Preliminary evaluation of an osteochondral autograft, a prosthetic implant, and a biphasic absorbable implant for osteochondral reconstruction in a sheep model.

OBJECTIVE: To determine the ability of three implants to enhance the healing of osteochondral defects: (1) a biphasic construct composed of calcium phosphate (CaP) and chitosan/cellulosic polymer, (2) a titanium-polyurethane implant, and (3) an osteochondral autograft. STUDY DESIGN: Experimental study. ANIMALS: Ten adult female sheep. METHODS: In five sheep, an 8-mm diameter osteochondral defect was created on the medial femoral condyle of a stifle and filled with a synthetic titanium-polyurethane implant. In five sheep, a similar defect was filled with an osteochondral autograft, and the donor site was filled with a biphasic construct combining CaP granules and a chitosan/cellulosic polymer. Sheep were monitored daily for lameness. Stifle radiographs and MRI were evaluated at 20 weeks, prior to animals being humanely killed. Surgical sites were evaluated with histology, microcomputed tomography, and scanning electron microscopy. RESULTS: Clinical outcomes were satisfactory regardless of the tested biomaterials. All implants appeared in place on imaging studies. Osteointegration of prosthetic implants varied between sites, with limited ingrowth of new bone into the titanium structure. Autografts and biphasic constructs were consistently well integrated in subchondral bone. All autografts except one contained a cartilage surface, and all biphasic constructs except one partially restored hyaline cartilage surface. CONCLUSION: Biphasic constructs supported hyaline cartilage and subchondral bone regeneration, although restoration of the articular cartilage was incomplete. CLINICAL IMPACT: Biphasic constructs may provide an alternative treatment for osteochondral defects, offering a less invasive approach compared with autologous grafts and eliminating the requirement for a prosthetic implant.

TGF-ß1 and GDF5 Act Synergistically to Drive the Differentiation of Human Adipose Stromal Cells toward Nucleus Pulposus-like Cells.

Degenerative disc disease (DDD) primarily affects the central part of the intervertebral disc namely the nucleus pulposus (NP). DDD explains about 40% of low back pain and is characterized by massive cellular alterations that ultimately result in the disappearance of resident NP cells. Thus, repopulating the NP with regenerative cells is a promising therapeutic approach and remains a great challenge. The objectives of this study were to evaluate the potential of growth factor-driven protocols to commit human adipose stromal cells (hASCs) toward NP-like cell phenotype and the involvement of Smad proteins in this differentiation process. Here, we demonstrate that the transforming growth factor-ß1 and the growth differentiation factor 5 synergistically drive the nucleopulpogenic differentiation process. The commitment of the hASCs was robust and highly specific as attested by the expression of NP-related genes characteristic of young healthy human NP cells. In addition, the engineered NP-like cells secreted an abundant aggrecan and type II collagen rich extracellular matrix comparable with that of native NP. Furthermore, we demonstrate that these in vitro engineered cells survived, maintained their specialized phenotype and secretory activity after in vivo transplantation in nude mice subcutis. Finally, we provide evidence suggesting that the Smad 2/3 pathway mainly governed the acquisition of the NP cell molecular identity while the Smad1/5/8 pathway controlled the NP cell morphology. This study offers valuable insights for the development of biologically-inspired treatments for DDD by generating adapted and exhaustively characterized autologous regenerative cells.

Interpenetrated Si-HPMC/alginate hydrogels as a potential scaffold for human tissue regeneration.

Interpenetrated gels of biocompatible polysaccharides alginate and silanized hydroxypropyl methyl cellulose (Si-HPMC) have been studied in order to assess their potential as scaffolds for the regeneration of human tissues. Si-HPMC networks were formed by reduction of the pH to neutral and alginate networks were formed by progressive in situ release of Ca(2+). Linear and non-linear mechanical properties of the mixed gels at different polymer and calcium concentrations were compared with those of the corresponding single gels. The alginate/Si-HPMC gels were found to be stiffer than pure Si-HPMC gels, but weaker and more deformable than pure alginate gels. No significant difference was found for the maximum stress at rupture measured during compression for all these gels. The degrees of swelling or contraction in excess water at pH 7 as well as the release of Ca(2+) was measured as a function of time. Pure alginate gels contracted by as much as 50 % and showed syneresis, which was much reduced or even eliminated for mixed gels. The important release of Ca(2+) upon ageing for pure alginate gels was much reduced for the mixed gels. Furthermore, results of cytocompatibility assays indicated that there was no cytotoxicity of Si-HPMC/alginate hydrogels in 2D and 3D culture of human SW1353 cells. The results show that using interpenetrated Si-HPMC/alginate gels has clear advantages over the use of single gels for application in tissue regeneration.

