Metabolic control of extracellular matrix synthesis

PROJECT SUMMARY/ABSTRACT The extracellular matrix (ECM) is crucial for maintaining the connective tissue in all organs, supporting tissue homeostasis and repair. When tissue homeostasis is disrupted by wounds or injury, fibroblasts become activated to help repair the damage and restore tissue structure by producing fibrillar collagens and other ECM molecules. If fibroblasts produce insufficient collagen, it could lead to nonhealing, chronic wounds. Conversely, excessive collagen synthesis can lead to fibrosis and impairment of organ function, a major healthcare challenge. How fibroblasts maintain the intricate balance between underproduction and overproduction of ECM remains an important yet unresolved question. A key challenge is understanding how fibroblasts regulate the production of ECM proteins, particularly collagen. An important but often overlooked aspect of ECM production is that fibroblasts must meet substantial metabolic demands to produce ECM biomass. These metabolic requirements differ from those for cellular biomass generation during proliferation, including a high demand for the non-essential amino acids glycine and proline for synthesizing collagens. We and others have demonstrated that activated fibroblasts upregulate nutrient uptake and metabolic flux into glycine and proline biosynthesis and that these pathways are required for collagen production. Despite these advances, little is known about how fibroblasts meet the metabolic demands of ECM synthesis physiologically during tissue repair. To address this gap, my research program aims to determine the physiological nutrients and metabolic pathways required for fibroblast ECM synthesis during tissue repair. The central question we will address over the next five years is: how do fibroblasts meet the nitrogen demands of collagen synthesis to drive tissue repair while tolerating toxicity from accumulating reduced nitrogen during this process? To answer this question, we have developed a novel experimental platform to trace nutrients directly into the ECM under physiological conditions. Leveraging this model, we will: (1) develop a long-term in vivo stable isotope tracing platform to determine the nitrogen sources for collagen synthesis during tissue repair; (2) understand how ECM synthesis associated metabolic rewiring allows fibroblasts to tolerate the accumulation of toxic metabolic waste products. Achieving these goals will provide fundamental insights into cellular metabolism and tissue repair and help lay the groundwork for strategies to modulate nutrients and their associated metabolic pathways to overcome healthcare challenges associated with insufficient or excessive ECM synthesis.