Macrophage phenotype in response to ECM bioscaffolds.

Macrophage presence and phenotype are critical determinants of the healing response following injury. Downregulation of the pro-inflammatory macrophage phenotype has been associated with the therapeutic use of bioscaffolds composed of extracellular matrix (ECM), but phenotypic characterization of macrophages has typically been limited to small number of non-specific cell surface markers or expressed proteins. The present study determined the response of both primary murine bone marrow derived macrophages (BMDM) and a transformed human mononuclear cell line (THP-1 cells) to degradation products of two different, commonly used ECM bioscaffolds; urinary bladder matrix (UBM-ECM) and small intestinal submucosa (SIS-ECM). Quantified cell responses included gene expression, protein expression, commonly used cell surface markers, and functional assays. Results showed that the phenotype elicited by ECM exposure (MECM) is distinct from both the classically activated IFNγ+LPS phenotype and the alternatively activated IL-4 phenotype. Furthermore, the BMDM and THP-1 macrophages responded differently to identical stimuli, and UBM-ECM and SIS-ECM bioscaffolds induced similar, yet distinct phenotypic profiles. The results of this study not only characterized an MECM phenotype that has anti-inflammatory traits but also showed the risks and challenges of making conclusions about the role of macrophage mediated events without consideration of the source of macrophages and the limitations of individual cell markers.

BPIFA1 regulates lung neutrophil recruitment and interferon signaling during acute inflammation.

Bpifa1 (BPI fold-containing group A member 1) is an airway host-protective protein with immunomodulatory properties that binds to LPS and is regulated by infectious and inflammatory signals. Differential expression of Bpifa1 has been widely reported in lung disease, yet the biological significance of this observation is unclear. We sought to understand the role of Bpifa1 fluctuations in modulating lung inflammation. We treated wild-type (WT) and Bpifa1-/- mice with intranasal LPS and performed immunological and transcriptomic analyses of lung tissue to determine the immune effects of Bpifa1 deficiency. We show that neutrophil (polymorphonuclear cells, PMNs) lung recruitment and transmigration to the airways in response to LPS is impaired in Bpifa1-/- mice. Transcriptomic analysis revealed a signature of 379 genes that differentiated Bpifa1-/- from WT mice. During acute lung inflammation, the most downregulated genes in Bpifa1-/- mice were Cxcl9 and Cxcl10. Bpifa1-/- mice had lower bronchoalveolar lavage concentrations of C-X-C motif chemokine ligand 10 (Cxcl10) and Cxcl9, interferon-inducible PMN chemokines. This was consistent with lower expression of IFNγ, IFNλ, downstream IFN-stimulated genes, and IFN-regulatory factors, which are important for the innate immune response. Administration of Cxcl10 before LPS treatment restored the inflammatory response in Bpifa1-/- mice. Our results identify a novel role for Bpifa1 in the regulation of Cxcl10-mediated PMN recruitment to the lungs via IFNγ and -λ signaling during acute inflammation.

Modified mesenchymal stem cells using miRNA transduction alter lung injury in a bleomycin model.

Although different preclinical models have demonstrated a favorable role for bone marrow-derived mesenchymal stem cells (B-MSC) in preventing fibrosis, this protective effect is not observed with late administration of these cells, when fibrotic changes are consolidated. We sought to investigate whether the late administration of B-MSCs overexpressing microRNAs (miRNAs) let-7d (antifibrotic) or miR-154 (profibrotic) could alter lung fibrosis in a murine bleomycin model. Using lentiviral vectors, we transduced miRNAs (let-7d or miR-154) or a control sequence into human B-MSCs. Overexpression of let-7d or miR-154 was associated with changes in the mesenchymal properties of B-MSCs and in their cytokine expression. Modified B-MSCs were intravenously administered to mice at day 7 after bleomycin instillation, and the mice were euthanized at day 14 Bleomycin-injured animals that were treated with let-7d cells were found to recover quicker from the initial weight loss compared with the other treatment groups. Interestingly, animals treated with miR-154 cells had the lowest survival rate. Although a slight reduction in collagen mRNA levels was observed in lung tissue from let-7d mice, no significant differences were observed in Ashcroft score and OH-proline. However, the distinctive expression in cytokines and CD45-positive cells in the lung suggests that the differential effects observed in both miRNA mice groups were related to an effect on the immunomodulation function. Our results establish the use of miRNA-modified mesenchymal stem cells as a potential future research in lung fibrosis.

