The host response to endotoxin-contaminated dermal matrix

Study on the preparation and properties of acellular matrix from the skin of silver carp (Hypophthalmichthys molitrix)

Acellular matrices are mainly composed of mammalian tissues, and aquatic tissues with lower biological risks and less religious restrictions are considered alternatives to mammalian tissues. The acellular fish skin matrix (AFSM) has been commercially available. Silver carp has the advantages of farmability, high yield and low price, but there are few studies on the silver carp acellular fish skin matrix (SC-AFSM). In this study, an acellular matrix with low DNA and endotoxin was prepared from the skin of silver carp. After treatment with trypsin/sodium dodecyl sulfate and Triton X-100 solutions, the DNA content in SC-AFSM reached 11.03 ± 0.85 ng/mg, and the endotoxin removal rate was 96.8%. The porosity of SC-AFSM was 79.64% ± 0.17%, which is favorable for cell infiltration and proliferation. The relative cell proliferation rate of SC-AFSM extract was 117.79% ± 15.26%. The wound healing experiment showed that SC-AFSM had no adverse acute pro-inflammatory response, which had a similar effect as commercial products in promoting tissue repair. Therefore, SC-AFSM has great application potential in biomaterials.

Biodegradable and Non-Biodegradable Biomaterials and Their Effect on Cell Differentiation

Biomaterials for tissue scaffolds are key components in modern tissue engineering and regenerative medicine. Targeted reconstructive therapies require a proper choice of biomaterial and an adequate choice of cells to be seeded on it. The introduction of stem cells, and the transdifferentiation procedures, into regenerative medicine opened a new era and created new challenges for modern biomaterials. They must not only fulfill the mechanical functions of a scaffold for implanted cells and represent the expected mechanical strength of the artificial tissue, but furthermore, they should also assure their survival and, if possible, affect their desired way of differentiation. This paper aims to review how modern biomaterials, including synthetic (i.e., polylactic acid, polyurethane, polyvinyl alcohol, polyethylene terephthalate, ceramics) and natural (i.e., silk fibroin, decellularized scaffolds), both non-biodegradable and biodegradable, could influence (tissue) stem cells fate, regulate and direct their differentiation into desired target somatic cells.

Comparison of outcomes of ventral hernia repair using different meshes: a systematic review and network meta-analysis

PURPOSE

We conducted a network meta-analysis to evaluate potential differences in patient outcomes when different meshes, especially biological meshes, were used for ventral hernia repair.

METHODS

PubMed, Embase, Cochrane Library, and Clinical Trials.gov databases were searched for studies comparing biological meshes with biological or synthetic meshes for ventral hernia repair. The outcomes were hernia recurrence rate, surgical site infection, and seroma. We performed a two-step network meta-analysis to investigate the outcomes of several biological meshes: non-cross-linked human acellular dermal matrix (NCHADM), non-cross-linked porcine ADM (NCPADM), non-cross-linked bovine ADM (NCBADM), cross-linked porcine ADM (CPADM), and porcine small intestinal submucosa (PSIS).

RESULTS

From 6304 publications, 23 studies involving 2603 patients were finally included. We found no differences between meshes in recurrence at 1-year follow-up and in surgical site infection rate. NCBADM was associated with the lowest recurrence rate and the lowest surgical site infection rate. NCHADM implantation was associated with the lowest rate of seroma. PSIS was associated with a higher risk of seroma than NCHADM (pooled risk ratio 3.89, 95% confidence interval 1.13-13.39) and NCPADM (RR 3.42, 95% CI 1.29-9.06).

CONCLUSIONS

Our network meta-analysis found no differences in recurrence rate or surgical site infection among different biological meshes. The incidence of postoperative seroma was higher with PSIS than with acellular dermal matrices. We observed large heterogeneity in the studies of ventral hernia repair using biological meshes, and, therefore, well-designed randomized clinical trials are needed.

