Three-dimensional cartilage tissue regeneration system harnessing goblet-shaped microwells containing biocompatible hydrogel

Glucosamine-loaded injectable hydrogel promotes autophagy and inhibits apoptosis after cartilage injury

The ability of cartilage to regenerate and repair is limited. N-acetyl- d-glucosamine (GlcNAc) is a nutritional supplement commonly used to activate chondrocytes. To prolong the duration of action of GlcNAc and improve its curative effect after cartilage injury, a GlcNAc thermosensitive hydrogel is prepared based on Pluronic F127 (PF127). The physicochemical properties results indicate that this hydrogel is injectable and retards the release of GlcNAc. Further, the therapeutic benefits of GlcNAc hydrogel are detected through intra-articular injection in rat specimens with cartilage injury. Behavioral experiments results indicate that the rats treated with GlcNAc hydrogel had longer step lengths, smaller foot angles and slower fall times. Compared with the sham group, the expression of Sox9 was 1.5 times and the level of collagen II was 2.4 times in the hydrogel treated group. Terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) staining result confirmed that the GlcNAc hydrogel reduce apoptosis by about 50%. Our results of immunohistochemical staining, Western blotting assays and enzyme activity detection all suggested that GlcNAc hydrogel reduce the expression of cleaved-caspase3 and caspase8 (Compared to the sham group, the protein contents were reduced by about 50% in the GlcNAc hydrogel group). We also found that GlcNAc hydrogel activates autophagy through ERK signal pathway. The results of Western blotting indicated that GlcNAc hydrogel increase the levels of LC3B and Becline1 (hydrogel group & sham group, LC3B: 1.56 ± 0.07 & 1.00 ± 0.14; Becline1: 1.98 ± 0.07 & 1.00 ± 0.13). Whereas, the content of P62 reduced after GlcNAc hydrogel treatment, the relative level in sham group and hydrogel group are 1.00 ± 0.02 and 0.73 ± 0.06. Our results revealed that the number of P-ERK positive cells in the hydrogel group (57.36 ± 3.56%) was higher when compared with the sham (24.82 ± 2.72%). And, the ratio of P-ERK and ERK was higher than that in the sham group (1.48 ± 0.07 & 1.00 ± 0.08). The GlcNAc thermosensitive hydrogel is a promising and sustainable drug delivery system for intra-articular injection in the treatment of cartilage injury.

A superhydrophobic chip integrated with an array of medium reservoirs for long-term hanging drop spheroid culture

Hanging drop (HD) is one of the most popular methods used for forming three-dimensional (3D) cell spheroids. However, conventional hanging drop systems are only applicable for short-term spheroid culture due to their inconvenience in exchanging cell culture media. Here we present a medium-reservoir-integrated superhydrophobic (MRI-SH) chip for long-term HD spheroid cultures. The device consists of two main components: i) a patterned superhydrophobic (SH) surface containing an array of wettable spots which anchor arrays of droplets of cell suspension, and ii) an array of chambers that serve as medium reservoirs, both interconnected via an array of thru-holes. This configuration provides two distinct advantages over conventional HD configurations: i) the high wettability contrast of the SH pattern on the chip leads to the formation and adhesion of nearly spherical hanging droplets on its surface, which minimizes interactions between the liquid and the substrate; ii) the integrated chambers provide large volumes of medium to maintain longer culture durations. Using this device, spheroids of MHCC97H cells were successfully formed, and the cultured spheroids could maintain high viability for up to 30 days and exhibited enhanced spheroid morphology compared to those cultured in the conventional HD systems. STATEMENT OF SIGNIFICANCE: This paper presents a medium-reservoir-integrated superhydrophobic hanging drop (HD) platform for the long-term culture of spheroids with enhanced morphology. By monolithically integrating medium reservoirs and a patterned SH surface into a single device, this HD platform can not only produce high-quality spheroids, but also permit them to sustain high viability for up to 30 days without the need for tedious medium replenishment. We believe that such a platform will be valuable in a wide range of biological or biomedical applications, including tissue engineering, regenerative medicine, and drug discovery.

Perichondrium-inspired permeable nanofibrous tube well promoting differentiation of hiPSC-derived pellet toward hyaline-like cartilage pellet

