Chitosan scaffolds for osteochondral tissue regeneration

Valorization of biological waste from insect-based food industry: Assessment of chitin and chitosan potential

Edible mealworms can be farmed to produce high-quality nutrients and proteins, useful as ingredients in human and animal foods. During this process biological waste is produced. This work explores the usage of the biological waste as source to produce chitin and chitosan with different potential applications. Different waste fractions were processed, and the feasibility of chitin isolation was assessed. Chitosan was derived, and films were fabricated and tested for intended uses. Data indicate that biopolymers with different properties can be obtained from multiple biological waste fractions. All samples show antibacterial activity, while chitosan films derived from molt show interesting properties for packaging purposes. Films also trigger the expression of anti-inflammatory phenotype markers in macrophage cells, which may be useful for tissue engineering implantation purposes. Altogether, biological waste from insect farming can be used to extract chitin and chitosan with different properties, and therefore, suitable for different applications.

Preparation and characterization of poly(3-hydroxybutyrate)/chitosan composite films using acetic acid as a solvent

Poly(3-hydroxybutyrate) and chitosan are among the most widely used polymers for biomedical applications due to their biocompatibility, renewability and low toxicity. The creation of composite materials based on biopolymers belonging to different classes makes it possible to overcome the disadvantages of each of the components and to obtain a material with specific properties. Solving this problem is associated with difficulties in the selection of conditions and solvents for obtaining the composite material. In our study, acetic acid was used as a common solvent for hydrophobic poly(3-hydroxybutyrate) and chitosan. Mechanical, thermal, physicochemical and surface properties of the composites and homopolymers were investigated. The composite films had less crystallinity and hydrophobicity than poly(3-hydroxybutyrate), and the addition of chitosan caused an increase in moisture absorption, a decrease in contact angle and changes in mechanical properties of the poly(3-hydroxybutyrate). The inclusion of varying amounts of chitosan controlled the properties of the composite, which will be important in the future for its specific biomedical applications.

Application of chitosan with different molecular weights in cartilage tissue engineering

Cartilage tissue engineering involves the invention of novel implantable cartilage replacement materials to help heal cartilage injuries that do not heal themselves, aiming to overcome the shortcomings of current clinical cartilage treatments. Chitosan has been widely used in cartilage tissue engineering because of its similar structure to glycine aminoglycan, which is widely distributed in connective tissues. The molecular weight, as an important structural parameter of chitosan, affects not only the method of chitosan composite scaffold preparation but also the effect on cartilage tissue healing. Thus, this review identifies methods for the preparation of chitosan composite scaffolds with low, medium and high molecular weights, as well as a range of chitosan molecular weights appropriate for cartilage tissue repair, by summarizing the application of different molecular weights of chitosan in cartilage repair in recent years.

Chitosan and its derivatives in 3D/4D (bio) printing for tissue engineering and drug delivery applications

Tissue engineering research has undergone to a revolutionary improvement, thanks to technological advancements, such as the introduction of bioprinting technologies. The ability to develop suitable customized biomaterial inks/bioinks, with excellent printability and ability to promote cell proliferation and function, has a deep impact on such improvements. In this context, printing inks based on chitosan and its derivatives have been instrumental. Thus, the current review aims at providing a comprehensive overview on chitosan-based materials as suitable inks for 3D/4D (bio)printing and their applicability in creating advanced drug delivery platforms and tissue engineered constructs. Furthermore, relevant strategies to improve the mechanical and biological performances of this biomaterial are also highlighted.

Advancements and Utilizations of Scaffolds in Tissue Engineering and Drug Delivery

The drug development process requires a thorough understanding of the scaffold and its three-dimensional structure. Scaffolding is a technique for tissue engineering and the formation of contemporary functioning tissues. Tissue engineering is sometimes referred to as regenerative medicine. They also ensure that drugs are delivered with precision. Information regarding scaffolding techniques, scaffolding kinds, and other relevant facts, such as 3D nanostructuring, are discussed in depth in this literature. They are specific and demonstrate localized action for a specific reason. Scaffold's acquisition nature and flexibility make it a new drug delivery technology with good availability and structural parameter management.

Design strategies for composite matrix and multifunctional polymeric scaffolds with enhanced bioactivity for bone tissue engineering

Over the past few decades, various bioactive material-based scaffolds were investigated and researchers across the globe are actively involved in establishing a potential state-of-the-art for bone tissue engineering applications, wherein several disciplines like clinical medicine, materials science, and biotechnology are involved. The present review article's main aim is to focus on repairing and restoring bone tissue defects by enhancing the bioactivity of fabricated bone tissue scaffolds and providing a suitable microenvironment for the bone cells to fasten the healing process. It deals with the various surface modification strategies and smart composite materials development that are involved in the treatment of bone tissue defects. Orthopaedic researchers and clinicians constantly focus on developing strategies that can naturally imitate not only the bone tissue architecture but also its functional properties to modulate cellular behaviour to facilitate bridging, callus formation and osteogenesis at critical bone defects. This review summarizes the currently available polymeric composite matrices and the methods to improve their bioactivity for bone tissue regeneration effectively.

Applications of Chitosan in Surgical and Post-Surgical Materials

The continuous advances in surgical procedures require continuous research regarding materials with surgical applications. Biopolymers are widely studied since they usually provide a biocompatible, biodegradable, and non-toxic material. Among them, chitosan is a promising material for the development of formulations and devices with surgical applications due to its intrinsic bacteriostatic, fungistatic, hemostatic, and analgesic properties. A wide range of products has been manufactured with this polymer, including scaffolds, sponges, hydrogels, meshes, membranes, sutures, fibers, and nanoparticles. The growing interest of researchers in the use of chitosan-based materials for tissue regeneration is obvious due to extensive research in the application of chitosan for the regeneration of bone, nervous tissue, cartilage, and soft tissues. Chitosan can serve as a substance for the administration of cell-growth promoters, as well as a support for cellular growth. Another interesting application of chitosan is hemostasis control, with remarkable results in studies comparing the use of chitosan-based dressings with traditional cotton gauzes. In addition, chitosan-based or chitosan-coated surgical materials provide the formulation with antimicrobial activity that has been highly appreciated not only in dressings but also for surgical sutures or meshes.

