IKVAV modified - Laminin functional hydrogel
Several peptides have been synthesized from active extracellular matrix motifs. Of these, peptides derived from active sites on laminin have been used to study multiple biological and pathological functions. IKVAV (Ile‐Lys‐Val‐ala‐Val) is an active site on the laminin α1 which binds integrin receptors1. IKVAV was initially shown to regulate cell adhesion, migration, differentiation, angiogenesis, and neurite outgrowth1. However, IKVAV was soon discovered to be a powerful activator of tumor growth and metastasis2. IKVAV can be used in many cell lines to study multiple cellular processes in two- and three-dimensional (3D) environments.
The ability of IKVAV to promote neuronal differentiation and neurite extension has been thoroughly studied in typical two-dimensional environments, 3D hydrogels, and in vivo. The covalent immobilization of IKVAV into hydrogels allows for the formation of nanofiber matrices with active integrin-binding sites3,4. This 3D system promotes neural stem cell adhesion5, and subsequent viability and differentiation into neurons3,4. Myriad studies have also demonstrated the robust growth-promoting effects of IKVAV on neurite extension. PC12 cells showed enhanced neurite outgrowth when cultured in 3D hydrogels with covalently linked IKVAV relative to cells cultured in hydrogels without IKVAV or other laminin peptides6. Furthermore, Hynd et. al. (2007) elegantly demonstrated increased neurite outgrowth of primary rat hippocampal neurons on hydrogels containing patterns of extracellular matrix proteins, including IKVAV5. The ability of IKVAV to promote neurite outgrowth, and more importantly to act as a guidance cue, has also been observed using a photoactivatable version of the peptide7. However, despite the evidence demonstrating the promotion of neurite extension, IKVAV has also been found to inhibit neurite outgrowth of chick dorsal root ganglion neurons6. These differences on neuritogenesis seem to be subtype dependent and further illustrate the utility of IKVAV. In addition to studying neuronal differentiation, adhesion, and neurite extension, IKVAV 3D modified hydrogels have been used as a system to deliver neural progenitor cells into injured brains for purposes of regeneration4,8. IKVAV plays a critical role in facilitating cell survival in these 3D injectable hydrogels to allow for transplantation of new neural progenitors at injury sites4,9–11. In addition, 3D hydrogel structures containing IKVAV peptides have been used to provide the necessary substrata for the regeneration of injured axons after lesion in the cortex12, spinal cord13, cerebellum14, sciatic nerve11, and cochlea15. Overall, evidence shows that IKVAV has a robust influence on neuron development and function.
Extracellular matrix proteins can act as an attractive environment for motile cancer cells, leading to an increase in migration and invasion, and ultimately metastasis. Moreover, laminin receptor expression positively correlates with malignancy. Therefore, the use of peptides derived from extracellular matrix motifs has been used to study cancer cell growth and metastasis. In a hallmark study, Tashiro and colleagues found enhanced invasion and metastatic behavior in a mouse melanoma cell lines in response to IKVAV peptide (K1735 and B16F10)16. The metastatic activity induced by IKVAV also correlates with increased collagenase IV production in both human17 and mouse16 melanoma cells. Other studies have observed increased attachment of cancer cells to hydrogels in the presence of IKVAV, allowing for greater cluster growth, indicative of tumor growth5,18. Interestingly, IKVAV induced morphological changes and increased cell growth of PC-3 cells, a human prostate cancer line from bone metastasis19. Often this increased cancer cell adhesion is accompanied by increased proliferation and subsequent invasion of metastatic cells16,18,19. Taken together, it is apparent IKVAV is a useful tool for the study of cancer cell processes.
