From benchtop to clinic: a translational analysis of the immune response to submicron topography and its relevance to bone healing.

Proper regulation of the innate immune response to bone biomaterials after implantation is pivotal for successful bone healing. Pro-inflammatory M1 and anti-inflammatory M2 macrophages are known to have an important role in regulating the healing response to biomaterials. Materials with defined structural and topographical features have recently been found to favourably modulate the innate immune response, leading to improved healing outcomes. Calcium phosphate bone grafts with submicron-sized needle-shaped surface features have been shown to trigger a pro-healing response through upregulation of M2 polarised macrophages, leading to accelerated and enhanced bone regeneration. The present review describes the recent research on these and other materials, all the way from benchtop to the clinic, including in vitro and in vivo fundamental studies, evaluation in clinically relevant spinal fusion models and clinical validation in a case series of 77 patients with posterolateral and/or interbody fusion in the lumbar and cervical spine. This research demonstrates the feasibility of enhancing biomaterial-directed bone formation by modulating the innate immune response through topographic surface features.

Reduction of fibrogenesis by selective delivery of a Rho kinase inhibitor to hepatic stellate cells in mice.

One of the pathways activated during liver fibrosis is the Rho kinase pathway, which regulates activation, migration, and contraction of hepatic stellate cells (HSC). Inhibition of this kinase by the Rho kinase inhibitor Y27632 [(+)-(R)-trans- 4-(1-aminoethyl)-N-(4-pyridyl)cyclohexanecarboxamide dihydrochloride] has been shown to reduce fibrosis in animal models. However, kinase expression is ubiquitous, so any inhibitor may affect many cell types. We hypothesize that cell-specific delivery of a kinase inhibitor will be beneficial. Therefore, we conjugated Y27632 to the carrier mannose-6-phosphate (M6P) human serum albumin (HSA), which is taken up specifically in activated HSC through the M6P/insulin-like growth factor II receptor. This conjugate decreased protein expression of phosphorylated myosin light chain 2 (pMLC2) and vinculin, downstream of Rho kinase, in activated primary HSC and decreased the migration and contraction of HSC. In an ex vivo model, free Y27632 decreased contractility of rat aortas, whereas the Y27-conjugate did not, showing that the Y27-conjugate does not affect nontarget tissue. In chronic CCl(4)-induced liver fibrosis, both free drug and conjugate reduced HSC activation; however, only the Y27-conjugate significantly reduced collagen deposition. Treatment with the Y27-conjugate, but not with free drug, reduced pMLC2 expression in livers 24 h after injection, demonstrating prolonged inhibition of the Rho kinase pathway. The Rho kinase inhibitor Y27632 can be specifically targeted to HSC using M6PHSA, decreasing its effects in nontarget tissues. The targeted drug effectively reduced fibrotic parameters in vivo via the inhibition of the Rho kinase pathway.

Role of alkaline phosphatase in colitis in man and rats.

BACKGROUND AND AIMS: Crohn's disease (CD) and ulcerative colitis (UC) are chronic multifactorial inflammatory bowel diseases (IBDs) with unknown aetiology, but a deregulated mucosal immune response to gut-derived bacterial antigens is thought to be involved. Toll-like receptor ligands, especially lipopolysaccharide (LPS), contribute to the maintenance of the disease. It has previously been shown that the enzyme alkaline phosphatase (AP) is able to detoxify LPS, and the aim of this study was to examine a possible role in IBDs. METHODS: Intestinal AP (iAP) mRNA expression and LPS dephosphorylation in intestinal biopsies of control subjects and patients with IBD were examined, and the effect of orally administered iAP tablets on the progression of dextran sodium sulfate-induced colitis in rats was subsequently studied. RESULTS: In healthy persons, iAP mRNA and enzyme activity was high in the ileum relative to the colon. In patients with UC and CD, iAP mRNA expression was found to be markedly reduced when inflamed tissue was compared with non-inflamed tissue. Oral administration of iAP tablets to colitic rats resulted in a significant attenuation of colonic inflammation as reflected by reduced mRNA levels for tumour necrosis factor alpha, interleukin 1 beta, interleukin 6 and inducible nitric oxide synthase NOS (iNOS), a reduced iNOS staining and inflammatory cell influx, and a significantly improved morphology of the intestinal wall. CONCLUSIONS: The present study shows that epithelial iAP mRNA expression is reduced in patients with UC and CD. The rat model demonstrates that oral administration of active iAP enzymes in the intestinal tract results in a significant reduction of inflammation. This provides new insight on IBD pathology and a novel treatment approach to this severe inflammatory disease.

