Biological and bactericidal properties of Ag-doped bioactive glass in a natural extracellular matrix hydrogel with potential application in dentistry.

The aim of this study was the fabrication and evaluation of a novel bioactive and bactericidal material, which could have applications in dentistry by supporting tissue regeneration and killing oral bacteria. Our hypothesis was that a new scaffold for pulp-dentin tissue engineering with enhanced antibacterial activity could be obtained by associating extracellular matrix derived from porcine bladder with an antibacterial bioactive glass. Our study combines in vitro approaches and ectopic implantation in scid mice. The novel material was fabricated by incorporating a sol-gel derived silver (Ag)-doped bioactive glass (BG) in a natural extracellular matrix (ECM) hydrogel in ratio 1:1 in weight % (Ag-BG/ECM). The biological properties of the Ag-BG/ECM were evaluated in culture with dental pulp stem cells (DPSCs). In particular, cell proliferation, cell apoptosis, stem cells markers profile, and cell differentiation potential were studied. Furthermore, the antibacterial activity against Streptococcus mutans and Lactobacillus casei was measured. Moreover, the capability of the material to enhance pulp/dentin regeneration in vivo was also evaluated. Our data show that Ag-BG/ECM significantly enhances DPSCs' proliferation, it does not affect cell morphology and stem cells markers profile, protects cells from apoptosis, and enhances in vitro cell differentiation and mineralisation potential as well as in vivo dentin formation. Furthermore, Ag-BG/ECM strongly inhibits S. mutans and L. casei growth suggesting that the new material has also anti-bacterial properties. This study provides foundation for future clinical applications in dentistry. It could potentially advance the currently available options of dental regenerative materials.

Matrix-bound nanovesicle-associated IL-33 supports functional recovery after skeletal muscle injury by initiating a pro-regenerative macrophage phenotypic transition.

Injuries to skeletal muscle are among the most common injuries in civilian and military populations, accounting for nearly 60% of extremity injuries. The standard of care for severe extremity injury has been focused upon limb salvage procedures and the utilization of tissue grafts or orthotics in conjunction with rehabilitation to avoid amputation. Nonetheless, many patients have persistent strength and functional deficits that permanently impact their quality of life. Preclinical and clinical studies have shown that partial restoration of functional skeletal muscle tissue following injury can be achieved by the implantation of a biologic scaffold composed of extracellular matrix (ECM). These favorable outcomes are mediated, at least in part, through local immunomodulation. The mechanisms underlying this immunomodulatory effect, however, are poorly understood. The present study investigates a potential mechanistic driver of the immunomodulatory effects; specifically, the effect of selected ECM components upon inflammation resolution and repair. Results show that the host response to skeletal muscle injury is profoundly altered and functional recovery decreased in il33-/- mice compared to age- and sex-matched wildtype counterparts by 14 days post-injury. Results also show that IL-33, contained within matrix-bound nanovesicles (MBV), supports skeletal muscle regeneration by regulating local macrophage activation toward a pro-remodeling phenotype via canonical and non-canonical pathways to improve functional recovery from injury compared to untreated il33-/- counterparts. Taken together, these data suggest that MBV and their associated IL-33 cargo represent a novel homeostatic signaling mechanism that contributes to skeletal muscle repair.

Menisco-fibular ligament - an overview: cadaveric dissection, clinical and magnetic resonance imaging diagnosis, arthroscopic visualisation and treatment.

