Scaffold-Mediated Immunoengineering as Innovative Strategy for Tendon Regeneration

Tendon injuries are at the frontier of innovative approaches to public health concerns and sectoral policy objectives. Indeed, these injuries remain difficult to manage due to tendon’s poor healing ability ascribable to a hypo-cellularity and low vascularity, leading to the formation of a fibrotic tissue affecting its functionality. Tissue engineering represents a promising solution for the regeneration of damaged tendons with the aim to stimulate tissue regeneration or to produce functional implantable biomaterials. However, any technological advancement must take into consideration the role of the immune system in tissue regeneration and the potential of biomaterial scaffolds to control the immune signaling, creating a pro-regenerative environment. In this context, immunoengineering has emerged as a new discipline, developing innovative strategies for tendon injuries. It aims at designing scaffolds, in combination with engineered bioactive molecules and/or stem cells, able to modulate the interaction between the transplanted biomaterial-scaffold and the host tissue allowing a pro-regenerative immune response, therefore hindering fibrosis occurrence at the injury site and guiding tendon regeneration. Thus, this review is aimed at giving an overview on the role exerted from different tissue engineering actors in leading immunoregeneration by crosstalking with stem and immune cells to generate new paradigms in designing regenerative medicine approaches for tendon injuries.

Characterization of innately decellularised micropattern pseudostem of Musa balbisiana - A non-surface functionalized 3D economic biomaterial scaffold

Banana (Musa balbisiana) pseudostem 3D scaffolds have been developed here for primary eukaryotic cell and cell line culture as an economical, sustainable, eco-friendly alternative for surface-functionalized polymeric and plant tissue-based structures. Musa pseudostem 3D micro pattern scaffold (MPM-3Ds) developed by freeze-drying followed by ethylene oxide sterilization yielded 5.6ng of DNA per mg of tissue, confirming its extended decellularised state. Thermogravimetric analysis, contact angle measurement, uniaxial testing, and FTIR determined thermal stability, wettability, tensile strength, and surface functional groups respectively. Micro and macronutrients, sugars, and amino acids that naturally enrich MPM-3Ds were estimated using EDAX, HPLC, and biochemical analysis. The most important finding was, non-surface functionalized MPM-3Ds supported attachment, growth, and differentiation of human mesenchyme stem cells, human primary hepatocytes like cells, primary mouse brain cortical neurons, mouse fibroblast cells, and human pancreatic cancer cells. MPM-3Ds showed in vivo biodegradation and biocompatibility in a preliminary analysis in Sprague Dawley rats. These findings illuminate nature's power to nurture cells in the micropattern cradles of MPM- 3Ds that can support innovative research in stem cell differentiation, drug and cosmetic testing, and biosensor development leading to advanced biomedical research.

Characterization of innately decellularised micropattern pseudostem of Musa balbisiana - A non-surface functionalized 3D economic biomaterial scaffold

Banana (Musa balbisiana) pseudostem 3D scaffolds have been developed here for primary eukaryotic cell and cell line culture as an economical, sustainable, eco-friendly alternative for surface-functionalized polymeric and plant tissue-based structures. Musa pseudostem 3D micro pattern scaffold (MPM-3Ds) developed by freeze-drying followed by ethylene oxide sterilization yielded 5.6ng of DNA per mg of tissue, confirming its extended decellularised state. Thermogravimetric analysis, contact angle measurement, uniaxial testing, and FTIR determined thermal stability, wettability, tensile strength, and surface functional groups respectively. Micro and macronutrients, sugars, and amino acids that naturally enrich MPM-3Ds were estimated using EDAX, HPLC, and biochemical analysis. The most important finding was, non-surface functionalized MPM-3Ds supported attachment, growth, and differentiation of human mesenchyme stem cells, human primary hepatocytes like cells, primary mouse brain cortical neurons, mouse fibroblast cells, and human pancreatic cancer cells. MPM-3Ds showed in vivo biodegradation and biocompatibility in a preliminary analysis in Sprague Dawley rats. These findings illuminate nature's power to nurture cells in the micropattern cradles of MPM- 3Ds that can support innovative research in stem cell differentiation, drug and cosmetic testing, and biosensor development leading to advanced biomedical research.

