Latent TGF-beta binding proteins (LTBPs)-1 and -3 coordinate proliferation and osteogenic differentiation of human mesenchymal stem cells

Expanded phenotypes and pathogenesis of geleophysic dysplasia 3 resulted from a de novo LTBP3 mutation: A case report

RATIONALE

The aim of this study is to investigate the de novo mutation and clinical features of latent transforming growth factor-beta-binding protein 3 (LTBP3) gene-associated geleophysic dysplasia 3, and possible mechanisms of action.

PATIENT CONCERNS

A nonconsanguineous couple was recruited for this study due to the presence of intrauterine growth restriction. The pregnant woman and her elder daughter presented with skeletal abnormalities with diabetes. The pregnant woman underwent amniocentesis for cytogenetic analysis and copy number variation sequencing. Furthermore, we employed a combination of pedigree whole exome sequencing and bioinformatics analysis to predict the effects of mutations.

DIAGNOSES

The results of karyotyping and copy number variation sequencing were normal. And the whole exome sequencing results indicated that the family carried a de novo mutation c.852_853insAGG (p.L284_P285insR) in the LTBP3 gene (NM_001130144.3) inherited from the mother. The results of bioinformatics prediction demonstrated the mutation influenced the stability of the LTBP3 gene, thereby enhanced the transforming growth factor β signaling pathways.

INTERVENTIONS

The couple terminated the pregnancy after comprehensive consideration.

OUTCOMES

A de novo non-frameshift mutation of the LTBP3 gene might enhance the transforming growth factor β signaling pathways, thereby leading to geleophysic dysplasia 3.

LESSONS

As a rare multi-system musculoskeletal disorder, geleophysic dysplasia 3 necessitates early prenatal diagnosis and multidisciplinary consultation in order to facilitate further diagnosis and evaluation of the patient and the fetus.

A Proteomic Approach to Determine Stem Cell Skeletal Differentiation Signature on Additive Manufactured Scaffolds

Understanding how porous biomaterials interact with cells at their surface and how they either promote or inhibit cellular processes has presented several challenges. Additive manufacturing enables the fabrication of scaffolds with distinct compositions and designs for different tissue engineering applications. To evaluate the in vitro performance of multiple printed materials, biochemical assays can be limiting in providing valuable insight and key information to select the best tissue destination. Omics technologies like proteomics are crucial for studying important cellular events and gathering valuable information about cellular processes and mechanisms. However, only few studies focus on proteomics to decipher cell-material interactions and cell differentiation on additive manufactured scaffolds. Here, scaffolds were fabricated using three polymers (polycaprolactone (PCL), poly(ethylene oxide)-poly(butylene terephthalate) (PEOT/PBT), and polylactic acid (PLA)) through additive manufacturing. Their chondrogenic and osteogenic potential were characterized and compared using human bone marrow-derived mesenchymal stem cells (hBMSCs) through proteomics analysis. The 3D scaffolds were all hydrophilic and displayed Young's moduli close to those of bone or cartilage for PLA and PCL and PEOT/PBT, respectively. Biochemical assays indicated that PEOT/PBT and PLA scaffolds have a greater chondrogenic potential by higher glycosaminoglycan (GAG) and collagen deposition compared to PCL. PLA and PEOT/PBT showed to be more effective in promoting bone formation, as evidenced by higher calcium deposits detected by alizarin red staining, and higher alkaline phosphatase (ALP), especially for PLA in osteogenic medium. Proteomics data revealed the most distinct separation between conditions in chondrogenic medium, which had the highest protein identification rates. Pathway analysis showed that PCL did not induce any differentiation-related pathways when compared to PEOT/PBT and PLA in any of the tested media conditions. Analysis of PEOT/PBT proteins showed pathways involved in chondrogenesis in all three media and pathways related to hypertrophic phenotype progression in chondrogenic medium. These data suggests that PEOT/PBT is a valuable candidate for cartilage and osteochondral applications, able to drive hBMSCs differentiation without the need of growth factors. PLA was also a valuable candidate for cartilage and bone applications by upregulating both chondrogenic and osteogenic-related proteins in maintenance and chondrogenic media. In osteogenic and maintenance media, the upregulation of angiogenic proteins makes PLA a better candidate for bone application where vascularization is key.

The roles and regulatory mechanisms of TGF-β and BMP signaling in bone and cartilage development, homeostasis and disease

Transforming growth factor-βs (TGF-βs) and bone morphometric proteins (BMPs) belong to the TGF-β superfamily and perform essential functions during osteoblast and chondrocyte lineage commitment and differentiation, skeletal development, and homeostasis. TGF-βs and BMPs transduce signals through SMAD-dependent and -independent pathways; specifically, they recruit different receptor heterotetramers and R-Smad complexes, resulting in unique biological readouts. BMPs promote osteogenesis, osteoclastogenesis, and chondrogenesis at all differentiation stages, while TGF-βs play different roles in a stage-dependent manner. BMPs and TGF-β have opposite functions in articular cartilage homeostasis. Moreover, TGF-β has a specific role in maintaining the osteocyte network. The precise activation of BMP and TGF-β signaling requires regulatory machinery at multiple levels, including latency control in the matrix, extracellular antagonists, ubiquitination and phosphorylation in the cytoplasm, nucleus-cytoplasm transportation, and transcriptional co-regulation in the nuclei. This review weaves the background information with the latest advances in the signaling facilitated by TGF-βs and BMPs, and the advanced understanding of their diverse physiological functions and regulations. This review also summarizes the human diseases and mouse models associated with disordered TGF-β and BMP signaling. A more precise understanding of the BMP and TGF-β signaling could facilitate the development of bona fide clinical applications in treating bone and cartilage disorders.

Multi-organ phenotypes in mice lacking latent TGFβ binding protein 2 (LTBP2)

BACKGROUND

Latent TGFβ binding protein-2 (LTBP2) is a fibrillin 1 binding component of the microfibril. LTBP2 is the only LTBP protein that does not bind any isoforms of TGFβ, although it may interfere with the function of other LTBPs or interact with other signaling pathways.

RESULTS

Here, we investigate mice lacking Ltbp2 (Ltbp2-/- ) and identify multiple phenotypes that impact bodyweight and fat mass, and affect bone and skin development. The alterations in skin and bone development are particularly noteworthy since the strength of these tissues is differentially affected by loss of Ltbp2. Interestingly, some tissues that express high levels of Ltbp2, such as the aorta and lung, do not have a developmental or homeostatic phenotype.

CONCLUSIONS

Analysis of these mice show that LTBP2 has complex effects on development through direct effects on the extracellular matrix (ECM) or on signaling pathways that are known to regulate the ECM.

