Cellular and Biosurface
Engineering Laboratory
P.I.: Andrés J.
García
Petit Institute for Bioengineering and Bioscience
Georgia Institute of Technology
Our research activities
focus on biomolecular, cellular, and tissue engineering strategies to
analyze/manipulate cell function (adhesion, proliferation, differentiation) for
biotechnological, biomaterial and regenerative medicine applications. These integrated strategies provide
fundamental insights into mechanisms regulating cell-material interactions and
constitute novel bioinspired approaches to the engineering of bioactive
materials and hybrid tissues.
Research Activities
Thrust 1:
Regulation of Cell Adhesion Strengthening
Thrust 2:
Bioadhesive Interfaces to Direct Cell Function and Host Responses
Thrust 3:
Genetically Engineered Cells/Scaffolds for Bone Tissue Engineering
Thrust 1: Regulation of Cell Adhesion Strengthening
Cell adhesion to extracellular matrices is central
to the organization, maintenance, and repair of numerous tissues. Cell-matrix adhesive interactions provide
tissue structure and generate anchorage forces that mediate cell spreading and
migration, neurite extension, muscle cell
contraction, and cytokinesis. Moreover, cell adhesion triggers signals
regulating the survival, cell cycle progression, and expression of differentiated
phenotypes in multiple cell systems. Abnormalities
in adhesive interactions are often associated with pathological states,
including blood clotting and wound healing defects as well as malignant tumor
formation. Adhesion to extracellular
matrix components, such as fibronectin (FN) and laminin, is primarily mediated
by integrin receptors. Integrin-mediated adhesion is a highly
regulated process involving receptor activation and mechanical coupling to
extracellular ligands. Bound receptors
rapidly associate with the actin cytoskeleton and cluster together to form focal adhesions, discrete supramolecular complexes
that contain structural proteins, such as vinculin and talin, and signaling
molecules, including FAK and Src.
We have integrated a hydrodynamic adhesion assay, micro/nanopatterning
techniques, and molecular/cell approaches
to analyze adhesion strengthening mechanisms.
This research focuses on (i) structure-function
analyses of integrin clustering and focal adhesion assembly, and (ii) the
functional role of adhesive structural and signaling components on adhesion
strengthening. This work provides a
rigorous framework for the analysis of adhesive mechanisms and functional
studies of normal and pathological processes.
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Thrust 2: Bioadhesive Interfaces to Direct Cell Function
and Host Responses
Cell adhesion to adsorbed proteins
or adhesive sequences engineered on biomaterial surfaces is crucial to cellular
and host responses to implanted devices, biological integration of biomaterials
and tissue-engineered constructs, and the performance of cell-based arrays and
sensors as well as biotechnological cell culture supports. Therefore, the development of biointerfaces that elicit specific cell adhesive responses
is central to numerous biomedical and biotechnological applications.
We are engineering bioactive interfaces, consisting of synthetic and
biological elements, to control adhesive interactions in order to direct cell
function. Our efforts concentrate on
engineering integrin binding specificity and focal adhesion assembly to regulate adhesive signaling
in order to regulate higher order cell functions, such as proliferation and
differentiation. Biomolecular strategies
pursued in this thrust include the engineering of interfaces presenting (i) adhesive ligands that mimic the secondary/tertiary
structure of native proteins to convey integrin specificity and/or exhibit
novel functionality, and (ii) controlled micro/nano-patterned
adhesive domains. This research spans
the biomolecular design of the interface, in vitro analyses of cell adhesion
and function, and implantation studies to evaluate the efficacy of these
innovative materials. These surface
engineering strategies provide a basis for the rational design of robust
biospecific interfaces that tailor adhesive interactions and elicit specific
cellular responses for biomedical and biotechnological applications.
Thrust 3: Genetically Engineered Cells/Scaffolds for Bone
Tissue Engineering
Tissue-engineered constructs,
consisting of cells dispersed in 3D matrices, have emerged as promising
grafting materials for the repair of non-healing bone defects. However, host
tissue-construct interactions, loss of osteoblastic phenotype under culture
conditions, and limited supply of committed osteoprogenitor cells that will
differentiate into osteoblasts restrict this approach. Our efforts focus engineering mineralizing
templates consisting of cells genetically modified to express the osteoblast
transcription factor Runx2/Cbfa1 and 3-D
polymeric scaffolds to create constructs that promote bone repair. This research encompasses (i) fundamental studies of the function of Runx2 in the
regulation of osteogenesis, (ii) engineering of mineralizing constructs
containing Runx2-genetically engineered cells, both osteogenic and
non-osteogenic cells (e.g., myoblasts, fibroblasts), and (iii) development of
hybrid, multi-tissue interfaces. The
significance of this work lies on the integration of genetic and tissue
engineering strategies to develop autologous grafting templates for
regenerative medicine applications.
