Abstract
The degeneration of the intervertebral disc (IVD) is the primary cause for low back pain, which is treated with surgical interventions such as spinal fusion. A strategy to develop a regenerative and non-invasive treatment requires an injectable cell carrier system. Our efforts have focussed on developing a hyaluronan (HA)-based hydrogel system that can be used as a carrier for therapeutic agents in annulus fibrosus (AF) repair. High molecular weight HA at 20mM is chemically crosslinked with varying concentrations of 4-arm PEG. Hydrogels were optimised for degree of crosslinking, stability and rheological properties. Subsequently, the morphology and viability of the human AF cells encapsulated in the hydrogels were studied. The highest crosslinking was seen with 4-arm PEG at 1:1 HA:PEG molar ratio. This was the most stable against enzymatic and hydrolytic degradation, and had greater swelling property, which is desired as the degeneration decreases the water retention capability of the IVD. The gelation time, important for in situ injectability, was under five minutes for all formulations. Storage modulus was between 0.4–1.1 kPa. Compared to 2D cultures, cells were rounder after encapsulation, mimicking the native microenvironment, and had the similar metabolic activity for seven days. AF cells encapsulated in HA/4-arm PEG hydrogel were stiffer compared to the nucleus pulposus (NP) cells encapsulated similarly as measured with Brillouin microscopy. The 4-arm PEG crosslinked HA-based hydrogel system promises to be a candidate for an injectable carrier for cells for AF repair and regeneration.
