TGF-β Type II Receptor/MCP-5 Axis: At the Crossroad between Joint and Growth Plate Development

Despite its clinical significance, the mechanisms of joint morphogenesis are still elusive. Here, we show by combining laser-capture microdissection for RNA sampling with microarray analysis, that the setting in which joint-forming interzone cells develop is distinct from adjacent growth plate chondrocytes and is characterized by down-regulation of chemokines, such as monocyte-chemoattractant protein-5 (MCP-5). Using in-vivo, ex-vivo and in-vitro approaches, we showed that low levels of interzone-MCP-5 are essential for joint formation and contribute to proper growth plate organization. Mice lacking the TGF-β-type-II-receptor (TβRII) in their limbs (Tgfbr2Prx1KO), which lack joint development and fail chondrocyte hypertrophy, showed up-regulation of interzone-MCP-5. In-vivo and ex-vivo blockade of the sole MCP-5 receptor, CCR2, in Tgfbr2Prx1KO led to rescue of joint formation and growth plate maturation; while in control mice determined an acceleration of endochondral growth plate mineralization. Taken together, we characterized the TβRII/MCP-5 axis as an essential crossroad for joint development and endochondral growth

Joint TGF-β Type II Receptor-Expressing Cells: Ontogeny and Characterization as Joint Progenitors

TGF-β type II receptor (Tgfbr2) signaling plays an essential role in joint-element development. The Tgfbr2PRX-1KO mouse, in which the Tgfbr2 is conditionally inactivated in developing limbs, lacks interphalangeal joints and tendons. In this study, we used the Tgfbr2-β-Gal-GFP-BAC mouse as a LacZ/green fluorescent protein (GFP)-based read-out to determine: the spatial and temporally regulated expression pattern of Tgfbr2-expressing cells within joint elements; their expression profile; and their slow-cycling labeling with bromodeoxyuridine (BrdU). Tgfbr2-β-Gal activity was first detected at embryonic day (E) 13.5 within the interphalangeal joint interzone. By E16.5, and throughout adulthood, Tgfbr2-expressing cells clustered in a contiguous niche that comprises the groove of Ranvier and the synovio-entheseal complex including part of the perichondrium, the synovium, the articular cartilage superficial layer, and the tendon's entheses. Tgfbr2-expressing cells were found in the synovio-entheseal complex niche with similar temporal pattern in the knee, where they were also detected in meniscal surface, ligaments, and the synovial lining of the infrapatellar fat pad. Tgfbr2-β-Gal-positive cells were positive for phospho-Smad2, signifying that the Tgfbr2 reporter was accurate. Developmental-stage studies showed that Tgfbr2 expression was in synchrony with expression of joint-morphogenic genes such as Noggin, GDF5, Notch1, and Jagged1. Prenatal and postnatal BrdU-incorporation studies showed that within this synovio-entheseal-articular-cartilage niche most of the Tgfbr2-expressing cells labeled as slow-proliferating cells, namely, stem/progenitor cells. Tgfbr2-positive cells, isolated from embryonic limb mesenchyme, expressed joint progenitor markers in a time- and TGF-β-dependent manner. Our studies provide evidence that joint Tgfbr2-expressing cells have anatomical, ontogenic, slow-cycling trait and in-vivo and ex-vivo expression profiles of progenitor joint cells

Systemically delivered insulin-like growth factor-I enhances mesenchymal stem cell-dependent fracture healing

In this study, we examined the effectiveness of systemic subcutaneous delivery of recombinant Insulin-like growth factor (IGF)-I concurrently with primary cultured bone marrow-derived mesenchymal stem cell (MSC) transplant on fracture repair. We found that the fracture callus volume increased in mice with a stabilized tibia fracture that received IGF-I + MSC when compared with that in either untreated or MSC alone treated mice. In evaluating the callus tissue components, we found that the soft and new bone tissue volumes were significantly increased in IGF-I + MSC recipients. Histological and in-situ hybridization analyses confirmed a characteristic increase of newly forming bone in IGF-I + MSC recipients and that healing progressed mostly through endochondral ossification. The increase in soft and new bone tissue volumes correlated with increased force and toughness as determined by biomechanical testing. In conclusion, MSC transplant concurrent with systemic delivery of IGF-I improves fracture repair suggesting that IGF-I + MSC could be a novel therapeutic approach in patients who have inadequate fracture repair

