Matrix metalloproteinase mediated degradation of basement membrane proteins in Trembler J neuropathy nerves

Quantitative proteomics unveils known and previously unrecognized alterations in neuropathic nerves

Charcot-Marie-Tooth disease type 1E (CMT1E) is an inherited autosomal dominant peripheral neuropathy caused by mutations in the peripheral myelin protein 22 (PMP22) gene. The identical leucine-to-proline (L16P) amino acid substitution in PMP22 is carried by the Trembler J (TrJ) mouse and is found in CMT1E patients presenting with early-onset disease. Peripheral nerves of patients diagnosed with CMT1E display a complex and varied histopathology, including Schwann cell hyperproliferation, abnormally thin myelin, axonal degeneration, and subaxonal morphological changes. Here, we have taken an unbiased data-independent analysis (DIA) mass spectrometry (MS) approach to quantify proteins from nerves of 3-week-old, age and genetic strain-matched wild-type (Wt) and heterozygous TrJ mice. Nerve proteins were dissolved in lysis buffer and digested into peptide fragments, and protein groups were quantified by liquid chromatography-mass spectrometry (LC-MS). A linear model determined statistically significant differences between the study groups, and proteins with an adjusted p-value of less than 0.05 were deemed significant. This untargeted proteomics approach identified 3759 quality-controlled protein groups, of which 884 demonstrated differential expression between the two genotypes. Gene ontology (GO) terms related to myelin and myelin maintenance confirm published data while revealing a previously undetected prominent decrease in peripheral myelin protein 2. The dataset corroborates the described pathophysiology of TrJ nerves, including elevated activity in the proteasome-lysosomal pathways, alterations in protein trafficking, and an increase in three macrophage-associated proteins. Previously unrecognized perturbations in RNA processing pathways and GO terms were also discovered. Proteomic abnormalities that overlap with other human neurological disorders besides CMT include Lafora Disease and Amyotrophic Lateral Sclerosis. Overall, this study confirms and extends current knowledge on the cellular pathophysiology in TrJ neuropathic nerves and provides novel insights for future examinations. Recognition of shared pathomechanisms across discrete neurological disorders offers opportunities for innovative disease-modifying therapeutics that could be effective for distinct neuropathies.

Novel Matrix Metalloproteinase-9 (MMP-9) Inhibitors in Cancer Treatment

Matrix metalloproteinases (MMPs) belong to a family of zinc-dependent proteolytic metalloenzymes. MMP-9, a member of the gelatinase B family, is characterized as one of the most intricate MMPs. The crucial involvement of MMP-9 in extracellular matrix (ECM) remodeling underscores its significant correlation with each stage of cancer pathogenesis and progression. The design and synthesis of MMP-9 inhibitors is a potentially attractive research area. Unfortunately, to date, there is no effective MMP-9 inhibitor that passes the clinical trials and is approved by the FDA. This review primarily focuses on exploring the diverse strategies employed in the design and advancement of MMP-9 inhibitors, along with their anticancer effects and selectivity. To illuminate the essential structural characteristics necessary for the future design of novel MMP-9 inhibitors, the current narrative review highlights several recently discovered MMP-9 inhibitors exhibiting notable selectivity and potency.

MMP-9 reinforces radiation-induced delayed invasion and metastasis of neuroblastoma cells through second-signaling positive feedback with NFκB via both ERK and IKK activation

Neuroblastoma (NB) progression is branded with hematogenous metastasis and frequent relapses. Despite intensive multimodal clinical therapy, outcomes for patients with progressive disease remain poor, with negligible long-term survival. Therefore, understanding the acquired molecular rearrangements in NB cells with therapy pressure and developing improved therapeutic strategies is a critical need to improve the outcomes for high-risk NB patients. We investigated the rearrangement of MMP9 in NB with therapy pressure, and unveiled the signaling that facilitates NB evolution. Radiation-treatment (RT) significantly increased MMP9 expression/activity, and the induced enzyme activity was persistently maintained across NB cell lines. Furthermore, RT-triggered NFκB transcriptional activity and this RT-induced NFκB were required/adequate for MMP9 maintenance. RT-triggered NFκB-dependent MMP9 actuated a second-signaling feedback to NFκB, facilitating a NFκB-MMP9-NFκB positive feedback cycle (PFC). Critically, MMP9-NFκB feedback is mediated by MMP9-dependent activation of IKKβ and ERK phosphotransferase activity. Beyond its tumor invasion/metastasis function, PFC-dependent MMP9 lessens RT-induced apoptosis and favors survival pathway through the activation of NFκB signaling. In addition, PFC-dependent MMP9 regulates 19 critical molecular determinants that play a pivotal role in tumor evolution. Interestingly, seven of 19 genes possess NFκB-binding sites, demonstrating that MMP9 regulates these molecules by activating NFκB. Collectively, these data suggest that RT-triggered NFκB-dependent MMP9 actuates feedback to NFκB though IKKβ- and ERK1/2-dependent IκBα phosphorylation. This RT-triggered PFC prompts MMP9-dependent survival advantage, tumor growth, and dissemination. Targeting therapy-pressure-driven PFC and/or selective inhibition of MMP9 maintenance could serve as promising therapeutic strategies for treatment of progressive NB.

Hypoxia-induced upregulation of matrix metalloproteinase 9 increases basement membrane degradation by downregulating collagen type IV alpha 1 chain

Hypoxia can cause basement membrane (BM) degradation in tissues. Matrix metalloproteinase 9 (MMP-9) is involved in various human cancers as well as BM degradation by downregulating type IV collagen (COL4). This study investigated the role of MMP-9 in hypoxia-mediated BM degradation in rat bone marrow based on its regulation of collagen type IV alpha 1 chain (COL4A1). Eighty male rats were randomly divided into four groups based on exposure to hypoxic conditions at a simulated altitude of 7,000 m, control (normoxia) and 3, 7, and 10 days of hypoxia exposure. BM degradation in bone marrow was determined by transmission electron microscopy. MMP-9 levels were assessed by western blot and real-time PCR, and COL4A1 levels were assessed by western blot and immunohistochemistry. Microvessels BMs in bone marrow exposed to acute hypoxia were observed by electron microscopy. MMP-9 expression increased, COL4A1 protein expression decreased, and BM degradation occurred in the 10-, 7-, and 3-day hypoxia groups compared with that in the control group (all P < 0.05). Hypoxia increased MMP-9 levels, which in turn downregulated COL4A1, thereby increasing BM degradation. MMP-9 upregulation significantly promoted BM degradation and COL4A1 downregulation. Our results suggest that MMP-9 is related to acute hypoxia-induced BM degradation in bone marrow by regulating COL4A1.

