Nanofibrous polyester-polypeptide block copolymer scaffolds with high porosity and controlled degradation promote cell adhesion, proliferation and differentiation

Engineering of gelatin scaffold by extracellular matrix of Sertoli cells for embryonic stem cell proliferation

Mimicking the microenvironment of seminiferous tubules plays an indispensable role in directing differentiation of stem cells toward germ cells in vitro. In this work, we fabricated electrospun gelatin (EG) mats (i.e., with diameter <500 nm) conditioned with Sertoli cells' extracellular matrix (ECM) to simulate both 3D structures and composition of normal testis tissue. Sertoli cells were isolated from mice testis and represented through immunocytochemistry (ICC) staining for expression of vimentin, a specific marker of Sertoli cells. The morphological characteristics of ECM-coated scaffold were investigated under scanning electron microscope (SEM). The efficient elimination of cells was confirmed by MTT assay. Furthermore, the cyto/biocompatibility of ECM-conditioned EG scaffold was determined for Sertoli cells and embryonic stem cells (ESCs), alone and as in co-culture. According to the results, the designed scaffold provided a mat for cell proliferation with negligible toxicity (almost 100% cell viability). SEM micrographs displayed cells with elongated shape and complete stretching morphology when compared with those cultured on scaffold without ECM. Moreover, an enhanced differentiation of ESCs toward sperm-generating cells was obtained through co-culturing of Sertoli cells and ESCs, where cell viability was found almost 100%. Our findings introduce the ECM-conditioned EG scaffold as a potentially influential engineered substrate for in vitro guidance of stem cells differentiation by mimicking the native microenvironment.

Bridging the gap: a translational perspective in spinal cord injury

Traumatic spinal cord injury (SCI) is a devastating and complex condition to treat with no curative options. In the past few decades, rapid advancements in our understanding of SCI pathophysiology as well as the mergence of new treatments has created more optimism. Focusing on clinical translation, this paper provides a comprehensive overview of SCI through its epidemiology, pathophysiology, currently employed management strategies, and emerging therapeutic approaches. Additionally, it emphasizes the importance of addressing the heavy quality of life (QoL) challenges faced by SCI patients and their desires, providing a basis to tailor patient-centric forms of care. Furthermore, this paper discusses the frequently encountered barriers in translation from preclinical models to clinical settings. It also seeks to summarize significant completed and ongoing SCI clinical trials focused on neuroprotective and neuroregenerative strategies. While developing a cohesive regenerative treatment strategy remains challenging, even modest improvements in sensory and motor function can offer meaningful benefits and motivation for patients coping with this highly debilitating condition.

Poly(ferulic acid)-hybrid nanofibers for reducing thrombosis and restraining intimal hyperplasia in vascular tissue engineering

Small-diameter blood vascular transplantation failure is mainly caused by the vascular materials' unreliable hemocompatibility and histocompatibility and the unmatched mechanical properties, which will cause unstable blood flow. How to solve the problems of coagulation and intimal hyperplasia caused by the above factors is formidable in vascular replacement. In this work, we have synthesized poly(ferulic acid) (PFA) and prepared poly(ester-urethane)urea (PEUU)/silk fibroin (SF)/poly(ferulic acid) (PFA) hybrid nanofibers vascular graft (PSPG) by random electrospinning and post-double network bond crosslinking for process optimization. The results in vitro demonstrated that the graft is of significant anti-oxidation, matched mechanical properties, reliable cytocompatibility, and blood compatibility. Replacing resected rat abdominal aorta and rabbit carotid artery models with PSPG vascular grafts indicated that the grafts are capable of homogeneous hybrid PFA significantly promoted the stabilization of endothelial cells and the ingrowth of smooth muscle cells, meanwhile stabilizing the immune microenvironment. This research demonstrates the PSPG vascular graft with substantial patency, indicating their potential for injured vascular healing.