Decellularized Avian Cartilage, a Promising Alternative for Human Cartilage Tissue Regeneration

Articular cartilage defects, and subsequent degeneration, are prevalent and account for the poor quality of life of most elderly persons; they are also one of the main predisposing factors to osteoarthritis. Articular cartilage is an avascular tissue and, thus, has limited capacity for healing and self-repair. Damage to the articular cartilage by trauma or pathological causes is irreversible. Many approaches to repair cartilage have been attempted with some potential; however, there is no consensus on any ideal therapy. Tissue engineering holds promise as an approach to regenerate damaged cartilage. Since cell adhesion is a critical step in tissue engineering, providing a 3D microenvironment that recapitulates the cartilage tissue is vital to inducing cartilage regeneration. Decellularized materials have emerged as promising scaffolds for tissue engineering, since this procedure produces scaffolds from native tissues that possess structural and chemical natures that are mimetic of the extracellular matrix (ECM) of the native tissue. In this work, we present, for the first time, a study of decellularized scaffolds, produced from avian articular cartilage (extracted from Gallus Gallus domesticus), reseeded with human chondrocytes, and we demonstrate for the first time that human chondrocytes survived, proliferated and interacted with the scaffolds. Morphological studies of the decellularized scaffolds revealed an interconnected, porous architecture, ideal for cell growth. Mechanical characterization showed that the decellularized scaffolds registered stiffness comparable to the native cartilage tissues. Cell growth inhibition and immunocytochemical analyses showed that the decellularized scaffolds are suitable for cartilage regeneration.

The Antimicrobial Effectiveness and Cytotoxicity of the Antibiotic-Loaded Chitosan: ECM Scaffolds

Background: The development of multifunctional wound dressings with the ability to control hemostasis, limit infection and promote rapid wound healing and constructive tissue remodeling has been a challenge for many years. In view of these challenges, a hybrid scaffold platform was developed that combined two different extracellular matrices (ECM): ECM from decellularized mammalian tissue and ECM (chitosan) from crustaceans. Both types of ECM have well established clinical benefits that support and promote wound healing and control hemostasis. This scaffold platform could also be augmented with antibiotics to provide bactericidal activity directly to the wound site. Methods: Four different scaffold formulations were developed containing chitosan supplemented with either 20% or 50% urinary bladder matrix (UBM) hydrogel or 1% (w/v) or 10% (w/v) UBM–ECM particulates. 100% chitosan scaffolds were used as controls. The scaffolds were augmented with either minocycline or rifampicin. Escherichia Coli and Staphylococcus Aureus were used to assesses antimicrobial efficacy and duration of activity, while neutral red uptake assays were performed to establish direct and indirect cytotoxicity. Results: Results showed that scaffold handling properties, scaffold integrity over time and the efficacy and release rate of loaded antibiotics could be modified by altering scaffold composition. Moreover, antibiotics were easily released from the scaffold and could remain effective for up to 24 h by modifying the scaffold composition. Variable results with cytotoxicity testing show that further work is required to optimize the scaffold formulations but these proof of principle experiments suggest that these scaffolds have potential as bioactive wound dressings.

A biological study establishing the endotoxin limit for osteoblast and adipocyte differentiation of human mesenchymal stem cells

INTRODUCTION

Multipotent mesenchymal stem cells (MSCs) are widespread in adult organisms and are implicated in tissue maintenance and repair, regulation of hematopoiesis, and immunologic responses. Human (h)MSCs have applications in tissue engineering, cell-based therapy, and medical devices but it is unclear how they respond to unfavorable conditions, such as hypoxia or inflammation after transplantation in vivo. Although endotoxin testing is required for evaluating the quality and safety of transplanted MSCs, no reports on their dose response to endotoxins are available to establish the limits for in vitro MSC culture systems. In the present study, we aimed to accurately quantify the risk of endotoxin contamination in cell culture systems to establish an acceptable endotoxin limit for the differentiation of hMSC osteoblasts and adipocytes.

METHODS

Three types of bone marrow-derived hMSCs (hMSC-1: 21-year-old, M/B; hMSC-2: 36-year-old, M/B; hMSC-3: 43-year-old, M/C) and adipose-derived stem cells (ADSCs; StemPro Human) were cultured in osteogenic or adipogenic differentiation media, respectively, from commercial kits, containing various concentrations of endotoxin (0.01-100 ng/ml). The degree of adipocyte and osteoblast differentiation was estimated by fluorescent staining of lipid droplets and hydroxyapatite, respectively. To clarify the molecular mechanism underlying the effect of endotoxin on hMSC differentiation, cellular proteins were extracted from cultured cells and subjected to liquid chromatograph-tandem mass spectrometry shotgun proteomics analysis.

