Pitt HomeEngineering HomeContact Us

People Faculty

Michael S. Sacks

William Kepler Whiteford Professor, Department of Bioengineering

Email:
Phone: (412) 235-5146
Fax: (412) 235-5160
Office: Research: 100 Technology Drive, Room 250
Teaching: Room 742 Benedum Hall
Lab: Engineered Tissue Mechanics Laboratory

Education

Ph.D. (Biomedical Engineering), University of Texas Southwestern Medical Center at Dallas, 1992
M.S. Applied Mechanics, Michigan State University, 1983
B.S. Applied Mechanics, Michigan State University, 1981

Professional Interests

My overall research focus is quantification and modeling of the structure-mechanical properties of native and engineered soft tissues, with a focus on tissues of the cardiovascular and urological systems. In particular, my laboratory has focused on the mechanical behavior and function of the native aortic and mitral heart valves, including the developement of the first constitutive (stress-strain) models for these tissues using a structural approach. My laboratory is also active in the biomechanics of engineered tissues, and in particular understanding the in-vitro and in-vito remodeling processes from a functional biomechanical perspective. To acquire the necessary critical experimental data, my laboratory has developed several novel methods to quantify tissue structure and multi-axial mechanical testing techniques. By integrating the resulting experimental data obtained from both techniques, we have developed structural constitutive (stress-strain) models that directly integrate information on tissue composition and structure. These models avoid ambiguities in material characterization, offering insight into the function, structure, and mechanics of tissue components.

More recent work includes multi-scale studies of cell/tissue/organ mechanical interactions in heart valves. I am particularly interested in determing the local stress environment for heart valve interstitial cells. Next, we are currently utilizing an integrated experimental/multi-scale finite element approach to determine how hemodynamic loading on the valve translates to altered stress states on the valve interstitial cell function and, in-turn, changes in local extra-cellular structure/composition and valve function.

Specific applications include:

  • Structural constitutive (stress-strain) models for native and engineered heart valve tissues, and biologically derived biomaterials used in heart valve bioprostheses. This includes the first model of the native and bioprosthetic aortic heart valve.
  • Multi-scale experimental studies and finite element simulations that incorporate structural constitutive models for soft tissue that enable simulation of growth and estimation of cell/matrix stress fields.
  • Effects of long-term changes in heart valve structure/composition when subjected to altered stress states using valvular tissue from normal and left ventricular assist device (LVAD)-supported calfs. This unique study allows us study how otherwise normal valvular tissue responds to either increased or decreased dynamic stresses.
  • Measurement and computation of the dynamic heart valve tissue strains and stresses from in-vivo and in-vitro dynamic deformation data and in-vitro for the mitral valve.
  • Structure-strength relations and constitutive models of tissue engineered materials, including stem-cell seeded intestinal sub-mucosa and cell-seeded polymer biocomposites.
  • Development of first quasi-static and viscoelastic constitutive models for active and passive mechanical properties of the urinary bladder. These models are correlated to changes in tissue composition and structure in both the normal and post-spinal cord injured rat bladder.
  • Quantification and modeling of the mechanical properties of the normal and aneurysmal abdominal aorta.

In addition to the tissue and cell level work, I have established a research program in organ-level stress-analyses that utilize in-vitro and in-vivo imaging technologies. Specific applications include:

  • Development of a novel device to quantify heart valve leaflet motion and shape under physiologic flow conditions using a non-contacting structured light approach. This device is to be used for both native, chemically treated, and tissue engineered valve prostheses.
  • Development of novel surface fitting methods to quantify the complete shape and deformation of anatomic structures from spiral CT, MR, and material marker data.
  • Development of a thin-shell force-equilibrium model to compute the in-vivo wall tensions in abdominal aortic aneurysms and the urinary bladder directly from in-vivo images.

For more details, please click here to review Dr. Sacks' curriculum vitae (PDF Format).

