A one-step combined therapy for cartilage repair: development and performance assessment

With a progressively ageing and physically active population, joint ailments appear as responsible for activity limitation in adults 18-65 years of age, resulting in reduced quality of life and high socio-economic burden. Despite intensive efforts on the development of cartilage repair strategies worldwide, no current approach has proven full efficacy. In this work, it is proposed a novel one-step combined therapy where human adipose-derived stem/stromal cells (hASC)1 develop cartilage-like tissue within a novel hydrogel based on methacrylated gellan gum2 (mimsys® G). A complete xeno-free approach was developed and both in vitro and in vivo experiments were conducted to evaluate the performance of this system for focal cartilage repair. Human ASC (hASC xeno-free, irisbiosciences, Portugal) were expanded in xeno-free media until sub-confluency. mimsys G hydrogel (mimsys® G, irisbiosciencies) was prepared to yield a 2% w/V solution. Cells were encapsulated at 10x106 cells/mL, ionically crosslinked and cultured with or without chondrogenic induction for 21 days. Cell viability was determined by live/dead assay, and cell metabolic activity by MTS reduction. A in vivo study evaluated regeneration of focal cartilage lesions on a rabbit knee model for 8 weeks, using an autologous approach. Chondrogenic development was assessed on both in vitro and in vivo samples by histological staining of cartilage matrix using safranin O and immunolocalization of col-II. Expression of chondrogenic-related genes such as aggrecan, col-II and sox-9 (Applied Biosystems) were also determined at different time points. In vitro analysis of the combined system demonstrated high viability of the cells and progressive metabolic activity along culture (Fig.1A). Additionally, intense cartilage matrix deposition was detected by safranin O staining (Fig.1B). Correspondent up-regulation of chondrogenic genes were quantified. As for in vivo performance, analysis of rabbit cartilage lesion explants demonstrated filling of the defect and indication of focal regeneration. The proposed one-step combined therapy system demonstrated both safety and efficacy in vitro, revealed respectively, by high cell viability and intense cartilage development, demonstrated by expression of specific hyaline cartilage markers. The in vivo study revealed promising repair performance in focal cartilage lesions, suggesting a valuable approach for further therapeutic exploitation.