and differentiating potential into adipocytes, osteocytes, and chondrocytes. However, adipose-derived mesenchymal stem cells (ASCs) showed variable characteristics based on the tissue-harvesting site. This study aimed at comparing human adipose-derived mesenchymal stem cell from the orbit (Orbital ASCs) and abdomen (Abdominal ASCs). Orbital and abdominal ASCs were isolated during an upper or lower blepharoplasty operation and liposuction, respectively. Flow cytometric analysis was done to analyze the surface antigens of ASCs, and cytokine profiles were measured using Luminex assay kit. The multilineage potential of both ASCs was investigated using Oil Red O, alizarin red, and alcian staining. Reverse transcriptase polymerase chain reaction (RT-PCR) was performed to measure mRNA levels of genes involved in these trilineage differentiations. Our results showed that both types of ASCs expressed the cell surface markers which are commonly expressed stem cells; however, orbital-ASCs showed higher expressions of CD73, CD90, CD105, and CD146 than abdominal ASCs. Unlikely, orbital-ASC expressed CD31, CD45 and HLA-DR lesser than abdominal-ASCs. Orbital ASCs secreted higher concentrations of eotaxin, fractalkine, IP-10, GRO, MCP-1, IL-6, IL-8, and RANTES but lower MIP-1α, FGF-2, and VEGF concentrations than abdominal-ASCs. Our result showed that orbital ASCs have higher potential towards adipogenic and osteogenic differentiation but lower tendency to chondrogenesis when compared with abdominal ASCs. In conclusion, tissue-harvesting site is a strong determinant for characterization of adipose-derived mesenchymal stem cells. Understanding defining phenotypes of such cells is useful for making suitable choices in different regenerative clinical indications.

miR-30b regulates chondrogenic differentiation of mouse embryo-derived stem cells by targeting SOX9

The present study aimed to investigate the mechanisms underlying microRNA (miRNA)-mediated regulation of chondrogenic differentiation. Mouse embryo-derived stem cells C3H10T1/2 were cultured and chondrogenic differentiation was induced using transforming growth factor-β3 (TGF-β3). In addition, miRNA expression profiles were detected via miRNA array analysis, and quantitative polymerase chain reaction was performed to verify the differentially expressed miRNAs. Furthermore, bioinformatics software was used to predict the putative targets and the prediction was validated by dual-luciferase reporter assays and western blot analysis. In addition, cell proliferation and glycosaminoglycans were measured by a direct cell count method and alcian blue staining, respectively. Compared with the control group, 86 miRNAs were identified as differentially expressed in TGF-β3-induced cells and the expression levels of 28 miRNAs were increased while the remaining 58 miRNAs exhibited a decline in expression. Amongst the differentially expressed miRNAs, miR-30b expression was observed to have significantly decreased during chondrogenic differentiation. SOX9 is a target gene of miR-30b, and miR-30b inhibits SOX9 expression during chondrogenic differentiation. Furthermore, the alcian blue staining results demonstrated that miR-30b inhibited early chondrogenic differentiation. However, the data of the present study indicated that miR-30b had no influence on C3H10T1/2 cell line proliferation. In conclusion, miR-30b is a key negative regulator of TGF-β3-induced C3H10T1/2 cell chondrogenic differentiation, which functions by directly targeting SOX9.

Rho-kinase inhibitor Y-27632 and hypoxia synergistically enhance chondrocytic phenotype and modify S100 protein profiles in human chondrosarcoma cells

Articular chondrocytes are slowly dividing cells that tend to lose their cell type-specific phenotype and ability to produce structurally and functionally correct cartilage tissue when cultured. Thus, culture conditions, which enhance the maintenance of chondrocyte phenotype would be very useful for cartilage research. Here we show that Rho-kinase inhibition by Y-27632 under hypoxic conditions efficiently maintains and even enhances chondrocyte-specific extracellular matrix production by chondrocytic cells. The effects of long-term Y-27632 exposure to human chondrosarcoma 2/8 cell phenotype maintenance and extracellular matrix production were studied at normoxia and at a 5% low oxygen atmosphere. Y-27632 treatment at normoxia induced ACAN and COL2A1 gene up-regulation and a minor increase of sulfated glycosaminoglycans (sGAGs), while type II collagen expression was not significantly up-regulated. A further increase in expression of ACAN and COL2A1 was achieved with Y-27632 treatment and hypoxia. The production of sGAGs increased by 65.8%, and ELISA analysis revealed a 6-fold up-regulation of type II collagen. Y-27632 also induced the up-regulation of S100-A1 and S100-B proteins and modified the expression of several other S100 protein family members, such as S100-A4, S100-A6, S100-A13 and S100-A16. The up-regulation of S100-A1 and S100-B proteins is suggested to enhance the chondrocytic phenotype of these cells.

miRNA-140 inhibits C3H10T1/2 mesenchymal stem cell proliferation by targeting CXCL12 during transforming growth factor-β3-induced chondrogenic differentiation

