Fundamentals of Multiscale Fabrication Lecture 12 Applications IV: Tissue Engineering Kahp-Yang Suh Associate Professor SNU MAE sky4u@snu.ac.kr

What is tissue engineering?

Regulation of cell and tissue functions by local ECM cues Dynamic cell-matrix interactions in Development Cancer metastasis Wound healing Regeneration Functioning of many cell types in health and disease states can be significantly affected by naturally occurring nanotopographic structures defined by the ECM. Extracellular matrix

SEM of cultured mammalian cells

Elements of the Cytoskeleton Eukaryotic cells contain these main kinds of cytoskeletal filaments – Actin filaments (Microfilaments), Intermediate filaments and Microtubules.

Elements of the Cytoskeleton Microfilaments are found around the periphery of the cell. They also form the contractile element of skeletal muscle Microtubules are found in arrays radiating from the nucleus, in the spindle apparatus and in the basal bodies of cilia Intermediate filaments are seen as cables stretching across the cell and in the nuclear lamina

Cell Adhesion Cell adhesion is the binding of a cell to another cell (“cell-to-cell adhesion”) or to a surface or matrix (“cell-matrix adhesion”) Cellular adhesion is regulated by specific adhesion molecules (“receptors”) that interact with molecules (“ligands” or “counter-receptors”) on the opposing cell or surface. Cell adhesion generally involves protein molecules at the surface of cells, so the study of cell adhesion involves cell adhesion proteins and the molecules that they bind to.

Cell adhesion is highly regulated by many receptors and binding proteins ECM protein: Collagens, Fibronectin, Laminins

Cell adhesion is highly regulated by many receptors and binding proteins The basal lamina is a layer of extracellular matrix on which epithelium sits and which is secreted by the epithelial cells. It is typically about 40-50 nanometers thick. From Wikipedia.

Cell adhesion is highly regulated by many receptors and binding proteins

Immuno-staining of adhesion receptors and cytoskeletal structures

Cell-ECM nanotopography interactions Fibroblasts in 3D Collagen fibers Basement membrane 500 nm 2D flat, rigid surface Cell Tissue Res. 299, 39-46 Better understanding of how the cell behavior changes when cells are placed in a more bio-mimetic microenvironment, modeling the complex ECM nanotopography, will be extremely important for projecting the in vitro finding toward the in vivo cell behavior.

Scalable design and fabrication of scaffold is important Large-area PEG hydrogel nanopattern can mimic the anisotropically aligned ex-vivo myocardium of adult rat heart. Kim et al. PNAS, accepted for publication

Cell Movement through Focal Adhesions (FAs)

Some tissue engineering applications Material rigidity vs Stem cell differentiation Shear stress vs Endothelial cell 표면경도에 따른 줄기세포의 분화 특성 연구 혈관상피세포의 마이크로 유체에 대한 전단력 영향 연구 Engler et al., Cell (2006) Wu et al., PNAS (2007)

Some tissue engineering applications Merits of miniaturization: ‘Sensitivity = Output signal / Input signal‘ so as device miniaturized, it gets more sensitive. Figure. Axon guidance and tissue regeneration on multiscale patterns (courtesy by Prof. Noo-Li Jeon)

Some tissue engineering applications ECM size vs Cell fate Nanoscaffold vs Tissue engineering 단백질 패턴 사이즈에 따른 세포의 성장과 사멸 연구 스캐폴드 길이 스케일에 따른 조직형성 차이 연구 Chen et al., Science (1997) Stevens et al., Science (2005) (review paper)

Heterotypic co-culture platform Some tissue engineering applications Heterotypic co-culture platform Hepatocyte/fibroblast 200 mm Stem cell/fibroblast 200 mm Khademhosseini, Suh, et al., Biomaterials (2004)

Kim et al., Biomaterials (2009) Some tissue engineering applications Cells on nanogrooves: altered cell shape, migration and polarity Capillary force lithography Kim et al., Biomaterials (2009) 10mm Nanogroove containing devices might serve as useful platforms for understanding the mechanisms of directed cell motility and polarization.