Distinct Changes in Calpain and Calpastatin during PNS Myelination and Demyelination in Rodent Models

Myelin forming around axons provides electrical insulation and ensures rapid and efficient transmission of electrical impulses. Disruptions to myelinated nerves often result in nerve conduction failure along with neurological symptoms and long-term disability. In the central nervous system, calpains, a family of calcium dependent cysteine proteases, have been shown to have a role in developmental myelination and in demyelinating diseases. The roles of calpains in myelination and demyelination in the peripheral nervous system remain unclear. Here, we show a transient increase of activated CAPN1, a major calpain isoform, in postnatal rat sciatic nerves when myelin is actively formed. Expression of the endogenous calpain inhibitor, calpastatin, showed a steady decrease throughout the period of peripheral nerve development. In the sciatic nerves of Trembler-J mice characterized by dysmyelination, expression levels of CAPN1 and calpastatin and calpain activity were significantly increased. In lysolecithin-induced acute demyelination in adult rat sciatic nerves, we show an increase of CAPN1 and decrease of calpastatin expression. These changes in the calpain-calpastatin system are distinct from those during central nervous system development or in acute axonal degeneration in peripheral nerves. Our results suggest that the calpain-calpastatin system has putative roles in myelination and demyelinating diseases of peripheral nerves.

Tridimensional cell culture of dermal fibroblasts promotes exosome-mediated secretion of extracellular matrix proteins

Extracellular matrix (ECM) secretion, deposition and assembly are part of a whole complex biological process influencing the microenvironment and other cellular behaviors. Emerging evidence is attributing a significant role to extracellular vesicles (EVs) and exosomes in a plethora of ECM-associated functions, but the role of dermal fibroblast-derived EVs in paracrine signalling is yet unclear. Herein, we investigated the effect of exosomes isolated from stimulated human dermal fibroblasts. We report that tridimensional (3D) cell culture of dermal fibroblasts promotes secretion of exosomes carrying a large quantity of proteins involved in the formation, organisation and remodelling of the ECM. In our 3D model, gene expression was highly modulated and linked to ECM, cellular migration and proliferation, as well as inflammatory response. Mass spectrometry analysis of exosomal proteins, isolated from 3D cultured fibroblast-conditioned media, revealed ECM protein enrichment, of which many were associated with the matrisome. We also show that the cytokine interleukin 6 (IL-6) is predicted to be central to the signalling pathways related to ECM formation and contributing to cell migration and proliferation. Overall, our data suggest that dermal fibroblast-derived EVs participate in many steps of the establishment of dermis's ECM.

Computational study of effective matrix metalloproteinase 9 (MMP9) targeting natural inhibitors

Object: The present study screened ideal lead natural compounds that could target and inhibit matrix metalloproteinase 9 (MMP9) protein from the ZINC database to develop drugs for clear cell renal cell carcinoma (CCRCC)-targeted treatment.

Methods: Discovery Studio 4.5 was used to compare and screen the ligands with the reference drug, solasodine, to identify ideal candidate compounds that could inhibit MMP9. The LibDock module was used to analyze compounds that could strongly bind to MMP9, and the top 20 compounds determined by the LibDock score were selected for further research. ADME and TOPKAT modules were used to choose the safe compounds from these 20 compounds. The selected compounds were analyzed using the CDOCKER module for molecular docking and feature mapping for pharmacophore prediction. The stability of these compound–MMP9 complexes was analyzed by molecular dynamic simulation. Cell counting kit-8, colony-forming, and scratch assays were used to analyze the anti-CCRCC effects of these ligands.

Results: Strong binding to MMP9 was exhibited by 6,762 ligands. Among the top 20 compounds, sappanol and sventenin exhibited nearly undefined blood–brain barrier level and lower aqueous solubility, carcinogenicity, and hepatotoxicity than the positive control drug, solasodine. Additionally, these compounds exhibited lower potential energies with MMP9, and the ligand–MMP9 complexes were stable in the natural environment. Furthermore, sappanol inhibited CCRCC cell migration and proliferation.

Conclusion: Sappanol and sventenin are safe and reliable compounds to target and inhibit MMP9. Sappanol can CCRCC cell migration and proliferation. These two compounds may give new thought to the targeted therapy for patients with CCRCC.

Role of MMP-9 in epithelial-mesenchymal transition of thyroid cancer

Background

The purpose of this study is to explore the role and mechanism of MMP-9 in the EMT process of thyroid cancer (TC), so as to provide a basis for clinical exploration of invasion and metastasis process of TC, looking for biological markers of tumor metastasis and molecular intervention therapy.

Methods

Western blot and RT-PCR were employed to detect the expression of MMP-9 in human normal thyroid cell line HT-ori3 and human TC cell lines IHH-4 (PTC), FTC-133, and 8505C. Expression levels of EMT-related markers: epithelial cell marker E-cadherin and stromal cell marker Vimentin in TGF-1-induced TC cell lines were detected by Western blot and RT-PCR, respectively. The effects of MMP-9 downregulation on cell invasion and metastasis were investigated by wound-healing assay and cell invasion experiment.

