Cartilage Tissue Formation Research Articles

Four-Dimensional Printing of β-Tricalcium Phosphate-Modified Shape Memory Polymers for Bone Scaffolds in Osteochondral Regeneration

The use of scaffolds for osteochondral tissue regeneration requires an appropriate selection of materials and manufacturing techniques that provide the basis for supporting both cartilage and bone tissue formation. As scaffolds are designed to replicate a part of the replaced tissue and ensure cell growth and differentiation, implantable materials have to meet various biological requirements, e.g., biocompatibility, biodegradability, and mechanical properties. Osteoconductive materials such as tricalcium phosphate ceramics and some biodegradable polymers appear to be a perfect choice. The present work evaluates the structural, mechanical, thermal, and functional properties of a shape memory terpolymer modified with β-tricalcium phosphate (β-TCP). A new approach is using the developed materials for 4D printing, with a particular focus on its applicability in manufacturing medical implants. In this study, the manufacturing parameters of the scaffold components were developed. The scaffolds were examined via scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS), Fourier-transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), and mechanical testing. The cytotoxicity result was obtained with an MTT assay, and the alkaline phosphatase (ALP) activity was measured. The structural and microstructural investigations confirmed the integration of β-TCP into the filament matrix and scaffolds. Thermal stability was enhanced as β-TCP delayed depolymerization of the polymer matrix. The shape memory studies demonstrated effective recovery. The in vitro cell culture studies revealed the significantly increased cell viability and alkaline phosphatase (ALP) activity of the β-TCP-modified terpolymer after 3 weeks. The developed terpolymer can be tailored for applications in which partial shape recovery is acceptable, such as bone scaffolds.

Application of miR-29a-Exosome and Multifunctional Scaffold for Full-Thickness Cartilage Defects

BackgroundFull-thickness cartilage defect is a common refractory disease in orthopedics. In this study, we designed a novel composite scaffold composed of silk fibroin-chitosan for the cartilage layer and porous tantalum for the subchondral bone layer, loaded with engineered bone mesenchymal stem cell exosomes, to evaluate its efficacy in repairing full-thickness cartilage defect. MethodsPorous tantalum was 3D printed and combined with silk fibroin-chitosan to form a composite scaffold. Chondrocytes were cultured on the scaffold, and their growth was assessed using the CCK-8 method. Toluidine blue staining confirmed cell morphology, while immunofluorescence revealed collagen type Ⅱ expression. Engineered exosomes loaded with miR-29a were created and characterized using various techniques. Co-culturing with chondrocytes demonstrated their proliferation over 10 days. Immunofluorescence revealed staining for the nucleus, collagen type II, and Aggrecan. In vivo experiments were performed on rats to assess cartilage defect repair, utilizing histological staining and micro-CT scanning at 4 and 8 weeks post-operation. ResultsThe silk fibroin-chitosan scaffold demonstrated good biocompatibility, supporting chondrocyte adhesion, growth, and cartilage tissue formation. Engineered exosomes exhibited promising biological activity, conducive to bone and cartilage regeneration. The implantation of the silk fibroin-chitosan/porous tantalum composite scaffold loaded with engineered exosomes promoted integration with the surrounding bone and cartilage tissues, facilitating repair and regeneration. ConclusionsThe silk fibroin-chitosan combined with porous tantalum scaffold carrying engineered exosomes loaded with miR-29a has good potential for full-thickness cartilage defects regeneration.

Engineered Osteochondral Scaffolds with Bioactive Cartilage Zone for Enhanced Articular Cartilage Regeneration.