The antifibrotic potential of a sustained release formulation of a PDGFß-receptor targeted rho kinase inhibitor.

Rho kinase activity in hepatic stellate cells (HSCs) is associated with activation, transformation and contraction of these cells, leading to extracellular matrix production and portal hypertension in liver cirrhosis. Inhibition of rho kinase activity can reduce these activities, but may also lead to side effects, for instance systemic hypotension. This can be circumvented by liver-specific delivery of a rho kinase inhibitor to effector cells. Therefore, we targeted the rho kinase inhibitor Y27632 to the key pathogenic cells in liver fibrosis, i.e. myofibroblasts including activated HSCs that highly express the PDGFß-receptor, using the drug carrier pPB-MSA. This carrier consists of mouse serum albumin (MSA) covalently coupled to several PDGFßR-recognizing moieties (pPB). We aimed to create a prolonged release system of such a targeted construct, by encapsulating pPB-MSA-Y27632 in biodegradable polymeric microspheres, thereby reducing short-lasting peak concentrations and the need for frequent administrations. Firstly, we confirmed the vasodilating potency of PDGFß-receptor targeted Y27632 in vitro in a contraction assay using HSCs seeded on a collagen gel. We subsequently demonstrated the in vivo antifibrotic efficacy of pPB-MSA-Y27632-loaded microspheres in the Mdr2-/- mouse model of progressive biliary liver fibrosis. A single subcutaneous microsphere administration followed by organ harvest one week later clearly attenuated liver fibrosis progression and significantly suppressed the expression of fibrosis related genes, such as several collagens, profibrotic cytokines and matrix metalloproteinases. In conclusion, we demonstrate that polymeric microspheres are suitable as drug delivery system for the sustained systemic delivery of targeted protein constructs with antifibrotic potential, such as pPB-MSA-Y27632. This formulation appears suitable for the sustained treatment of liver fibrosis and possibly other chronic diseases.

Cellular targeting of the apoptosis-inducing compound gliotoxin to fibrotic rat livers.

Liver fibrosis is associated with proliferation of hepatic stellate cells (HSCs) and their transformation into myofibroblastic cells that synthesize scar tissue. Several studies indicate that induction of apoptosis in myofibroblastic cells may prevent fibrogenesis. Gliotoxin (GTX) was found to induce apoptosis of hepatic cells and caused regression of liver fibrosis. However, the use of apoptosis-inducing drugs may be limited due to lack of cell specificity, with a risk of severe adverse effects. In previous studies, we found that mannose-6-phosphate-modified human serum albumin (M6P-HSA) selectively accumulated in liver fibrogenic cells. The aim of this study therefore was to couple GTX to M6P-HSA and test its pharmacological effects in vitro and in rats with liver fibrosis. The conjugate GTX-M6P-HSA bound specifically to HSCs and reduced their viability. Apoptosis was induced in cultures of human hepatic myofibroblasts (hMFs) and in liver slices obtained from rats with liver fibrosis. In vivo treatment with GTX or GTX-M6P-HSA in bile duct ligated rats revealed a significant decrease in alpha-smooth muscle actin mRNA levels and a reduced staining for this HSC marker in fibrotic livers. In addition, although GTX also affected hepatocytes, GTX-M6P-HSA did not significantly affect other liver cells. In conclusion, we developed an HSC-specific compound that induced apoptosis in human hMFs, rat HSCs, and in fibrotic liver slices. In vivo, both GTX and GTX-M6P-HSA attenuated the number of activated HSCs, but GTX also affected hepatocytes. This study shows that cell-selective delivery of the apoptosis-inducing agent GTX is feasible in fibrotic livers.