Recombinant Proteins-Based Strategies in Bone Tissue Engineering

The increase in fracture rates and/or problems associated with missing bones due to accidents or various pathologies generates socio-health problems with a very high impact. Tissue engineering aims to offer some kind of strategy to promote the repair of damaged tissue or its restoration as close as possible to the original tissue. Among the alternatives proposed by this specialty, the development of scaffolds obtained from recombinant proteins is of special importance. Furthermore, science and technology have advanced to obtain recombinant chimera’s proteins. This review aims to offer a synthetic description of the latest and most outstanding advances made with these types of scaffolds, particularly emphasizing the main recombinant proteins that can be used to construct scaffolds in their own right, i.e., not only to impregnate them, but also to make scaffolds from their complex structure, with the purpose of being considered in bone regenerative medicine in the near future.

Gradient scaffolds for osteochondral tissue engineering and regeneration

The tissue engineering approach for repairing osteochondral (OC) defects involves the fabrication of a biological tissue scaffold that mimics the physiological properties of natural OC tissue (e.g., the gradient transition between the cartilage surface and the subchondral bone). The OC tissue scaffolds described in many research studies exhibit a discrete gradient (e.g., a biphasic or tri/multiphasic structure) or a continuous gradient to mimic OC tissue attributes such as biochemical composition, structure, and mechanical properties. One advantage of a continuous gradient scaffold over biphasic or tri/multiphasic tissue scaffolds is that it more closely mimics natural OC tissue since there is no distinct interface between each layer. Although research studies to this point have yielded good results related to OC regeneration with tissue scaffolds, differences between engineered scaffolds and natural OC tissue remain; due to these differences, current clinical therapies to repair OC defects with engineered scaffolds have not been successful. This paper provides an overview of both discrete and continuous gradient OC tissue scaffolds in terms of cell type, scaffold material, microscale structure, mechanical properties, fabrication methods, and scaffold stimuli. Fabrication of gradient scaffolds with three-dimensional (3D) printing is given special emphasis due to its ability to accurately control scaffold pore geometry. Moreover, the application of computational modeling in OC tissue engineering is considered; for example, efforts to optimize the scaffold structure, mechanical properties, and physical stimuli generated within the scaffold-bioreactor system to predict tissue regeneration are considered. Finally, challenges associated with the repair of OC defects and recommendations for future directions in OC tissue regeneration are proposed.

Challenges and Innovations in Osteochondral Regeneration: Insights from Biology and Inputs from Bioengineering toward the Optimization of Tissue Engineering Strategies

Due to the extremely high incidence of lesions and diseases in aging population, it is critical to put all efforts into developing a successful implant for osteochondral tissue regeneration. Many of the patients undergoing surgery present osteochondral fissure extending until the subchondral bone (corresponding to a IV grade according to the conventional radiographic classification by Berndt and Harty). Therefore, strategies for functional tissue regeneration should also aim at healing the subchondral bone and joint interface, besides hyaline cartilage. With the ambition of contributing to solving this problem, several research groups have been working intensively on the development of tailored implants that could promote that complex osteochondral regeneration. These implants may be manufactured through a wide variety of processes and use a wide variety of (bio)materials. This review aimed to examine the state of the art regarding the challenges, advantages, and drawbacks of the current strategies for osteochondral regeneration. One of the most promising approaches relies on the principles of additive manufacturing, where technologies are used that allow for the production of complex 3D structures with a high level of control, intended and predefined geometry, size, and interconnected pores, in a reproducible way. However, not all materials are suitable for these processes, and their features should be examined, targeting a successful regeneration.

Enhancement of in vivo supraspinatus tendon-to-bone healing with an alginate-chitin scaffold and rhBMP-2

INTRODUCTION

Rotator cuff disorders present a high retear rate despite advances in surgical treatment. Tissue engineering could therefore be interesting in order to try to enhance a more biological repair. RhBMP-2 is one of the most osteogenic growth factors and it also induces the formation of collagen type I. However, it has a short half-life and in order to get a more stable release over time it could be integrated in a more slowly degradable carrier, such as an alginate-chitin scaffold. The aim of this study was to investigate the role of the alginate-chitin scaffold alone and in combination with different concentrations of rhBMP-2 when applied on chronic rotator cuff lesions in a rat model.

MATERIALS AND METHODS

We performed an experimental study with 80 Sprague-Dawley rats, 8 months old, with a chronic rupture of the supraspinatus tendon that was repaired with a modified Mason Allen suture. A scaffold was applied over the suture and 4 groups were obtained; suture (S) only suture, double control (DC) alginate and chitin scaffold, single sample (SS) scaffold of alginate with rhBMP-2 (20 µg rhBMP-2) and chitin, double sample (DS) a scaffold containing alginate with rhBMP-2 and chitin with rhBMP-2 (40 µg rhBMP-2). Macroscopic, histological and biomechanical studies were performed at 4 months after reparation.

RESULTS

The modified Åström and Rausing's histological scale (the higher the score the worse outcome, 0 points=native tendon) was applied: S got 52 points compared to DC 30 (p = 0,034), SS 22 (p = 0,009) and DS 16 (p = 0,010). Biomechanically the maximum load was highest in DC (63,05 N), followed by DS (61,60 N), SS (52,35 N) and S (51,08), p = 0,025 DS vs S. As to the elastic constant a higher value was obtained in DC (16,65), DS (12,55) and SS (12,20) compared to S (9,33), p = 0,009 DC vs S and 0,034 DS vs S.

CONCLUSIONS

The alginate-chitin scaffold seems to promote a more biological response after the reparation of a chronic rotator cuff lesion. Its effect is further enhanced by the addition of rhBMP-2 since the osteotendinous junction is more native-like and has better biomechanical properties.