The aim of the present study was to investigate the role of microRNA (miRNA or miR)-140 in C3H10T1/2 mesenchymal stem cells (MSCs). Cluster analysis was used to evaluate the miRNA expression profile. The expression level of miRNA‑140 was validated by reverse transcription‑quantitative polymerase chain reaction (RT‑qPCR). TargetScan and microRNA.org databases were used to predict target miRNAs and cartilage‑associated target genes. Binding sites between miR‑140 and the target gene were predicted by bioinformatics software. A dual‑luciferase reporter assay was performed to determine whether miR‑140 could target C‑X‑C motif chemokine ligand 12 (CXCL12). Following the promotion/inhibition of miR‑140, 1, 7 and 14 days following transforming growth factor‑β3 (TGF‑β3)‑induction, western blotting was utilized to evaluate CXCL12 protein levels. MTT assays and alcian blue staining were applied to assess C3H10T1/2 MSC viability and chondrogenic differentiation, respectively. In the TGF‑β3‑induced group, RT‑qPCR verified that the mRNA level of Mus musculus (mmu)‑miR‑140 was significantly elevated when compared with the control group. miR‑140 was predicted to recognize and interact with CXCL12‑3'UTR and the dual luciferase reporter assay further validated that miR‑140 targeted the predicted region of CXCL12. CXCL12 was markedly decreased following miR‑140 overexpression and visibly increased following miR‑140 inhibition. In addition, the level of CXCL12 expression declined as the duration of induction increased. Following the promotion/inhibition of miR‑140, at 1 and 7 days following TGF‑β3‑induction, C3H10T1/2 MSCs inhibited or promoted cell viability, respectively, when compared with the control groups. In addition, in pellets achieved by chondrogenic differentiation following the induction of C3H10T1/2 MSCs for 7 days, alcian blue staining revealed no significant difference in characteristic extracellular matrix glycosaminoglycans between the miR‑140 up and downregulated groups, and their respective control groups. The present study concludes that miRNA‑140 inhibition promoted C3H10T1/2 MSC viability however, not C3H10T1/2 MSC differentiation by targeting and reducing CXCL12 protein levels during the process of TGF‑β3‑induced chondrogenic differentiation. In conclusion, the present study provided a potential target for the treatment of cartilage defection.

Methylparaben and butylparaben alter multipotent mesenchymal stem cell fates towards adipocyte lineage

Paraben esters and their salts are widely used as preservatives in cosmetics, personal care products, pharmaceuticals, and foods. We previously reported that parabens promoted adipocyte differentiation in vitro and increased adiposity but suppressed serum marker of bone formation in vivo. Here, we investigated the effects of parabens (methylparaben and butylparaben) on modulating cell fate of multipotent stem cell line C3H10T1/2. Both parabens modulated adipogenic, osteogenic, and chondrogenic differentiation of C3H10T1/2 cells in vitro. Butylparaben markedly promoted adipogenic differentiation, but suppressed osteogenic and chondrogenic differentiation whereas methylparaben showed similar but less pronounced effects. Moreover, butylparaben, but not methylparaben, was shown to activate peroxisome proliferator-activated receptor (PPAR) γ whereas neither of the paraben was shown to activate glucocorticoid receptor (GR) responsive reporter in C3H10T1/2 cells. The adipogenic effects of butylparaben were significantly attenuated by PPARγ knockdown, but not by GR knockdown. In contrast, paraben's effects on osteoblast differentiation were affected by both knockdowns. Collectively, the results demonstrate opposing effects of parabens on adipogenic and osteoblastogenic/chondrogenic differentiation of multipotent stem cells. In light of the recent findings that parabens are detected in human placenta and milk, our studies provide rationales to study paraben exposure during early development of life in the future.

Limb proportions show developmental plasticity in response to embryo movement

Animals have evolved limb proportions adapted to different environments, but it is not yet clear to what extent these proportions are directly influenced by the environment during prenatal development. The developing skeleton experiences mechanical loading resulting from embryo movement. We tested the hypothesis that environmentally-induced changes in prenatal movement influence embryonic limb growth to alter proportions. We show that incubation temperature influences motility and limb bone growth in West African Dwarf crocodiles, producing altered limb proportions which may, influence post-hatching performance. Pharmacological immobilisation of embryonic chickens revealed that altered motility, independent of temperature, may underpin this growth regulation. Use of the chick also allowed us to merge histological, immunochemical and cell proliferation labelling studies to evaluate changes in growth plate organisation, and unbiased array profiling to identify specific cellular and transcriptional targets of embryo movement. This disclosed that movement alters limb proportions and regulates chondrocyte proliferation in only specific growth plates. This selective targeting is related to intrinsic mTOR (mechanistic target of rapamycin) pathway activity in individual growth plates. Our findings provide new insights into how environmental factors can be integrated to influence cellular activity in growing bones and ultimately gross limb morphology, to generate phenotypic variation during prenatal development.

