Molecular network mechanism in cerebral ischemia-reperfusion rats treated with human urine stem cells.

Objective: To explore the effect of human urine-derived stem cells (husc) in improving the neurological function of rats with cerebral ischemia-reperfusion (CIR), and report new molecular network by bioinformatics, combined with experiment validation. Methods: After CIR model was established, and husc were transplanted into the lateral ventricle of rats，neurological severe score (NSS) andgene network analysis were performed. Firstly, we input the keywords "Cerebral reperfusion" and "human urine stem cells" into Genecard database and merged data with findings from PubMed so as to get their targets genes, and downloaded them to make Venny intersection plot. Then, Gene ontology (GO) analysis, kyoto encyclopedia of genes and genomes (KEGG) pathway analysis and protein-protein interaction (PPI) were performed to construct molecular network of core genes. Lastly, the expressional level of core genes was validated via quantitative real-time polymerase chain reaction (qRT-PCR), and localized by immunofluorescence. Results: Compared with the Sham group, the neurological function of CIR rats was significantly improved after the injection of husc into the lateral ventricle; at 14 days, P = 0.028, which was statistically significant. There were 258 overlapping genes between CIR and husc, and integrated with 252 genes screened from PubMed and CNKI. GO enrichment analysis were mainly involved neutrophil degranulation, neutrophil activation in immune response and platelet positive regulation of degranulation, Hemostasis, blood coagulation, coagulation, etc. KEGG pathway analysis was mainly involved in complement and coagulation cascades, ECM-receptor. Hub genes screened by Cytoscape consist ofCD44, ACTB, FN1, ITGB1, PLG, CASP3, ALB, HSP90AA1, EGF, GAPDH. Lastly, qRT-PCR results showed statistic significance (P < 0.05) in ALB, CD44 and EGF before and after treatment, and EGF immunostaining was localized in neuron of cortex. Conclusion: husc transplantation showed a positive effect in improving neural function of CIR rats, and underlying mechanism is involved in CD44, ALB, and EGF network.

Discovery of astragaloside IV against high glucose-induced apoptosis in retinal ganglion cells: Bioinformatics and in vitro studies.

OBJECTIVE: To examine the therapeutic mechanism of astragaloside IV (AS-IV) in the management of retinal ganglion cell (RGC) injury induced by high glucose (HG), a comprehensive approach involving the integration of network pharmacology and conducting in vitro and in vivo experiments was utilized. METHODS: A rat model of diabetic retinopathy (DR) injury was created by administering streptozotocin through intraperitoneal injection. Additionally, a model of RGC injury induced by HG was established using a glucose concentration of 0.3 mmol/mL. Optical coherence tomography (OCT) images were captured 8 weeks after the injection of AS-IV. AS-IV and FBS were added to the culture medium and incubated for 48 h. The viability of cells was assessed using a CCK-8 assay, while the content of reactive oxygen species (ROS) was measured using DCFH-DA. Apoptosis was evaluated using Annexin V-PI. To identify the targets of AS-IV, hyperglycemia, and RGC, publicly available databases were utilized. The Metascape platform was employed for conducting GO and KEGG enrichment analyses. The STRING database in conjunction with Cytoscape 3.7.2 was used to determine common targets of protein-protein interactions (PPIs) and to identify the top 10 core target proteins in the RGC based on the MCC algorithm. qRT-PCR was used to measure the mRNA expression levels of the top10 core target proteins in RGCs. RESULTS: OCT detection indicated that the thickness of the outer nucleus, and inner and outer accessory layers of the retina increased in the AS-IV treated retina compared to that in the DM group but decreased compared to that in the CON group. Coculturing RGC cells with AS-IV after HG induction resulted in a significant increase in cell viability and a decrease in ROS and apoptosis, suggesting that AS-IV can reduce damage to RGC cells caused by high glucose levels by inhibiting oxidative stress. There were 14 potential targets of AS-IV in the treatment of RGC damage induced by high glucose levels. The top 10 core target proteins identified by the MCC algorithm were HIF1α, AKT1, CTNNB1, SMAD2, IL6, SMAD3, IL1ß, PPARG, TGFß1, and NOTCH3. qRT-PCR analysis showed that AS-IV could upregulate the mRNA expression levels of SMAD3, TGF-ß1, and NOTCH3, and downregulate the mRNA expression levels of HIF1α, AKT1, CTNNB1, SMAD2, SMAD3, and IL-1ß in high glucose-induced RGC cells. CONCLUSION: The findings of this study validate the efficacy of astragaloside IV in the treatment of DR and shed light on the molecular network involved. Specifically, HIF1α, AKT1, CTNNB1, SMAD2, SMAD3, and IL-1ß were identified as the crucial candidate molecules responsible for the protective effects of astragaloside IV on RGCs.

