Rat Perforator and Skin Vessels Vascular Mapping: An Original Anatomical Study About 140 Vessels and Literature Review.

INTRODUCTION: Recent microsurgical reconstruction techniques benefit from the use of skin and perforator flaps that spare the donor sites. Studies on these skin flaps in rat models are numerous but there is currently no reference regarding the position of the perforators, their caliber, and the length of the vascular pedicles. METHODS: We performed an anatomical study on 10 Wistar rats and 140 vessels: cranial epigastric (CE), superficial inferior epigastric (SIE), lateral thoracic (LT), posterior thigh (PT), deep iliac circumflex (DCI) and posterior intercostal (PIC) vessels. The evaluation criteria were the external caliber, the length of the pedicle, and the position of the vessels reported on the skin surface. RESULTS: Data from the six perforator vascular pedicles are reported, with figures illustrating the orthonormal reference frame, the representation of the vessel's position, the cloud of points corresponding to the various measurements, and the average representation of the collected data. The analysis of the literature does not find similar studies; the different vascular pedicles are discussed as well as the limitations of our study: evaluation of cadaver specimen, presence of the very mobile panniculus carnosus, other perforator vessels not evaluated as well as the precise definition of perforating vessels. CONCLUSIONS: Our work describes the vascular calibers, pedicle lengths, and location of birth and arrival at the skin of the perforator vessels PT, DCI, PIC, LT, SIE, and CE in rat animal models. This work, without an equivalent in the literature, lays the foundation for future studies about flap perfusion, microsurgery, and super microsurgery learning.

Sustainable Biomass Lignin-Based Hydrogels: A Review on Properties, Formulation, and Biomedical Applications.

Different techniques have been developed to overcome the recalcitrant nature of lignocellulosic biomass and extract lignin biopolymer. Lignin has gained considerable interest owing to its attractive properties. These properties may be more beneficial when including lignin in the preparation of highly desired value-added products, including hydrogels. Lignin biopolymer, as one of the three major components of lignocellulosic biomaterials, has attracted significant interest in the biomedical field due to its biocompatibility, biodegradability, and antioxidant and antimicrobial activities. Its valorization by developing new hydrogels has increased in recent years. Furthermore, lignin-based hydrogels have shown great potential for various biomedical applications, and their copolymerization with other polymers and biopolymers further expands their possibilities. In this regard, lignin-based hydrogels can be synthesized by a variety of methods, including but not limited to interpenetrating polymer networks and polymerization, crosslinking copolymerization, crosslinking grafted lignin and monomers, atom transfer radical polymerization, and reversible addition-fragmentation transfer polymerization. As an example, the crosslinking mechanism of lignin-chitosan-poly(vinyl alcohol) (PVA) hydrogel involves active groups of lignin such as hydroxyl, carboxyl, and sulfonic groups that can form hydrogen bonds (with groups in the chemical structures of chitosan and/or PVA) and ionic bonds (with groups in the chemical structures of chitosan and/or PVA). The aim of this review paper is to provide a comprehensive overview of lignin-based hydrogels and their applications, focusing on the preparation and properties of lignin-based hydrogels and the biomedical applications of these hydrogels. In addition, we explore their potential in wound healing, drug delivery systems, and 3D bioprinting, showcasing the unique properties of lignin-based hydrogels that enable their successful utilization in these areas. Finally, we discuss future trends in the field and draw conclusions based on the findings presented.

Application of a Cryo-FIB-SEM-µRaman Instrument to Probe the Depth of Vitreous Ice in a Frozen Sample.