Pharmacokinetics of a sustained release formulation of PDGFß-receptor directed carrier proteins to target the fibrotic liver.

Liver fibrogenesis is associated with excessive production of extracellular matrix by myofibroblasts that often leads to cirrhosis and consequently liver dysfunction and death. Novel protein-based antifibrotic drugs show high specificity and efficacy, but their use in the treatment of fibrosis causes a high burden for patients, since repetitive and long-term parenteral administration is required as most proteins and peptides are rapidly cleared from the circulation. Therefore, we developed biodegradable polymeric microspheres for the sustained release of proteinaceous drugs. We encapsulated the drug carrier pPB-HSA, which specifically binds to the PDGFßR that is highly upregulated on activated myofibroblasts, into microspheres composed of hydrophilic multi-block copolymers composed of poly(l-lactide) and poly ethylene glycol/poly(ϵ-caprolactone), allowing diffusion-controlled release. Firstly, we estimated in mice with acute fibrogenesis induced by a single CCl4 injection the half-life of I125-labeled pPB-HSA at 40 min and confirmed the preferential accumulation in fibrotic tissue. Subsequently, we determined in the Mdr2 −/− mouse model of advanced biliary liver fibrosis how the subcutaneously injected microspheres released pPB-HSA into both plasma and fibrotic liver at 24 h after injection, which was maintained for six days. Although the microspheres still contained protein at day seven, pPB-HSA plasma and liver concentrations were decreased. This reduction was associated with an antibody response against the human albumin-based carrier protein, which was prevented by using a mouse albumin-based equivalent (pPB-MSA). In conclusion, this study shows that our polymeric microspheres are suitable as sustained release formulation for targeted protein constructs such as pPB-HSA. These formulations could be applied for the long-term treatment of chronic diseases such as liver fibrosis.

Polymeric microspheres for the sustained release of a protein-based drug carrier targeting the PDGFß-receptor in the fibrotic kidney.

Injectable sustained release drug delivery systems are an attractive alternative for the intravenous delivery of therapeutic proteins. In particular, for chronic diseases such as fibrosis, this approach could improve therapy by reducing the administration frequency while avoiding large variations in plasma levels. In fibrotic tissues the platelet-derived growth factor receptor beta (PDGFßR) is highly upregulated, which provides a target for site-specific delivery of drugs. Our aim was to develop an injectable sustained release formulation for the subcutaneous delivery of the PDGFßR-targeted drug carrier protein pPB-HSA, which is composed of multiple PDGFßR-recognizing moieties (pPB) attached to human serum albumin (HSA). We used blends of biodegradable multi-block copolymers with different swelling degree to optimize the release rate using the model protein HSA from microspheres produced via a water-in-oil-in-water double emulsion evaporation process. The optimized formulation containing pPB-HSA, showed complete release in vitro within 14days. After subcutaneous administration to mice suffering from renal fibrosis pPB-HSA was released from the microspheres and distributed into plasma for at least 7days after administration. Furthermore, we demonstrated an enhanced accumulation of pPB-HSA in the fibrotic kidney. Altogether, we show that subcutaneously administered polymeric microspheres present a suitable sustained release drug delivery system for the controlled systemic delivery for proteins such as pPB-HSA.

The role of beta2-glycoprotein I in liposome-hepatocyte interaction.