Results

The protein and mRNA expression levels of MMP-9 in TC cell lines were increased compared with the human normal thyroid cell line HT-ori3. When TGF-β1 was added, the expression of EMT and Vimentin increased while the expression of E-cadherin decreased. Compared with the control group, the TC cells stably transfected with MMP-9 shRNA showed inhibited EMT, decreased Vimentin expression, and increased E-cadherin expression. The induction of TGF-β1 did not promote the occurrence of EMT in TC cells which were stably transformed with MMP-9 shRNA. The addition of TGF-β1 to TC cells increased the ability of the cells to migrate and invade. Compared with the control group, the migration and invasion ability of TC cells stably transfected with MMP-9 shRNA was significantly reduced, and the induction of TGF-β1 could not restore the migration and invasion ability of cells without MMP-9.

Conclusions

In conclusion, we found that MMP-9 can be used as a biomarker for TC, which can promote the EMT process of TGF-β1 induced TC, and thus affecting the cell migration and invasion ability.

Chronic Hypoxia-Induced Microvessel Proliferation and Basal Membrane Degradation in the Bone Marrow of Rats Regulated through the IL-6/JAK2/STAT3/MMP-9 Pathway

Chronic hypoxia (CH) is characterized by long-term hypoxia that is associated with microvessel proliferation and basal membrane (BM) degradation in tissues. The IL-6/JAK2/STAT3/MMP-9 pathway has been described in a variety of human cancers and plays an essential role in microvessel proliferation and BM degradation. Therefore, this study investigated the role of the IL-6/JAK2/STAT3/MMP-9 pathway in hypoxia-mediated microvessel proliferation and BM degradation in the rat bone marrow. Eighty pathogen-free Sprague Dawley male rats were randomly divided into four groups (20 per group)—control group, CH group (exposed to hypoxia in a hypobaric chamber at a simulated altitude of 5000 m for 28 d), CH + STAT3 inhibitor group (7.5 mg/kg/d), and CH + DMSO group. Microvessel density (MVD) and BM degradation in the bone marrow were determined by immunofluorescence staining and transmission electron microscopy. Serum IL-6 levels were assessed by enzyme-linked immunosorbent assay (ELISA), and the levels of P-JAK2, P-STAT3, and MMP-9 were assessed by western blot analysis and real-time reverse transcription PCR (RT-PCR). Hypoxia increased serum IL-6 levels, which in turn increased JAK2 and STAT3 phosphorylation, which subsequently upregulated MMP-9. Overexpression of MMP-9 significantly promoted the elevation of MVD and BM degradation. Inhibition of STAT3 using an inhibitor, SH-4-54, significantly downregulated MMP-9 expression and decreased MVD and BM degradation. Surprisingly, STAT3 inhibition also decreased serum IL-6 levels and JAK2 phosphorylation. Our results suggest that the IL-6/JAK2/STAT3/MMP-9 pathway might be related to CH-induced microvessel proliferation and BM degradation in the bone marrow.

Rhodiola crenulata Suppresses High Glucose-Induced Matrix Metalloproteinase Expression and Inflammatory Responses by Inhibiting ROS-Related HMGB1-TLR4 Signaling in Endothelial Cells

Rhodiola crenulata, a popular folk medicine for anti-altitude sickness in Tibet, has been shown to have protective effects against high glucose (HG)-induced endothelial cell dysfunction in human umbilical vein endothelial cells (HUVECs). However, its mechanisms of action are unclear. Here, we aimed to examine the effects and the mechanisms of action of Rhodiola crenulata extract (RCE) on matrix metalloproteinases (MMPs) and inflammatory responses under HG conditions. HUVECs were pretreated with RCE or untreated and then exposed to 33[Formula: see text]mM glucose medium for 24[Formula: see text]h. The levels of oxidative stress markers, MMPs, endogenous tissue inhibitors of MMPs (TIMPs), and adhesion molecules were determined. Zymography assays were also carried out. We found that RCE significantly decreased HG-induced increases in reactive oxygen species (ROS) and activation of MAPK and NF-[Formula: see text]B pathways. In addition, RCE not only significantly reduced the expression and activities of MMPs but also upregulated TIMP protein levels. Consistently, HG-induced activation of the toll-like receptor 4 (TLR4)/myeloid differentiation primary response protein (MyD88) signaling pathway, intracellular adhesion molecule-1 (ICAM-1), vascular adhesion molecule-1 (VCAM-1), and high mobility group box 1 (HMGB1) as well as endothelial cell apoptosis was inhibited by RCE treatment. RCE exerts protective effects on endothelial cells against HG insult, partially by suppressing the HMGB1/TLR4 axis. These findings indicate that Rhodiola crenulata may be a potential therapeutic agent for diabetes-associated vascular diseases.

Comparison of three congruent patient-specific cell types for the modelling of a human genetic Schwann-cell disorder

Patient-specific human induced pluripotent stem cells (hiPSCs) hold great promise for the modelling of genetic disorders. However, these cells display wide intra-individual and inter-individual variations in gene expression, making it challenging to distinguish true-positive and false-positive phenotypes. Also, data from hiPSC phenotypes and from human embryonic stem cells (hESCs) harbouring the same disease mutation are lacking. Here, we report a comparison of molecular, cellular and functional characteristics of three congruent patient-specific cell types ― hiPSCs, hESCs, and direct lineage-converted cells ― derived from currently available differentiation and direct-reprogramming technologies, for the modelling of Charcot Marie Tooth 1A, a human genetic Schwann-cell disorder featuring a 1.4 megabase chromosomal duplication. In particular, we find that the chemokines CXCL1 and MCP1 are commonly upregulated in all three congruent models and in clinical patient samples. The development of congruent models of a single genetic disease by using somatic cells from a common patient will facilitate the search for convergent phenotypes.

Matrix Metalloproteinase-9 (MMP-9) as a Cancer Biomarker and MMP-9 Biosensors: Recent Advances

As one of the most widely investigated matrix metalloproteinases (MMPs), MMP-9 is a significant protease which plays vital roles in many biological processes. MMP-9 can cleave many extracellular matrix (ECM) proteins to regulate ECM remodeling. It can also cleave many plasma surface proteins to release them from the cell surface. MMP-9 has been widely found to relate to the pathology of cancers, including but not limited to invasion, metastasis and angiogenesis. Some recent research evaluated the value of MMP-9 as biomarkers to various specific cancers. Besides, recent research of MMP-9 biosensors discovered various novel MMP-9 biosensors to detect this enzyme. In this review, some recent advances in exploring MMP-9 as a biomarker in different cancers are summarized, and recent discoveries of novel MMP-9 biosensors are also presented.