The development of instruments combining multiple characterization and imaging tools drove huge advances in material science, engineering, biology, and other related fields. Notably, the coupling of SEM with micro-Raman spectrometry (µRaman) provides the means for the correlation between structural and physicochemical properties at the surface, while dual focused ion beam (FIB)-scanning electron microscopes (SEMs) operating under cryogenic conditions (cryo-FIB-SEM) allow for the analysis of the ultrastructure of materials in situ and in their native environment. In cryo-FIB-SEM, rapid and efficient methods for assessing vitrification conditions in situ are required for the accurate investigation of the original structure of hydrated samples. This work reports for the first time the use of a cryo-FIB-SEM-µRaman instrument to efficiently assess the accuracy of cryo-fixation methods. Analyses were performed on plunge-freezed highly hydrated calcium phosphate cement (CPC) and a gelatin composite. By making a trench of a defined thickness with FIB, µRaman analyses were carried out at a specific depth within the frozen material. Results show that the µRaman signal is sensitive to the changes in the molecular structures of the aqueous phase and can be used to examine the depth of vitreous ice in frozen samples. The method presented in this work provides a reliable way to avoid imaging artifacts in cryo-FIB-SEM that are related to cryo-fixation and therefore constitutes great interest in the study of vitreous materials exhibiting high water content, regardless of the sample preparation method (i.e., by HPF, plunge freezing, and so on).

3D variable-density SPARKLING trajectories for high-resolution T2*-weighted magnetic resonance imaging.

We have recently proposed a new optimization algorithm called SPARKLING (Spreading Projection Algorithm for Rapid K-space sampLING) to design efficient compressive sampling patterns for magnetic resonance imaging (MRI). This method has a few advantages over conventional non-Cartesian trajectories such as radial lines or spirals: i) it allows to sample the k-space along any arbitrary density while the other two are restricted to radial densities and ii) it optimizes the gradient waveforms for a given readout time. Here, we introduce an extension of the SPARKLING method for 3D imaging by considering both stacks-of-SPARKLING and fully 3D SPARKLING trajectories. Our method allowed to achieve an isotropic resolution of 600 µm in just 45 seconds for T2∗-weighted ex vivo brain imaging at 7 Tesla over a field-of-view of 200 × 200 × 140 mm3 . Preliminary in vivo human brain data shows that a stack-of-SPARKLING is less subject to off-resonance artifacts than a stack-of-spirals.

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.

FitEllipsoid: a fast supervised ellipsoid segmentation plugin.

BACKGROUND: The segmentation of a 3D image is a task that can hardly be automatized in certain situations, notably when the contrast is low and/or the distance between elements is small. The existing supervised methods require a high amount of user input, e.g. delineating the domain in all planar sections. RESULTS: We present FitEllipsoid, a supervised segmentation code that allows fitting ellipsoids to 3D images with a minimal amount of interactions: the user clicks on a few points on the boundary of the object on 3 orthogonal views. The quantitative geometric results of the segmentation of ellipsoids can be exported as a csv file or as a binary image. The core of the code is based on an original computational approach to fit ellipsoids to point clouds in an affine invariant manner. The plugin is validated by segmenting a large number of 3D nuclei in tumor spheroids, allowing to analyze the distribution of their shapes. User experiments show that large collections of nuclei can be segmented with a high accuracy much faster than with more traditional 2D slice by slice delineation approaches. CONCLUSIONS: We designed a user-friendly software FitEllipsoid allowing to segment hundreds of ellipsoidal shapes in a supervised manner. It may be used directly to analyze biological samples, or to generate segmentation databases necessary to train learning algorithms. The algorithm is distributed as an open-source plugin to be used within the image analysis software Icy. We also provide a Matlab toolbox available with GitHub.

SPARKLING: variable-density k-space filling curves for accelerated T2* -weighted MRI.

PURPOSE: To present a new optimition-driven design of optimal k-space trajectories in the context of compressed sensing: Spreading Projection Algorithm for Rapid K-space sampLING (SPARKLING). THEORY: The SPARKLING algorithm is a versatile method inspired from stippling techniques that automatically generates optimized sampling patterns compatible with MR hardware constraints on maximum gradient amplitude and slew rate. These non-Cartesian sampling curves are designed to comply with key criteria for optimal sampling: a controlled distribution of samples (e.g., variable density) and a locally uniform k-space coverage. METHODS: Ex vivo and in vivo prospective T2* -weighted acquisitions were performed on a 7-Tesla scanner using the SPARKLING trajectories for various setups and target densities. Our method was compared to radial and variable-density spiral trajectories for high-resolution imaging. RESULTS: Combining sampling efficiency with compressed sensing, the proposed sampling patterns allowed up to 20-fold reductions in MR scan time (compared to fully sampled Cartesian acquisitions) for two-dimensional T2* -weighted imaging without deterioration of image quality, as demonstrated by our experimental results at 7 Tesla on in vivo human brains for a high in-plane resolution of 390 µm. In comparison to existing non-Cartesian sampling strategies, the proposed technique also yielded superior image quality. CONCLUSIONS: The proposed optimization-driven design of k-space trajectories is a versatile framework that is able to enhance MR sampling performance in the context of compressed sensing.