Bioinformatics-based Study on the Effects of Umbilical Cord Mesenchymal Stem Cells on the Aging Retina.

BACKGROUND: Retinal aging is one of the common public health problems caused by population aging and has become an important cause of acquired vision loss in adults. The aim of this study was to determine the role of human umbilical cord mesenchymal stem cells (hUCMSCs) in delaying retinal ganglion cell (RGC) aging and part of the network of molecular mechanisms involved. METHODS: A retinal ganglion cell senescence model was established in vitro and treated with UCMSC. Successful establishment of the senescence system was demonstrated using ß- galactosidase staining. The ameliorative effect of MSC on senescence was demonstrated using CCK8 cell viability and Annexin V-PI apoptosis staining. The relevant targets of RGC, MSC, and senescence were mainly obtained by searching the GeneCards database. The protein interaction network among the relevant targets was constructed using the String database and Cytoscape, and 10 key target genes were calculated based on the MCC algorithm, based on which Gene ontologies (GO) enrichment and the Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment were performed. Changes in relevant target genes were detected using real-time fluorescence quantitative PCR and the mechanism of action of UCMSC was determined by RNA interference. RESULTS: ß-galactosidase staining showed that UCMSC significantly reduced the positive results of RGC. The retinal aging process was alleviated. The bioinformatics screen yielded 201 shared genes. 10 key genes were selected by the MCC algorithm, including vascular endothelial growth factor A (VEGFA), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), albumin (ALB), interleukin- 6 (IL6), tumor necrosis factor (TNF), tumor protein P53 (TP53), insulin (INS), matrix metalloproteinase 9 (MMP9), epidermal growth factor (EGF), interleukin-1ß (IL1B), and enrichment to related transferase activity and kinase activity regulated biological processes involved in oxidative stress and inflammation related pathways. In addition, PCR results showed that all the above molecules were altered in expression after UCMSC involvement. CONCLUSION: This experiment demonstrated the role of UCMSC in delaying retinal ganglion cell senescence and further elucidated that UCMSC may be associated with the activation of VEGFA, TP53, ALB, GAPDH, IL6, IL1B, MMP9 genes and the inhibition of INS, EGF, and TNF in delaying retinal senescence.

Salidroside protects RGC from pyroptosis in diabetes-induced retinopathy associated with NLRP3, NFEZL2 and NGKB1, revealed by network pharmacology analysis and experimental validation.

OBJECTIVE: To investigate the effect of salidroside (SAL) in protecting retinal ganglion cell (RGC) from pyroptosis and explore associated molecular network mechanism in diabetic retinapathy (DR) rats. METHODS: HE, Nissl and immunofluorescence staining were used to observe the retinal morphological change, and the related target genes for salidroside, DR and pyroptosis were downloaded from GeneCard database. Then Venny, PPI, GO, KEGG analysis and molecular docking were used to reveal molecular network mechanism of SAL in inhibiting the pyroptosis of RGC. Lastly, all hub genes were confirmed by using qPCR. RESULTS: HE and Nissl staining showed that SAL could improve the pathological structure known as pyroptosis in diabetic retina, and the fluorescence detection of pyroptosis marker in DM group was the strongest, while they decreased in the SAL group(P < 0.05)). Network pharmacological analysis showed 6 intersecting genes were obtained by venny analysis. GO and KEGG analysis showed 9 biological process, 3 molecular function and 3 signaling pathways were involved. Importantly, molecular docking showed that NFE2L2, NFKB1, NLRP3, PARK2 and SIRT1 could combine with salidroside, and qPCR validates the convincible change of CASP3, NFE2L2, NFKB1, NLRP3, PARK2 and SIRT1. CONCLUSION: Salidroside can significantly improve diabetes-inducedRGC pyrotosis in retina, in which, the underlying mechanism is associated with the NLRP3, NFEZL2 and NGKB1 regulation.