Evaluation of Glycerylphytate Crosslinked Semi- and Interpenetrated Polymer Membranes of Hyaluronic Acid and Chitosan for Tissue Engineering

In the present study, semi- and interpenetrated polymer network (IPN) systems based on hyaluronic acid (HA) and chitosan using ionic crosslinking of chitosan with a bioactive crosslinker, glycerylphytate (G1Phy), and UV irradiation of methacrylate were developed, characterized and evaluated as potential supports for tissue engineering. Semi- and IPN systems showed significant differences between them regarding composition, morphology, and mechanical properties after physicochemical characterization. Dual crosslinking process of IPN systems enhanced HA retention and mechanical properties, providing also flatter and denser surfaces in comparison to semi-IPN membranes. The biological performance was evaluated on primary human mesenchymal stem cells (hMSCs) and the systems revealed no cytotoxic effect. The excellent biocompatibility of the systems was demonstrated by large spreading areas of hMSCs on hydrogel membrane surfaces. Cell proliferation increased over time for all the systems, being significantly enhanced in the semi-IPN, which suggested that these polymeric membranes could be proposed as an effective promoter system of tissue repair. In this sense, the developed crosslinked biomimetic and biodegradable membranes can provide a stable and amenable environment for hMSCs support and growth with potential applications in the biomedical field.

The Use of Nanomaterials in Tissue Engineering for Cartilage Regeneration; Current Approaches and Future Perspectives

The repair and regeneration of articular cartilage represent important challenges for orthopedic investigators and surgeons worldwide due to its avascular, aneural structure, cellular arrangement, and dense extracellular structure. Although abundant efforts have been paid to provide tissue-engineered grafts, the use of therapeutically cell-based options for repairing cartilage remains unsolved in the clinic. Merging a clinical perspective with recent progress in nanotechnology can be helpful for developing efficient cartilage replacements. Nanomaterials, < 100 nm structural elements, can control different properties of materials by collecting them at nanometric sizes. The integration of nanomaterials holds promise in developing scaffolds that better simulate the extracellular matrix (ECM) environment of cartilage to enhance the interaction of scaffold with the cells and improve the functionality of the engineered-tissue construct. This technology not only can be used for the healing of focal defects but can also be used for extensive osteoarthritic degenerative alterations in the joint. In this review paper, we will emphasize the recent investigations of articular cartilage repair/regeneration via biomaterials. Also, the application of novel technologies and materials is discussed.

A Composite Chitosan-Reinforced Scaffold Fails to Provide Osteochondral Regeneration

Several biomaterials have recently been developed to address the challenge of osteochondral regeneration. Among these, chitosan holds promises both for cartilage and bone healing. The aim of this in vivo study was to evaluate the regeneration potential of a novel hybrid magnesium-doped hydroxyapatite (MgHA), collagen, chitosan-based scaffold, which was tested in a sheep model to ascertain its osteochondral regenerative potential, and in a rabbit model to further evaluate its ability to regenerate bone tissue. Macroscopic, microtomography, histology, histomorphometry, and immunohistochemical analysis were performed. In the sheep model, all analyses did not show significant differences compared to untreated defects (p > 0.05), with no evidence of cartilage and subchondral bone regeneration. In the rabbit model, this bone scaffold provided less ability to enhance tissue healing compared with a commercial bone scaffold. Moreover, persistence of scaffold material and absence of integration with connective tissue around the scaffolds were observed. These results raised some concerns about the osteochondral use of this chitosan composite scaffold, especially for the bone layer. Further studies are needed to explore the best formulation of chitosan-reinforced composites for osteochondral treatment.

Integration of C-type natriuretic peptide gene-modified bone marrow mesenchymal stem cells with chitosan/silk fibroin scaffolds as a promising strategy for articular cartilage regeneration

The treatment of articular cartilage defects has become a major clinical concern. Currently, additional efforts are necessary to develop effective methods to cure this disease. In this work, we combined gene therapy with tissue engineering methods to test their effect on cartilage repair. In in vitro experiments, we obtained C-type natriuretic peptide (CNP) gene-modified bone marrow-derived mesenchymal stem cells (BMSCs) by transfection with recombinant adenovirus containing the CNP gene and revealed that CNP gene-modified BMSCs had good chondrogenic differentiation ability. By the freeze-drying method, we successfully synthesized a chitosan/silk fibroin (CS/SF) porous scaffold, which had a suitable aperture size for chondrogenesis. Then, we loaded CNP gene-modified BMSCs onto CS/SF scaffolds and tested their effect on repairing full-thickness cartilage defects in rat joints. The gross morphology and histology examination results showed that the composite of the CNP gene-modified BMSCs and CS/SF scaffolds had better repair effects than those of the other three groups at each time point. Additionally, compared to the group with BMSCs and scaffolds, we found that there was more cartilage matrix in the CNP gene-modified BMSCs and CS/SF scaffolds group. Data obtained in the present study suggest that the composite of CNP gene-modified BMSCs and CS/SF scaffolds represent promising strategies for repairing focal cartilage lesions.

Novel alginate biphasic scaffold for osteochondral regeneration: an in vivo evaluation in rabbit and sheep models

Current therapeutic strategies for osteochondral restoration showed a limited regenerative potential. In fact, to promote the growth of articular cartilage and subchondral bone is a real challenge, due to the different functional and anatomical properties. To this purpose, alginate is a promising biomaterial for a scaffold-based approach, claiming optimal biocompatibility and good chondrogenic potential. A previously developed mineralized alginate scaffold was investigated in terms of the ability to support osteochondral regeneration both in a large and medium size animal model. The results were evaluated macroscopically and by microtomography, histology, histomorphometry, and immunohistochemical analysis. No evidence of adverse or inflammatory reactions was observed in both models, but limited subchondral bone formation was present, together with a slow scaffold resorption time.The implantation of this biphasic alginate scaffold provided partial osteochondral regeneration in the animal model. Further studies are needed to evaluate possible improvement in terms of osteochondral tissue regeneration for this biomaterial.

