Determining the Correlation Between Aging and Cellular Mechanics

The mechanical behavior of a cell is both a consequence and regulatory factor of biological function and cellular architecture. Researchers globally are investigating the forces that cells generate and sustain within their environment to provide a cellular-level perspective on pathologies among other pressing research questions. Cellular Traction Forces (CTFs) are critical to the physiology of cells, through their structural support, and facilitation of migration within tissues. These aforementioned features have been associated with aging due to gradual physiological cellular decay and warrant further investigation to expand etiological understanding.<br/><br/>This study investigates this correlation on both a cellular and macroscopic(tissue) level. At the cellular level, testing for cell morphology, cell proliferation, and cell modulus through Atomic Force Microscopy (AFM) were conducted. Macroscopically, fibroblasts from three distinct age groups–neonatal, 29-years, and 71-years–were placed within collagen gel individually to resemble the dermis layer of skin. The collagen gel was then rimmed to perform consequent gel contraction. Microscopically, analysis using Digital Image Speckled Correlation (DISC) was also conducted to quantify the cell mechanical force exerted on the surrounding extracellular matrix. Morphological analysis was conducted displaying a physical difference within the distinct cell types such that the neonatal and 71 y.o. cells have a more slender and elongated structure compared to the 29 y.o. cells’ more condensed and compact shape. After a three-day cell proliferation assay was conducted, it was determined that the 29 y.o. cells displayed the greatest and fastest cell proliferation. Cell modulus, the biophysical property that describes the cell elasticity and measures their resistance to strain4. The neonatal, 29 y.o, and 71 y.o. cells had moduli of 1, 1.264, and 2.022 respectively. It was found that the 71 y.o. cells had the greatest modulus and resistance to deformation. Over a period of 9 hours, and with final imaging at the 24 hour mark, imaging was conducted to observe the cellular gel contraction as a reflection of the CTFs. The collagen gel area contraction results demonstrated that the 29 y.o. and 71 y.o. cells produced a similar trend in gel area rate, whereas the neonatal cells demonstrated a smaller rate of decrease of the gel area. Fibroblasts incorporated with red fluorescent beads were plated atop mtG-crosslinked-gelatin and the CTFs are visualized through the observation of bead displacement during EVOS imaging, and heat maps were generated using DISC algorithm where the 29 y.o. cells displayed the greatest force.<br/><br/>Ongoing experimentation and future steps include conducting further examination on cell displacement using DISC, as well as conducting Polymerase Chain Reaction to identify how the 3 different aged cells promote angiogenesis to provide critical insight into wound healing given that younger, more elastic skin has been found to allow for a smoother and faster wound healing process when compared to older, more rigid skin.