Selected Publications

  • Sacks, M.S., Engelmayr, G.C., Hildebrand, D.K., and Mayer, J.E., Jr. (2005). Chapter 11 - Biomechanical considerations for tissue engineered heart valve bioreactors. An invited chapter for Bioreactors for Tissue Engineering, Julian Chadhuri and Mohamed Al Rubeai, Eds., Springer, pp. 235-267.
  • Wells, S., Sellaro, T., and Sacks, M. (2005). Cyclic loading response of bioprosthetic heart valves: Effects of fixation stress state on the collagen fiber architecture. Biomaterials, 26(15), 2611-2619.
  • Sutherland, F.W.H., Perry, T.E., Yu, Y., Sherwood, M.C., Rabkin, E., Masuda, Y., Garcia, G.A., McLelland, D.L., Engelmayr, G.C., Sacks, M.S., Schoen, F.J., and Mayer, J.E. (2005). From stem cells to viable autologous semilunar heart valve. Circulation, 111(21), 2783-2791.
  • Sun, W., Scott, M.J., and Sacks, M.S. (2005). Effects of boundary conditions on the planar biaxial mechanical properties of soft tissues. Journal of Biomechanical Engineering, 127(4), 709-715.
  • Sun, W., Scott, M.J., and Sacks, M.S. (2005). Finite element implementation of a generalized fung-elastic constitutive model for planar soft tissues. Biomechanics and Modeling in Mechanobiology, 4(2-3), 190-199.
  • Sun, W., Abad, A., and Sacks, M.S. (2005). Simulated bioprosthetic heart valve deformation under quasi-static loading. Journal of Biomechanical Engineering, 127(6), 905-914.
  • Nagatomi, J., Grashow, J.S., Toosi, K., and Sacks, M.S. (2005). Quantification of bladder smooth muscle orientation in normal and spinal cord injured rats. Annals of Biomedical Engineering, 33(8), 1078-1089.
  • Nagatomi J., DeMiguel, K., Torimoto, Chancellor, M.B., Getzengerg, R.H., and Sacks, M.S. (2005). Early molecular-level changes in rat bladder wall tissue following spinal cord injury. Biochemical and Biophysical Research Communications, 334(4), 1159-1164.
  • Mirnajafi, A., Raymer, J.M., McClure, L.R., and Sacks, M.S. (2005). Flexural rigidity of the aortic valve leaflet in the commissural region. Journal of Biomechanics, 14, December (e-publication).
  • Mirnajafi, A., Raymer, J., Scott, M.J., and Sacks, M.S. (2005). The effects of collagen fiber orientation on the flexural properties of pericardial heterograft biomaterials. Biomaterials, 26(7), 795-804.
  • Lu, S.H., Sacks, M.S., Chung, S.Y., Gloeckner, D.C., Pruchnic, R., Huard, J., deGroat, W.C., and Chancellor, M.B. (2005). Biaxial mechanical properties of muscle-derived cell seeded small intestitinal submucosa for bladder wall reconstruction. Biomaterials, 26, 443-449.
  • Liao, J., Yang, L., Grashow, J., Sacks, M.S. (2005). Molecular orientation of collagen in intact planar connective tissue under biaxial stretch. ACTA BIOMATERIALIA, 1(1), 45-54.
  • He, Z., Ritchie, J., Grashow, J.S., Sacks, M.S., and Yoganathan, A.P. (2005). In-vitro dynamic strain behavior of the miral valve posterior leaflet. Journal of Biomechanical Engineering, 127(3), 504-511.
  • Guan, J., Fujimoto, K.L., Sacks, M.S., and Wagner, W.R. (2005). Preparation and characterization of highly porous, biodegradable polyurethane scaffolds for soft tissue applications. Biomaterials, 26, 3961-3971.
  • Engelmayr, G.C., Rabkin, E., Sutherland, F.W.H., Schoen, F.J., Mayer, Jr., J.E., and Sacks M.S. (2005). The independent role of cyclic flexure in the early in vitro development of engineered heart valve tissue. Biomaterials, 26(2), 175-187.
  • Connolly, J.M., Alferiev, I., Clark, J.N., Eidelman, N., Sacks, M.S., Palmatory, E., Lu, Z., Kronsteiner, A., DeFelice, S., Xu, J., Ohri, R., Narula, N., Vyavahare, N., and Levy, R.J. (2005). Triglycidyl amine crosslinking of porcine aortic valve cusps or bovine pericardium results in improved biocompatibility, biomechanics, and calcification resistance: Chemical and biological mechanisms. American Journal of Pathology, 166(1), 1-13.
