Quantifying the relation between bond number and myoblast proliferation.

Many functions of the extracellular matrix can be mimicked by small peptide fragments (e.g., arginine-glycine-aspartic acid (RGD) sequence) of the entire molecule, but the presentation of the peptides is critical to their effects on cells.

Cyclic arginine-glycine-aspartate peptides enhance three-dimensional stem cell osteogenic differentiation.

The role of morphogens in bone regeneration has been widely studied, whereas the effect of matrix cues, particularly on stem cell differentiation, are less well understood. In this work, we investigated the effects of arginine-glycine-aspartate (RGD) ligand conformation (linear vs cyclic RGD) on primary human bone marrow stromal cell (hBMSC) and D1 stem cell osteogenic differentiation in three-dimensional (3D) culture and compared their response with that of committed MC3T3-E1 preosteoblasts to determine whether the stage of cell differentiation altered the response to the adhesion ligands. Linear RGD densities that promoted osteogenic differentiation of committed cells (MC3T3-E1 preosteoblasts) did not induce differentiation of hBMSCs or D1 stem cells, although matrices presenting the cyclic form of this adhesion ligand enhanced osteoprogenitor differentiation in 3D culture.

Regulating myoblast phenotype through controlled gel stiffness and degradation.

Mechanical stiffness and degradability are important material parameters in tissue engineering. The aim of this study was to address the hypothesis that these variables regulate the function of myoblasts cultured in 2-D and 3-D microenvironments. Development of cell-interactive alginate gels with tunable degradation rates and mechanical stiffness was established by a combination of partial oxidation and bimodal molecular weight distribution.

Quantifying the relation between adhesion ligand-receptor bond formation and cell phenotype.

One of the fundamental interactions in cell biology is the binding of cell receptors to adhesion ligands, and many aspects of cell behavior are believed to be regulated by the number of these bonds that form. Unfortunately, a lack of methods to quantify bond formation, especially for cells in 3D cultures or tissues, has precluded direct probing of this assumption. We now demonstrate that a FRET technique can be used to quantify the number of bonds formed between cellular receptors and synthetic adhesion oligopeptides coupled to an artificial extracellular matrix.

Designing scaffolds to enhance transplanted myoblast survival and migration.

Myoblast transplantation is currently limited by poor survival and integration of these cells into host musculature. Transplantation systems that enhance the viability of the cells and induce their outward migration to populate injured muscle may enhance the success of this approach to muscle regeneration. In this study, enriched populations of primary myoblasts were seeded onto delivery vehicles formed from alginate, and the role of vehicle design and local growth factor delivery in cell survival and migration were examined.

Regulating activation of transplanted cells controls tissue regeneration.

Current approaches to tissue regeneration are limited by the death of most transplanted cells and/or resultant poor integration of transplanted cells with host tissue. We hypothesized that transplanting progenitor cells within synthetic microenvironments that maintain viability, prevent terminal differentiation, and promote outward migration would significantly enhance their repopulation and regeneration of damaged host tissue. This hypothesis was addressed in the context of muscle regeneration by transplanting satellite cells to muscle laceration sites on a delivery vehicle releasing factors that induce cell activation and migration (hepatocyte growth factor and fibroblast growth factor 2) or transplantation on materials lacking factor release.

Cellular cross-linking of peptide modified hydrogels.

Peptide modification of hydrogel-forming materials is being widely explored as a means to regulate the phenotype of cells immobilized within the gels. Alternatively, we hypothesized that the adhesive interactions between cells and peptides coupled to the gel-forming materials would also enhance the overall mechanical properties of the gels. To test this hypothesis, alginate polymers were modified with RGDSP-containing peptides and the resultant polymer was used to encapsulate C2C12 myoblasts.

Controlling alginate gel degradation utilizing partial oxidation and bimodal molecular weight distribution.

Degradability is often a critical property of materials utilized in tissue engineering. Although alginate, a naturally derived polysaccharide, is an attractive material due to its biocompatibility and ability to form hydrogels, its slow and uncontrollable degradation can be an undesirable feature. In this study, we characterized gels formed using a combination of partial oxidation of polymer chains and a bimodal molecular weight distribution of polymer.

Protein-based signaling systems in tissue engineering.

Tissue engineering aims to replace damaged tissues or organs using either transplanted cells or host cells recruited to the target site. Protein signaling is crucial to regulate cell phenotype and thus engineered tissue structure and function. Biomaterial vehicles are being designed to incorporate and locally deliver various molecules involved in this signaling, including both growth factors and peptides that mimick whole proteins.