Matrix metalloproteinase-2 and its correlation with basal membrane components laminin-5 and collagen type IV in paediatric burn patients measured with Surface Plasmon Resonance Imaging (SPRI) biosensors

The purpose of this study was the determination of matrix metalloproteinase-2 and its correlation with basal membrane components laminin-5 and collagen type IV in the blood plasma of burn patients measured with Surface Plasmon Resonance Imaging (SPRI) biosensors.

MATERIAL AND METHODS

31 children scalded by hot water who were managed at the Department of Paediatric Surgery between 2014-2015, after primarily presenting with burns in 4-20% TBSA were included into the study (age 9 months up to 14 years, mean age 2,5+1 years). There were 10 girls and 21 boys. Venous blood samples were drawn 2-6h, and 12-16h after the thermal injury, and on the subsequent days 3, 5 and 7. The matrix metalloproteinase-2, collagen type IV and laminin-5 concentrations were assessed using Surface Plasmon Resonance Imaging by the investigators blinded to the other data.

RESULTS

The MMP-2, laminin-5 and collagen type IV concentrations in the blood plasma of patients with burns, were highest 12-16h after thermal injury, the difference was statistically significant. The MMP-2, laminin-5 and collagen type IV concentrations measured 3 days, 5 days and 7 days after the thermal injury, slowly decreased over time, and on the 7th day reached the normal range, when compared with the concentration measured in controls.

CONCLUSION

Current work is the first follow-up study regarding MMP-2 in burns. MMP-2, laminin-5 and collagen type IV levels were elevated early after burn injury in the plasma of studied patients, and were highest 12-16h after the injury. MMP-2, laminin-5 and collagen type IV levels were not proportional to the severity of the burn. We believe in the possibility that the gradual decrease of MMP-2, collagen type IV and laminin-5 concentrations could be connected with the process of healing, but to prove it, more investigation is needed in this area. The SPR imaging biosensor is a good diagnostic tool for determination of MMP-2, laminin-5 and collagen type IV in blood plasma of patients with burns.

Immunofibrogenic Gene Expression Patterns in Tanzanian Children with Ocular Chlamydia trachomatis Infection, Active Trachoma and Scarring: Baseline Results of a 4-Year Longitudinal Study

Trachoma, caused by Chlamydia trachomatis, is the world's leading infectious cause of blindness and remains a significant public health problem. Much of trachomatous disease pathology is thought to be caused indirectly by host cellular and immune responses, however the immune response during active trachoma and how this initiates progressive scarring is not clearly understood. Defining protective vs. pathogenic immune response to C. trachomatis is important for vaccine design and evaluation. This study reports the baseline results of a longitudinal cohort of Tanzanian children, who were monitored for 4 years in order to determine the immunofibrogenic and infectious correlates of progressive scarring trachoma. In this cohort baseline, 506 children aged 6-10 years were assessed for clinical signs, infection status and the expression of 91 genes of interest prior to mass azithromycin administration for trachoma control. C. trachomatis was detected using droplet digital PCR and gene expression was measured using quantitative real-time PCR. The prevalence of follicles, papillary inflammation and scarring were 33.6, 31.6, and 28.5%, respectively. C. trachomatis was detected in 78/506 (15.4%) individuals, 62/78 of whom also had follicles. C. trachomatis infection was associated with a strong upregulation of IFNG and IL22, the enrichment of Th1 and NK cell pathways and Th17 cell-associated cytokines. In individuals with inflammation in the absence of infection the IFNG/IL22 and NK cell response was reduced, however, pro-inflammatory, growth and matrix factors remained upregulated and mucins were downregulated. Our data suggest that, strong IFNG/IL22 responses, probably related to Th1 and NK cell involvement, is important for clearance of C. trachomatis and that the residual pro-inflammatory and pro-fibrotic phenotype that persists after infection might contribute to pathological scarring. Interestingly, females appear more susceptible to developing papillary inflammation and scarring than males, even at this young age, despite comparable levels of C. trachomatis infection. Females also had increased expression of a number of IFNγ pathway related genes relative to males, suggesting that overexpression of this pathway in response to infection might contribute to more severe scarring. Longitudinal investigation of these factors will reveal their relative contributions to protection from C. trachomatis infection and development of scarring complications.

Tissue remodeling after interference RNA mediated knockdown of transthyretin in a familial amyloidotic polyneuropathy mouse model

Transthyretin (TTR) deposition in the peripheral nervous system is the hallmark of familial amyloidotic polyneuropathy (FAP). Currently, liver transplantation is the only available treatment to halt the progression of clinical symptoms; however, due to the limitations of this procedure, development of alternative therapeutic strategies is of utmost importance. In this regard, interference RNA (RNAi) targeting TTR is currently in phase III clinical development. To dissect molecular changes occurring in dorsal root ganglia (DRG) upon RNAi-mediated knockdown of TTR, we treated both chronically and acutely an FAP mouse model, in different stages of disease. Our data show that inhibition of TTR expression by the liver with RNAi reverse TTR deposition in DRG, decrease matrix metalloproteinase-2 (MMP-2) protein levels in plasma, inhibit Mmp-2 gene expression and downregulate MMP-9 activity in DRG, indicating extracellular matrix remodeling. Furthermore, protein levels of MMP-2 were found upregulated in plasma samples from FAP patients indicating that MMP-2 might be a novel potential biomarker for FAP diagnosis. Collectively, our data show that silencing TTR liver synthesis in vivo can modulate TTR-induced pathology in the peripheral nervous system and highlight the potential of MMP-2 as a novel disease biomarker.