Efficient Treatment of Pulpitis via Transplantation of Human Pluripotent Stem Cell-Derived Pericytes Partially through LTBP1-Mediated T Cell Suppression

Dental pulp pericytes are reported to have the capacity to generate odontoblasts and express multiple cytokines and chemokines that regulate the local immune microenvironment, thus participating in the repair of dental pulp injury in vivo. However, it has not yet been reported whether the transplantation of exogenous pericytes can effectively treat pulpitis, and the underlying molecular mechanism remains unknown. In this study, using a lineage-tracing mouse model, we showed that most dental pulp pericytes are derived from cranial neural crest. Then, we demonstrated that the ablation of pericytes could induce a pulpitis-like phenotype in uninfected dental pulp in mice, and we showed that the significant loss of pericytes occurs during pupal inflammation, implying that the transplantation of pericytes may help to restore dental pulp homeostasis during pulpitis. Subsequently, we successfully generated pericytes with immunomodulatory activity from human pluripotent stem cells through the intermediate stage of the cranial neural crest with a high level of efficiency. Most strikingly, for the first time we showed that, compared with the untreated pulpitis group, the transplantation of hPSC-derived pericytes could substantially inhibit vascular permeability (the extravascular deposition of fibrinogen, ** p < 0.01), alleviate pulpal inflammation (TCR+ cell infiltration, * p < 0.05), and promote the regeneration of dentin (** p < 0.01) in the mouse model of pulpitis. In addition, we discovered that the knockdown of latent transforming growth factor beta binding protein 1 (LTBP1) remarkably suppressed the immunoregulation ability of pericytes in vitro and compromised their in vivo regenerative potential in pulpitis. These results indicate that the transplantation of pericytes could efficiently rescue the aberrant phenotype of pulpal inflammation, which may be partially due to LTBP1-mediated T cell suppression.

Dupuytren's Disease Is Mediated by Insufficient TGF-β1 Release and Degradation

Dupuytren's disease (DD) is a fibroproliferative disorder affecting the palmar fascia, causing functional restrictions of the hand and thereby limiting patients' daily lives. The disturbed and excessive myofibroblastogenesis, causing DD, is mainly induced by transforming growth factor (TGF)-β1. But, the extent to which impaired TGF-β1 release or TGF-β signal degradation is involved in pathologically altered myofibroblastogenesis in DD has been barely examined. Therefore, the complex in which TGF-β1 is secreted in the extracellular matrix to elicit its biological activity, and proteins such as plasmin, integrins, and matrix metalloproteinases (MMPs), which are involved in the TGF-β1 activation, were herein analyzed in DD-fibroblasts (DD-FBs). Additionally, TGF-β signal degradation via caveolin-1 was examined with 5-fluoruracil (5-FU) in detail. Gene expression analysis was performed via Western blot, PCR, and immunofluorescence analyses. As a surrogate parameter for disturbed myofibroblastogenesis, 𝛼-smooth-muscle-actin (𝛼-SMA) expression was evaluated. It was demonstrated that latency-associated peptide (LAP)-TGF-β and latent TGF-β-binding protein (LTBP)-1 involved in TGF-β-complex building were significantly upregulated in DD. Plasmin a serinprotease responsible for the TGF-β release was significantly downregulated. The application of exogenous plasmin was able to inhibit disturbed myofibroblastogenesis, as measured via 𝛼-SMA expression. Furthermore, a reduced TGF-β1 degradation was also involved in the pathological phenotype of DD, because caveolin-1 expression was significantly downregulated, and if rescued, myofibroblastogenesis was also inhibited. Therefore, our study demonstrates that a deficient release and degradation of TGF-β1 are important players in the pathological phenotype of DD and should be addressed in future research studies to improve DD therapy or other related fibrotic conditions.

Long-term in vivo survival of 3D-bioprinted human lipoaspirate-derived adipose tissue: proteomic signature and cellular content

Three-dimensional (3D)-bioprinted lipoaspirate-derived adipose tissue (LAT) is a potential alternative to lipo-injection for correcting soft-tissue defects. This study investigated the long-term in vivo survival of 3D-bioprinted LAT and its proteomic signature and cellular composition. We performed proteomic and multicolour flow cytometric analyses on the lipoaspirate and 3D-bioprinted LAT constructs were transplanted into nude mice, followed by explantation after up to 150 days. LAT contained adipose-tissue-derived stem cells (ASCs), pericytes, endothelial progenitor cells (EPCs) and endothelial cells. Proteomic analysis identified 6,067 proteins, including pericyte markers, adipokines, ASC secretome proteins, proangiogenic proteins and proteins involved in adipocyte differentiation and developmental morphogenic signalling, as well as proteins not previously described in human subcutaneous fat. 3D-bioprinted LAT survived for 150 days in vivo with preservation of the construct shape and size. Furthermore, we identified human blood vessels after 30 and 150 days in vivo, indicating angiogenesis from capillaries. These results showed that LAT has a favourable proteomic signature, contains ASCs, EPCs and blood vessels that survive 3D bioprinting and can potentially facilitate angiogenesis and successful autologous fat grafting in soft-tissue reconstruction.

SOX4 Mediates ATRA-Induced Differentiation in Neuroblastoma Cells

Neuroblastoma (NB), which is considered to be caused by the differentiation failure of neural crest cells, is the most common extracranial malignant solid tumor in children. The degree of tumor differentiation in patients with NB is closely correlated with the survival rate. To explore the potential targets that mediate NB cell differentiation, we analyzed four microarray datasets from GEO, and the overlapping down- or upregulated DEGs were displayed using Venn diagrams. SOX4 was one of the overlapping upregulated DEGs and was confirmed by RT-qPCR and Western blot in ATRA-treated NGP, SY5Y, and BE2 cells. To clarify whether SOX4 was the target gene regulating NB cell differentiation, the correlation between the expression of SOX4 and the survival of clinical patients was analyzed via the R2 database, SOX4 overexpression plasmids and siRNAs were generated to change the expression of SOX4, RT-qPCR and Western blot were performed to detect SOX4 expression, cell confluence or cell survival was detected by IncuCyte Zoom or CCK8 assay, immunocytochemistry staining was performed to detect cells' neurites, and a cell cycle analysis was implemented using Flow cytometry after PI staining. The results showed that the survival probabilities were positively correlated with SOX4 expression, in which overexpressing SOX4 inhibited NB cell proliferation, elongated the cells' neurite, and blocked the cell cycle in G1 phase, and that knockdown of the expression of SOX4 partially reversed the ATRA-induced inhibition of NB cell proliferation, the elongation of the cells' neurites, and the blocking of the cell cycle in the G1 phase. These indicate that SOX4 may be a target to induce NB cell differentiation.

Latent Transforming Growth Factor β Binding Protein 3 Controls Adipogenesis

Transforming growth factor-beta (TGFβ) is released from cells as part of a trimeric latent complex consisting of TGFβ, the TGFβ propeptides, and either a latent TGFβ binding protein (LTBP) or glycoprotein-A repetitions predominant (GARP) protein. LTBP1 and 3 modulate latent TGFβ function with respect to secretion, matrix localization, and activation and, therefore, are vital for the proper function of the cytokine in a number of tissues. TGFβ modulates stem cell differentiation into adipocytes (adipogenesis), but the potential role of LTBPs in this process has not been studied. We observed that 72 h post adipogenesis initiation Ltbp1, 2, and 4 expression levels decrease by 74-84%, whereas Ltbp3 expression levels remain constant during adipogenesis. We found that LTBP3 silencing in C3H/10T1/2 cells reduced adipogenesis, as measured by the percentage of cells with lipid vesicles and the expression of the transcription factor peroxisome proliferator-activated receptor gamma (PPARγ). Lentiviral mediated expression of an Ltbp3 mRNA resistant to siRNA targeting rescued the phenotype, validating siRNA specificity. Knockdown (KD) of Ltbp3 expression in 3T3-L1, M2, and primary bone marrow stromal cells (BMSC) indicated a similar requirement for Ltbp3. Epididymal and inguinal white adipose tissue fat pad weights of Ltbp3^-/- mice were reduced by 62% and 57%, respectively, compared to wild-type mice. Inhibition of adipogenic differentiation upon LTBP3 loss is mediated by TGFβ, as TGFβ neutralizing antibody and TGFβ receptor I kinase blockade rescue the LTBP3 KD phenotype. These results indicate that LTBP3 has a TGFβ-dependent function in adipogenesis both in vitro and possibly in vivo.