Nanocomposite hydrogels for cartilage tissue engineering: mesoporous silica nanofibers interlinked with siloxane derived polysaccharide.

Injectable materials for mini-invasive surgery of cartilage are synthesized and thoroughly studied. The concept of these hybrid materials is based on providing high enough mechanical performances along with a good medium for chondrocytes proliferation. The unusual nanocomposite hydrogels presented herein are based on siloxane derived hydroxypropylmethylcellulose (Si-HPMC) interlinked with mesoporous silica nanofibers. The mandatory homogeneity of the nanocomposites is checked by fluorescent methods, which show that the silica nanofibres dispersion is realized down to nanometric scale, suggesting an efficient immobilization of the silica nanofibres onto the Si-HPMC scaffold. Such dispersion and immobilization are reached thanks to the chemical affinity between the hydrophilic silica nanofibers and the pendant silanolate groups of the Si-HPMC chains. Tuning the amount of nanocharges allows tuning the resulting mechanical features of these injectable biocompatible hybrid hydrogels. hASC stem cells and SW1353 chondrocytic cells viability is checked within the nanocomposite hydrogels up to 3 wt% of silica nanofibers.

Development of a DNA damage-induced senescence model in osteoarthritic chondrocytes.

Senescent cells (SnCs) have been described to accumulate in osteoarthritis (OA) joint tissues in response to injury, thereby participating in OA development and progression. However, clinical therapeutic approaches targeting SnCs using senolysis, although promising in preclinical OA models, have not yet proven their efficacy in patients with knee OA. This pitfall may be due to the lack of understanding of the mechanisms underlying chondrocyte senescence. Therefore, our study aimed to generate models of chondrocyte senescence. This study used etoposide, to induce DNA damage-related senescence or chronic exposure to IL-1ß to entail inflammation-related senescence in human OA chondrocytes. Several hallmarks of cellular senescence, such as cell cycle arrest, expression of cyclin-dependent kinase inhibitors, DNA damages, and senescence-associated secretory profile were evaluated. Chronic exposure to IL-1ß induces only partial expression of senescence markers and does not allow us to conclude on its ability to induce senescence in chondrocytes. On the other hand, etoposide treatment reliably induces DNA damage-related senescence in human articular chondrocytes evidenced by loss of proliferative capacity, DNA damage accumulation, and expression of some SASP components. Etoposide-induced senescence model may help investigate the initiation of cellular senescence in chondrocytes, and provide a useful model to develop therapeutic approaches to target senescence in OA.

Silanization of Chitosan and Hydrogel Preparation for Skeletal Tissue Engineering.

Tissue engineering is a multidisciplinary field that relies on the development of customized biomaterial to support cell growth, differentiation and matrix production. Toward that goal, we designed the grafting of silane groups onto the chitosan backbone (Si-chito) for the preparation of in situ setting hydrogels in association with silanized hydroxypropyl methylcellulose (Si-HPMC). Once functionalized, the chitosan was characterized, and the presence of silane groups and its ability to gel were demonstrated by rheology that strongly suggests the presence of silane groups. Throughout physicochemical investigations, the Si-HPMC hydrogels containing Si-chito were found to be stiffer with an injection force unmodified. The presence of chitosan within the hydrogel has demonstrated a higher adhesion of the hydrogel onto the surface of tissues. The results of cell viability assays indicated that there was no cytotoxicity of Si-chito hydrogels in 2D and 3D culture of human SW1353 cells and human adipose stromal cells, respectively. Moreover, Si-chito allows the transplantation of human nasal chondrocytes in the subcutis of nude mice while maintaining their viability and extracellular matrix secretory activity. To conclude, Si-chito mixed with Si-HPMC is an injectable, self-setting and cytocompatible hydrogel able to support the in vitro and in vivo viability and activity of hASC.

A Self-Setting Hydrogel of Silylated Chitosan and Cellulose for the Repair of Osteochondral Defects: From in vitro Characterization to Preclinical Evaluation in Dogs.