Comprehensive mass spectrometry based biomarker discovery and validation platform as applied to diabetic kidney disease

A protein biomarker discovery workflow was applied to plasma samples from patients at different stages of diabetic kidney disease. The proteomics platform produced a panel of significant plasma biomarkers that were statistically scrutinised against the current gold standard tests on an analysis of 572 patients. Five proteins were significantly associated with diabetic kidney disease defined by albuminuria, renal impairment (eGFR) and chronic kidney disease staging (CKD Stage ≥1, ROC curve of 0.77). The results prove the suitability and efficacy of the process used, and introduce a biomarker panel with the potential to improve diagnosis of diabetic kidney disease.

Analysis of Reproducibility of Proteome Coverage and Quantitation Using Isobaric Mass Tags (iTRAQ and TMT)

This study aimed to compare the depth and reproducibility of total proteome and differentially expressed protein coverage in technical duplicates and triplicates using iTRAQ 4-plex, iTRAQ 8-plex, and TMT 6-plex reagents. The analysis was undertaken because comprehensive comparisons of isobaric mass tag reproducibility have not been widely reported in the literature. The highest number of proteins was identified with 4-plex, followed by 8-plex and then 6-plex reagents. Quantitative analyses revealed that more differentially expressed proteins were identified with 4-plex reagents than 8-plex reagents and 6-plex reagents. Replicate reproducibility was determined to be ≥69% for technical duplicates and ≥57% for technical triplicates. The results indicate that running an 8-plex or 6-plex experiment instead of a 4-plex experiment resulted in 26 or 39% fewer protein identifications, respectively. When 4-plex spectra were searched with three software tools-ProteinPilot, Mascot, and Proteome Discoverer-the highest number of protein identifications were obtained with Mascot. The analysis of negative controls demonstrated the importance of running experiments as replicates. Overall, this study demonstrates the advantages of using iTRAQ 4-plex reagents over iTRAQ 8-plex and TMT 6-plex reagents, provides estimates of technical duplicate and triplicate reproducibility, and emphasizes the value of running replicate samples.

Proteomic Analysis of the Peri-Infarct Area after Human Umbilical Cord Mesenchymal Stem Cell Transplantation in Experimental Stroke

Among various therapeutic approaches for stroke, treatment with human umbilical cord mesenchymal stem cells (hUC-MSCs) has acquired some promising results. However, the underlying mechanisms remain unclear. We analyzed the protein expression spectrum of the cortical peri-infarction region after ischemic stroke followed by treatment with hUC-MSCs, and found 16 proteins expressed differentially between groups treated with or without hUC-MSCs. These proteins were further determined by Gene Ontology term analysis and network with CD200-CD200R1, CCL21-CXCR3 and transcription factors. Three of them: Abca13, Grb2 and Ptgds were verified by qPCR and ELISA. We found the protein level of Abca13 and the mRNA level of Grb2 consistent with results from the proteomic analysis. Finally, the function of these proteins was described and the potential proteins that deserve to be further studied was also highlighted. Our data may provide possible underlying mechanisms for the treatment of stroke using hUC-MSCs.

A proteomic analysis of chondrogenic, osteogenic and tenogenic constructs from ageing mesenchymal stem cells

Background

Mesenchymal stem cells (MSCs) have prospective applications in regenerative medicine and tissue engineering but to what extent phenotype and differentiation capacity alter with ageing is uncertain. Consequently, any loss in functionality with age would have profound consequences for the maintenance of tissue viability and the quality of tissues. Proteomics enables the set of proteins responsible for a particular cell phenotype to be identified, as well as enabling insights into mechanisms responsible for age-related alterations in musculoskeletal tissues. Few proteomic studies have been undertaken regarding age-related effects on tissue engineered into cartilage and bone, and none for tendon. This study provides a proteome inventory for chondrogenic, osteogenic and tenogenic constructs synthesised from human MSCs, and elucidates proteomic alterations as a consequence of donor age.

Methods

Human bone-marrow derived MSCs from young (n = 4, 21.8 years ± 2.4SD) and old (n = 4, 65.5 years ± 8.3SD) donors were used to make chondrogenic, osteogenic and tenogenic tissue-engineered constructs. We utilised an analytical method relying on extracted peptide intensities as a label-free approach for peptide quantitation by liquid chromatography–mass spectrometry. Results were validated using western blotting.

Results

We identified proteins that were differentially expressed with ageing; 128 proteins in chondrogenic constructs, 207 in tenogenic constructs and four in osteogenic constructs. Differentially regulated proteins were subjected to bioinformatic analysis to ascertain their molecular functions and the signalling pathways. For all construct types, age-affected proteins were involved in altered cell survival and death, and antioxidant and cytoskeletal changes. Energy and protein metabolism were the principle pathways affected in tenogenic constructs, whereas lipid metabolism was strongly affected in chondrogenic constructs and mitochondrial dysfunction in osteogenic constructs.