Despite progress, osteochondral (OC) tissue engineering strategies face limitations in terms of articular cartilage layer development and its integration with the underlying bone tissue. The main objective of this study is to develop a zonal OC scaffold with native biochemical signaling in the cartilage zone to promote articular cartilage development devoid of cells and growth factors. Herein, we report the development and in vivo assessment of a novel gradient and zonal-structured scaffold for OC defect regeneration. The scaffold system is composed of a mechanically supportive 3D-printed template containing decellularized cartilage extracellular matrix (ECM) biomaterial in the cartilage zone that possesses bioactive characteristics, such as chemotactic activity and native tissue biochemical composition. OC scaffolds with a bioactive cartilage zone were implanted in vivo in a rabbit osteochondral defect model and assessed for gross morphology, matrix deposition, cellular distribution, and overall tissue regeneration. The scaffold system supported recruitment and infiltration of host cells into the cartilage zone of the graft, which led to increased ECM deposition and physiologically relevant articular cartilage tissue formation. Semi-quantitative ICRS scoring (overall score double for OC scaffold with bioactive cartilage zone compared to PLA scaffold) further confirm the bioactive scaffold enhanced articular cartilage engineering. This strategy of designing bioactive scaffolds to promote endogenous cellular infiltration can be a much simpler and effective approach for OC tissue repair and regeneration.

In Vitro Investigation of 3D Printed Hydrogel Scaffolds with Electrospun Tidemark Component for Modeling Osteochondral Interface.

Osteochondral (OC) tissue plays a crucial role due to its ability to connect bone and cartilage tissues. To address the complexity of structure and functionality at the bone-cartilage interface, relevant to the presence of the tidemark as a critical element at the bone-cartilage boundary, we fabricated graded scaffolds through sequential 3D printing. The scaffold's bottom layer was based on a gelatin/oxidized alginate mixture enriched with hydroxyapatite (HAp) to create a rougher surface and larger pores to promote osteogenesis. In contrast, the upper layer was engineered to have smaller pores and aimed to promote cartilage tissue formation and mimic the physical properties of the cartilage. An electrospun ε-polycaprolactone (PCL) membrane with micrometer-range pores was incorporated between the layers to replicate the function of tidemark-a barrier to prevent vascularization of cartilage from subchondral bone tissue. In vitro cell studies confirmed the viability of the cells on the layers of the scaffolds and the ability of PCL mesh to prevent cellular migration. The fabricated scaffolds were thoroughly characterized, and their mechanical properties were compared to native OC tissue, demonstrating suitability for OC tissue engineering and graft modeling. The distance of gradient of mineral concentration was found to be 151 µm for grafts and the native OC interface.

Transforming growth factor-β1-loaded RADA-16 hydrogel scaffold for effective cartilage regeneration

Cartilage repair remains a major challenge in clinical trials. These current cartilage repair materials can not effectively promote chondrocyte generation, limiting their practical application in cartilage repair. In this work, we develop an implantable scaffold of RADA-16 peptide hydrogel incorporated with TGF-β1 to provide a microenvironment for stem cell-directed differentiation and chondrocyte adhesion growth. The longest release of growth factor TGF-β1 release can reach up to 600 h under physiological conditions. TGF-β1/RADA-16 hydrogel was demonstrated to be a lamellar porous structure. Based on the cell culture with hBMSCs, TGF-β1/RADA-16 hydrogel showed excellent ability to promote cell proliferation, directed differentiation into chondrocytes, and functional protein secretion. Within 14 days, 80% of hBMSCs were observed to be directed to differentiate into vigorous chondrocytes in the co-culture of TGF-β1/RADA-16 hydrogels with hBMSCs. Specifically, these newly generated chondrocytes can secrete and accumulate large amounts of collagen II within 28 days, which can effectively promote the formation of cartilage tissue. Finally, the exploration of RADA-16 hydrogel-based scaffolds incorporated with TGF-β1 bioactive species would further greatly promote the practical clinical trials of cartilage remediation, which might have excellent potential to promote cartilage regeneration in areas of cartilage damage.