Adsorption of serum proteins to the liposomal surface plays a critical role in liposome clearance from the blood. The aim of this study was to investigate the role of liposome-adsorbed serum proteins in the interaction of liposomes with hepatocytes. We analyzed the serum proteins adsorbing to the surface of differently composed small unilamellar liposomes during incubation with human or rat serum, and found that one protein, with a molecular weight of around 55 kDa, adsorbed in a large amount to negatively charged liposomes containing phosphatidylserine (PS) or phosphatidylglycerol (PG). The binding was dependent on the liposomal charge density. The approximately 55-kDa protein was identified as beta2-glycoprotein I (beta2GPI) by Western blotting. Despite the high affinity of beta2GPI for strongly negatively charged liposomes, in vitro uptake and binding experiments with isolated rat hepatocytes, Kupffer cells or liver endothelial cells, and with HepG2 cells showed no enhancing effect of this protein on the association of negatively charged liposomes with any of these cells. On the contrary, an inhibitory effect was observed. We conclude that despite abundant adsorption to negatively charged liposomes, beta2GP1 inhibits, rather than enhances, liposome uptake by liver cells.

A modified cerium-based histochemical method for detection of experimentally-induced ATPase impairment in glomeruli of the rat kidney.

We studied glomerular ATPase activity, as detectable at the light microscopic (LM) level in cryostat sections of the rat kidney, after unilateral local X-irradiation. The biochemically detectable reduction in glomerular ATPase activity after X-irradiation could be demonstrated at the LM level by application of a modified cerium-based technique. Results show a clear reduction of reaction product in glomeruli in X-irradiated kidneys as compared with the contralateral control kidney. Technical parameters (i.e., tissue fixation, second thickness, cerium concentration of the incubation mixture, and percentage H2O2 added for the amplification step) were established for optimal reproducibility of the staining results. We show that this modified staining protocol allows detection of differences of ATPase activity in contrast to conventional histochemical methods. Inhibition studies with various phosphatase inhibitors and competitive substrate inhibition experiments revealed that the enzyme is specific for nucleoside di- and triphosphatases. Since reduced glomerular adenine nucleotidase activity has recently been recognized as an early event in (experimental) glomerulonephritis, we feel that the new staining protocol presented here may be highly relevant for routine tissue section screening in nephropathological research.

Endotoxin induced intraplacental thrombotic tendency and decreased vascular ADPase in the pregnant rat.

The mechanism underlying increased sensitivity for endotoxin in pregnancy, as reflected by intravascular thrombus formation in various organs i.e. the placenta, is unknown. We studied the influence of endotoxin infusion at day 14 upon the vascular antithrombotic ADPase present in the labyrinth of the rat placenta just before term (day 21). Pregnant Wistar rats were infused with either endotoxin (1 microgram/kg body weight) or saline through permanent vena jugularis catheters and their placenta and kidneys were examined at day 21 using light electron microscopy and enzyme cytochemistry at the ultrastructural level. Also, placenta perfusion ex vivo was done using platelets and ADP to test the thrombotic tendency of placental vessels in endotoxin treated and control rats. The results show in both maternal as well as the fetal vessels of the placental labyrinth vascular occlusions and decreased membrane ADPase activity exclusively in endotoxin treated and not in saline infused pregnant animals. Alternate placenta and kidney perfusion ex vivo resulted in intraplacental and intraglomerular platelet aggregation again exclusively in endotoxin-treated rats. It is concluded that vascular ADPase may be affected by endotoxin due to the pregnant condition, resulting in a functional defect in antithrombotic potention which may promote intravascular formation of microthrombi in situ.

Surgical irrigation with pooled human immunoglobulin G to reduce post-operative spinal implant infection.

A multiple-site, nonlethal rabbit surgical model of spinal implant infection was used to assess the efficacy of a spinal wound lavage to reduce post-operative infection from methicillinresistant Staphylococcus aureus (MRSA). Multiple aqueous lavages of isotonic saline were compared to the same procedure using 1wt% pooled human immunoglobulin G (IgG) applied directly to the surgical implant sites. Visually observed clinically relevant signs of infection (e.g. , swelling, erythema, pus) were supported by bacterial enumeration from multiple biopsied tissue and bone sites post-mortem at 7 and 28 days post-challenge. Clinical signs of infection were significantly reduced in IgG-lavaged infected spinal sites. Bacterial enumeration also exhibited statistically significant reductions in soft tissues, bone and on K-wire spinal implants using IgG lavage compared with saline. Complete healing of all surgical wounds was seen after 28 days, although isolated fibrosed abscesses were observed in autopsied sites treated with both IgG and saline lavages. Local use of IgG wound lavage is proposed as supplementary infection prophylaxis against antibiotic resistant implant-centered or surgical wound infection.