Conclusions

Our results imply that further work on MSC-based therapeutics for the older population needs to focus on oxidative stress protection. The differentially regulated proteome characterised by this study can potentially guide translational research specifically aimed at effective clinical interventions.

Electronic supplementary material

The online version of this article (doi:10.1186/s13287-016-0384-2) contains supplementary material, which is available to authorized users.

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.

Cells and secretome--towards endogenous cell re-activation for cartilage repair

Regenerative medicine approaches to cartilage tissue repair have mainly been concerned with the implantation of a scaffold material containing monolayer expanded cells into the defect, with the aim to differentiate the cells into chondrocytes. While this may be a valid approach, the secretome of the implanted cells and its effects on the endogenous resident cells, is gaining in interest. This review aims to summarize the knowledge on the secretome of mesenchymal stem cells, including knowledge from other tissues, in order to indicate how these mechanisms may be of value in repairing articular cartilage defects. Potential therapies and their effects on the repair of articular cartilage defects will be discussed, with a focus on the transition from classical cell therapy to the implantation of cell free matrices releasing specific cytokines.

Proteomic Analysis of Engineered Cartilage

Tissue engineering holds promise for the treatment of damaged and diseased tissues, especially for those tissues that do not undergo repair and regeneration readily in situ. Many techniques are available for cell and tissue culturing and differentiation of chondrocytes using a variety of cell types, differentiation methods, and scaffolds. In each case, it is critical to demonstrate the cellular phenotype and tissue composition, with particular attention to the extracellular matrix molecules that play a structural role and that contribute to the mechanical properties of the resulting tissue construct. Mass spectrometry provides an ideal analytical method with which to characterize the full spectrum of proteins produced by tissue-engineered cartilage. Using normal cartilage tissue as a standard, tissue-engineered cartilage can be optimized according to the entire proteome. Proteomic analysis is a complementary approach to biochemical, immunohistochemical, and mechanical testing of cartilage constructs. Proteomics is applicable as an analysis approach to most cartilage constructs generated from a variety of cellular sources including primary chondrocytes, mesenchymal stem cells from bone marrow, adipose tissue, induced pluripotent stem cells, and embryonic stem cells. Additionally, proteomics can be used to optimize novel scaffolds and bioreactor applications, yielding cartilage tissue with the proteomic profile of natural cartilage.

Differential protein expression between chondrogenic differentiated MSCs, undifferentiated MSCs and adult chondrocytes derived from Oryctolagus cuniculus in vitro

OBJECTIVE

This preliminary study aims to determine the differentially expressed proteins from chondrogenic differentiated multipotent stromal cells (cMSCs) in comparison to undifferentiated multipotent stromal cells (MSCs) and adult chondrocytes (ACs).

METHODS

ACs and bone marrow-derived MSCs were harvested from New Zealand White rabbits (n = 3). ACs and cMSCs were embedded in alginate and were cultured using a defined chondrogenic medium containing transforming growth factor-beta 3 (TGF-β3). Chondrogenic expression was determined using type-II collagen, Safranin-O staining and glycosaminoglycan analyses. Two-dimensional gel electrophoresis (2-DE) was used to isolate proteins from MSCs, cMSCs and ACs before being identified using liquid chromatography-mass spectrometry (LC-MS). The differentially expressed proteins were then analyzed using image analysis software.

RESULTS

Both cMSCs and ACs were positively stained with type-II collagen and safranin-O. The expression of glycosaminoglycan in cMSCs was comparable to AC at which the highest level was observed at day-21 (p>0.05). Six protein spots were found to be most differentially expressed between MSCs, cMSCs and ACs. The protein spots cofilin-1 (CFL1) and glycealdehyde-3-phosphate dehydrogenase (GAPD) from cMSCs had expression levels similar to that of ACs whereas the others (ie. MYL6B, ALDOA, TAGLN2, EF1-alpha), did not match the expression level of ACs.

CONCLUSION

Despite having similar phenotypic expressions to ACs, cMSCs expressed proteins which were not typically expected. This may explain the reason for the unexplained lack of improvement in cartilage repair outcomes reported in previous studies.

Identification of stromal differentially expressed proteins in the colon carcinoma by quantitative proteomics

Tumor microenvironment plays very important roles in the carcinogenesis. A variety of stromal cells in the microenvironment have been modified to support the unique needs of the malignant state. This study was to discover stromal differentially expressed proteins (DEPs) that were involved in colon carcinoma carcinogenesis. Laser capture microdissection (LCM) was captured and isolated the stromal cells from colon adenocarcinoma (CAC) and non-neoplastic colon mucosa (NNCM) tissues, respectively. Seventy DEPs were identified between the pooled LCM-enriched CAC and NNCM stroma samples by iTRAQ-based quantitative proteomics. Gene Ontology (GO) relationship analysis revealed that DEPs were hierarchically grouped into 10 clusters, and were involved in multiple biological functions that were altered during carcinogenesis, including extracellular matrix organization, cytoskeleton, transport, metabolism, inflammatory response, protein polymerization, and cell motility. Pathway network analysis revealed 6 networks and 56 network eligible proteins with Ingenuity pathway analysis. Four significant networks functioned in digestive system development and its function, inflammatory disease, and developmental disorder. Eight DEPs (DCN, FN1, PKM2, HSP90B1, S100A9, MYH9, TUBB, and YWHAZ) were validated by Western blotting, and four DEPs (DCN, FN1, PKM2, and HSP90B1) were validated by immunohistochemical analysis. It is the first report of stromal DEPs between CAC and NNCM tissues. It will be helpful to recognize the roles of stromas in the colon carcinoma microenvironment, and improve the understanding of carcinogenesis in colon carcinoma. The present data suggest that DCN, FN1, PKM2, HSP90B1, S100A9, MYH9, TUBB, and YWHAZ might be the potential targets for colon cancer prevention and therapy.