BACKGROUND: Injury to the menisco-fibular ligament (MFiL) is not commonly recognised. The anatomy of the lateral meniscus is complex and structure-function relationships are only partly understood. The purpose of the present study was to evaluate the MFiL, an anatomic structure rarely discussed that stabilises the lateral meniscus at the level of the hiatus popliteus and may have a crucial role in pathology of lateral meniscus injury. MATERIALS AND METHODS: The MFiL was dissected from its attachment at the lateral meniscus to its insertion on fibular head in 12 human normal cadaver knees. The dimensions were determined and its anatomic position visualised throughout a 90° range of motion. Findings were documented on digital photographs and on video. Results were compared against the magnetic resonance imaging (MRI) appearance of the injured MFiL in 20 patients. Concomitant knee injuries in those patients were also analysed to determine the most frequent pattern of injuries. RESULTS: The normal MFiL showed an inverted trapezoid-shape with a mean width proximally of 13 mm, mean width distally of 8.5 mm and a mean length of 18.4 mm. MRI visualisation of the ligament was possible even in regular sequences; however, additional radial plane sequences were also used. Arthroscopic visualisation and manipulation was optimal when the camera was inserted into the postero-lateral gutter with full knee extension. CONCLUSIONS: The MFiL stabilises the postero-lateral knee in concert with the menisco-femoral ligaments. Injury to the MFiL can be a cause of chronic postero-lateral pain syndrome with associated instability. Further anatomical and biomechanical studies are needed in order to fully evaluate its importance.

Oncological safety of stromal vascular fraction enriched fat grafting in two-stage breast reconstruction after nipple sparing mastectomy: long-term results of a prospective study.

OBJECTIVE: Autologous fat transfer (AFT) is commonly used to treat implant palpability and prevent fibrosis and thinning in mastectomy skin flaps. A major limit to this procedure is volume retention over time, leading to the introduction of fat enrichment with stromal vascular fraction (SVF+AFT). Oncological concerns have been raised over the injection of an increased concentration of progenitors cells (ASCs) in the SVF. The aim of the study is to evaluate the long-term cancer recurrence risk of SVF+AFT cases compared to AFT, in patients undergoing Nipple Sparing Mastectomy (NSM). PATIENTS AND METHODS: A prospective study was designed to compare three groups of patients undergoing NSM followed by SVF+AFT, AFT or none (control group), after a two-stage breast reconstruction. Patients were strictly followed-up for at least 5-years from the second stage reconstructive procedure. Loco-regional and systemic recurrence rate were evaluated over time as the primary outcome. Logistic regression was used to investigate which factors were associated with recurrence events and independent variables of interest were: surgical technique, age above 50 years old, lympho-vascular invasion, oncological stage, adjuvant or neoadjuvant chemotherapy, adjuvant radiotherapy and adjuvant hormone therapy. RESULTS: 41 women were included in G1 (SVF+AFT), 64 in G2 (AFT), and 64 in G3 (control group). Loco-regional recurrence rate was 2.4% for G1, 4.7% for G2, and 1.6% for G3. Systemic recurrence was 7.3%, 3.1%, and 3.1%, respectively. Among the variables included, there were no significant risk factors influencing a recurrence event, either loco-regional or systemic. In particular, SVF+AFT (G1) did not increase the oncological recurrence. CONCLUSIONS: Our data suggest that both centrifuged and SVF-enhanced fat transfer have a similar safety level in comparison to patients who did not undergo fat grafting in breast reconstruction after NSM.

In vitro comparison of human fibroblasts from intact and ruptured ACL for use in tissue engineering.

The present study compares fibroblasts extracted from intact and ruptured human anterior cruciate ligaments (ACL) for creation of a tissue engineered ACL-construct, made of porcine small intestinal submucosal extracellular matrix (SIS-ECM) seeded with these ACL cells. The comparison is based on histological, immunohistochemical and RT-PCR analyses. Differences were observed between cells in a ruptured ACL (rACL) and cells in an intact ACL (iACL), particularly with regard to the expression of integrin subunits and smooth muscle actin (SMA). Despite these differences in the cell source, both cell populations behaved similarly when seeded on an SIS-ECM scaffold, with similar cell morphology, connective tissue organization and composition, SMA and integrin expression. This study shows the usefulness of naturally occurring scaffolds such as SIS-ECM for the study of cell behaviour in vitro, and illustrates the possibility to use autologous cells extracted from ruptured ACL biopsies as a source for tissue engineered ACL constructs.

Thrombolysis vs. bleeding from hemostatic sites by a prourokinase mutant compared with tissue plasminogen activator.