Disease-induced drug targeting using novel peptide-ligand albumins.

UNLABELLED: Small therapeutic oligopeptides (two to 12 amino acids), designed for interaction with cytokine and growth factor receptors, unfortunately, are rapidly removed from the body. Efficient glomerular filtration and carrier-mediated membrane transport processes are involved in their clearance. By coupling of such peptides to macromolecules, elimination via these pathways is prevented and exposure to the particular receptors can be largely improved. Some of these constructs undergo receptor-mediated endocytoses and can be used as carriers to deliver associated drugs to various cell types in the body. It has been shown that, in the case of neo-glycoprotein carriers, down-regulation of the receptors aimed at can occur in the diseased state. We therefore designed a new type of polypeptide carrier, homing on receptors that are known to be highly upregulated in the pathological target tissue. For this purpose we designed ligand peptides (minimized proteins) representing the receptor-recognizing domains of PDGF and collagen type VI, aimed at receptors that are highly expressed, particularly on activated hepatic stellate cells (HSC). This myofibroblast-type of cell largely contributes to connective tissue expansion during liver fibrosis. Drug carriers for the stellate cell have not been reported before. METHODS: Cyclic octapeptide moieties (n10--12) with affinity for the two receptors were coupled to HSA (pPB-HSA and pCVI-HSA, respectively). Receptor binding experiments confirmed binding of these ligand peptides to their receptors in vitro. IN VITRO STUDIES: rat HSC were isolated and purified according to standard techniques. The cells were cultured for 2 days (quiescent phenotype) or for 10 days (activated phenotype). Cell cultures were incubated with the carriers and the binding (at 4 degrees C), uptake (at 37 degrees C), and degradation were determined with radioactive and immunohistochemical methods. The results were compared with data obtained with unmodified HSA. IN VIVO STUDIES: the organ distribution of pCVI-HSA and pPB-HSA was determined 10 min after i.v. injection of tracer doses in normal and fibrotic rats, 3 weeks after bile duct ligation. Hepatocellular distribution was scored after double-immunostaining of the liver sections with an antibody against the designated hepatic cell type in combination with anti-HSA IgG. IN VITRO STUDIES: All three carriers preferentially bound to the activated rather than to quiescent HSC. Binding to cells was inhibitable by an excess of unlabelled pCVI-HSA, endocytosis was inhibitable by 2 mM monensin suggestive of lysosomal routing of the proteins, whereas pPB-HSA, at least partly, remained at the cell surface. Degradation products of the carriers were detected extracellularly after incubation with fibrotic rat liver slices during 2-h experiments. IN VIVO STUDIES: 62+/-6% of the dose of pCVI-HSA accumulated in fibrotic livers at 10 min after injection, of which the major part was taken up in HSC. 48+/-9% of pPB-HSA accumulated in fibrotic rat livers and this carrier was also mainly taken up by HSC (5). Similar amounts of both constructs were taken up in normal rat livers, but predominantly in other cell types. The preferential homing to the stellate cells, only in the fibrotic liver is explained by the marked proliferation of this cell type as well as overexpression of the targeted receptors on these cells in the diseased state. CONCLUSIONS: The in vivo results support the in vitro studies showing accumulation of these modified albumins in HSC in fibrotic rat livers and, in particular, in the stellate cells. The results demonstrate the specificity of the stellate cell targeting and imply applicability of pCVI-HSA as carriers for drugs that act intracellularly. In addition, pPB-HSA may be used to deliver drugs that act extracellularly, such as receptor antagonists. This concept may create new opportunities for delivery of conventional drugs that are not effective enough in vivo and/or display serious extrahepatic side-effects. Minimized proteins attached to soluble or particle type of macromolecules represent a novel carrier modality of which selective body distribution is induced by the disease process to be targeted. They can be utilized as receptor antagonists and at the same time can deliver therapeutic agents to the desired site of action (dual targeting).

