Tuning cytokines enriches dendritic cells and regulatory T cells in the periodontium.

Background: Periodontal disease results from the pathogenic interactions between the tissue, immune system, and microbiota; however, standard therapy fails to address the cellular mechanism underlying the chronic inflammation. Dendritic cells (DC) are key regulators of T cell fate, and biomaterials that recruit and program DC locally can direct T cell effector responses. We hypothesized that a biomaterial that recruited and programmed DC toward a tolerogenic phenotype could enrich regulatory T cells within periodontal tissue, with the eventual goal of attenuating T cell mediated pathology.

The effects of processing methods upon mechanical and biologic properties of porcine dermal extracellular matrix scaffolds.

Biologic materials from various species and tissues are commonly used as surgical meshes or scaffolds for tissue reconstruction. Extracellular matrix (ECM) represents the secreted product of the cells comprising each tissue and organ, and therefore provides a unique biologic material for selected regenerative medicine applications. Minimal disruption of ECM ultrastructure and content during tissue processing is typically desirable.

Patterning alginate hydrogels using light-directed release of caged calcium in a microfluidic device.

This paper describes a simple reversible hydrogel patterning method for 3D cell culture. Alginate gel is formed in select regions of a microfluidic device through light-triggered release of caged calcium. In the pre-gelled alginate solution, calcium is chelated by DM-nitrophen (DM-n) to prevent cross-linking of alginate.

Cancer cell angiogenic capability is regulated by 3D culture and integrin engagement.

Three-dimensional culture alters cancer cell signaling; however, the underlying mechanisms and importance of these changes on tumor vascularization remain unclear. A hydrogel system was used to examine the role of the transition from 2D to 3D culture, with and without integrin engagement, on cancer cell angiogenic capability. Three-dimensional culture recreated tumor microenvironmental cues and led to enhanced interleukin 8 (IL-8) secretion that depended on integrin engagement with adhesion peptides coupled to the polymer.

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.

Integrin-adhesion ligand bond formation of preosteoblasts and stem cells in three-dimensional RGD presenting matrices.

Cell-interactive polymers have been widely used as synthetic extracellular matrices to regulate cell function and promote tissue regeneration. However, there is a lack of quantitative understanding of the cell-material interface. In this study, integrin-adhesion ligand bond formation of preosteoblasts and D1 stem cells with RGD presenting alginate matrices were examined using FRET and flow cytometry.

AFM imaging of RGD presenting synthetic extracellular matrix using gold nanoparticles.

Several high-resolution imaging techniques such as FESEM, TEM and AFM are compared with respect to their application on alginate hydrogels, a widely used polysaccharide biomaterial. A new AFM method applicable to RGD peptides covalently conjugated to alginate hydrogels is described. High-resolution images of RGD adhesion ligand distribution were obtained by labeling biotinylated RGD peptides with streptavidin-labeled gold nanoparticles.

Differentiation stage alters matrix control of stem cells.

Cues from the material to which a cell is adherent (e.g., adhesion ligand presentation, substrate elastic modulus) clearly influence the phenotype of differentiated cells.

Upregulation of bone cell differentiation through immobilization within a synthetic extracellular matrix.

There is a need for new therapeutic strategies to treat bone defects caused by trauma, disease or tissue loss. Injectable systems for cell transplantation have the advantage of allowing the use of minimally invasive surgical procedures, and thus for less discomfort to patients. In the present study, it is hypothesized that Arg-Gly-Asp (RGD)-coupled in a binary (low and high molecular weight) injectable alginate composition is able to influence bone cell differentiation in a three-dimensional (3D) structure.

Nanoscale cell adhesion ligand presentation regulates nonviral gene delivery and expression.

It is hypothesized that the nanoscale organization of cell adhesion ligands in a synthetic ECM regulates nonviral gene delivery. This hypothesis was examined with pre-osteoblasts cultured on substrates which present varied density and spacing of synthetic adhesion ligands. The levels of gene transfer and expression were increased with the density of adhesion ligands, but decreased with the spacing of ligands, due to changes in the cell growth rate.

Regulation of chondrocyte differentiation level via co-culture with osteoblasts.

The close apposition of osteoblasts and chondrocytes in bone and their interaction during bone development and regeneration suggest that they may each regulate the other's growth and differentiation. In these studies, osteoblasts and chondrocytes were co-cultured in vitro, with both direct and indirect contact. Proliferation of the co-cultured chondrocytes was enhanced using soluble factors produced from the osteoblasts, and the differentiation level of the osteoblasts influenced the differentiation level of the chondrocytes.

Multi-scale modeling to predict ligand presentation within RGD nanopatterned hydrogels.

The adhesion ligand RGD has been coupled to various materials to be used as tissue culture matrices or cell transplantation vehicles, and recent studies indicate that nanopatterning RGD into high-density islands alters cell adhesion, proliferation, and differentiation. However, elucidating the impact of nanopattern parameters on cellular responses has been stymied by a lack of understanding of the actual ligand presentation within these systems. We have developed a multi-scale predictive modeling approach to characterize the adhesion ligand nanopatterns within an alginate hydrogel matrix.

Dual growth factor delivery and controlled scaffold degradation enhance in vivo bone formation by transplanted bone marrow stromal cells.

Supraphysiological concentrations of exogenous growth factors are typically required to obtain bone regeneration, and it is unclear why lower levels are not effective. We hypothesized that delivery of bone progenitor cells along with appropriate combinations of growth factors and scaffold characteristics would allow physiological doses of proteins to be used for therapeutic bone regeneration. We tested this hypothesis by measuring bone formation by rat bone marrow stromal cells (BMSCs) transplanted ectopically in SCID mice using alginate hydrogels.

Effects of a bone-like mineral film on phenotype of adult human mesenchymal stem cells in vitro.

Multipotent cell types are rapidly becoming key components in a variety of tissue engineering schemes, and mesenchymal stem cells (MSCs) are emerging as an important tool in bone tissue regeneration. Although several soluble signals influencing osteogenic differentiation of MSCs in vitro are well-characterized, relatively little is known about the influence of substrate signals. This study was aimed at elucidating the effects of a bone-like mineral (BLM), which is vital in the process of bone bonding to orthopedic implant materials, on the osteogenic differentiation of human MSCs in vitro.

Nanoscale Adhesion Ligand Organization Regulates Osteoblast Proliferation and Differentiation.

It was hypothesized that nanoscale adhesion ligand spacing regulates cell adhesion, proliferation, and differentiation, and that this control can be decoupled from the overall ligand density. Alginate was chemically modified with a peptide containing the cell adhesion sequence arginine-glycine-aspartic acid (RGD), and the nanoscale spacing of RGD ligands in alginate gels was varied. A decrease in the RGD island spacing from 78 to 36 nm upregulated the proliferation rates of MC3T3-E1 cells from 0.