4D-DIA quantitative proteomics revealed the core mechanism of diabetic retinopathy after berberine treatment.

OBJECTIVE: To reveal the core mechanism of berberine (BBR) in the treatment of diabetic retinopathy (DR), by using Four-dimensional independent data acquisition (4D-DIA) proteomics combined bioinformatics analysis with experimental validation. METHODS: DR injury model was established by injecting streptozotocin intraperitoneally. At 8 weeks after BBR administration, optical coherence tomography (OTC) photos and Hematoxylin-eosin staining from retina in each group were performed, then the retina was collected for 4D-DIA quantitative proteomics detection. Moreover, difference protein analysis, Gene Ontology (GO) enrichment and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway, protein-protein interaction (PPI) network, as well as molecular docking was performed, respectively. In the part of experiment, Western blot (WB) and immunofluorescent staining was used to confirm the change and distribution of carbonic anhydrase 1 (CA1), one of the most important molecules from quantitative PCR detection. Lastly, RNA knockdown was used to determine the crucial role of CA1 in retinal pigment epithelial cells (RPEs) administrated with berberine. RESULTS: OCT detection showed that the outer nucleus, inner layer and outer accessory layer of RPEs were thinned in DR group, compared with in sham one, while they were thickened after berberine administration, when compared with in DR group. 10 proteins were screened out by using proteomic analysis and Venny cross plot, in which, denn domain containing 1A (DENND1A) and UTP6 small subunit processome component (UTP6) was down-regulated, while ATPase copper transporting alpha (ATP7A), periplakin (PPL), osteoglycin (OGN), nse1 Homolog (NSMCE1), membrane metalloendopeptidase (MME), lim domain only 4 (LMO4), CA1 and fibronectin 1 (FN1) was up-regulated in DR group, and the BBR treatment can effectively reverse their expressions. PPI results showed that 10 proteins shared interactions with each other, but only ATP7A, FN1 and OGN exhibited directly associated with each other. Moreover, we enlarged the linked relation up to 15 genes in network, based on 10 proteins found from proteomics detection, so as to perform deep GO and KEGG analysis. As a result, the most important biological process is involving rRNA processing; the most important cell component is small subunit processor; the most important molecular function is Phospholipid binding; the KEGG pathway was Ribosome biogenesis in eukaryotes. Moreover, molecular docking showed that LMO4, ATP7A, PPL, NSMCE1, MME, CA1 could form a stable molecular binding pattern with BBR. Of these, the mRNA expression of CA1, PPL and ATP7A and the protein level of CA1 was increased in DR, and decreased in BBR group. Lastly, CA1 RNA knockdown confirmed the crucial role of CA1 in RPE administered with BBR. CONCLUSION: The present findings confirmed the role of BBR in DR treatment and explained associated molecular network mechanism, in which, CA1 could be considered as a crucial candidate in the protection of RPEs with berberine treatment.

Neuroprotective effect of salidroside on hippocampal neurons in diabetic mice via PI3K/Akt/GSK-3ß signaling pathway.

