A Macromolecular Drug for Cancer Therapy via Extracellular Calcification.

Cancer chemotherapy typically relies on drug endocytosis and inhibits tumor cell proliferation via intracellular pathways; however, severe side effects may arise. In this study, we performed a first attempt to develop macromolecular-induced extracellular chemotherapy involving biomineralization by absorbing calcium from the blood through a new type of drug, polysialic acid conjugated with folate (folate-polySia), which selectively induces biogenic mineral formation on tumor cells and results in the pathological calcification of tumors. The macromolecule-initiated extracellular calcification causes cancer cell death mainly by intervening with the glycolysis process in cancer cells. Systemic administration of folate-polySia inhibited cervical and breast tumor growth and dramatically improved survival rates in mice. This study provides an extracellular therapeutic approach for malignant tumor diseases via calcification that is ready for clinical trials and offers new insights into macromolecular anticancer drug discovery.

Human Milk Oligosaccharide Supplementation Affects Intestinal Barrier Function and Microbial Composition in the Gastrointestinal Tract of Young Sprague Dawley Rats.

Human milk oligosaccharides (HMOs) are chief maternal milk constituents that feed the intestinal microbiota and drive maturation of the infant gut. Our objective was to determine whether supplementing individual HMOs to a weanling diet alters growth and gut health in rats. Healthy three-week-old Sprague Dawley rat pups were randomized to control, 2'-O-fucosyllactose (2'FL)- and 3'sialyllactose (3'SL)-fortified diets alone or in combination at physiological doses for eight weeks. Body composition, intestinal permeability, serum cytokines, fecal microbiota composition, and messenger RNA (mRNA) expression in the gastrointestinal tract were assessed. Males fed a control diet were 10% heavier and displayed elevated interleukin (IL-18) (p = 0.01) in serum compared to all HMO-fortified groups at week 11. No differences in body composition were detected between groups. In females, HMOs did not affect body weight but 2'FL + 3'SL significantly increased cecum weight. All female HMO-fortified groups displayed significant reductions in intestinal permeability compared to controls (p = 0.02). All HMO-fortified diets altered gut microbiota composition and mRNA expression in the gastrointestinal tract, albeit differently according to sex. Supplementation with a fraction of the HMOs found in breast milk has a complex sex-dependent risk/benefit profile. Further long-term investigation of gut microbial profiles and supplementation with other HMOs during early development is warranted.

Development of a nattokinase-polysialic acid complex for advanced tumor treatment.

Cancer-associated thrombus (CAT) impedes delivery of nanoparticles to tumor sites and also inhibits the ability of immune cells to detect and attack these tumors, particularly in advanced tumors with old thrombi. Nattokinase (NK) is an extract from a popular Japanese food, natto, which consists of boiled soybeans fermented with bacteria. Nattokinase exerts strong fibrinolytic and thrombolytic activities and can unblock blood vessels. To deliver NK to thrombus sites in tumors, we modified the surface of NK with polysialic acid (PSA), which formed complexes via electrostatic interactions, resulting in NK-PSA. Particle size and zeta potential of NK-PSA were evaluated, and differential scanning calorimetry, Fourier-transform infrared spectroscopy, and morphological analyses of NK-PSA were performed. To determine the efficacy of the NK-PSA complex on delivery of nanoparticulate drugs, sialic acid-modified doxorubicin liposomes (DOX-SAL) were used as a model drug. In vivo pharmacokinetic and tissue distribution analyses showed that the blood clearance rate of DOX-SAL was significantly enhanced by NK-PSA, and NK-PSA increased accumulation of 1,1'-dioctadecyl-3,3,3',3'-tetramethylindotricarbocyanine iodide (DiR) labeled SAL (DiR-SAL) in tumors. Analysis of anti-tumor efficacy showed that the combination of NK-PSA and DOX-SAL enhanced anti-tumor activity. These results suggested that NK-PSA combined with DOX-SAL may be an effective strategy to clear CAT and increase the ability of nanoparticles and immune cells to reach tumors.

Bovine Milk Oligosaccharides with Sialyllactose Improves Cognition in Preterm Pigs.

