Sulfated Alginate Hydrogels Prolong the Therapeutic Potential of MSC Spheroids by Sequestering the Secretome

Abstract

Cell-based approaches to tissue repair suffer from rapid cell death upon implantation, limiting the window for therapeutic intervention. Despite robust lineage-specific differentiation potential in vitro, the function of transplanted mesenchymal stromal cells (MSCs) in vivo is largely attributed to their potent secretome comprising a variety of growth factors (GFs). Furthermore, GF secretion is markedly increased when MSCs are formed into spheroids. Native GFs are sequestered within the extracellular matrix (ECM) via sulfated glycosaminoglycans, increasing the potency of GF signaling compared to their unbound form. To address the critical need to prolong the efficacy of transplanted cells, alginate hydrogels are modified with sulfate groups to sequester endogenous heparin-binding GFs secreted by MSC spheroids. The influence of crosslinking method and alginate modification is assessed on mechanical properties, degradation rate, and degree of sulfate modification. Sulfated alginate hydrogels sequester a mixture of MSC-secreted endogenous biomolecules, thereby prolonging the therapeutic effect of MSC spheroids for tissue regeneration. GFs are sequestered for longer durations within sulfated hydrogels and retain their bioactivity to regulate endothelial cell tubulogenesis and myoblast infiltration. This platform has the potential to prolong the therapeutic benefit of the MSC secretome and serve as a valuable tool for investigating GF sequestration.

Human iPSC‐Vascular smooth muscle cell spheroids demonstrate size‐dependent alterations in cellular viability and secretory function

“…We and others have used functionalized biomaterials to enhance stem cell survival, and paracrine secretion both in vitro and in vivo 16,37–39 . Spheroids with a 3D tissue‐like architecture have been shown to improve cell‐survival, paracrine secretion, and improved regenerative potential 4,6,8,14,16,21,28 …”

“…16,[37][38][39] Spheroids with a 3D tissue-like architecture have been shown to improve cell-survival, paracrine secretion, and improved regenerative potential. 4,6,8,14,16,21,28 The purpose of this study was to develop a low-cost and reproducible method to form hiPSC-VSMC 3D spheroids of different sizes and evaluate the individual differences between varying sizes to establish the optimal spheroid parameters. We established a selfaggregation method to form spheroids using just agarose-coated, U-bottom microwells.…”

“…3D spheroids have been used to promote cartilage regeneration, treat lung injury, and model epithelial cell behavior 13,17,18 . In comparison to the traditional culture technique of cells in a monolayer, cells cultured as spheroids have demonstrated enhanced cell‐survival, paracrine factor secretion, and tissue forming potential 3,4,6,8,9,19–22 . They also have higher levels of tissue‐specific gene expression and increased exosome production 10,23 .…”

“…13,17,18 In comparison to the traditional culture technique of cells in a monolayer, cells cultured as spheroids have demonstrated enhanced cell-survival, paracrine factor secretion, and tissue forming potential. 3,4,6,8,9,[19][20][21][22] They also have higher levels of tissue-specific gene expression and increased exosome production. 10,23 Overall, spheroids enhance biological processes relating to immunity, inflammation, angiogenesis, and wound healing.…”

Soluble extracts from amnion and chorion membranes improve hMSC osteogenic response in a mineralized collagen scaffold

“…Stem cells can act as endogenous factories of bioactive molecules capable of recruiting host cells to the tissue site, modulating the local inflammatory microenvironment, and promoting angiogenesis [2]. Numerous studies have used biomaterials to sequester mesenchymal stem cell (MSC) produced secretome to modulate the behavior of other cell types such as immune and endothelial cells, highlighting the potential for using bioactive molecules contained by a biomaterial as indirect signals in the absence of direct MSC stimuli [3,4]. The collagen and calcium phosphate mineral composition of bone have inspired a wide range of collagen biomaterials [5][6][7][8].…”