The poor regenerative ability of injured tendon tissues remains a clinical challenge. However, decellularized extracellular matrix (ECM) combined with stem cells shows promise. In contrast to bovine and porcine ECM, marine-derived decellularized ECM has several advantages; it is easily obtained, poses less biological risk, and is not contraindicated on religious grounds. This study successfully fabricated decellularized tilapia fish skin (DTFS) with copious preserved collagen fibers and natural pore structures. The outer layer is smooth and dense, while the inner layer has a soft structure with a rough surface. After crosslinking with 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide (EDC) and N-hydroxysuccinimide (NHS), crosslinked DTFS (C-DTFS) showed improved mechanics in dry and wet conditions. In vitro, the leach liquor of crosslinked DTFS showed no cytotoxicity and promoted migration and tenonic differentiation of tendon-derived stem cells (TDSCs). Meanwhile, TDSCs seeded in the inner surface of DTFS maintained viability, differentiated, and exhibited spreading. Furthermore, cell-seeded scaffolds guided the regeneration of tendon tissue in a rat Achilles tendon defect model. Our results suggest that DTFS combined with TDSCs is a novel and promising therapeutic option for tendon tissue engineering.

The integrative regeneration of both articular cartilage and subchondral bone remains an unmet clinical need due to the difficulties of mimicking spatial complexity in native osteochondral tissues for artificial implants. Layer-by-layer fabrication strategies, such as 3D printing, have emerged as a promising technology replicating the stratified zonal architecture and varying microstructures and mechanical properties. However, the dynamic and circulating physiological environments, such as mass transportation or cell migration, usually distort the pre-confined biological properties in the layered implants, leading to undistinguished spatial variations and subsequently inefficient regenerations. This study introduced a biomimetic calcified interfacial layer into the scaffold as a compact barrier between a cartilage layer and a subchondral bone layer to facilitate osteogenic–chondrogenic repair. The calcified interfacial layer consisting of compact polycaprolactone (PCL), nano-hydroxyapatite, and tasquinimod (TA) can physically and biologically separate the cartilage layer (TA-mixed, chondrocytes-load gelatin methacrylate) from the subchondral bond layer (porous PCL). This introduction preserved the as-designed independent biological environment in each layer for both cartilage and bone regeneration, successfully inhibiting vascular invasion into the cartilage layer and preventing hyaluronic cartilage calcification owing to devascularization of TA. The improved integrative regeneration of cartilage and subchondral bone was validated through gross examination, micro-computed tomography (micro-CT), and histological and immunohistochemical analyses based on an in vivo rat model. Moreover, gene and protein expression studies identified a key role of Caveolin (CAV-1) in promoting angiogenesis through the Wnt/β-catenin pathway and indicated that TA in the calcified layer blocked angiogenesis by inhibiting CAV-1.

Alginate oligosaccharide (AOS) has the function to inhibit tumor progression and the sulfated modification can enhance the antitumor activity. To date, the function and mechanism of sulfated AOS (AOS-SO₄) in tumors remain largely elusive. We prepared AOS by the enzymatic degradation of alginate, collected AOS-SO₄by sulfating following the canonical procedure. Using these materials, in vitro assays showed that both AOS and AOS-SO₄elicited antitumor effects in osteosarcoma cells. Sulfated modification significantly enhanced the antitumor activity. In addition, AOS-SO₄had obvious effects on cell cycle arrest, apoptosis, and autophagy induction in vitro and in vivo. Mechanistically, we observed that AOS-SO₄treatment triggered proapoptotic autophagy by inhibiting MEK1/ERK/mTOR signaling. The ERK activator reversed AOS-SO₄-induced autophagy. More importantly, we found that KSR1 interacted with MEK1 and functioned as a positive regulator of MEK1 protein in osteosarcoma cells. High KSR1 expression was significantly associated with poor survival in osteosarcoma patients. Together, these results suggest that AOS-SO₄has a better antitumor effect in osteosarcoma by inhibiting MEK1/ERK/mTOR signaling, which is KSR1-dependent; thus, AOS-SO₄can be a new potential therapeutic candidate for the treatment of osteosarcoma.

Decellularized cartilage scaffold (DCS) is an emerging substitute for cartilage defect application. However, it is hard to preserve an intact structure of such scaffolds derived from terrestrial animals, because of their dense and compact constitution. In contrast, squid (Dosidicus gigas) cranial cartilage, which possesses a relatively loose structure, could be easily decellularized using mild conditions and it retains the original microstructures of extracellular matrix (ECM). Herein, decellularized squid cranial cartilage scaffold (DSCS) was fabricated successfully after substantially removing the cells, which contained abundant ECM components (proteoglycans and type II collagen). Microscopic structure results showed that the DSCS possesses a relatively smooth and dense surface with a favorable interconnected inner porous structure for cell growth. DSCS exhibited excellent biomechanics and hydrophilicity. In vitro experiments indicated that the scaffold extracts were not toxic to cells, and were amenable to chondrocyte migration. Meanwhile, chondrocytes seeded in DSCS could maintain a favorable viability and present a spreading morphology. Furthermore, the in vivo experiments revealed that both cell-free scaffold and cell-laden scaffold exert promotive effects for the regeneration of cartilage in a full-thickness rabbit cartilage defect model. Taken together, these results suggested that DSCS presents a novel and promising cell-free therapeutic choice for cartilage tissue engineering.