Cobalt-containing calcium silicate nanowires incorporated scaffolds for the repair of osteochondral defect induced by chondrosarcoma

Considering the difficulty in the treatment of chondrosarcoma in clinic, multifunctional composite hydrogel scaffolds were designed with excellent photothermal ability for the regeneration of damaged bone and cartilage tissue. The chitosan solution/polyvinyl alcohol (CP) hydrogels with different contents of cobalt doped calcium silicate (Co-CSH) nanowires were prepared via 3D printing method. Attributing to the excellent photothermal performance of Co-CSH nanowires, the average survival rate of human chondrosarcoma cells in the CP-5Co-13.4 % and CP-5Co-16.2 % scaffolds with near infrared laser irradiation was about 10.5 % and 9.9 %, respectively. At the same time, the prepared composite hydrogel scaffolds possessed satisfactory biocompatibility and could support the adhesion and spread of rabbit bone mesenchymal stem cells (rBMSCs) and rabbit chondrocytes in the hydrogel scaffolds, and further promoted the formation of new bone and cartilage tissue in vivo, on account of the stimulation effect of released bioactive ions. Therefore, the prepared composite hydrogel scaffolds is expected to provide a new therapeutic strategy for the postoperative adjuvant treatment of chondrosarcoma.

Multipatterned Chondrocytes' Scaffolds by FL-MOPL with a BSA-GMA Hydrogel to Regulate Chondrocytes' Morphology.

Repairing articular cartilage damage is challenging due to its low regenerative capacity. In vitro, cartilage regeneration is a potential strategy for the functional reconstruction of cartilage defects. A hydrogel is an advanced material for mimicking the extracellular matrix (ECM) due to its hydrophilicity and biocompatibility, which is known as an ideal scaffold for cartilage regeneration. However, chondrocyte culture in vitro tends to dedifferentiate, leading to fibrosis and reduced mechanical properties of the newly formed cartilage tissue. Therefore, it is necessary to understand the mechanism of modulating the chondrocytes' morphology. In this study, we synthesize photo-cross-linkable bovine serum albumin-glycidyl methacrylate (BSA-GMA) with 65% methacrylation. The scaffolds are found to be suitable for chondrocyte growth, which are fabricated by homemade femtosecond laser maskless optical projection lithography (FL-MOPL). The large-area chondrocyte scaffolds have holes with interior angles of triangle (T), quadrilateral (Q), pentagon (P), hexagonal (H), and round (R). The FL-MOPL polymerization mechanism, swelling, degradation, and biocompatibility of the BSA-GMA hydrogel have been investigated. Furthermore, cytoskeleton and nucleus staining reveals that the R-scaffold with larger interior angle is more effective in maintaining chondrocyte morphology and preventing dedifferentiation. The scaffold's ability to maintain the chondrocytes' morphology improves as its shape matches that of the chondrocytes. These results suggest that the BSA-GMA scaffold is a suitable candidate for preventing chondrocyte differentiation and supporting cartilage tissue repair and regeneration. The proposed method for chondrocyte in vitro culture by developing biocompatible materials and flexible fabrication techniques would broaden the potential application of chondrocyte transplants as a viable treatment for cartilage-related diseases.

Fabrication of gelatin-heparin based cartilage models: enhancing spatial complexity through refinement of stiffness properties and oxygen availability

