Petroll Lab

Cell Mechanics & Corneal Wound Healing

Petroll Lab applies engineering approaches and design principles to the investigation of fundamental clinical and biological problems in ophthalmology, while providing training to graduate students, medical students, and post-docs.

Research

The main focus of Petroll Lab’s research is cell mechanics and tissue engineering, in which multidimensional time-lapse imaging is used to investigate how the mechanical behavior of corneal fibroblasts is regulated by both biochemical and biophysical stimuli. He also has a longstanding interest in the development and application of in vivo confocal microscopy and in situ multiphoton imaging, which allow quantitative 3-D assessment of cell differentiation and extracellular matrix organization during corneal wound healing in response to clinical procedures such as refractive surgery or UV cross-linking.

applied research We develop and apply in vivo confocal microscopy and in situ multiphoton imaging techniques to assess the cellular responses to corneal injury, disease and refractive surgical procedures.

    Overview

    The organization of extracellular matrices by cells through the exertion of mechanical forces drives fundamental processes such as developmental morphogenesis, wound healing, and the organization of bioengineered tissues. Historically, our ability to investigate cell mechanical behavior has been limited by the technical challenges associated with measuring the sub-cellular origins of cellular force generation and local matrix patterning in a 3-D environment. Thus, our understanding of these fundamental processes is limited, especially in ocular tissues. Over the last several years, our research team has addressed these challenges through the development of new experimental models, use of emerging imaging technologies, and the application of quantitative analysis techniques. 

    Experimental Models

    Our in vitro approaches include: 1) models for assessing how specific growth factors expressed following injury or surgery alter the mechanical differentiation of quiescent corneal keratocytes within 3-D collagen matrices, 2) novel approaches for assessing the response of fibroblasts to dynamic changes in ECM mechanical properties (as might be observed during development or wound healing), 3) 3-D constructs for assessing the mechanical interplay between fibroblast migration, sub-cellular force generation, and ECM patterning, and 4) engineered substrates that allow investigation of the impact of ECM protein composition, topography, and elasticity on cell differentiation and mechanical behavior.

    Together, these experimental models are providing unique insights into the underlying biochemical and biomechanical signaling mechanisms controlling corneal fibroblast migration, contraction, and matrix reorganization. This is fundamental information which can not be obtained using standard 2-D culture models, and may eventually lead to improved strategies for modulating cell mechanical activity during wound healing, and for designing artificial matrices and directing cell behavior during corneal tissue engineering. 

    The cornea is an optically clear tissue that forms the front surface of the eye, and accounts for nearly two-thirds of its refractive power. The corneal stroma, which makes up 90% of corneal thickness, is a highly organized structure consisting of collagen lamellae with specific packing and spacing that is critical to maintenance of corneal transparency. Corneal stromal cells (keratocytes) reside between the collagen lamellae, and are responsible for secreting extracellular matrix (ECM) components required to maintain normal corneal structure and function (i.e. transparency). Because it is exposed, the cornea is susceptible to infection, physical and chemical injuries; it is also the target of many vision correction procedures.

    Stromal keratocytes play a central role in mediating the corneal response to lacerating injury, chemical injuries or surgical procedures. During wound healing, quiescent corneal keratocytes surrounding the area of injury generally become activated, and transform into a fibroblastic repair phenotype. In certain wound types, fibroblasts further differentiate into myofibroblasts, which generate stronger forces and synthesize a disorganized fibrotic ECM. Cellular force generation and fibrosis can alter corneal shape and/or reduce corneal transparency, thereby reducing visual acuity.

    In addition to fibrosis which develops on top of the wound bed, most vision correction procedures induce keratocyte death beneath the laser-treated area.  Stromal cell death can also be induced by toxic injury, as well as UV cross-linking (CXL) of the cornea in keratoconus patients. Ideally, repopulation following these insults should occur via intra-stromal migration of keratocytes from the surrounding stromal tissue, without generation of strong contractile forces that could disrupt the collagen architecture and lead to vision loss.

