Biomechanical Regulation of Gene Expression in Knee Ligaments

Ligaments maintain joint stability by resisting tensile loads and preserving compressive loads between bones. During normal function, ligaments are subjected to mechanical loads which consequently induce the deformation in the ligament tissues. Two knee ligaments of clinical interest are the anterior cruciate ligament (ACL), which fails to heal after injury, and the medial collateral ligament (MCL), which exhibits a healing response. Characterizing the biomechanical regulation of cellular behavior relevant to healing and remodeling processes would contribute to our understanding of mechanically induced changes in ligaments. This dissertation investigates the role of mechanical loading on the expression of collagens in ligament fibroblasts through the use of an in vitro cell culture system and an ex vivo organ culture preparation

Expression of types I and HI collagens were determined for ACL and MCL fibroblast monolayers subjected to cyclic mechanical loads. ACL fibroblasts responded with an upregulation of type I collagen expression while MCL fibroblasts exhibited a striking increase in type in collagen expression. In addition, type III collagen expression patterns in ACL cells depended on the maximum strain. These results were consistent with observations in tissue healing and remodeling in vivo, and demonstrate an additional intrinsic difference that exists between ACL and MCL fibroblasts.

To preserve the anatomical cellular loading environment of ligament fibroblasts, an organ culture preparation novel for the application of mechanical loads to ligaments was designed. In particular, the ACL was chosen for further analysis. A tissue harvest procedure was developed for rat ACLs and shown to be feasible by cell viability assessment. Application of 5 N incremental loads induced ACL surface strains on the order of those previously measured in human ACLs. After initiation of incremental loading, expression of type I collagen increased significantly within 1 hour, but then decreased significantly to 46% of control values after 2 hours.

These studies contribute to our understanding of cellular responses to mechanical loading. Development of an organ culture system for the study of mechanically-induced responses in ligaments provides impetus for further research in ligament healing and remodeling as well as in relevant cellular and molecular processes.