BACKGROUND: Diabetic encephalopathy is manifested by cognitive dysfunction. Salidroside, a nature compound isolated from Rhodiola rosea L, has the effects of anti-inflammatory and antioxidant, hypoglycemic and lipid-lowering, improving insulin resistance, inhibiting cell apoptosis, and protecting neurons. However, the mechanism by which salidroside alleviates neuronal degeneration and improves learning and memory impairment in diabetic mice remains unclear. OBJECTIVE: To investigate the effects and mechanisms of salidroside on hippocampal neurons in streptozotocin-induced diabetic mice. MATERIALS AND METHODS: C57BL/6 mice were randomly divided into 4 groups to receive either sham (control group (CON)), diabetes mellitus (diabetes group (DM)), diabetes mellitus + salidroside (salidroside group (DM + SAL)), and diabetes mellitus + salidroside + phosphatidylinositol 3-kinase (PI3K) inhibitor LY294002 (diabetes mellitus + salidroside + LY294002 group (DM + SAL + LY294002)). After 12 weeks of diabetes onset, the cognitive behaviors were tested using Morris water maze. The number of hippocampal neurons was detected by Nissl staining. The expressions of PI3K, p-PI3K, Akt, p-Akt, GSK-3ß, p-GSK-3ß, cleaved caspase-3, caspase-3, Bax, Bcl-2, MAP2, and SYN in the hippocampus were detected by Western blot. Moreover, the expression of MAP2 and SYN in the hippocampus was further confirmed by immunofluorescence staining. RESULTS: Salidroside increased the time of diabetic mice in the platform quadrant and reduced the escape latency of diabetic mice. Salidroside also increased the expression of p-PI3K, p-Akt, p-GSK-3ß, MAP2, SYN, Bcl-2, while suppressed the expression of cleaved caspase-3, caspase3, and Bax in the DM + SAL group compared with the DM group (P < 0.05). The Nissl staining showed that the number of hippocampus neurons in the DM + SAL group was increased with the intact, compact, and regular arrangement, compared with the DM groups (P < 0.05). Interestingly, the protective effects of salidroside on diabetic cognitive dysfunction, hippocampal morphological alterations, and protein expressions were abolished by inhibition of PI3K with LY294002. CONCLUSIONS: Salidroside exerts neuroprotective properties in diabetic cognitive dysfunction partly via activating the PI3K/Akt/GSK-3ß signaling pathway.

Heterogeneous organization of Locus coeruleus: An intrinsic mechanism for functional complexity.

Locus coeruleus (LC) is a small nucleus located deep in the brainstem that contains the majority of central noradrenergic neurons, which provide the primary source of noradrenaline (NA) throughout the entire central nervous system (CNS).The release of neurotransmitter NA is considered to modulate arousal, sensory processing, attention, aversive and adaptive stress responses as well as high-order cognitive function and memory, with the highly ramified axonal arborizations of LC-NA neurons sending wide projections to the targeted brain areas. For over 30 years, LC was thought to be a homogeneous nucleus in structure and function due to the widespread uniform release of NA by LC-NA neurons and simultaneous action in several CNS regions, such as the prefrontal cortex, hippocampus, cerebellum, and spinal cord. However, recent advances in neuroscience tools have revealed that LC is probably not so homogeneous as we previous thought and exhibits heterogeneity in various aspects. Accumulating studies have shown that the functional complexity of LC may be attributed to its heterogeneity in developmental origin, projection patterns, topography distribution, morphology and molecular organization, electrophysiological properties and sex differences. This review will highlight the heterogeneity of LC and its critical role in modulating diverse behavioral outcomes.

A Mechanistic Exploratory Study on the Therapeutic Efficacy of Astragaloside IV Against Diabetic Retinopathy Revealed by Network Pharmacology.

