Osteogenic-differentiated Mesenchymal Stem Cell-secreted Extracellular Matrix as a Bone Morphogenetic Protein-2 delivery system for ectopic bone formation

International audienceWhile human bone morphogenetic protein-2 (BMP-2) is a promising growth factor for bone regeneration, a major challenge in biomedical applications is finding an optimal carrier for its delivery at the site of injury. Because of their natural affinities for growth factors (including BMP-2) as well as their role in instructing cell function, cultured cell-derived extracellular matrices (ECM) are of special interest. We hereby hypothesized that a “bony matrix” containing mineralized, osteogenic ECM is a potential efficacious carrier of BMP-2 for promoting bone formation and, therefore, compared the efficacy of the decellularized ECM derived from osteogenic-differentiated human mesenchymal stem cells (hMSCs) to the one obtained from ECM from undifferentiated hMSCs. Our results provided evidence that both ECMs can bind BMP-2 and promote bone formation when implanted ectopically in mice. The osteoinductive potential of BMP-2, however, was greater when loaded within an osteogenic MSC-derived ECM; this outcome was correlated with higher sequestration capacity of BMP-2 over time in vivo. Interestingly, although the BMP-2 mainly bound onto the mineral crystals contained within the osteogenic MSC derived-ECM, these mineral components were not involved in the observed higher osteoinductivity, suggesting that the organic components were the critical components for the matrix efficacy as BMP-2 carrier

Osteogenic potential of adipogenic predifferentiated human bone marrow-derived multipotent stromal cells for bone tissue-engineering

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Effect of the bone morphogenetic protein-2 doses on the osteogenic potential of human multipotent stromal cells- containing tissue engineered constructs

The addition of bone morphogenetic protein-2 (BMP-2) with multipotent stromal cells (MSC) is an attractive strategy to enhance the bone-forming potential of MSC-based tissue engineering (TE) constructs. However, the effective dosage of BMP-2 remains to be determined. In this study, we evaluated the effects of human MSCs codelivered with BMP-2 at either low or high dosage on the bone-forming potential of constructs in a mice ectopic model. Our results showed that the addition of only low dose of BMP-2 was beneficial to enhance the bone-forming potential of MSCs, whereas high dose of BMP-2 overcame the advantage of combining this growth factor with MSCs. Expressions of select genes of both murine and human origins in TE constructs demonstrated that the beneficial effect of low dose of BMP-2 with implanted human MSCs did not involve enhanced differentiation of these cells into osteoblasts or induction of paracrine cues but rather involved induction of the osteogenic differentiation of the host progenitors. Therefore, the advantage of combining BMP-2 with MSCs to enhance the bone-forming potential of TE constructs appeared to be an additive effect of both components rather than a synergistic one

Targeted resequencing of the 13q13 spondyloarthritis-linked locus identifies a rare variant in FREM2 possibly associated with familial spondyloarthritis

International audienceObjectives: The strong heritability of spondyloarthritis remains poorly explained, despite several large-scale association studies. A recent linkage analysis identified a new region linked to SpA on 13q13. Here we searched for variants potentially explaining this linkage signal by deep-sequencing of the region. Methods: Re-sequencing of the 1.4 Mb target interval was performed in 92 subjects from the 43 best-linked multicases families (71 spondyloarthritis and 21 unaffected relatives), using hybridization capture-based protocol (Illumina Nextera®). Variants of interest were then genotyped by TaqMan and high resolution melting to check their co-segregation with disease in the same families and to test their association with spondyloarthritis in an independent cohort of 1,091 unrelated cases and 399 controls. Expression of FREM2 was assessed by immunostaining. Results: Of the 7,563 variants identified, 24 were non-synonymous coding single-nucleotide variants. Two of them were located in the FREM2 gene on a haplotype co-segregating with the disease, including one common variant (R1840 W, minor allele frequency = 0.11) and one rare variant (R727H, minor allele frequency = 0.0001). In the case-control analysis, there was no significant association between R1840 W and spondyloarthritis (P-value = 0.21), whereas R727H was not detected in any of the genotyped individuals. Immunostaining experiments revealed that FREM2 is expressed in synovial membrane, cartilage and colon. Conclusions: Targeted re-sequencing of a spondyloarthritis-linked region allowed us to identify a rare non-synonymous coding variant in FREM2, co-segregating with spondyloarthritis in a large family. This gene is expressed in several tissues relevant to spondyloarthritis pathogenesis, supporting its putative implication in spondyloarthritis