PTHrP promotes subchondral bone formation in TMJ-OA

PTH-related peptide (PTHrP) improves the bone marrow micro-environment to activate the bone-remodelling, but the coordinated regulation of PTHrP and transforming growth factor-β (TGFβ) signalling in TMJ-OA remains incompletely understood. We used disordered occlusion to establish model animals that recapitulate the ordinary clinical aetiology of TMJ-OA. Immunohistochemical and histological analyses revealed condylar fibrocartilage degeneration in model animals following disordered occlusion. TMJ-OA model animals administered intermittent PTHrP (iPTH) exhibited significantly decreased condylar cartilage degeneration. Micro-CT, histomorphometry, and Western Blot analyses disclosed that iPTH promoted subchondral bone formation in the TMJ-OA model animals. In addition, iPTH increased the number of osterix (OSX)-positive cells and osteocalcin (OCN)-positive cells in the subchondral bone marrow cavity. However, the number of osteoclasts was also increased by iPTH, indicating that subchondral bone volume increase was mainly due to the iPTH-mediated increase in the bone-formation ability of condylar subchondral bone. In vitro, PTHrP treatment increased condylar subchondral bone marrow-derived mesenchymal stem cell (SMSC) osteoblastic differentiation potential and upregulated the gene and protein expression of key regulators of osteogenesis. Furthermore, we found that PTHrP-PTH1R signalling inhibits TGFβ signalling during osteoblastic differentiation. Collectively, these data suggested that iPTH improves OA lesions by enhancing osteoblastic differentiation in subchondral bone and suppressing aberrant active TGFβ signalling. These findings indicated that PTHrP, which targets the TGFβ signalling pathway, may be an effective biological reagent to prevent and treat TMJ-OA in the clinic.

Disruption of LTBP4 Inhibition-Induced TGFβ1 Activation Promoted Cell Proliferation and Metastasis in Skin Melanoma by Inhibiting the Activation of the Hippo-YAP1 Signaling Pathway

Melanoma is a malignant tumor derived from melanocytes, which is the most fatal skin cancer. The present study aimed to explore and elucidate the candidate genes in melanoma and its underlying molecular mechanism. A total of 1,156 differentially expressed genes were obtained from the GSE46517 dataset of Gene Expression Omnibus database using the package “limma” in R. Based on two algorithms (LASSO and SVM-RFE), we obtained three candidate DEGs (LTBP4, CDHR1, and MARCKSL1). Among them, LTBP4 was identified as a diagnostic marker of melanoma (AUC = 0.985). Down-regulation of LTBP4 expression was identified in melanoma tissues and cells, which predicted poor prognosis of patients with melanoma. Cox analysis results discovered that LTBP4 with low expression was an independent prognostic factor for overall survival in patients with melanoma. LTBP4 inhibition reduced cell apoptosis and promoted cell proliferation and metastasis. These changes were correlated with the expression levels of caspase-3, Ki67 and E-cadherin. Further, as indicated by tumor formation study of nude mice, LTBP4 silencing improved the tumorigenic ability of melanoma cells. Knockdown of LTBP4 increased the percentage of active TGFβ1 secreted by melanoma cells. CTGF, Gyr61, and Birc5 expression levels were reduced, YAP1 phosphorylation was inhibited, and YAP1 was translocated from the cytoplasm to the nucleus in melanoma cells treated with TGF-β1. These effects were reversed by LTBP4 overexpression. As evidenced by immunofluorescent staining, Western blotting and luciferase reporter assay, LTBP4 overexpression activated the Hippo signaling pathway, which was characterized by the increased nuclear-cytoplasmic translocation of YAP1 and the enhanced phosphorylation of YAP1, MST1, and MOB1. In addition, the effects of LTBP4 overexpression on inhibiting CTGF, Cyr61 and Birc5 expression, promoting the apoptosis, and inhibiting the metastasis and proliferation of melanoma cells were reversed by the overexpression of YAP1 or MST1. In conclusion, the LTBP4-TGFβ1-Hippo-YAP1 axis is a critical pathway for the progression of skin melanoma.

LTBP3 Frameshift Variant in British Shorthair Cats with Complex Skeletal Dysplasia

We investigated a highly inbred family of British Shorthair cats in which two offspring were affected by deteriorating paraparesis due to complex skeletal malformations. Radiographs of both affected kittens revealed vertebral deformations with marked stenosis of the vertebral canal from T11 to L3. Additionally, compression of the spinal cord, cerebellar herniation, coprostasis and hypogangliosis were found. The pedigree suggested monogenic autosomal recessive inheritance of the trait. We sequenced the genome of an affected kitten and compared the data to 62 control genomes. This search yielded 55 private protein-changing variants of which only one was located in a likely functional candidate gene, LTBP3, encoding latent transforming growth factor β binding protein 3. This variant, c.158delG or p.(Gly53Alafs*16), represents a 1 bp frameshift deletion predicted to truncate 95% of the open reading frame. LTBP3 is a known key regulator of transforming growth factor β (TGF-β) and is involved in bone morphogenesis and remodeling. Genotypes at the LTBP3:c.158delG variant perfectly co-segregated with the phenotype in the investigated family. The available experimental data together with current knowledge on LTBP3 variants and their functional impact in human patients and mice suggest LTBP3:c.158delG as a candidate causative variant for the observed skeletal malformations in British Shorthair cats. To the best of our knowledge, this study represents the first report of LTBP3-related complex skeletal dysplasia in domestic animals.

GARP is a key molecule for mesenchymal stromal cell responses to TGF-β and fundamental to control mitochondrial ROS levels

Multipotent mesenchymal stromal cells (MSCs) have emerged as a promising cell therapy in regenerative medicine and for autoimmune/inflammatory diseases. However, a main hurdle for MSCs-based therapies is the loss of their proliferative potential in vitro. Here we report that glycoprotein A repetitions predominant (GARP) is required for the proliferation and survival of adipose-derived MSCs (ASCs) via its regulation of transforming growth factor-β (TGF-β) activation. Silencing of GARP in human ASCs increased their activation of TGF-β which augmented the levels of mitochondrial reactive oxygen species (mtROS), resulting in DNA damage, a block in proliferation and apoptosis. Inhibition of TGF-β signaling reduced the levels of mtROS and DNA damage and restored the ability of GARP-/low ASCs to proliferate. In contrast, overexpression of GARP in ASCs increased their proliferative capacity and rendered them more resistant to etoposide-induced DNA damage and apoptosis, in a TGF-β-dependent manner. In summary, our data show that the presence or absence of GARP on ASCs gives rise to distinct TGF-β responses with diametrically opposing effects on ASC proliferation and survival.