RESULTS

Although endotoxin did not effect the adipocyte differentiation of hMSCs, osteoblast differentiation was enhanced by various endotoxin concentrations: over 1 ng/ml, for hMSC-1; 10 ng/ml, for hMSC-2; and 100 ng/ml, for hMSC-3. Proteomic analysis of hMSC-1 cells revealed up-regulation of many proteins related to bone formation. These results suggested that endotoxin enhances the osteoblast differentiation of MSCs depending on the cell type.

CONCLUSIONS

Since endotoxins can affect various cellular functions, an endotoxin limit should be established for in vitro MSC cultures. Its no-observed-adverse-effect level was 0.1 ng/ml based on the effect on the hMSC osteoblast differentiation, but it may not necessarily be the limit for ADSCs.

Effect of Source Animal Age upon Macrophage Response to Extracellular Matrix Biomaterials

Extracellular matrix biomaterials have been shown to promote constructive remodeling in many preclinical and clinical applications. This response has been associated with the promotion of a timely switch from pro-inflammatory (M1) to anti-inflammatory (M2) macrophages. A previous study has shown that this beneficial response is lost when these biomaterials are derived from aged animals. This study examined the impact of small intestine submucosa (SIS) derived from 12, 26 and 52 week old pigs on the phenotype and function of bone marrow macrophages derived either from 2 or 18 month old mice. Results showed that 52 week old SIS promoted less iNOS in 2 month macrophages and Fizz1 expression in 2 and 18 month compared to 12 week SIS. Pro-inflammatory cytokine exposure to 52 week SIS-treated macrophages resulted in higher iNOS in 18 month macrophages and reduced MHC-II expression in 2 month macrophages, as well as reduced nitric oxide production in comparison to 12 week SIS. These results indicate that ECM derived from aged animals promotes an altered macrophage phenotype compared to young controls. This suggests that sourcing of ECM from young donors is important to preserve constructive remodeling outcomes of ECM biomaterials. Alteration of macrophage phenotype by aged ECM also raises the hypothesis that alterations in aged ECM may play a role in immune dysfunction in aged individuals.

A biological study establishing the endotoxin limit for in vitro proliferation of human mesenchymal stem cells

INTRODUCTION

Multipotent mesenchymal stem cells (MSCs) are widespread in adult organisms and are implicated in tissue maintenance and repair, regulation of hematopoiesis, and immunologic responses. Human (h)MSCs have applications in tissue engineering, cell-based therapy, and medical devices but it is unclear how they respond to unfavorable conditions such as hypoxia or inflammation after in vivo transplantation. Although endotoxin testing is a requirement for evaluating the quality and safety of transplanted MSCs, there have been no reports on the dose response to endotoxins to establish limits for in vitro MSC culture systems. The present study aimed to accurately quantify the risk of endotoxin contamination in cell culture systems in order to establish the acceptable endotoxin limit for hMSC proliferation.

METHODS

Three types of bone marrow-derived hMSC (hMSC-1: 21 years, M/B; hMSC-2: 36 years, M/B; hMSC-3: 43 years, M/C) and adipose-derived stem cells (ADSCs; StemPro Human) were cultured in medium from commercial kits containing various concentrations of endotoxin (0.1-1000 ng/ml). The proliferative capacity of cells was estimated by cell counts using a hemocytometer. To clarify the molecular mechanism underlying the effect of endotoxin on hMSCs proliferation, cellular proteins were extracted from cultured cells and subjected to liquid chromatograph-tandem mass spectrometry shotgun proteomics analysis. The expression of Cu/Zn-type superoxide dismutase (SOD1) and Fe/Mn-type superoxide dismutase (SOD2) induced in hMSCs by endotoxin stimulation were evaluated by enzyme-linked immunosorbent assay (ELISA), and the effect of SOD2 on hMSC proliferation was also estimated.