Integrated Genomics Reveals Convergent Transcriptomic Networks Underlying Chronic Obstructive Pulmonary Disease and Idiopathic Pulmonary Fibrosis.

RATIONALE: Despite shared environmental exposures, idiopathic pulmonary fibrosis (IPF) and chronic obstructive pulmonary disease are usually studied in isolation, and the presence of shared molecular mechanisms is unknown. OBJECTIVES: We applied an integrative genomic approach to identify convergent transcriptomic pathways in emphysema and IPF. METHODS: We defined the transcriptional repertoire of chronic obstructive pulmonary disease, IPF, or normal histology lungs using RNA-seq (n = 87). MEASUREMENTS AND MAIN RESULTS: Genes increased in both emphysema and IPF relative to control were enriched for the p53/hypoxia pathway, a finding confirmed in an independent cohort using both gene expression arrays and the nCounter Analysis System (n = 193). Immunohistochemistry confirmed overexpression of HIF1A, MDM2, and NFKBIB members of this pathway in tissues from patients with emphysema or IPF. Using reads aligned across splice junctions, we determined that alternative splicing of p53/hypoxia pathway-associated molecules NUMB and PDGFA occurred more frequently in IPF or emphysema compared with control and validated these findings by quantitative polymerase chain reaction and the nCounter Analysis System on an independent sample set (n = 193). Finally, by integrating parallel microRNA and mRNA-Seq data on the same samples, we identified MIR96 as a key novel regulatory hub in the p53/hypoxia gene-expression network and confirmed that modulation of MIR96 in vitro recapitulates the disease-associated gene-expression network. CONCLUSIONS: Our results suggest convergent transcriptional regulatory hubs in diseases as varied phenotypically as chronic obstructive pulmonary disease and IPF and suggest that these hubs may represent shared key responses of the lung to environmental stresses.

Aging mesenchymal stem cells fail to protect because of impaired migration and antiinflammatory response.

RATIONALE: Aging is characterized by functional impairment and reduced capacity to respond appropriately to environmental stimuli and injury. With age, there is an increase in the incidence and severity of chronic and acute lung diseases. However, the relationship between age and the lung's reduced ability to repair is far from established and necessitates further research in the field. OBJECTIVES: Little is currently known about age-related phenomena in mesenchymal stem cells (MSCs). On account of their ability to protect the endothelium and the alveolar epithelium through multiple paracrine mechanisms, we looked for adverse effects that aging might cause in MSC biology. Such age-related changes might partly account for the increased susceptibility of the aging lung to injury. MEASUREMENTS AND MAIN RESULTS: We demonstrated that old mice have more inflammation in response to acute lung injury. To investigate the causes, we compared the global gene expression of aged and young bone marrow-derived MSCs (B-MSCs). Our results revealed that the expression levels of inflammatory response genes depended on the age of the B-MSCs. We demonstrated that the age-dependent decrease in expression of several cytokine and chemokine receptors is important for the migration and activation of B-MSCs. Finally, we showed by adoptive transfer of aged B-MSCs to young endotoxemic mice that aged cells lacked the antiinflammatory protective effect of their young counterparts. CONCLUSIONS: Taken together, the decreased expression of cytokine and chemokine receptors in aged B-MSCs compromises their protective role by perturbing the potential of B-MSCs to become activated and mobilize to the site of injury.

Let-7d microRNA affects mesenchymal phenotypic properties of lung fibroblasts.

MicroRNAs are small noncoding RNAs that inhibit protein expression. We have previously shown that the inhibition of the microRNA let-7d in epithelial cells caused changes consistent with epithelial-to-mesenchymal transition (EMT) both in vitro and in vivo. The aim of this study was to determine whether the introduction of let-7d into fibroblasts alters their mesenchymal properties. Transfection of primary fibroblasts with let-7d caused a decrease in expression of the mesenchymal markers α-smooth muscle actin, N-cadherin, fibroblast-specific protein-1, and fibronectin, as well as an increase in the epithelial markers tight junction protein-1 and keratin 19. Phenotypic changes were also present, including a delay in wound healing, reduced motility, and proliferation of fibroblasts following transfection. In addition, we examined the effects of transfection on fibroblast responsiveness to TGF-ß, an important factor in many fibrotic processes such as lung fibrosis and found that let-7d transfection significantly attenuated high-mobility group-A2 protein induction by TGF-ß. Our results indicate that administration of the epithelial microRNA let-7d can significantly alter the phenotype of primary fibroblasts.