Transcriptome Display During Testicular Differentiation of Channel Catfish (Ictalurus punctatus) as Revealed by RNA-Seq Analysis

Channel catfish (Ictalurus punctatus) has been recognized as a dominant freshwater aquaculture species in the United States. It is also a suitable model for studying the mechanisms of sex determination and differentiation because of its sexual plasticity and exhibition of both genetic and environmental sex determination. The testicular differentiation in male channel catfish normally starts between 90 and 102 days postfertilization (dpf), while the ovarian differentiation starts early from 19 dpf. As such, efforts to better understand the postponed testicular development at the molecular level are needed. Toward that end, we conducted transcriptomic comparison of gene expression of male and female gonads at 90, 100, and 110 dpf using high-throughput RNA-Seq. Transcriptomic profiles of male gonads on 90 and 100 dpf exhibited high similarities except for a small number of significantly up-regulated genes that were involved in development of germ cell-supporting somatic cells, while drastic changes were observed during 100-110 dpf, with a group of highly up-regulated genes that were involved in germ cells development, including nanog and pou5f1 Transcriptomic comparison between testes and ovaries identified male-preferential genes, such as gsdf, cxcl12, as well as other cytokines mediated the development of the gonad into a testis. Co-expression analysis revealed highly correlated genes and potential pathways underlying germ cell differentiation and spermatogonia stem cell development. The candidate genes and pathways identified in this study set the foundation for further studies on sex determination and differentiation in catfish as well as other teleosts.

The Role of Collagens in Peripheral Nerve Myelination and Function

In the peripheral nervous system, myelin is formed by Schwann cells, which are surrounded by a basal lamina. Extracellular matrix (ECM) molecules in the basal lamina play an important role in regulating Schwann cell functions, including adhesion, survival, spreading, and myelination, as well as in supporting neurite outgrowth. Collagens are a major component of ECM molecules, which include 28 types that differ in structure and function. A growing body of evidence suggests that collagens are key components of peripheral nerves, where they not only provide a structural support but also affect cell behavior by triggering intracellular signals. In this review, we will summarize the main properties of collagen family, discuss the role of extensively studied collagen types (collagens IV, V, VI, and XV) in Schwann cell function and myelination, and provide a detailed overview of the recent advances with respect to these collagens in peripheral nerve function.

Biochemical characterization of protein quality control mechanisms during disease progression in the C22 mouse model of CMT1A

Charcot–Marie–Tooth disease type 1A (CMT1A) is a hereditary demyelinating neuropathy linked with duplication of the peripheral myelin protein 22 (PMP22) gene. Transgenic C22 mice, a model of CMT1A, display many features of the human disease, including slowed nerve conduction velocity and demyelination of peripheral nerves. How overproduction of PMP22 leads to compromised myelin and axonal pathology is not fully understood, but likely involves subcellular alterations in protein homoeostatic mechanisms within affected Schwann cells. The subcellular response to abnormally localized PMP22 includes the recruitment of the ubiquitin–proteasome system (UPS), autophagosomes and heat-shock proteins (HSPs). Here we assessed biochemical markers of these protein homoeostatic pathways in nerves from PMP22-overexpressing neuropathic mice between the ages of 2 and 12 months to ascertain their potential contribution to disease progression. In nerves of 3-week-old mice, using endoglycosidases and Western blotting, we found altered processing of the exogenous human PMP22, an abnormality that becomes more prevalent with age. Along with the ongoing accrual of misfolded PMP22, the activity of the proteasome becomes compromised and proteins required for autophagy induction and lysosome biogenesis are up-regulated. Moreover, cytosolic chaperones are consistently elevated in nerves from neuropathic mice, with the most prominent change in HSP70. The gradual alterations in protein homoeostatic response are accompanied by Schwann cell de-differentiation and macrophage infiltration. Together, these results show that while subcellular protein quality control mechanisms respond appropriately to the presence of the overproduced PMP22, with aging they are unable to prevent the accrual of misfolded proteins.

In peripheral nerves of neuropathic C22 mice the frequency of cytosolic PMP22 aggregates increases with age, which elicits a response from protein quality control mechanisms. The combined effects of aging and neuropathic genotype exacerbate disease progression leading to nerve defects.

Long-term analyses of innervation and neuromuscular integrity in the Trembler-J mouse model of Charcot-Marie-Tooth disease

A large fraction of hereditary demyelinating neuropathies, classified as Charcot-Marie-Tooth disease type 1A, is associated with misexpression of peripheral myelin protein 22. In this study, we characterized morphologic and biochemical changes that occur with diseaseprogression in neuromuscular tissue of Trembler-J mice, a spontaneous rodent model of Charcot-Marie-Tooth disease type 1A. Using age-matched, 2- and 10-month-old, wild-type and Trembler-J mice, we observed neuromuscular deficits that progress from distal to proximal regions. The impairments in motor performance are underlined by degenerative events at distal nerve segments and structural alterations at nerve-muscle synapses. Furthermore, skeletal muscle of affected mice showed reduced myofiber diameter, increased expression of the muscle atrophy marker muscle ring-finger protein 1, and fiber type switching. A dietary intervention of intermittent fasting attenuated these progressive changes and supported distal nerve myelination and neuromuscular junction integrity. In addition to the well-characterized demyelination aspects of this model, our investigations identified distinct degenerative events in distal nerves and muscle of affected neuropathic mice. Therefore, therapeutic studies aimed at slowing or reversing the neuropathic features of these disorders should include the examination of muscle tissue, as well as neuromuscular contact sites.

Rabbit model of radiation-induced lung injury

OBJECTIVE

To explore the feasibility of establishing an animal model of chronic radiation-induced lung injury.

METHODS

Twenty-eight New Zealand white rabbits were randomly divided into 3 groups (the right lung irradiation group, the whole lung irradiation group and the control group). Animal model of radiation-induced lung injury was established by high-does radiotherapy in the irradiation groups, then all rabbits underwent CT and pathological examinations at 1, 2, 4, 8, 12, 16 weeks, respectively after radiation.

