It is known that the cell environment such as biomechanical properties and extracellular matrix (ECM) composition dictate cell behaviour including migration, proliferation, and differentiation. Important constituents of the microenvironment, including ECM molecules such as proteoglycans and glycosaminoglycans (GAGs), determine events in both embryogenesis and repair of the adult lung. Mesenchymal stromal/stem cells (MSC) have been shown to have immunomodulatory properties and may be potent actors regulating tissue remodelling and regenerative cell responses upon lung injury. Using MSC in cell-based therapy holds promise for treatment of chronic lung diseases such as idiopathic pulmonary fibrosis (IPF) and chronic obstructive pulmonary disease (COPD). However, so far clinical trials with MSCs in COPD have not had a significant impact on disease amelioration nor on IPF, where low cell survival rate and pulmonary retention time are major hurdles to overcome. Research shows that the microenvironment has a profound impact on transplanted MSCs. In our studies on acellular lung tissue slices (lung scaffolds) from IPF patients versus healthy individuals, we see a profound effect on cellular activity, where healthy cells cultured in diseased lung scaffolds adapt and produce proteins further promoting a diseased environment, whereas cells on healthy scaffolds sustain a healthy proteomic profile. Therefore, modulating the environmental context for cell-based therapy may be a potent way to improve treatment using MSCs. In this review, we will describe the importance of the microenvironment for cell-based therapy in chronic lung diseases, how MSC-ECM interactions can affect therapeutic output and describe current progress in the field of cell-based therapy.

Mesenchymal stromal cell (MSC)-based therapies for inflammatory diseases rely mainly on the paracrine ability to modulate the activity of macrophages. Despite recent advances, there is scarce information regarding changes of the secretome content attributed to physiomimetic cultures and, especially, how secretome content influence on macrophage activity for therapy. hLMSCs from human donors were cultured on devices developed in house that enabled lung-mimetic strain. hLMSC secretome was analyzed for typical cytokines, chemokines and growth factors. RNA was analyzed for the gene expression of CTGF and CYR61. Human monocytes were differentiated to macrophages and assessed for their phagocytic capacity and for M1/M2 subtypes by the analysis of typical cell surface markers in the presence of hLMSC secretome. CTGF and CYR61 displayed a marked reduction when cultured in lung-derived hydrogels (L-Hydrogels). The secretome showed that lung-derived scaffolds had a distinct secretion while there was a large overlap between L-Hydrogel and the conventionally (2D) cultured samples. Additionally, secretome from L-Scaffold showed an HGF increase, while IL-6 and TNF-α decreased in lung-mimetic environments. Similarly, phagocytosis decreased in a lung-mimetic environment. L-Scaffold showed a decrease of M1 population while stretch upregulated M2b subpopulations. In summary, mechanical features of the lung ECM and stretch orchestrate anti-inflammatory and immunosuppressive outcomes of hLMSCs.

Healthy regeneration of tissue relies on a well-orchestrated release of growth factors. Herein, we show the use of synthetic glycosaminoglycans for controlled binding and release of growth factors to induce a desired cellular response. First, we screened glycosaminoglycans with growth factors of interest to determine kon (association rate constant), koff (dissociation rate constant), and Kd (equilibrium rate constant). As proof-of-concept, we functionalized an elastin-like recombinamer (ELR) hydrogel with a synthetic glycosaminoglycan and immobilized fibroblast growth factor 2 (FGF2), demonstrating that human umbilical vein endothelial cells cultured on top of ELR hydrogel differentiated into tube-like structures. Taking this concept further, we developed a tunable macroporous ELR cryogel material, containing a synthetic glycosaminoglycan and FGF2 that showed increased blood vessel formation and reduced immune response compared to control when implanted in a subcutaneous mouse model. These results demonstrated the possibility for specific release of desired growth factors in/from a modular 3D scaffold in vitro and in vivo.

Fluorescently labeled xylosides are taken up by cells and initiate priming of labeled GAG chains of various length.

We present a xylosylated naphthoxyloside carrying a terminal azide functionality that can be used for conjugation using click chemistry. We show that this naphthoxyloside serves as a substrate for β4GalT7 and induces the formation of soluble glycosaminoglycan (GAG) chains with physiologically relevant lengths and sulfation patterns. Finally, we demonstrate its usefulness by conjugation to the Alexa Fluor 647 and TAMRA fluorophores and coupling to a surface plasmon resonance chip for interaction studies with the hepatocyte growth factor known to interact with the GAG heparan sulfate.