The intricate nature of native cartilage, characterized by zonal variations in oxygen levels and ECM composition, poses a challenge for existing hydrogel-based tissue models. Consequently, these 3D models often present simplified renditions of the native tissue, failing to fully capture its heterogenous nature. The combined effects of hydrogel components, network properties, and structural designs on cellular responses are often overlooked. In this work, we aim to establish more physiological cartilage models through biofabrication of photopolymerizable allylated-gelatin (GelAGE) and Thiolated Heparin (HepSH) constructs with tailorable matrix stiffness and customized architectures. This involves systematically studying how the native glycosaminoglycan Heparin together with hydrogel stiffness, and oxygen availability within 3D structures influence chondrogenic differentiation and regional heterogeneity. A comprehensive library of 3D hydrogel constructs was successfully developed, encompassing GelAGE-HepSH hydrogels with three distinct stiffness levels: 12, 55 and 121 kPa, and three unique geometries: spheres, discs, and square lattices. In soft GelAGE-HepSH hydrogels, the localization of differentiating cells was observed to be irregular, while stiff hydrogels restricted the overall secretion of ECM components. The medium-stiff hydrogels were found to be most applicable, supporting both uniform tissue formation and maintained shape fidelity. Three different 3D architectures were explored, where biofabrication of smaller GelAGE-HepSH spheres without oxygen gradients induced homogenous, hyaline cartilage tissue formation. Conversely, fabrication of larger constructs (discs and lattices) with oxygen gradients could be utilized to design heterogenous cartilage tissue models. Similarly, temporal oxygen gradients were observed to drive interconnected deposition of glycosaminoglycans (GAGs). Control samples of GelAGE without HepSH did not exhibit any notable changes in chondrogenesis as a function of stiffness, architectures, or oxygen concentrations. Overall, the incorporation of HepSH within GelAGE hydrogels was observed to serve as an amplifier for the biological effects from both stiffness and oxygen cues. In conclusion, fabrication of GelAGE-HepSH constructs designed to impose limitations on oxygen availability induce more zone-specific cartilage tissue alignment. This systematic study of matrix components, network stiffness, and oxygen levels in 3D biofabricated structures contributes to the development of more physiologically relevant cartilage models while further enhancing our overall understanding of cartilage tissue engineering.

Immunomodulatory Strategies for Cartilage Regeneration in Osteoarthritis.

Osteoarthritis (OA) is the most prevalent musculoskeletal disorder and a leading cause of disability globally. Although many efforts have been made to treat this condition, current tissue engineering (TE) and regenerative medicine strategies fail to address the inflammatory tissue environment that leads to the rapid progression of the disease and prevents cartilage tissue formation. First, this review addresses in detail the current anti-inflammatory therapies for OA with a special emphasis on pharmacological approaches, gene therapy, and mesenchymal stromal cell (MSC) intra-articular administration, and discusses the reasons behind the limited clinical success of these approaches at enabling cartilage regeneration. Then, we analyze the state-of-the-art TE strategies and how they can be improved by incorporating immunomodulatory capabilities such as the optimization of biomaterial composition, porosity and geometry, and the loading of anti-inflammatory molecules within an engineered structure. Finally, the review discusses the future directions for the new generation of TE strategies for OA treatment, specifically focusing on the spatiotemporal modulation of anti-inflammatory agent presentation to allow for tailored patient-specific therapies. Impact statement Osteoarthritis (OA) is a prevalent and debilitating musculoskeletal disorder affecting millions worldwide. Despite significant advancements in regenerative medicine and tissue engineering (TE), mitigating inflammation while simultaneously promoting cartilage tissue regeneration in OA remains elusive. In this review article, we discuss current anti-inflammatory therapies and explore their potential synergy with cutting-edge cartilage TE strategies, with a special focus on novel spatiotemporal and patient-specific anti-inflammatory strategies.