Lab Publications
Stephansson SN, Byers BA, and García AJ. Enhanced expression of
the osteoblastic phenotype on substrates that modulate fibronectin conformation
and integrin receptor binding. Biomaterials
23: 2527-2534 (2002). Abstract
Gallant ND
Byers BA, Pavlath GK, Murphy TJ, Karsenty G, and García AJ. Cell type-dependent upregulation
of in vitro mineralization following overexpression of the osteoblast-specific
transcription factor Runx2/Cbfa1. Journal
of Bone and Mineral Research 17: 1931-1944 (2002). Abstract
Cutler SM and García AJ. Engineering cell adhesive surfaces that direct
integrin a5b1 binding
using a recombinant fragment of fibronectin. Biomaterials 24: 1759-1770 (2003).
Abstract
Capadona JR, Collard DM, and García
AJ. Fibronectin adsorption and cell adhesion to mixed monolayers of
tri(ethylene glycol)- and methyl-terminated alkanethiols. Langmuir 19: 1847-1852 (2003). Abstract
Reyes CD and García AJ. Engineering integrin-specific surfaces with a
triple-helical collagen-mimetic peptide. Journal
of Biomedical Materials Research 65A: 511-523 (2003). Abstract
García AJ and
Keselowsky BG, Collard DM, and García AJ. Surface chemistry
modulates fibronectin conformation and directs integrin binding and specificity
to control cell adhesion. Journal of
Biomedical Materials Research 66A: 247-259 (2003). Abstract
Michael KM, Vernakar VN, Keselowsky BG,
Meredith JC, Latour RA, and García AJ.
Adsorption-induced conformational changes in fibronectin due to interactions
with well-defined surface chemistries. Langmuir 19: 8033-8040 (2003). Abstract
Meredith JC, Sormana JL, Keselowsky BG, García
AJ, Tona A, Karim A, and Amis EJ. Combinatorial characterization of cell interactions
with polymer surfaces. Journal of
Biomedical Materials Research 66A: 483-490 (2003). Abstract
Cartmell SH, Porter BD, García AJ,
and Guldberg RE. Effects of media perfusion rate on
cell seeded 3D bone constructs in vitro. Tissue
Engineering 9: 1197-1203 (2003). Abstract
Reyes CD and García AJ. A
centrifugation cell adhesion assay for high-throughput screening of biomaterial
surfaces. Journal of Biomedical Materials
Research 67A: 328-333 (2003). Abstract
García AJ, Guldberg RE, Byers BA, Gersbach
CA, Phillips JE. Genetic engineering with Runx2/Cbfa1 to address cell sourcing
limitations in bone tissue engineering. IEEE
Engineering in Medicine and Biology 22: 65-70 (2003). Abstract
Charest JL, Bryant LE,
García AJ, and King WP. Hot embossing for micro patterned cell substrates. Biomaterials 25: 4767-4775 (2004). Abstract
Keselowsky BG, Collard DM, and García
AJ. Surface chemistry modulates focal adhesion composition and signaling
through changes in integrin binding. Biomaterials
25: 5947-5954 (2004). Abstract
Reyes CD and García AJ. a2b1 integrin-specific
collagen-mimetic surfaces that support osteoblastic differentiation. Journal of Biomedical Materials Research
69A: 591-600 (2004). Abstract
Wilson K, Stuart SJ, García
AJ, and Latour RA. A molecular modeling study of the
effect of surface chemistry on the adsorption of the 7-10 type III segments of
fibronectin. Journal of Biomedical
Materials Research 69A: 686-698 (2004). Abstract
Keselowsky BG and García AJ.
