Accumulating evidence suggests that the mechanical and biochemical signals originating from cell–cell adhesion are critical for stem cell lineage specification. In this review, we focus on the role ...of cadherin mediated signaling in development and stem cell differentiation, with emphasis on two well-known cadherins, cadherin-2 (CDH2) (N-cadherin) and cadherin-11 (CDH11) (OB-cadherin). We summarize the existing knowledge regarding the role of CDH2 and CDH11 during development and differentiation in vivo and in vitro. We also discuss engineering strategies to control stem cell fate decisions by fine-tuning the extent of cell–cell adhesion through surface chemistry and microtopology. These studies may be greatly facilitated by novel strategies that enable monitoring of stem cell specification in real time. We expect that better understanding of how intercellular adhesion signaling affects lineage specification may impact biomaterial and scaffold design to control stem cell fate decisions in three-dimensional context with potential implications for tissue engineering and regenerative medicine.
•The role of CDH11 and CDH2 in development and morphogenesis•The role of CDH2 and CDH11 during MSC lineage commitment•CDH11 mediated AJ formation promotes MSC differentiation into SMC.•Directing stem cell fate by controlling intracellular adhesion•Engineering cell–cell adhesion to direct stem cell fate decisions
Recently our group demonstrated that acellular tissue engineered vessels (A-TEVs) comprised of small intestinal submucosa (SIS) immobilized with heparin and vascular endothelial growth factor (VEGF) ...could be implanted into the arterial system of a pre-clinical ovine animal model, where they endothelialized within one month and remained patent. Here we report that immobilized VEGF captures blood circulating monocytes (MC) with high specificity under a range of shear stresses. Adherent MC differentiate into a mixed endothelial (EC) and macrophage (Mφ) phenotype and further develop into mature EC that align in the direction of flow and produce nitric oxide under high shear stress. In-vivo, newly recruited cells on the vascular lumen express MC markers and at later times they co-express MC and EC-specific proteins and maintain graft patency. This novel finding indicates that the highly prevalent circulating MC contribute directly to the endothelialization of acellular vascular grafts under the right chemical and biomechanical cues.
Abstract The large number of coronary artery bypass procedures necessitates development of off-the-shelf vascular grafts that do not require cell or tissue harvest from patients. However, immediate ...thrombus formation after implantation due to the absence of a healthy endothelium is very likely. Here we present the successful development of an acellular tissue engineered vessel (A-TEV) based on small intestinal submucosa that was functionalized sequentially with heparin and VEGF. A-TEVs were implanted into the carotid artery of an ovine model demonstrating high patency rates and significant host cell infiltration as early as one week post-implantation. At one month, a confluent and functional endothelium was present and the vascular wall showed significant infiltration of host smooth muscle cells exhibiting vascular contractility in response to vaso-agonists. After three months, the endothelium aligned in the direction of flow and the medial layer comprised of circumferentially aligned smooth muscle cells. A-TEVs demonstrated high elastin and collagen content as well as impressive mechanical properties and vascular contractility comparable to native arteries. This is the first demonstration of successful endothelialization, remodeling, and development of vascular function of a cell-free vascular graft that was implanted in the arterial circulation of a pre-clinical animal model.
Cell-free tissue-engineered vascular grafts provide a promising alternative to treat cardiovascular disease but timely endothelialization is essential for ensuring patency and proper functioning ...post-implantation. Recent studies from our lab showed that blood cells like monocytes (MCs) and macrophages (Mφ) may contribute directly to cellularization and regeneration of bioengineered arteries in small and large animal models. While MCs and Mφ are leukocytes that are part of the innate immune response, they share common developmental origins with endothelial cells (ECs) and are known to play crucial roles during vessel formation (angiogenesis) and vessel repair after inflammation/injury. They are highly plastic cells that polarize into proinflammatory and anti-inflammatory phenotypes upon exposure to cytokines; and differentiate into other cell types, including EC-like cells, in the presence of appropriate chemical and mechanical stimuli. This review focuses on the developmental origins of MCs and ECs; the role of MCs and Mφ in vessel repair/regeneration during inflammation/injury; and the role of chemical signaling and mechanical forces in Mφ inflammation that mediates vascular graft regeneration. We postulate that comprehensive understanding of these mechanisms will better inform the development of strategies to coax MCs/Mφ into endothelializing the lumen and regenerate the smooth muscle layers of cell-free bioengineered arteries and veins that are designed to treat cardiovascular diseases and perhaps the native vasculature as well.
