fibrin and Nerve-Degeneration

Neuronal loss, a key substrate of irreversible disability in multiple sclerosis (MS), is a recognized feature of MS cortical pathology of which the cause remains unknown. Fibrin(ogen) deposition is neurotoxic in animal models of MS, but has not been evaluated in human progressive MS cortex. The aim of this study was to investigate the extent and distribution of fibrin(ogen) in progressive MS cortex and elucidate its relationship with neurodegeneration.. A postmortem cohort of pathologically confirmed MS (n = 47) and control (n = 10) cases was used. The extent and distribution of fibrin(ogen) was assessed and related to measures of demyelination, inflammation, and neuronal density. In a subset of cases (MS, n = 20; control, n = 10), expression of plasminogen activator inhibitor 1 (PAI-1), a key enzyme in the fibrinolytic cascade, was assessed and related to the extent of fibrin(ogen).. Motor cortical fibrin(ogen) deposition was significantly over-represented in MS compared to control cases in all compartments studied (ie, extracellular [p = 0.001], cell body [p = 0.003], and neuritic/glial-processes [p = 0.004]). MS cases with high levels of extracellular fibrin(ogen) had significantly upregulated PAI-1 expression in all cortical layers assessed (p < 0.05) and reduced neuronal density (p = 0.017), including in the functionally-relevant layer 5 (p = 0.001).. For the first time, we provide unequivocal evidence that fibrin(ogen) is extensively deposited in progressive MS motor cortex, where regulation of fibrinolysis appears perturbed. Progressive MS cases with severe fibrin(ogen) deposition have significantly reduced neuronal density. Future studies are needed to elucidate the provenance and putative neurotoxicity of fibrin(ogen), and its potential impact on clinical disability. Ann Neurol 2017;82:259-270.

Topics: Adult; Aged; Aged, 80 and over; Case-Control Studies; Demyelinating Diseases; Female; Fibrin; Fibrinogen; Humans; Inflammation; Male; Middle Aged; Motor Cortex; Multiple Sclerosis, Chronic Progressive; Nerve Degeneration; Plasminogen Activator Inhibitor 1

Alzheimer's disease (AD) is the most common form of dementia and has no effective treatment. Besides the well-known pathologic characteristics, this disease also has a vascular component, and substantial evidence shows increased thrombosis as well as a critical role for fibrin(ogen) in AD. This molecule has been implicated in neuroinflammation, neurovascular damage, blood-brain barrier permeability, vascular amyloid deposition, and memory deficits that are observed in AD. Here, we present evidence demonstrating that fibrin deposition increases in the AD brain and correlates with the degree of pathology. Moreover, we show that fibrin(ogen) is present in areas of dystrophic neurites and that a modest decrease in fibrinogen levels improves neuronal health and ameliorates amyloid pathology in the subiculum of AD mice. Our results further characterize the important role of fibrin(ogen) in this disease and support the design of therapeutic strategies aimed at blocking the interaction between fibrinogen and amyloid-β (Aβ) and/or normalizing the increased thrombosis present in AD.

Topics: Alzheimer Disease; Amyloid beta-Peptides; Animals; Blood-Brain Barrier; Brain; Fibrin; Fibrinogen; Humans; Inflammation; Intracranial Thrombosis; Memory Disorders; Mice, Transgenic; Molecular Targeted Therapy; Nerve Degeneration; Neurites; Neurons

Numerous in-vitro techniques exist for investigating the influence of 3D substrate topography on sensory axon growth. However, simple and cost-effective methods for studying post-natal motor axon interactions with such substrates are lacking. Here, spinal cord organotypic slice cultures (OSC) from post-natal day 7-9 rat pups were presented with spinal nerve roots, or blocks of fibrin hydrogel or 3D microporous collagen scaffolds to investigate motor axon-substrate interactions. By 7-14 days, axons from motor neuronal pools extended into the explanted nerve roots, growing along Schwann cell processes and demonstrating a full range of axon-Schwann cell interactions, from simple ensheathment to concentric wrapping by Schwann cell processes and the formation of compact myelin within a basal lamina sheath. Extensive motor axon regeneration and all stages of axon-Schwann interactions were also supported within the longitudinally orientated microporous framework of the 3D collagen scaffold. In stark contrast, the simple fibrin hydrogel only supported axon growth and cell migration over its surface. The relative ease of demonstrating such motor axon regeneration through the microporous 3D framework by immunofluorescence, two-photon microscopy and transmission electron microscopy strongly supports the adoption of this technique for assaying the influence of substrate topography and functionalization in regenerative bioengineering.