Application of Millifluidics to Encapsulate and Support Viable Human Mesenchymal Stem Cells in a Polysaccharide Hydrogel.

Human adipose-derived stromal cells (hASCs) are widely known for their immunomodulatory and anti-inflammatory properties. This study proposes a method to protect cells during and after their injection by encapsulation in a hydrogel using a droplet millifluidics technique. A biocompatible, self-hardening biomaterial composed of silanized-hydroxypropylmethylcellulose (Si-HPMC) hydrogel was used and dispersed in an oil continuous phase. Spherical particles with a mean diameter of 200 µm could be obtained in a reproducible manner. The viability of the encapsulated hASCs in the Si-HPMC particles was 70% after 14 days in vitro, confirming that the Si-HPMC particles supported the diffusion of nutrients, vitamins, and glucose essential for survival of the encapsulated hASCs. The combination of droplet millifluidics and biomaterials is therefore a very promising method for the development of new cellular microenvironments, with the potential for applications in biomedical engineering.

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.

Purification of the exopolysaccharide produced by Alteromonas infernus: identification of endotoxins and effective process to remove them.

Alteromonas infernus bacterium isolated from deep-sea hydrothermal vents can produce by fermentation a high molecular weight exopolysaccharide (EPS) called GY785. This EPS described as a new source of glycosaminoglycan-like molecule presents a great potential for pharmaceutical and biotechnological applications. However, this unusual EPS is secreted by a Gram-negative bacterium and can be therefore contaminated by endotoxins, in particular the lipopolysaccharides (LPS). Biochemical and chemical analyses of the LPS extracted from A. infernus membranes have shown the lack of the typical LPS architecture since 3-deoxy-D-manno-oct-2-ulopyranosonic acid (Kdo), glucosamine (GlcN), and phosphorylated monosaccharides were not present. Unlike for other Gram-negative bacteria, the results revealed that the outer membrane of A. infernus bacterium is most likely composed of peculiar glycolipids. Furthermore, the presence of these glycolipids was also detected in the EPS batches produced by fermentation. Different purification and chemical detoxification methods were evaluated to efficiently purify the EPS. Only the method based on a differential solubility of EPS and glycolipids in deoxycholate detergent showed the highest decrease in the endotoxin content. In contrast to the other tested methods, this new protocol can provide an effective method for obtaining endotoxin-free EPS without any important modification of its molecular weight, monosaccharide composition, and sulfate content.

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.

Micro-CT Analysis of Radiation-Induced Osteopenia and Bone Hypovascularization in Rat.

