title: In vivo simultaneous evaluations of sarcomere imaging and muscle fiber tension.
abstract: Muscle fiber tension and sarcomere length play critical roles in regulating muscle functions and adaptations under pathological conditions. However, methods are lacking to quantify these two variables simultaneously in vivo. A novel force microscope was developed with the unique capabilities of estimating muscle fiber tension and acquiring sarcomere images simultaneously in vivo. The force microscope consisting of a custom microscopic imaging system and a force sensor was used to quantify in vivo sarcomere length, muscle fiber tension and stress of the tibialis cranialis muscle at plantar-flexed and dorsi-flexed positions from 11 rat hind limbs. Results showed that sarcomere images and fiber tension could be measured together in vivo with significantly higher muscle fiber tension and stress and longer sarcomere length at the plantar-flexed position when compared to their counterparts at the dorsi-flexed position. The fiber tension estimated using the force microscope had close agreement with the direct measurements of the fiber tension. The present force microscope with simultaneous characterizations of fiber tension and sarcomere imaging provides us a useful in vivo tool to investigate the roles of muscle tension in regulating sarcomere and muscle fiber functions under physiological and pathological conditions.
authors.affiliation: Sensory Motor Performance Program, Rehabilitation Institute of Chicago, Chicago, IL, USA; Department of Physical Therapy, University of Massachusetts Lowell, Lowell, MA, USA.
authors.forename: Yi-Ning
authors.initials: YN
authors.lastname: Wu
authors.affiliation: Sensory Motor Performance Program, Rehabilitation Institute of Chicago, Chicago, IL, USA.
authors.forename: Yupeng
authors.initials: Y
authors.lastname: Ren
authors.affiliation: Department of Physical Medicine & Rehabilitation, Northwestern University, Chicago, IL, USA; Department of Physical Therapy, Georgia State University, Atlanta, GA, USA.
authors.forename: Liang-Ching
authors.initials: LC
authors.lastname: Tsai
authors.affiliation: Sensory Motor Performance Program, Rehabilitation Institute of Chicago, Chicago, IL, USA; Department of Health Care Sciences, University of Texas Southwestern, Dallas, TX, USA.
authors.forename: Fan
authors.initials: F
authors.lastname: Gao
authors.affiliation: Sensory Motor Performance Program, Rehabilitation Institute of Chicago, Chicago, IL, USA; Department of Physical Medicine & Rehabilitation, Northwestern University, Chicago, IL, USA; Department of Orthopaedic Surgery, Northwestern University, Chicago, IL, USA; Department of Biomedical Engineering, Northwestern University, Evanston, IL, USA(h)Department of Orthopaedic Surgery, Northshore University HealthSystem, Evanston, IL, USA; Department of Orthopaedic Surgery, Northshore University HealthSystem, Evanston, IL, USA. Electronic address: l-zhang@northwestern.edu.
authors.forename: Li-Qun
authors.initials: LQ
authors.lastname: Zhang
mesh_terms: D000818:Animals; D008297:Male; D008853:Microscopy; D018485:Muscle Fibers, Skeletal / Q000502:physiology*; D017207:Rats, Sprague-Dawley; D012518:Sarcomeres / Q000502:physiology*
keywords: Force microscope; Muscle fiber; Sarcomere