The pellet formation has been regarded as a golden standard forin vitrochondrogenic differentiation. However, a spatially inhomogeneous chondrogenic microenvironment around a pellet resulted from the use of a traditional impermeable narrow tube, such as the conical tube, undermines the differentiation performance and therapeutic potential of differentiated cartilage pellet in defective articular cartilage treatment. To address this drawback, a perichondrium-inspired permeable nanofibrous tube (PINaT) well with a nanofibrous wall permeable to gas and soluble molecules is proposed. The PINaT well was fabricated with a micro deep drawing process where a flat thin nanofibrous membrane was transformed to a 3.5 mm deep tube well with a ∼50µm thick nanofibrous wall. Similar toin vivoperichondrium, the PINaT well was found to allow oxygen and growth factor diffusion required for chondrogenic differentiation across the entire nanofibrous wall. Analyses of gene expressions (COL2A1, COL10A1, ACAN, and SOX9), proteins (type II and X collagen), and glycosaminoglycans contents were conducted to assess the differentiation performance and clinical efficacy of differentiated cartilage pellet. The regulated spatially homogeneous chondrogenic microenvironment around the human induced pluripotent stem cell-derived pellet (3 × 10⁵cells per pellet) in the PINaT well remarkably improved the quality of the differentiated pellet toward a more hyaline-like cartilage pellet. Furthermore, an accelerated chondrogenic differentiation process of the pellet produced by the PINaT well was achieved for 14 days, demonstrating a hyaline cartilage-specific marker similar to the control pellet differentiated for 20 days. Finally, the enhanced clinical efficacy of the hyaline-like cartilage pellet was confirmed using an osteochondral defect rat model, with the repaired tissue resembling hyaline cartilage rather than fibrous cartilage after 8 weeks of regeneration.

Human Adipose-Derived Stromal/Stem Cell Culture and Analysis Methods for Adipose Tissue Modeling In Vitro: A Systematic Review

Human adipose-derived stromal/stem cells (hASC) are widely used for in vitro modeling of physiologically relevant human adipose tissue. These models are useful for the development of tissue constructs for soft tissue regeneration and 3-dimensional (3D) microphysiological systems (MPS) for drug discovery. In this systematic review, we report on the current state of hASC culture and assessment methods for adipose tissue engineering using 3D MPS. Our search efforts resulted in the identification of 184 independent records, of which 27 were determined to be most relevant to the goals of the present review. Our results demonstrate a lack of consensus on methods for hASC culture and assessment for the production of physiologically relevant in vitro models of human adipose tissue. Few studies have assessed the impact of different 3D culture conditions on hASC adipogenesis. Additionally, there has been a limited use of assays for characterizing the functionality of adipose tissue in vitro. Results from this study suggest the need for more standardized culture methods and further analysis on in vitro tissue functionality. These will be necessary to validate the utility of 3D MPS as an in vitro model to reduce, refine, and replace in vivo experiments in the drug discovery regulatory process.

Autonomous spheroid formation by culture plate compartmentation

Scaffold-free 3D cell cultures (e.g. pellet cultures) are widely used in medical science, including cartilage regeneration. Their drawbacks are high time/reagent consumption and lack of early readout parameters. While optimisation was achieved by automation or simplified spheroid generation, most culture systems remain expensive or require tedious procedures. The aim of this study was to establish a system for resource efficient spheroid generation. This was achieved by compartmentation of cell culture surfaces utilising laser engraving (grid plates). This compartmentation triggered autonomous spheroid formation via rolling-up of the cell monolayer in human adipose-derived stem cells (ASC/TERT1) and human articular chondrocytes (hAC)-ASC/TERT1 co-cultures, when cultivated on grid plates under chondrogenic conditions. Plates with 3 mm grid size yielded stable diameters (about 300 μm). ASC/TERT1 spheroids fully formed within 3 weeks while co-cultures took 1-2 weeks, forming significantly faster with increasing hAC ratio (p<0.05 and 0.01 for 1:1 and 1:4 ASC/TERT1:hAC ratio respectively). Co-cultures showed slightly lower spheroid diameter, due to earlier spheroid formation and incomplete monolayer formation. However, this was associated with more regular matrix distribution in the co-culture. Both showed differentiation capacity comparable to standard pellet culture in (immune-)histochemistry and RT-qPCR. To assess usability for cartilage repair, spheroids were embedded into a hydrogel (fibrin), yielding cellular outgrowth and matrix deposition, which was especially pronounced in co-cultures. The herein presented novel cell culture system is not only a promising tool for autonomous spheroid generation with the potential of experimental and clinical application in tissue engineering but also for high-throughput analysis for both pharmaceutical and therapeutic uses.

Rapid fabrication of sieved microwells and cross-flow microparticle trapping

The use of microwells is popular for a wide range of applications due to its' simplicity. However, the seeding of conventional microwells, which are closed at the bottom, is restricted to gravitational sedimentation for cell or particle deposition and therefore require lengthy settling times to maximize well occupancy. The addition of microfluidics to the capture process has accelerated cell or particle dispersion and improved capture ability but is mostly limited to gravitationally-driven settling for capture into the wells. An alternative approach to conventional closed-microwells, sieved microwells supersedes reliance on gravity by using hydrodynamic forces through the open pores at the bottom of the microwells to draw targets into the wells. We have developed a rapid fabrication method, based on flow lithography techniques, which allows us to easily customize the mesh pore sizes in a simple two-step process. Finally, by combining this microwell design with cross-flow trapping in a microfluidic two-layered channel, we achieve an 88 ± 6% well occupancy in under 10 s.