BACKGROUND: A single site mutant (M5) of prourokinase (proUK) was developed to make proUK less vulnerable to spontaneous activation in plasma. This was a problem that seriously compromised proUK in clinical trials, as it precluded proUK-mediated fibrinolysis at therapeutic concentrations. METHODS AND RESULTS: After completing dose-finding studies, 12 anesthetized dogs with femoral artery thrombosis were given either M5 (2.0 mg kg(-1)) or tissue plasminogen activator (t-PA) (1.4 mg kg(-1)) by i.v. infusion over 60 min (20% administered as a bolus). Two pairs of standardized injuries were inflicted at which hemostasis was completed prior to drug administration. Blood loss was quantified by measuring the hemoglobin in blood absorbed from these sites. Thrombolysis was evaluated at 90 min and was comparably effective by both activators. Rethrombosis developed in one t-PA dog. The principal difference found was that blood loss was 10-fold higher with t-PA (mean approximately 40 mL) than with M5 (mean approximately 4 mL) (P = 0.026) and occurred at more multiple sites (mean 2.7 vs. 1.2). This effect was postulated to be related to differences in the mechanism of plasminogen activation by t-PA and M5 in which the latter is promoted by degraded rather than intact (hemostatic) fibrin. In addition, two-chain M5 was efficiently inactivated by plasma C1 inactivator, an exceptional property which helped contain its non-specific proteolytic effect. CONCLUSIONS: Intravascular thrombolysis by M5 was accompanied by significantly less bleeding from hemostatic sites than by t-PA. This was attributed to the proUK paradigm of fibrinolysis being retained at therapeutic concentrations by the mutation.

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.

Marrow-derived cells populate scaffolds composed of xenogeneic extracellular matrix.

INTRODUCTION: The source of cells that participate in wound repair directly affects outcome. The extracellular matrix (ECM) and other acellular biomaterials have been used as therapeutic scaffolds for cell attachment and proliferation and as templates for tissue repair. The ECM consists of structural and functional proteins that influence cell attachment, gene expression patterns, and the differentiation of cells. OBJECTIVE: The objective of this study was to determine if the composition of acellular matrix scaffolds affects the recruitment of bone marrow-derived cellular elements that populate the scaffolds in vivo. METHODS: Scaffolds composed of porcine tissue ECM, purified Type I collagen, poly(L)lactic coglycolic acid (PLGA), or a mixture of porcine ECM and PLGA were implanted into subcutaneous pouches on the dorsum of mice. The origin of cells that populated the matrices was determined by first performing bone marrow transplantation to convert the marrow of glucose phosphate isomerase 1b (Gpi-1(b)) mice to cells expressing glucose phosphate isomerase 1a (Gpi-1(a)). RESULTS: A significant increase in Gpi-1(a) expressing cells was present in sites implanted with the porcine ECM compared to sites implanted with either Type I collagen or PLGA. Use of recipient mice transplanted with marrow cells that expressed beta-galactosidase confirmed that the majority of cells that populated and remodeled the naturally occurring porcine ECM were marrow derived. Addition of porcine ECM to the PLGA scaffold caused a significant increase in the number of marrow-derived cells that became part of the remodeled implant site. CONCLUSION: The composition of bioscaffolds affects the cellular recruitment pattern during tissue repair. ECM scaffolds facilitate the recruitment of marrow-derived cells into sites of remodeling.

Protection from reperfusion injury in the isolated rat heart by postischaemic deferoxamine and oxypurinol administration.