Chitosan composite scaffolds for articular cartilage defect repair: a review

Articular cartilage (AC) defects lack the ability to self-repair due to their avascular nature and the declined mitotic ability of mature chondrocytes. To date, cartilage tissue engineering using implanted scaffolds containing cells or growth factors is the most promising defect repair method. Scaffolds for cartilage tissue engineering have been comprehensively researched. As a promising scaffold biomaterial for AC defect repair, the properties of chitosan are summarized in this review. Strategies to composite chitosan with other materials, such as polymers (including collagen, gelatin, alginate, silk fibroin, poly-caprolactone, and poly-lactic acid) and bioceramics (including calcium phosphate, calcium polyphosphate, and hydroxyapatite) are presented. Methods to manufacture three-dimensional porous structures to support cell attachment and nutriment exchange have also been included.

Properties of chitosan/polymer and chitosan/bioceramic composite scaffolds for articular cartilage defect repair are reviewed.

Advances for Treatment of Knee OC Defects

Osteochondral (OC) defects are prevalent among young adults and are notorious for being unable to heal. Although they are traumatic in nature, they often develop silently. Detection of many OC defects is challenging, despite the criticality of early care. Current repair approaches face limitations and cannot provide regenerative or long-standing solution. Clinicians and researchers are working together in order to develop approaches that can regenerate the damaged tissues and protect the joint from developing osteoarthritis. The current concepts of tissue engineering and regenerative medicine, which have brought many promising applications to OC management, are overviewed herein. We will also review the types of stem cells that aim to provide sustainable cell sources overcoming the limitation of autologous chondrocyte-based applications. The various scaffolding materials that can be used as extracellular matrix mimetic and having functional properties similar to the OC unit are also discussed.

Enhanced biological fixation of ligaments to bone tissues utilizing chitin fabrics

In ligament reconstruction involving anterior cruciate ligament surgery, biological fixation between the transferred ligament and bone tissue is critical for achieving successful outcomes. Here, we administered chitin fabrics into the bone tunnels and evaluated their efficacy in promoting biological fixation. An animal model on the rat's patellar ligament was employed. First, bone tunnels were created in the lateral condyle of the femur. The ligament was then separated from the tibial tuberosity, and half was inserted into the tunnel and fixed with the use of end button. Animals in the experimental group were treated with microfiber nonwoven chitin fabric, whereas control animals received no treatment. Specimens were collected at 2, 4, and 6 weeks after surgery, and the fixation strength was measured by mechanical tests. Histological sections were prepared from samples prepared 4 weeks after surgery, and the diameter of bone tunnel and the width ratio of collagenous tissue in the bone tunnel were measured. Administration of chitin significantly increased the mean fixation strength at 4 and 6 weeks after surgery. Furthermore, chitin also promoted bone formation in the bone tunnel and increased the density of collagen fibers. Thus, microfiber nonwoven chitin fabric enhanced the biological fixation of the ligament to the bone tissue. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 2355-2360, 2018.

Effect of a Rapidly Degrading Presolidified 10 kDa Chitosan/Blood Implant and Subchondral Marrow Stimulation Surgical Approach on Cartilage Resurfacing in a Sheep Model

Objective This study tested the hypothesis that presolidified chitosan-blood implants are retained in subchondral bone channels perforated in critical-size sheep cartilage defects, and promote bone repair and hyaline-like cartilage resurfacing versus blood implant. Design Cartilage defects (10 × 10 mm) with 3 bone channels (1 drill, 2 Jamshidi biopsy, 2 mm diameter), and 6 small microfracture holes were created bilaterally in n = 11 sheep knee medial condyles. In one knee, 10 kDa chitosan-NaCl/blood implant (presolidified using recombinant factor VIIa or tissue factor), was inserted into each drill and Jamshidi hole. Contralateral knee defects received presolidified whole blood clot. Repair tissues were assessed histologically, biochemically, biomechanically, and by micro-computed tomography after 1 day ( n = 1) and 6 months ( n = 10). Results Day 1 defects showed a 60% loss of subchondral bone plate volume fraction along with extensive subchondral hematoma. Chitosan implant was resident at day 1, but had no effect on any subsequent repair parameter compared with blood implant controls. At 6 months, bone defects exhibited remodeling and hypomineralized bone repair and were partly resurfaced with tissues containing collagen type II and scant collagen type I, 2-fold lower glycosaminoglycan and fibril modulus, and 4.5-fold higher permeability compared with intact cartilage. Microdrill holes elicited higher histological ICRS-II overall assessment scores than Jamshidi holes (50% vs. 30%, P = 0.041). Jamshidi biopsy holes provoked sporadic osteonecrosis in n = 3 debrided condyles. Conclusions Ten kilodalton chitosan was insufficient to improve repair. Microdrilling is a feasible subchondral marrow stimulation surgical approach with the potential to elicit poroelastic tissues with at least half the compressive modulus as intact articular cartilage.

Bioengineering of Humanized Bone Marrow Microenvironments in Mouse and Their Visualization by Live Imaging

Human hematopoietic stem cells (HSCs) reside in the bone marrow (BM) niche, an intricate, multifactorial network of components producing cytokines, growth factors, and extracellular matrix. The ability of HSCs to remain quiescent, self-renew or differentiate, and acquire mutations and become malignant depends upon the complex interactions they establish with different stromal components. To observe the crosstalk between human HSCs and the human BM niche in physiological and pathological conditions, we designed a protocol to ectopically model and image a humanized BM niche in immunodeficient mice. We show that the use of different cellular components allows for the formation of humanized structures and the opportunity to sustain long-term human hematopoietic engraftment. Using two-photon microscopy, we can live-image these structures in situ at the single-cell resolution, providing a powerful new tool for the functional characterization of the human BM microenvironment and its role in regulating normal and malignant hematopoiesis.

Repair of rotator cuff injuries using different composites

AIM

Rotator cuff repairs have shown a high level of re-ruptures. It is hypothesised that the use of rhBMP-2 in a carrier could improve the biomechanical and histological properties of the repair.

