Restoring disc matrix homeostasis: Dual-miRNA and human platelet lysate as a novel therapeutic strategy

Intervertebral disc (IVD) degeneration is the predominant cause of low back pain, resulting from progressive extracellular matrix (ECM) degradation and establishment of a pro-catabolic microenvironment. microRNA (miRNA) delivery has potential to promote ECM restoration and curb the catabolic milieu. We previously demonstrated a robust anti-catabolic effect through the delivery of a dual-miRNA injectable therapy in ex vivo organ culture models of degeneration. However, to further enhance regenerative outcomes, additional stimulation, such as supplementation with human platelet lysate (HPL) may strengthen this therapeutic strategy. Supplementation of rat nucleus pulposus (NP) cells with the dual-miRNA-FLR-149-5p mimic and miRNA-221-3p inhibitor and HPL was assessed in monolayer and ex vivo organ culture modelling mild degeneration. To evaluate the translatability of our approach, a tuneable patient NP cell-laden NP-ECM gel analogue was developed. For all models, key ECM constituents and matrix-degrading proteins were assessed biochemically, histologically, and using immunofluorescence. HPL supplementation combined with FLR-miRNA-149-5p and 221-3p inhibitor resulted in increased ECM regenerative proteins, SRY-box transcription factor 9 (SOX9), and aggrecan, while suppressing catabolic factors from matrix-degrading enzymes disintegrin and metalloproteinase with thrombospondin motifs (ADAMTS) and matrix metalloproteinases (MMPs). Importantly, rat and human culture models were consistent in their response, highlighting the clinical translatability of our models and therapeutic strategy. Combined delivery of dual-miRNA with HPL delivery in rat and human models of mild degeneration enhanced expression of restorative ECM proteins while suppressing matrix-degrading factors. These findings highlight a novel and promising therapeutic strategy for the treatment of early-stage IVD degeneration.