Novel modeling of combinatorial miRNA targeting identifies SNP with potential role in bone density.

MicroRNAs (miRNAs) are post-transcriptional regulators that bind to their target mRNAs through base complementarity. Predicting miRNA targets is a challenging task and various studies showed that existing algorithms suffer from high number of false predictions and low to moderate overlap in their predictions. Until recently, very few algorithms considered the dynamic nature of the interactions, including the effect of less specific interactions, the miRNA expression level, and the effect of combinatorial miRNA binding. Addressing these issues can result in a more accurate miRNA:mRNA modeling with many applications, including efficient miRNA-related SNP evaluation. We present a novel thermodynamic model based on the Fermi-Dirac equation that incorporates miRNA expression in the prediction of target occupancy and we show that it improves the performance of two popular single miRNA target finders. Modeling combinatorial miRNA targeting is a natural extension of this model. Two other algorithms show improved prediction efficiency when combinatorial binding models were considered. ComiR (Combinatorial miRNA targeting), a novel algorithm we developed, incorporates the improved predictions of the four target finders into a single probabilistic score using ensemble learning. Combining target scores of multiple miRNAs using ComiR improves predictions over the naïve method for target combination. ComiR scoring scheme can be used for identification of SNPs affecting miRNA binding. As proof of principle, ComiR identified rs17737058 as disruptive to the miR-488-5p:NCOA1 interaction, which we confirmed in vitro. We also found rs17737058 to be significantly associated with decreased bone mineral density (BMD) in two independent cohorts indicating that the miR-488-5p/NCOA1 regulatory axis is likely critical in maintaining BMD in women. With increasing availability of comprehensive high-throughput datasets from patients ComiR is expected to become an essential tool for miRNA-related studies.

Treatment with a Urinary Bladder Matrix Alters the Innate Host Response to Pneumonia Induced by Escherichia coli.

Escherichiacoli has become the prominent cause of nosocomial pneumonia in recent years. In the meantime, some strains of E. coli have developed resistance to commonly used antibacterial drugs. The urinary bladder matrix (UBM) is a biologically derived scaffold material that has been used to promote site-appropriate tissue remodeling in a variety of body systems, partially through the modulation of the innate immune response. In this study, we seek to determine UBM efficacy in preventing bacterial pneumonia in mouse lungs using the Gram-negative bacterial strain E. coli. Our results show that the UBM prevented bacterial biofilm formation in both abiotic and biotic conditions through experimentation on polystyrene plates and culture on the apical surface of differentiated airway epithelial cells. Intratracheal treatment with UBM led to host protection from E. coli-induced respiratory infection in a murine pneumonia model. Transcriptomic analysis revealed the involvement of the enhanced host immune response in UBM-treated mice. Additionally, UBM-treated macrophages had an increased iNOS expression and enhanced phagocytosis activity. Therefore, the protection against E. coli-induced infection and the antibacterial function observed by UBM is potentially through both the anti-biofilm activity and enhanced host immunity following UBM treatment. Taken together, our results support further investigation of UBM as an alternative treatment to attenuate bacterial-induced respiratory infection.

Type 2 immunity induced by bladder extracellular matrix enhances corneal wound healing.

The avascular nature of cornea tissue limits its regenerative potential, which may lead to incomplete healing and formation of scars when damaged. Here, we applied micro- and ultrafine porcine urinary bladder matrix (UBM) particulate to promote type 2 immune responses in cornea wounds. Results demonstrated that UBM particulate substantially reduced corneal haze formation as compared to the saline-treated group. Flow cytometry and gene expression analysis showed that UBM particulate suppressed the differentiation of corneal stromal cells into α-smooth muscle actin-positive (αSMA+) myofibroblasts. UBM treatments up-regulated interleukin-4 (IL-4) produced primarily by eosinophils in the wounded corneas and CD4+ T cells in draining lymph nodes, suggesting a cross-talk between local and peripheral immunity. Gata1-/- mice lacking eosinophils did not respond to UBM treatment and had impaired wound healing. In summary, stimulating type 2 immune responses in the wounded cornea can promote proregenerative environments that lead to improved wound healing for vision restoration.

The effect of normal, metaplastic, and neoplastic esophageal extracellular matrix upon macrophage activation.