Year	Entry
1992	Butler DL, Guan Y, Kay MD, Cummings JF, Feder SM, Levy MS. Location-dependent variations in the material properties of the anterior cruciate ligament. J Biomech. May 1992;25(5):511-518.
1972	Fung Y-CB. Stress-strain-history relations of soft tissues in simple elongation. In: Fung YC, Perrone N, Anliker M, eds. Biomechanics: Its Foundations and Objectives. Symposium on Biomechanics, its Foundations and Objectives; July 29-31, 1970. Englewood Cliff, NJ: Inc., Prentice-Hall International; 1972:181-208.
1996	Rawlinson SCF, Pitsillides AA, Lanyon LE. Involvement of different ion channels in osteoblasts' and osteocytes' early responses to mechanical strain. Bone. December 1996;19(6):609-614.
1892	Wolff J. Das Gesetz der Transformation der Knochen. Berlin: Hirschwald; 1892.
1983	Woo SL-Y, Gomez MA, Seguchi Y, Endo CM, Akeson WH. Measurement of mechanical properties of ligament substance from a bone-ligament-bone preparation. J Orthop Res. 1983;1(1):22-29.
1987	Woo SL-Y, Hollis JM, Roux RD, Gomez MA, Inoue M, Kleiner JB, Akeson WH. Effects of knee flexion on the structural properties of the rabbit femur-anterior cruciate ligament-tibia complex (FATC). J Biomech. 1987;20(6):557-563.
1996	Blankevoort L, Huiskes R. Validation of a three-dimensional model of the knee. J Biomech. July 1996;29(7):955-961.
1999	Li G, Rudy TW, Sakane M, Kanamori A, Ma CB, Woo SL-Y. The importance of quadriceps and hamstring muscle loading on knee kinematics and in-situ forces in the ACL. J Biomech. April 1999;32(4):395-400.
1998	Quapp KM, Weiss JA. Material characterization of human medial collateral ligament. J Biomech Eng. December 1998;120(6):757-763.
1999	Pioletti DP, Rakotomanana LR, Leyvraz P-F. Strain rate effect on the mechanical behavior of the anterior cruciate ligament–bone complex. Med Eng Phys. March 1999;21(2):95-100.
1975	Girgis FG, Marshall JL, Al Monajem ARS. The cruciate ligaments of the knee joint: anatomical, functional and experimental analysis. Clin Orthop Relat Res. January–February 1975;106:216-231.
1983	Frank C, Woo SL-Y, Amiel D, Harwood F, Gomez M, Akeson W. Medial collateral ligament healing: a multidisciplinary assessment in rabbits. Am J Sports Med. 1983;11(6):379-389.
1996	Rudy TW, Livesay GA, Woo SL-Y, Fu FH. A combined robotic/universal force sensor approach to determine in situ forces of knee ligaments. J Biomech. October 1996;29(10):1357-1360.
1991	Weiss JA, Woo SL-Y, Ohland KJ, Horibe S, Newton PO. Evaluation of a new injury model to study medial collateral ligament healing: primary repair versus nonoperative treatment. J Orthop Res. July 1991;9(4):516-528.
1991	Woo SL-Y, Hollis JM, Adams DJ, Lyon RM, Takai S. Tensile properties of the human femur-anterior cruciate ligament-tibia complex: the effects of specimen age and orientation. Am J Sports Med. 1991;19(3):217-225.
1983	Arms S, Boyle J, Johnson R, Pope M. Strain measurement in the medial collateral ligament of the human knee: an autopsy study. J Biomech. 1983;16(7):491-496.
1996	Hull ML, Berns GS, Varmat H, Patterson HA. Strain in the medial collateral ligament of the human knee under single and combined loads. J Biomech. February 1996;29(2):199-206.
1997	Sah RL, Yang AS, Chen AC, Hant JJ, Halili RB, Yoshioka M, Amiel D, Coutts RD. Physical properties of rabbit articular cartilage after transection of the anterior cruciate ligament. J Orthop Res. March 1997;15(2):197-203.
1974	Noyes FR, DeLucas JL, Torvik PJ. Biomechanics of anterior cruciate ligament failure: an analysis of strain-rate sensitivity and mechanisms of failure in primates. J Bone Joint Surg. March 1974;56A(2):236-253.
1998	Herzog W, Diet S, Suter E, Mayzus P, Leonard TR, Müller C, Wu JZ, Epstein M. Material and functional properties of articular cartilage and patellofemoral contact mechanics in an experimental model of osteoarthritis. J Biomech. December 1998;31(12):1137-1145.
1982	Woo SL-Y, Gomez MA, Woo Y-K, Akeson WH. Mechanical properties of tendons and ligaments, II: the relationships of immobilization and exercise on tissue remodeling. Biorheology. 1982;19(3):397-408.

Year

Entry

1992

Butler DL, Guan Y, Kay MD, Cummings JF, Feder SM, Levy MS. Location-dependent variations in the material properties of the anterior cruciate ligament. J Biomech. May 1992;25(5):511-518.

1972

Fung Y-CB. Stress-strain-history relations of soft tissues in simple elongation. In: Fung YC, Perrone N, Anliker M, eds. Biomechanics: Its Foundations and Objectives. Symposium on Biomechanics, its Foundations and Objectives; July 29-31, 1970. Englewood Cliff, NJ: Inc., Prentice-Hall International; 1972:181-208.

1996

Rawlinson SCF, Pitsillides AA, Lanyon LE. Involvement of different ion channels in osteoblasts' and osteocytes' early responses to mechanical strain. Bone. December 1996;19(6):609-614.

1892

Wolff J. Das Gesetz der Transformation der Knochen. Berlin: Hirschwald; 1892.

1983

Woo SL-Y, Gomez MA, Seguchi Y, Endo CM, Akeson WH. Measurement of mechanical properties of ligament substance from a bone-ligament-bone preparation. J Orthop Res. 1983;1(1):22-29.