Articular cartilage (AC) may be affected by many injuries including traumatic lesions that predispose to osteoarthritis. Currently there is no efficient cure for cartilage lesions. In that respect, new strategies for regenerating AC are contemplated with interest. In this context, we aim to develop and characterize an injectable, self-hardening, mechanically reinforced hydrogel (Si-HPCH) composed of silanised hydroxypropymethyl cellulose (Si-HPMC) mixed with silanised chitosan. The in vitro cytocompatibility of Si-HPCH was tested using human adipose stromal cells (hASC). In vivo, we first mixed Si-HPCH with hASC to observe cell viability after implantation in nude mice subcutis. Si-HPCH associated or not with canine ASC (cASC), was then tested for the repair of osteochondral defects in canine femoral condyles. Our data demonstrated that Si-HPCH supports hASC viability in culture. Moreover, Si-HPCH allows the transplantation of hASC in the subcutis of nude mice while maintaining their viability and secretory activity. In the canine osteochondral defect model, while the empty defects were only partially filled with a fibrous tissue, defects filled with Si-HPCH with or without cASC, revealed a significant osteochondral regeneration. To conclude, Si-HPCH is an injectable, self-setting and cytocompatible hydrogel able to support the in vitro and in vivo viability and activity of hASC as well as the regeneration of osteochondral defects in dogs when implanted alone or with ASC.

Mesenchymal stem cells induce a weak immune response in the rat striatum after allo or xenotransplantation.

Mesenchymal stem cells (MSCs) have attracted attention for their potential use in regenerative medicine such as brain transplantation. As MSCs are considered to be hypoimmunogenic, transplanted MSCs should not trigger a strong host inflammatory response. To verify this hypothesis, we studied the brain immune response after transplantation of human or rat MSCs into the rat striatum and MSC fate at days 5, 14, 21 and 63 after transplantation. Flow cytometry analysis indicated that both MSCs express CD90 and human leucocyte antigen (MHC) class I, but no MHC class II molecules. They do not express CD45 or CD34 antigens. However, MSC phenotype varies with passage number. Human MSCs have mRNAs for interleukin (IL)-6, IL-8, IL-12, tumour necrosis factor (TNF)-alpha and TGF-beta(1), whereas rat MSCs express IL-6-, IL-10-, IL-12- and TGF-beta(1)-mRNAs. The quantification shows higher levels of mRNAs for the anti-inflammatory molecules IL-6 and TGF-beta(1) than for pro-inflammatory cytokines IL-8 and IL-12; ELISA analysis showed no IL-12 whereas TGF-beta(1) and IL-6 were detected. Transplant size did not significantly vary between 14 and 63 days after transplantation, indicating an absence of immune rejection of the grafts. Very few mast cells and moderate macrophage and microglial infiltrations, observed at day 5 remained stable until day 63 after transplantation in both rat and human MSC grafts. The observations of very few dendritic cells, T alphabeta-cells, and no T gammadelta-lymphocytes, all three being associated with Tp rejection in the brain, support the contention that MSCs are hypoimmunogenic. Our results suggest that MSCs are of great interest in regenerative medicine in a (xeno)transplantation setting.

Use of DNA combing for studying DNA replication in vivo in yeast and mammalian cells.

Plasticity is an inherent feature of chromosomal DNA replication in eukaryotes. Potential origins of DNA replication are made in excess, but are used (fired) in a partly stochastic, partly programmed manner throughout the S phase of the cell cycle. Since most origins have a firing efficiency below 50%, population-based analysis methods yield a cumulative picture of origin activity (obtained by accretion) that does not accurately describe how chromosomes are replicated in single cells. DNA combing is a method that allows the alignment on silanized glass coverslips, at high density and with uniform stretching, of single DNA molecules in the Mb range. If this DNA is isolated from cells that have been labelled with halogenated nucleotides (BrdU, CldU, IdU), it is possible to determine the density and position of replication origins as well as the rate and symmetry of fork progression, quantitatively and on single DNA molecules. This chapter will successively describe (a) the preparation ofsilanized coverslips, (b) the incorporation of halogenated nucleotides in newly synthesized DNA in yeast and mammalian cell lines, (c) the preparation and combing of genomic DNA, and finally (d) the acquisition and analysis of single-molecule images to extract salient features of replication dynamics.

