LAUSR

Introduction Owing to their ability to secrete anti-inflammatory and immuno-modulatory factors Mesenchymal Stromal Cells (MSCs) are an attractive tool for the treatment of osteoarthritis. Considering cell death and the risk of cell leakage upon intra-articular injection, MSCs encapsulation therefore could protect cell from death, avoid cell effusion outside the articular space, and supply a suitable 3D microenvironment supporting the biological activity of MSCs. Objectives Our objective was to develop a method of MSC encapsulation compatible with their intra-articular injection through a 26G needle. Methods Human adipose-derived stem cells (hASCs) were encapsulated via a micromolding method. We first manufactured polydimethylsiloxane chips containing 1600 micromolds with a circular shape, 150 µm in diameter and 100 µm in depth. For cell encapsulation, a solution of 2% alginate (w/v) containing 3 million of hASCs per mL polymer was deposited onto the chips, loaded in the moulds either by sedimentation or centrifugation and crosslinked using an agarose gel charged with CaCl2. The number of encapsulated cells was evaluated by a CyQUANT assay immediately and 24 hour after encapsulation. The impact of encapsulation on metabolic activity was determined by a presto blue assay 24 hours after encapsulation and 24 hour after their injection through a 26G needle. Results We successfully obtained cylindrical alginate microparticles presenting a diameter of 103±0.7 µm. Using cell quantification, we determined that the centrifugation method allowed the encapsulation of 30 333 (±5552) cells within one chip versus 6056 (±2862) by sedimentation. Cell number and metabolic activity remained stable for 24 hours after encapsulation. We also demonstrated that injection through a 26G needle had no impact on the viability of encapsulated cells. Conclusions Our results show that micromolding allows hASCs encapsulation into alginate particles injectable through a 26 G needle without impacting cell viability. Future work will focus on evaluating in vitro long-term encapsulated cell survival and functionality. In case of success, we will then consider intra-articular injection in an animal model of osteoarthritis. Disclosure of interest None declared