Topics: Animals; Axons; Coculture Techniques; Collagen; Fibrin; Hydrogel, Polyethylene Glycol Dimethacrylate; Image Processing, Computer-Assisted; Immunohistochemistry; Motor Neurons; Nerve Degeneration; Nerve Regeneration; Organ Culture Techniques; Rats; Spinal Cord; Spinal Nerve Roots; Tissue Scaffolds

Early signs of inflammatory demyelination include entry of fibrin(ogen) into the central nervous system (CNS), which is normally excluded by the blood-brain barrier, and up-regulation of components of the plasminogen activator system. Using mice deficient in tissue-type plasminogen activator (tPA-/-) and urokinase plasminogen activator receptor (uPAR-/-), we investigated the involvement of the PA system on the clinical and pathological features of experimental allergic encephalomyelitis, an animal model of multiple sclerosis. tPA-/- mice suffered an early and a more severe acute disease characterized by incomplete recovery when compared to wild-type controls, with significantly higher CNS levels of plasminogen activator inhibitor-1. This correlated with fibrin accumulation, which co-localized with nonphosphorylated neurofilament on thickened axons in experimental allergic encephalomyelitis tissue. In contrast, uPAR-/- mice had a delayed, less acute disease reflected in delayed infiltration of inflammatory cells. These animals developed chronic disease as a result of steadily increased inflammation, increased levels of urokinase-type plasminogen activator (uPA), and greater degree of demyelination. Thus, the plasminogen activator system can modulate both inflammatory and degenerative events in the CNS through the respective effects of tPA and uPAR on fibrinolysis and cell adhesion/migration, manipulation of which may have therapeutic implications for multiple sclerosis.

Topics: Animals; Axons; Central Nervous System; Demyelinating Diseases; Encephalomyelitis, Autoimmune, Experimental; Female; Fibrin; Fibrinolysis; Inflammation; Male; Mice; Mice, Inbred C57BL; Mice, Knockout; Multiple Sclerosis; Nerve Degeneration; Plasminogen Activator Inhibitor 1; Receptors, Cell Surface; Receptors, Urokinase Plasminogen Activator; Tissue Plasminogen Activator; Urokinase-Type Plasminogen Activator

Gap injuries of peripheral nerves, resulting from trauma or neurosurgical procedures, presage badly, for the presence of the distal stump of the nerve seems to be indispensable for regeneration. The standard grafting method requires a lesion of a healthy nerve, and therefore various substitutional materials are under consideration. The aim of the present work was to examine the recovery of rat sciatic nerves after supplying 10-mm-long gaps with an autologous connective-tissue chambers filled with fibrin only or fibrin and various neuroactive substances (brain-derived neurotrophic factor (BDNF), extracts from predegenerated or non-predegenerated nerves). The nerves were allowed to regenerate for 16 weeks. Recovery was measured functionally using the sciatic functional index, and by comparing the weight ratios of calf muscles. The histologic features of regeneration were assessed by counting the number of acetylcholinesterase-positive nerve fibers present inside implanted chambers. We found that chambers filled with fibrin and predegenerated peripheral nerve extracts or BDNF supported functional nerve regeneration much more strongly than chambers filled with fibrin only or fibrin and non-predegenerated peripheral nerve extracts. We conclude that autologous connective-tissue chambers filled with fibrin and predegenerated peripheral nerve extracts or BDNF seem to be a promising tool in peripheral nerve gap injury treatment, with likely clinical implications.

Topics: Animals; Brain-Derived Neurotrophic Factor; Cell Extracts; Fibrin; Male; Microsomes; Nerve Degeneration; Nerve Regeneration; Rats; Rats, Wistar; Recovery of Function; Sciatic Nerve; Sciatic Neuropathy

Despite numerous experimental and clinical attempts to reconstruct injuries of peripheral nerves, the methods developed until now have not been sufficiently effective. We examined the influence of extracts (postmicrosomal fractions) obtained from non-pre-degenerated or 7-day-pre-degenerated distal segments of peripheral nerves on the regeneration of injured sciatic nerves of male adult rats. The extracts were introduced to the site of injury with autologous connective tissue chambers filled with fibrin. Reference groups were treated with brain-derived neurotrophic factor (BDNF) or fibrin only. We examined DiI-labeled motoneurons, toluidine blue-labeled myelinated fibers in the mid-part of the chambers, and AChE-positive nerve endings to assess the regeneration intensity. In addition, the length of fibers regrowing within the chambers was measured. We found that extracts obtained from distal stumps of 7-day-pre-degenerated peripheral nerves enhanced nerve regeneration as strongly as BDNF.