Optimal nutrition is important after preterm birth to facilitate normal brain development. Human milk is rich in sialic acid and preterm infants may benefit from supplementing formula with sialyllactose to support neurodevelopment. Using pigs as models, we hypothesized that sialyllactose supplementation improves brain development after preterm birth. Pigs (of either sex) were delivered by cesarean section at 90% gestation and fed a milk diet supplemented with either an oligosaccharide-enriched whey with sialyllactose (n = 20) or lactose (n = 20) for 19 days. Cognitive performance was tested in a spatial T-maze. Brains were collected for ex vivo magnetic resonance imaging (MRI), gene expression, and sialic acid measurements. For reference, term piglets (n = 14) were artificially reared under identical conditions and compared with vaginally born piglets naturally reared by the sow (n = 12). A higher proportion of sialyllactose supplemented preterm pigs reached the T-maze learning criteria relative to control preterm pigs (p < 0.05), and approximated the cognition level of term reference pigs (p < 0.01). Furthermore, supplemented pigs had upregulated genes related to sialic acid metabolism, myelination, and ganglioside biosynthesis in hippocampus. Sialyllactose supplementation did not lead to higher levels of sialic acid in the hippocampus or change MRI endpoints. Contrary, these parameters were strongly influenced by postconceptional age and postnatal rearing conditions. In conclusion, oligosaccharide-enriched whey with sialyllactose improved spatial cognition, with effects on hippocampal genes related to sialic acid metabolism, myelination, and ganglioside biosynthesis in preterm pigs. Dietary sialic acid enrichment may improve brain development in infants.

Fresh evidence for major brain gangliosides as a target for the treatment of Alzheimer's disease.

Although it was suggested that gangliosides play an important role in the binding of amyloid fragments to neuronal cells, the exact role of gangliosides in Alzheimer's disease (AD) pathology remains unclear. To understand the role of gangliosides in AD pathology in vivo, we crossed st3gal5-deficient (ST3-/-) mice that lack major brain gangliosides GM1, GD1a, GD3, GT1b, and GQ1b with 5XFAD transgenic mice that overexpress 3 mutant human amyloid proteins AP695 and 2 presenilin PS1 genes. We found that ST3-/- 5XFAD mice have a significantly reduced burden of amyloid depositions, low level of neuroinflammation, and did not exhibit neuronal loss or synaptic dysfunction. ST3-/- 5XFAD mice performed significantly better in a cognitive test than wild-type (WT) 5XFAD mice, which was comparable with WT nontransgenic mice. Treatment of WT 5XFAD mice with the sialic acid-specific Limax flavus agglutinin resulted in substantial improvement of AD pathology to a level of ST3-/- 5XFAD mice. Thus, our findings highlight an important role for gangliosides as a target for the treatment of AD.

Polysialic acid-polyethylene glycol conjugate-modified liposomes as a targeted drug delivery system for epirubicin to enhance anticancer efficiency.

Polysialic acid (PSA) is a nonimmunogenic and biodegradable polysaccharide. In recent years, PSA has shown its potential applications to cancer treatment. In this study, PSA-polyethylene glycol (PEG) conjugate was synthesized for the decoration of epirubicin (EPI)-loaded liposomes. The study aimed to evaluate the PSA-PEG conjugated modified liposomes (EPI-PSL) in vitro and in vivo to investigate the role of PSA on physicochemical characteristics and antitumor activity in PEGylated liposomes. EPI-PSL showed a particle size of 116.9 ± 5.2 nm, zeta potential of - 40.3 ± 3.5 mV, and encapsulation efficiency of 99.1 ± 1.5%. The results of in vitro release experiments showed a delayed release of EPI from EPI-PSL. Greater cellular uptake of EPI-PSL was observed compared with PEGylated liposomes (EPI-PL) in B16 cells. Cytotoxicity studies suggested that EPI-PSL exhibited stronger cytotoxic activity than EPI-PL. Though EPI-PSL exhibited comparable blood plasma profiles with EPI-PL, biodistribution studies proved that the distribution of EPI-PSL in tumors was more than that of EPI-PL. The superior antitumor efficacy of EPI-PSL was also verified in the B16 xenograft mouse model with a reduction in systemic toxicity. In conclusion, these results therefore indicated that PSA-modified PEGylated liposomes may represent an excellent anticancer drug delivery system for targeted cancer therapy.

Dietary Sialyllactose Does Not Influence Measures of Recognition Memory or Diurnal Activity in the Young Pig.

