Carlos A. Aguilar

Adult stem cells occupy a niche that contributes to their function, but how stem cells rebuild their microenvironment after injury remains an open‐ended question. Herein, biomaterial‐based systems and metabolic labeling are utilized to evaluate how skeletal muscle stem cells deposit extracellular matrix. Muscle stem cells and committed myoblasts are observed to generate less nascent matrix than muscle resident fibro‐adipogenic progenitors. When cultured on substrates that matched the stiffness of physiological uninjured and injured muscles, muscle stem cells increased nascent matrix deposition with activation kinetics. Reducing the ability to deposit nascent matrix by an inhibitor of vesicle trafficking (Exo‐1) attenuated muscle stem cell function and mimicked impairments observed from muscle stem cells isolated from old muscles. Old muscle stem cells are observed to deposit less nascent matrix than young muscle stem cells, which is rescued with therapeutic supplementation of insulin‐like growth factors. These results highlight the role of nascent matrix production with muscle stem cell activation.

Brain metastases are the most lethal progression events, in part because the biological processes underpinning brain metastases are poorly understood. There is a paucity of realistic models of metastasis, as current in vivo murine models are slow to manifest metastasis. Metabolic and secretory modulators of brain metastases utilizing two models consisting of in vitro microfluidic devices are delineated: 1) a blood–brain niche (BBN) chip that recapitulates the blood–brain‐ barrier and niche; and 2) a migration chip that assesses cell migration. Secretory cues provided by the brain niche that attract metastatic cancer cells to colonize the brain niche region are reported. Astrocytic Dkk‐1 is increased in response to brain‐seeking breast cancer cells and stimulates cancer cell migration. Brain metastatic cancer cells under Dkk‐1 stimulation increase gene expression of FGF‐13 and PLCB1. Further, extracellular Dkk‐1 modulates cancer cell migration upon entering the brain niche.