RESULTS

Within 4 weeks of irradiation, some rabbits in the right lung irradiation group and whole lung irradiation group died. CT and pathological examinations all showed acute radiation pneumonitis. At 8-12 weeks after irradiation, CT scanning showed ground glass samples signs, patchy shadows and fibrotic stripes. Pathological examination showed the fibrosis pulmonary alveolar wall thickened obviously.

CONCLUSIONS

The clinical animal model of chronic radiation-induced lung injury which corresponds to practical conditions in clinic can be successfully established.

Dietary restriction supports peripheral nerve health by enhancing endogenous protein quality control mechanisms

The peripheral nervous system (PNS) comprises of an extensive network of connections that convey information between the central nervous system (CNS) and peripheral organs. Long myelinated nerve fibers are particularly susceptible to age-related changes, as maintenance of the insulating glial membrane requires extensive synthesis and processing of many proteins. In rodent models, peripheral demyelination caused by genetic risk factors or by normal aging are attenuated by intermittent fasting (IF) or calorie restriction (CR) supporting a role for dietary intervention in preserving neural function. This review will summarize recent studies examining mechanisms by which life-long CR or extended IF supports peripheral nerve health.

Myelinating and demyelinating phenotype of Trembler-J mouse (a model of Charcot-Marie-Tooth human disease) analyzed by atomic force microscopy and confocal microscopy

The accumulation of misfolded proteins is associated with various neurodegenerative conditions. Mutations in PMP-22 are associated with the human peripheral neuropathy, Charcot-Marie-Tooth Type 1A (CMT1A). PMP-22 is a short-lived 22 kDa glycoprotein, which plays a key role in the maintenance of myelin structure and compaction, highly expressed by Schwann cells. It forms aggregates when the proteasome is inhibited or the protein is mutated. This study reports the application of atomic force microscopy (AFM) as a detector of profound topographical and mechanical changes in Trembler-J mouse (CMT1A animal model). AFM images showed topographical differences in the extracellular matrix and basal lamina organization of Tr-J/+ nerve fibers. The immunocytochemical analysis indicated that PMP-22 protein is associated with type IV collagen (a basal lamina ubiquitous component) in the Tr-J/+ Schwann cell perinuclear region. Changes in mechanical properties of single myelinating Tr-J/+ nerve fibers were investigated, and alterations in cellular stiffness were found. These results might be associated with F-actin cytoskeleton organization in Tr-J/+ nerve fibers. AFM nanoscale imaging focused on topography and mechanical properties of peripheral nerve fibers might provide new insights into the study of peripheral nervous system diseases.

Lifelong calorie restriction alleviates age-related oxidative damage in peripheral nerves

Aging is associated with protein damage and imbalance in redox status in a variety of cells and tissues, yet little is known about the extent of age-related oxidative stress in the peripheral nervous system. Previously, we showed a drastic decline in the expression of glial and neuronal proteins in myelinated peripheral nerves with age, which is significantly ameliorated by lifelong calorie restriction. The age-related decline in functional molecules is associated with alterations in cellular protein homeostatic mechanisms, which could lead to a buildup of damaged, aggregated proteins. To determine the extent of oxidative damage within myelinated peripheral nerves, we studied sciatic nerves from rats of four different ages (8, 18, 29, and 38 months) maintained on an ad libitum or a 40% calorie-restricted diet. We found a prominent accumulation of polyubiquitinated substrates with age, which are associated with the conglomeration of distended lysosomes and lipofuscin adducts. The occurrence of these structures is notably less frequent within nerves of age-matched rodents kept on a lifelong reduced calorie diet. Markers for lipid peroxidation, inflammation, and immune cell infiltration are all elevated in nerves of ad libitum-fed rats, whereas food restriction is able to attenuate such deleterious processes with age. Together these results show that dietary restriction is an efficient means of defying age-related oxidative damage and maintaining a younger state in peripheral nerves.

Complement inhibition accelerates regeneration in a model of peripheral nerve injury

Complement (C) activation is a crucial event in peripheral nerve degeneration but its effect on the subsequent regeneration is unknown. Here we show that genetic deficiency of the sixth C component, C6, accelerates axonal regeneration and recovery in a rat model of sciatic nerve injury. Foot-flick test and Sciatic Function Index monitored up to 5 weeks post-injury showed a significant improvement of sensory and motor function in the C6 deficient animals compared to wildtypes. Retrograde tracing experiments showed a significantly higher number of regenerated neurons at 1 week post-injury in C6 deficient rats than wildtypes. Pathology showed improved nerve regeneration in tibials of C6 deficient animals compared to wildtypes. Reconstitution with purified human C6 protein re-established the wildtype phenotype whereas pharmacological inhibition of C activation with soluble C receptor 1 (sCR1) facilitated recovery and improved pathology similarly to C6 deficient animals. We suggest that a destructive C-mediated event during nerve degeneration hampers the subsequent regenerative process. These findings provide a rationale for the testing of anti-complement agents in human nerve injury.

Intermittent fasting alleviates the neuropathic phenotype in a mouse model of Charcot-Marie-Tooth disease

Charcot-Marie-Tooth type 1A (CMT1A) neuropathies linked to the misexpression of peripheral myelin protein 22 (PMP22) are progressive demyelinating disorders of the peripheral nervous system. In this study we asked whether dietary restriction by intermittent fasting (IF) could alleviate the neuropathic phenotype in the Trembler J (TrJ) mouse model of CMT1A. Our results show that neuropathic mice kept on a five month long IF regimen had improved locomotor performance compared to ad libitum (AL) fed littermates. The functional benefits of this dietary intervention are associated with an increased expression of myelin proteins combined with a thicker myelin sheath, less redundant basal lamina, and a reduction in aberrant Schwann cell proliferation. These morphological improvements are accompanied by a decrease in PMP22 protein aggregates, and enhanced expression of cytosolic chaperones and constituents of the autophagy-lysosomal pathway. These results indicate that dietary restriction is beneficial for peripheral nerve function in TrJ neuropathic mice, as it promotes the maintenance of locomotor performance.