A MODERN VIEW ON REPARATIVE OSTEOGENESIS: MAIN STAGES AND THEIR PATTERNS

Introduction. Reparative osteogenesis is a staged mechanism that ensures the restoration of damaged bone tissue. The study and summarization of current data about bone defect regeneration is the basis for the search and development of methods to improve this process. The aim of the study is to analyze and systematize the current data about reparative osteogenesis, describe the main stages and their patterns. Materials and methods. Searching the relevant sources using online scientific databases and keywords. Selection of publications for review. Further analysis and synthesis of information. The results. Despite different interpretations of the stages of reparative osteogenesis by researchers, they all describe the same coordinated process. The following key stages have been identified: haematoma formation, inflammation, MSC involvement and angiogenesis, cartilage, connective and bone tissue formation, their subsequent reorganisation, ossification and remodelling. Each of these stages involves specific cellular elements, local and general regulatory factors. The development of osteogenic cells and mechanisms of intercellular interaction, as well as the main signalling pathways and molecules (Wnt, RANK/RANKL/OPG, BMPs, HIF, etc.) that regulate osteo- and angiogenesis are described. The role of hypoxia in the process of bone regeneration and angiogenesis is highlighted. The H-type vessels and their participation in the regulation of osteogenesis are considered. Attention is paid to the phenomenon of ‘chondrocyte transdifferentiation’, which is one of the sources of osteoblasts during endochondral ossification. In the context of remodelling, the law of bone biomechanics and piezoelectric adaptive remodelling, as well as bone multicellular units as microsystems that ensure the restructuring of coarse fibrous bone tissue into lamellar bone tissue, are described. Conclusions. Reparative osteogenesis is a complicated and coordinated process at both the cellular and molecular levels. The regeneration process depends on numerous local and systemic factors and the optimization search is carried out at each stage

Repair of Bone Defect of the Talus with Calcaneus Autograft and Autologous Matrix-Induced Chondrogenesis: A Case Report

Background. The question of choosing a treatment strategy for full-thickness osteochondral defects of the tarsal bone remains relevant. When choosing a treatment strategy, two key points should be considered: restoring the architecture of the tarsal bone and achieving long-term restoration of cartilage-like coverage in the area of the osteochondral defect.
 Case report. A 34-year-old physically active patient sustained an ankle injury in 2011 and was treated conservatively. In 2020, he complained of pain and reduced activity. Initial assessment scores were: VAS (Visual Analog Scale) — 6 points, AOFAS-AHS (American Orthopaedic Foot and Ankle Society Ankle-Hindfoot Score) — 49 points, FAAM (Foot and Ankle Ability Measure) — 55 points. An MRI revealed an osteochondral defect in the medial part of the tarsal bone dome, measuring 16.4×9.4 mm and with a depth of 20.8 mm. The patient underwent the replacement of the bone defect with an autograft taken from the heel bone, using autologus matrix induced chondrogenesis (AMIC) procedure. After 6 months, a follow-up examination was performed, including ankle arthroscopy and removal of metal fixators. Arthroscopic findings showed that the chondroplasty area was almost identical to intact joint cartilage. One year after chondroplasty, the patient returned to his previous level of physical activity. Assessment scores were: VAS — 1 point, AOFAS-AHS — 94 points, FAAM — 83 points.
 Conclusion. The proposed method allows for the restoration of the architecture of the tarsal bone along with the cartilage surface. The use of a bone autograft helps to fill the tarsal bone defect, and covering the autograft with a collagen membrane contributes to the formation of hyaline-like cartilage tissue in the defect area.

Structural and Molecular Changes of Human Chondrocytes Exposed to the Rotating Wall Vessel Bioreactor.

Over the last 30 years, the prevalence of osteoarthritis (OA), a disease characterized by a loss of articular cartilage, has more than doubled worldwide. Patients suffer from pain and progressive loss of joint function. Cartilage is an avascular tissue mostly consisting of extracellular matrix with embedded chondrocytes. As such, it does not regenerate naturally, which makes an early onset of OA prevention and treatment a necessity to sustain the patients' quality of life. In recent years, tissue engineering strategies for the regeneration of cartilage lesions have gained more and more momentum. In this study, we aimed to investigate the scaffold-free 3D cartilage tissue formation under simulated microgravity in the NASA-developed rotating wall vessel (RWV) bioreactor. For this purpose, we cultured both primary human chondrocytes as well as cells from the immortalized line C28/I2 for up to 14 days on the RWV and analyzed tissue morphology, development of apoptosis, and expression of cartilage-specific proteins and genes by histological staining, TUNEL-assays, immunohistochemical detection of collagen species, and quantitative real-time PCR, respectively. We observed spheroid formation in both cell types starting on day 3. After 14 days, constructs from C28/I2 cells had diameters of up to 5 mm, while primary chondrocyte spheroids were slightly smaller with 3 mm. Further inspection of the 14-day-old C28/I2 spheroids revealed a characteristic cartilage morphology with collagen-type 1, -type 2, and -type 10 positivity. Interestingly, these tissues were less susceptible to RWV-induced differential gene expression than those formed from primary chondrocytes, which showed significant changes in the regulation of IL6, ACTB, TUBB, VIM, COL1A1, COL10A1, MMP1, MMP3, MMP13, ITGB1, LAMA1, RUNX3, SOX9, and CASP3 gene expression. These diverging findings might reflect the differences between primary and immortalized cells. Taken together, this study shows that simulated microgravity using the RWV bioreactor is suitable to engineer dense 3D cartilage-like tissue without addition of scaffolds or any other artificial materials. Both primary articular cells and the stable chondrocyte cell line C28/I2 formed 3D neocartilage when exposed for 14 days to an RWV.