MATERIAL AND METHODS

Controlled experimental study conducted on 40 rats with section and repair of the supraspinatus tendon and randomisation to one of five groups: Group 1 (control) only suture; Group 2 (double control), suture and alginate-chitin carrier; Group 3 (alginate-control), the rhBMP-2 was added to the alginate; Group 4 (chitin-control) application of the rhBMP-2 to the chitin, and Group 5 (double sample): The two components of the carrier (alginate and chitin) have rhBMP-2. A biomechanical and histological analysis was performed at 4 weeks.

RESULTS

A gap was observed in all cases 4 weeks after supraspinatus detachment. The re-rupture rate was 7.5%, with 20% of them in the control-alginate Group. Histologically the best results were obtained in the double sample group: 4.5 (3.3-5.0). Double sample were also able to support higher loads to failure: 62.9N (59.8 to 69.4) with lower rigidity 12.7 (9.7 to 15.9).

CONCLUSIONS

The use of alginate-chitin carrier with rhBMP-2 improves the biomechanical and histological properties of the repair site in a chronic rotator cuff tear.

Improved cartilage regeneration by implantation of acellular biomaterials after bone marrow stimulation: a systematic review and meta-analysis of animal studies

Microfracture surgery may be applied to treat cartilage defects. During the procedure the subchondral bone is penetrated, allowing bone marrow-derived mesenchymal stem cells to migrate towards the defect site and form new cartilage tissue. Microfracture surgery generally results in the formation of mechanically inferior fibrocartilage. As a result, this technique offers only temporary clinical improvement. Tissue engineering and regenerative medicine may improve the outcome of microfracture surgery. Filling the subchondral defect with a biomaterial may provide a template for the formation of new hyaline cartilage tissue. In this study, a systematic review and meta-analysis were performed to assess the current evidence for the efficacy of cartilage regeneration in preclinical models using acellular biomaterials implanted after marrow stimulating techniques (microfracturing and subchondral drilling) compared to the natural healing response of defects. The review aims to provide new insights into the most effective biomaterials, to provide an overview of currently existing knowledge, and to identify potential lacunae in current studies to direct future research. A comprehensive search was systematically performed in PubMed and EMBASE (via OvidSP) using search terms related to tissue engineering, cartilage and animals. Primary studies in which acellular biomaterials were implanted in osteochondral defects in the knee or ankle joint in healthy animals were included and study characteristics tabulated (283 studies out of 6,688 studies found). For studies comparing non-treated empty defects to defects containing implanted biomaterials and using semi-quantitative histology as outcome measure, the risk of bias (135 studies) was assessed and outcome data were collected for meta-analysis (151 studies). Random-effects meta-analyses were performed, using cartilage regeneration as outcome measure on an absolute 0–100% scale. Implantation of acellular biomaterials significantly improved cartilage regeneration by 15.6% compared to non-treated empty defect controls. The addition of biologics to biomaterials significantly improved cartilage regeneration by 7.6% compared to control biomaterials. No significant differences were found between biomaterials from natural or synthetic origin or between scaffolds, hydrogels and blends. No noticeable differences were found in outcome between animal models. The risk of bias assessment indicated poor reporting for the majority of studies, impeding an assessment of the actual risk of bias. In conclusion, implantation of biomaterials in osteochondral defects improves cartilage regeneration compared to natural healing, which is further improved by the incorporation of biologics.

Assessment of degradation and biocompatibility of electrodeposited chitosan and chitosan-carbon nanotube tubular implants

Designing three-dimensional tubular materials made of chitosan is still a challenging task. Availability of such forms is highly desired by tissue engineering, especially peripheral nerve tissue engineering. Aiming at this problem, we use an electrodeposition phenomenon in order to obtain chitosan and chitosan-carbon nanotube hydrogel tubular implants. The in vitro biocompatibility of the fabricated structures is assessed using a mouse hippocampal cell line (mHippoE-18). As both implants do not induce significant cytotoxicity, they are next subjected to in vitro degradation studies in the environment simulating in vivo conditions for specified periods of time: 7, 14, and 28 days. The mass loss of implants indicates their stability at the tested time period; therefore, the materials are subcutaneously implanted in Sprague Dawley rats. The explants are collected after 7, 14, and 28 days. The assessment of composition and changes in tissues surrounding the implanted materials is made in respect to surrounding tissue thickness as well as the number of blood vessels, macrophages, lymphocytes, and neutrophils. No symptoms of acute inflammation are noticed at any point in time. The observed regular healing process allows concluding that both chitosan and chitosan-carbon hydrogel tubular implants are biocompatible with high application potential in tissue engineering. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 2701-2711, 2016.

Multi-layered collagen-based scaffolds for osteochondral defect repair in rabbits

INTRODUCTION

Identification of a suitable treatment for osteochondral repair presents a major challenge due to existing limitations and an urgent clinical need remains for an off-the-shelf, low cost, one-step approach. A biomimetic approach, where the biomaterial itself encourages cellular infiltration from the underlying bone marrow and provides physical and chemical cues to direct these cells to regenerate the damaged tissue, provides a potential solution. To meet this need, a multi-layer collagen-based osteochondral defect repair scaffold has been developed in our group.

AIM

The objective of this study was to assess the in vivo response to this scaffold and determine its ability to direct regenerative responses in each layer in order to repair osteochondral tissue in a critical-sized defect in a rabbit knee.

METHODS

Multi-layer scaffolds, consisting of a bone layer composed of type I collagen (bovine source) and hydroxyapatite (HA), an intermediate layer composed of type I and type II collagen and HA; and a superficial layer composed of type I and type II collagen (porcine source) and hyaluronic acid (HyA), were implanted into critical size (3 × 5 mm) osteochondral defects created in the medial femoral condyle of the knee joint of New Zealand white rabbits and compared to an empty control group. Repair was assessed macroscopically, histologically and using micro-CT analysis at 12 weeks post implantation.

