A Synthetic Gene Circuit for Self-Regulating Delivery of Biologic Drugs in Engineered Tissues.

Transient, resolving inflammation plays a critical role in tissue repair and regeneration. In the context of joint disease, however, chronic inflammation following injury or with osteoarthritis can lead to irreversible articular cartilage degradation and joint pain. Developing tissue engineering strategies for the regeneration of articular cartilage remains challenging due to the harsh inflammatory environment of an injured or arthritic joint, which can promote degradation of engineered tissues as well as native articular cartilage. Here, we developed an artificial gene circuit for controlled, cell-based delivery of biologic drugs, based on a nuclear factor kappa-light-chain-enhancer of activated B cells (NF-B)-responsive synthetic promoter. Using lentivirus-based gene therapy, we engineered murine induced pluripotent stem cells (iPSCs) capable of attenuating inflammation through controlled release of an anti-inflammatory drug, interleukin-1 receptor antagonist (IL-1Ra), subsequently inhibiting gene circuit activation in a self-regulating manner. Murine iPSCs were transduced with the synthetic gene circuit either in monolayer or through biomaterial-mediated transduction. Cells were maintained in monolayer or differentiated into cartilage constructs and stimulated with different doses of interleukin 1 alpha (IL-1) to determine the ability of this synthetic NF-B responsive system to inhibit inflammation and protect tissue-engineered constructs. In response to IL-1, cells produced high levels of IL-1Ra, which inhibited inflammatory signaling and protected tissue-engineered cartilage from proteoglycan degradation. Our results show that the combination of gene therapy and tissue engineering can be used to successfully create iPSCs capable of producing biologic drugs in a controlled manner. This self-regulating system provides a tool for cell-based drug delivery as the basis for a novel therapeutic approach for a variety of diseases. Impact Statement We engineered a synthetic transcription system based on nuclear factor kappa-light-chain-enhancer of activated B cells signaling that can attenuate the effects of the inflammatory cytokine interleukin (IL)-1 in a self-regulating manner. This system responds in a time- and dose-dependent manner to rapidly produce therapeutic levels of IL-1 receptor antagonist (IL-1Ra). The use of lentiviral gene therapy allows this system to be utilized through different transduction methods and in different cell types for a variety of applications. Broadly, this approach may be applicable in developing autoregulated biologic systems for tissue engineering and drug delivery in a range of disease applications.