Исследование биораспределения биомедицинского клеточного продукта на основе хондроцитов человека при имплантации мышам линии BALB/C nude

Despite the prospects of the approach to cell therapy of cartilage damage in humans involving autologous chondrocytes, similar technologies are just beginning to be introduced into medical practice in the Russian Federation. In this regard, the development of biomedical cell products (BCPs) for cartilage tissue repair is quite topical, while the use of organoid technology is the most close to the native tissue conditions. According to requirements of legislation of the Russian Federation, it is necessary to assess biodistribution characterizing migration potential of the cells, their tropism for body tissues following implantation within the framework of preclinical trials. The study was aimed to assess biodistribution of novel BCP based on human chondrocytes in the form of chondrospheres after subcutaneous implantation in Balb/c nude mice. Implantation to 12 mice was performed during the first phase, along with administration of saline to 12 control animals. Weighting and follow-up were conducted for 90 days. Then mice were withdrawn from the experiment to collect samples of organs and tissues for histological analysis of the implant, estimation of its viability, integration. During the second phase biodistribution was assessed by PCR in order to detect human DNA in the organ and tissue samples. Chondrospheres successfully integrated in the tissues surrounding the inoculation zones and formed cartilage tissue. No significant (p < 0.05) changes in weight were reported. No human DNA found in chondrosphere implantation zones was detected in the samples collected from other organs and tissues. BCP demonstrated no biodistribution across other tissues and organs of mice 90 days after implantation, which suggested that the product developed was safe.

Detection of the de novo Pro253Arg Mutation of Fibroblast Growth Factor Receptor 2 (FGFR2) in a Pediatric Patient with Congenital Hand Anomaly

Congenital hand deformities are a group of birth defects related to abnormal development of soft, cartilage, or bone tissues in the hands. Recent studies have indicated that the most usual reason of congenital hand anomalies are due to the genetic factors. In this study, we sequenced the exome of a 2.5-year-old female patient case with bilateral hand deformity. Results revealed that the patient did not carry mutations in the expression region of the GLI3 and SHH genes. However, the patient did have a heterozygous mutation: FGFR2: c.C758G, p.P253R. Sanger sequencing confirmed this was a de novo mutation as it was not detected in the parents. In silico analyses indicated that P253R has a potential effect to alter the structure and function of the fibroblast growth factor receptor, consequently disrupting the processes involved in the formation and development of bone and cartilage tissues. Overall, this research will contribute to a better understanding of the role and functionality of the FGF molecular signaling network in the development and synthesis of bone and cartilage tissues, particularly during the embryonic stage.

Single-Step Biofabrication of In Situ Spheroid-Forming Compartmentalized Hydrogel for Clinical-Sized Cartilage Tissue Formation.

