Fight Aging!

A few days ago, I noted a use of CRISPR to suppress chronic inflammation via epigenetic alterations that interfere with the signaling that promotes the inflammatory response. Here I'll point out a different, arguably more sophisticated approach to achieving the same end, also using CRISPR to achieve the necessary genetic edits, but in this case turning stem cells into regulators that damp down inflammatory signaling only when required. Rising levels of inflammation in aging are a contributing factor that speeds progression of most of the common age-related conditions. Finding ways to suppress this inflammation without further damaging the diminished immune response should prove to be broadly beneficial, though not as desirable an end goal as repairing the immune system as a whole, restoring its balanced and youthful function.

Chronic inflammatory diseases such as arthritis are characterized by dysregulated responses to pro-inflammatory cytokines such as interleukin-1 (IL-1) and tumor necrosis factor α (TNF-α). Pharmacologic anti-cytokine therapies are often effective at diminishing this inflammatory response, but due to the pleiotropic roles of TNF-α and IL-1 and their involvement in tissue homeostasis, the use of such therapies may have significant side effects, including increased susceptibility to infection as well as to autoimmune diseases. Moreover, excess inhibition of these cytokines can interfere with tissue regeneration and repair. Therefore, methods to dynamically deliver precisely calibrated doses of anti-inflammatory biologic therapies could improve treatments by combating cytokine-mediated pain and degeneration while spatially and temporally regulating the production of anti-cytokine drugs.

Here, we propose a regenerative medicine approach to the treatment of chronic inflammatory diseases by engineering cells that execute real-time, programmed responses to environmental cues, including pro-inflammatory cytokines. We used genome editing with the CRISPR/Cas9 system to create stem cells that antagonize IL-1- and TNF-α-mediated inflammation in an autoregulated manner. To achieve this, we selected to overtake the chemokine (C-C) ligand 2 (Ccl2) gene, which is also known as macrophage chemoattractant protein-1 (Mcp-1). The Ccl2 gene product regulates trafficking of monocytes/macrophages, basophils, and T lymphocytes. TNF-α and IL-1 serve as two of the most potent stimulators of Ccl2 expression; however, the persistence of Ccl2 expression depends on continued exposure to inflammatory cues, so resolution of inflammation results in rapid decay of Ccl2 transcripts.

Thus, we performed targeted gene addition of IL-1 and TNF-α antagonists at the Ccl2 locus to confer cytokine-activated and feedback-controlled expression of biologic therapies. These programmed stem cells were then used to engineer articular cartilage tissue to establish the efficacy of self-regulated therapy toward protection of tissues against cytokine-induced degeneration. We hypothesized that this approach of repurposing normally inflammatory signaling pathways would allow for transient, autoregulated production of cytokine antagonists in direct response to cytokine stimulation. This type of approach could provide an effective "vaccine" for the treatment of chronic diseases while overcoming limitations associated with delivery of large drug doses or constitutive overexpression of biologic therapies.

Link: http://dx.doi.org/10.1016/j.stemcr.2017.03.022