Bioprinted anisotropic scaffolds with fast stress relaxation bioink for engineering 3D skeletal muscle and repairing volumetric muscle loss

Viscoelastic hydrogels can enhance 3D cell migration and proliferation due to the faster stress relaxation promoting the arrangement of the cellular microenvironment. However, most synthetic photocurable hydrogels used as bioink materials for 3D bioprinting are typically elastic. Developing a photocurable hydrogel bioink with fast stress relaxation would be beneficial for 3D bioprinting engineered 3D skeletal muscles in vitro and repairing volumetric muscle loss (VML) in vivo; however, this remains an ongoing challenge. This study aims to develop an interpenetrating network (IPN) hydrogel with tunable stress relaxation using a combination of gelatin methacryloyl (GelMA) and fibrinogen. These IPN hydrogels with faster stress relaxation showed higher 3D cellular proliferation and better differentiation. A 3D anisotropic biomimetic scaffold was further developed via a printing gel-in-gel strategy, where the extrusion printing of cell-laden viscoelastic FG hydrogel within Carbopol supported gel. The 3D engineered skeletal muscle tissue was further developed via 3D aligned myotube formation and contraction. Furthermore, the cell-free 3D printed scaffold was implanted into a rat VML model, and both the short and long-term repair results demonstrated its ability to enhance functional skeletal muscle tissue regeneration. These data suggest that such viscoelastic hydrogel provided a suitable 3D microenvironment for enhancing 3D myogenic differentiation, and the 3D bioprinted anisotropic structure provided a 3D macroenvironment for myotube organization, which indicated the potential in skeletal muscle engineering and VML regeneration. STATEMENT OF SIGNIFICANCE: The development of a viscoelastic 3D aligned biomimetic skeletal muscle scaffold has been focused on skeletal muscle regeneration. However, a credible technique combining viscoelastic hydrogel and printing gel-in-gel strategy for fabricating skeletal muscle tissue was rarely reported. Therefore, in this study, we present an interpenetrating network (IPN) hydrogel with fast stress relaxation for 3D bioprinting engineered skeletal muscle via a printing gel-in-gel strategy. Such IPN hydrogels with tunable fast stress relaxation resulted in high 3D cellular proliferation and adequate differentiation in vitro. Besides, the 3D hydrogel-based scaffolds also enhance functional skeletal muscle regeneration in situ. We believe that this study provides several notable advances in tissue engineering that can be potentially used for skeletal muscle injury treatment in clinical.

Velvet antler polypeptide-loaded polyvinyl alcohol-sodium alginate hydrogels promote the differentiation of neural progenitor cells in 3D towards oligodendrocytes in vitro

Three-dimensional (3D) culture of neural progenitor cells (NPCs) in hydrogels represents a powerful means for recapitulating neurodevelopment, disease modelling and drug discovery. However, the differentiation of NPCs to oligodendrocytes in 3D scaffolds remains a great challenge. In this study, polyvinyl alcohol (PVA) - sodium alginate (SA) composite hydrogels intended for NPC culture in 3D were fabricated by ionic crosslinking between SA and calcium ions. It was demonstrated that adding PVA to the composite hydrogels resulted in increases in pore size and swelling rate and decreases in elastic moduli as the PVA proportion was enhanced. In addition, the composite hydrogels were biocompatible with mouse NPCs and improved the proliferation of the encapsulated NPCs compared with SA hydrogels. Moreover, when velvet antler polypeptides (VAPs), which were capable of facilitating the differentiation of NPCs to oligodendrocyte fate in 2D, were loaded into PVA-SA hydrogels, NPCs differentiated into neurons, astrocytes and oligodendrocytes, with the presence of VAPs promoting oligodendrogenesis in a dose-dependant manner. The present composite hydrogels provide a suitable scaffold for the construction of neural tissue engineering and neurological disease modelling.

Recent Progress on Biodegradable Tissue Engineering Scaffolds Prepared by Thermally-Induced Phase Separation (TIPS)

Porous biodegradable scaffolds provide a physical substrate for cells allowing them to attach, proliferate and guide the formation of new tissues. A variety of techniques have been developed to fabricate tissue engineering (TE) scaffolds, among them the most relevant is the thermally-induced phase separation (TIPS). This technique has been widely used in recent years to fabricate three-dimensional (3D) TE scaffolds. Low production cost, simple experimental procedure and easy processability together with the capability to produce highly porous scaffolds with controllable architecture justify the popularity of TIPS. This paper provides a general overview of the TIPS methodology applied for the preparation of 3D porous TE scaffolds. The recent advances in the fabrication of porous scaffolds through this technique, in terms of technology and material selection, have been reviewed. In addition, how properties can be effectively modified to serve as ideal substrates for specific target cells has been specifically addressed. Additionally, examples are offered with respect to changes of TIPS procedure parameters, the combination of TIPS with other techniques and innovations in polymer or filler selection.