Sialic acid (SA) is an integral component of gangliosides and signaling molecules in the brain and its dietary intake may support cognitive development. We previously reported that feeding sialyllactose, a milk oligosaccharide that contains SA, alters SA content and diffusivity in the pig brain. The present research sought to expand upon such results and describe the effects of feeding sialyllactose on recognition memory and sleep/wake activity using a translational pig model. Pigs were provided ad libitum access to a customized milk replacer containing 0 g/L or 380 g/L of sialyllactose from postnatal day (PND) 2-22. Beginning on PND 15, pigs were fitted with accelerometers to track home-cage activity and testing on the novel object recognition task began at PND 17. There were no significant effects of diet on average daily body weight gain, average daily milk intake, or the gain-to-feed ratio during the study (all p ≥ 0.11). Pigs on both diets were able to display recognition memory on the novel object recognition task (p < 0.01), but performance and exploratory behavior did not differ between groups (all p ≥ 0.11). Total activity and percent time spent sleeping were equivalent between groups during both day and night cycles (all p ≥ 0.56). Dietary sialyllactose did not alter growth performance of young pigs, and there was no evidence that providing SA via sialyllactose benefits the development of recognition memory or gross sleep-related behaviors.

Dietary Sialyllactose Influences Sialic Acid Concentrations in the Prefrontal Cortex and Magnetic Resonance Imaging Measures in Corpus Callosum of Young Pigs.

Sialic acid (SA) is a key component of gangliosides and neural cell adhesion molecules important during neurodevelopment. Human milk contains SA in the form of sialyllactose (SL) an abundant oligosaccharide. To better understand the potential role of dietary SL on neurodevelopment, the effects of varying doses of dietary SL on brain SA content and neuroimaging markers of development were assessed in a newborn piglet model. Thirty-eight male pigs were provided one of four experimental diets from 2 to 32 days of age. Diets were formulated to contain: 0 mg SL/L (CON), 130 mg SL/L (LOW), 380 mg SL/L (MOD) or 760 mg SL/L (HIGH). At 32 or 33 days of age, all pigs were subjected to magnetic resonance imaging (MRI) to assess brain development. After MRI, pig serum and brains were collected and total, free and bound SA was analyzed. Results from this study indicate dietary SL influenced (p = 0.05) bound SA in the prefrontal cortex and the ratio of free SA to bound SA in the hippocampus (p = 0.04). Diffusion tensor imaging indicated treatment effects in mean (p < 0.01), axial (p < 0.01) and radial (p = 0.01) diffusivity in the corpus callosum. Tract-based spatial statistics (TBSS) indicated differences (p < 0.05) in white matter tracts and voxel-based morphometry (VBM) indicated differences (p < 0.05) in grey matter between LOW and MOD pigs. CONT and HIGH pigs were not included in the TBSS and VBM assessments. These findings suggest the corpus callosum, prefrontal cortex and hippocampus may be differentially sensitive to dietary SL supplementation.

[Polysialic Acid for Immunomodulation in an Animal Model for Wet Age-Related Macular Degeneration (AMD)]. / Polysialinsäure zur Immunmodulation im Tiermodell der feuchten altersabhängigen Makuladegeneration (AMD).

Background Chronic activation of the innate immune system is a hallmark of retinal degenerative diseases, including age-related macular degeneration (AMD). Overt microglia and macrophage reactivity, as well as dysregulation of the alternative complement system, trigger and sustain retinal degeneration. It is now accepted that there exists a vicious cycle of mononuclear phagocyte reactivity, abnormal intrinsic complement activation, damage of Bruch's membrane, dysfunction of the retinal pigment epithelium, photoreceptor degeneration and choroidal neovascularization (CNV). Targeting the innate immune system may, therefore, be a complementary approach to anti-angiogenic therapy. This article presents data from polysialic acid treatment experiments in the laser-induced mouse model of wet AMD. Material and Methods The laser-CNV mouse model was used to simulate events of neovascular AMD. Polysialic acid was applied by intravitreal injection and microglia activity was assessed with Iba1 staining of retinal and RPE/choroidal flat mounts. Neovascular leakage was determined by fluorescein angiography. Results Intravitreal injection of polysialic acid reduced retinal and RPE/choroidal lesion-associated microglia activity in the laser-induced mouse model of AMD. Polysialic acid treatment also diminished vascular leakage at laser spots in this model. Conclusion Local retinal immunomodulation with polysialic acid presents a novel concept for treatment of inflammatory conditions related to neovascular AMD.

Polysialic acid blocks mononuclear phagocyte reactivity, inhibits complement activation, and protects from vascular damage in the retina.