RESULTS

Although there was no change in cell morphology during the culture period, proliferative capacity increased with endotoxin concentration to over 0.1 ng/ml for ADSCs, 1 ng/ml for hMSC-1, and 100 ng/ml for hMSC-2; hMSC-3 proliferation was unaffected by the presence of endotoxin. A proteomic analysis of hMSC-1 revealed that various proteins related to the cell cycle, apoptosis, and host defense against infection were altered by endotoxin stimulation, whereas SOD2 expression was significantly and consistently upregulated during the culture period. The latter was also confirmed by ELISA. Moreover, recombinant SOD2 increased proliferative capacity in hMSC-1 cells in a manner similar to endotoxin. These results suggest that endotoxin protects MSCs from oxidative stress via upregulation of SOD2 to improve cell survival.

CONCLUSIONS

Since endotoxins can affect various cellular functions, an endotoxin limit should be set for in vitro MSC cultures. The lowest observed adverse effect level was determined to be 0.1 ng/ml based on the effect on MSC proliferation.

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 (M_ECM) 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 M_ECM 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.

The host response to naturally-derived extracellular matrix biomaterials

Biomaterials based on natural materials including decellularized tissues and tissue-derived hydrogels are becoming more widely used for clinical applications. Because of their native composition and structure, these biomaterials induce a distinct form of the foreign body response that differs from that of non-native biomaterials. Differences include direct interactions with cells via preserved moieties as well as the ability to undergo remodeling. Moreover, these biomaterials could elicit adaptive immune responses due to the presence of modified native molecules. Therefore, these biomaterials present unique challenges in terms of understanding the progression of the foreign body response. This review covers this response to natural materials including natural polymers, decellularized tissues, cell-derived matrix, tissue derived hydrogels, and biohybrid materials. With the expansion of the fields of regenerative medicine and tissue engineering, the current repertoire of biomaterials has also expanded and requires continuous investigation of the responses they elicit.

A Porcine Urinary Bladder Matrix Does Not Recapitulate the Spatiotemporal Macrophage Response of Muscle Regeneration after Volumetric Muscle Loss Injury

Volumetric muscle loss (VML) results in irrecoverable loss of muscle tissue making its repair challenging. VML repair with acellular extracellular matrix (ECM) scaffolds devoid of exogenous cells has shown improved muscle function, but limited de novo muscle fiber regeneration. On the other hand, studies using minced autologous and free autologous muscle grafts have reported appreciable muscle regeneration. This raises the fundamental question whether an acellular ECM scaffold can orchestrate the spatiotemporal cellular events necessary for appreciable muscle fiber regeneration. This study compares the macrophage and angiogenic responses including the remodeling outcomes of a commercially available porcine urinary bladder matrix, MatriStem™, and autologous muscle grafts. The early heightened and protracted M1 response of the scaffold indicates that the scaffold does not recapitulate the spatiotemporal macrophage response of the autograft tissue. Additionally, the scaffold only supports limited de novo muscle fiber formation and regressing vessel density. Furthermore, scaffold remodeling is accompanied by increased presence of transforming growth factor and α-smooth muscle actin, which is consistent with remodeling of the scaffold into a fibrotic scar-like tissue. The limited muscle formation and scaffold-mediated fibrosis noted in this study corroborates the findings of recent studies that investigated acellular ECM scaffolds (devoid of myogenic cells) for VML repair. Taken together, acellular ECM scaffolds when used for VML repair will likely remodel into a fibrotic scar-like tissue and support limited de novo muscle fiber regeneration primarily in the proximity of the injured musculature. This is a work of the US Government and is not subject to copyright protection in the USA. Foreign copyrights may apply. Published by S. Karger AG, Basel.

Emerging Implications for Extracellular Matrix-Based Technologies in Vascularized Composite Allotransplantation

Despite recent progress in vascularized composite allotransplantation (VCA), limitations including complex, high dose immunosuppression regimens, lifelong risk of toxicity from immunosuppressants, acute and most critically chronic graft rejection, and suboptimal nerve regeneration remain particularly challenging obstacles restricting clinical progress. When properly configured, customized, and implemented, biomaterials derived from the extracellular matrix (ECM) retain bioactive molecules and immunomodulatory properties that can promote stem cell migration, proliferation and differentiation, and constructive functional tissue remodeling. The present paper reviews the emerging implications of ECM-based technologies in VCA, including local immunomodulation, tissue repair, nerve regeneration, minimally invasive graft targeted drug delivery, stem cell transplantation, and other donor graft manipulation.