Glucose and insulin responses during mixed meals or infusion of glucose in pregnant and lactating rats.

We studied the glucose tolerance in freely moving rats throughout pregnancy and lactation and during the first week after weaning. Dioestrous virgin rats served as controls. Basal glucose and insulin levels were determined after a 2-hr fasting period. Subsequently, the changes of the insulin and the glucose levels were determined during ingestion of a mixed ad lib meal or a 2 g mixed test meal, or during infusion of glucose (7.4 mg/min for 20 min) into the vena cava. Basal glucose levels were high during early pregnancy, low during late pregnancy, and in the normal range throughout lactation and after weaning. Basal insulin levels were decreased at the end of lactation. The results of the ad lib meal and test meal experiments were essentially the same. Glucose tolerance during meals was somewhat decreased early in pregnancy. The corresponding insulin responses greatly increased during the last week of pregnancy. Glucose tolerance during IV infusion of glucose was normal during pregnancy, but increased during lactation. Insulin responses to the infusion were increased during pregnancy and decreased during lactation. We concluded that glucose tolerance is hardly affected by pregnancy and even increases in the course of lactation. This is effected by an increased responsiveness of the B-cells to glucose during late pregnancy and by an increased turnover of glucose during lactation. We discuss to what extent the actions of progesterone, placental lactogen and prolactin may explain these adaptions of maternal metabolism.

Targeting naproxen to non-parenchymal liver cells protects against endotoxin induced liver damage.

Non-steroidal anti-inflammatory drugs (NSAID's) could be of value in the treatment of liver disease; however, their use in this situation is limited by renal side effects. Therefore, we explored whether naproxen covalently bound to human serum albumin NAP-HSA) was able to reduce toxicity in an acute model of liver disease induced by endotoxin in rats pretreated with Corynebacterium parvum. In the isolated perfused liver of such animals endotoxin induced cholestasis (0.62 +/- 0.05 vs. 0.24 +/- 0.09 microliter.min-1.g liver-1; p < 0.05), increased vascular resistance (11300 +/- 400 vs. 311000 +/- 2000 dyn.s.cm-5; p < 0.05) and alanine aminotransferase release (22 +/- 9 vs. 149 +/- IU/l; p < 0.05). At the highest dose tested (22 mg/kg, corresponding to 6.0 mumoles naproxen), NAP-HSA normalized ALT release (21 +/- 10 IU/l: p < 0.05) while an equimolar amount of non-targeted naproxen was only partially effective (56 +/- 19 IU/l). A conventional dose of naproxen similarly prevented transaminase release. Cholestasis and increased vascular resistance were also prevented by NAP-HSA. Drug targeting by linking drugs to proteins is a potentially useful approach to maximizing drug effect while minimizing adverse events; this could be particularly useful for compounds with potentially serious adverse effects in patients with chronic liver disease such as the nonsteroidal anti-inflammatory agents used in the present study.

Effect of chronic bile duct obstruction and LPS upon targeting of naproxen to the liver using naproxen-albumin conjugate.