ABSTRACTRecently, our group demonstrated that immobilized VEGF can capture flowing endothelial cells (ECs) from the blood in vitro and promote endothelialization and patency of acellular ...tissue–engineered vessels (A‐TEVs) into the arterial system of an ovine animal model. Here, we demonstrate implantability of submillimeter diameter heparin and VEGF‐decorated A‐TEVs in a mouse model and discuss the cellular and immunologic response. At 1 mo postimplantation, the graft lumen was fully endothelialized, as shown by expression of EC markers such as CD144, eNOS, CD31, and VEGFR2. Interestingly, the same cells coexpressed leukocyte/macrophage (Mϕ) markers CD14, CD16, VEGFR1, CD38, and EGR2. Notably, there was a stark difference in the cellular makeup between grafts containing VEGF and those containing heparin alone. In VEGF‐containing grafts, infiltrating monocytes (MCs) converted into anti‐inflammatory M2‐Mϕs, and the grafts developed well‐demarcated luminal and medial layers resembling those of native arteries. In contrast, in grafts containing only heparin, MCs converted primarily into M1‐Mϕs, and the endothelial and smooth muscle layers were not well defined. Our results indicate that VEGF may play an important role in regulating A‐TEV patency and regeneration, possibly by regulating the inflammatory response to the implants.—Smith, R. J., Jr., Yi, T., Nasiri, B., Breuer, C. K., Andreadis, S. T. Implantation of VEGF‐functionalized cell‐free vascular grafts: regenerative and immunological response. FASEB J. 33, 5089–5100 (2019). www.fasebj.org
We discovered that Cadherin-11 (CDH11) regulates collagen and elastin synthesis, both affecting the mechanical properties and contractile function of animal tissues. Using a Cdh11-null mouse model, ...we observed a significant reduction in the mechanical properties Youngs' modulus and ultimate tensile strength (UTS) of Cdh11(-/-) as compared to wild-type (WT) mouse tissues, such as the aorta, bladder and skin. The deterioration of mechanical properties (Youngs' modulus and UTS) was accompanied by reduced collagen and elastin content in Cdh11(-/-) mouse tissues as well as in cells in culture. Similarly, knocking down CDH11 abolished collagen and elastin synthesis in human cells, and consequently reduced their ability to generate force. Conversely, engagement of CDH11 through homophilic interactions, led to swift activation of the TGF-β and ROCK pathways as evidenced by phosphorylation of downstream effectors. Subsequently, activation of the key transcription factors, MRTF-A (also known as MKL1) and MYOCD led to significant upregulation of collagen and elastin genes. Taken together, our results demonstrate a novel role of adherens junctions in regulating extracellular matrix (ECM) synthesis with implications for many important biological processes, including maintenance of tissue integrity, wound healing and tissue regeneration.
Neural crest (NC) cells are a multipotent stem cell population that give rise to a diverse array of cell types in the body, including peripheral neurons, Schwann cells (SC), craniofacial cartilage ...and bone, smooth muscle cells, and melanocytes. NC formation and differentiation into specific lineages takes place in response to a set of highly regulated signaling and transcriptional events within the neural plate border. Premigratory NC cells initially are contained within the dorsal neural tube from which they subsequently emigrate, migrating to often distant sites in the periphery. Following their migration and differentiation, some NC‐like cells persist in adult tissues in a nascent multipotent state, making them potential candidates for autologous cell therapy. This review discusses the gene regulatory network responsible for NC development and maintenance of multipotency. We summarize the genes and signaling pathways that have been implicated in the differentiation of a postmigratory NC into mature myelinating SC. We elaborate on the signals and transcription factors involved in the acquisition of immature SC fate, axonal sorting of unmyelinated neuronal axons, and finally the path toward mature myelinating SC, which envelope axons within myelin sheaths, facilitating electrical signal propagation. The gene regulatory events guiding development of SC in vivo provides insights into means for differentiating NC‐like cells from adult human tissues into functional SC, which have the potential to provide autologous cell sources for the treatment of demyelinating and neurodegenerative disorders.
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Native tissues orchestrate their functions by complex interdependent cascades of biochemical and biophysical cues that vary spatially and temporally during cellular processes. ...Scaffolds with well-tuned structural, mechanical, and biochemical properties have been developed to guide cell behavior and provide insight on cell-matrix interaction. However, static scaffolds very often fail to mimic the dynamicity of native extracellular matrices. Stimuli-responsive scaffolds have emerged as powerful platforms that capture vital features of native tissues owing to their ability to change chemical and physical properties in response to cytocompatible stimuli, thus enabling on-demand manipulation of cell microenvironment. The vast expansion in biorthogonal chemistries and stimuli-responsive functionalities has fuelled further the development of new smart scaffolds that can permit multiple irreversible or reversible spatiotemporal modulation of cell-directing cues, thereby prompting in-depth studies to interpret the decisive elements that regulate cell behavior. Integration of stimuli-responsive hydrogels with current biofabrication technologies has allowed the development of dynamic scaffolds with organizational features and hierarchical architectures similar to native tissues. This review highlights the progress achieved using stimuli-responsive hydrogels in fundamental cell biology studies, with particular emphasis on the interplay between chemistry, biomaterials design, and biofabrication technologies for manipulation of cell microenvironment.
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