Mechanical strength vs. degradation of a biologically-derived surgical mesh over time in a rodent full thickness abdominal wall defect.

The use of synthetic surgical mesh materials has been shown to decrease the incidence of hernia recurrence, but can be associated with undesirable effects such as infection, chronic discomfort, and adhesion to viscera. Surgical meshes composed of extracellular matrix (i.e., biologically-derived mesh) are an alternative to synthetic meshes and can reduce some of these undesirable effects but are less frequently used due to greater cost and perceived inadequate strength as the mesh material degrades and is replaced by host tissue. The present study assessed the temporal association between mechanical properties and degradation of biologic mesh composed of urinary bladder matrix (UBM) in a rodent model of full thickness abdominal wall defect. Mesh degradation was evaluated for non-chemically crosslinked scaffolds with the use of (14)C-radiolabeled UBM. UBM biologic mesh was 50% degraded by 26 days and was completely degraded by 90 days. The mechanical properties of the UBM biologic mesh showed a rapid initial decrease in strength and modulus that was not proportionately associated with its degradation as measured by (14)C. The loss of strength and modulus was followed by a gradual increase in these values that was associated with the deposition of new, host derived connective tissue. The strength and modulus values were comparable to or greater than those of the native abdominal wall at all time points.

The effect of detergents on the basement membrane complex of a biologic scaffold material.

The basement membrane complex (BMC) is a critical component of the extracellular matrix (ECM) that supports and facilitates the growth of cells. This study investigates four detergents commonly used in the process of tissue decellularization and their effect upon the BMC. The BMC of porcine urinary bladder was subjected to 3% Triton-X 100, 8mM 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate (CHAPS), 4% sodium deoxycholate or 1% sodium dodecyl sulfate (SDS) for 24h. The BMC structure for each treatment group was assessed by immunolabeling, scanning electron microscopy (SEM) and second harmonic generation (SHG) imaging of the fiber network. The composition was assessed by quantification of dsDNA, glycosaminoglycans (GAG) and collagen content. The results showed that collagen fibers within samples treated with 1% SDS and 8mM CHAPS were denatured, and the ECM contained fewer GAG compared with samples treated with 3% Triton X-100 or 4% sodium deoxycholate. Human microvascular endothelial cells (HMEC) were seeded onto each BMC and cultured for 7 days. Cell-ECM interactions were investigated by immunolabeling for integrin ß-1, SEM imaging and semi-quantitative assessment of cellular infiltration, phenotype and confluence. HMEC cultured on a BMC treated with 3% Triton X-100 were more confluent and had a normal phenotype compared with HMEC cultured on a BMC treated with 4% sodium deoxycholate, 8mM CHAPS and 1% SDS. Both 8mM CHAPS and 1% SDS damaged the BMC to the extent that seeded HMEC were able to infiltrate the damaged sub-basement membrane tissue, showed decreased confluence and an atypical phenotype. The choice of detergents used for tissue decellularization can have a marked effect upon the integrity of the BMC of the resultant bioscaffold.

Fractionation of an ECM hydrogel into structural and soluble components reveals distinctive roles in regulating macrophage behavior.

Extracellular matrix (ECM) derived from mammalian tissues has been utilized to repair damaged or missing tissue and improve healing outcomes. More recently, processing of ECM into hydrogels has expanded the use of these materials to include platforms for 3-dimensional cell culture as well as injectable therapeutics that can be delivered by minimally invasive techniques and fill irregularly shaped cavities. At the cellular level, ECM hydrogels initiate a multifaceted host response that includes recruitment of endogenous stem/progenitor cells, regional angiogenesis, and modulation of the innate immune response. Unfortunately, little is known about the components of the hydrogel that drive these responses. We hypothesized that different components of ECM hydrogels could play distinctive roles in stem cell and macrophage behavior. Utilizing a well-characterized ECM hydrogel derived from urinary bladder matrix (UBM), we separated the soluble and structural components of UBM hydrogel and characterized their biological activity. Perivascular stem cells migrated toward and reduced their proliferation in response to both structural and soluble components of UBM hydrogel. Both components also altered macrophage behavior but with different fingerprints. Soluble components increased phagocytosis with an IL-1RA(high), TNFα(low), IL-1ß(low), uPA(low) secretion profile. Structural components decreased phagocytosis with a PGE2(high), PGF2α(high), TNFα(low), IL-1ß(low), uPA(low), MMP2(low), MMP9(low), secretion profile. The biologic activity of the soluble components was mediated by Notch and PI3K/Akt signaling, while the biologic activity of the structural components was mediated by integrins and MEK/ERK signaling. Collectively, these findings demonstrate that soluble and structural components of ECM hydrogels contribute to the host response but through different mechanisms.

Heparin-binding properties of human serum spreading factor.

Human serum spreading factor (SF) is a blood glycoprotein that promotes attachment and spreading and influences growth, migration, and differentiation of a variety of animal cells in culture. SF purified from human plasma or serum by chromatographic methods reported previously (Barnes, D. W., and Silnutzer, J. (1983) J. Biol. Chem. 258, 12548-12552) does not bind to heparin-Sepharose under conditions of physiological ionic strength and pH. In a further examination of the heparin-binding properties of human serum SF, we found that exposure of purified SF to 8 M urea altered several properties of the protein, including heparin affinity, and these alterations remained after removal of the urea from SF solutions. Urea-treated SF bound to heparin under physiological conditions, and salt concentrations of 0.4 M or higher were required for elution of urea-treated SF from heparin-Sepharose at pH 7.0. The alteration of heparin-binding properties of SF also was observed upon exposure of the protein to heat or acid. Treatment of SF with urea, heat, or acid resulted additionally in greatly decreased cell spreading-promoting activity of the molecule. The decreased biological activity was associated with a reduced ability of the treated SF to bind to the cell culture substratum, a prerequisite for the attachment-promoting activity of the molecule. Experiments examining the heparin-binding properties of native SF in unfractionated human plasma indicated that the major portion of SF in blood did not bind to heparin under conditions of physiological ionic strength and pH.