TGF-ß1 Induces Changes in the Energy Metabolism of White Adipose Tissue-Derived Human Adult Mesenchymal Stem/Stromal Cells In Vitro

Adipose tissue plays an active role in the regulation of the body’s energy balance. Mesenchymal stem/stromal cells from adipose tissue (adMSC) are the precursor cells for repair and adipogenesis. Since the balance of the differentiation state of adipose tissue-resident cells is associated with the development of various diseases, the examination of the regulation of proliferation and differentiation of adMSC might provide new therapeutic targets. Transforming growth factor-β1 (TGF-ß1) is synthetized by many cell types and is involved in various biological processes. Here, we investigated the effects of different concentrations of TGF-ß1 (1–10 ng/mL) on adMSC proliferation, metabolic activity, and analyzed the gene expression data obtained from DNA microarrays by bioinformatics. TGF-ß1 induced the concentration- and time-dependent increase in the cell number of adMSC with simultaneously unchanged cell cycle distributions. The basal oxygen consumption rates did not change significantly after TGF-ß1 exposure. However, glycolytic activity was significantly increased. The gene expression analysis identified 3275 differentially expressed genes upon exposure to TGF-ß1. According to the pathway enrichment analyses, they also included genes associated with energy metabolism. Thus, it was shown that TGF-ß1 induces changes in the energy metabolism of adMSC. Whether these effects are of relevance in vivo and whether they contribute to pathogenesis should be addressed in further examinations.

MicroRNA-323-3p promotes myogenesis by targeting Smad2

Skeletal muscle is an important and complex organ with multiple biological functions in humans and animals. Proliferation and differentiation of myoblasts are the key steps during the development of skeletal muscle. MicroRNA (miRNA) is a class of 21-nucleotide noncoding RNAs regulating gene expression by combining with the 3'-untranslated region of target messenger RNA. Many studies in recent years have suggested that miRNAs play a critical role in myogenesis. Through high-throughput sequencing, we found that miR-323-3p showed significant changes in the longissimus dorsi muscle of Rongchang pigs in different age groups. In this study, we discovered that overexpression of miR-323-3p repressed myoblast proliferation and promoted differentiation, whereas the inhibitor of miR-323-3p displayed the opposite results. Furthermore, we predicted Smad2 as the target gene of miR-323-3p and found that miR-323-3p directly modulated the expression level of Smad2. Then luciferase reporter assays verified that Smad2 was a target gene of miR-323-3p during the differentiation of myoblasts. These findings reveal that miR-323-3p is a positive regulator of myogenesis by targeting Smad2. This provides a novel mechanism of miRNAs in myogenesis.

Identification of new therapeutic targets for osteoarthritis through genome-wide analyses of UK Biobank data

Osteoarthritis is the most common musculoskeletal disease and the leading cause of disability globally. Here, we perform a genome-wide association study for osteoarthritis (77,052 cases and 378,169 controls), analysing 4 phenotypes: knee osteoarthritis, hip osteoarthritis, knee and/or hip osteoarthritis, and any osteoarthritis. We discover 64 signals, 52 of them novel, more than doubling the number of established disease loci. Six signals fine map to a single variant. We identify putative effector genes by integrating eQTL colocalization, fine-mapping, human rare disease, animal model, and osteoarthritis tissue expression data. We find enrichment for genes underlying monogenic forms of bone development diseases, and for the collagen formation and extracellular matrix organisation biological pathways. Ten of the likely effector genes, including TGFB1, FGF18, CTSK and IL11 have therapeutics approved or in clinical trials, with mechanisms of action supportive of evaluation for efficacy in osteoarthritis.

TGF-β and mesenchymal stromal cells in regenerative medicine, autoimmunity and cancer

Multipotent mesenchymal stromal cells (MSCs) represent a promising cell-based therapy in regenerative medicine and for the treatment of inflammatory/autoimmune diseases. Importantly, MSCs have emerged as an important contributor to the tumor stroma with both pro- and anti-tumorigenic effects. However, the successful translation of MSCs to the clinic and the prevention of their tumorigenic and metastatic effect require a greater understanding of factors controlling their proliferation, differentiation, migration and immunomodulation in vitro and in vivo. The transforming growth factor(TGF)-β1, 2 and 3 are involved in almost every aspect of MSC function. The aim of this review is to highlight the roles that TGF-β play in the biology and therapeutic applications of MSCs. We will discuss the how TGF-β modulate MSC function as well as the paracrine effects of MSC-derived TGF-β on other cell types in the context of tissue regeneration, immune responses and cancer. Finally, taking all these aspects into consideration we discuss how modulation of TGF-β signaling/production in MSCs could be of clinical interest.

Mapping genetic variants for cranial vault shape in humans

The shape of the cranial vault, a region comprising interlocking flat bones surrounding the cerebral cortex, varies considerably in humans. Strongly influenced by brain size and shape, cranial vault morphology has both clinical and evolutionary relevance. However, little is known about the genetic basis of normal vault shape in humans. We performed a genome-wide association study (GWAS) on three vault measures (maximum cranial width [MCW], maximum cranial length [MCL], and cephalic index [CI]) in a sample of 4419 healthy individuals of European ancestry. All measures were adjusted by sex, age, and body size, then tested for association with genetic variants spanning the genome. GWAS results for the two cohorts were combined via meta-analysis. Significant associations were observed at two loci: 15p11.2 (lead SNP rs2924767, p = 2.107 × 10⁻⁸) for MCW and 17q11.2 (lead SNP rs72841279, p = 5.29 × 10⁻⁹) for MCL. Additionally, 32 suggestive loci (p < 5x10^-6) were observed. Several candidate genes were located in these loci, such as NLK, MEF2A, SOX9 and SOX11. Genome-wide linkage analysis of cranial vault shape in mice (N = 433) was performed to follow-up the associated candidate loci identified in the human GWAS. Two loci, 17q11.2 (c11.loc44 in mice) and 17q25.1 (c11.loc74 in mice), associated with cranial vault size in humans, were also linked with cranial vault size in mice (LOD scores: 3.37 and 3.79 respectively). These results provide further insight into genetic pathways and mechanisms underlying normal variation in human craniofacial morphology.

LTBPs in biology and medicine: LTBP diseases

The latent transforming growth factor (TGF) β binding proteins (LTBP) are crucial mediators of TGFβ function, as they control growth factor secretion, matrix deposition, presentation and activation. Deficiencies in specific LTBP isoforms yield discrete phenotypes representing defects in bone, lung and cardiovascular development mediated by loss of TGFβ signaling. Additional phenotypes represent loss of unique TGFβ-independent features of LTBP effects on elastogenesis and microfibril assembly. Thus, the LTBPs act as sensors for the regulation of both growth factor activity and matrix function.