Fibroblast growth factor-1 is a mesenchymal stromal cell-secreted factor stimulating proliferation of osteoarthritic chondrocytes in co-culture

Previously, we showed that mesenchymal stromal cells (MSCs) in co-culture with primary chondrocytes secrete soluble factors that increase chondrocyte proliferation. The objective of this study is to identify these factors. Human primary chondrocytes (hPCs) isolated from late-stage osteoarthritis patients were co-cultured with human bone marrow-derived MSCs (hMSCs) in pellets. Genome-wide mRNA expression analysis and quantitative polymerase chain reactions (qPCR) were used to identify soluble factors that were specifically induced in co-cultures. Immunofluorescent staining combined with cell tracking and enzyme-linked immunosorbent assay (ELISA) were performed to validate up-regulation at the protein level and to identify the cellular origin of the increased proteins. Chemical blockers and neutralizing antibodies were used to elucidate the role of the identified candidate genes in co-cultures. A number of candidate factors were differentially regulated in co-cultures at the mRNA level. Of these, fibroblast growth factor-1 (FGF-1) mRNA and protein expression were markedly increased in co-cultures predominantly due to up-regulated expression in MSCs. Blocking of FGF signaling in co-culture pellets by specific FGF receptor inhibitors or FGF-1 neutralizing antibodies completely blocked hPCs proliferation. We demonstrate that MSCs increase FGF-1 secretion on co-culture with hPCs, which, in turn, is responsible for increased hPCs proliferation in pellet co-cultures.

Chd4 and associated proteins function as corepressors of Sox9 expression during BMP-2-induced chondrogenesis

Mouse embryonic fibroblasts (MEFs) differentiate into fully functional chondrocytes in response to bone morphogenetic protein-2 (BMP-2). However, the comprehensive proteomic aspect of BMP-2-induced chondrogenesis remains unknown. We took advantage of quantitative proteomic analysis based on isobaric tag for relative and absolute quantitation (iTRAQ) and on-line 2D nano-liquid chromatography/tandem mass spectrometry (LC/MS/MS) to identify proteins differentially expressed during BMP-2-induced chondrogenic differentiation of MEFs. We found 85 downregulated proteins, and ingenuity pathways analysis (IPA) revealed a protein-protein network with chromodomain-helicase-DNA-binding protein 4 (Chd4) in the center. Chromatin immunoprecipitation (ChIP) and nuclease hypersensitivity assays showed that Chd4, interacting with Hdac1/2, cooperates with its related proteins Kap1 and Cbx1 to bind at -207/-148 of the Sox9 promoter. We also provided evidence that let-7a targets the 3'UTR of Chd4 to promote chondrogenesis of MEFs. Together, our findings indicate that BMP-2 induced the upregulation of let-7a, targeting Chd4 and positively controlling the chondrogenic differentiation of MEFs. These findings illustrate epigenetic regulation of the chondrogenic differentiation process and also expand the understanding of the involved intracellular mechanisms.

Proteomics analysis of autophagy-deficient Atg7-/- MEFs reveals a close relationship between F-actin and autophagy

Autophagy plays a crucial role in a wide array of physiological processes. To uncover the complex regulatory networks and mechanisms underlying basal autophagy, we performed a quantitative proteomics analysis of autophagy-deficient mouse embryonic fibroblast cells (MEFs) using iTRAQ labeling coupled with on-line 2D LC/MS/MS. We quantified a total of 1234 proteins and identified 114 proteins that were significantly altered (90% confidence interval), including 48 up-regulated proteins and 66 down-regulated proteins. We determined that F-actin was disassembled in autophagy-deficient Atg7(-/-) MEFs. Treatment of the WT MEFs with cytochalasin D (CD), which induces F-actin depolymerization, significantly induced autophagosome formation. However, treatment with cytochalasin D also increased the protein level of p62 under starvation conditions, suggesting that depolymerization of F-actin impaired autophagosome maturation and that the intact F-actin network is required for basal and starvation-induced autophagy. Our results demonstrate a close relationship between F-actin and autophagy and provide the basis for further investigation of their interactions.