INTRODUCTION: Macrophages are capable of extreme plasticity and their activation state has been strongly associated with solid tumor growth progression and regression. Although the macrophage response to extracellular matrix (ECM) isolated from normal tissue is reasonably well understood, there is a relative dearth of information regarding their response to ECM isolated from chronically inflamed tissues, pre-neoplastic tissues, and neoplastic tissues. Esophageal adenocarcinoma (EAC) is a type of neoplasia driven by chronic inflammation in the distal esophagus, and the length of the esophagus provides the opportunity to investigate macrophage behavior in the presence of ECM isolated from a range of disease states within the same organ. METHODS: Normal, metaplastic, and neoplastic ECM hydrogels were prepared from decellularized EAC tissue. The hydrogels were evaluated for their nanofibrous structure (SEM), biochemical profile (targeted and global proteomics), and direct effect upon macrophage (THP-1 cell) activation state (qPCR, ELISA, immunolabeling) and indirect effect upon epithelial cell (Het-1A) migration (Boyden chamber). RESULTS: Nanofibrous ECM hydrogels from the three tissue types could be formed, and normal and neoplastic ECM showed distinctive protein profiles by targeted and global mass spectroscopy. ECM proteins functionally related to cancer and tumorigenesis were identified in the neoplastic esophageal ECM including collagen alpha-1(VIII) chain (COL8A1), lumican, and elastin. Metaplastic and neoplastic esophageal ECM induce distinctive effects upon THP-1 macrophage signaling compared to normal esophageal ECM. These effects include activation of pro-inflammatory IFNγ and TNFα gene expression and anti-inflammatory IL1RN gene expression. Most notably, neoplastic ECM robustly increased macrophage TNFα protein expression. The secretome of macrophages pre-treated with metaplastic and neoplastic ECM increases the migration of normal esophageal epithelial cells, similar behavior to that shown by tumor cells. Metaplastic ECM shows similar but less pronounced effects than neoplastic ECM suggesting the abnormal signals also exist within the pre-cancerous state. CONCLUSION: A progressively diseased ECM, as exists within the esophagus exposed to chronic gastric reflux, can provide insights into novel biomarkers of early disease and identify potential therapeutic targets.

Solution Formulation and Rheology for Fabricating Extracellular Matrix-Derived Fibers Using Low-Voltage Electrospinning Patterning.

Composite formation and chemical cross-linking are common strategies in tuning the functionality and performance of biologically derived fibers fabricated by electrospinning. The modification to the initial polymeric solution changes the fiber-processing parameters and the associated fiber morphologies. Here, we investigated the gelatin solution formulation and how the addition of homogenized decellularized matrix particles (dCMps) can alter the processability of gelatin fibers produced by low-voltage electrospinning patterning. To produce water-insoluble fibers, the effect of a cross-linker addition was also separately investigated. In particular, we found that the electrospinnability of the solutions formulated with different concentrations of gelatin and dCMps and the morphology of the electrospun fibers were dependent on the rheological properties of the solutions. The solution dispersion rheology can be used as a useful indicator for guiding fiber processability and the fabrication strategy for patterning. The loss tangent associated with an oscillatory rheological test can be used to indicate the switch from an "extrusion-patterning" to a "drag-patterning" configuration. Fine-tuning of the cross-linking time can switch the thin fibrous film between a woven and a nonwoven structure. This study can be used as a guide to producing extracellular matrix fibers and films with specific microstructures suitable for tissue engineering applications.

Extracellular Matrix Degradation Products Downregulate Neoplastic Esophageal Cell Phenotype.

IMPACT STATEMENT: Extracellular matrix (ECM) biomaterials were used to treat esophageal cancer patients after cancer resection and promoted regrowth of normal mucosa without recurrence of cancer. The present study investigates the mechanisms by which these materials were successful to prevent the cancerous phenotype. ECM downregulated neoplastic esophageal cell function (proliferation, metabolism), but normal esophageal epithelial cells were unaffected in vitro, and suggests a molecular basis (downregulation of PI3K-Akt, cell cycle) for the promising clinical results. The therapeutic effect appeared to be enhanced using homologous esophageal ECM. This study suggests that ECM can be further investigated to treat cancer patients after resection or in combination with targeted therapy.

Solution fibre spinning technique for the fabrication of tuneable decellularised matrix-laden fibres and fibrous micromembranes.

