The rapidly increasing demand for organ and tissue transplantation has promoted tissue engineering and stem cell research as promising approaches. Tissue engineering combines cells, growth factors and 3D scaffolds for repair and regeneration of biological tissues. To advance tissue engineering research, scaffold properties must be optimized for a given application and cell type. This includes chemical and mechanical properties, shape, and structure and degradation rate.

In addition co-culture approaches are required to allow organization of complex tissue structures. Endothelial cell co-cultures are important for inducing vascularization of engineered tissues. Our experiments in engineered skeletal and cardiac muscle tissue indicate that endothelial cells promote differentiation and organization of co-cultured myoblasts. Endothelial 3D tubular networks were formed within the tissue and shown to promote vascularization upon implantation.

Our recent results using pancreatic islets co-cultures further support the inductive effect of endothelial vessels on islets survival in vitro and in vivo. Given the attractive potential of human embryonic stem cells in tissue regeneration we evaluate the ability to differentiate the cells and induce their 3D organization toward formation of complex tissues.

Porous biodegradable polymer scaffolds are ideal systems for exploring 3D tissue formation, providing support for the cells that can be modulated by modifying cell adhesion sites. Following degradation, the polymers can promote further growth of cells and provide space for remodeling of tissue structures. In addition, degradation of the scaffolds can be used as a tool for localized and controlled growth factor supplementation.

Biodegradable, growth factor-eluting nano-fibers are also used to study embryonic stem cells process in 3D models. Differentiation of the cells is further studied in micro perfusion system to allow the precise localization of a growth factor,  both temporally and spatially using laminar flows. The technique can provide a tool to investigate cell-cell signaling between adjacent embryonic stem cells by maintaining a constant gradient of growth factors in the surrounding culture medium.

Understanding stem cells differentiation and 3D cellular communications can lead to advances in cell therapy and tissue engineering and facilitate organ and tissue regeneration.

Vascularization of engineered tissue constructs

The uniqueness of this approach (developed by Levenberg et al and first published in Nature Biotechnology 2005) is to induce vessel network assembly within 3D tissue constructs in vitro by multicellular culturing of endothelial cells (ECs) and vascular mural cells with cells specific to the tissue of interest.

Levenberg has shown that such in vitro prevascularization of engineered tissue can promote its survival and vascularization upon implantation. The ongoing projects in the lab focus on characterizing the mechanisms of in vitro vascularization and vessel-network formation in multi-cellular tissue constructs by using defined biomaterials and mechanical stimulation designed to mimic in vivo settings.

In addition, this study aims to elucidate the signaling effects and in vivo integration process of engineered vessel network with host vasculature. Several in vivo models are being used for real-time investigation of the vascularization and integration of engineered vascularized constructs.

Moreover, new strategies are being developed for fabrication of engineering vascularized flaps. Additional focus is placed on the effects of interstitial flow and tensile forces on the self-assembly of endothelial cells into vascular networks in vitro. The effects are being characterized and quantified using a combination of bioreactor setups, computational modeling, 3D image analysis and gene expression studies.

This research has received funding from the European Research Council under the European Union’s Seventh Framework Programme (FP/2007–2013)/ERC Grant Agreement no. 281501.

Engineering vascularized cardiac tissue

The aim in this project is to create in vitro pre-vascularized cardiac tissue using a multi-cellular seeding strategy. This strategy involves co-culturing 3 types of cells, namely cardiomyocytes, endothelial cells, and fibroblasts within a nano-patterned scaffold.

Cardiac tissue engineering aims to create functional tissue constructs that can re-establish the structure and function of injured myocardium. The cellular organization of the heart consists primarily of cardiomyocytes, fibroblasts, vascular smooth muscle cells, and endothelial cells.

This research has received funding from the European Research Council under the European Union’s Seventh Framework Programme (FP/2007–2013)/ERC Grant Agreement no. 281501.

Flow-induced vascularization in engineered tissue


subm_5-1024x1024One of today’s major challenges in engineering complex three-dimensional functional tissues is proper vascularization – cells need to be in close proximity (~100µm) to blood vessels in order to survive.

The research focuses on the effects of interstitial flow on the self assembly of endothelial cells into vascular networks in vitro. Using a combination of perfusion-bioreactor design, computational fluid dynamics (CFD) modeling, fluorescence microscopy image analysis and gene expression analysis, we are working to characterize and quantify these effects.

This research has received funding from the European Research Council under the European Union’s Seventh Framework Programme (FP/2007–2013)/ERC Grant Agreement no. 281501.

Engineering skeletal muscle tissue- as graft and flaps for reconstruction of abdominal wall tissue

muscle2This study offers novel reconstruction techniques in the form of an alternative biomaterial implantation (vascularized engineered skeletal muscle tissue), offering the possibility to repair a full-thickness defect of the abdominal wall without the need to transfer tissue (autologous muscle free flap) from another site and minimal postoperative scarification.

This research has received funding from the European Research Council under the European Union’s Seventh Framework Programme (FP/2007–2013)/ERC Grant Agreement no. 281501.

Engineering a vascular niche to support pancreatic islet survival and function and to improve islet transplantation efficacy

vascularized murine isletsThe working hypothesis of this study is that non-nutritional, EC-generated signals may be paramount to in vitro culturing of islets for the purpose of boosting early graft infusion survival prospects.

The study aims to reconstruct pancreatic tissue consisting of islets or beta cell progenitors enriched with a vascular milieu that both supports and promotes graft integration and function. Particular focus is being placed on understanding the inductive signals and characterizing the resulting 3D vascular networks and on evaluating its capacity to treat a Type 1 diabetes.

This research has received funding from the European Research Council under the European Union’s Seventh Framework Programme (FP/2007–2013)/ERC Grant Agreement no. 281501.

spinal cord injury regeneration

spinalSpinal cord injury is devastating to both patients and their families. Among the strategies being investigated to promote regeneration is the transplantation of stem cells. We aims to exploit the supportive properties of stem cells and other neuronal cells in combination with endothelial cells and a biodegradable scaffold, as a strategy to preserve spared neural tissue, and promote a more hospitable environment for vasculogenesis and neural regeneration.

Cell mechanics in 3D constructs

Slideshow_1In this project we investigate the mechanical interplay between cells and scaffold within 3D engineered constructs.

We examine the influence of cells seeded within scaffold via measurements of contractile forces and the influence of mechanical constraints of the scaffold on cell behavior mainly focusing on embryonic stem cells differentiation.   We combine different methods such as tissue engineering techniques, bioreactors (and new designs), gene analysis and finite elements modeling.

Droplet Based Microfluidics

C03_10x_1We have developed innovative methods to create and manipulate nanoliter volume droplets in microfluidic channels. We are able to achieve on demand generation of nanoliter droplets, purely hydrodynamic droplet sorting, and accurate droplet composition control.

Our latest work brought stationary nanoliter droplet arrays on a substrate of choice for the culture and analysis of single adherent and non-adherent cells. We are currently using  these modules to answer biological questions by implementing single cell assays.

The Rina and Avner Schneur Center of Diabetes Research

The Rina and Avner Schneur Center of Diabetes Research lead by Prof. Levenberg, brings together top researchers from the faculty of Biomedical engineering and the Faculty of Medicine at the Technion-Israel Institute of Technology to seek for a cure to type II diabetes.

Type II Diabetes (DM2) is one of the most important public health challenges requiring a cure rather than preventive treatment. The current project (In collaboration with Prof Eddy Karnieli) focuses on the development of a new cure for this important disease in the form of transplantation of engineered tissue, which will provide a useful tool to reach better systemic glucose homeostasis in DM2.