Treatment of carcinomas of the upper aerodigestive tract often requires external radiation therapy. However, radiation affects all the components of bone, with different degrees of sensitivity, and may produce severe side effects such as mandibular osteoradionecrosis (ORN). Intraosseous vascularization is thought to be decreased after irradiation, but its impact on total bone volume is still controversial. The aim of this study was to compare intraosseous vascularization, cortical bone thickness, and total bone volume in a rat model of ORN versus nonirradiated rats, using a micro-computed tomography (micro-CT) analysis after intracardiac injection of a contrast agent. The study was performed on 8-week-old Lewis 1A rats (n = 14). Eleven rats underwent external irradiation on the hind limbs by a single 80-Gy dose. Three rats did not receive irradiation and served as controls for statistical analysis. Eight weeks after the external irradiation, all the animals received a barium sulfate intracardiac injection under general anesthesia. All samples were analyzed with the micro-computed tomography system at a resolution of 5.5 µm. The images were later processed to create 3D reconstructions and study vascularization, bone volume, and cortical thickness. Data from irradiated and nonirradiated rats were compared using the Kruskal-Wallis test. No animal died after irradiation. Nineteen irradiated tibias and six nonirradiated tibias were included for micro-CT analysis. The vessel percentage was significantly lower in irradiated bones (p = 0.0001). The distance between the vessels, a marker of vascular destruction, was higher after irradiation (p = 0.001). The vessels were also more altered distally after irradiation (p = 0.028). Cortical thickness was severely decreased after irradiation, sometimes even reduced to zero. Both trabecular and cortical structures were destroyed after irradiation, with wide bone gaps. Finally, both total bone volume (p = 0.0001) and cortical thickness (p = 0.0001) were significantly decreased in irradiated tibias compared to nonirradiated tibias. These results led to multiple spontaneous fractures in the irradiated group, and the destruction of intraosseous vessels observed macroscopically with the radiographic preview. This study revealed the impact of radiation on intraosseous vasculature and cortical bone with a micro-CT analysis in a rat ORN model. Hypovascularization and osteopenia are consistent with the literature, contributing a morphological scale with high resolution. Visualization of the vasculature by micro-CT is an innovative technique to see the changes after radiation, and should help adjust bone tissue engineering in irradiated bone.

Development of a cyclosporin-A-induced immune tolerant rat model to test marrow allograft cell type effects on bone repair.

Bone repair is an important concept in tissue engineering, and the ability to repair bone in hypotrophic conditions such as that of irradiated bone, represents a challenge for this field. Previous studies have shown that a combination of bone marrow and (BCP) was effective to repair irradiated bone. However, the origin and role played by each cell type in bone healing still remains unclear. In order to track the grafted cells, the development of an animal model that is immunotolerant to an allograft of bone marrow would be useful. Furthermore, because the immune system interacts with bone turnover, it is of critical importance to demonstrate that immunosuppressive drugs do not interfere with bone repair. After a preliminary study of immunotolerance, cyclosporin-A was chosen to be used in immunosuppressive therapy. Ten rats were included to observe qualitative and quantitative bone repair 8 days and 6 weeks after the creation of bone defects. The defects were filled with an allograft of bone marrow alone or in association with BCP under immunosuppressive treatment (cyclosporin-A). The results showed that there was no significant interaction of cyclosporin-A with osseous regeneration. The use of this new immunotolerant rat model of bone marrow allograft in future studies will provide insight on how the cells within the bone marrow graft contribute to bone healing, especially in irradiated conditions.

Autologous Fat Grafting in the Breast: Critical Points and Technique Improvements.

BACKGROUND: Breast augmentation or reconstruction is a major challenge in esthetic and reconstructive surgery. While autologous fat grafting (AFG) provides a natural filler and seems easy to harvest, AFG in breast surgery is still problematic especially due to the high resorption rate associated with megavolume transfer. Despite this pending issue, there is growing interest in this method, which is becoming more and more widespread, as can be seen by the recent increase in the number of clinical studies. This review aims to highlight recent knowledge in the technique of AFG to the breast and recent refined procedures to improve fat viability and long-term success of the graft. METHODS: Clinical publications and trials of AFG to the breast from the past 5 years were examined. Attention was focused on the different AFG steps and the clinical outcomes, in order to highlight the strengths and weaknesses of the available protocols. RESULTS: Recent studies have concentrated on new techniques to improve fat viability and graft intake. However, all of these studies use different protocols at each step of the procedure. Furthermore, results may vary depending on the technique used for fat harvesting and processing. CONCLUSION: This review points out the recent advances in breast AFG techniques and their associated outcomes and complications. The bibliography has been carefully examined to reach a consensus so that recommendations could be made for each step of the technique with the aim of improving graft viability and long-term volume maintenance.

Svetlana a supervised segmentation classifier for Napari.