Purpose: Diabetic retinopathy (DR) is a serious complication of diabetes mellitus, which nearly happens to all the diabetic sufferers. This study aims to identify the preliminary molecular regulation involved in the therapeutic efficacy of astragaloside IV (AS- IV) for DR. Methods: Diabetic rat models were established and treated with AS-IV. Optical coherence tomography (OCT) and Hematoxylin-eosin (HE) staining was employed to demonstrate the histopathological changes. The main targets of AS-IV were identified by searching from public databases of traditional Chinese medicine (GeneCards, PharmMapper and Swiss Target Prediction). Besides, disease targets of DR were also obtained by integrated data from GEO datasets and predicted from public databases. Protein-protein interaction (PPI) network was constructed by Cytoscape with overlapping genes and 10 core targets were selected, on which Gene Ontology (GO) along with Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis were conducted. The interaction between AS-IV and these crucial genes were analyzed using molecular docking. RT-qPCR and western blot were used to verify the expression variation of core targets. Results: OCT imaging and HE staining demonstrated that AS-IV administration significantly increased retinal thickness in diabetic rats, obviously alleviating DR induced histopathological changes as well as elevated blood glucose levels. 107 common targets of AS-IV and DR were determined after intersection. PPI network analysis filtered 10 hub genes potentially targeted by AS-IV, including VEGFA, CASP3, HIF1α, STAT3, CTNNB1, SRC, AKT1, EGFR, IL1ß and IL6. Enrichment analysis indicated that these genes were mainly enriched in biological processes like T cell activation, epithelial cell proliferation and protein kinase B signaling, and involved in oxidative stress, apoptosis and inflammation-related pathways. The molecular docking prediction suggested that AS-IV exhibited stable binding to these core targets. In addition, mRNA levels of core targets in diabetic rats were differentially expressed before and after AS-IV treatment. Western blot further revealed that AS-IV treatment elevated DR-depressed protein levels of PI3K and AKT. Conclusion: Our study elucidated the effect of AS-IV in attenuating retinopathy induced by diabetes in rats and preliminarily unveiled the therapeutic efficacy of AS-IV in the treatment of DR might be attributed to activation of PI3K-AKT signaling pathway.

Electronic structure and interaction in CH4@C60: a first-principle investigation.

CH4@C60 was the first example within which an organic molecule has been embedded in C60. CH4 can rotate freely in the molecular cage, and the carbon skeleton structure of the C60 has no obvious deformation. The electronic structure of CH4@C60 and interaction between C60 and CH4 were studied under quantum mechanical calculation method. The different reaction sites on C-C bonds in C60 and the weak Van der Waals interaction between CH4 and C60 were shown clearly. These results and the orbital interaction between CH4 and C60 were helpful for understanding and further application of this unique biggest organic molecule CH4 contained in C60 structure so far.

Probing the glass transition in reversible cross-linked polymer composites.

Understanding the nature of glass transition is still a great challenge. Glass transition is widely observed in many glassy materials; however, it has never been unambiguously observed in reversible cross-linked polymer, which is an ideal model of the percolation process. Herein, we report the synthesis of a reversible cross-linked polymer incorporated with four-armed Diels-Alder (DA) dynamic covalent bonds, and the robust experimental observation of percolation-induced glass transition in this reversible four-armed cross-linked polymer (DAMF1). Temperature-modulated differential scanning calorimetry (TMDSC) experiment results clearly revealed the presence of a glass transition along with an endothermic or exothermic peak associated with DA/retro-DA (RDA) reaction related to the reconstitution/disassociation of the DAMF1's four-armed cross-linked network. In situ 13C variable-temperature solid-state NMR experiments further confirmed the DA/RDA reaction during glass transition at a molecular level. The above experimental results provide a direct experimental evidence for the recently developed percolation model of glass transition, which provides new insights into the nature of glass transition.

Histone deacetylase 2 is involved in µ­opioid receptor suppression in the spinal dorsal horn in a rat model of chronic pancreatitis pain.

Chronic pain occurs in ~85-90% of chronic pancreatitis (CP) patients. However, as the pathogenesis of CP pain remains to be fully understood, the current therapies for CP pain remain inadequate. Emerging evidence has suggested that the epigenetic modulations of genes are involved in chronic pain. In the present study, intrapancreatic trinitrobenzene sulfonic acid infusions were used to establish a CP model in rats. Mechanical allodynia was measured with von Frey filaments. Immunofluorescent staining analysis was used to observe the expression changes of histone deacetylase 2 (HDAC2) and µ­opioid receptor (MOR), and intrathecal administration of the selective HDAC2 inhibitor AR­42 was used to assess the underlying mechanisms. The expression levels of c­Jun N­terminal kinase (JNK) in the thoracic spinal cord were detected by western blotting, and the mRNA expression levels of interleukin (IL)1­ß, IL­6 and tumor necrosis factor (TNF)­α were detected by reverse transcription­quantitative polymerase chain reaction. The results demonstrated that HDAC2 expression was upregulated during the course of CP induction, while MOR activity in the thoracic spinal dorsal horn was significantly suppressed. Intrathecal infusion of AR­42 significantly attenuated CP­induced mechanical allodynia, with rescued MOR activity. Additionally, HDAC2 facilitated the release of inflammatory cytokines, including IL­1ß, IL­6 and TNF­α. These results suggested that the underlying mechanisms of HDAC2 regulating MOR activity under CP induction may occur via promoting the release of inflammatory cytokines, thus activating the JNK signaling pathway. The present study suggested that the epigenetic­regulated disturbance of MOR is dependent on the endogenous analgesia system in CP, which may a provide novel therapeutic strategy for treating pain in CP.