A Langendorff isolated rat heart preparation was used to determine the effect of oxypurinol, a xanthine oxidase inhibitor, and deferoxamine, an iron binding agent, on the extent of myocardial reperfusion injury after 60 minutes of ischaemia. Thirty rats were divided into three groups of 10, and an isolated heart preparation made from each rat. The isolated hearts were perfused for 15 minutes with a modified Krebs-Henseleit perfusate solution to permit stabilisation of the preparation. Each heart was then subjected to 60 minutes of total ischaemia at 37 degrees C followed by 60 minutes of reperfusion with either saline treated perfusate, oxypurinol treated perfusate (1.3 mmol.litre-1), or deferoxamine treated perfusate (0.61 mmol.litre-1). Reperfusion injury was assessed by the total amount of creatine phosphokinase released into the perfusate, by changes in myocardial vascular resistance, and by morphological examination. The saline treated group released significantly more creatine phosphokinase into the perfusate than either the oxypurinol treated group (p less than 0.05) or the deferoxamine treated group (p less than 0.05). The mean vascular resistance increased for all groups during the 60 minutes of reperfusion compared with that just before ischaemia but was significantly greater in the saline treated group than in the drug treated groups (p less than 0.01). Ultrastructural examination of a randomly selected heart from each group after 60 minutes of reperfusion showed pronounced attenuation of mitochondrial and endoplasmic reticulum swelling, increased maintenance of membrane integrity, and diminished separation of myofilaments in the oxypurinol treated and deferoxamine treated hearts.(ABSTRACT TRUNCATED AT 250 WORDS)

Histochemical demonstration of endothelial superoxide and hydrogen peroxide generation in ischaemic and reoxygenated rat tissues.

OBJECTIVE: The aims were to test and evaluate two novel and independent histochemical methods for detecting the initial postischaemic burst of superoxide and hydrogen peroxide in buffer perfused rat tissues during reflow after 60 min warm ischaemia. METHODS: The first is a high manganese/diaminobenzidine technique, in which superoxide oxidises Mn2+ to Mn3+, which in turn oxidises diaminobenzidine to form amber coloured polymers, observable by light microscopy. The second is a high iron/diaminobenzidine technique, in which hydrogen peroxide oxidises diethylenetriaminepenta-acetate chelated Fe2+ to form intermediate species, which in turn oxidise diaminobenzidine similarly to Mn3+. Various isolated organs of the rat were rendered ischaemic for 60 min, and reperfused with oxygen or air equilibrated buffers containing diaminobenzidine and either Mn2+ or Fe2+. Tissues were fixed by perfusion with Trump's solution and processed for light microscopy. RESULTS: Both manganese and iron methods consistently showed the appearance of reaction product on the luminal surfaces of arterial, capillary, and venular endothelial cells in lung, heart, and intestine of the rat during the first 2 to 3 min of reoxygenation after ischaemia. The histochemical reactions were nearly absent in non-manganese-treated and non-iron-treated controls. Superoxide dismutase strongly inhibited Mn2+/diaminobenzidine reaction product formation and catalase strongly inhibited Fe2+/diaminobenzidine reaction product formation, when tested in specially perfused lung preparations in which these specific antioxidant enzymes were concentrated. CONCLUSIONS: These histochemical techniques provide direct, visual evidence that a burst of reactive oxygen species is generated in postischaemic rat tissues. The Mn2+/diaminobenzidine and Fe2+/diaminobenzidine techniques permit investigation of the endothelium derived reactive oxygen by simple laboratory procedures available to almost any investigator at low marginal cost. The endothelial oxidants so revealed may be of pathophysiological significance in a variety of cardiovascular disorders.

Phytoplankton biomass and composition in a well-flushed, sub-tropical estuary: The contrasting effects of hydrology, nutrient loads and allochthonous influences.

The primary objective of this study was to examine trends in phytoplankton biomass and species composition under varying nutrient load and hydrologic regimes in the Guana Tolomato Matanzas estuary (GTM), a well-flushed sub-tropical estuary located on the northeast coast of Florida. The GTM contains both regions of significant human influence and pristine areas with only modest development, providing a test case for comparing and contrasting phytoplankton community dynamics under varying degrees of nutrient load. Water temperature, salinity, Secchi disk depth, nutrient concentrations and chlorophyll concentrations were determined on a monthly basis from 2002 to 2012 at three representative sampling sites in the GTM. In addition, microscopic analyses of phytoplankton assemblages were carried out monthly for a five year period from 2005 through 2009 at all three sites. Results of this study indicate that phytoplankton biomass and composition in the GTM are strongly influenced by hydrologic factors, such as water residence times and tidal exchanges of coastal waters, which in turn are affected by shifts in climatic conditions, most prominently rainfall levels. These influences are exemplified by the observation that the region of the GTM with the longest water residence times but lowest nutrient loads exhibited the highest phytoplankton peaks of autochthonous origin. The incursion of a coastal bloom of the toxic dinoflagellate Karenia brevis into the GTM in 2007 demonstrates the potential importance of allochthonous influences on the ecosystem.