Recreating tissue-specific microenvironments of the extracellular matrix (ECM) in vitro is of broad interest for the fields of tissue engineering and organ-on-a-chip. Here, we present biofunctional ECM protein fibres and suspended membranes, with tuneable biochemical, mechanical and topographical properties. This soft and entirely biologic membrane scaffold, formed by micro-nano-fibres using low voltage electrospinning, displays three unique characteristics for potential cell culture applications: high-content of key ECM proteins, single-layered mesh membrane, and flexibility for in situ integration into a range of device setups. Extracellular matrix (ECM) powder derived from urinary bladder, was used to fabricate the ECM-laden fibres and membranes. The highest ECM concentration in the dry protein fibre was 50 wt%, with the rest consisting of gelatin. Key ECM proteins, including collagen IV, laminin, and fibronectin, were shown to be preserved post the biofabrication process. The single fibre tensile Young's modulus can be tuned for over two orders of magnitude between ∼600 kPa and 50 MPa depending on the ECM content. Combining the fibre mesh printing with 3D printed or microfabricated structures, culture devices were constructed for endothelial layer formation, and a trans-membrane co-culture formed by glomerular cell types of podocytes and glomerular endothelial cells, demonstrating feasibility of the membrane culture. Our cell culture observation points to the importance of membrane mechanical property and re-modelling ability as a factor for soft membrane-based cell cultures. The ECM-laden fibres and membranes presented here would see potential applications in in vitro assays, and tailoring structure and biological functions of tissue engineering scaffolds. STATEMENT OF SIGNIFICANCE: Recreating tissue-specific microenvironments of the extracellular matrix (ECM) is of broad interest for the fields of tissue engineering and organ-on-a-chip. Both the biochemical and biophysical signatures of the engineered ECM interplay to affect cell response. Currently, there are limited biomaterials processing methods which allow to design ECM membrane properties flexibly and rapidly. Solvents and additives used in many existing processes also induced unwanted ECM protein degradation and toxic residues. This paper presents a solution fibre spinning technique, where careful selection of the solution combination led to well-preserved ECM proteins with tuneable composition. This technique also provides a highly versatile approach to fabricate ECM fibres and membranes, leading to designable fibre Young's modulus for over two orders of magnitude.

Injectable, porous, biohybrid hydrogels incorporating decellularized tissue components for soft tissue applications.

Biodegradable injectable hydrogels have been extensively studied and evaluated in various medical applications such as for bulking agents, drug delivery reservoirs, temporary barriers, adhesives, and cell delivery matrices. Where injectable hydrogels are intended to facilitate a healing response, it may be desirable to encourage rapid cellular infiltration into the hydrogel volume from the tissue surrounding the injection site. In this study, we developed a platform technique to rapidly form pores in a thermally responsive injectable hydrogel, poly(NIPAAm-co-VP-co-MAPLA) by using mannitol particles as porogens. In a rat hindlimb muscle injection model, hydrogels incorporating porosity had significantly accelerated cellular infiltration. To influence the inflammatory response to the injected hydrogel, enzymatically digested urinary bladder matrix (UBM) was mixed with the solubilized hydrogel. The presence of UBM was associated with greater polarization of the recruited macrophage population to the M2 phenotype, indicating a more constructive foreign body response. The hybrid hydrogel positively affected the wound healing outcomes of defects in rabbit adipose tissue with negligible inflammation and fibrosis, whereas scar formation and chronic inflammation were observed with autotransplantation and in saline injected groups. These results demonstrate the value of combining the effects of promoting cell infiltration and mediating the foreign body response for improved biomaterials options soft tissue defect filling applications. STATEMENT OF SIGNIFICANCE: Our objective was to develop a fabrication process to create porous injectable hydrogels incorporating decellularized tissue digest material. This new hydrogel material was expected to exhibit faster cellular infiltration and a greater extent of pro-M2 macrophage polarization compared to control groups not incorporating each of the functional components. Poly(NIPAAm-co-VP-co-MAPLA) was chosen as the representative thermoresponsive hydrogel, and mannitol particles and digested urinary bladder matrix (UBM) were selected as the porogen and the bioactive decellularized material components respectively. In rat hindlimb intramuscular injection models, this new hydrogel material induced more rapid cellular infiltration and a greater extent of M2 macrophage polarization compared to control groups not incorporating all of the functional components. The hybrid hydrogel positively affected the wound healing outcomes of defects in rabbit adipose tissue with negligible inflammation and fibrosis, whereas scar formation and chronic inflammation were observed with autotransplantation and in saline injected groups. The methodology of this report provides a straightforward and convenient mechanism to promote cell infiltration and mediate foreign body response in injectable hydrogels for soft tissue applications. We believe that the readership of Acta Biomaterialia will find the work of interest both for its specific results and general translatability of the findings.

