3D bioprinted light responsive hydrogel materials for cartilage tissue analogues

Articular cartilage defects are a significant and health problem for millions worldwide, especially in an aging population. Effective cartilage regeneration remains elusive. A promising approach is to combine bioinks with human pluripotent stem cells that can be 3D printed to form hydrogels, as responsive, chondroprogenitor-containing materials for eventual transplantation into articular cartilage defects. A significant step towards this is the development of improved chondrogenic tissue analogues.
To generate articular chondrocytes from human pluripotent stem cells (hPSCs) in vitro chondrogenesis protocols rely on timed addition of growth factors to drive differentiation. Transforming growth factor-beta (TGF-b) and bone morphogenic protein (BMP) signals are crucial in specification of an articular phenotype over a hypertrophic phenotype. Optogenetics can be used as a tool for precise cell signalling manipulation. For example, recently an optogenetic BMP (optoBMP) system has been engineered into hPSCs, providing precise, spaciotemporal and reversible (blue) light driven activation of the BMP signalling pathway. Light will be harnessed to generate 3D chondrogenic tissue analogues with stable articular chondrocyte phenotype. Optogenically engineered hPSCs that can be stimulated by red and blue light will be combined with bioinks and fabricated into hydrogel structures using digital light processing (e.g., projection printing). Projection printing allows for the fabrication of spatially patterned regions in 3D, including stiffness, as well as patterned light stimulation of cells. Responsive inks, based on gelatin and hyaluronan will be developed that can change stiffness in response to light (for example, to increase in stiffness in defined regions to green light). This will enable signalling and stiffness to be orthogonally controlled in cell culture, and realise more realistic cartilage tissue analogues. The ability to control stiffness is particularly interesting as it mimics the behaviour of the cell niche of developing tissues.
Responsive gelatin and hyaluronan based hydrogel inks will be formed using click-chemistry approaches, e.g., gelatin-tetrazine and hyaluronan-norbornene systems, that click to form gels on mixing in the presence of cells. Light responsive moieties will be incorporated to the gels that allow tuneable stiffness control. Importantly, the gelatin and hyaluronan hydrogel system can be enzymatically degraded, allowing RNA sequencing of cells. RNA sequencing will be conducted on cells that have been exposed to light stimulation in the hydrogels and the effect of change in stiffness on cell response assessed. 3D translation of opto-engineered cells could generate 3D cartilage analogues with spatiotemporal control over cell phenotype to aid in achieving appropriate zonal extracellular matrix, a significant step towards realising improved cartilage disease models and cartilage tissue regeneration.
Biomaterials and Tissue Engineering - The application of engineering methods to create environments and or materials that promote cell or tissue growth and function, in vitro. And also Synthetic Biology (also now termed Engineering Biology)- the application of engineering tools and principles to design and engineer novel biologically based parts.
The project tackles the development of cartilage tissue analogues, and uses optogenetic approaches (synthetic biology), combined with novel materials development - light responsive hydrogels.
Further, Engineering Biology has been identified as one of the five most critical technologies to the UK, in government policy paper The UK Science and Technology Framework, published February 2024.
The project also aligns with EPSRC remit areas: Healthcare Technologies Theme; Advanced Materials Theme, and Manufacturing technologies.