RESULTS

Analysis of repair tissue demonstrated an enhanced macroscopic appearance in the multi-layer scaffold group compared to the empty group. In addition, diffuse host cellular infiltration in the scaffold group resulted in tissue regeneration with a zonal organisation, with repair of the subchondral bone, formation of an overlying cartilaginous layer and evidence of an intermediate tidemark.

CONCLUSION

These results demonstrate the potential of this biomimetic multi-layered scaffold to support and guide the host reparative response in the treatment of osteochondral defects.

STATEMENT OF SIGNIFICANCE

Osteochondral defects, involving cartilage and the underlying subchondral bone, frequently occur in young active patients due to disease or injury. While some treatment options are available, success is limited and patients often eventually require joint replacement. To address this clinical need, a multi-layer collagen-based osteochondral defect repair scaffold designed to direct host-stem cell mediated tissue formation within each region, has been developed in our group. The present study investigates the in vivo response to this scaffold in a critical-sized defect in a rabbit knee. Results shows the scaffolds ability to guide the host reparative response leading to tissue regeneration with a zonal organisation, repair of the subchondral bone, formation of an overlying cartilaginous layer and evidence of an intermediate tidemark.

Injectable in situ forming poly(l-glutamic acid) hydrogels for cartilage tissue engineering

Injectable, in situ forming hydrogels have exhibited many advantages in regenerative medicine. Herein, we present the novel design of poly(l-glutamic acid) injectable hydrogels via the self-crosslinking of adipic dihydrazide (ADH)-modified poly(l-glutamic acid) (PLGA-ADH) and aldehyde-modified poly(l-glutamic acid) (PLGA-CHO), and investigate their potential in cartilage tissue engineering. Both the hydrazide modification degree of PLGA-ADH and oxidation degree of PLGA-CHO can be adjusted by the amount of activators and sodium periodate, respectively. Experiments reveal that the solid content of the hydrogels, -NH₂/-CHO molar ratio, and oxidation degree of PLGA-CHO have a great effect on the gelation time, equilibrium swelling, mechanical properties, microscopic morphology, and in vitro degradation of the hydrogels. Encapsulation of rabbit chondrocytes within the hydrogels showed viability of the entrapped cells and cytocompatibility of the injectable hydrogels. A preliminary study exhibits injectability and rapid in vivo gel formation, as well as mechanical stability, cell ingrowth, and ectopic cartilage formation. These results suggest that the PLGA hydrogel has potential as an injectable cell delivery carrier for cartilage regeneration and could serve as a new biomaterial for tissue engineering.

What is the future of 'organ transplantation' in the head and neck?

PURPOSE OF REVIEW

To update readers on the current state and future of head and neck tissue transplantation.

RECENT FINDINGS

Many exciting advances have recently occurred in the field of head and neck transplantation and regenerative medicine. Larynx, face, and trachea transplants have all been successfully performed. Significant advancements in tissue engineering have occurred, including the ability to generate three-dimensional tissue structures. Transplantation of regenerated tissues has been successfully incorporated into airway reconstruction.

SUMMARY

These exciting advancements set the foundation to expand reconstructive options for dysfunctional tissues and to improve a patient's quality of life.

Chitosan-based scaffold modified with D-(+) raffinose for cartilage repair: an in vivo study

BACKGROUND

Osteochondral defects significantly affect patients' quality of life and represent challenging tissue lesions, because of the poor regenerative capacity of cartilage. Tissue engineering has long sought to promote cartilage repair, by employing artificial scaffolds to enhance cell capacity to deposit new cartilage. An ideal biomaterial should closely mimic the natural environment of the tissue, to promote scaffold colonization, cell differentiation and the maintenance of a differentiated cellular phenotype. The present study evaluated chitosan scaffolds enriched with D-(+) raffinose in osteochondral defects in rabbits. Cartilage defects were created in distal femurs, both on the condyle and on the trochlea, and were left untreated or received a chitosan scaffold. The animals were sacrificed after 2 or 4 weeks, and samples were analysed microscopically.

RESULTS

The retrieved implants were surrounded by a fibrous capsule and contained a noticeable inflammatory infiltrate. No hyaline cartilage was formed in the defects. Although defect closure reached approximately 100% in the control group after 4 weeks, defects did not completely heal when filled with chitosan. In these samples, the lesion contained granulation tissue at 2 weeks, which was then replaced by fibrous connective tissue by week 4. Noteworthy, chitosan never appeared to be integrated in the surrounding cartilage.

CONCLUSIONS

In conclusion, the present study highlights the limits of D-(+) raffinose-enriched chitosan for cartilage regeneration and offers useful information for further development of this material for tissue repair.

Evaluation of chitosan-GP hydrogel biocompatibility in osteochondral defects: an experimental approach

Background

Articular cartilage, because of its avascular nature, has little capacity for spontaneous healing, and tissue engineering approaches, employing different biomaterials and cells, are under development. Among the investigated biomaterials are the chitosan-based hydrogels. Although thoroughly studied in other mammalian species, studies are scarce in equines. So, the aim of the present study was to investigate the biocompatibility of chitosan-GP in horse joints submitted to high mechanical loads.

Results

An osteochondral defect was created by arthroscopy in the medial surface of lateral trochlea of talus of left or right leg, randomly selected, from six healthy geldings. The defect was filled up with chitosan-GP. The contralateral joint received an identical defect with no implant. The chondral fragment removed to produce the defect was collected, processed and used as the “Initial” sample (normal cartilage) for histology, immunohistochemistry, and metabolic labelling of PGs. After 180 days, the repair tissues were collected, and also analyzed. At the end of the experiment (180 days after lesion), the total number of cells per field in repair tissues was equal to control, and macrophages and polymorphonuclear cells were not detected, suggesting that no significant inflammation was present. These cells were able to synthesize type II collagen and proteoglycans (PGs). Nevertheless, the cell population in these tissues, both in presence of chitosan-GP and in untreated controls, were heterogeneous, with a lower proportion of type II collagen-positives cells and some with a fibroblastic aspect. Moreover, the PGs synthesized in repair tissues formed in presence or absence of chitosan-GP were similar to those of normal cartilage. However, the chitosan-GP treated tissue had an disorganized appearance, and blood vessels were present.