Extracellular matrix-based biomaterial scaffolds and the host response

Extracellular matrix (ECM) collectively represents a class of naturally derived proteinaceous biomaterials purified from harvested organs and tissues with increasing scientific focus and utility in tissue engineering and repair. This interest stems predominantly from the largely unproven concept that processed ECM biomaterials as natural tissue-derived matrices better integrate with host tissue than purely synthetic biomaterials. Nearly every tissue type has been decellularized and processed for re-use as tissue-derived ECM protein implants and scaffolds. To date, however, little consensus exists for defining ECM compositions or sources that best constitute decellularized biomaterials that might better heal, integrate with host tissues and avoid the foreign body response (FBR). Metrics used to assess ECM performance in biomaterial implants are arbitrary and contextually specific by convention. Few comparisons for in vivo host responses to ECM implants from different sources are published. This review discusses current ECM-derived biomaterials characterization methods including relationships between ECM material compositions from different sources, properties and host tissue response as implants. Relevant preclinical in vivo models are compared along with their associated advantages and limitations, and the current state of various metrics used to define material integration and biocompatibility are discussed. Commonly applied applications of these ECM-derived biomaterials as stand-alone implanted matrices and devices are compared with respect to host tissue responses.

Immunomodulatory polymeric scaffold enhances extracellular matrix production in cell co-cultures under dynamic mechanical stimulation

Despite the importance of immune cells in regulating the wound healing process following injury, there are few examples of synthetic biomaterials that have the capacity to push the body's immune cells toward pro-regeneration phenotypes, and fewer still that are designed with the intention of achieving this immunomodulatory character. While monocytes and their derived macrophages have been recognized as important contributors to tissue remodeling in vivo, this is primarily believed to be due to their ability to regulate other cell types. The ability of monocytes and macrophages to generate tissue products themselves, however, is currently not well appreciated within the field of tissue regeneration. Furthermore, while monocytes/macrophages are found in remodeling tissue that is subjected to mechanical loading, the effect this biomechanical strain on monocytes/macrophages and their ability to regulate tissue-specific cellular activity has not been understood due to the complexity of the many factors involved in the in vivo setting, hence necessitating the use of controlled in vitro culture platforms to investigate this phenomenon. In this study, human monocytes were co-cultured with human coronary artery smooth muscle cells (VSMCs) on a tubular (3mm ID) degradable polyurethane scaffold, with a unique combination of non-ionic polar, hydrophobic and ionic chemistry (D-PHI). The goal was to determine if such a synthetic matrix could be used in a co-culture system along with dynamic biomechanical stimulus (10% circumferential strain, 1Hz) conditions in order to direct monocytes to enhance tissue generation, and to better comprehend the different ways in which monocytes/macrophages may contribute to new tissue production. Mechanical strain and monocyte co-culture had a complementary and non-mitigating effect on VSMC growth. Co-culture samples demonstrated increased deposition of sulphated glycosaminoglycans (GAGs) and elastin, as well as increases in the release of FGF-2, a growth factor that can stimulate VSMC growth, while dynamic culture supported increases in collagen I and III as well as increased mechanical properties (elastic modulus, tensile strength) vs. static controls. Macrophage polarization toward an M1 state was not promoted by the biomaterial or culture conditions tested. Monocytes/macrophages cultured on D-PHI were also shown to produce vascular extracellular matrix components, including collagen I, collagen III, elastin, and GAGs. This study highlights the use of synthetic biomaterials having immunomodulatory character in order to promote cell and tissue growth when used in tissue engineering strategies, and identifies ECM deposition by monocytes/macrophages as an unexpected source of this new tissue.

STATEMENT OF SIGNIFICANCE

The ability of biomaterials to regulate macrophage activation towards a wound healing phenotype has recently been shown to support positive tissue regeneration. However, the ability of immunomodulatory biomaterials to harness monocyte/macrophage activity to support tissue engineering strategies in vitro holds enormous potential that has yet to be investigated. This study used a monocyte co-culture on a degradable polyurethane (D-PHI) to regulate the response of VSMCs in combination with biomechanical strain in a vascular tissue engineering context. Results demonstrate that immunomodulatory biomaterials, such as D-PHI, that support a desirable macrophage activation state can be combined with biomechanical strain to augment vascular tissue production in vitro, in part due to the novel and unexpected contribution of monocytes/macrophages themselves producing vascular ECM proteins.