Age-related macular degeneration (AMD) is a major cause of blindness in the elderly population. Its pathophysiology is linked to reactive oxygen species (ROS) and activation of the complement system. Sialic acid polymers prevent ROS production of human mononuclear phagocytes via the inhibitory sialic acid-binding immunoglobulin-like lectin-11 (SIGLEC11) receptor. Here, we show that low-dose intravitreal injection of low molecular weight polysialic acid with average degree of polymerization 20 (polySia avDP20) in humanized transgenic mice expressing SIGLEC11 on mononuclear phagocytes reduced their reactivity and vascular leakage induced by laser coagulation. Furthermore, polySia avDP20 prevented deposition of the membrane attack complex in both SIGLEC11 transgenic and wild-type animals. In vitro, polySia avDP20 showed two independent, but synergistic effects on the innate immune system. First, polySia avDP20 prevented tumor necrosis factor-α, vascular endothelial growth factor A, and superoxide production by SIGLEC11-positive phagocytes. Second, polySia avDP20 directly interfered with complement activation. Our data provide evidence that polySia avDP20 ameliorates laser-induced damage in the retina and thus is a promising candidate to prevent AMD-related inflammation and angiogenesis.

The polysialic acid mimetics 5-nonyloxytryptamine and vinorelbine facilitate nervous system repair.

Polysialic acid (PSA) is a large negatively charged glycan mainly attached to the neural cell adhesion molecule (NCAM). Several studies have shown that it is important for correct formation of brain circuitries during development and for synaptic plasticity, learning and memory in the adult. PSA also plays a major role in nervous system regeneration following injury. As a next step for clinical translation of PSA based therapeutics, we have previously identified the small organic compounds 5-nonyloxytryptamine and vinorelbine as PSA mimetics. Activity of 5-nonyloxytryptamine and vinorelbine had been confirmed in assays with neural cells from the central and peripheral nervous system in vitro and shown to be independent of their function as serotonin receptor 5-HT1B/1D agonist or cytostatic drug, respectively. As we show here in an in vivo paradigm for spinal cord injury in mice, 5-nonyloxytryptamine and vinorelbine enhance regain of motor functions, axonal regrowth, motor neuron survival and remyelination. These data indicate that 5-nonyloxytryptamine and vinorelbine may be re-tasked from their current usage as a 5-HT1B/1D agonist or cytostatic drug to act as mimetics for PSA to stimulate regeneration after injury in the mammalian nervous system.

Novel pH-sensitive polysialic acid based polymeric micelles for triggered intracellular release of hydrophobic drug.

Polysialic acid (PSA), a non-immunogenic and biodegradable natural polymer, is prone to hydrolysis under endo-lysosomal pH conditions. Here, we synthesized an intracellular pH-sensitive polysialic acid-ursolic acid conjugate by a condensation reaction. To further test the drug loading capability, we prepared paclitaxel-loaded polysialic acid-based amphiphilic copolymer micelle (PTX-loaded-PSAU) by a nanoprecipitation method. Results showed PTX-loaded-PSAU exhibited well-defined spherical shape and homogeneous distribution. The drug-loading was 4.5% with an entrapment efficiency of 67.5%. PTX released from PTX-loaded-PSAU was 15% and 42% in 72 h under simulated physiological condition (pH 7.4) and mild acidic conditions (pH 5.0), respectively. In addition, In vitro cytotoxicity assay showed that PTX-loaded-PSAU retained anti-tumor (SGC-7901) activity with a cell viability of 53.8% following 72 h incubation, indicating PTX-loaded-PSAU could efficiently release PTX into the tumor cells. These results indicated that the pH-responsive biodegradable PTX-loaded-PSAU possess superior extracellular stability and intracellular drug release ability.

Sialylneolacto-N-tetraose c (LSTc)-bearing liposomal decoys capture influenza A virus.

Influenza is a severe disease in humans and animals with few effective therapies available. All strains of influenza virus are prone to developing drug resistance due to the high mutation rate in the viral genome. A therapeutic agent that targets a highly conserved region of the virus could bypass resistance and also be effective against multiple strains of influenza. Influenza uses many individually weak ligand binding interactions for a high avidity multivalent attachment to sialic acid-bearing cells. Polymerized sialic acid analogs can form multivalent interactions with influenza but are not ideal therapeutics due to solubility and toxicity issues. We used liposomes as a novel means for delivery of the glycan sialylneolacto-N-tetraose c (LSTc). LSTc-bearing decoy liposomes form multivalent, polymer-like interactions with influenza virus. Decoy liposomes competitively bind influenza virus in hemagglutination inhibition assays and inhibit infection of target cells in a dose-dependent manner. Inhibition is specific for influenza virus, as inhibition of Sendai virus and respiratory syncytial virus is not observed. In contrast, monovalent LSTc does not bind influenza virus or inhibit infectivity. LSTc decoy liposomes prevent the spread of influenza virus during multiple rounds of replication in vitro and extend survival of mice challenged with a lethal dose of virus. LSTc decoy liposomes co-localize with fluorescently tagged influenza virus, whereas control liposomes do not. Considering the conservation of the hemagglutinin binding pocket and the ability of decoy liposomes to form high avidity interactions with influenza hemagglutinin, our decoy liposomes have potential as a new therapeutic agent against emerging influenza strains.

