Periwound dopaminergic sprouting is dependent on numbers of wound macrophages

Nerve fiber overgrowth in patients with symptomatic diverticular disease

BACKGROUND

Colonic diverticulosis is a common condition in industrialized countries. Up to 25% of patients with diverticula develop symptoms, a condition termed symptomatic uncomplicated diverticular disease (SUDD). The aim of the present study was to characterize neuroimmune interactions and nerve fiber plasticity in the colonic mucosa of patients with diverticula.

METHODS

Controls, patients with diverticulosis and with SUDD were enrolled in the study. Mucosal biopsies were obtained close to diverticula (diverticular region) and in a normal mucosa (distant site), corresponding to sigmoid and descending colon in the controls. Quantitative immunohistochemistry was used to assess mast cells, T cells, macrophages, nerve fibers, and neuronal outgrowth (growth-associated protein 43, GAP43+fibers).

KEY RESULTS

No difference emerged in mast cells and T cells among the three groups. Macrophages were increased in patients with SUDD and diverticulosis as compared to controls. Nerve fibers were enhanced in patients with SUDD and diverticulosis in comparison with controls in the diverticular region. GAP43+ fibers were increased only in patients with SUDD as compared to controls and to patients with diverticulosis in the diverticular region. In patients with SUDD, GAP43 density was increased in the diverticular region compared to distant site. Macrophages close to GAP43+ fibers were increased in the diverticular region of patients with SUDD. Significant correlations were found between GAP43+ fibers and immune cells.

CONCLUSIONS AND INFERENCES

Patients with diverticula are characterized by increased macrophage counts, while nerve fiber sprouting is increased only in the diverticular region of patients with SUDD suggesting a role in symptom generation.

Molecular and cellular mechanisms underlying the role of blood vessels in spinal cord injury and repair

Spinal cord injury causes immediate damage of nervous tissue accompanied by the loss of motor and sensory function. The limited self-repair ability of damaged nervous tissue underlies the need for reparative interventions to restore function after spinal cord injury. Blood vessels play a crucial role in spinal cord injury and repair. Injury-induced loss of local blood vessels and a compromised blood-brain barrier contribute to inflammation and ischemia and thus to the overall damage to the nervous tissue of the spinal cord. Lack of vasculature and leaking blood vessels impede endogenous tissue repair and limit prospective repair approaches. A reduction of blood vessel loss and the restoration of blood vessels so that they no longer leak might support recovery from spinal cord injury. The promotion of new blood vessel formation (i.e., angio- and vasculogenesis) might aid repair but also incorporates the danger of exacerbating tissue loss and thus functional impairment. The delicate interplay between cells and molecules that govern blood vessel repair and formation determines the extent of damage and the success of reparative interventions. This review deals with the cellular and molecular mechanisms underlying the role of blood vessels in spinal cord injury and repair.

Comparison of inflammation in the brain and spinal cord following mechanical injury

Inflammation in the CNS predominantly involves microglia and macrophages, and is believed to be a significant cause of secondary injury following trauma. This study compares the microglial and macrophage response in the rat brain and spinal cord following discrete mechanical injury to better appreciate the degree to which these cells could contribute to secondary damage in these areas. We find that, 1 week after injury, the microglial and macrophage response is significantly greater in the spinal cord compared to the brain. This is the case for injuries to both gray and white matter. In addition, we observed a greater inflammatory response in white matter compared to gray matter within both the brain and spinal cord. Because activated microglia and macrophages appear to be effectors of secondary damage, a greater degree of inflammation in the spinal cord is likely to result in more extensive secondary damage. Tissue saving strategies utilizing anti-inflammatory treatments may therefore be more useful in traumatic spinal cord than brain injury.

The effect of activated microglia on astrogliosis parameters in astrocyte cultures

In the diseased central nervous system, astrogliosis is accompanied by microglial activation. Depending on the context of their activation, reactive astrocytes are involved in neuronal survival and regeneration in an either protective or impedimental way. Major reactive changes of astrocytes in vivo are the upregulation of the intermediate filaments GFAP (glial fibrillary acidic protein) and vimentin with accompanying cellular hypertrophy and/or hyperplasia. To examine the involvement of activated microglia in the onset and maintenance of astrogliosis, we used an in vitro model of purified cultures of astrocytes and assessed as parameters for astrogliosis GFAP, vimentin, astroglial hypertrophy and cell growth after treatment with medium conditioned by LPS (lipopolysaccarides)-stimulated microglia. Furthermore, IL-6 as a typically upregulated cytokine in proinflammatory processes in the brain was determined in treated astrocytes. GFAP, the classical marker for astrogliosis, was downregulated on its protein and in parallel with vimentin on its mRNA level. The expression of actin, another cytoskeleton protein used as control, remained unchanged. Ultrastructural studies of astroglial intermediate filaments supported these findings. No hypertrophy was found. Nevertheless, LPS-activated microglia stimulated astrocytes as demonstrated by an increased cell number and an enhanced mRNA expression of IL-6. Resting microglia did not change any of the determined parameters. Our results suggest that the role of activated microglia in astrogliotic processes following injury of the brain has to be reevaluated, as microglia in their activated state might support the onset of astrogliosis on the one hand, but might delay or reduce subsequent glial scar formation on the other hand.