Developmental abnormalities in the nerves of peripheral myelin protein 22-deficient mice

Peripheral myelin protein 22 (PMP22) is a tetraspan glycoprotein whose misexpression is associated with a family of hereditary peripheral neuropathies. In a recent report, we have characterized a novel PMP22-deficient mouse model in which the first two coding exons were replaced by the lacZ reporter. To investigate further the myelin abnormalities in the absence of PMP22, sciatic nerves and dorsal root ganglion (DRG) neuron explant cultures from PMP22-deficient mice were studied at various stages of myelination. Throughout the first 3 months of postnatal development, myelin protein and beta4 integrin levels are dramatically reduced, whereas p75 and beta1 integrin remain elevated. By immunostaining, the distributions of several glial proteins, including beta4 integrin, the voltage-gated potassium channel Kv1.1, and E-cadherin, are altered. Schwann cells from PMP22-deficient mice are able to produce limited amounts of myelin in DRG explant cultures, yet the internodal segments are dramatically fewer and shorter. The comparison of PMP22-deficient mice with other PMP22 mutant models reveals that the decrease in beta4 integrin is specific to an absence of PMP22. Furthermore, whereas lysosome-associated membrane protein 1 and ubiquitin are notably up-regulated in nerves of PMP22-deficient mice, heat shock protein 70 levels remain constant or decrease compared with wild-type or PMP22 mutant samples. Together these results support a role for PMP22 in the early events of peripheral nerve myelination. Additionally, although myelin abnormalities are a commonality among PMP22 neuropathic models, the underlying subcellular mechanisms are distinct and depend on the specific genetic abnormality.

Modulation of extracellular matrix components by metalloproteinases and their tissue inhibitors during degeneration and regeneration of rat sural nerve

The success of peripheral nervous system regeneration has been associated with changes on the microenvironment, particularly on the extracellular matrix (ECM) components. In the present study we analyzed by indirect immunohistochemistry, electron microscopy and Western blotting, the distribution of ECM components, metalloproteinases (MMPs) and their tissue inhibitors (TIMPs), during Wallerian degeneration (WD) and nerve regeneration (2nd, 7th and 21st days after injury) on crushed rat sural nerves. Our results showed that laminin alpha3-chain and alpha2-chain are over expressed during the early stages of degeneration and regeneration respectively, whereas type IV collagen expression increased progressively after crush. On the other hand, the expression of chondroitin sulfate was down regulated during the early stages of degeneration, returning progressively to normal values during nerve regeneration. The expression of MMP-3 was almost normal immediately after lesion, and then reduced progressively achieving the smallest expression at 21 days after crush; on the contrary, the expression of MMP-7 increased significantly immediately after crush (2nd day) returning to normal values afterwards. TIMP-1 and TIMP-2 were over expressed at the beginning of WD, returning progressively to normal values after that. These results indicate that the modifications of ECM components, which are favorable for nerve regeneration, are correlated with changes on the balance between MMPs and TIMPs.

TNFalpha-induced MMP-9 promotes macrophage recruitment into injured peripheral nerve

Matrix metalloproteinase-9 (MMP-9) is an extracellular protease that is induced hours after injury to peripheral nerve. This study shows that MMP-9 gene deletion and neutralization with MMP-9 antibody reduce macrophage content in injured wild-type nerves. In mice with delayed Wallerian degeneration (WldS), MMP-9 and tumor necrosis factor alpha (TNFalpha) decline in association with the reduced macrophage recruitment to injured nerve that characterizes this strain of mice. We further determined that TNFalpha acts as an MMP-9 inducer by establishing increased MMP-9 levels after TNFalpha injection in rat sciatic nerve in vivo and primary Schwann cells in vitro. We found reduced MMP-9 expression in crushed TNFalpha knockout nerves that was rescued with exogenous TNFalpha. Finally, local application of MMP-9 on TNFalpha-/- nerves increased macrophage recruitment to the lesion. These data suggest that TNFalpha lies upstream of MMP-9 in the pathway of macrophage recruitment to injured peripheral nerve.

Experimental Charcot-Marie-Tooth type 1A: a cDNA microarrays analysis

To reveal the spectrum of genes that are modulated in Charcot-Marie-Tooth neuropathy type 1A (CMT1A), which is due to overexpression of the gene coding for the peripheral myelin protein 22 (pmp22), we performed a cDNA microarray experiment with cDNA from sciatic nerves of a rat model of the disease. In homozygous pmp22 overexpressing animals, we found a significant down-regulation of 86 genes, while only 23 known genes were up-regulated, suggesting that the increased dosage of pmp22 induces a general down-regulation of gene expression in peripheral nerve tissue. Classification of the modulated genes into functional categories leads to the identification of some pathways altered by overexpression of pmp22. In particular, a selective down-regulation of the ciliary neurotrophic factor transcript and of genes coding for proteins involved in cell cycle regulation, for cytoskeletal components and for proteins of the extracellular matrix, was observed. Cntf expression was further studied by real-time PCR and ELISA technique in pmp22 transgenic sciatic nerves, human CMT1A sural nerve biopsies, and primary cultures of transgenic Schwann cells. According to the results of cDNA microarray analysis, a down-regulation of cntf, both at the mRNA and protein level, was found in all the conditions tested. These results are relevant to reveal the molecular function of PMP22 and the pathogenic mechanism of CMT1A. In particular, finding a specific reduction of cntf expression in CMT1A Schwann cells suggests that overexpression of pmp22 significantly affects the ability of Schwann cells to offer a trophic support to the axon, which could be a factor, among other, responsible for the development of axonal atrophy in human and experimental CMT1A.