We present Svetlana (SuperVised sEgmenTation cLAssifier for NapAri), an open-source Napari plugin dedicated to the manual or automatic classification of segmentation results. A few recent software tools have made it possible to automatically segment complex 2D and 3D objects such as cells in biology with unrivaled performance. However, the subsequent analysis of the results is oftentimes inaccessible to non-specialists. The Svetlana plugin aims at going one step further, by allowing end-users to label the segmented objects and to pick, train and run arbitrary neural network classifiers. The resulting network can then be used for the quantitative analysis of biophysical phenoma. We showcase its performance through challenging problems in 2D and 3D and provide a comprehensive discussion on its strengths and limits.

Diagnostic value of VEGF in peri-implantitis and its correlation with titanium particles: A controlled clinical study.

OBJECTIVES: VEGF is prototypic marker of neovascularization, repeatedly proposed as intrinsic characteristic of peri-implantitis. This study aimed to assess pattern of VEGF in peri-implantitis, its correlation with titanium particles (TPs) and capacity as respective biomarker. MATERIAL AND METHODS: Pathological specificity of VEGF was assessed in peri-implant granulations using immunohistochemistry, periodontal granulations represented Ti-free positive controls. VEGF was correlated to TPs, identified using scanning electron microscopy coupled with dispersive x-ray spectrometry. Diagnostic accuracy, sensitivity and specificity of VEGF were estimated in PICF specimens from peri-implantitis, peri-implant mucositis (PIM) and healthy peri-implant tissues (HI) using machine learning algorithms. RESULTS: Peri-implantitis exhibited rich neovascular network with expressed density in contact zones toward neutrophil infiltrates without specific pattern variations around TPs, identified in all peri-implantitis specimens (mean particle size 8.9 ± 24.8 µm2; Ti-mass (%) 0.380 ± 0.163). VEGF was significantly more expressed in peri-implantitis (47,065 ± 24.2) compared to periodontitis (31,14 ± 9.15), and positively correlated with its soluble concentrations in PICF (p = 0.01). VEGF was positively correlated to all clinical endpoints and significantly increased in peri-implantitis compared to both PIM and HI, but despite high specificity (96%), its overall diagnostic capacity was average. Two patient clusters were identified in peri-implantitis, one with 8-fold higher VEGF values compared to HI, and second with lower values comparable to PIM. SIGNIFICANCE: VEGF accurately reflects neovascularization in peri-implantitis that was expressed in contact zones toward implant surface without specific histopathological patter variation around TPs. VEGF answered requests for biomarker of peri-implantitis but further research is necessary to decrypt its exact underlying cause.

Influence of physico-chemical properties of two lipoxin emulsion-loaded hydrogels on pre-polarized macrophages: a comparative analysis.

Inflammation, a crucial defense mechanism, must be rigorously regulated to prevent the onset of chronic inflammation and subsequent tissue damage. Specialized pro resolving mediators (SPMs) such as lipoxin A4 (LXA4) have demonstrated their ability to facilitate the resolution of inflammation by orchestrating a transition of M1 pro-inflammatory macrophages towards an anti-inflammatory M2 phenotype. However, the hydrophobic and chemically labile nature of LXA4 necessitates the development of a delivery system capable of preserving its integrity for clinical applications. In this study, two types of emulsion were formulated using different homogenization processes:mechanical overhead stirrer (MEB for blank Emulsion and MELX for LXA4 loaded-Emulsion) or Luer-lock syringes (SEB for blank Emulsion and SELX for LXA4 loaded-Emulsion)). Following characterization, including size and droplet morphology assessment by microscopy, the encapsulation efficiency (EE) was determined using liquid chromatography-tandem mass spectrometry (LC-MS/MS). To exert control over LXA4 release, these emulsions were embedded within silanized hyaluronic acid hydrogels. A comprehensive evaluation, encompassing gel time, swelling, and degradation profiles under acidic, basic, and neutral conditions, preceded the assessment of LXA4 cumulative release using LC-MS/MS. Physicochemical results indicate that H-MELX (Mechanical overhead stirrer LXA4 Emulsion loaded-Hydrogel) exhibits superior efficiency over H-SELX (Luer-lock syringes LXA4 Emulsion loaded-Hydrogel). While both formulations stimulated pro-inflammatory cytokine secretion and promoted a pro-inflammatory macrophage phenotype, LXA4 emulsion-loaded hydrogels displayed a diminished pro-inflammatory activity compared to blank emulsion-loaded hydrogels. These findings highlight the biological efficacy of LXA4 within both systems, with H-SELX outperforming H-MELX in terms of efficiency. To the best of our knowledge, this is the first successful demonstration of the biological efficacy of LXA4 emulsion-loaded hydrogel systems on macrophage polarization. These versatile H-MELX and H-SELX formulations can be customized to enhance their biological activity making them promising tools to promote the resolution of inflammation in diverse clinical applications.

