Marine collagen-chitosan-fucoidan cryogels as cell-laden biocomposites envisaging tissue engineering.

The combination of marine origin biopolymers for tissue engineering (TE) applications is of high interest, due to their similarities with the proteins and polysaccharides present in the extracellular matrix of different human tissues. This manuscript reports on innovative collagen-chitosan-fucoidan cryogels formed by the simultaneous blending of these three marine polymers in a chemical-free crosslinking approach. The physicochemical characterization of marine biopolymers comprised FTIR, amino acid analysis, circular dichroism and SDS-PAGE, and suggested that the jellyfish collagen used in the cryogels was not denatured (preserved the triple helical structure) and had similarities with type II collagen. The chitosan presented a high deacetylation degree (90.1%) that can strongly influence the polymer physicochemical properties and biomaterial formation. By its turn, rheology, and SEM studies confirmed that these novel cryogels present interesting properties for TE purposes, such as effective blending of biopolymers without visible material segregation, mechanical stability (strong viscoelastic character), as well as adequate porosity to support cell proliferation and exchange of nutrients and waste products. Additionally, in vitro cellular assessments of all cryogel formulations revealed a non-cytotoxic behavior. The MTS test, live/dead assay and cell morphology assessment (phalloidin DAPI) showed that cryogels can provide a proper microenvironment for cell culturing, supporting cell viability and promoting cell proliferation. Overall, the obtained results suggest that the novel collagen-chitosan-fucoidan cryogels herein presented are promising scaffolds envisaging tissue engineering purposes, as both acellular biomaterials or cell-laden cryogels.

Methacrylated gellan gum and hyaluronic acid hydrogel blends for image-guided neurointerventions.

Cell-based therapies delivered via intrathecal injection are considered as one of the most promising solutions for the treatment of amyotrophic lateral sclerosis (ALS). Herein, injectable manganese-based biocompatible hydrogel blends were developed, that can allow image-guided cell delivery. The hydrogels can also provide physical support for cells during injection, and at the intrathecal space after transplantation, while assuring cell survival. In this regard, different formulations of methacrylated gellan gum/hyaluronic acid hydrogel blends (GG-MA/HA) were considered as a vehicle for cell delivery. The hydrogels blends were supplemented with paramagnetic Mn2+ to allow a real-time monitorization of hydrogel deposition via T1-weighted magnetic resonance imaging (MRI). The developed hydrogels were easily extruded and formed a stable fiber upon injection into the cerebrospinal fluid. Hydrogels prepared with a 75 : 25 GG-MA to HA ratio supplemented with MnCl2 at 0.1 mM showed controlled hydrogel degradation, suitable permeability, and a distinct MRI signal in vitro and in vivo. Additionally, human-derived adipose stem cells encapsulated in 75 : 25 GG-MA/HA hydrogels remained viable for up to 14 days of culture in vitro. Therefore, the engineered hydrogels can be an excellent tool for injectable image-guided cell delivery approaches.

Hyaluronic Acid.

In recent times, the field of tissue engineering and regenerative medicine (TERM) has considerably increased the extent of therapeutic strategies for clinical application in orthopedics. However, TERM approaches have its rules and requirements, in the respect of the biologic response of each tissue and bioactive agents which need to be considered, respected, and subject of ongoing studies. Different medical devices/products have been prematurely available on the market and used in clinics with limited success. However, other therapeutics, when used in a serious and evidence-based approach, have achieved considerable success, considering the respect for solid expectations from doctors and patients (when properly informed).Orthobiologics has appeared as a recent technological trend in orthopedics. This includes the improvement or regeneration of different musculoskeletal tissues by means of using biomaterials (e.g., hyaluronic acid), stem cells, and growth factors (e.g., platelet-rich plasma). The potential symbiotic relationship between biologic therapies and surgery makes these strategies suitable to be used in one single intervention.However, herein, the recent clinical studies using hyaluronic acid (HA) in the treatment of orthopedic conditions will mainly be overviewed (e.g., osteochondral lesions, tendinopathies). The possibilities to combine different orthobiologic agents as TERM clinical strategies for treatment of orthopedic problems will also be briefly discussed.

Promising Biomolecules.

The osteochondral defect (OD) comprises the articular cartilage and its subchondral bone. The treatment of these lesions remains as one of the most problematic clinical issues, since these defects include different tissues, requiring distinct healing approaches. Among the growing applications of regenerative medicine, clinical articular cartilage repair has been used for two decades, and it is an effective example of translational medicine; one of the most used cell-based repair strategies includes implantation of autologous cells in degradable scaffolds such as alginate, agarose, collagen, chitosan, chondroitin sulfate, cellulose, silk fibroin, hyaluronic acid, and gelatin, among others. Concerning the repair of osteochondral defects, tissue engineering and regenerative medicine started to design single- or bi-phased scaffold constructs, often containing hydroxyapatite-collagen composites, usually used as a bone substitute. Biomolecules such as natural and synthetic have been explored to recreate the cartilage-bone interface through multilayered biomimetic scaffolds. In this chapter, a succinct description about the most relevant natural and synthetic biomolecules used on cartilage and bone repair, describing the procedures to obtain these biomolecules, their chemical structure, common modifications to improve its characteristics, and also their application in the biomedical fields, is given.

PRP Therapy.

Osteochondral lesions remain as a clinical challenge despite the advances in orthopedic regenerative strategies. Biologics, in particular, platelet-rich plasma, has been applied for the reparative and regenerative effect in many tissues, and osteochondral tissue is not an exception. Platelet-rich plasma is an autologous concentrate prepared from the collected blood; thus, this safe application is free of immune response or risk of transmission of disease. It has a high potential to promote regeneration, thanks to its content, and can be applied alone or can reinforce a tissue engineering strategy. The relevant works making use of platelet-rich plasma in osteochondral lesions are overviewed herein. The practical success of platelet-rich plasma is uncertain since there are many factors involved including but not limited to its preparation and administration method. Nevertheless, today, the issues and challenges of platelet-rich plasma have been well acknowledged by researchers and clinicians. Thus, it is believed that a consensus will be built it, and then with high-quality randomized controlled trials and standardized protocols, the efficacy of platelet-rich plasma therapy can be better evaluated. HIGHLIGHTS: The need of treating the osteochondral lesions has not been yet met in the clinics. Thanks to being an autologous source of growth factors, interleukins, and other cytokines and relative ease of clinical application, i.e., during a single-step surgical procedure, the use of platelet-rich plasma is of great interest. The high theoretical potential of the role of platelet-rich plasma in the regeneration process of osteochondral lesions is known, and the efficiency needs to be confirmed by high-quality randomized controlled trials for a robust position in the treatments of osteochondral lesions in the clinics.

Small Animal Models.

Animal assays represent an important stage between in vitro studies and human clinical applications. These models are crucial for biomedical research and regenerative medicine studies, as these offer precious information for systematically assessing the efficacy and risks of recently created biomaterials, medical devices, drugs, and therapeutic modalities prior to initiation of human clinical trials. Therefore, selecting a suitable experimental model for tissue engineering purposes is essential to establish valid conclusions. However, it remains important to be conscious of the advantages and limitations of the various small and large animal models frequently used for biomedical research as well as the different challenges encountered in extrapolating data obtained from animal studies and the risks of misinterpretation. This chapter discusses the various small animal model strategies used for osteochondral defect repair. Particular emphasis will be placed on analyzing the materials and strategies used in each model.