Custom-made macroporous bioceramic implants based on triply-periodic minimal surfaces for bone defects in load-bearing sites

International audienceThe architectural features of synthetic bone grafts are key parameters for regulating cell functions and tissue formation for the successful repair of bone defects. In this regard, macroporous structures based on triplyperiodic minimal surfaces (TPMS) are considered to have untapped potential. In the present study, custom-made implants based on a gyroid structure, with (GPRC) and without (GP) a cortical-like reinforcement, were specifically designed to fit an intended bone defect in rat femurs. Sintered hydroxyapatite implants were produced using a dedicated additive manufacturing technology and their morphological, physico-chemical and mechanical features were characterized. The implants' integrity and ability to support bone ingrowth were assessed after 4, 6 and 8 weeks of implantation in a 3-mm-long, femoral defect in Lewis rats. GP and GPRC implants were manufactured with comparable macro-to nano-architectures. Cortical-like reinforcement significantly improved implant effective stiffness and resistance to fracture after implantation. This cortical-like reinforcement also concentrated new bone formation in the core of the GPRC implants, without affecting newly formed bone quantity or maturity. This study showed, for the first time, that custom-made TPMS-based bioceramic implants could be produced and successfully implanted in load-bearing sites. Adding a cortical-like reinforcement (GPRC implants) was a relevant solution to improve implant mechanical resistance, and changed osteogenic mechanism compared to the GP implants

Intense bone fluorescence reveals hidden patterns in pumpkin toadlets.

The phenomenon of fluorescence can be used by animals to change effective colouration or patterning, potentially to serve functions including intra- and interspecific signalling. Initially believed to be restricted to marine animals, fluorescent colours are now being described in an increasing number of terrestrial species. Here, we describe unique, highly fluorescent patterns in two species of pumpkin toadlets (Brachycephalus ephippium and B. pitanga). We establish that the origin of the fluorescence lies in the dermal bone of the head and back, visible through a particularly thin skin. By comparing them to those of the closely related species Ischnocnema parva, we demonstrate that pumpkin toadlets' bones are exceptionally fluorescent. We characterize the luminescence properties of the toadlets' bones and discuss the potential function of fluorescent patterns in natural lighting conditions

3D‐Printed Osteoinductive Polymeric Scaffolds with Optimized Architecture to Repair a Sheep Metatarsal Critical‐Size Bone Defect

Abstract The reconstruction of critical‐size bone defects in long bones remains a challenge for clinicians. A new osteoinductive medical device is developed here for long bone repair by combining a 3D‐printed architectured cylindrical scaffold made of clinical‐grade polylactic acid (PLA) with a polyelectrolyte film coating delivering the osteogenic bone morphogenetic protein 2 (BMP‐2). This film‐coated scaffold is used to repair a sheep metatarsal 25‐mm long critical‐size bone defect. In vitro and in vivo biocompatibility of the film‐coated PLA material is proved according to ISO standards. Scaffold geometry is found to influence BMP‐2 incorporation. Bone regeneration is followed using X‐ray scans, µCT scans, and histology. It is shown that scaffold internal geometry, notably pore shape, influenced bone regeneration, which is homogenous longitudinally. Scaffolds with cubic pores of ≈870 µm and a low BMP‐2 dose of ≈120 µg cm −3 induce the best bone regeneration without any adverse effects. The visual score given by clinicians during animal follow‐up is found to be an easy way to predict bone regeneration. This work opens perspectives for a clinical application in personalized bone regeneration