Browsing by Author "Ganji, Elahe"
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Item Growth and mechanobiology of the Achilles enthesis in mice(University of Delaware, 2021) Ganji, ElaheEntheses are connective tissues that connect tendon to bone, two vastly different hierarchical materials with different structural and mechanical properties. As a result of this material mismatch, entheses are prone to local peaks in mechanical stress (stress concentrations) that increase their susceptibility to overuse injuries, especially during rapid growth (postnatal maturation) and in young athletes. The enthesis matures postnatally in a mechanoadaptive process, similar to the growing bone, and forms a graded transition to dampen the stress concentrations at the attachment site. Despite decades of research, the key biological and mechanoadaptive processes that govern the adaptation of the enthesis under repeated loading and onset of injury during its postnatal maturation remain unknown. ☐ The objective of this research was to investigate the role of mechanical and biological cues on the mechanoadaptation of growing and adult entheses. I did that through four main aims: (1) developing and confirming the feasibility and repeatability of a novel non-invasive in vivo model for repeated loading of the tendon and enthesis, using optogenetics; (2) investigating the age-dependent mechanically-induced structural and functional adaptation of the enthesis during growth and adulthood; (3) exploring the structural and functional relationships and possible mechanisms of damage (i.e., disrupted interdigitation vs. collagen denaturation) in disruption of the toughening mechanism of the maturing enthesis; and (4) identifying FGFs signaling, a known mediator of bone growth, as a critical regulator of the structural gradation, and therefore, mechanical properties of maturing entheses. ☐ This study is innovative in taking an interdisciplinary approach to put forth a novel model for skeletal adaptation to loading during growth, elucidating the structural adaptation of maturing and adult enthesis under repeated loading, and proposing new biological pathways involved in the mechanoadaptation of the maturing enthesis. The results and tools developed in this work can be used to investigate the adaptation of the enthesis by investigating the mechanobiology of enthesis formation, with the long-term goal of improving the diagnosis and treatment of overuse injuries in maturing attachment.Item Maize brace root mechanics vary by whorl, genotype, and reproductive stage(Annals of Botany, 2022-03-03) Hostetler, Ashley N.; Erndwein, Lindsay; Ganji, Elahe; Reneau, Jonathan W.; Killian, Megan L.; Sparks, Erin E.Background and Aims: Root lodging is responsible for significant crop losses world-wide. During root lodging, roots fail by breaking, buckling, or pulling out of the ground. In maize, above-ground roots, called brace roots, have been shown to reduce root lodging susceptibility. However, the underlying structural-functional properties of brace roots that prevent root lodging are poorly defined. In this study, we quantified structural mechanical properties, geometry, and bending moduli for brace roots from different whorls, genotypes, and reproductive stages. Methods: Using 3-point bend tests, we show that brace root mechanics are variable by whorl, genotype, and reproductive stage. Key Results: Generally, we find that within each genotype and reproductive stage, the brace roots from the first whorl (closest to the ground) had higher structural mechanical properties and a lower bending modulus than brace roots from the second whorl. There was additional variation between genotypes and reproductive stages. Specifically, genotypes with higher structural mechanical properties also had a higher bending modulus, and senesced brace roots had lower structural mechanical properties than hydrated brace roots. Conclusions: Collectively these results highlight the importance of considering whorl-of-origin, genotype, and reproductive stage for quantification of brace root mechanics, which is important for mitigating crop loss due to root mechanical failure.