Biomaterials for pelvic floor reconstructive surgery: how can we do better?

Stress urinary incontinence (SUI) and pelvic organ prolapse (POP) are major health issues that detrimentally impact the quality of life of millions of women worldwide. Surgical repair is an effective and durable treatment for both conditions. Over the past two decades there has been a trend to enforce or reinforce repairs with synthetic and biological materials. The determinants of surgical outcome are many, encompassing the physical and mechanical properties of the material used, and individual immune responses, as well surgical and constitutional factors. Of the current biomaterials in use none represents an ideal. Biomaterials that induce limited inflammatory response followed by constructive remodelling appear to have more long term success than biomaterials that induce chronic inflammation, fibrosis and encapsulation. In this review we draw upon published animal and human studies to characterize the changes biomaterials undergo after implantation and the typical host responses, placing these in the context of clinical outcomes.

Biologic scaffolds for regenerative medicine: mechanisms of in vivo remodeling

Successful regenerative medicine strategies for functional tissue reconstruction include the in situ placement of acellular materials composed of the extracellular matrix (ECM) or individual components of the ECM. The composition and ultrastructure of these materials vary depending on multiple factors including the tissue source and species from which the materials are harvested, the methods of manufacture, the efficiency of decellularization, post-processing modifications such as chemical cross-linking or solubilization, and the methods of terminal sterilization. Appropriately configured materials have the ability to modulate different stages of the healing response by inducing a shift from a process of inflammation and scar tissue formation to one of constructive remodeling and functional tissue restoration. The events that facilitate such a dramatic change during the biomaterial-host interaction are complex and necessarily involve both the immune system and mechanisms of stem cell recruitment, growth, and differentiation. The present manuscript reviews the composition of biologic scaffolds, the methods and recommendations for manufacture, the mechanisms of the biomaterial-host interaction, and the clinical application of this regenerative medicine approach.

A perspective on the clinical translation of scaffolds for tissue engineering

Scaffolds have been broadly applied within tissue engineering and regenerative medicine to regenerate, replace, or augment diseased or damaged tissue. For a scaffold to perform optimally, several design considerations must be addressed, with an eye toward the eventual form, function, and tissue site. The chemical and mechanical properties of the scaffold must be tuned to optimize the interaction with cells and surrounding tissues. For complex tissue engineering, mass transport limitations, vascularization, and host tissue integration are important considerations. As the tissue architecture to be replaced becomes more complex and hierarchical, scaffold design must also match this complexity to recapitulate a functioning tissue. We outline these design constraints and highlight creative and emerging strategies to overcome limitations and modulate scaffold properties for optimal regeneration. We also highlight some of the most advanced strategies that have seen clinical application and discuss the hurdles that must be overcome for clinical use and commercialization of tissue engineering technologies. Finally, we provide a perspective on the future of scaffolds as a functional contributor to advancing tissue engineering and regenerative medicine.

Monocyte/macrophage cytokine activity regulates vascular smooth muscle cell function within a degradable polyurethane scaffold

Tissue engineering strategies rely on the ability to promote cell proliferation and migration into porous biomaterial constructs, as well as to support specific phenotypic states of the cells in vitro. The present study investigated the use of released factors from monocytes and their derived macrophages (MDM) and the mechanism by which they regulate vascular smooth muscle cell (VSMC) response in a VSMC-monocyte co-culture system within a porous degradable polyurethane (D-PHI) scaffold. VSMCs cultured in monocyte/MDM-conditioned medium (MCM), generated from the culture of monocytes/MDM on D-PHI scaffolds for up to 28 days, similarly affected VSMC contractile marker expression, growth and three-dimensional migration when compared to direct VSMC-monocyte co-culture. Monocyte chemotactic protein-1 (MCP-1) and interleukin-6 (IL-6) were identified as two cytokines present in MCM, at concentrations that have previously been shown to influence VSMC phenotype. VSMCs cultured alone on D-PHI scaffolds and exposed to MCP-1 (5 ng ml(-1)) or IL-6 (1 ng ml(-1)) for 7 days experienced a suppression in contractile marker expression (with MCP-1 or IL-6) and increased growth (with MCP-1) compared to no cytokine medium supplementation. These effects were also observed in VSMC-monocyte co-culture on D-PHI. Neutralization of IL-6, but not MCP-1, was subsequently shown to decrease VSMC growth and enhance calponin expression for VSMC-monocyte co-cultures on D-PHI scaffolds for 7 days, implying that IL-6 mediates VSMC response in monocyte-VSMC co-cultures. This study highlights the use of monocytes and their derived macrophages in conjunction with immunomodulatory biomaterials, such as D-PHI, as agents for regulating VSMC response, and demonstrates the importance of monocyte/MDM-released factors, such as IL-6 in particular, in this process.