Distinct disease mechanisms in peripheral neuropathies due to altered peripheral myelin protein 22 gene dosage or a Pmp22 point mutation

Point mutations affecting PMP22 can cause hereditary demyelinating and dysmyelinating peripheral neuropathies. In addition, duplication and deletion of PMP22 are associated with Charcot-Marie-Tooth disease Type 1A (CMT1A) and Hereditary Neuropathy with Liability to Pressure Palsy (HNPP), respectively. This study was designed to elucidate disease processes caused by misexpression of Pmp22 and, at the same time, to gain further information on the controversial molecular function of PMP22. To this end, we took advantage of the unique resource of a set of various Pmp22 mutant mice to carry out comparative expression profiling of mutant and wild-type sciatic nerves. Tissues derived from Pmp22-/- ("knockout"), Pmp22tg (increased Pmp22 copy number), and Trembler (Tr; point mutation in Pmp22) mutant mice were analyzed at two developmental stages: (i) at postnatal day (P)4, when normal myelination has just started and primary causative defects of the mutations are expected to be apparent, and (ii) at P60, with the goal of obtaining information on secondary disease effects. Interestingly, the three Pmp22 mutants exhibited distinct profiles of gene expression, suggesting different disease mechanisms. Increased expression of genes involved in cell cycle regulation and DNA replication is characteristic and specific for the early stage in Pmp22-/- mice, supporting a primary function of PMP22 in the regulation of Schwann cell proliferation. In the Tr mutant, a distinguishing feature is the high expression of stress response genes. Both Tr and Pmp22tg mice show strongly reduced expression of genes important for cholesterol synthesis at P4, a characteristic that is common to all three mutants at P60. Finally, we have identified a number of candidate genes that may play important roles in the disease process or in myelination per se.

Up-regulation of the extracellular matrix remodeling genes, biglycan, neutrophil gelatinase-associated lipocalin, and matrix metalloproteinase-9 in familial amyloid polyneuropathy

Familial amyloid polyneuropathy (FAP) is characterized by extracellular deposition of transthyretin (TTR) aggregates and amyloid fibrils, particularly in the peripheral nervous system (PNS) and is accompanied with changes in connective tissue. Given the invasiveness of nerve biopsy, FAP salivary glands (SGs) were used in microarray analysis; biglycan and neutrophil gelatinase-associated lipocalin (NGAL), two genes related to extracellular matrix (ECM) remodeling were overexpressed in FAP. Results were validated by RT-PCR and immunohistochemistry both in SG and in nerve biopsies of different stages of disease progression. Matrix metalloproteinase-9 (MMP-9), which exists as a complex with NGAL, was also increased in FAP and in vitro degraded TTR aggregates and fibrils; however in the presence of serum amyloid P, a universal amyloid component, TTR fibrils became resistant to MMP-9 proteolysis. Biglycan, NGAL, and MMP-9 are transcriptionally up-regulated by NF-kappaB, a transcription factor that is activated in FAP nerves and SG. Given the relationship between inflammation and ECM remodeling, and the increase of proinflammatory cytokines in FAP, IL-10 expression in FAP nerves was investigated; IL-10 increased after fibril deposition, suggesting a balance between proinflammatory and anti-inflammatory mechanisms. Changes in ECM-related proteins and inflammatory events may be relevant for therapy in FAP and other neurodegenerative disorders.

The temporospatial expression of peripheral myelin protein 22 at the developing blood-nerve and blood-brain barriers

Peripheral myelin protein 22 (PMP22), also known as growth arrest-specific gene 3 (gas3), is a tetraspan membrane protein whose misexpression is associated with demyelinating peripheral neuropathies. Although the function of PMP22 in Schwann cells is unknown, the protein is found at intercellular junctions of various epithelia and endothelia. To begin to elucidate the role of PMP22 at cell junctions, we examined the temporal expression and protein localization during development and maturation of the rat blood-nerve barrier (BNB) and blood-brain barrier (BBB). Developing and adult rat sciatic nerves and brains were coimmunostained for PMP22 and known junctional proteins including zonula occludens-1 (ZO-1), occludin, and claudin-5. Prior to the maturation of the BNB and BBB and detection of the tight junction protein occludin, PMP22 is present at ZO-1 positive endothelial junctions of the sciatic nerve and brain cortex. The subcellular localization of PMP22 in cultured brain endothelia was confirmed by internalization with ZO-1 after EGTA-induced disruption of cell junctions. In choroid epithelia, PMP22 is detected along with occludin and ZO-1 as early as embryonic day 15 (E15). In agreement, PMP22 message is elevated in P1 rat brain microvasculature and choroid epithelia, compared with total cortex. Additionally, neuroepithelial cell junctions in the embryonic rat brain are immunoreactive for PMP22, ZO-1, and beta-catenin but not occludin. Together, these studies identify PMP22 as an early constituent of intercellular junctions in the developing and mature rat BNB and BBB.

Macrophages contribute to the maintenance of stable regenerating neurites following peripheral nerve injury

Normal adult uninjured nerve is unable to support axonal regeneration. We have studied the mechanisms underlying the regeneration of peripheral nerve by culturing adult mouse dorsal root ganglia (DRG) explants on unfixed, longitudinal cryosections of either the uninjured sciatic nerve or the distal segment of the transected sciatic nerve. We found that, initially, DRG grew vigorously on cryosections of both uninjured and postinjury sciatic nerves. However, the neurites began to degenerate shortly after contact with the uninjured nerve, whereas those growing on postinjury nerve substrate remained healthy for up to 9 days in culture. This ability to support stable outgrowth peaked at 8 days, gradually decreased by 10 days, and disappeared by 20 days after injury. Macrophages appeared in the distal segment by 4 days postinjury and had infiltrated its entire length by 8 days. Uninjured nerve cryosections could be rendered supportive of stable outgrowth by preincubation with macrophage-conditioned medium or by brief trypsinization. The activity of the macrophage-conditioned medium was augmented upon activation of macrophages. Together these findings suggest that the environment of the sciatic nerve undergoes a transformation during Wallerian degeneration such that it becomes transiently supportive of the stable outgrowth of neurites. This transformation may be mediated by a proteolytic activity, generated by activated macrophages, that removes a putative "degeneration signal" protein normally present in the adult nerve and thus contributes to the maintenance of stable regenerating neurites.