Photoinduced Porcine Gelatin Cross-Linking by Homobi- and Homotrifunctional Tetrazoles

Gelatin is a costless polypeptide material of natural origin, able to form hydrogels that are potentially useful in biomaterial scaffold design for drug delivery, cell cultures, and tissue engineering. However, gelatin hydrogels are unstable at physiological conditions, losing their features only after a few minutes at 37 °C. Accordingly, treatments to address this issue are of great interest. In the present work, we propose for the first time the use of bi- and trifunctional tetrazoles, most of them unknown to date, for photoinduced gelatin cross-linking towards the production of physiologically stable hydrogels. Indeed, after UV-B irradiation, aryl tetrazoles generate a nitrilimine intermediate that is reactive towards different functionalities, some of them constitutively present in the amino acid side chains of gelatin. The efficacy of the treatment strictly depends on the structure of the cross-linking agent used, and substantial improved stability was observed by switching from bifunctional to trifunctional cross-linkers.

Magnetic resonance imaging for non-invasive clinical evaluation of normal and regenerated cartilage

With the development of tissue engineering and regenerative medicine, it is much desired to establish bioimaging techniques to monitor the real-time regeneration efficacy in vivo in a non-invasive way. Herein, we tried magnetic resonance imaging (MRI) to evaluate knee cartilage regeneration after implanting a biomaterial scaffold seeded with chondrocytes, namely, matrix-induced autologous chondrocyte implantation (MACI). After summary of the T2 mapping and the T1-related delayed gadolinium-enhanced MRI imaging of cartilage (dGEMRIC) in vitro and in vivo in the literature, these two MRI techniques were tried clinically. In this study, 18 patients were followed up for 1 year. It was found that there was a significant difference between the regeneration site and the neighboring normal site (control), and the difference gradually diminished with regeneration time up to 1 year according to both the quantitative T1 and T2 MRI methods. We further established the correlation between the quantitative evaluation of MRI and the clinical Lysholm scores for the first time. Hence, the MRI technique was confirmed to be a feasible semi-quantitative yet non-invasive way to evaluate the in vivo regeneration of knee articular cartilage.

Cartilage Repair Capacity within a Single Full-Thickness Chondral Defect in a Porcine Autologous Matrix-Induced Chondrogenesis Model Is Affected by the Location within the Defect

Objective Large articular cartilage defects are a challenge to regenerative surgery. Biomaterial scaffolds might provide valuable support for restoration of articulating surface. The performance of a composite biomaterial scaffold was evaluated in a large porcine cartilage defect. Design Cartilage repair capacity of a biomaterial combining recombinant human type III collagen (rhCo) and poly-(l/d)-lactide (PLA) was tested in a porcine model. A full-thickness chondral defect covering the majority of the weightbearing area was inflicted to the medial femoral condyle of the right knee. Spontaneous cartilage repair and nonoperated healthy animals served as controls. The animals were sacrificed after a 4-month follow-up. The repair tissue was evaluated with the International Cartilage Repair Society (ICRS) macroscopic score, ICRS II histological score, and with micro-computed tomography. Additionally, histopathological evaluation of lymph nodes and synovial samples were done for toxicological analyses. Results The lateral half of the cartilage defect in the operated groups showed better filling than the medial half. The mean overall macroscopic score for the rhCo-PLA, spontaneous, and nonoperated groups were 5.96 ± 0.33, 4.63 ± 0.42, and 10.98 ± 0.35, respectively. The overall histological appearance of the specimens was predominantly hyaline cartilage in 3 of 9 samples of the rhCo-PLA group, 2 of 8 of the spontaneous group, and 9 of 9 of the nonoperated group. Conclusions The use of rhCo-PLA scaffold did not differ from spontaneous healing. The repair was affected by the spatial properties within the defect, as the lateral part of the defect showed better repair than the medial part, probably due to different weightbearing conditions.

Design Challenges in Polymeric Scaffolds for Tissue Engineering

Numerous surgical procedures are daily performed worldwide to replace and repair damaged tissue. Tissue engineering is the field devoted to the regeneration of damaged tissue through the incorporation of cells in biocompatible and biodegradable porous constructs, known as scaffolds. The scaffolds act as host biomaterials of the incubating cells, guiding their attachment, growth, differentiation, proliferation, phenotype, and migration for the development of new tissue. Furthermore, cellular behavior and fate are bound to the biodegradation of the scaffold during tissue generation. This article provides a critical appraisal of how key biomaterial scaffold parameters, such as structure architecture, biochemistry, mechanical behavior, and biodegradability, impart the needed morphological, structural, and biochemical cues for eliciting cell behavior in various tissue engineering applications. Particular emphasis is given on specific scaffold attributes pertaining to skin and brain tissue generation, where further progress is needed (skin) or the research is at a relatively primitive stage (brain), and the enumeration of some of the most important challenges regarding scaffold constructs for tissue engineering.