Matrix-bound vesicles within ECM bioscaffolds provide mechanistic insight into inductive properties.

The early macrophage response to biomaterials has been shown to be a critical and predictive determinant of downstream outcomes. When properly prepared, bioscaffolds composed of mammalian extracellular matrix (ECM) have been shown to promote a transition in macrophage behavior from a proinflammatory to a regulatory/anti-inflammatory phenotype, which in turn has been associated with constructive and functional tissue repair. The mechanism by which ECM bioscaffolds promote this phenotypic transition, however, is poorly understood. The present study shows that matrix-bound nanovesicles (MBV), a component of ECM bioscaffolds, are capable of recapitulating the macrophage activation effects of the ECM bioscaffold from which they are derived. MBV isolated from two different source tissues, porcine urinary bladder and small intestinal submucosa, were found to be enriched in miRNA125b-5p, 143-3p, and 145-5p. Inhibition of these miRNAs within macrophages was associated with a gene and protein expression profile more consistent with a proinflammatory rather than an anti-inflammatory/regulatory phenotype. MBV and their associated miRNA cargo appear to play a significant role in mediating the effects of ECM bioscaffolds on macrophage phenotype.

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Central nervous system neurons often degenerate after trauma due to the inflammatory innate immune response to injury, which can lead to neuronal cell death, scarring, and permanently lost neurologic function. Extracellular matrix bioscaffolds, derived by decellularizing healthy tissues, have been widely used in both preclinical and clinical studies to promote positive tissue remodeling, including neurogenesis, in numerous tissues, with extracellular matrix from homologous tissues often inducing more positive responses. Extracellular matrix hydrogels are liquid at room temperature and enable minimally invasive extracellular matrix injections into central nervous system tissues, before gelation at 37℃. However, few studies have analyzed how extracellular matrix hydrogels influence primary central nervous system neuron survival and growth, and whether central nervous system and non-central nervous system extracellular matrix specificity is critical to neuronal responses. Urinary bladder extracellular matrix hydrogels increase both primary hippocampal neuron survival and neurite growth to similar or even greater extents, suggesting extracellular matrix from non-homologous tissue sources, such as urinary bladder matrix-extracellular matrix, may be a more economical and safer alternative to developing central nervous system extracellular matrices for central nervous system applications. Additionally, we show matrix-bound vesicles derived from urinary bladder extracellular matrix are endocytosed by hippocampal neurons and positively regulate primary hippocampal neuron neurite growth. Matrix-bound vesicles carry protein and RNA cargos, including noncoding RNAs and miRNAs that map to the human genome and are known to regulate cellular processes. Thus, urinary bladder matrix-bound vesicles provide natural and transfectable cargoes which offer new experimental tools and therapeutic applications to study and treat central nervous system neuron injury.

Identification of matrix-bound nanovesicles (MBV) as ubiquitous components of the extracellular matrix (ECM) raises questions regarding their biologic functions and their potential theranostic application. Unlike liquid-phase extracellular vesicles (e.g., exosomes), MBV are tightly bound to the ECM, which makes their isolation and harvesting more challenging. The indiscriminate use of different methods to harvest MBV can alter or disrupt their structural and/or functional integrity. The objective of the present study was to compare the effect of various MBV harvesting methods upon yield, purity, and biologic activity. Combinations of four methods to solubilize the ECM (collagenase [COL], liberase [LIB], or proteinase K [PK] and nonenzymatic elution with potassium chloride) and four isolation methods (ultracentrifugation, ultrafiltration [UF], density barrier, and size exclusion chromatography [SEC]) were used to isolate MBV from urinary bladder-derived ECM. All combinations of solubilization and isolation methods allowed for the harvesting of MBV, however, distinct differences were noted. The highest yield, purity, cellular uptake, and biologic activity were seen with MBV isolated by a combination of liberase or collagenase followed by SEC. The combination of proteinase K and UF was shown to have detrimental effects on bioactivity. The results show the importance of selecting appropriate MBV harvesting methods for the characterization and evaluation of MBV and for analysis of their potential theranostic application.

vation and mitochondrial dysfunction. The present paper reviews regenerative medicine strategies that seek to restore adequate skeletal muscle structure and function including exogenous delivery of cells and pharmacological therapies to induce myogenesis or reverse the physiologic changes that result in the disease. Approaches that modify the microenvironment to provide an environment conducive to reversal and mitigation of the disease represent a potential regenerative medicine approach that is discussed herein.

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Chronic inflammatory gastric reflux alters the esophageal microenvironment and induces metaplastic transformation of the epithelium, a precancerous condition termed Barrett’s esophagus (BE). The microenvironmental niche, which includes the extracellular matrix (ECM), substantially influences cell phenotype. ECM harvested from normal porcine esophageal mucosa (eECM) was formulated as a mucoadhesive hydrogel, and shown to largely retain basement membrane and matrix-cell adhesion proteins. Dogs with BE were treated orally with eECM hydrogel and omeprazole (n = 6) or omeprazole alone (n = 2) for 30 days. eECM treatment resolved esophagitis, reverted metaplasia to a normal, squamous epithelium in four of six animals, and downregulated the pro-inflammatory tumor necrosis factor–α+ cell infiltrate compared to control animals. The metaplastic tissue in control animals (n = 2) did not regress. The results suggest that in vivo alteration of the microenvironment with a site-appropriate, mucoadhesive ECM hydrogel can mitigate the inflammatory and metaplastic response in a dog model of BE.