Proteomic Alterations Associated with Biomechanical Dysfunction are Early Processes in the Emilin1 Deficient Mouse Model of Aortic Valve Disease

Aortic valve (AV) disease involves stiffening of the AV cusp with progression characterized by inflammation, fibrosis, and calcification. Here, we examine the relationship between biomechanical valve function and proteomic changes before and after the development of AV pathology in the Emilin1-/- mouse model of latent AV disease. Biomechanical studies were performed to quantify tissue stiffness at the macro (micropipette) and micro (atomic force microscopy (AFM)) levels. Micropipette studies showed that the Emilin1-/- AV annulus and cusp regions demonstrated increased stiffness only after the onset of AV disease. AFM studies showed that the Emilin1-/- cusp stiffens before the onset of AV disease and worsens with the onset of disease. Proteomes from AV cusps were investigated to identify protein functions, pathways, and interaction network alterations that occur with age- and genotype-related valve stiffening. Protein alterations due to Emilin1 deficiency, including changes in pathways and functions, preceded biomechanical aberrations, resulting in marked depletion of extracellular matrix (ECM) proteins interacting with TGFB1, including latent transforming growth factor beta 3 (LTBP3), fibulin 5 (FBLN5), and cartilage intermediate layer protein 1 (CILP1). This study identifies proteomic dysregulation is associated with biomechanical dysfunction as early pathogenic processes in the Emilin1-/- model of AV disease.

Proteomics-based network analysis characterizes biological processes and pathways activated by preconditioned mesenchymal stem cells in cardiac repair mechanisms

BACKGROUND

We have demonstrated that intramyocardial delivery of human mesenchymal stem cells preconditioned with a hyaluronan mixed ester of butyric and retinoic acid (MSCp⁺) is more effective in preventing the decay of regional myocardial contractility in a swine model of myocardial infarction (MI). However, the understanding of the role of MSCp⁺ in proteomic remodeling of cardiac infarcted tissue is not complete. We therefore sought to perform a comprehensive analysis of the proteome of infarct remote (RZ) and border zone (BZ) of pigs treated with MSCp⁺ or unconditioned stem cells.

METHODS

Heart tissues were analyzed by MudPIT and differentially expressed proteins were selected by a label-free approach based on spectral counting. Protein profiles were evaluated by using PPI networks and their topological analysis.

RESULTS

The proteomic remodeling was largely prevented in MSCp⁺ group. Extracellular proteins involved in fibrosis were down-regulated, while energetic pathways were globally up-regulated. Cardioprotectant pathways involved in the production of keto acid metabolites were also activated. Additionally, we found that new hub proteins support the cardioprotective phenotype characterizing the left ventricular BZ treated with MSCp⁺. In fact, the up-regulation of angiogenic proteins NCL and RAC1 can be explained by the increase of capillary density induced by MSCp⁺.

CONCLUSIONS

Our results show that angiogenic pathways appear to be uniquely positioned to integrate signaling with energetic pathways involving cardiac repair.

GENERAL SIGNIFICANCE

Our findings prompt the use of proteomics-based network analysis to optimize new approaches preventing the post-ischemic proteomic remodeling that may underlie the limited self-repair ability of adult heart.

External factors influencing mesenchymal stem cell fate in vitro

Mesenchymal stem cells (MSCs) have extensive potentials, which make them attractive candidates for the developmental biology, drug discovery and regenerative medicine. However, the use of MSCs is limited by their scarceness in tissues and in culture conditions. They also exhibit various degrees of potency which subsequently influencing their applications. Nowadays, questions remain about how self-renewal and differentiation of MSCs can be controlled in vitro and in vivo, how they will behave and migrate to the right place and how they modulate the immune system. Therefore, identification of factors and culture conditions to affect the fate and function of MSCs may be effective to enhance their applications in clinical situations. Studies have indicated that the fate of MSCs in culture is influenced by various external factors, including the specific cell source, donor age, plating density, passage number and plastic surface quality. Some other factors such as cell culture media and their supplementary factors, O₂ concentration, mechano-/electro-stimuli and three-dimensional scaffolds are also shown to be influential. This review addresses the current state of MSC research for describing and discussing the findings about external factors that influence the fate and function of MSCs. Additionally, the new discoveries and suggestions regarding their molecular mechanisms will be explained.

TGF-β and BMP signaling in osteoblast, skeletal development, and bone formation, homeostasis and disease

Transforming growth factor-beta (TGF-β) and bone morphogenic protein (BMP) signaling has fundamental roles in both embryonic skeletal development and postnatal bone homeostasis. TGF-βs and BMPs, acting on a tetrameric receptor complex, transduce signals to both the canonical Smad-dependent signaling pathway (that is, TGF-β/BMP ligands, receptors, and Smads) and the non-canonical-Smad-independent signaling pathway (that is, p38 mitogen-activated protein kinase/p38 MAPK) to regulate mesenchymal stem cell differentiation during skeletal development, bone formation and bone homeostasis. Both the Smad and p38 MAPK signaling pathways converge at transcription factors, for example, Runx2 to promote osteoblast differentiation and chondrocyte differentiation from mesenchymal precursor cells. TGF-β and BMP signaling is controlled by multiple factors, including the ubiquitin–proteasome system, epigenetic factors, and microRNA. Dysregulated TGF-β and BMP signaling result in a number of bone disorders in humans. Knockout or mutation of TGF-β and BMP signaling-related genes in mice leads to bone abnormalities of varying severity, which enable a better understanding of TGF-β/BMP signaling in bone and the signaling networks underlying osteoblast differentiation and bone formation. There is also crosstalk between TGF-β/BMP signaling and several critical cytokines’ signaling pathways (for example, Wnt, Hedgehog, Notch, PTHrP, and FGF) to coordinate osteogenesis, skeletal development, and bone homeostasis. This review summarizes the recent advances in our understanding of TGF-β/BMP signaling in osteoblast differentiation, chondrocyte differentiation, skeletal development, cartilage formation, bone formation, bone homeostasis, and related human bone diseases caused by the disruption of TGF-β/BMP signaling.

Mesenchymal stromal cells express GARP/LRRC32 on their surface: effects on their biology and immunomodulatory capacity

Mesenchymal stromal cells (MSCs) represent a promising tool for therapy in regenerative medicine, transplantation, and autoimmune disease due to their trophic and immunomodulatory activities. However, we are still far from understanding the mechanisms of action of MSCs in these processes. Transforming growth factor (TGF)-β1 is a pleiotropic cytokine involved in MSC migration, differentiation, and immunomodulation. Recently, glycoprotein A repetitions predominant (GARP) was shown to bind latency-associated peptide (LAP)/TGF-β1 to the cell surface of activated Foxp3⁺ regulatory T cells (Tregs) and megakaryocytes/platelets. In this manuscript, we show that human and mouse MSCs express GARP which presents LAP/TGF-β1 on their cell surface. Silencing GARP expression in MSCs increased their secretion and activation of TGF-β1 and reduced their proliferative capacity in a TGF-β1-independent manner. Importantly, we showed that GARP expression on MSCs contributed to their ability to inhibit T-cell responses in vitro. In summary, we have found that GARP is an essential molecule for MSC biology, regulating their immunomodulatory and proliferative activities. We envision GARP as a new target for improving the therapeutic efficacy of MSCs and also as a novel MSC marker. Stem Cells2015;33:183–195