Astrocytic NDRG2 is involved in glucocorticoid-mediated diabetic mechanical allodynia.

AIMS: The present study aims to test whether astrocytes contribute to glucocorticoid-mediated diabetic mechanical allodynia. METHODS: Streptozotocin (STZ)-induced diabetic rats were used in our study. The intrathecal operation was performed 21 days after the onset of diabetes. Diabetic mechanical allodynia was present 28 d after the onset of diabetes, and the mechanical threshold was tested using von Frey filaments. Immunohistochemistry, including immunofluorescent histochemical staining, was performed to observe the morphology of the spinal dorsal horn (SDH). Western blot analysis was employed as a semi-quantitative assay of the expression levels of GFAP and NDRG2 associated with diabetic mechanical allodynia. RESULTS: Diabetic rats displayed mechanical allodynia and activated astrocytes in the SDH 28 days after the onset of diabetes. This allodynia was attenuated by intrathecal administration of the astrocyte-specific inhibitor l-α-aminoadipate. In parallel, intrathecal injection of RU486, a glucocorticoid receptor antagonist, inhibited the activation of astrocytes in the SDH, alleviating the diabetes-induced mechanical allodynia. Furthermore, we found that dorsal horn astrocytes express abundant N-myc downstream-regulated gene 2 (NDRG2), which contributes to astrocyte reactivity. NDRG2 was over-expressed in activated astrocytes in diabetic rats with mechanical allodynia. Intrathecal injection of RU486 prevented the over-expression of NDRG2, which reversed the astrocyte reactivity and diabetic tactile allodynia. CONCLUSIONS: These results suggest that glucocorticoid-mediated over-expression of NDRG2 may contribute to the activation of dorsal horn astrocytes, which play a crucial role in diabetic mechanical allodynia. Thus, inhibiting glucocorticoid receptors and/or astrocyte reactivity in the SDH may be a therapeutic strategy for treating diabetic tactile allodynia.

Protective effects of curcumin on retinal Müller cell in early diabetic rats.

AIM: To explore the effects and potential mechanisms of curcumin on retinal Müller cell in early diabetic rats. METHODS: Diabetic rats were induced by a single intraperitoneal injection of streptozotocin (STZ). Male Sprague-Dawley (SD) rats were randomly assigned into 4 groups: control group (naïve SD rats administered with a single intraperitoneal injection of citric buffer), diabetic group (STZ-diabetic rats), dimethyl sulfoxide (DMSO) group (diabetic rats intraperitoneally administered with mixture of DMSO and normal saline, once a day) and curcumin group (diabetic rats intraperitoneally administered with curcumin, 80mg/kg, once a day). Three months after diabetes onset, malondialdehyde (MDA, indication of oxidative stress level) and reduced glutathione (GSH) in retina were detected with kits, glial fibrillary acidic protein (GFAP) in retina was revealed by immunohistochemistry and Western blot, and retinal glutamine synthetase (GS) were observed by Western blot. RESULTS: Compared with control group, retinal MDA was increased, and GSH was decreased in diabetic and DMSO groups (P<0.05, respectively). While, retinal MDA and GSH in curcumin group showed no difference compared with control group (P>0.05). Furthermore, up-regulation of retinal GFAP and down-regulation of retinal GS were detected in diabetic and DMSO groups, and no alteration could be observed in curcumin group revealed with Western blot. Compared with control group, retinal Müller cells showed significant increase in GFAP immunochemistry staining in diabetic and DMSO groups. Moreover, GFAP-positive staining was decreased in curcumin group compared with diabetic group. CONCLUSION: Curcumin inhibits diabetic retinal oxidative stress, protects Müller cell, and prevents the down-regulation of GS in diabetic retina. Therefore, curcumin has a therapeutic potential in the treatment of diabetic retinopathy (DR).

