Nanohydrogel based on hyaluronic acid and cholesterol for the delivery of anti-inflammatory therapeutics

Rheumatoid arthritis (RA) is a chronic inflammatory autoimmune disease characterised by immune cell infiltration into the synovium and its hyperplasia, with progressive cartilage destruction and bone erosion, resulting in joint ankylosis1. Currently, two main classes of treatment are available: disease-modifying anti-rheumatic drugs (DMARDs) and glucocorticoids such as dexamethasone (DEX). Among the DMARDs, methotrexate (MET) is considered the anchor drug and a subcategory is represented by the Janus kinase inhibitors such as baricitinib (BAR), which have also been shown to be effective in treating this pathology. The aim of this project is to use a novel nanogel (NHs) system based on an amphiphilic derivative of hyaluronic acid (HA) for the delivery of anti-inflammatory therapeutics for the treatment of RA. The purpose of HA is to exploit the interaction with its receptor, CD44, which is over-expressed in activated macrophages involved in the inflammatory process. This strategy promotes better internalisation of the drug into the cells and a more effective treatment, while overcoming the limitations of the oral route in favour of intravenous and intra-articular administration. The (HA) backbone was derivatised with hydrophobic cholesterol moieties, resulting in a new derivative (HA-CH) capable of self-assembly in nanogel form after a standard autoclave cycle2. Three different drugs (DEX, MET and BAR) were loaded inside the NHs with a good encapsulation efficiency (see Figure 1). A viability assay was performed on the macrophages raw 264.7 to assess the safety of the NHs and no decrease in cell viability was observed. ELISA test to quantify the main cytokines involved in RA confirmed the anti-inflammatory effect of the formulation. Flow cytometry study and confocal microscopy experiment revealed an increasing in the amount of NHs internalized in raw 264.7 cells activated to inflammation compared to the non-activated ones, at the longest incubation time; it is reasonable to assume that this is due to a receptor mediated internalization process, which involve CD44 and that is slower than other mechanism of internalization. In this work, we have shown that HA-CH NHs can entrapped efficiently anti-inflammatory compounds commonly used in the treatment of rheumatoid arthritis, the efficacy of the treatment in reducing the inflammatory cytokines is preserved when the drug is encapsulated in the nanosystems. Moreover, the presence of hyaluronic acid as the main component appears to facilitate the internalization of NHs within immune system cells activated to inflammation, leading to the development of an efficient and effective nanocarrier for the delivery of therapeutics in rheumatoid arthritis.