Naproxen covalently linked to human serum albumin (NAP-HSA) is efficiently targeted to endothelial and Kupffer cells of the liver and may offer a new therapeutic approach in the treatment of liver disease associated with inflammatory processes. In the present investigation we explored the pharmacokinetic behaviour of targeted and non-targeted naproxen as well as the pharmacokinetic properties of the active metabolite, Naproxen lysine (Nap lysine), in rats rendered fibrotic by bile duct ligation (BDL) for 4 weeks. Furthermore, we studied the effect of endotoxemia, experimentally induced by intravenous injection of 800 microg/kg lipopolysaccaride (LPS) upon the pharmacokinetics of these agents in order to investigate the feasibility of targeting naproxen to non-parenchymal cells in the inflamed and fibrotic liver. Our studies demonstrate that liver disease altered the pharmacokinetic behaviour of the different naproxen compounds. Thus, initial plasma concentrations of NAP HSA and naproxen were markedly lower in BDL rats accompanied by an increase of the volume of distribution during the terminal elimination phase (Vd(beta) BDL vs control 114 +/- 63 vs 50 +/- 7 and 202 +/- 24 vs 115 +/- 11 ml/kg for naproxen and NAP-HSA, respectively). After injection of LPS, no significant change in the pharmacokinetics of NAP-HSA was found whereas the naproxen treated control animals showed an increase in the terminal volume of distribution (176 +/- 34 vs 115 +/- 11 ml/kg) as well as an elevation of the plasma half-life (171 +/- 27 vs 116 +/- 14 min). The feasibility of targeting naproxen to the chronically diseased liver could be clearly demonstrated: 15 min after administration of the conjugate 46% and 55% of the administered dose was found in the liver of CTR and BDL rats, whereas after injection of free naproxen only 5% and 12% of the dose was detected in liver tissue, respectively. We conclude that targeting albumin-linked naproxen to non-parenchymal cells in the liver is still feasible under the pathological conditions induced in the present study. Liver fibrosis induced significant alterations in the pharmacokinetic behaviour of the studied compounds.

Targeting of naproxen covalently linked to HSA to sinusoidal cell types of the liver.

The kinetic behaviour of a naproxen human serum albumin conjugate (Nap23-HSA) was investigated in rats and in isolated perfused rat livers (IPRL), as compared to its active metabolite naproxen-lysine (Nap-lysine) and free naproxen. Through covalently linking the anti-inflammatory drug naproxen to HSA, this drug can be selectively delivered to non parenchymal cells of the liver. Liver endothelial and Kupffer cells play an important role in the pathogenesis of inflammatory liver diseases. Targeting naproxen to these cells might increase its efficacy and reduce the side effects. The altered kinetic properties of Nap23-HSA, after i.v. injection of 22 mg x kg(-1), as compared to an equimolar amount of the uncoupled drug, were demonstrated in vivo by a decrease in the steady state volume of distribution (41 +/- 5 vs. 134 +/- 19 ml x kg(-1)), a decrease in its clearance (0.48 +/- 0.05 vs. 0.63 +/- 0.1 ml x min(-1) x kg(-1)), a shorter plasma half life (60 +/- 11 vs. 152 +/- 44 min) and a sustained biliary excretion. Liver targeting of Nap23-HSA was clearly demonstrated: drug content of the liver 180 min after injection was about 30 times higher for Nap23-HSA as compared to naproxen itself. The IPRL experiments showed that the Vmax of hepatic removal of the conjugate was 40 microg x min(-1) x g liver(-1). With doses below receptor saturation a rapid removal of the conjugate (t1/2 = 6 min) from the perfusion medium was found. In conclusion, this study demonstrates the saturable uptake of Nap23-HSA and its lysosomal degradation in both in vivo and IPRL experiments. Covalently linked naproxen is released as Nap-lysine. This active metabolite accumulates in Kupffer and endothelial cells in which it reaches therapeutic concentrations. Release from these cells leads to rapid uptake by hepatocytes and carrier mediated excretion into bile. Levels of Nap-lysine in bile and plasma reflect the slowest step in its generation: the proteolytic release in endothelial and Kupffer cells.

The geometry of the human paraspinal muscles with the aid of three-dimensional computed tomography scans and 3-Space Isotrak.

STUDY DESIGN: Accurate determination of the three-dimensional coordinates of paraspinal muscles is presented. OBJECTIVES: To determine the precise position and the size of the paraspinal muscles. SUMMARY OF BACKGROUND DATA: The accurate measurements of the muscle moment arms are important in the evaluation of computer models for spinal movement. It has been reported that a change in the modelling of the erector spinae muscles can alter the compressive forces in the spinal column by 20% and can increase the offsetting shear forces. Classic studies used measurements from cross-sectional anatomic diagrams of human cadavers, scaled to the width and depth of the trunk of the subject, to calculate the moment that produces the joint torque. METHODS: Computed tomography scans of two male cadavers provided data on the bony elements. Three-dimensional coordinates of the origins and insertions of the muscle-fascicles of the paraspinal muscles were obtained with the use of 3-Space Isotrak equipment. The bony and muscle coordinates were combined in the ANSYS (version 5.4; Swanson Analysis Systems, Canonsberg, PA) program. RESULTS: Results of this combination and the three-dimensional coordinates of the paraspinal muscles as acquired by the 3-Space Isotrak are given. CONCLUSION: The position and the moment arms of paraspinal muscles were accurately determined. This is important for further evaluation of mathematical models.