Conclusions

Implanted chitosan-GP did not evoke an important inflammatory reaction, and permitted cell growth. These cells were able to synthesize type II collagen and PGs similar to those synthesized in normal cartilage and in healing tissue without implant, indicating its chondrocyte nature.

Development of hybrid scaffolds using ceramic and hydrogel for articular cartilage tissue regeneration

The regeneration of articular cartilage consisting of hyaline cartilage and hydrogel scaffolds has been generally used in tissue engineering. However, success in in vivo studies has been rarely reported. The hydrogel scaffolds implanted into articular cartilage defects are mechanically unstable and it is difficult for them to integrate with the surrounding native cartilage tissue. Therefore, it is needed to regenerate cartilage and bone tissue simultaneously. We developed hybrid scaffolds with hydrogel scaffolds for cartilage tissue and with ceramic scaffolds for bone tissue. For in vivo study, hybrid scaffolds were press-fitted into osteochondral tissue defects in a rabbit knee joints and the cartilage tissue regeneration in blank, hydrogel scaffolds, and hybrid scaffolds was compared. In 12th week after implantation, the histological and immunohistochemical analyses were conducted to evaluate the cartilage tissue regeneration. In the blank and hydrogel scaffold groups, the defects were filled with fibrous tissues and the implanted hydrogel scaffolds could not maintain their initial position; in the hybrid scaffold group, newly generated cartilage tissues were morphologically similar to native cartilage tissues and were smoothly connected to the surrounding native tissues. This study demonstrates hybrid scaffolds containing hydrogel and ceramic scaffolds can provide mechanical stability to hydrogel scaffolds and enhance cartilage tissue regeneration at the defect site.

Chondrogenesis of infrapatellar fat pad derived adipose stem cells in 3D printed chitosan scaffold

Infrapatellar fat pad adipose stem cells (IPFP-ASCs) have been shown to harbor chondrogenic potential. When combined with 3D polymeric structures, the stem cells provide a source of stem cells to engineer 3D tissues for cartilage repair. In this study, we have shown human IPFP-ASCs seeded onto 3D printed chitosan scaffolds can undergo chondrogenesis using TGFβ3 and BMP6. By week 4, a pearlescent, cartilage-like matrix had formed that penetrated the top layers of the chitosan scaffold forming a 'cap' on the scaffold. Chondrocytic morphology showed typical cells encased in extracellular matrix which stained positively with toluidine blue. Immunohistochemistry demonstrated positive staining for collagen type II and cartilage proteoglycans, as well as collagen type I. Real time PCR analysis showed up-regulation of collagen type II, aggrecan and SOX9 genes when IPFP-ASCs were stimulated by TGFβ3 and BMP6. Thus, IPFP-ASCs can successfully undergo chondrogenesis using TGFβ3 and BMP6 and the cartilage-like tissue that forms on the surface of 3D-printed chitosan scaffold may prove useful as an osteochondral graft.

Chitosan scaffolds containing calcium phosphate salts and rhBMP-2: in vitro and in vivo testing for bone tissue regeneration

Numerous strategies that are currently used to regenerate bone depend on employing biocompatible materials exhibiting a scaffold structure. These scaffolds can be manufactured containing particular active compounds, such as hydroxyapatite precursors and/or different growth factors to enhance bone regeneration process. Herein, we have immobilized calcium phosphate salts (CPS) and bone morphogenetic protein 2 (BMP-2) – combined or alone – into chitosan scaffolds using ISISA process. We have analyzed whether the immobilized bone morphogenetic protein preserved its osteoinductive capability after manufacturing process as well as BMP-2 in vitro release kinetic. We have also studied both the in vitro and in vivo biocompatibility of the resulting scaffolds using a rabbit model. Results indicated that rhBMP-2 remained active in the scaffolds after the manufacturing process and that its release kinetic was different depending on the presence of CPS. In vitro and in vivo findings showed that cells grew more in scaffolds with both CPS and rhBMP-2 and that these scaffolds induced more bone formation in rabbit tibia. Thus chitosan scaffolds containing both CPS and rhBMP-2 were more osteoinductive than their counterparts alone indicating that could be useful for bone regeneration purposes, such as some applications in dentistry.

Chitosan hydrogels for chondroitin sulphate controlled release: an analytical characterization

This paper provides an analytical characterization of chitosan scaffolds obtained by freeze-gelation toward the uptake and the controlled release of chondroitin sulphate (CS), as cartilage repair agent, under different pH conditions. Scanning electron microscopy (SEM), attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), and liquid chromatography-UV spectrophotometry (LC-UV) techniques were exploited to obtain qualitative and quantitative descriptions of polymer and drug behaviour in the biomaterial. As for morphology, SEM analysis allowed the evaluation of scaffold porosity in terms of pore size and distribution both at the surface (Feret diameter 58 ± 19 μm) and on the cross section (Feret diameter 106 ± 51 μm). LC and ATR-FTIR evidenced a pH-dependent CS loading and release behaviour, strongly highlighting the role of electrostatic forces on chitosan/chondroitin sulphate interactions.

Current concepts: tissue engineering and regenerative medicine applications in the ankle joint

Tissue engineering and regenerative medicine (TERM) has caused a revolution in present and future trends of medicine and surgery. In different tissues, advanced TERM approaches bring new therapeutic possibilities in general population as well as in young patients and high-level athletes, improving restoration of biological functions and rehabilitation. The mainstream components required to obtain a functional regeneration of tissues may include biodegradable scaffolds, drugs or growth factors and different cell types (either autologous or heterologous) that can be cultured in bioreactor systems (in vitro) prior to implantation into the patient. Particularly in the ankle, which is subject to many different injuries (e.g. acute, chronic, traumatic and degenerative), there is still no definitive and feasible answer to ‘conventional’ methods. This review aims to provide current concepts of TERM applications to ankle injuries under preclinical and/or clinical research applied to skin, tendon, bone and cartilage problems. A particular attention has been given to biomaterial design and scaffold processing with potential use in osteochondral ankle lesions.