Topics: Acetylcholinesterase; Animals; Brain-Derived Neurotrophic Factor; Fibrin; Male; Microscopy, Electron; Motor Neurons; Nerve Degeneration; Nerve Endings; Nerve Regeneration; Rats; Rats, Wistar; Sciatic Nerve; Silicones; Tissue Extracts

Tissue plasminogen activator (tPA) is a serine protease that converts plasminogen to plasmin and can trigger the degradation of extracellular matrix proteins. In the nervous system, under noninflammatory conditions, tPA contributes to excitotoxic neuronal death, probably through degradation of laminin. To evaluate the contribution of extracellular proteolysis in inflammatory neuronal degeneration, we performed sciatic nerve injury in mice. Proteolytic activity was increased in the nerve after injury, and this activity was primarily because of Schwann cell-produced tPA. To identify whether tPA release after nerve damage played a beneficial or deleterious role, we crushed the sciatic nerve of mice deficient for tPA. Axonal demyelination was exacerbated in the absence of tPA or plasminogen, indicating that tPA has a protective role in nerve injury, and that this protective effect is due to its proteolytic action on plasminogen. Axonal damage was correlated with increased fibrin(ogen) deposition, suggesting that this protein might play a role in neuronal injury. Consistent with this idea, the increased axonal degeneration phenotype in tPA- or plasminogen-deficient mice was ameliorated by genetic or pharmacological depletion of fibrinogen, identifying fibrin as the plasmin substrate in the nervous system under inflammatory axonal damage. This study shows that fibrin deposition exacerbates axonal injury, and that induction of an extracellular proteolytic cascade is a beneficial response of the tissue to remove fibrin. tPA/plasmin-mediated fibrinolysis may be a widespread protective mechanism in neuroinflammatory pathologies.

Topics: Animals; Axons; Blood Coagulation; Demyelinating Diseases; Extracellular Matrix; Fibrin; Fibrinogen; Fibrinolysis; Mice; Mice, Inbred C57BL; Mice, Knockout; Muscle Denervation; Muscle, Skeletal; Nerve Degeneration; Plasminogen; Schwann Cells; Sciatic Nerve; Tissue Plasminogen Activator

Cortical biopsies of eight patients with craniocerebral trauma complicated with subdural or epidural hematoma were examined with the transmission electron microscope. The patients showed post-traumatic neurobehavioural disorders and moderate or severe vasogenic brain edema. The capillary wall displayed increased vacuolar and vesicular endothelial transport, basement membrane thickening and vacuolization and swollen astrocytic end-feet. Pericapillary and parenchymatous hemorrhages were also observed. The extracellular space appeared considerably enlarged with presence of proteinaceous hematogenous edema fluid and fibrinous organization. Pyramidal and non-pyramidal neurons showed intracellular edema featured by irregular enlargement of rough endoplasmic reticulum, nuclear envelope and Golgi apparatus. The myelinated axons exhibited clear or black type axoplasmic degeneration, varicose fiber swelling, myelin sheath distortion, formation of myelin ovoids and increased amount of oligodendroglial ad-axonal layer. The dendrites also showed clear or dark and beaded shape degeneration. Synaptic degeneration was characterized by swollen and shrunken pre- and postsynaptic endings, clumping, enlargement and depletion of synaptic vesicles, synaptic membrane complex disassembly and detachment of glial ensheathment. Perivascular and perineuronal astrocytes appeared remarkably swollen. Phagocytic astrocytes were also found. Oligodendrocytes displayed hydropic and reactive changes. Reactive oligodendrocytes induced myelinolysis. The brain barrier dysfunction, the vasogenic and cytotoxic edema and the subsequent neuronal and neuroglial cell reactive and degeneration processes might represent the morphological substrate responsible for the post-traumatic neurobehavioural disorders.

Topics: Adolescent; Adult; Aged; Aged, 80 and over; Behavioral Symptoms; Blood-Brain Barrier; Brain Edema; Brain Injuries; Capillaries; Cerebral Cortex; Female; Fibrin; Humans; Male; Microscopy, Electron; Middle Aged; Nerve Degeneration; Neurocognitive Disorders

Topics: Alanine; Amino Acids; Animals; Aspartic Acid; Brain Damage, Chronic; Caseins; Fibrin; Glutamates; Humans; Hypothalamus; Injections, Subcutaneous; Mice; Nerve Degeneration; Parenteral Nutrition; Protein Hydrolysates; Sulfonic Acids

Topics: Age Factors; Animals; Brain; Cell Division; Female; Fibrin; Fishes; Male; Meninges; Mesencephalon; Mitosis; Nerve Degeneration; Nerve Regeneration; Sex Factors; Species Specificity; Time Factors