  • Cannon, T.W., Sweeney, D.D., Conway, D.A., Kamo, I., Yoshimura, N., Sacks, M.S., and Chancellor, M.B. (2005). A tissue-engineered suburethral sling in an animal model of stress urinary incontinence. BJU International, 96(4), 664-669.
  • Vande Geest, J.P., Sacks, M., & Vorp, D.A. (2004). Age-related differences in the biaxial biomechanical behavior of human abdominal aorta. Journal of Biomechanical Engineering, 126, 815-822.
  • Sun, W., Sacks, M.S., Fulchiero, G., Lovekamp, J., Vyavahare, N., & Scott, M.J. (2004). Response of heterograft heart valve biomaterials to moderate cyclic loading. Journal of Biomedical Materials Research, 69A, 658-669.
  • Sun, W., Sacks, M.S., Fulchiero, G., Lovekamp, J., Vyavahare, N., & Scott, M.J. (2004). Response of heterograft heart valve biomaterials to moderate cyclic loading. Journal of Biomedical Materials Research, 69A, 658-669.
  • Nagatomi, J., Gloeckner, D.C., Chancellor, M.B., deGroat, W.C., & Sacks, M.S. (2004). Changes in the biaxial viscoelastic response of the urinary bladder following spinal cord injury. Annals of Biomedical Engineering, 32, 1409-1419.
  • Hildebrand, D.K., Wu, J., Mayer, J.E., & Sacks, M.S. (2004). Design and hydrodynamic evaluation of a novel pulsatile bioreactor for biologically active heart valves. Annals of Biomedical Engineering, 32(8), 1039-1049.
  • Guan, J., Sacks, M.S., Beckman, E.J., & Wagner, W.R. (2004). Biodegradable poly(ester-urethane)urea elastomers based on poly(ether ester) triblock copolymers and putrescine: Synthesis, characterization, and cytocompatibility. Biomaterials, 25(1), 85-96.
  • Sacks, M.S. (2004). Small angle light scattering methods for soft tissue connective tissue structural analysis. In: G Wnek and G Bowlin (Eds) Encyclopedia for Biomaterials and Biomedical Engineering, (p. 1371-1384), New York, Marcel Dekker.
  • Sacks, M.S. (2003). Biomechanics of native and engineered heart valve tissues. Functional Tissue Engineering (Chap. 18, pp. 243-257). New York, NY: Springer-Verlag.
  • Sacks, M.S., & Sun, W. (2003). Multiaxial mechanical behavior of biological materials. Annual Reviews of Biomedical Engineering (Vol. 5, pp. 251-284). Palo Alto, CA.
  • Sun, W., Sacks, M.S., Sellaro, T.L., Slaughter, W.S., & Scott, M. (2003). Biaxial mechanical response of chemically treated bovine pericardium to high in-plane shear. Journal of Biomechanics, 125(3), 372-380.
  • Sacks, M.S. (2003). Incorporation of SALS-derived fiber orientation data into a structural constitutive model for planar collagenous tissues. Journal of Biomechanical Engineering, 25, 280-287.
  • Perry, T.E., Kaushal, S., Sutherland, F.W.H., Guleserian, K.J., Bischoff, J., Sacks, M.S., & Mayer, J.E. (2003). Bone marrow: A cell source for tissue engineered valves. Annals of Thoracic Surgery, 75(3), 761-767.
  • Lu, S.H., Cannon, T.W., Chermanski, C., Pruchnic, R., Somogy, G., Sacks, M.S., DeGroat, W.C., Huard, J., & Chancellor, M.B. (2003). Muscle-derived stem cells seeded acellular scaffolds develop calcium dependent contractile activity that is modulated by nicotinic receptors. Urology, 61(6), 1285-1291.
  • He, Z., Sacks, M.S., Baijens, L., Wanant, S., Shah, P., & Yoganathan, A.P. (2003). Effects of papillary muscle position on the in-vitro dynamic strain on the porcine mitral valve. Journal of Heart Valve Disease, 12(4), 488-494.
  • Engelmayr, G.C., Hildebrand, D.K., Sutherland, F.W.H., Mayer, Jr., J.E., & Sacks, M.S. (2003). A novel bioreactor for the dynamic flexural stimulation of tissue engineered heart valve biomaterials. Biomaterials, 24(14), 2523-2532.