Evaluation of IRS-1 role in osteoblastic differentiation of osteosarcoma cells and MSCs

L’osteosarcoma (OS) è il tumore primitivo dell’osso più comune in età pediatrica e adolescenziale. L’OS è stato recentemente riconsiderato come una patologia da de-differenziamento, legata all’interruzione del processo cui vanno incontro i precursori osteoblastici, quali le cellule staminali mesenchimali (MSCs), per trasformarsi in osteoblasti maturi. Il sistema IGF è coinvolto nella regolazione della proliferazione e del differenziamento di cellule di OS. IRS-1 è un mediatore critico di tale via di segnalazione e il suo livello di espressione modula il differenziamento di cellule ematopoietiche. Lo scopo di questa tesi è stato quello di definire il ruolo di IRS-1 nel differenziamento osteoblastico di MSCs e cellule di OS. Il potenziale differenziativo di cellule di OS umano e murino e di MSCs derivate da midollo osseo è stato valutato tramite Alizarin Red staining e Real Time-PCR. Dai dati ottenuti è emerso come i livelli di espressione di IRS-1 diminuiscano durante il differenziamento osteoblastico. Conseguentemente, i livelli di espressione di IRS-1 sono stati manipolati utilizzando shRNA per down-regolare l’espressione della proteina o un plasmide per sovra-esprimerla. Sia la down-regolazione sia la sovra-espressione di IRS-1 hanno inibito il differenziamento osteoblastico delle linee cellulari considerate. Allo scopo di valutare il contributo di IRS-1 nella via di segnalazione di IGF-1R è stato utilizzato l’inibitore di tale recettore, αIR-3. Anche in questo caso è stata osservata una riduzione della capacità differenziativa. L’inibitore del proteasoma MG-132 ha portato ad un aumento dei livelli di IRS-1, portando nuovamente all’inibizione del differenziamento osteoblastico e suggerendo che l’ubiquitinazione di questa proteina potrebbe avere un ruolo importante nel mantenimento di appropriati livelli di espressione di IRS-1. I risultati ottenuti indicano la criticità dei livelli di espressione di IRS-1 nella determinazione della capacità differenziativa sia di cellule di OS umano e murino, sia delle MSCs.Osteosarcoma (OS) is the most common primary malignant bone tumor affecting children and adolescents. OS has recently been re-considered as a differentiation disease, caused by genetic and epigenetic alterations which may impair normal bone development by blocking multipotent mesenchymal stem cell (MSCs) differentiation into osteoblasts. The IGF-system is involved in regulating OS cell proliferation and differentiation. IRS-1 is a critical mediator of IGF-1R signaling and its expression level modulates hematopoietic cell differentiation. The aim of this study is to define the role of IRS-1 in the osteoblastic differentiation of MSCs and OS cells. Differentiating potential of human and murine OS cell lines and bone marrow-derived mouse MSCs was evaluated by Alizarin Red staining and real-time PCR. We found that IRS-1 expression level decreased during differentiation. Consequently, IRS-1 expression levels were manipulated using shRNAs to knock-down, or a plasmid to over-express the protein. Both down-regulation and over-expression of IRS-1 inhibited osteoblastic differentiation. To understand the contribution of IRS-1 in the IGF-1R pathway we used the αIR-3 IGF-1R blocking antibody, which inhibited the differentiation process. The proteasome inhibitor MG-132 led to an increase in IRS-1 protein level that again inhibited osteoblastic differentiation, suggesting ubiquitination may play a role in maintaining the appropriate expression level of IRS-1. Taken together, these results indicate that IRS-1 expression level is critical for determining the differentiating capacity of MSCs as well as human and mouse OS cells and that precise regulation of IRS-1 expression by cells is required for this commitment to osteoblastic differentiation

