Robbins, Paul D.

ABSTRACT This manuscript summarizes over 30 years of research that began with the novel concept of using intra‐articular gene transfer to treat joint diseases. A notable milestone in this journey was the first‐in‐human transfer of an exogenous gene to a joint, accomplished by the ex vivo delivery of cDNA encoding the interleukin‐1 receptor antagonist (IL‐1Ra) to joints of patients with rheumatoid arthritis. Responding to lessons learned from this study and the prevailing clinical landscape we next developed an in vivo gene delivery system based on adeno‐associated virus (AAV) with osteoarthritis (OA) as the target disease. The safety and efficacy of this vector, sc‐rAAV2.5IL‐1Ra, was demonstrated in the joints of rats and horses leading to a successful IND application to the FDA. In this clinical trial (ClinicalTrials. gov Identifier: NCT02790723) sc‐rAAV2.5IL‐1Ra was injected at escalating doses into the knee joints of nine patients with OA who were followed for 1 year. This trial met its primary outcome measure, safety, and demonstrated that sustained expression of transgenic IL‐1Ra was possible after a single injection of the vector. Patient‐reported outcomes improved, but without a control group it is not possible to determine the influence of a placebo effect. This and other unresolved matters are addressed in a recently‐completed Phase Ib trial (ClinicalTrials. gov Identifier: NCT05835895). Beyond OA, sc‐rAAV2.5IL‐1Ra has potential therapeutic value in a variety of degenerative, inflammatory, fibrotic and autoimmune conditions. More generally, gene therapy holds much promise in the field of regenerative medicine, including regenerative orthopaedics. Trial Registration: (ClinicalTrials. gov Identifier: NCT02790723, NCT05835895).

ABSTRACT Objective Aging alters mesenchymal stromal cell (MSC) function, leading to dysregulated adipogenesis across tissues through biased lineage commitment. Fat redistribution from adipose depots to skeletal muscle and bone marrow is common in aging, but the underlying mechanisms remain unclear. This study investigates how MSC senescence modulates adipogenesis. Methods Primary MSCs were isolated from mouse skeletal muscle (FAPs), adipose tissue (APCs), and bone marrow (BMSCs). Single‐cell RNA sequencing was performed to compare transcriptional profiles among these populations. In vitro adipogenic differentiation and DNA damage–induced senescence assays were conducted, and the effects of autologous conditioned media from senescent MSCs on adipogenesis were assessed. Results Transcriptional analyses revealed that FAPs and APCs share greater similarity with each other than with BMSCs. All MSC types exhibited adipogenic potential and developed a robust senescence‐associated secretory phenotype (SASP) upon senescence induction. Conditioned media from senescent MSCs enhanced adipogenesis in BMSCs but inhibited adipogenesis in FAPs and APCs, revealing tissue‐specific paracrine effects. Conclusions MSC senescence reprograms adipogenic bias in a tissue‐dependent, non–cell autonomous manner, contributing to age‐related fat redistribution among adipose tissue, skeletal muscle, and bone marrow. Understanding these mechanisms may provide new therapeutic approaches for improving tissue composition and function in the context of aging.