Comparison of uncultured marrow mononuclear cells and culture-expanded mesenchymal stem cells in 3D collagen-chitosan microbeads for orthopedic tissue engineering

Stem cell-based therapies have shown promise in enhancing repair of bone and cartilage. Marrow-derived mesenchymal stem cells (MSC) are typically expanded in vitro to increase cell number, but this process is lengthy, costly, and there is a risk of contamination and altered cellular properties. Potential advantages of using fresh uncultured bone marrow mononuclear cells (BMMC) include heterotypic cell and paracrine interactions between MSC and other marrow-derived cells including hematopoietic, endothelial, and other progenitor cells. In the present study, we compared the osteogenic and chondrogenic potential of freshly isolated BMMC to that of cultured-expanded MSC, when encapsulated in three-dimensional (3D) collagen-chitosan microbeads. The effect of low and high oxygen tension on cell function and differentiation into orthopedic lineages was also examined. Freshly isolated rat BMMC (25 × 10(6) cells/mL, containing an estimated 5 × 10(4) MSC/mL) or purified and culture-expanded rat bone marrow-derived MSC (2 × 10(5) cells/mL) were added to a 65-35 wt% collagen-chitosan hydrogel mixture and fabricated into 3D microbeads by emulsification and thermal gelation. Microbeads were cultured in control MSC growth media in either 20% O2 (normoxia) or 5% O2 (hypoxia) for an initial 3 days, and then in control, osteogenic, or chondrogenic media for an additional 21 days. Microbead preparations were evaluated for viability, total DNA content, calcium deposition, and osteocalcin and sulfated glycosaminoglycan expression, and they were examined histologically. Hypoxia enhanced initial progenitor cell survival in fresh BMMC-microbeads, but it did not enhance osteogenic potential. Fresh uncultured BMMC-microbeads showed a similar degree of osteogenesis as culture-expanded MSC-microbeads, even though they initially contained only 1/10th the number of MSC. Chondrogenic differentiation was not strongly supported in any of the microbead formulations. This study demonstrates the microbead-based approach to culturing and delivering cells for tissue regeneration, and suggests that fresh BMMC may be an alternative to using culture-expanded MSC for bone tissue engineering.

Bending of layer-by-layer films driven by an external magnetic field

We report on optimized architectures containing layer-by-layer (LbL) films of natural rubber latex (NRL), carboxymethyl-chitosan (CMC) and magnetite (Fe₃O₄) nanoparticles (MNPs) deposited on flexible substrates, which could be easily bent by an external magnetic field. The mechanical response depended on the number of deposited layers and was explained semi-quantitatively with a fully atomistic model, where the LbL film was represented as superposing layers of hexagonal graphene-like atomic arrangements deposited on a stiffer substrate. The bending with no direct current or voltage being applied to a supramolecular structure containing biocompatible and antimicrobial materials represents a proof-of-principle experiment that is promising for tissue engineering applications in biomedicine.

Preparation of an osteochondral composite with mesenchymal stem cells as the single-cell source in a double-chamber bioreactor

A double-chamber bioreactor has been developed to generate a tissue-engineered osteochondral composite (TEOC). However, a TEOC generally requires two types of cells (i.e. chondrogenic and osteogenic cells). Therefore, the capacity of mesenchymal stem cells (MSCs) as a single-cell source to work within a double-chamber bioreactor and biphasic scaffolds for generating TEOC was investigated. Compared with static culture, the double-chamber bioreactor not only can promote faster cellular proliferation, indicated by the PicoGreen dsDNA assay, SEM and confocal imaging, but also can trigger efficient chondrogenic and osteogenic differentiation of MSCs in biphasic scaffolds simultaneously, evidenced by gene expression. Thus MSCs are promising as the ideal single-cell source and the double-chamber bioreactor is an advanced culture system to generate TEOC.

Stereological analysis of subchondral angiogenesis induced by chitosan and coagulation factors in microdrilled articular cartilage defects

OBJECTIVE

Cartilage repair elicited by bone marrow stimulation can be enhanced by a chitosan-glycerol phosphate (GP)/blood implant, through mechanisms involving therapeutic inflammatory angiogenesis. The implant is formed by in situ coagulation, which can be accelerated by adding coagulation factors. We hypothesized that coagulation factors enhance acute subchondral angiogenesis in repairing drilled defects.

DESIGN

Full-thickness cartilage defects were created bilaterally in 12 skeletally mature rabbit knee trochlea, microdrilled, then allowed to bleed as a control (N = 6) or treated with chitosan-GP/blood implant (N = 6), or implant solidified with thrombin (IIa), tissue factor (TF) with recombinant human factor VIIa (rhFVIIa), or rhFVIIa alone (N = 4 each condition). At 3 weeks post-operative, quantitative stereology was used to obtain blood vessel length (L(V)), surface (S(V)), and volume (V(V)) density at systematic depths in two microdrill holes per defect. Collagen type I, type II and glycosaminoglycan (GAG) percent stain in non-mineralized repair tissue were analysed by histomorphometry.

RESULTS

All drill holes were healing, and showed a depth-dependent increase in granulation tissue blood vessel density (Lv, Sv, and Vv, P < 0.005). Residual chitosan implant locally suppressed blood vessel ingrowth into the granulation tissue, whereas holes completely cleared of chitosan amplified angiogenesis vs microdrill-only (P = 0.049), an effect enhanced by IIa. Chitosan implant suppressed strong Col-I, Col-II, and GAG accumulation that occurred spontaneously in drill-only bone defects (P < 0.005) and coagulation factors did not alter this effect.

CONCLUSIONS

Subchondral angiogenesis is promoted by chitosan implant clearance. Chitosan implant treatment suppresses fibrocartilage scar tissue formation, and promotes bone remodeling, which allows more blood vessel migration and woven bone repair towards the cartilage lesion area.