Assessment of an efficient xeno-free culture system of human periodontal ligament stem cells

The possibility of transplanting adult stem cells into damaged organs has opened new prospects for the treatment of several human pathologies. The purpose of this study was to develop a culture system for the expansion and production of human Periodontal Ligament Stem Cells (hPDLSCs) using a new xeno-free media formulation and ensuring the maintenance of the stem cells features comprising the multiple passage expansion, mesengenic lineage differentiation, cellular phenotype, and genomic stability, essential elements for conforming to translation to cell therapy. Somatic stem cells were isolated from the human periodontium using a minimally invasive periodontal access flap surgery in healthy donors. Expanded hPDLSCs in a xeno-free culture showed the morphological features of stem cells, expressed the markers associated with pluripotency, and a normal karyotype. Under appropriate culture conditions, hPDLSCs presented adipogenic and osteogenic potential; indeed, a very high accumulation of lipid droplets was evident in the cytoplasm of adipogenic-induced cells, and indisputable evidence of osteogenic differentiation, investigated by transmission electron microscopy, and analyzed for gene expression analysis has been shown. Based on these data, the novel xeno-free culture method might provide the basis for Good Manufacturing Procedure culture of autologous stem cells, readily accessible from human periodontium, and can be a resource to facilitate their use in human clinical studies for potential therapeutic regeneration.

Latent TGF-β-binding proteins

The LTBPs (or latent transforming growth factor β binding proteins) are important components of the extracellular matrix (ECM) that interact with fibrillin microfibrils and have a number of different roles in microfibril biology. There are four LTBPs isoforms in the human genome (LTBP-1, -2, -3, and -4), all of which appear to associate with fibrillin and the biology of each isoform is reviewed here. The LTBPs were first identified as forming latent complexes with TGFβ by covalently binding the TGFβ propeptide (LAP) via disulfide bonds in the endoplasmic reticulum. LAP in turn is cleaved from the mature TGFβ precursor in the trans-golgi network but LAP and TGFβ remain strongly bound through non-covalent interactions. LAP, TGFβ, and LTBP together form the large latent complex (LLC). LTBPs were originally thought to primarily play a role in maintaining TGFβ latency and targeting the latent growth factor to the extracellular matrix (ECM), but it has also been shown that LTBP-1 participates in TGFβ activation by integrins and may also regulate activation by proteases and other factors. LTBP-3 appears to have a role in skeletal formation including tooth development. As well as having important functions in TGFβ regulation, TGFβ-independent activities have recently been identified for LTBP-2 and LTBP-4 in stabilizing microfibril bundles and regulating elastic fiber assembly.

Mutations in the latent TGF-beta binding protein 3 (LTBP3) gene cause brachyolmia with amelogenesis imperfecta

Inherited dental malformations constitute a clinically and genetically heterogeneous group of disorders. Here, we report on four families, three of them consanguineous, with an identical phenotype, characterized by significant short stature with brachyolmia and hypoplastic amelogenesis imperfecta (AI) with almost absent enamel. This phenotype was first described in 1996 by Verloes et al. as an autosomal recessive form of brachyolmia associated with AI. Whole-exome sequencing resulted in the identification of recessive hypomorphic mutations including deletion, nonsense and splice mutations, in the LTBP3 gene, which is involved in the TGF-beta signaling pathway. We further investigated gene expression during mouse development and tooth formation. Differentiated ameloblasts synthesizing enamel matrix proteins and odontoblasts expressed the gene. Study of an available knockout mouse model showed that the mutant mice displayed very thin to absent enamel in both incisors and molars, hereby recapitulating the AI phenotype in the human disorder.

Two clinical phenotypes in polycythemia vera

BACKGROUND

Polycythemia vera is the ultimate phenotypic consequence of the V617F mutation in Janus kinase 2 (encoded by JAK2), but the extent to which this mutation influences the behavior of the involved CD34+ hematopoietic stem cells is unknown.

METHODS

We analyzed gene expression in CD34+ peripheral-blood cells from 19 patients with polycythemia vera, using oligonucleotide microarray technology after correcting for potential confounding by sex, since the phenotypic features of the disease differ between men and women.

RESULTS

Men with polycythemia vera had twice as many up-regulated or down-regulated genes as women with polycythemia vera, in a comparison of gene expression in the patients and in healthy persons of the same sex, but there were 102 genes with differential regulation that was concordant in men and women. When these genes were used for class discovery by means of unsupervised hierarchical clustering, the 19 patients could be divided into two groups that did not differ significantly with respect to age, neutrophil JAK2 V617F allele burden, white-cell count, platelet count, or clonal dominance. However, they did differ significantly with respect to disease duration; hemoglobin level; frequency of thromboembolic events, palpable splenomegaly, and splenectomy; chemotherapy exposure; leukemic transformation; and survival. The unsupervised clustering was confirmed by a supervised approach with the use of a top-scoring-pair classifier that segregated the 19 patients into the same two phenotypic groups with 100% accuracy.

CONCLUSIONS

Removing sex as a potential confounder, we identified an accurate molecular method for classifying patients with polycythemia vera according to disease behavior, independently of their JAK2 V617F allele burden, and identified previously unrecognized molecular pathways in polycythemia vera outside the canonical JAK2 pathway that may be amenable to targeted therapy. (Funded by the Department of Defense and the National Institutes of Health.).

The clinical significance and regulation mechanism of hypoxia-inducible factor-1 and miR-191 expression in pancreatic cancer

The aim of study was to discuss the correlation and regulatory mechanism of HIF-1 and miR-191 expression in pancreatic tumor. The association between the miR-191 and the clinicopathologic characteristics and the prognosis of pancreatic cancer was further explored. After hypoxic cultured for 6 and 12 h, qRT-PCR and Western blot were practiced to analyze the miR-191 and HIF-1 expression of MIA PaCa-2 and Aspac1 cells. We regulated the HIF-1 expression via plasmid and siRNA transfection to observe the alteration of HIF-1 and miR-191 expression. ChIP sequencing identified the binding sites of HIF-1 and miR-191. Dual luciferase assays were practiced to verify the binding sites. Immunohistochemical staining was practiced to analyze the expression of HIF-1, while qRT-PCR were done for investigating miR-191 in tumor tissues. Then, the association between the expression of them and the clinicopathologic characteristics and prognosis of pancreatic cancer were analyzed. After hypoxic cultured 12 h, the expression of HIF-1 protein, HIF-1mRNA and miR-191 of MIA PaCa-2 and AsPC-1 cells increased significantly (P < 0.05). After HIF-1 overexpressing plasmid transfected to the MIA PaCa-2 and AsPC-1 cells for 48 h, the expression of HIF-1 protein, HIF-1mRNA, and miR-191 upregulated significantly (P < 0.05). While after transfected the MIA PaCa-2 cells by HIF-1 siRNA, the significant decreasing of HIF-1 protein, HIF-1mRNA, and miR-191 expression were observed (P < 0.05). ChIP sequencing showed the protein synthesis of HIF-1 increased in hypoxia situation. Only the HRE5 (-1,169 bp, ChIP4) were significantly brighter in hypoxia in comparing with normoxic cells. In dual luciferase assays, after pGL3-miR-191 and HIF-1 overexpressing plasmid co-transfect the MIAPaCa-2 cells for 48 h, its relative expression of bioluminescence was higher than those co-transfected by mutant miR-191 vectors and HIF-1 overexpressing plasmid or by pGL3-miR-191 and HIF-1 empty plasmid. The expression of miR-191 closely associated with the tumor size, pTNM stage, lymph node metastasis, and perineural invasion (P < 0.05). Patients with higher expression of miR-191 were a risk factor for prognosis of pancreatic cancers. Expression of HIF-1 in pancreatic cancer cells increased under the condition of chronic hypoxia, which may bind to HRE2 in 5'flanking region of miR-191 and initiate transcription of miR-191. Expression of miR-191 was significantly higher in pancreatic tumor tissues. The expression of miR-191 closely associated with the tumor size, pTNM stage, lymph node metastasis and perineural invasion and poor prognosis of pancreatic cancer.