Resting metabolic rate and postprandial thermogenesis in highly trained and untrained males.

The purpose was to compare the resting metabolic rate (RMR) and thermic effect of a meal (TEM) in exercise trained and untrained individuals. TEM was measured for 180 min and blood samples were drawn for determination of plasma insulin, glucose, triiodothyronine (T3) and thyroxine (T4). Results indicated that highly trained subjects demonstrated a higher RMR when expressed in kilocalories per minute and per kilogram fat-free weight (FFW) than do untrained subjects. TEM was lower in trained (55.8 +/- 3.1 kcal) than in untrained (79.2 +/- 3.7 kcal) subjects. No differences were noted between the two groups for plasma levels of insulin, glucose, T3, and T4. A higher RMR and lower TEM persisted in the trained group compared with the untrained group when groups were matched for FFW and body fat. Results support a higher RMR in endurance athletes and a lower TEM even after control is exerted over differences in body composition.

Resting metabolic rate and postprandial thermogenesis in vegetarians and nonvegetarians.

Resting metabolic rate (RMR), thermic effect of a meal (TEM), and associated hormonal changes were studied in vegetarians and nonvegetarians. RMR was established by indirect calorimetry in 12 male vegetarians (VEG) and 11 nonvegetarians (NVEG) of similar body fat and aerobic fitness. Subjects ingested a liquid meal and TEM was measured for 180 min postprandially. Plasma concentrations of glucose, insulin and thyroid hormones (T3 and T4) were determined before and after meal ingestion. Absolute RMR was comparable between VEG and NVEG. However, TEM was lower (p less than 0.01) in VEG (55.8 +/- 3.3 kcal/180 min) vs NVEG (76.4 +/- 3.6). Plasma levels of glucose and insulin were similar between the two groups whereas plasma T3 was slightly but nonsignificantly lower in vegetarians. A vegetarian diet may decrease the postprandial thermic response; this does not support the supposition that an elevated TEM is a factor contributing to the lower body weight in vegetarians than in omnivores.

Xenogeneic extracellular matrix grafts elicit a TH2-restricted immune response.

BACKGROUND: Porcine small intestinal submucosa (SIS) is an acellular, naturally derived extracellular matrix (ECM) that has been used for tissue remodeling and repair in numerous xenotransplantations. Although a vigorous immune response to xenogeneic extracellular matrix biomaterials is expected, to date there has been evidence for only normal tissue regeneration without any accompanying rejection. The purpose of this study was to determine the reason for a lack of rejection. METHODS: Mice were implanted s.c. with xenogeneic tissue, syngeneic tissue, or SIS, and the graft site analyzed histologically for rejection or acceptance. Additionally, graft site cytokine levels were determined by reverse transcriptase polymerase chain reaction and SIS-specific serum antibody isotype levels were determined by ELISA. RESULTS: Xenogeneically implanted mice showed an acute inflammatory response followed by chronic inflammation and ultimately graft necrosis, consistent with rejection. Syngeneically or SIS implanted mice, however, showed an acute inflammatory response that diminished such that the graft ultimately became indistinguishable from native tissue, observations that are consistent with graft acceptance. Graft site cytokine analysis showed an increase in interleukin-4 and an absence of interferon-gamma. In addition, mice implanted with SIS produced a SIS-specific antibody response that was restricted to the IgG1 isotype. Reimplantation of SIS into mice led to a secondary anti-SIS antibody response that was still restricted to IgG1. Similar results were observed with porcine submucosa derived from urinary bladder. To determine if the observed immune responses were T cell dependent, T cell KO mice were implanted with SIS. These mice expressed neither interleukin-4 at the implant site nor anti-SIS-specific serum antibodies but they did accept the SIS graft. CONCLUSIONS: Porcine extracellular matrix elicits an immune response that is predominately Th2-like, consistent with a remodeling reaction rather than rejection.