A novel spinal implant infection model in rabbits.

STUDY DESIGN: A new spinal implant model was designed to study device-centered infection with methicillin-resistant Staphylococcus aureus in multiple noncontiguous surgical sites in the lumbar spine region of a rabbit. OBJECTIVE: To develop a multiple-site spinal implant device-centered infection model in rabbits. SUMMARY OF BACKGROUND DATA: Results in many recent studies show that postoperative wound infection after spinal implant surgery and the increase in antibiotic-resistant bacteria are a concern. Anti-infection strategies must be tested in relevant animal models that will lead to appropriate clinical studies. METHODS: Eight anesthetized New Zealand White rabbits underwent completely isolated partial laminectomy and subsequent stainless steel Kirschner wire implantation directly into the transverse processes of vertebrae T13, L3, and L6. The middle sites (L3) were used as sterile control sites, and the outer sites (T13, L6) were challenged with different amounts of methicillin-resistant Staphylococcus aureus. Rabbits were killed after 7 days, and biopsies were performed to provide evidence for device-centered infection. Bacterial growth on the implant surfaces and in surrounding tissues and bone was assayed. RESULTS: Overall device-centered infection was established after 7 days in 100% of the sites challenged with 10(3) colony-forming units methicillin-resistant Staphylococcus aureus or higher. No infection was seen in any of the control sites located between infected vertebrae. Multiple blood and liver samples showed that the separate localized infections did not become systemic after 7 days. CONCLUSIONS: This new animal model demonstrates that multiple biomaterial implants can be evaluated in the same animal and provides a technique for investigating postoperative device-centered infection of the spine. Infection was demonstrated in noncontiguous lumbar sites of the spine, whereas adjacent control sites remained sterile. Because there was no cross contamination or systemic spread of the infection, multiple anti-infection strategies or implant materials can now be tested for efficacy in a single animal to combat dramatic and costly postoperative implant infections.

Investigations into the stabilisation of drugs by sugar glasses: II. Delivery of an inulin-stabilised alkaline phosphatase in the intestinal lumen via the oral route.

In this study the possibility to deliver the acid-sensitive enzyme alkaline phosphatase (AP) from calf intestine (CIAP) to the intestinal system by oral administration was investigated. Tablets were prepared and in vitro evaluated. Final proof of concept studies were performed in rats. This acid labile enzyme is potentially useful in the treatment of sepsis, a serious condition during which endotoxins can migrate into the blood stream. The CIAP was freeze-dried with inulin and subsequently compacted into round biconvex tablets with a diameter of 4mm and a weight of 25-30 mg per tablet. The tablets were coated with an enteric coating in order to ensure their survival in the stomach. In vitro evaluation of tablets containing alkaline phosphatase from bovine intestine (BIAP) was the first step in the development. It was found that tablets without enteric coating dissolved rapidly in 0.10 M HCl with total loss of enzymatic activity of the alkaline phosphatase. Tablets that were coated were stable for at least 2 h in 0.10 M HCl, but dissolved rapidly when the pH was increased to 6.8. Furthermore, it was shown that the enzymatic activity of the released BIAP was fully preserved. The in vivo test clearly showed that the oral administration of enteric coated tablets resulted in the release of enzymatically active CIAP in the intestinal lumen of rats. The location of the enhanced enzymatic activity of AP in the intestines varied with the time that had passed between the administration of the tablets and the sacrificing of the rats. Also, the level of enzymatic activity increased with an increasing number of tablets that were administered.