    Our lab develops and applies high resolution imaging and image processing approaches to better understand and potentially modulate these healing responses. Specifically, we use in vivo confocal microscopy to assess stromal keratocyte differentation, patterning and activation in response corneal injury, surgery, or disease. We also use 3-D confocal and multiphoton imaging of corneal tissue ex vivo to assess the expression and localization of specific proteins associated with wound healing (using fluorescent labeling) as well as changes in extracellular matrix organization (using second harmonic generation imaging).1,2

    References

    1. Petroll WM, Kivanany PB, Hagenasr D, Graham EK. Corneal Fibroblast Migration Patterns During Intrastromal Wound Healing Correlate With ECM Structure and Alignment. Invest Ophthalmol Vis Sci. 2015 Nov;56(12):7352-61.

    2. Kivanany PB, Grose KC, Tippani M, Su S, Petroll WM. Assessment of Corneal Stromal Remodeling and Regeneration after Photorefractive Keratectomy. Sci Rep. 2018 Aug 22;8(1):12580. 

    Meet the Principal Investigator

    W. Matthew Petroll, Ph.D.

    Dr. Petroll received his B.S. degree in Biomedical Engineering from Duke University in 1984, and his Ph.D. in Biomedical Engineering from the University of Virginia in 1989. After two years at Georgetown University in the lab of Drs. James Jester and Dwight Cavanagh, he joined the faculty at UT Southwestern in 1991. He was promoted to professor in 2005, and became Chair of the Graduate Program in Biomedical Engineering in 2012.

    Dr. Petroll’s laboratory applies engineering approaches and design principles to the investigation of fundamental clinical and biological problems in ophthalmology, while providing training to graduate students, medical students, and post-docs. The main focus of Dr. Petroll’s research is cell mechanics and tissue engineering, in which multidimensional time-lapse imaging is used to investigate how the mechanical behavior of corneal fibroblasts is regulated by both biochemical and biophysical stimuli. He also has a longstanding interest in the development and application of in vivo confocal microscopy, which allows quantitative 3-D imaging of the cornea and has been used in numerous research and clinical studies on corneal wound healing, toxicity, development and infection.

    Featured Publications

    1. Petroll WM, Varner VD, Schmidtke DW. Keratocyte Mechanobiology. Exp Eye Res. 2020 Nov;200:108228. 

    2. Kivanany PB, Grose KC, Tippani M, Su S, Petroll WM. Assessment of Corneal Stromal Remodeling and Regeneration after Photorefractive Keratectomy. Sci Rep. 2018 Aug 22;8(1):12580. 

    3. Miron-Mendoza M, Graham E, Manohar S, Petroll WM. Fibroblast-fibronectin patterning and network formation in 3D fibrin matrices. Matrix Biol. 2017 Dec;64:69-80. 

    4. Petroll WM, Kivanany PB, Hagenasr D, Graham EK. Corneal Fibroblast Migration Patterns During Intrastromal Wound Healing Correlate With ECM Structure and Alignment. Invest Ophthalmol Vis Sci. 2015 Nov;56(12):7352-61. 

    5. Petroll WM, Miron-Mendoza M. Mechanical interactions and crosstalk between corneal keratocytes and the extracellular matrix. Exp Eye Res. 2015 Apr;133:49-57.

    6. Miron-Mendoza M, Koppaka V, Zhou C, Petroll WM. Techniques for assessing 3-D cell-matrix mechanical interactions in vitro and in vivo. Exp Cell Res. 2013 Oct 1;319(16):2470-80.

    7. Lakshman N, Petroll WM. Growth factor regulation of corneal keratocyte mechanical phenotypes in 3-D collagen matrices. Invest Ophthalmol Vis Sci. 2012 Mar;53(3):1077-86.

    8. Grinnell F, Petroll WM. Cell motility and mechanics in three-dimensional collagen matrices. Annu Rev Cell Dev Biol. 2010;26:335-61.

    Full Bibliography

    Contact Petroll Lab

    W. Matthew Petroll, Ph.D. 
    Professor of Ophthalmology Vice Chair, Research
    Chair, Biomedical Engineering Graduate Program
    Email

    Mailing Address
    Department of Ophthalmology
    UT Southwestern Medical Center
    5323 Harry Hines Blvd.
    Dallas, TX 75390-9057

     

    Join Our Lab

    Petroll Lab is always interested in hearing from students and postdoctoral candidates who are interested in joining our lab. Please contact us for more information.