The protective effect of heparin in a dog model of rethrombosis following pharmacologic thrombolysis.

Rethrombosis is an important clinical problem for patients who have benefitted from pharmacologic thrombolysis. The present study describes a dog model of arterial thrombosis, which includes endothelial denudation, intimal damage, and stenosis, and is suitable for studying the phenomena of both thrombolysis and subsequent rethrombosis. The model was used to determine the effect of tissue-type plasminogen activator (t-PA), high and low dose heparin, and saline upon the incidence of rethrombosis after t-PA-induced thrombolysis. Initial thrombolysis with reflow was achieved with 0.4 mg/kg t-PA, intravenous bolus injection, followed immediately by 0.4 mg/kg t-PA, 30 min infusion, in 40 of 42 dogs (95%) that had an occlusive, 125I-labelled thrombus created in a segment of femoral artery. The 40 dogs in which reperfusion was achieved were randomly sorted into 4 groups of 10 each which then received either saline, t-PA (0.4 mg kg-1 infused over 1 h), low dose heparin (500 U bolus injection then 250 U h-1 for 24 h), or high dose heparin (1,500 U bolus injection then 500 U h-1 for 24 h). Sixty percent (6/10) of the saline treated dogs showed occlusive rethrombosis at 24 h. The incidence of occlusive rethrombosis was 9/10 in the t-PA treated group (p = NS), 3/10 in the low dose heparin treated group (p = NS), and 0/10 in the high dose heparin treated group (p less than 0.01). Two smaller groups consisting of 5 dogs each were treated with either saline or high dose heparin alone (no t-PA). None of the dogs in either group showed thrombolysis with reflow.(ABSTRACT TRUNCATED AT 250 WORDS)

Output power and metabolic input power of skeletal muscle contracting linearly to compress a pouch in a mock circulatory system.

Output power and metabolic input power values were determined for unconditioned canine latissimus dorsi (two), gastrocnemius (seven), and triceps (three) muscles contracting linearly to cause compression of a doubly valved pouch in a hydraulic model of the circulation. The motor nerves to the muscles were stimulated tetanically with 450 msec trains of 0.1 msec pulses having a frequency of 50/sec. The muscles were contracted 10, 20, 30, and 40 times per minute and pouch output in milliliters per minute was measured directly for each muscle at each contraction (train) rate. The output power in milliwatts was determined by two methods: (1) by using the pouch output and the pressure rise imparted to the stroke volume (average power) and (2) by using the pressure-volume loop. Metabolic input power in milliwatts was determined from the oxygen consumption in milliliters per minute of the working muscle. It was found that as the pouch output was increased, the pouch output power and the metabolic input power both increased. The average power output was slightly less than that computed from the pressure-volume loop. The mean output power values, when pumping at L liters per minute, were 0.62 L (average) and 0.75 L mW/gm (pressure-volume loop) for the latissimus dorsi muscles; 0.83 L (average) and 1.16 L mW/gm (pressure-volume loop) for the gastrocnemius muscles; and 0.55 L (average) and 0.66 L mW/gm (pressure-volume loop) for the triceps muscles. The percent efficiency of energy conversion ranged from 9.2% to 17.8% for the latissimus dorsi muscles, from 5.1% to 19.5% for the gastrocnemius muscles, and from 10.5% to 27.3% for the triceps muscles. However, it should not be concluded that one muscle type is better than another on the basis of percent efficiency because efficiency does not take endurance into account. An important observation in this study relates to the large output obtained with the three linearly contracting muscle types. All were capable of pumping in excess of 1.5 L/min. A second observation relates to the absence of fatigue, although determination of endurance was not an objective in these studies.