3D cellular spheroids offer more biomimetic microenvironments than conventional 2D cell culture technologies, which has proven value for many tissue engineering applications. Despite beneficiary effects of 3D cell culture, clinical translation of spheroid tissue engineering is challenged by limited scalability of current spheroid formation methods. Although recent adoption of droplet microfluidics can provide a continuous production process, use of oils and surfactants, generally low throughput, and requirement of additional biofabrication steps hinder clinical translation of spheroid culture. Here, the use of clean (e.g., oil-free and surfactant-free), ultra-high throughput (e.g., 8.5mL min-1 , 10 000 spheroids s-1 ), single-step, in-air microfluidic biofabrication of spheroid forming compartmentalized hydrogels is reported. This novel technique can reliably produce 1D fibers, 2D planes, and 3D volumescompartmentalized hydrogel constructs, which each allows for distinct (an)isotropic orientation of hollow spheroid-forming compartments. Spheroids produced within ink-jet bioprinted compartmentalized hydrogels outperform 2D cell cultures in terms of chondrogenic behavior. Moreover, the cellular spheroids can be harvested from compartmentalized hydrogels and used to build shape-stable centimeter-sized biomaterial-free living tissues in a bottom-up manner. Consequently, it is anticipated that in-air microfluidic production of spheroid-forming compartmentalized hydrogels can advance production and use of cellular spheroids for various biomedical applications.

Simulating the mechanical stimulation of cells on a porous hydrogel scaffold using an FSI model to predict cell differentiation.

3D-structured hydrogel scaffolds are frequently used in tissue engineering applications as they can provide a supportive and biocompatible environment for the growth and regeneration of new tissue. Hydrogel scaffolds seeded with human mesenchymal stem cells (MSCs) can be mechanically stimulated in bioreactors to promote the formation of cartilage or bone tissue. Although in vitro and in vivo experiments are necessary to understand the biological response of cells and tissues to mechanical stimulation, in silico methods are cost-effective and powerful approaches that can support these experimental investigations. In this study, we simulated the fluid-structure interaction (FSI) to predict cell differentiation on the entire surface of a 3D-structured hydrogel scaffold seeded with cells due to dynamic compressive load stimulation. The computational FSI model made it possible to simultaneously investigate the influence of both mechanical deformation and flow of the culture medium on the cells on the scaffold surface during stimulation. The transient one-way FSI model thus opens up significantly more possibilities for predicting cell differentiation in mechanically stimulated scaffolds than previous static microscale computational approaches used in mechanobiology. In a first parameter study, the impact of the amplitude of a sinusoidal compression ranging from 1% to 10% on the phenotype of cells seeded on a porous hydrogel scaffold was analyzed. The simulation results show that the number of cells differentiating into bone tissue gradually decreases with increasing compression amplitude, while differentiation into cartilage cells initially multiplied with increasing compression amplitude in the range of 2% up to 7% and then decreased. Fibrous cell differentiation was predicted from a compression of 5% and increased moderately up to a compression of 10%. At high compression amplitudes of 9% and 10%, negligible areas on the scaffold surface experienced high stimuli where no cell differentiation could occur. In summary, this study shows that simulation of the FSI system is a versatile approach in computational mechanobiology that can be used to study the effects of, for example, different scaffold designs and stimulation parameters on cell differentiation in mechanically stimulated 3D-structured scaffolds.

Enhanced Cartilage and Subchondral Bone Repair Using Carbon Nanotube-Doped Peptide Hydrogel-Polycaprolactone Composite Scaffolds.

A carbon nanotube-doped octapeptide self-assembled hydrogel (FEK/C) and a hydrogel-based polycaprolactone PCL composite scaffold (FEK/C3-S) were developed for cartilage and subchondral bone repair. The composite scaffold demonstrated modulated microstructure, mechanical properties, and conductivity by adjusting CNT concentration. In vitro evaluations showed enhanced cell proliferation, adhesion, and migration of articular cartilage cells, osteoblasts, and bone marrow mesenchymal stem cells. The composite scaffold exhibited good biocompatibility, low haemolysis rate, and high protein absorption capacity. It also promoted osteogenesis and chondrogenesis, with increased mineralization, alkaline phosphatase (ALP) activity, and glycosaminoglycan (GAG) secretion. The composite scaffold facilitated accelerated cartilage and subchondral bone regeneration in a rabbit knee joint defect model. Histological analysis revealed improved cartilage tissue formation and increased subchondral bone density. Notably, the FEK/C3-S composite scaffold exhibited the most significant cartilage and subchondral bone formation. The FEK/C3-S composite scaffold holds great promise for cartilage and subchondral bone repair. It offers enhanced mechanical support, conductivity, and bioactivity, leading to improved tissue regeneration. These findings contribute to the advancement of regenerative strategies for challenging musculoskeletal tissue defects.