Metabolic labeling of human bone marrow mesenchymal stem cells for the quantitative analysis of their chondrogenic differentiation

Human mesenchymal stem cells (hMSCs), residing in bone marrow as well as in the synovial lining of joints, can be triggered to differentiate toward chondrocytes. Thus, hMSCs harbor great therapeutic potential for the repair of cartilage defects in osteoarthritis (OA) and other articular diseases. However, the molecular mechanisms underlying the chondrogenesis process are still in part unknown. In this work, we applied for the first time the stable isotope labeling by amino acids in cell culture (SILAC) technique for the quantitative analysis of protein modulation during the chondrogenic differentiation process of hMSCs. First, we have standardized the metabolic labeling procedure on MSCs isolated from bone marrow (hBMSCs), and we have assessed the quality of chondrogenesis taking place in these conditions. Then, chondrogenic differentiation was induced on these labeled cells, and a quantitative proteomics approach has been followed to evaluate protein changes between two differentiation days. With this strategy, we could identify 622 different proteins by LC-MALDI-TOF/TOF analysis and find 65 proteins whose abundance was significantly modulated between day 2 and day 14 of chondrogenesis. Immunohistochemistry analyses were performed to verify the changes on a panel of six proteins that play different biological roles in the cell: fibronectin, gelsolin, vimentin, alpha-ATPase, mitochondrial superoxide dismutase, and cyclophilin A. All of these proteins were increased at day 14 compared to day 2 of chondrogenic induction, thus being markers of the enhanced extracellular matrix synthesis, cell adhesion, metabolism, and response to stress processes that take place in the early steps of chondrogenesis. Our strategy has allowed an additional insight into both specific protein function and the mechanisms of chondrogenesis and has provided a panel of protein markers of this differentiation process in hBMSCs.

B2A peptide induces chondrogenic differentiation in vitro and enhances cartilage repair in rats

This study investigated whether the synthetic peptide B2A (B2A2-K-NS) could induce in vitro chondrogenic differentiation and enhance the in vivo repair of damaged cartilage in an osteoarthritis model. In vitro, micromass cultures of murine and human stem cells with and without B2A were used as models of chondrogenic differentiation. Micromasses were evaluated for gene expression using microarray analysis and quantitative PCR; and for extracellular matrix production by Alcian blue staining for sulfated glycosaminoglycan and immunochemical detection of collagen type II. In vivo, osteoarthritis was chemically induced in knees of adult rats by an injection of mono-iodoacetate (MIA) into the synovial space. Treatment was administered at 7- and 14 days after the MIA by injection into the synovial space of B2A or saline and terminated at 21 days, after which knee cartilage damage was determined and scored by histological analysis. In murine C3H10T1/2 micromass culture, B2A induced the expression of more than 11 genes associated with growth factors/receptors, transcription, and the extracellular matrix, including PDGF-AA. B2A also significantly increased the sulfated glycosaminoglycan and collagen of murine- and human micromass cultures. In the knee osteoarthritis model, B2A treatment enhanced cartilage repair compared to untreated knees as determined histologically by a decrease in damage indicators. These findings suggest that B2A induces stem cells chondrogenic differentiation in vitro and enhances cartilage repair in vivo. The results suggest that B2A might be useful to promote cartilage repair.

Peculiarities of using stem cells for regeneration of the bone and cartilage tissue

Scientific literature about the use of MSC contains clinical and experimental data on the efficiency of cell technologies for restoration of the osteoarticular apparatus. The use of MSC immobilized in the appropriate carriers and differentiation of these cells towards the bone cells and chondrocytes are of crucial importance. However, the use of MSC, both individual and in combination with other preparations and substances has a number of drawbacks and advantages. The absence of published reports on contraindications and complications of cell therapy is worthy of note, because the analysis of unsuccessful application of MSC will help to determine the indication for this treatment, and hence, to improve the efficiency of cell technologies in the future. Wider use of MSC in clinical practice and experimental studies for acceleration of reparative processes in the bone and cartilage tissue seems to be promising.

Human mesenchymal stromal cell proteomics: contribution for identification of new markers and targets for medicine intervention

Mesenchymal stem or stromal cells (MSCs) have become of great interest for cell-based therapy owing to their roles in tissue repair and immune suppression. MSCs have the ability to differentiate into specialized tissues, including bone, cartilage and muscle, among several others. Furthermore, it has been found that MSCs can also serve as cellular factories that secrete mediators to stimulate in situ regeneration of injured tissues. Proteomics has contributed significantly to the identification of new proteins to improve cellular characterization of MSCs, to identify new targets for therapeutic intervention and to elucidate important pathways utilized by MSCs to differentiate into distinct tissues. As proteomics technology advances, several studies can be revisited and analyzed in depth, employing state-of-the-art approaches, helping to uncover the cellular mechanisms utilized by MSCs to exert their regenerative functionalities. In this article, we will review the progress made so far and discuss further opportunities for proteomics to contribute to the clinical applications of MSCs.

