Towards Bioinspired Meniscus-Regenerative Scaffolds: Engineering a Novel 3D Bioprinted Patient-Specific Construct Reinforced by Biomimetically Aligned Nanofibers

In Situ Printing of Polylactic Acid/Nanoceramic Filaments for the Repair of Bone Defects Using a Portable 3D Device

In situ 3D printing is attractive for the direct repair of bone defects in underdeveloped countries and in emergency situations. So far, the lack of an interesting method to produce filament using FDA-approved biopolymers and nanoceramics combined with a portable strategy limits the use of in situ 3D printing. Herein, we investigated the osseointegration of new nanocomposite filaments based on polylactic acid (PLA), laponite (Lap), and hydroxyapatite (Hap) printed directly at the site of the bone defect in rats using a portable 3D printer. The filaments were produced using a single-screw extruder (L/D = 26), without the addition of solvents that can promote the toxicity of the materials. In vitro performance was evaluated in the cell differentiation process with mesenchymal stem cells (MSC) by an alkaline phosphatase activity test and visualization of mineralization nodules; a cell viability test and total protein dosage were performed to evaluate cytotoxicity. For the in vivo analysis, the PLA/Lap composite filaments with a diameter of 1.75 mm were printed directly into bone defects of Wistar rats using a commercially available portable 3D printer. Based on the in vitro and in vivo results, the in situ 3D printing technique followed by rapid cooling proved to be promising for bone tissue engineering. The absence of fibrous encapsulation and inflammatory processes became a good indicator of effectiveness in terms of biocompatibility parameters and bone tissue formation, and the use of the portable 3D printer showed a significant advantage in the application of this material by in situ printing.

Current advances in engineering meniscal tissues: insights into 3D printing, injectable hydrogels and physical stimulation based strategies

The knee meniscus is the cushioning fibro-cartilage tissue present in between the femoral condyles and tibial plateau of the knee joint. It is largely avascular in nature and suffers from a wide range of tears and injuries caused by accidents, trauma, active lifestyle of the populace and old age of individuals. Healing of the meniscus is especially difficult due to its avascularity and hence requires invasive arthroscopic approaches such as surgical resection, suturing or implantation. Though various tissue engineering approaches are proposed for the treatment of meniscus tears, three-dimensional (3D) printing/bioprinting, injectable hydrogels and physical stimulation involving modalities are gaining forefront in the past decade. A plethora of new printing approaches such as direct light photopolymerization and volumetric printing, injectable biomaterials loaded with growth factors and physical stimulation such as low-intensity ultrasound approaches are being added to the treatment portfolio along with the contemporary tear mitigation measures. This review discusses on the necessary design considerations, approaches for 3D modeling and design practices for meniscal tear treatments within the scope of tissue engineering and regeneration. Also, the suitable materials, cell sources, growth factors, fixation and lubrication strategies, mechanical stimulation approaches, 3D printing strategies and injectable hydrogels for meniscal tear management have been elaborated. We have also summarized potential technologies and the potential framework that could be the herald of the future of meniscus tissue engineering and repair approaches.

Biofabrication of Composite Bioink-Nanofiber Constructs: Effect of Rheological Properties of Bioinks on 3D (Bio)Printing and Cells Interaction with Aligned Touch Spun Nanofibers

This paper reports on a novel approach for the fabrication of composite multilayered bioink-nanofibers construct. This work achieves this by using a hands-free 3D (bio)printing integrated touch-spinning approach. Additionally, this work investigates the interaction of fibroblasts in different bioinks with the highly aligned touch-spun nanofibers. This work conducts a comprehensive characterization of the rheological properties of the inks, starting with low-strain oscillatory rheology to analyze the viscoelastic behavior, when the material structure remains intact. Moreover, this work performs amplitude sweeps to investigate the stability of the inks under large deformations, rotational rheology to examine the shear thinning profile, and a three-step creep experiment to study time-dependent rheological behavior. The obtained rheological results are correlated to visual observation of the flow behavior of inks. These behaviors span from an ink with zero-shear viscosity, very weak shear thinning, and no thixotropic behavior to inks exhibiting flow stress, pronounced shear thinning, and thixotropy. It is demonstrated that inks have an essential effect on cell behavior. While all bioinks allow a preferred directionality of the fibroblasts along the fiber direction, cells tend to form aggregates in bioinks with higher viscosity, and a considerable number of agglomerates are observed in the presence of laponite-RD.

Advances in Hydrogels for Meniscus Tissue Engineering: A Focus on Biomaterials, Crosslinking, Therapeutic Additives

Meniscus tissue engineering (MTE) has emerged as a promising strategy for meniscus repair and regeneration. As versatile platforms, hydrogels have gained significant attention in this field, as they possess tunable properties that allow them to mimic native extracellular matrices and provide a suitable microenvironment. Additionally, hydrogels can be minimally invasively injected and can be adjusted to match the shape of the implant site. They can conveniently and effectively deliver bioactive additives and demonstrate good compatibility with other functional materials. These inherent qualities have made hydrogel a promising candidate for therapeutic approaches in meniscus repair and regeneration. This article provides a comprehensive review of the advancements made in the research on hydrogel application for meniscus tissue engineering. Firstly, the biomaterials and crosslinking strategies used in the formation of hydrogels are summarized and analyzed. Subsequently, the role of therapeutic additives, including cells, growth factors, and other active products, in facilitating meniscus repair and regeneration is thoroughly discussed. Furthermore, we summarize the key issues for designing hydrogels used in MTE. Finally, we conclude with the current challenges encountered by hydrogel applications and suggest potential solutions for addressing these challenges in the field of MTE. We hope this review provides a resource for researchers and practitioners interested in this field, thereby facilitating the exploration of new design possibilities.