Correlation of motor-evoked potential response to ischemic spinal cord damage.

The prevalence of morbidity is a major deterrent to the success of aortic aneurysm replacement operations. We have developed a model of spinal cord ischemia, based on the amplitude reduction of the motor-evoked potential, which produces approximately a 90% prevalence of paraplegia. Regional blood flow was studied with the use of radioactive microspheres, and results showed that there was a significant decrease in flow to the lumbar cord (85% reduction) during aortic occlusion, followed by a twofold to threefold hyperemia that persisted for 24 hours. Histopathologic examination of the cord revealed that the greater portion of microgliosis, spongiosis, and neuronal damage was confined to the gray matter of the cord, and its severity increased as one progressed caudally. The somatosensory-evoked potential disappeared before the motor-evoked potential L-2 signal in all dogs, with a mean disappearance time of 10.9 +/- 5.6 minutes, compared with 21 +/- 6.6 minutes for the motor-evoked potential. Both the sensory-evoked potential and the motor-evoked potential cord signal were present 24 hours later in all dogs tested. The peripheral nerve motor-evoked potential disappeared within 1 minute of cord ischemia, was not present 24 hours later, and hence appears to be too sensitive to use as an indicator of spinal cord damage. Plotting spinal cord motor-evoked potential amplitude reduction versus both histopathologic damage and regional blood flow revealed a positive correlation between motor-evoked potential amplitude reduction, decreased cord perfusion, and increased histopathologic damage. In addition, it may be possible to make inferences about the neurologic status of a subject based on the magnitude and time-course of the motor-evoked potential's amplitude reduction and wave morphology.

Endothelial cell adherence to small intestinal submucosa: an acellular bioscaffold.

Degradable biomaterials to be used as scaffolds for tissue repair will ideally be able to support new blood vessel growth. The present study evaluated the adherence of human dermal microvascular endothelial cells (HMECs) to an acellular resorbable scaffold material derived from the small intestinal submucosa (SIS). HMECs were exposed to hydrated and dehydrated forms of SIS and to plastic surfaces coated with one of four different known components of the SIS extracellular matrix: collagen Type I, collagen Type IV, fibronectin, and laminin. Results showed that adherence of HMECs to hydrated SIS was greater than to any of the other tested surfaces (P < 0.05). Exposure of HMECs to either soluble collagen Type IV or soluble fibronectin prior to exposure of these cells to hydrated SIS showed only partial inhibition of HMEC attachment. We conclude that HMECs find hydrated SIS to be a suitable substrate for adherence and that dehydration of SIS adversely affects the ability of HMECs to adhere in vitro. The cause of HMEC adherence to SIS appears to be a combination of both its composition and architecture.

In vivo degradation of 14C-labeled small intestinal submucosa (SIS) when used for urinary bladder repair.

The rate of in vivo degradation was determined for a naturally occurring biomaterial derived from the extracellular matrix of the small intestinal submucosa (SIS). The SIS was labeled by giving weekly intravenous injections of 10 microCi of 14C-proline to piglets from 3 weeks of age until the time of sacrifice at 26 weeks. The resultant SIS prepared from these pigs contained approximately 10(3) fold more 14C than unlabeled tissues. The labeled SIS was used to repair experimental defects in the urinary bladder of 10 dogs. The animals were sacrificed at post-operative times ranging from 3 days to 1 year and the remodeled urinary bladder tissue was harvested for evaluation of 14C by a combination of liquid scintillation counting and accelerator mass spectrometry. The remodeled tissue contained less than 10% of the 14C (disintegrations per minute/gram tissue wet weight) at 3 months post-surgery compared to the SIS biomaterial that was originally implanted. The SIS scaffold was replaced by host tissue that resembled normal bladder both in structure and function. After implantation, 14C was detected in highest concentrations in the blood and the urine. The SIS bioscaffold provides a temporary scaffold for tissue remodeling with rapid host tissue remodeling, degradation, and elimination via the urine when used as a urinary bladder repair device.