An animal model for trigeminal neuralgia by compression of the trigeminal nerve root.

BACKGROUND: Microvascular compression of the trigeminal nerve root is a major cause of most trigeminal neuralgia (TN) in patients; however, no reliable animal model to further study the pathogenesis of TN currently exists. OBJECTIVE: Our objective was to establish a novel and practical animal model for TN by chronic compression of the trigeminal (CCT) nerve root in rats, which would provide a better animal model to mimic the clinical feature of TN on the research of the pathogenesis of TN. STUDY DESIGN: A randomized, double blind, controlled animal trial. METHODS: Sixteen adult male Sprague-Dawley rats (200-220 g) were randomly divided into 2 groups: one group that received chronic compression of the trigeminal nerve root (the CCT group, n=8) and another group that received sham operation without compression (the sham operation group, n=8). A small plastic filament was retrogressively inserted into the intracalvarium from the inferior orbital fissure until it reached the trigeminal nerve root for compression in CCT group. Animal behaviors were observed for 4 weeks after operation. Immunohistochemistry of glial fibrillary acidic protein (GFAP), isolectin B4 (IB4), substance P (SP) and calcitonin gene-related peptide (CGRP) were performed in the trigeminal root entry zone (TREZ) and medullary dorsal horn (MDH). RESULTS: The orofacial mechanical allodynia and heat hyperalgesia in the CCT rats were obviously increased after the operation and lasted for 28 days. Increased face-grooming behavior was also observed in the CCT rats and continued for over 21 days, returning to baseline by day 28. Immunohistochemistry for GFAP in the TREZ revealed a progressive extension of astrocytic processes in the ipsilateral TREZ of rats in the CCT group. Furthermore, the IB4 positive immunoreactive nonpeptidergic C-fiber terminals in the MDH were reduced for 4 weeks after the operation. Both SP and CGRP, expressed in the peptidergic C-fiber terminals, were found to be decreased in the ipsilateral MDH of CCT animals after the trigeminal nerve root injury. LIMITATIONS: CCT animal model with a plastic filament only imitated the mechanical compression of the trigeminal root but not to display the complex vascular physiological feature as the microvascular in the TN patient. CONCLUSIONS: The chronic compression of the trigeminal nerve root in rats effectively induced persistent orofacial neuropathic pain behaviors, and it would provide a novel and practical animal model for future research on the pathogenesis of TN.

Origins of endomorphin-2 immunopositive fibers and terminals in the rat medullary dorsal horn.

Endomorphin-2-immunoreactive (EM2-IR) fibers and terminals are densely present in the medullary dorsal horn (MDH) and are key factors in regulating central nociceptive processing. However, the origins of these EM2-IR fibers and terminals remain elusive. It was hypothesized that there were at least three possible origins of the EM2-IR fibers and terminals in the MDH: intrinsic dorsal horn neurons, primary afferent fibers, and projection fibers from higher parts of the brain. Different kinds of measures were employed in the current study to elucidate this hypothesis. After intracerebral ventricle administration of colchicine, no EM2-IR neuronal cell bodies were detected in the MDH, suggesting that there was no intrinsic EM2-IR dorsal horn neuron. Disruption of bilateral primary afferents (exposed to the primary afferent neurotoxin, capsaicin) decreased bilateral EM2 expression but did not eliminate it. Transection of the trigeminal nerve sensory root significantly decreased EM2 expression on the ipsilateral but not on the contralateral MDH. After injecting FluoroGold (FG) into the MDH, FG retrogradely labeled some EM2-IR neurons in the bilateral hypothalamus and nucleus tractus solitarii (NTS), and some of the FG retrogradely labeled neurons in the ipsilateral trigeminal ganglion also showed EM2-immunoreactivities. These results indicate that EM2-IR fibers and terminals in the MDH come not only from ipsilateral primary trigeminal afferents but also from bilateral fibers from the hypothalamus and NTS.