Overexpression of TGF-β1 enhances chondrogenic differentiation and proliferation of human synovium-derived stem cells

Transforming growth factor-beta (TGF-β) superfamily proteins play a critical role in proliferation, differentiation, and other functions of mesenchymal stem cells (MSCs). During chondrogenic differentiation of MSCs, TGF-β up-regulates chondrogenic gene expression by enhancing the expression of the transcription factor SRY (sex-determining region Y)-box9 (Sox9). In this study, we investigated the effect of continuous TGF-β1 overexpression in human synovium-derived MSCs (hSD-MSCs) on immunophenotype, differentiation potential, and proliferation rate. hSD-MSCs were transduced with recombinant retroviruses (rRV) encoding TGF-β1. The results revealed that continuous overexpression of TGF-β1 did not affect their phenotype as evidenced by flow cytometry and reverse transcriptase PCR (RT-PCR). In addition, continuous TGF-β1 overexpression strongly enhanced cell proliferation of hSD-MSCs compared to the control groups. Also, induction of chondrogenesis was more effective in rRV-TGFB-transduced hSD-MSCs as shown by RT-PCR for chondrogenic markers, toluidine blue staining and glycosaminoglycan (GAG)/DNA ratio. Our data suggest that overexpression of TGF-β1 positively enhances the proliferation and chondrogenic potential of hSD-MSCs.

TGF-β stimulation in human and murine cells reveals commonly affected biological processes and pathways at transcription level

Background

The TGF-β signaling pathway is a fundamental pathway in the living cell, which plays a key role in many central cellular processes. The complex and sometimes contradicting mechanisms by which TGF-β yields phenotypic effects are not yet completely understood. In this study we investigated and compared the transcriptional response profile of TGF-β1 stimulation in different cell types. For this purpose, extensive experiments are performed and time-course microarray data are generated in human and mouse parenchymal liver cells, human mesenchymal stromal cells and mouse hematopoietic progenitor cells at different time points. We applied a panel of bioinformatics methods on our data to uncover common patterns in the dynamic gene expression response in respective cells.

Results

Our analysis revealed a quite variable and multifaceted transcriptional response profile of TGF-β1 stimulation, which goes far beyond the well-characterized classical TGF-β1 signaling pathway. Nonetheless, we could identify several commonly affected processes and signaling pathways across cell types and species. In addition our analysis suggested an important role of the transcription factor EGR1, which appeared to have a conserved influence across cell-types and species. Validation via an independent dataset on A549 lung adenocarcinoma cells largely confirmed our findings. Network analysis suggested explanations, how TGF-β1 stimulation could lead to the observed effects.

Conclusions

The analysis of dynamical transcriptional response to TGF-β treatment experiments in different human and murine cell systems revealed commonly affected biological processes and pathways, which could be linked to TGF-β1 via network analysis. This helps to gain insights about TGF-β pathway activities in these cell systems and its conserved interactions between the species and tissue types.

TGF-beta1 does not induce senescence of multipotent mesenchymal stromal cells and has similar effects in early and late passages

Transforming growth factor-beta 1 (TGF-β1) stimulates a broad range of effects which are cell type dependent, and it has been suggested to induce cellular senescence. On the other hand, long-term culture of multipotent mesenchymal stromal cells (MSCs) has a major impact on their cellular physiology and therefore it is well conceivable that the molecular events triggered by TGF-β1 differ considerably in cells of early and late passages. In this study, we analyzed the effect of TGF-β1 on and during replicative senescence of MSCs. Stimulation with TGF-β1 enhanced proliferation, induced a network like growth pattern and impaired adipogenic and osteogenic differentiation. TGF-β1 did not induce premature senescence. However, due to increased proliferation rates the cells reached replicative senescence earlier than untreated controls. This was also evident, when we analyzed senescence-associated DNA-methylation changes. Gene expression profiles of MSCs differed considerably at relatively early (P 3-5) and later passages (P 10). Nonetheless, relative gene expression differences provoked by TGF-β1 at individual time points or in a time course dependent manner (stimulation for 0, 1, 4 and 12 h) were very similar in MSCs of early and late passage. These results support the notion that TGF-β1 has major impact on MSC function, but it does not induce senescence and has similar molecular effects during culture expansion.

Modifying muscular dystrophy through transforming growth factor-β

Muscular dystrophy arises from ongoing muscle degeneration and insufficient regeneration. This imbalance leads to loss of muscle, with replacement by scar or fibrotic tissue, resulting in muscle weakness and, eventually, loss of muscle function. Human muscular dystrophy is characterized by a wide range of disease severity, even when the same genetic mutation is present. This variability implies that other factors, both genetic and environmental, modify the disease outcome. There has been an ongoing effort to define the genetic and molecular bases that influence muscular dystrophy onset and progression. Modifier genes for muscle disease have been identified through both candidate gene approaches and genome-wide surveys. Multiple lines of experimental evidence have now converged on the transforming growth factor-β (TGF-β) pathway as a modifier for muscular dystrophy. TGF-β signaling is upregulated in dystrophic muscle as a result of a destabilized plasma membrane and/or an altered extracellular matrix. Given the important biological role of the TGF-β pathway, and its role beyond muscle homeostasis, we review modifier genes that alter the TGF-β pathway and approaches to modulate TGF-β activity to ameliorate muscle disease.

Gremlin-1 associates with fibrillin microfibrils in vivo and regulates mesothelioma cell survival through transcription factor slug

Malignant mesothelioma is a form of cancer that is highly resistant to conventional cancer therapy for which no major therapeutic advances have been introduced. Here, we identify gremlin-1, a known bone morphogenetic protein inhibitor crucial for embryonic development, as a potential therapeutic target for mesothelioma. We found high expression levels of gremlin-1 in the mesothelioma tumor tissue, as well as in primary mesothelioma cells cultured from pleural effusion samples. Downregulation of gremlin-1 expression by siRNA-mediated silencing in a mesothelioma cell line inhibited cell proliferation. This was associated with downregulation of the transcription factor slug as well as mesenchymal proteins linked to cancer epithelial-to-mesenchymal transition. Further, resistance to paclitaxel-induced cell death was associated with high gremlin-1 and slug expression. Treatment of gremlin-1-silenced mesothelioma cells with paclitaxel or pemetrexed resulted in efficient loss of cell survival. Finally, our data suggest that concomitant upregulation of fibrillin-2 in mesothelioma provides a mechanism for extracellular localization of gremlin-1 to the tumor microenvironment. This was supported by the demonstration of interactions between gremlin-1, and fibrillin-1 and -2 peptides as well as by colocalization of gremlin-1 to fibrillin microfibrils in cells and tumor tissue samples. Our data suggest that gremlin-1 is also a potential target for overcoming drug resistance in mesothelioma.

