Abstract
Osteoarthritis is the most prevalent joint disease, affecting 1 out of 15 people in the world [1]. Osteoarthritis is characterised by joint inflammation due to chondral lesions. An active sport practice, a serious fall, or a surgical intervention can induce these lesions, which very often evolve into osteoarthritis. Since articular cartilage, especially knee cartilage, presents very limited “self-healing” properties, one approach to prevent osteoarthritis is to treat the chondral lesions before the apparition of the disease. Herein, we present a potential therapeutic solution to treat chondral lesions by producing new cartilage in situ.We developed collagen microspheres as an injectable carrier to deliver cells at the lesion site. Mesenchymal stromal cells (MSCs) were chosen because of their ability to differentiate into chondrocytes producing neo-cartilage [2]. However, a gene (RunX2) involved in MSCs differentiation also induces late chondrocyte hypertrophy and ossification [3,4]. Here, we intend to use a silencing RNA (siRunX2) to silence this gene. The siRNA lipid vector (lipoplex) is attached to the matrix through an MMP-13-cleavable peptide, and its delivery should be triggered by the early secretion of matrix metalloproteinase-13 (MMP-13) by hypertrophic chondrocytes (Figure 1). We anticipate that this on-demand delivery of siRNA to chondrocytes will help maintain their mature phenotype.Thus, we first optimized the sequence by synthesizing a peptide library (based on the peptidase database, MEROPS) for which we measured MMP-13 specificity and selectivity against other MMPs. To that end, peptides were evaluated in a novel enzymatic assay, named indirect fluorescence measurement. Kinetics were confirmed by LC–MS. Furthermore, conjugation of the peptide to the lipoplexes and to the injectable carrier was studied. Peptides were also modified with fluorophores to study the release of the lipoplexes in the presence of MMP-13.This promising strategy could bring the patient a sustainable treatment for osteoarthritis and provide new tools to tissue engineering and drug delivery sciences.References1. WHO, 2019.2. Mathieu M, et al. Eur Cells Mater. 2014.3. Scotti C, et al. Proc Natl Acad Sci U S A. 2010.4. Gordeladze JO, et al. Exp Cell Res. 2008.