Intracellular signaling mechanisms associated with CD47 modified surfaces

We have previously established that recombinant CD47 can ameliorate the inflammatory response to synthetic polymeric surfaces. Here, we begin to profile, at the transcriptional, translational and cell signaling level, the inflammatory cell response when blood interacts with CD47 modified polyvinyl chloride (PVC) (CD47-PVC). We used qPCR arrays to compare transcriptional changes between human whole blood exposed to CD47-PVC or PVC. Transcription of IL1F5, IL1F10, IL17F, CCL3, CCL8, CCL28, CXCL12, and CXCL13 was upregulated in blood exposed to PVC, compared to CD47-PVC. The increase in CCL3 and CCL8 transcription correlated with an increase in the chemokines' presence in the plasma. Exposure of blood to CD47-PVC resulted in an increase, compared to PVC, in transcription of CCL2, CCL4, CCL20, CXCL1, TGFβ3, GDF3, GDF10, CD40LG, and TNFSF10. CD47-PVC exposure resulted in an increase of the following matrix metalloproteinase related genes: MMP1, MMP7, MMP13, and MMP16. Phosflow cytometry, and assays examining transcription factor binding, cell attachment, and genome-wide chromatin association indicated that members of the JAK-STAT signaling pathway, particularly JAK2 and STAT5, mediate inflammatory cell interactions with CD47-PVC. Our data demonstrate that differential molecular responses to CD47 involve downregulation of cytokines, upregulation of MMPs, and JAK/STAT signaling mechanisms.

Preparation and characterization of a biologic scaffold from esophageal mucosa

Biologic scaffolds composed of extracellular matrix (ECM) are commonly used to facilitate a constructive remodeling response in several types of tissue, including the esophagus. Surgical manipulation of the esophagus is often complicated by stricture, but preclinical and clinical studies have shown that the use of an ECM scaffold can mitigate stricture and promote a constructive outcome after resection of full circumference esophageal mucosa. Recognizing the potential benefits of ECM derived from homologous tissue (i.e., site-specific ECM), the objective of the present study was to prepare, characterize, and assess the in-vivo remodeling properties of ECM from porcine esophageal mucosa. The developed protocol for esophageal ECM preparation is compliant with previously established criteria of decellularization and results in a scaffold that maintains important biologic components and an ultrastructure consistent with a basement membrane complex. Perivascular stem cells remained viable when seeded upon the esophageal ECM scaffold in-vitro, and the in-vivo host response showed a pattern of constructive remodeling when implanted in soft tissue.

Functional characterization of detergent-decellularized equine tendon extracellular matrix for tissue engineering applications

Natural extracellular matrix provides a number of distinct advantages for engineering replacement orthopedic tissue due to its intrinsic functional properties. The goal of this study was to optimize a biologically derived scaffold for tendon tissue engineering using equine flexor digitorum superficialis tendons. We investigated changes in scaffold composition and ultrastructure in response to several mechanical, detergent and enzymatic decellularization protocols using microscopic techniques and a panel of biochemical assays to evaluate total protein, collagen, glycosaminoglycan, and deoxyribonucleic acid content. Biocompatibility was also assessed with static mesenchymal stem cell (MSC) culture. Implementation of a combination of freeze/thaw cycles, incubation in 2% sodium dodecyl sulfate (SDS), trypsinization, treatment with DNase-I, and ethanol sterilization produced a non-cytotoxic biomaterial free of appreciable residual cellular debris with no significant modification of biomechanical properties. These decellularized tendon scaffolds (DTS) are suitable for complex tissue engineering applications, as they provide a clean slate for cell culture while maintaining native three-dimensional architecture.