A Cellulose/Laponite Interpenetrated Polymer Network (IPN) Hydrogel: Controllable Double-Network Structure with High Modulus.

Laponite XLS™, which is a synthetic clay of nanometric dimensions containing a peptizing agent, has been associated with silanized hydroxypropylmethylcellulose (Si-HPMC) to form, after crosslinking, a novel composite hydrogel. Different protocols of sample preparation were used, leading to different morphologies. A key result was that the storage modulus of Si-HPMC/XLS composite hydrogel could be increased ten times when compared to that of pure Si-HPMC hydrogel using 2 wt % of Laponite. The viscoelastic properties of the composite formulations indicated that chemical and physical network structures co-existed in the Si-HPMC/XLS composite hydrogel. Images that were obtained from confocal laser scanning microscopy using labelled Laponite XLS in the composite hydrogels show two co-continuous areas: red light area and dark area. The tracking of fluorescent microspheres motions in the composite formulations revealed that the red-light area was a dense structure, whereas the dark area was rather loose without aggregated Laponite. This novel special double-network structure facilitates the composite hydrogel to be an adapted biomaterial for specific tissue engineering. Unfortunately, cytotoxicity's assays suggested that XLS Laponites are cytotoxic at low concentration. This study validates that the hybrid interpenetrated network IPN hydrogel has a high modulus that has adapted for tissue engineering, but the cell's internalization of Laponites has to be controlled.

Laponite nanoparticle-associated silated hydroxypropylmethyl cellulose as an injectable reinforced interpenetrating network hydrogel for cartilage tissue engineering.

Articular cartilage is a connective tissue which does not spontaneously heal. To address this issue, biomaterial-assisted cell therapy has been researched with promising advances. The lack of strong mechanical properties is still a concern despite significant progress in three-dimensional scaffolds. This article's objective was to develop a composite hydrogel using a small amount of nano-reinforcement clay known as laponites. These laponites were capable of self-setting within the gel structure of the silated hydroxypropylmethyl cellulose (Si-HPMC) hydrogel. Laponites (XLG) were mixed with Si-HPMC to prepare composite hydrogels leading to the development of a hybrid interpenetrating network. This interpenetrating network increases the mechanical properties of the hydrogel. The in vitro investigations showed no side effects from the XLG regarding cytocompatibility or oxygen diffusion within the composite after cross-linking. The ability of the hybrid scaffold containing the composite hydrogel and chondrogenic cells to form a cartilaginous tissue in vivo was investigated during a 6-week implantation in subcutaneous pockets of nude mice. Histological analysis of the composite constructs revealed the formation of a cartilage-like tissue with an extracellular matrix containing glycosaminoglycans and collagens. Overall, this new hybrid construct demonstrates an interpenetrating network which enhances the hydrogel mechanical properties without interfering with its cytocompatibility, oxygen diffusion, or the ability of chondrogenic cells to self-organize in the cluster and produce extracellular matrix components. This composite hydrogel may be of relevance for the treatment of cartilage defects in a large animal model of articular cartilage defects. STATEMENT OF SIGNIFICANCE: Articular cartilage is a tissue that fails to heal spontaneously. To address this clinically relevant issue, biomaterial-assisted cell therapy is considered promising but often lacks adequate mechanical properties. Our objective was to develop a composite hydrogel using a small amount of nano reinforcement (laponite) capable of gelling within polysaccharide based self-crosslinking hydrogel. This new hybrid construct demonstrates an interpenetrating network (IPN) which enhances the hydrogel mechanical properties without interfering with its cytocompatibility, O2 diffusion and the ability of chondrogenic cells to self-organize in cluster and produce extracellular matrix components. This composite hydrogel may be of relevance for the treatment of cartilage defects and will now be considered in a large animal model of articular cartilage defects.

Sustained release of TGF-ß1 from biodegradable microparticles prepared by a new green process in CO2 medium.

