Preservation of critical quality attributes of mesenchymal stromal cells in 3D bioprinted structures by using natural hydrogel scaffolds

3D printing in musculoskeletal interface engineering: Current progress and future directions

The musculoskeletal system relies on critical tissue interfaces for its function; however, these interfaces are often compromised by injuries and diseases. Restoration of these interfaces is complex by nature which renders traditional treatments inadequate. An emerging solution is three-dimensional printing, which allows for precise fabrication of biomimetic scaffolds to enhance tissue regeneration. This review summarizes the utility of 3D printing in creating scaffolds for musculoskeletal interfaces, mainly focusing on advanced techniques such as multi-material printing, bioprinting, and 4D printing. We emphasize the significance of mimicking natural tissue gradients and the selection of appropriate biomaterials to ensure scaffold success. The review outlines state-of-the-art 3D printing technologies, varying from extrusion, inkjet and laser-assisted bioprinting, which are crucial for producing scaffolds with tailored mechanical and biological properties. Applications in cartilage-bone, intervertebral disc, tendon/ligament-bone, and muscle-tendon junction engineering are discussed, highlighting the potential for improved integration and functionality. Furthermore, we address challenges in material development, printing resolution, and the in vivo performance of scaffolds, as well as the prospects for clinical translation. The review concludes by underscoring the transformative potential of 3D printing to advance orthopedic medicine, offering a roadmap for future research at the intersection of biomaterials, drug delivery, and tissue engineering.

Biological Functions of Macromolecular Protein Hydrogels in Constructing Osteogenic Microenvironment

Irreversible bone defects resulting from trauma, infection, and degenerative illnesses have emerged as a significant health concern. Structurally and functionally controllable hydrogels made by bone tissue engineering (BTE) have become promising biomaterials. Natural proteins are able to establish connections with autologous proteins through unique biologically active regions. Hydrogels based on proteins can simulate the bone microenvironment and regulate the biological behavior of stem cells in the tissue niche, making them candidates for research related to bone regeneration. This article reviews the biological functions of various natural macromolecular proteins (such as collagen, gelatin, fibrin, and silk fibroin) and highlights their special advantages as hydrogels. Then the latest research trends on cross-linking modified macromolecular protein hydrogels with improved mechanical properties and composite hydrogels loaded with exogenous micromolecular proteins have been discussed. Finally, the applications of protein hydrogels, such as 3D printed hydrogels, microspheres, and injectable hydrogels, were introduced, aiming to provide a reference for the repair of clinical bone defects.

Mesenchymal stem cells aligned and stretched in self-assembling peptide hydrogels

The presented research highlights a novel approach using fmoc-protected peptide hydrogels for the encapsulation and stretching of mesenchymal stem cells (MSCs). This study utilized a custom mechanical stretching device with a PDMS chamber to stretch human MSCs encapsulated in Fmoc hydrogels. The study assessed the influence of various solvents on the self-assembly and mechanical properties of the hydrogels, and MSC viability and alignment. Particularly we focused on fluorenylmethoxycarbonyl-diphenylalanine (Fmoc-FF) prepared in dimethyl sulfoxide (DMSO), hexafluoro-2-propanol (HFP), and deionized water (DiH2O). Through molecular self-assembly of the peptide sequence into β-sheets connected by π-π aromatic stacking of F-F groups, the peptide hydrogel was found to form a stiff, hydrated gel with nanofiber morphology and a compressive modulus ranging from 174 to 277 Pa. Therefore, this hydrogel can mimic certain critical features of the extracellular matrix and collagen. Evaluations of MSCs cultured on the peptide hydrogels, including viability, morphology, and alignment assessments using various staining techniques, demonstrated that 3D-cultured MSCs in Fmoc-FF/HFP and Fmoc-FF/DMSO, followed by mechanical stretching, exhibited elongated morphology with distinct microfilament fibers compared to the control cells, which maintained a round and spherical F-actin shape. Notably, peptide gels with a concentration of 5 mM maintained 100 % MSC viability. The findings indicate the potential and specific conditions for successful cell encapsulation and alignment within peptide hydrogels, highlighting a promising tissue engineering platform through the encapsulation of MSCs in peptide nanofibers followed by a stretching process. By enhancing our understanding of MSC-peptide hydrogel interactions, this research contributes to the development of biomaterials tailored for regenerative medicine.

Advanced Hydrogel-Based Strategies for Enhanced Bone and Cartilage Regeneration: A Comprehensive Review

Bone and cartilage tissue play multiple roles in the organism, including kinematic support, protection of organs, and hematopoiesis. Bone and, above all, cartilaginous tissues present an inherently limited capacity for self-regeneration. The increasing prevalence of disorders affecting these crucial tissues, such as bone fractures, bone metastases, osteoporosis, or osteoarthritis, underscores the urgent imperative to investigate therapeutic strategies capable of effectively addressing the challenges associated with their degeneration and damage. In this context, the emerging field of tissue engineering and regenerative medicine (TERM) has made important contributions through the development of advanced hydrogels. These crosslinked three-dimensional networks can retain substantial amounts of water, thus mimicking the natural extracellular matrix (ECM). Hydrogels exhibit exceptional biocompatibility, customizable mechanical properties, and the ability to encapsulate bioactive molecules and cells. In addition, they can be meticulously tailored to the specific needs of each patient, providing a promising alternative to conventional surgical procedures and reducing the risk of subsequent adverse reactions. However, some issues need to be addressed, such as lack of mechanical strength, inconsistent properties, and low-cell viability. This review describes the structure and regeneration of bone and cartilage tissue. Then, we present an overview of hydrogels, including their classification, synthesis, and biomedical applications. Following this, we review the most relevant and recent advanced hydrogels in TERM for bone and cartilage tissue regeneration.