Evaluation and Application of Silk Fibroin Based Biomaterials to Promote Cartilage Regeneration in Osteoarthritis Therapy.

Osteoarthritis (OA) is a common joint disease characterized by cartilage damage and degeneration. Traditional treatments such as NSAIDs and joint replacement surgery only relieve pain and do not achieve complete cartilage regeneration. Silk fibroin (SF) biomaterials are novel materials that have been widely studied and applied to cartilage regeneration. By mimicking the fibrous structure and biological activity of collagen, SF biomaterials can promote the proliferation and differentiation of chondrocytes and contribute to the formation of new cartilage tissue. In addition, SF biomaterials have good biocompatibility and biodegradability and can be gradually absorbed and metabolized by the human body. Studies in recent years have shown that SF biomaterials have great potential in treating OA and show good clinical efficacy. Therefore, SF biomaterials are expected to be an effective treatment option for promoting cartilage regeneration and repair in patients with OA. This article provides an overview of the biological characteristics of SF, its role in bone and cartilage injuries, and its prospects in clinical applications to provide new perspectives and references for the field of bone and cartilage repair.

Fabricating the cartilage: recent achievements.

This review aims to describe the most recent achievements and provide an insight into cartilage engineering and strategies to restore the cartilage defects. Here, we discuss cell types, biomaterials, and biochemical factors applied to form cartilage tissue equivalents and update the status of fabrication techniques, which are used at all stages of engineering the cartilage. The actualized concept to improve the cartilage tissue restoration is based on applying personalized products fabricated using a full cycle platform: a bioprinter, a bioink consisted of ECM-embedded autologous cell aggregates, and a bioreactor. Moreover, in situ platforms can help to skip some steps and enable adjusting the newly formed tissue in the place during the operation. Only some achievements described have passed first stages of clinical translation; nevertheless, the number of their preclinical and clinical trials is expected to grow in the nearest future.

Effect of Collagen and GelMA on Preservation of the Costal Chondrocytes' Phenotype in a Scaffold in vivo.

Chondrocytes were isolated from the costal cartilage of newborn rats using 0.15% collagenase solution in DMEM. The cells was characterized by glycosaminoglycan staining with alcian blue. Chondrocyte scaffolds were obtained from 4% type I porcine atelocollagen and 10% GelMA by micromolding and then implanted subcutaneously into the withers of two groups of Wistar rats. Histological and immunohistochemical studies were performed on days 12 and 26 after implantation. Tissue samples were stained with hematoxylin and eosin, alcian blue; type I and type II collagens were identified by the corresponding antibodies. The implanted scaffolds induced a moderate inflammatory response in both groups when implanted in animals. By day 26 after implantation, both collagen and GelMA had almost completely resorbed. Cartilage tissue formation was observed in both animal groups. The newly formed tissue was stained intensively with alcian blue, and the cells were positive for both types of collagen. Cartilage tissue was formed among muscle fibers. The ability of collagen type I and GelMA hydrogels to form hyaline cartilage in animals after subcutaneous implantation of scaffolds was studied. Both collagen and GelMA contributed to formation of hyaline-like cartilage tissue type in animals, but the chondrocyte phenotype is characterized as mixed. Additional detailed studies of possible mechanisms of chondrogenesis under the influence of each of the hydrogels are needed.