Harnessing Wharton's jelly stem cell differentiation into bone-like nodule on calcium phosphate substrate without osteoinductive factors.

An important aim of bone regenerative medicine is to design biomaterials with controlled chemical and topographical features to guide stem cell fate towards osteoblasts without addition of specific osteogenic factors. Herein, we find that sprayed bioactive and biocompatible calcium phosphate substrates (CaP) with controlled topography induce, in a well-orchestrated manner, Wharton's jelly stem cells (WJ-SCs) differentiation into osteoblastic lineage without any osteogenic supplements. The resulting WJ-SCs commitment exhibits features of native bone, through the formation of three-dimensional bone-like nodule with osteocyte-like cells embedded into a mineralized type I collagen. To our knowledge, these results present the first observation of a whole differentiation process from stem cell to osteocytes-like on a synthetic material. This suggests a great potential of sprayed CaP and WJ-SCs in bone tissue engineering. These unique features may facilitate the transition from bench to bedside and the development of successful engineered bone.Designing materials to direct stem cell fate has a relevant impact on stem cell biology and provides insights facilitating their clinical application in regenerative medicine. Inspired by natural bone compositions, a friendly automated spray-assisted system was used to build calcium phosphate substrate (CaP). Sprayed biomimetic solutions using mild conditions led to the formation of CaP with controlled physical properties, good bioactivity and biocompatibility. Herein, we show that via optimization of physical properties, CaP substrate induce osteogenic differentiation of Wharton's jelly stem cells (WJ-SCs) without adding osteogenic supplement factors. These results suggest a great potential of sprayed CaP and WJ-SCs in bone tissue engineering and may facilitate the transition from bench to beside and the development of clinically successful engineered bone.journal articleresearch support, non-u.s. gov't2017 022016 11 22importe

Bone Environment Influences Irreversible Adhesion of a Methicillin-Susceptible Staphylococcus aureus Strain

Prosthesis and joint infections are an important threat in public health, especially due to the development of bacterial biofilms and their high resistance to antimicrobials. Biofilm-associated infections increase mortality and morbidity rates as well as hospitalization costs. Prevention is the best strategy for this serious issue, so there is an urgent need to understand the signals that could induce irreversible bacterial adhesion on a prosthesis. In this context, we investigated the influence of the bone environment on surface adhesion by a methicillin-susceptible Staphylococcus aureus strain. Using static and dynamic biofilm models, we tested various bone environment factors and showed that the presence of Mg2+, lack of oxygen, and starvation each increased bacterial adhesion. It was observed that human osteoblast-like cell culture supernatants, which contain secreted components that would be found in the bone environment, increased bacterial adhesion capacity by 2-fold (p = 0.015) compared to the medium control. Moreover, supernatants from osteoblast-like cells stimulated with TNF-α to mimic inflammatory conditions increased bacterial adhesion by almost 5-fold (p = 0.003) without impacting on the overall biomass. Interestingly, the effect of osteoblast-like cell supernatants on bacterial adhesion could be counteracted by the activity of synthetic antibiofilm peptides. Overall, the results of this study demonstrate that factors within the bone environment and products of osteoblast-like cells directly influence S. aureus adhesion and could contribute to biofilm initiation on bone and/or prosthetics implants

Identification of macro-heterogenous mechanical behaviour of temporomandibular joint disc

International audienceThe temporomandibular joint (TMJ) is one of the most utilized joints of the human body, not even resting during sleep (for instance people suffering of bruxism). The TMJ disc, a fibrocartilage, allows smooth joint movement and serves as a stress/force distributor between the temporal bone and the condyle. Being a crucial part of the joint, its biomechanical behaviour has to be studied, however tests on complete discs are rare. Among mechanical characterisation procedures, spherical compression does not require specific sample preparation hence discs can keep their integrity (Lee et al. 2016). Furthermore, different disc regions can be tested, and the compression tool radius can be adapted to the disc’s biconcavity. Experimentally the spherical compression tool displacement d is measured, which generally is different from the penetration depth δ. Therefore, the disadvantage of such a test lies in obtaining stress-strain curves since the contact radius a related to the penetration depth δ is required to evaluate the representative stress and strain σ* and ε*. Actually, the Hertz model based on contact of a sphere with a linear elastic half-space is used as a first approximation (Tappert et al. 2017)