Pharmacological modulation of human mesenchymal stem cell chondrogenesis by a chemically oversulfated polysaccharide of marine origin: potential application to cartilage regenerative medicine.

Mesenchymal stem cells (MSCs) are considered as an attractive source of cells for cartilage engineering due to their availability and capacity for expansion and multipotency. Differentiation of MSC into chondrocytes is crucial to successful cartilage regeneration and can be induced by various biological agents, including polysaccharides that participate in many biological processes through interactions with growth factors. Here, we hypothesize that growth factor-induced differentiation of MSC can be increased by chemically oversulfated marine polysaccharides. To test our hypothesis, human adipose tissue-derived MSCs (hATSCs) were cultured in pellets with transforming growth factor (TGF)-ß1-supplemented chondrogenic medium containing either the polysaccharide GY785 DR or its oversulfated isoform GY785 DRS. Chondrogenesis was monitored by the measurement of pellet volume, quantification of DNA, collagens, glycosaminoglycans (GAGs), and immunohistological staining. Our data revealed an increase in pellet volume, total collagens, and GAG production with GY785 DRS and chondrogenic medium. The enhanced chondrogenic differentiation of hATSC was further demonstrated by the increased expression of several chondrogenic markers by real-time reverse transcription-polymerase chain reaction. In addition, surface plasmon resonance analyses revealed that TGF-ß1 bound GY785 DRS with higher affinity compared to GY785 DR. In association with TGF-ß1, GY785 DRS was found to upregulate the phosphorylation of extracellular signal-regulated kinase 1/2, indicating that oversulfated polysaccharide affects the mitogen activated protein kinase signaling activity. These results demonstrate the upregulation of TGF-ß1-dependent stem cell chondrogenesis by a chemically oversulfated marine polysaccharide. This polysaccharide of marine origin is easily producible and therefore could be considered a promising additive to drive efficient and reliable MSC chondrogenesis for cartilage tissue engineering.

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.

The association of hydrogel and biphasic calcium phosphate in the treatment of dehiscence-type peri-implant defects: an experimental study in dogs.

Hydrogel polymers have many applications in regenerative medicine. The aim of this study in dogs was to investigate bone regeneration in dehiscence-type peri-implant defects created surgically and treated with (i) biphasic calcium phosphate (BCP) granules alone; (ii) a composite putty hydroxypropyl methylcellulose (HPMC)/BCP (MBCP/putty); and (iii) a polymer crosslinked membrane of silanized-HPMC (Si-HPMC/BCP) compared with empty controls. At 3 months, new bone formation was significantly more important in defects filled with HPMC/BCP or Si-HPMC/BCP compared with spontaneous healing in control (P = 0.032 and P = 0.046 respectively) and more substantial compared with BCP alone. Furthermore, new bone formation in direct contact with the implant surface was observed in all three groups treated with BCP. The addition of HPMC to the BCP granules may have enhanced the initial stability of the material within the blood clot in these large and complex osseous defects. The Si-HPMC hydrogel may also act as an occlusive membrane covering the BCP, which could improve the stability of the granules in the defect area. However, the crosslinking time of the Si-HPMC is too long for easy handling and the mechanical properties remain to be improved. The composite MBCP/putty appears to be a valuable bone-graft material in complex defects in periodontology and implantology. These encouraging results should now be confirmed in clinical studies.