An HDAC9-MALAT1-BRG1 complex mediates smooth muscle dysfunction in thoracic aortic aneurysm.

Thoracic aortic aneurysm (TAA) has been associated with mutations affecting members of the TGF-ß signaling pathway, or components and regulators of the vascular smooth muscle cell (VSMC) actomyosin cytoskeleton. Although both clinical groups present similar phenotypes, the existence of potential common mechanisms of pathogenesis remain obscure. Here we show that mutations affecting TGF-ß signaling and VSMC cytoskeleton both lead to the formation of a ternary complex comprising the histone deacetylase HDAC9, the chromatin-remodeling enzyme BRG1, and the long noncoding RNA MALAT1. The HDAC9-MALAT1-BRG1 complex binds chromatin and represses contractile protein gene expression in association with gain of histone H3-lysine 27 trimethylation modifications. Disruption of Malat1 or Hdac9 restores contractile protein expression, improves aortic mural architecture, and inhibits experimental aneurysm growth. Thus, we highlight a shared epigenetic pathway responsible for VSMC dysfunction in both forms of TAA, with potential therapeutic implication for other known HDAC9-associated vascular diseases.

The Influence of Extracellular RNA on Cell Behavior in Health, Disease and Regeneration.

PURPOSE OF REVIEW: An overview of the role of extracellular RNAs (exRNA) in the regulation of homeostasis, disease progression, and regeneration is provided herein. Several exRNAs have been identified as potential biomarkers for disease and disease progression. In addition, the potential of exRNAs as a therapeutic modality is discussed. RECENT FINDINGS: Fibrotic diseases of the lung, liver, and heart, among other organs share a number of identical exRNAs which play key roles in disease pathogenesis. Though regeneration is limited to only a few tissues in humans, small RNAs (e.g. microRNA) have been shown to be involved in the regenerative process of tissues such as liver and bone. The regulation of healing versus disease appears to be balanced by small RNAs. Because small RNAs are critical to health, they are being investigated as drug targets in multiple ongoing clinical trials. Preclinical studies suggest that promoting or blocking specific small RNAs can provide a novel therapeutic approach. SUMMARY: exRNA can be utilized for both detection and treatment of disease. Natural and synthetic RNA carriers are being investigated as delivery methods for small RNA molecules. Current and future investigations are likely to lead to expanded applications for exRNAs.

Extracellular Matrix Bioscaffolds as Immunomodulatory Biomaterials.

Suppression of the recipient immune response is a common component of tissue and organ transplantation strategies and has also been used as a method of mitigating the inflammatory and scar tissue response to many biomaterials. It is now recognized, however, that long-term functional tissue replacement not only benefits from an intact host immune response but also depends upon such a response. The present article reviews the limitations associated with the traditionally held view of avoiding the immune response, the ability of acellular biologic scaffold materials to modulate the host immune response and promote a functional tissue replacement outcome, and current strategies within the fields of tissue engineering and biomaterials to develop immune-responsive and immunoregulatory biomaterials.

Urinary bladder extracellular matrix hydrogels and matrix-bound vesicles differentially regulate central nervous system neuron viability and axon growth and branching.

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.

Matrix-Bound Nanovesicles Recapitulate Extracellular Matrix Effects on Macrophage Phenotype.

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.

Regenerative Medicine: lessons from Mother Nature.

Regenerative medicine strategies for the restoration of functional tissue have evolved from the concept of ex vivo creation of engineered tissue toward the broader concept of in vivo induction of functional tissue reconstruction. Multidisciplinary approaches are being investigated to achieve this goal using evolutionarily conserved principles of stem cell biology, developmental biology and immunology, current methods of engineering and medicine. This evolution from ex vivo tissue engineering to the manipulation of fundamental in vivo tenets of development and regeneration has the potential to capitalize upon the incredibly complex and only partially understood ability of cells to adapt, proliferate, self-organize and differentiate into functional tissue.