Intracellular calcium oscillations in articular chondrocytes induced by basic calcium phosphate crystals lead to cartilage degradation

Objective: Basic calcium phosphate (BCP) crystals, including octacalcium phosphate (OCP), carbonated-apatite (CA) and hydroxyapatite (HA) crystals are associated with destructive forms of osteoarthritis. Mechanisms of BCP-induced cartilage breakdown remain incompletely understood. We assessed the ability of BCP to induce changes in intracellular calcium (iCa(2+)) content and oscillations and the role of iCa(2+) in BCP-induced cartilage degradation. Methods: Bovine articular chondrocytes (BACs) and bovine cartilage explants (BCEs) were stimulated with BCP or monosodium urate (MSU) crystals. iCa(2+) levels were determined by spectrofluorimetry and oscillations by confocal microscopy. mRNA expression of matrix metalloproteinase 3 (MMP-3), a disintegrin and metalloprotease with thrombospondin-like motifs 4 (ADAMTS-4) and ADAMTS-5 was assessed by quantitative real-time PCR. Glycosaminoglycan (GAG) release was measured in the supernatants of BCE cultures. Results: All three BCP crystals significantly increased iCa(2+) content. OCP also induced iCa(2+) oscillations. Rate of BACs displaying iCa(2+) oscillations increased over time, with a peak after 20 min of stimulation. OCP-induced iCa(2+) oscillations involved both extracellular Ca2+ (eCa(2+)) influx and iCa(2+) stores. Indeed, OCP-induced iCa(2+) oscillations decreased rapidly in Ca2+-free medium. Both voltage- and non-voltage-dependent Ca2+ channels were involved in eCa(2+) influx. BCP crystal-induced variation in iCa(2+) content was associated with BCP crystal-induced cartilage matrix degradation. However, iCa(2+) was not associated with OCP crystal-induced mRNA expression of MMP-3, ADAMTS-4 or ADAMTS-5. Conclusion: BCP crystals can induce variation in iCa(2+) content and oscillations in articular chondrocytes. Furthermore. BCP crystal-induced changes in iCa(2+) content plays pivotal role in BCP catabolic effects on articular cartilage. (C) 2012 Osteoarthritis Research Society International. Published by Elsevier Ltd. All rights reserved

A new insight into the dissociating effect of strontium on bone resorption and formation.

Calcium phosphates are widely used as biomaterials and strontium (Sr) is known to have the ability to modify the bone balance towards osteosynthesis. In the present study we investigated the capacity of Sr-substituted sol-gel calcium phosphate to modify the expression of genes and proteins involved in extracellular matrix synthesis by primary bone cells. We first determined the most effective concentration of strontium using human primary bone cells. Sol-gel biphasic calcium phosphate (BCP) powders were then synthesised to obtain release of the optimal concentration of strontium. Finally, human osteoblasts obtained from explant cultures were cultured in the presence of sol-gel BCP, Sr-substituted BCP (5% Sr-substituted BCP, corresponding to a release of 5 × 10−5 M [Sr2+] under the culture conditions (BCP5%)) and medium containing strontium chloride (SrCl2). Viability, proliferation, cell morphology, protein production and protein activity were studied. We demonstrated that 5 × 10−5 M SrCl2 and BCP5% increased the expression of type I collagen and SERPINH1 mRNA and reduced the production of matrix metalloproteinases (MMP-1 and MMP-2) without modifying the levels of the tissue inhibitors of MMPs (TIMPs). Thus strontium has a positive effect on bone formation

Chitosan/hydroxyapatite hybrid scaffold for bone tissue engineering.

International audienceTo favor regeneration following critical bone defect, a combination of autologous bone graft and biomaterials is currently used. Major drawbacks of such techniques remain the availability of the autologous material and the second surgical site, inducing pain and morbidity