Comparative proteomic analysis of rat hepatic stellate cell activation: a comprehensive view and suppressed immune response

Elucidation of the molecular events underlying hepatic stellate cell (HSC) activation is an essential step toward understanding the biological properties of HSC and clarifying the potential roles of HSCs in liver fibrosis and other liver diseases, including hepatocellular carcinoma. High-throughput comparative proteomic analysis based on isobaric tags for relative and absolute quantitation (iTRAQ) labeling combined with online two-dimensional nanoscale liquid chromatography and tandem mass spectrometry (2D nano-LC-MS/MS) were performed on an in vitro HSC activation model to obtain a comprehensive view of the protein ensembles associated with HSC activation. In total, 2,417 proteins were confidently identified (false discovery rate <1%), of which 2,322 proteins were quantified. Compared with quiescent HSCs, 519 proteins showed significant differences in activated HSCs (≥ 3.0-fold). Bioinformatics analyses using Ingenuity Pathway Analysis revealed that the 319 up-regulated proteins represented multiple cellular functions closely associated with HSC activation, such as extracellular matrix synthesis and proliferation. In addition to the well-known markers for HSC activation, such as α-smooth muscle actin and collagen types 1 and 3, some novel proteins potentially associated with HSC activation were identified, while the 200 down-regulated proteins were primarily related to immune response and lipid metabolism. Most intriguingly, the top biological function, top network, and top canonical pathway of down-regulated proteins were all involved in immune responses. The expression and/or biological function of a set of proteins were properly validated, especially Bcl2-associated athanogene 2, BAG3, and B7H3.

CONCLUSION

The present study provided the most comprehensive proteome profile of rat HSCs and some novel insights into HSC activation, especially the suppressed immune response.

Comparative proteomic analysis of primary schwann cells and a spontaneously immortalized schwann cell line RSC 96: a comprehensive overview with a focus on cell adhesion and migration related proteins

Schwann cells (SCs) are the principal glial cells of the peripheral nervous system (PNS). As a result of tissue heterogeneity and difficulties in the isolation and culture of primary SCs, a considerable understanding of SC biology is obtained from SC lines. However, the differences between the primary SCs and SC lines remain uncertain. In the present study, quantitative proteomic analysis based on isobaric tags for relative and absolute quantitation (iTRAQ) labeling was conducted to obtain an unbiased view of the proteomic profiles of primary rat SCs and RSC96, a spontaneously immortalized rat SC line. Out of 1757 identified proteins (FDR < 1%), 1702 were quantified, while 61 and 78 were found to be, respectively, up- or down-regulated (90% confidence interval) in RSC96. Bioinformatics analysis indicated the unique features of spontaneous immortalization, illustrated the dedifferentiated state of RSC96, and highlighted a panel of novel proteins associated with cell adhesion and migration including CADM4, FERMT2, and MCAM. Selected proteomic data and the requirement of these novel proteins in SC adhesion and migration were properly validated. Taken together, our data collectively revealed proteome differences between primary SCs and RSC96, validated several differentially expressed proteins with potential biological significance, and generated a database that may serve as a useful resource for studies of SC biology and pathology.

Application for proteomic techniques in studying osteoarthritis: a review

After the genomic era, proteomic corresponds to a wide variety of techniques that study the protein content of cells, tissue, or organism and that allow the isolation of protein of interest. It offers the choice between gel-based and gel-free methods or shotgun proteomics. Applications of proteomic technology may concern three principal objectives in several biomedical or clinical domains of research as in osteoarthritis: (i) to understand the physiopathology or underlying mechanisms leading to a disease or associated with a particular model, (ii), to find disease-specific biomarker, and (iii) to identify new therapeutic targets. This review aimed at gathering most of the data regarding the proteomic techniques and their applications to osteoarthritis research. It also reported technical limitations and solutions, as for example for sample preparation. Proteomics open wide perspectives in biochemical research but many technical matters still remain to be solved.

Proteomic analysis of Col11a1-associated protein complexes

Cartilage plays an essential role during skeletal development within the growth plate and in articular joint function. Interactions between the collagen fibrils and other extracellular matrix molecules maintain structural integrity of cartilage, orchestrate complex dynamic events during embryonic development, and help to regulate fibrillogenesis. To increase our understanding of these events, affinity chromatography and liquid chromatography/tandem mass spectrometry were used to identify proteins that interact with the collagen fibril surface via the amino terminal domain of collagen α1(XI) a protein domain that is displayed at the surface of heterotypic collagen fibrils of cartilage. Proteins extracted from fetal bovine cartilage using homogenization in high ionic strength buffer were selected based on affinity for the amino terminal noncollagenous domain of collagen α1(XI). MS was used to determine the amino acid sequence of tryptic fragments for protein identification. Extracellular matrix molecules and cellular proteins that were identified as interacting with the amino terminal domain of collagen α1(XI) directly or indirectly, included proteoglycans, collagens, and matricellular molecules, some of which also play a role in fibrillogenesis, while others are known to function in the maintenance of tissue integrity. Characterization of these molecular interactions will provide a more thorough understanding of how the extracellular matrix molecules of cartilage interact and what role collagen XI plays in the process of fibrillogenesis and maintenance of tissue integrity. Such information will aid tissue engineering and cartilage regeneration efforts to treat cartilage tissue damage and degeneration.

