Enhanced Activation and Expansion of T Cells Using Mechanically Soft Elastomer Fibers

Abstract

Practical deployment of cellular therapies requires effective platforms for producing clinically relevant numbers of high-quality cells. This report introduces a materials-based approach to improving activation and expansion of T cells, which are rapidly emerging as an agent for treating cancer and a range of other diseases. Electrospinning is used to create a mesh of poly(ε-caprolactone) fibers, which is used to present activating ligands to CD3 and CD28, which activate T cells for expansion. Incorporation of poly(dimethyl siloxane) elastomer into the fibers reduces substrate rigidity and enhances expansion of mixed populations of human CD4+ and CD8+ T cells. Intriguingly, this platform also rescues expansion of T cells isolated from CLL patients, which often show limited responsiveness and other features resembling exhaustion. By simplifying the process of cell expansion, compared to current bead-based platforms, and improving T cell expansion, the system introduced here may accelerate development of cellular immunotherapy.

Ex vivo induction of regulatory T cells from conventional CD4+ T cells is sensitive to substrate rigidity

“…It was demonstrated that the number of T‐cell population doublings increase when activated by softer beads compared to that by rigid Dynabeads® after 19 days . A similar result was reported recently with a mesh format . These works were followed by many studies on lymphocyte responses to varying substrate rigidities which examine B cell activation, actin dynamics, and microtubule organizations of T cells …”

“…It was shown that polyclonal expansion of peripheral blood T cells (naïve CD4 + and CD8 + T cells) is greater on softer flat PDMS substrates compared to stiff ones . Similar results with fiber formats were reported, as well, that higher proliferation was shown with softer fibers (i.e., various mixtures of PDMS and PCL) than stiff fibers (i.e., PCL only) . Our motivation in this study was to determine if this phenomenon applies to the induction of Tregs from Tconvs, a cell population which is abundant in human blood.…”

“…As a part of the effort to better understand the physiological mechanical microenvironment of the immune system, studies have indicated that stimulating and culturing naïve T cells on softer materials result in significantly higher T-cell activation and cytokine secretion compared to on conventional stiff materials such as glass or polystyrene. [23][24][25][26] More importantly, cell proliferation composes a critical aspect of adoptive cell therapy (ACT). It was shown that polyclonal expansion of peripheral blood T cells (naïve CD4 + and CD8 + T cells) is greater on softer flat PDMS substrates compared to stiff ones.…”

“…25 A similar result was reported recently with a mesh format. 26 These works were followed by many studies on lymphocyte responses to varying substrate rigidities which examine B cell activation, actin dynamics, and microtubule organizations of T cells. [27][28][29] Here, we explore the effect of substrate rigidity on the induction of Tregs from naïve CD4 + Tconvs (Fig.…”

T cell activation and immune synapse organization respond to the microscale mechanics of structured surfaces

“…Contemporary approaches in biomaterials design have provided enhanced control over this branch of immunity, leading to new tools for medicine including vaccination and cellular immunotherapy. Intriguingly, tuning the mechanical rigidity of a substrate used to activate T cells can modulate their subsequent functions including cytokine secretion, proliferation, and population expansion (1)(2)(3)(4)(5). These studies have been carried out predominantly in the context of bulk materials that present to cells planar interfaces that are geometrically and mechanically simplistic.…”