  • Debski, R.E., Moore, S.M., Mercer, J.L., Sacks, M.S., & McMahon, P.J. (2003). The collagen fibers of the anteroinferior capsulolabrum have multi-axial orientation to resist shoulder dislocation. Journal of Shoulder and Elbow Surgery, 12(3), 247-252.
  • Criscione, J.C., Sacks, M.S., & Hunter, W.C. (2003). Experimentally tractable, pseudo-elastic constitutive law for biomembranes: II. Application. Journal of Biomechanical Engineering, 125(1), 100-105.
  • Criscione, J.C., Sacks, M.S., & Hunter, W.C. (2003). Experimentally tractable, pseudo-elastic constitutive law for biomembranes: I. Theory. Journal of Biomechanical Engineering, 125(1), 94-99.
  • Alferiev, I., Stachelek, S.J., Lu, Z., Fu, A., Sellaro, T.L., Connolly, J.M., Bianco, R.W., Sacks, M.S., & Levy, R.J. (2003). Prevention of polyurethane valve cusp calcification with covalently attached biophosphonate diethylamino moieties. Journal of Biomedical Materials Research, 66A(2), 385-395.
  • M.S. Sacks and F.J. Schoen, “Mechanical damage to collagen independent of calcification limits bioprosthetic heart valve durability,” Journal of Biomedical Materials Research, vol. 62, pp. 359-371, 2002.
  • J.Guan, M.S. Sacks, E.J. Beckman, W.R. Wagner, “Synthesis, characterization, and cytocompatability of elastomeric, biodegradable poly(ester-urethane)ureas based on poly(caprolactone) and putrescine,” Journal of Biomedical Materials Research, vol. 61, pp. 493-503, 2002.
  • D. C. Gloeckner, M.S. Sacks, M.O. Fraser, G.S. Somogyi, W.C. de Groat, M.B. Chancellor,” Passive Biaxial mechanical properties of the rat urinary bladder wall after spinal cord injury,” J. Urology, vol. 167, pp. 2247-2252, 2002.
  • S.M. Wells and M.S. Sacks, “Effects of fixation pressure on the biaxial mechanical behavior of porcine bioprosthetic heart valves with long-term cyclic loading,” Biomaterials, vol. 23, no. 11, pp. 2389-2399, 2002.
  • M.S. Sacks, “The biomechanical effects of fatigue on the porcine bioprosthetic heart valve,” Journal of Long-term Effects of Medical Implants, Vol. 11 (3&4),pp. 231-247, 2001.
  • A.K.S. Iyengar, H. Sugimoto, D.B. Smith, and M.S. Sacks, “Dynamic in-vitro quantifcation of bioprosthetic heart valve leaflet motion using structured light projection,” Annals of Biomedical Engineering , vol. 29, pp. 963-973, 2001.
  • M.S. Sacks, “Biaxial mechanical evaluation of planar biological materials,” Journal of Elasticity, vol. 61, pp. 199-246, 2000 (invited by Dr. Steven Cowin as part of a special issue on biomechanics).
  • M.S. Sacks, “A structural constitutive model for chemically treated planar tissues under biaxial loading,” Computional Mechanics, vol. 26 (3), pp. 243-249, 2000.
  • D.B. Smith, M.S. Sacks, D.A. Vorp, and M. Thornton, "Surface geometric analysis of anatomic structures using biquintic finite element interpolation," Annals of Biomedical Engineering, vol. 28(6), pp 598-611, 2000.
  • D. C. Gloeckner, M.S. Sacks, K.L. Billiar, N. Bachrach, "Mechanical Evaluation and Design of a Multi-layered Collagenous Repair Biomaterial," Journal of Biomedical Materials Research, vol. 52(2), pp.365-373, 2000.
  • K.L. Billiar and M.S. Sacks, “Biaxial mechanical properties of the fresh and glutaraldehyde treated porcine aortic valve: Part II - A structurally guided constitutive model,” Journal of Biomechanical Engineering, vol. 122 (4), pp. 327-335, 2000.
  • K.L. Billiar and M.S. Sacks, “Biaxial mechanical properties of the fresh and glutaraldehyde treated porcine aortic valve: Part I - Experimental results,” Journal of Biomechanical Engineering, vol. 122, pp. 23-30, 2000.

You are using a browser that does not support current Web standards. Although this site is viewable in all browsers, it will look much better in a browser that supports Web standards.