The aim of this work was to encapsulate transforming growth factor ß1 (TGF-ß1) into PLGA microparticles for regenerative medicine applications. TGF-ß1 was firstly precipitated to ensure its stability during subsequent encapsulation within microparticles. A novel emulsification/extraction process in CO2 medium under mild conditions of pressure and temperature was used to encapsulate the protein. Interestingly, non-volatile injectable solvents, isosorbide dimethyl ether (DMI) and glycofurol (GF), were employed to precipitate the protein and to dissolve the polymer. Good encapsulation efficiency was obtained with preserved bioactivity of the protein. The microparticles were characterized in terms of size and zeta potential. In addition, the morphology and surface properties were determined using scanning electron microscopy (SEM) and atomic force microscopy (AFM) respectively. In vitro release study of the protein from microparticles was presented to assess the capacity of these systems to control the protein release. Moreover, cytotoxicity study was performed and showed an excellent cytocompatibility of the obtained microparticles. Thus, we described an effective and original process for TGF-ß1 encapsulation into PLGA microparticles. The obtained polymeric carriers could be used in many biomedical applications and were more specifically developed for cartilage regeneration.

Mesenchymal stem cell transplantation and DMEM administration in a 3NP rat model of Huntington's disease: morphological and behavioral outcomes.

Transplantation of mesenchymal stem cells (MSCs) may offer a viable treatment for Huntington's disease (HD). We tested the efficacy of MSC transplants to reduce deficits in a 3-nitropropionic acid (3NP) rat model of HD. Five groups of rats (Sham, 3NP, 3NP+vehicle, 3NP+TP(low), 3NP+TP(high)), were given PBS or 3NP intraperitoneally, twice daily for 42 days. On day 28, rats in all groups except Sham and 3NP, received intrastriatal injections of either 200,000 MSCs (TP(low)), 400,000 (TP(high)) MSCs or DMEM (VH, the vehicle for transplantation). MSCs survived 72 days without inducing a strong inflammatory response from the striatum. Behavioral sparing was observed on tests of supported-hindlimb-retraction, unsupported-hindlimb-retraction, visual paw placement and stepping ability for 3NP+TP(low) rats and on the unsupported-hindlimb-retraction and rotarod tasks for 3NP+VH rats. Relative to 3NP controls, all treated groups were protected from 3NP-induced enlargement of the lateral ventricles. In vitro, MSCs expressed transcripts for numerous neurotrophic factors. In vivo, increased striatal labeling in BDNF, collagen type-I and fibronectin (but not GDNF or CNTF) was observed in the brains of MSC-transplanted rats but not in DMEM-treated rats. In addition, none of the transplanted MSCs expressed neural phenotypes. These findings suggest that factors other than neuronal replacement underlie the behavioral sparing observed in 3NP rats after MSC transplantation.

Effects of Human Alpha-Synuclein A53T-A30P Mutations on SVZ and Local Olfactory Bulb Cell Proliferation in a Transgenic Rat Model of Parkinson Disease.

A transgenic Sprague Dawley rat bearing the A30P and A53T α-synuclein (α-syn) human mutations under the control of the tyrosine hydroxylase promoter was generated in order to get a better understanding of the role of the human α-syn mutations on the neuropathological events involved in the progression of the Parkinson's disease (PD). This rat displayed olfactory deficits in the absence of motor impairments as observed in most early PD cases. In order to investigate the role of the mutated α-syn on cell proliferation, we focused on the subventricular zone (SVZ) and the olfactory bulbs (OB) as a change of the proliferation could affect OB function. The effect on OB dopaminergic innervation was investigated. The human α-syn co-localized in TH-positive OB neurons. No human α-syn was visualized in the SVZ. A significant increase in resident cell proliferation in the glomerular but not in the granular layers of the OB and in the SVZ was observed. TH innervation was significantly increased within the glomerular layer without an increase in the size of the glomeruli. Our rat could be a good model to investigate the role of human mutated α-syn on the development of olfactory deficits.

Multiple lipid compartments slow vesicle contents release in lipases and serum.

Unilamellar vesicles or "liposomes" are commonly used as simple cell models and as drug delivery vehicles. A major limitation of unilamellar liposomes in these applications has been premature contents release in physiological environments. This premature release is likely due to enzyme degradation or protein insertion into the liposome membrane, which significantly increases the bilayer permeability. Encapsulating unilamellar liposomes within a second bilayer to form multicompartment "vesosomes" extends contents retention by 2 orders of magnitude by preventing enzymes and/or proteins from reaching the interior bilayers. The multicompartment structure of the vesosome can also allow for independent optimization of the interior compartments and exterior bilayer; however, just the bilayer-within-a-bilayer structure of the vesosome is sufficient to increase drug retention from minutes to hours. The vesosome is a better mimic of eukaryotic cell structure and demonstrates the benefits of multiple internal bilayer-enclosed compartments.