Our Research
Dennis Laboratory
Thomas J. Kean, PhD, Hisashi Mera, MD, James E. Dennis, PhD, Adam Whitney, PhD candidate (not pictured)
Tissue engineering is a multidisciplinary field whereby cells are cultured in vitro to provide a living tissue repair. We are looking at several aspects of this research both to produce actual tissue (primarily cartilage and bone) and to promote the regeneration of tissue through systemic administration of stem cells. The Dennis Lab has several tissue engineering goals:
Total Joint Resurfacing: Using a technology developed in this laboratory to produce large sheets of cartilage (6.5 x 7.5 cm in area), this project is aimed at developing a method to completely replace entire surfaces of joints. Currently the laboratory is developing and testing a new bioreactor for producing cartilage of greater thickness, while working on biocompatible glues to adhere the engineered cartilage to the underlying bone or to combine the chondrocytes with mesenchymal stem cells to provide a bony interface. This program is currently funded as a sub-project in a Program Project Grant from the NIH (National Institute of Arthritis, Musculoskeletal and Skin Diseases), in collaboration with researchers from Case Western Reserve University in Cleveland, Ohio.
Engineering of a Neo-Trachea: Using the cartilage sheet technology, we are developing methods to engineer autologous trachea-like tissue that is suitable for use in repairing long segmental defects. This project is funded through an R01 grant from the National Institute of Dental and Craniofacial Research.
The etiology of laryngotracheal and tracheal stenoses is multifaceted, however, long-term intubation or tracheotomy are the most common causes. The traditional procedure for laryngotracheal stenosis has been laryngotracheal reconstruction (LTR) with anterior and/ or posterior cartilage grafting, which has proven to be very successful. We are currently investigating tissue engineered cartilage as an alternative to native cartilage. Various tissue engineering strategies, such as different scaffolds, growth factors and compression culture are researched to fabricate suitable cartilage grafts for laryngotracheal reconstruction.
Development of a Targeted Stem Cell: One of the major hurdles for applying adult stem cells to tissue repair is the efficient delivery of those cells to the tissue of interest. To address this issue, we are developing cellular “paints” that attach themselves to cell membranes and have the capacity to bind either to the matrix components of the tissue needing repair, or to bind to the specific endothelium of the tissue of interest. Our current focus is to define the interactions of “painted” cells on defined molecular substrates, in vitro, and to then apply them for in vivo targeting. The use of targeted cells for the repair of cartilage was funded through the National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS; http://www.niams.nih.gov/), and the targeting of cells to cardiac tissue was funded by the Department of Defense through a grant awarded to Cell Targeting, LLC (now acquired by BioTime Inc.).
The body has an amazing ability to repair and, in early life, regenerate. Much of this is thought to be performed by stem cells. However, in severe injury or disease, these repair mechanisms are insufficient. The goal of this research project is develop a targeted cell so that the cell adheres to sites of injury and repairs the damaged tissue. Two methods of targeting the cells are being investigated - Antibody Directed Cell Therapy (ADCT) and Peptide Directed Cell Therapy (PDCT). In ADCT cells are first coated with palmitated protein G (PPG), a modified recombinant protein that binds to the Fc region of antibodies. Then antibodies are used to coat the cells giving a targeted cell.
In PDCT peptides are derived by phage display technology. Phage are genetically engineered to express random peptides on their surface; for a seven amino acid peptide this produces a theoretical diversity of 1.28 x 10^9 different phage. These phage are then selected against the tissue of interest, reducing the phage pool. The reduced phage pool is then amplified and reselected against the tissue of interest. This work has been done in collaboration with Dr. Erkki Rouslahti who had previously developed phage which homed to injured tissue and neovasculature.