While most of the research utilizing IKVAV in cell culture experiments have focused on neurons and cancer cells, an array of additional studies has investigated the effects of IKVAV in other cells types. IKVAV has been found to promote adhesion of different cell types, such as skin fibroblasts 20, pulmonary fibroblasts21, olfactory ensheathing cells22, and human umbilical vein endothelial cells23. In addition to effects on cell adhesion, IKVAV can promote the organization of cells into dynamic structures. In one such study, IKVAV played a key role in promoting angiogenesis of endothelial cells and human bone marrow-derived mesenchymal stem cells to form vascular structures24. Moreover, identifying biochemical and mechanical cues to promote stem cell viability, adhesion, and differentiation is critical in developing 3D structures for tissue engineering. IKVAV is an important tool that regulates stem cell survivability and differentiation. IKVAV can promote the attachment and viability of adipose-derived stem cells25, mesenchymal stem cells26, and neural stem cells4,8, further illustrating the many uses of IKVAV.
The value of IKVAV has further been demonstrated in accompaniment with another popular extracellular matrix peptide, RGD (Arg-Gly-Asp). The combination of IKVAV and RGD has been found to have strong effects on neurons and cancer cells. The additive effect of IKVAV and RGD promotes the survival and differentiation of neural progenitor cells8. Additionally, IKVAV and RGD have been shown to promote axonal regeneration in transected rat sciatic nerves in vivo3. In short, hydrogels with covalently bound IKVAV and RGD were injected into the transected rat sciatic nerve gap forming a substratum for injured nerves to grow across. In addition, the synergistic effects of IKVAV and RGD cause cancer-promoting results. Breast cancer cells adhere strongly to IKVAV and RGD, leading to increased cell spreading and cluster growth27. Finally, IKVAV and RGD have been shown to have additive effects on other cell types. Researchers have observed increased cell viability in induced pluripotent stem cells28 and human mesenchymal stem cells26. This combination of extracellular matrix peptides also promoted myotube formation from mouse muscle cells29. These data demonstrate the many uses of combining IKVAV and RGD in hydrogels to study a variety of cellular processes in many cell types.
Cell Type Behavior Reference Table for VitroGel IKVAV
|Glioma LRM55||Promoted cell attachment|
|Melanoma A2058||Increased type IV collagenolytic activity|
|Melanoma K-1735||Increased cell invasion|
|Melanoma SK-MEL-28||Increased cell adhesion and proliferation|
|Prostate PC3||Increased cell growth and invasion|
|Human neural stem cells||Promoted cell viability and differentiation|
|Mouse neural progenitor cel||Promoted cell adhesion and differentiation|
|Mouse spiral ganglion neurons||Promoted neurite outgrowth|
|Neural PC12||Promoted neurite outgrowth|
|Rat cortical astrocytes||Increased cell adhesion|
|Rat neural stem cells||Promote cell attachment and differentiation|
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 F. A. Somaa et al., “Peptide-Based Scaffolds Support Human Cortical Progenitor Graft Integration to Reduce Atrophy and Promote Functional Repair in a Model of Stroke,” Cell Rep., 2017, doi: 10.1016/j.celrep.2017.07.069.
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 E. M. do. Reis, F. V. Berti, G. Colla, and L. M. Porto, “Bacterial nanocellulose-IKVAV hydrogel matrix modulates melanoma tumor cell adhesion and proliferation and induces vasculogenic mimicry in vitro,” J. Biomed. Mater. Res. – Part B Appl. Biomater., 2018, doi: 10.1002/jbm.b.34055.
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 H. N. Chia, M. Vigen, and A. M. Kasko, “Effect of substrate stiffness on pulmonary fibroblast activation by TGF-β,” Acta Biomater., 2012, doi: 10.1016/j.actbio.2012.03.027.
 H. Xu et al., “Effects of self-assembled IKVAV peptide nanofibers on olfactory ensheathing cells,” Shengwu Gongcheng Xuebao/Chinese J. Biotechnol., 2009.
 J. P. Jung, A. K. Nagaraj, E. K. Fox, J. S. Rudra, J. M. Devgun, and J. H. Collier, “Co-assembling peptides as defined matrices for endothelial cells,” Biomaterials, 2009, doi: 10.1016/j.biomaterials.2009.01.033.
 W. Sun et al., “Co-culture of outgrowth endothelial cells with human mesenchymal stem cells in silk fibroin hydrogels promotes angiogenesis,” Biomed. Mater., 2016, doi: 10.1088/1748-6041/11/3/035009.
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