A comparative study on various cell sources for constructing tissue-engineered meniscus

Injury to the meniscus is a common occurrence in the knee joint and its management remains a significant challenge in the clinic. Appropriate cell source is essential to cell-based tissue regeneration and cell therapy. Herein, three commonly used cell sources, namely, bone marrow mesenchymal stem cell (BMSC), adipose-derived stem cell (ADSC), and articular chondrocyte, were comparatively evaluated to determine their potential for engineered meniscus tissue in the absence of growth factor stimulus. Cells were seeded on electrospun nanofiber yarn scaffolds that share similar aligned fibrous configurations with native meniscus tissue for constructing meniscus tissue in vitro. Our results show that cells proliferated robustly along nanofiber yarns to form organized cell-scaffold constructs, which recapitulate the typical circumferential fiber bundles of native meniscus. Chondrocytes exhibited different proliferative characteristics and formed engineered tissues with distinct biochemical and biomechanical properties compared to BMSC and ADSC. Chondrocytes maintained good chondrogenesis gene expression profiles and produced significantly increased chondrogenic matrix and form mature cartilage-like tissue as revealed by typical cartilage lacunae. In contrast, stem cells underwent predominately fibroblastic differentiation and generated greater collagen, which contributes to improved tensile strengths of cell-scaffold constructs in comparison to the chondrocyte. ADSC showed greater proliferative activity and increased collagen production than BMSC. These findings indicate that chondrocytes are superior to stem cells for constructing chondrogenic tissues while the latter is feasible to form fibroblastic tissue. Combination of chondrocytes and stem cells might be a possible solution to construct fibrocartilage tissue and meniscus repair and regeneration.

Biomanufacturing of biomimetic three-dimensional nanofibrous multicellular constructs for tissue regeneration

Biomanufacturing of functional tissue analogues is of great importance in regenerative medicine. However, this is still highly challenging due to extreme difficulties in recreating/recapitulating complicated anatomies of body tissues that have both well-defined three-dimensional (3D) multicellular organizations and bioactive nanofibrous extracellular matrix (ECM). In the current investigation, a biomanufacturing approach via concurrent emulsion electrospinning and coaxial cell electrospraying was developed, which could fabricate 3D nanofibrous multicellular constructs that resemble both the multicellular organizations and bioactive nanofibrous microenvironments of body tissues. In the proof-of-concept study, endothelial cells (ECs) and smooth muscle cells (SMCs) were placed in respective layers of multilayer-structured constructs. The two different construct layers consisted of nanofibers providing different topographies (randomly oriented nanofibers or aligned nanofibers) and contained different growth factors (vascular endothelial growth factor or platelet-derived growth factor). The ECs and SMCs in the different construct layers showed high cell densities (> 4 ×10⁵ cells/cm² after 4-day incubation) and high cell viabilities (> 95%). Owing to the contact guidance/stimulation by different fibrous topographies and sequential release of different growth factors, ECs and SMCs exhibited distinct morphologies (uniformly stretched plaque-shaped or directionally elongated) and displayed enhanced proliferative activities. Our biomanufacturing approach is shown to be effective and efficient in reconstituting/replicating cell-ECM organizations as well as their interactions similar to those in body tissues such as blood vessels, indicating the great promise to produce a range of tissue analogues with biomimetic structures and functions for modeling or regenerating body tissues.

In situ forming double-crosslinked hydrogels with highly dispersed short fibers for the treatment of irregular wounds

In situ forming injectable hydrogels hold great potential for the treatment of irregular wounds. However, their practical applications were hindered by long gelation time, poor mechanical performance, and a lack of a natural extracellular matrix structure. Herein, amino-modified electrospun poly(lactic-co-glycolic acid) (APLGA) short fibers with uniform distribution were introduced into gelatin methacrylate/oxidized dextran (GM/ODex) hydrogels. In comparison with the fiber aggregation structure in the PLGA fiber-incorporated hydrogels, the hydrogels with APLGA fibers possessed a uniform porous structure. The highly dispersed APLGA short fibers accelerated the sol-gel phase transition of the hydrogel due to the formation of dynamic Schiff-base bonds between the fibers and hydrogels. Furthermore, in combination with UV-assisted crosslinking, a rapid gelation time of 90 s was achieved for the double-crosslinked hydrogels. The addition of APLGA short fibers as fillers and the formation of the double-crosslinking network enhanced the mechanical performance of the hydrogels. Furthermore, the fiber-hydrogel composites exhibited favorable injectability, excellent biocompatibility, and improved cell infiltration. In vivo assessment indicated that the GM/ODex-APLGA hydrogels successfully filled the full-thickness defects and improved wound healing. This work demonstrates a promising solution for the treatment of irregular wounds.

Application of Tissue Engineered Nanomaterials in Meniscus Sports Injury Repair

In daily life and sports activities, the knee joint is the dominant joint. Movements such as walking upstairs, running, and walking require the knee joint to function. The principle of tissue engineering and the technical methods of molecular biology to construct functional meniscus replacement products in vitro have become an ideal method to fundamentally solve the meniscus injury. This paper aims to study the application of tissue engineered nanomaterials in meniscal sports injury repair. In this paper, KOA exercise therapy based on Kalman filter theory is proposed, which has a great effect on the rehabilitation of bone tissue injuries. The experimental results of this paper show that in the number of people with meniscus injuries in 2013, the percentage of people younger than 25 years old was 13%, and the percentage of people younger than 25 years old in 2020 was 12%, which did not change much. However, the percentage of people over 40 years old was 57% in 2013, and by 2020, the percentage is 66%. Although the increase is not large, the percentage of people over the age of 40 is the highest every year, which means that older people have a higher proportion of meniscal injuries.