Determination of mesenchymal stem cell fate by pigment epithelium-derived factor (PEDF) results in increased adiposity and reduced bone mineral content

Pigment epithelium-derived factor (PEDF), the protein product of the SERPINF1 gene, has been linked to distinct diseases involving adipose or bone tissue, the metabolic syndrome, and osteogenesis imperfecta (OI) type VI. Since mesenchymal stem cell (MSC) differentiation into adipocytes vs. osteoblasts can be regulated by specific factors, PEDF-directed dependency of murine and human MSCs was assessed. PEDF inhibited adipogenesis and promoted osteoblast differentiation of murine MSCs, osteoblast precursors, and human MSCs. Blockade of adipogenesis by PEDF suppressed peroxisome proliferator-activated receptor-γ (PPARγ), adiponectin, and other adipocyte markers by nearly 90% compared with control-treated cells (P<0.001). Differentiation to osteoblasts by PEDF resulted in a common pathway that involved PPARγ suppression (P<0.01). Canonical Wnt-β-catenin signaling results in a MSC differentiation pattern analogous to that seen with PEDF. Thus, adding PEDF enhanced Wnt-β-catenin signal transduction in human MSCs, demonstrating a novel Wnt agonist function. In PEDF knockout (KO) mice, total body adiposity was increased by >50% compared with controls, illustrating its systemic role as a negative regulator of adipogenesis. Bones from KO mice demonstrated a reduction in mineral content recapitulating the OI type VI phenotype. These results demonstrate that the human diseases associated with PEDF reflect its ability to modulate MSC differentiation.

Hypomethylation of the hsa-miR-191 locus causes high expression of hsa-mir-191 and promotes the epithelial-to-mesenchymal transition in hepatocellular carcinoma

hsa-miR-191 is highly expressed in hepatocellular carcinoma (HCC), but the factors regulating this elevated expression are unknown. This study aimed to investigate the epigenetic mechanisms of increased hsa-miR-191 expression by analyzing the relationship between the DNA methylation status of hsa-miR-191 and miR-191 expression. Methylation-specific polymerase chain reaction (PCR), bisulfite sequencing PCR, Northern blot, and quantitative real-time PCR were performed to examine hsa-miR-191 methylation and expression levels. Western blot, transwell, and scratch assays were performed to examine the function and molecular mechanisms of hsa-miR-191. Approximately 58.9% of hsa-miR-191 expression was higher in HCC tissues than in adjacent noncancerous tissues; this high expression was associated with poor prognosis. The hypomethylation observed in some HCC cell lines and HCC tissues was correlated with the hsa-miR-191 expression level. This correlation was validated by treatment with the 5-aza-DAC demethylation agent. The level of hypomethylation was 63.0% in 73 clinical HCC tissue samples and was associated with increased (2.1-fold) hsa-miR-191 expression. The elevated expression of hsa-miR-191 in the SMMC-771 HCC cell line induced the cells to transition into mesenchymal-like cells; they exhibited characteristics such as loss of adhesion, down-regulation of epithelial cell markers, up-regulation of mesenchymal cell markers, and increased cell migration and invasion. Inhibiting hsa-miR-191 expression in the SMMC-7721 cell line reversed this process (as assessed by cell morphology and cell markers). Furthermore, hsa-miR-191 probably exerted its function by directly targeting TIMP metallopeptidase inhibitor 3 and inhibiting TIMP3 protein expression. Our results suggest that hsa-miR-191 locus hypomethylation causes an increase in hsa-miR-191 expression in HCC clinical tissues and that this expression induces HCC cells to transition into mesenchymal-like cells.

Genome-wide expression profiling reveals new candidate genes associated with osteoarthritis

INTRODUCTION

Although the extracellular matrix (ECM) is the functional element in articular cartilage and its degradation is central in the pathogenetic process in osteoarthritis (OA), increasing the knowledge about the cellular OA phenotype is essential. The aim of this study is therefore to provide a more complete picture of the cellular and molecular alterations detected in OA cartilage.

MATERIAL AND METHODS

Human articular cartilage biopsies were collected from donors with macroscopical and microscopical signs of OA as well as donors with no previous history of OA and with microscopically intact cartilage. RNA was isolated from the biopsies and subjected to whole genome microarray analysis. Important results from the microarray analysis were verified using real-time PCR and immunohistochemistry.

RESULTS

Our results reveal several new candidate genes not previously associated with OA to display significantly higher expression in OA cartilage than in normal donor cartilage, including genes involved in bone formation (CLEC3B, CDH11, GPNMB, CLEC3A, CHST11, MSX1, MSX2) and genes encoding collagens (COL13A1, COL14A1, COL15A1, COL8A2).

DISCUSSION

This study is the first to report a comprehensive gene expression analysis of human OA cartilage compared to control cartilage from donors lacking macroscopical and microscopical signs of OA using recently developed microarrays containing the whole human genome. Our results could broadly confirm previously published data on many characteristic features of OA as well as adding a panel of genes to the list of genes known to be differentially expressed in OA. Elucidation of the phenotypical alterations occurring in OA chondrocytes is important for the development of effective treatments for OA.

Matrix association of latent TGF-beta binding protein-2 (LTBP-2) is dependent on fibrillin-1

The components of the extracellular matrix (ECM) and their differential expression patterns play important roles in tissue formation. The deposition of latent TGF-beta binding proteins (LTBPs) to the ECM exhibit distinct distribution profiles. We have analyzed here the temporal and spatial ECM association of latent TGF-beta binding protein LTBP-2 in cultured human embryonic lung fibroblasts. We found that LTBP-2 was not assembled to the ECM until by confluency of cultures following the deposition of fibronectin (FN) and fibrillin-1. In 5-day-old cultures LTBP-2 was rapidly secreted from cells and it subsequently associated with the ECM as shown by metabolic labeling and immunoprecipitation. LTBP-2 colocalized transiently with fibronectin and failed to assemble to the ECM of FN deficient mouse fibroblasts. Analysis of different cultured human cell lines revealed partial colocalization of LTBP-2 and fibrillin-1 in the ECM of fibroblasts, MG-63 osteosarcoma cells and human vascular endothelial cells. Silencing of fibrillin-1 expression by lentiviral shRNAs profoundly disrupted the deposition of LTBP-2. Current results suggest that LTBP-2 is not an element of the provisional ECM of fibroblasts but is more likely a component of more mature ECM and indicate that matrix association of LTBP-2 depends on a pre-formed fibrillin-1 network.