Development and testing of solid dose formulations containing polysialic acid insulin conjugate: next generation of long-acting insulin.

BACKGROUND: The need for lifelong, daily insulin injections can have a dramatic effect on patient compliance, can be painful, and runs the risk of local infections. Furthermore, needle-stick injuries are common, and the issue of needle disposal is troublesome. Injecting a long-acting insulin analog with needle-free administration would be a significant improvement for diabetic subjects, but is not currently feasible. To achieve a constant, reliable delivery of a novel, long-acting insulin analog, Lipoxen's SuliXen (polysialylated insulin) in a solid dosage form capable of being delivered without a needle has been developed. The aim of this study was to evaluate the feasibility of Lipoxen's SuliXen delivery with the Glide solid dose injector, Glide SDI. MATERIALS AND METHODS: A formulation containing 14 kDa polysialic acid (PSA)-recombinant human insulin conjugate was manufactured at Lipoxen PLC and transferred to Glide Pharma. The PSA-insulin conjugate solution was incorporated into different excipients at Glide Pharma (excipients 1 and 2), and formulations were manufactured containing implants with doses of 0.3 and 1.0 IU of insulin, respectively. Two different polymeric excipients were investigated for their suitable release profiles. The physicomechanical properties of the formulations were characterized in terms of solid dosage form strength (via three-point bend and compression) and disintegration time at 37 degrees C. A preclinical efficacy study was performed in a nondiabetic rat model (Sprague-Dawley). RESULTS: The study demonstrated successful incorporation of PSA-insulin conjugate into formulations compatible for use with the solid dose injector. Physicochemical characterization indicated that each formulation produced was physically robust. For excipient 1, the compressive stress and three-point-bend-test values recorded for the 0.3 IU formulation were 106.99 +/- 14.3 MPa and 30.6 +/- 1.4 N (force in newtons), respectively. Corresponding values for the 1.0 IU dose were 53.10 +/- 10.2 MPa and 16.66 +/- 1.0 N. For excipient 2, the compressive stress and three-point-bend-test values recorded for the 0.3 IU dose were 53.10 +/- 10.2 MPa and 7.64 +/- 0.9 N, respectively, whereas the corresponding values recorded for the 1.0 IU dose were 41.61 +/- 7.4 MPa and 13.18 +/- 1.3 N. Each formulation successfully penetrated a laboratory substrate, achieving 100% penetration in each case. In vivo analysis demonstrated that PSA-insulin conjugate shows prolongation of activity (at least two-fold more compared to insulin) for more than 5 hours in the rat model. CONCLUSION: Even though additional work may be required, for example, to develop several fixed dose formulations, the preliminary results show that solid dosage forms incorporating PSA-insulin conjugate maintained the prolongation of PSA-insulin conjugate activity in the rat model. Convenient and easy to use, the solid dose injector will not only ensure diabetic patient compliance and trust but also provide cost-effective solutions for safe, reliable, and controlled needle-free injection of PSA-insulin conjugate.

[Animal model of distal myopathy with rimmed vacuoles/hereditary inclusion body myopathy and preclinical trial with sugar compounds].