Quantitative methods for analysis of integrin binding and focal adhesion formation
on biomaterial surfaces. Biomaterials
26: 413-418 (2005). Abstract
Brodkin KR, García AJ, and Levenston ME. Chondrocyte phenotypes on different
extracellular matrix monolayers. Biomaterials
25: 5929-5938 (2004). Abstract
Vanderploeg EJ, Imler
SM, Brodkin KR, García AJ and Levenston
ME. Oscillatory tension differentially modulates matrix metabolism and
cytoskeletal organization in chondrocytes and fibrochondrocytes. Journal of Biomechanics 37: 1941-1942
(2004). Abstract
Tate MC, García AJ, Keselowsky BG,
Butcher JT, Penrod AM, García AJ, and Nerem
RM. Differences in morphology and focal adhesion development between valvular and endothelial cells in static and fluid flow
environments. Arteriosclerosis,
Thrombosis and Vascular Biology 24: 1429-1434 (2004). Abstract
Gersbach CA, Byers BA, Pavlath GK,
and García AJ. Runx2/Cbfa1 expression stimulates transdifferentiation of
primary myoblasts into a mineralizing osteoblastic phenotype. Experimental Cell Research 300: 406-417
(2004). Abstract
Byers BA and García AJ. Exogenous Runx2 expression enhances
in vitro osteoblastic differentiation and mineralization in primary bone marrow
stromal cells. Tissue Engineering 10:
1623-1632 (2004). Abstract
Byers BA, Guldberg RE, and
García AJ. Synergy between genetic and tissue engineering: Runx2 overexpression
and in vitro construct development
enhance in vivo mineralization. Tissue Engineering 10: 1757-1766
(2004). Abstract
Reyes CD and García AJ. Bioadhesive surfaces to
promote osteoblast differentiation and bone formation. Journal of Dental Research 84: 407-413 (2005). Abstract
Hutmacher DW and García AJ. Scaffold-based bone engineering by
using genetically modified cells. Gene 347:
1-10 (2005). Abstract
Lan MA, Gersbach CA, Michael
KE, Keselowsky BG, García AJ. Myoblast proliferation
and differentiation on fibronectin-coated self assembled monolayers presenting
different surface chemistries. Biomaterials
26: 4523-4531 (2005). Abstract
Keselowsky BG, Collard DM, García AJ. Integrin binding
specificity regulates biomaterial surface chemistry effects on cell
differentiation. Proceedings of the
National
Nolan CM, Reyes CD, Debord
JD, García AJ, and
García AJ. Get a grip: integrins in cell-biomaterial
interactions. Biomaterials 26:
7525-7529 (2005). Abstract
Capadona JR, Petrie TA,
Fears KP, Latour RA, Collard DM, García AJ. Surface-nucleated assembly of fibrillar extracellular matrices. Advanced Materials 17: 2604-2608 (2005).
Abstract
Charest JL, Eliason MT,
García AJ, King WP, Talin AA, Simmons BA. Polymer cell culture substrates with
combined nanotopographical patterns and
micropatterned chemical domains. Journal
of Vacuum Science and Technology B 23: 3011-3014 (2005).
Charest JL,
Phillips JE, Gersbach CA, Wojtowicz AM, García AJ. Glucocorticoid-induced
osteogenesis is negatively regulated by Runx2/Cbfa1 serine phosphorylation. Journal of Cell Science 119:581-591
(2006). Abstract
Byers BA, Guldberg RE, Hutmacher, DW, García AJ. Effects of Runx2 genetic
engineering and in vitro maturation of tissue-engineered constructs on the
repair of critical size bone defects. Journal
of Biomedical Materials Research 76A: 646-655 (2006). Abstract
Stabenfeldt SE, García AJ, LaPlaca MC.
Thermoreversible laminin-functionalized hydrogel for
neural tissue engineering. Journal of
Biomedical Materials Research 77A: 718-725 (2006). Abstract
People in Lab
Kellie Burns – Lab manager
I-Ming Chung – Post doc; Engineering
materials to modulate morphogenesis
Kristin Michael – Grad student; Role
of FAK in cell adhesion strengthening
Catherine
Reyes – Grad student; Integrin-specific surfaces to enhance
osseointegration
Charlie Gersbach
– Grad student; Runx2-mediated transdifferentiation of myoblasts
Jennifer Phillips – Grad student;
Runx2 & glucocorticoid signaling; tissue engineering
Tim Petrie – Grad student;
Micropatterned biomimetic surfaces to engineer adhesive signaling
Sean Coyer – Grad student; Nanoscale
control of cell adhesion strengthening
Amanda Walls – Grad student; Dynamic biointerfaces to manipulate macrophage function
Abbey Wojtowicz
– Grad student; Runx2-engineered cell/scaffolds to promote bone repair
Dave Dumbauld
– Grad student; Role of vinculin in cell adhesion strengthening
Pete Creighton – Undergrad student;
Surface chemistry and stem cell differentiation
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Recent Graduates
Ben Keselowsky – BME,
Ben Byers –
DePuy Biologics
Nate
Gallant – NIST
Jeff Capadona – VA &
Heungsoo
Shin –
Research Funding
Arthritis
Foundation
Emory/Georgia
Tech Biomedical
National
Institutes of Health
National
Science Foundation
NSF-sponsored
Georgia Tech/Emory Center for the Engineering of Living Tissues
Whitaker
Foundation