Chondrogenesis and cartilage tissue engineering: the longer road to technology development

Joint injury and disease are painful and debilitating conditions affecting a substantial proportion of the population. The idea that damaged cartilage in articulating joints might be replaced seamlessly with tissue-engineered cartilage is of obvious commercial interest because the market for such treatments is large. Recently, a wealth of new information about the complex biology of chondrogenesis and cartilage has emerged from stem cell research, including increasing evidence of the role of physical stimuli in directing differentiation. The challenge for the next generation of tissue engineers is to identify the key elements in this new body of knowledge that can be applied to overcome current limitations affecting cartilage synthesis in vitro. Here we review the status of cartilage tissue engineering and examine the contribution of stem cell research to technology development for cartilage production.

The requirement for proteomics to unravel stem cell regulatory mechanisms

Stem cells are defined by their ability to self-renew and to differentiate, the processes whereby these events are achieved is the subject of much investigation. These studies include cancer stem cell populations, where eradication of this specific population is the ultimate goal of treatment. Whilst cellular signalling events and transcription factor complex-mediated changes in gene expression have been analysed in some detail within stem cells, full systematic understanding of the events promoting self-renewal or the commitment process leading to formation of a specific cell type require a systems biology approach. This in turn demands a need for proteomic analysis of post-translational regulation of protein levels, protein interactions, protein post-translational modification (e.g. ubiquitination, methylation, acetylation, phosphorylation) to identify networks for stem cell regulation. Furthermore, the phenomenon of induced pluripotency via cellular reprogramming also can be understood optimally using combined molecular biology and proteomics approaches; here we describe current research employing proteomics and mass spectrometry to dissect stem cell regulatory mechanisms.

Cucurbitacin B induces rapid depletion of the G-actin pool through reactive oxygen species-dependent actin aggregation in melanoma cells

Cucurbitacin B (CuB), a triterpenoid compound isolated from Cucurbitaceae plants, has been reported as a promising anti-cancer agent, yet its action mechanism is still controversial. In this study, we explored the potential mechanism of CuB in murine B16F10 melanoma cells. Anti-proliferation and anti-invasion effects were assessed in cultured cells, and in vivo anti-tumor activity was evaluated in a murine subcutaneous melanoma model. Flow cytometry was adopted to analyze cell cycle distribution and reactive oxygen species (ROS) levels. Actin levels were determined by western blot analysis, and the profiles of differential expressed proteins were identified by a quantitative proteomic approach. The results showed that CuB exerted inhibitory effects on cell proliferation, colony formation, as well as migration and invasion potential of the melanoma cells. The growth of subcutaneous melanoma was significantly inhibited in mice treated with CuB when compared with control group. Furthermore, CuB treatment caused rapid cell membrane blebbing and deformation, and induced G(2)/M-phase arrest and formation of multiploid cells. Notably, the G-actin pool was rapidly depleted and actin aggregates were formed quickly after CuB treatment. A number of cytoskeleton-regulatory proteins were differentially regulated. Blockage of ROS production significantly reduced the G-actin depletion ability and the anti-tumor activity of CuB. These findings indicate that CuB induces rapid depletion of the G-actin pool through ROS-dependent actin aggregation in melanoma cells, which may at least partly account for its anti-tumor activity.

Valproic acid synergistically enhances the cytotoxicity of gossypol in DU145 prostate cancer cells: an iTRTAQ-based quantitative proteomic analysis

Gossypol (GOS), a BH3 mimetic, has been investigated as a sensitizing co-therapy to radiation and chemotherapy in treatment of metastatic prostate cancer. In this study, we found that valproic acid (VPA), a histone deacetylase inhibitor (HDACI), counteracted the suppressive effect of GOS on histone H3 acetylation and enhanced the cytotoxicity of GOS to DU145 prostate cancer cells. Significant synergistic effects were observed in combined GOS and VPA treatment, culminating in more DNA damage and cell death. The iTRAQ-based quantitative proteomic analysis revealed differential proteomic profiles in cells treated with VPA, GOS or their combination. In GOS-treated cells, oxidative phosphorylation-related proteins were depressed and endoplasmic reticulum stress markers were upregulated. In the presence of VPA, the GOS-induced mitochondrial stress was further enhanced since glycolysis- and hypoxia-associated proteins were upregulated, suggesting a disruption of energy metabolism in these cells. Furthermore, the DNA damage repair ability of cells co-treated with GOS and VPA was also decreased, as evidenced by the downregulation of DNA damage repair proteins and the enhancement of DNA fragmentation and cell death. These findings suggest that GOS in combination with an HDACI has the potential to increase its clinical efficacy in the treatment of prostate cancer.