Sialic acids are terminal sugars of glycolipids and glycoproteins and are involved in several cellular processes. Sialic acid biosynthesis occurs in the cytosol, where UDP-N-acetylglucosamine (GlcNAc) is sequentially converted to N-acetylmannosamine (ManNAc) 6-phosphate by UDP-GlcNAc-2-epimerase/ManNAc kinase enzymes, both of which are encoded by the GNE gene. Since the only existing mouse model of DMRV/hIBM (Gne(-/-)hGNED176VTg) exhibited decreased sialic acid levels in most organs, DMRV/hIBM is thought to be secondary to the metabolic defect in sialic acid production. Theoretically, replenishing sialic acid could be employed as a therapeutic option. It has been reported that N-acetylneuraminic acid (NeuAc) and ManNAc are well incorporated into cells and converted to sialic acid. Thus, we evaluated the efficacy and safety of ManNAc, NeuAc, and sialyllactose in the Gne(-/-)hGNED176VTg, by orally administering these agents to mice from 5-15 weeks continuously until they reached 54-57 weeks of age. The treatment showed beneficial effects in terms of survival rate, overall motor performance, myofiber size, ex vivo skeletal muscle contractile properties, and pathology. These low-dose compounds showed acceptable kidney and liver toxicity profiles. Thus our results show that the oral therapy with NeuAc and ManNAc or their derivatives is safe and effective in preventing myopathic symptoms in Gne(-/-)hGNED176VTg mice, and could be considered as a guide for further therapeutic trials.

The effect of modified polysialic acid based hydrogels on the adhesion and viability of primary neurons and glial cells.

In this study we present the enzymatic and biological analysis of polysialic acid (polySia) based hydrogel in terms of its degradation and cytocompatibility. PolySia based hydrogel is completely degradable by endosialidase enzyme which may avoid second surgery after tissue recovery. Viability assay showed that soluble components of polySia hydrogel did not cause any toxic effect on cultured Schwann cells. Moreover, green fluorescence protein transfected neonatal and adult Schwann cells, neural stem cells and dorsal root ganglionic cells (unlabelled) were seeded on polySia hydrogel modified with poly-L-lysine (Pll), poly-L-ornithine-laminin (porn-laminin) or collagen. Water soluble tetrazolium salt assay revealed that modification of the hydrogel significantly improved cell adhesion and viability. These results infer that polySia based scaffolds in combination with cell adhesion molecules and cells genetically modified to express growth factors would potentially be promising alternative in reconstructive therapeutic strategies.

DAS181, a novel sialidase fusion protein, protects mice from lethal avian influenza H5N1 virus infection.

Increasing resistance to currently available influenza antivirals highlights the need to develop alternate approaches for the prevention and/or treatment of influenza. DAS181 (Fludase), a novel sialidase fusion protein that enzymatically removes sialic acids on respiratory epithelium, exhibits potent antiviral activity against influenza A and B viruses. Here, we use a mouse model to evaluate the efficacy of DAS181 treatment against a highly pathogenic avian influenza H5N1 virus. When used to treat mice daily beginning 1 day before infection with A/Vietnam/1203/2004(H5N1) virus, DAS181 treatment at 1 mg/kg/day protected 100% of mice from fatal disease, prevented viral dissemination to the brain, and effectively blocked infection in 70% of mice. DAS181 at 1 mg/kg/day was also effective therapeutically, conferring enhanced survival of H5N1 virus-challenged mice when treatment was begun 72 h after infection. This notable antiviral activity underscores the potential utility of DAS181 as a new class of drug that is effective against influenza viruses with pandemic potential.

Post-training intrahippocampal injection of synthetic poly-alpha-2,8-sialic acid-neural cell adhesion molecule mimetic peptide improves spatial long-term performance in mice.

Several data have shown that the neural cell adhesion molecule (NCAM) is necessary for long-term memory formation and might play a role in the structural reorganization of synapses. The NCAM, encoded by a single gene, is represented by several isoforms that differ with regard to their content of alpha-2,8-linked sialic acid residues (PSA) on their extracellular domain. The carbohydrate PSA is known to promote plasticity, and PSA-NCAM isoforms remain expressed in the CA3 region of the adult hippocampus. In the present study, we investigated the effect on spatial memory consolidation of a PSA gain of function by injecting a PSA mimetic peptide (termed pr2) into the dorsal hippocampus. Mice were subjected to massed training in the spatial version of the water maze. Five hours after the last training session, experimental mice received an injection of pr2, whereas control mice received PBS or reverse peptide injections in the hippocampal CA3 region. Memory retention was tested at different time intervals: 24 h, 1 wk, and 4 wk. The results showed that the post-training infusion of pr2 peptide significantly increases spatial performance whenever it was assessed after the training phase. By contrast, administration of the control reverse peptide did not affect retention performance. These findings provide evidence that (1) PSA-NCAM is involved in memory consolidation processes in the CA3 hippocampal region, and (2) PSA mimetic peptides can facilitate the formation of long-term spatial memory when injected during the memory consolidation phase.