In vitro biological water-gas shift reaction: Characterization and grafting on carbon nanotubes of recombinant Rhodospirillum rubrum CO-dehydrogenase (CODH)

International audienc

Electrochemical CO2-to-CO interconversion by an engineered Carbon Monoxide Dehydrogenase-Immobilized on Multiwall Carbon Nanotubes

International audienc

Efficient Electrochemical CO2/CO Interconversion by an Engineered Carbon Monoxide Dehydrogenase on a Gas-Diffusion Carbon Nanotube-Based Bioelectrode

International audienceCarbon monoxide dehydrogenase catalyzes the reversible oxidation of CO to CO2. The monofunctional enzyme from Rhodospirillum rubrum (RrCODH) has been extensively characterized in the past, although its use and investigation by bioelectrochemistry have been limited. Here, we developed a heterologous system yielding a highly stable and active recombinant RrCODH in one-step purification, with CO oxidation activity reaching a maximum of 26 500 U.mg(-1), making RrCODH the most active CODH under ambient conditions described so far. Electron paramagnetic resonance was used to precisely characterize the recombinant RrCODH, demonstrating the integrity of the active site. Selective CO2/CO interconversion with maximum turnover frequencies of 150 s(-1) for CO oxidation (1.5 mA cm(-2) at 250 mV overpotential) and 420 s(-1) for CO2 reduction (4.2 mA cm(-2) at 180 mV overpotential) is catalyzed by the recombinant RrCODH immobilized on MWCNT electrodes modified with 1-pyrenebutyric acid adamantyl amide (MWCNTADA), either in a classic three-electrode cell or in specifically designed CO2/CO-diffusing electrodes. This functional device is stable for hours with a turnover number of at least 800 000. The performances of recombinant RrCODH-modified MWCNTADA are close to the best metal-based and molecular-based catalysts. These results greatly increase the benchmark for bioelectrocatalysis of reversible CO2 conversion

In vitro biological water-gas shift reaction: characterization and grafting of recombinant Rhodospirillum rubrum CO-dehydrogenase

National audienc

Joint TGF-β Type II Receptor-Expressing Cells: Ontogeny and Characterization as Joint Progenitors

TGF-β type II receptor (Tgfbr2) signaling plays an essential role in joint-element development. The Tgfbr2(PRX-1KO) mouse, in which the Tgfbr2 is conditionally inactivated in developing limbs, lacks interphalangeal joints and tendons. In this study, we used the Tgfbr2-β-Gal-GFP-BAC mouse as a LacZ/green fluorescent protein (GFP)-based read-out to determine: the spatial and temporally regulated expression pattern of Tgfbr2-expressing cells within joint elements; their expression profile; and their slow-cycling labeling with bromodeoxyuridine (BrdU). Tgfbr2-β-Gal activity was first detected at embryonic day (E) 13.5 within the interphalangeal joint interzone. By E16.5, and throughout adulthood, Tgfbr2-expressing cells clustered in a contiguous niche that comprises the groove of Ranvier and the synovio-entheseal complex including part of the perichondrium, the synovium, the articular cartilage superficial layer, and the tendon's entheses. Tgfbr2-expressing cells were found in the synovio-entheseal complex niche with similar temporal pattern in the knee, where they were also detected in meniscal surface, ligaments, and the synovial lining of the infrapatellar fat pad. Tgfbr2-β-Gal-positive cells were positive for phospho-Smad2, signifying that the Tgfbr2 reporter was accurate. Developmental-stage studies showed that Tgfbr2 expression was in synchrony with expression of joint-morphogenic genes such as Noggin, GDF5, Notch1, and Jagged1. Prenatal and postnatal BrdU-incorporation studies showed that within this synovio-entheseal-articular-cartilage niche most of the Tgfbr2-expressing cells labeled as slow-proliferating cells, namely, stem/progenitor cells. Tgfbr2-positive cells, isolated from embryonic limb mesenchyme, expressed joint progenitor markers in a time- and TGF-β-dependent manner. Our studies provide evidence that joint Tgfbr2-expressing cells have anatomical, ontogenic, slow-cycling trait and in-vivo and ex-vivo expression profiles of progenitor joint cells