Our lab works to understand how cells interact with the extracellular matrix (ECM) and how these interactions change in diseased states. The ECM largely consists of a complex network of interwoven protein fibers that are assembled into a 3D nanostructured architecture. In addition to providing structural support, the ECM provides biophysical signals that direct cell shape, differentiation, migration, proliferation, as well as new tissue synthesis by presenting a complex milieu of topographic, mechanical and biochemical cues. To better understand these interactions our lab develops biophotonics tools based on nonlinear optical methods. Our primary imaging tool is Second Harmonic Generation (SHG) microscopy for quantifying changes in the fibril/fiber assembly of collagen in cancer and connective tissue disorders. We also utilize multiphoton excited photochemistry to fabricate 3D nano/microstructured models of the ECM for studying signaling pathways in cancer as well as for tissue engineering applications. We are currently focusing on:
1. Imaging collagen changes in ovarian and breast cancer: Alterations to the ECM composition and structure are thought to be critical for tumor initiation and progression for several epithelial carcinomas, including those of the ovary and breast. Thus selective imaging of the collagen assembly in the stroma may provide an earlier diagnostic optical signature. As these cancers develop there is a dynamic interaction between the epithelial neoplastic cells and the ECM. For example, the expression of matrix metalloproteinases (MMPs) has been shown to be increased in tumor cells and functions to remodel both the basal lamina and the stroma. Concurrently, changes in the stromal compartment of a tumor can act as an input to elicit a cascade of further changes involving fibroblasts and tumor cells and generating more aggressive tumor cells. Our lab develops SHG microscopy tools to quantitatively assess these alterations in the stroma where we correlate the optical signatures with structural changes in the fibrillar assembly between normal and diseased tissues. This physical approach to quantifying stromal changes provides objective measurements that may be used to understand disease progression. Ultimately these imaging tools may be developed as intrinsic biomarkers for use in clinical applications.
2. Studying invasion/metastasis in human ovarian cancer via nano/microfabricated models of the ECM: Ovarian cancer continues to be diagnosed at stages too late to treat efficaciously because of the lack of effective screening technologies. Our project on SHG imaging may lead to a diagnostic tool, however we first need to gain significantly more insight into tissue structural changes preceding and during carcinogenesis before clinical applications can become a reality. To investigate how remodeling enables invasion and metastasis in vivo we use multiphoton excited (MPE) photochemistry to fabricate biomimetic in vitro models of the ovarian ECM representing the crosslinked basal lamina and stroma. The nano/microstructured models simulate the crosslinked fibrillar structure of the native ECM and allow the testing of pathway activity not immediately possible in human subjects or even animal models. We evaluate how MMPs affect cell-ECM interactions in carcinogenesis by performing quantitative comparisons between “normal” immortalized epithelial cells as well as ovarian cancer cell lines of varying invasiveness. Specifically we determine cell migration speed, adhesion strength, and invasiveness with protease modulation through stimulus with soluble growth factors and cytokines and blocking by inhibitors and antibodies. Our approach evaluates remodeling signatures under controlled conditions using multiphoton excited fluorescence and SHG imaging of the invasion and the remodeling dynamics.
3. Studying cell-matrix interactions for tissue engineering applications via nano/microfabricated models of the ECM: Tissue engineering has vast potential to improve human health by repair and maintenance of existing tissue or generation of replacement of tissues and organs. Crucial to the success of creating implantable devices is the development of fabrication tools that control the nano/microscale architecture of the scaffold that governs the cell binding dynamics. Thus to stimulate tissue growth or repair fabrication tools must be able to position cells and active biomolecules with micron and submicron precision. A major limitation in extending such studies to the clinic has been an incomplete understanding of the underlying cell-ECM interactions that govern cell adhesion which will ultimately affect downstream functions. Our approach to this problem utilizes multiphoton excited photochemistry to create 3D scaffolds directly from crosslinked proteins. This process affords intrinsic 3D spatial control and can create minimum features sizes of submicron dimension, and can thus mimic both the composition and topography of the native ECM structure. Beginning with bio-inspired ECM designs we seek to achieve improved functionality through local control of composition and concentration, and gradients thereof. We further use this approach to study the factors that govern stem cell differentiation and fate.