Degenerative and spontaneous regenerative processes after spinal cord injury

Spinal cord injury results in acute as well as progressive secondary destruction of local and distant nervous tissue through a number of degenerative mechanisms. Spinal cord injury also initiates a number of endogenous neuroprotective and regenerative responses. Understanding of these mechanisms might identify potential targets for treatments after spinal cord injury in humans. Here, we first discuss recent developments in our understanding of the immediate traumatic and subsequent secondary degeneration of local tissue and long projecting pathways in animal models. These include the inflammatory and vascular responses during the acute phase, as well as cell death, demyelination and scar formation in the subacute and chronic phases. Secondly, we discuss the spontaneous axonal regeneration of injured and plasticity of uninjured systems, and other repair-related responses in animals, including the upregulation of regeneration-associated genes in some neurons, increases in neurotrophic factors in the spinal cord and remyelination by oligodendrocyte precursors and invading Schwann cells. Lastly, we comment on the still limited understanding of the neuropathology in humans, which is largely similar to that in rodents. However, there also are potentially important differences, including the reduced glial scarring, inflammation and demyelination, the increased Schwannosis and the protracted Wallerian degeneration in humans. The validity of current rodent models for human spinal cord injury is also discussed. The emphasis of this review is on the literature from 2002 to early 2005.

Progress in the identification of stroke-related genes: emerging new possibilities to develop concepts in stroke therapy

Stroke is a very complex disease influenced by many risk factors: genetic, environmental and comorbidities, such as hypertension, diabetes mellitus, obesity and having had a previous stroke. Neuroprotective therapies that have been found to be successful in laboratory animals have failed to produce the same benefits in clinical trials. Currently, a re-analysis of the clinical trial failures is underway and new therapeutic approaches using the growing knowledge from neurogenesis and neuroinflammation studies, combined with the information from gene expression studies, are taking place. This review focuses on possible ways to identify therapeutic targets using the new discoveries in neuroinflammation and intrinsic regenerative mechanisms of the brain. Molecular events associated with ischaemia trigger an environment for inflammation. Within the ischaemic region and its penumbra, a battery of chemokines and cytokines are released, which have both detrimental and beneficial effects, depending on the specific timepoint after injury and the current activation status of microglia/macrophages. Preventive therapies and treatments for stroke may be established by identifying the genes that are responsible for the induction of those phenotypic changes of microglia/macrophages that switch them to become players in tissue repair and regeneration processes. To aid in the establishment of new target sources for novel therapeutic agents, animal stroke models should closely mimic stroke in humans. To do so, these models should take into account the various risk factors for stroke. For example, hypertensive animals have a more vulnerable blood-brain barrier that in turn may trigger a greater degree of damage after stroke. Furthermore, in aged animals an accelerated astrocytic and microglial reaction has been observed and the regenerative capacity of aged brains is not as high as young brains. Improvements in animal models may also help to ensure better success rates of potential therapies in clinical studies. Inflammation in the brain is a double-edged sword--characterised by the deleterious effect of nerve cell damage and nerve cell death, as well as the beneficial influence on regeneration. The major challenge to develop successful stroke therapies is to broaden the knowledge regarding the underlying pathologic processes and the intrinsic mechanisms of the brain to drive regenerative and plasticity-related changes. On this basis, new concepts can be created leading to better stroke therapy.

CNS regeneration: clinical possibility or basic science fantasy?

Following injury to the CNS, severed axons undergo a phase of abortive sprouting in the vicinity of the wound, but do not spontaneously re-grow or regenerate. From a long history of attempts to stimulate regeneraion, a major strategy that has been developed clinically is the implantation of tissue into denervated target regions. Unfortunately trials have so far not borne out the promise that this would prove a useful therapy for disorders such as Parkinson's disease. Many strategies have also been developed to stimulate the regeneration of axons across sites of injury, particularly in the spinal cord. Animal data have demonstrated that some of these approaches hold promise and that the spinal cord has a remarkable degree of intrinsic plasticity. Attempts are now being made to utilize experimental techniques in spinal patients.

Peripheral nerve induces macrophage neurotrophic activities: regulation of neuronal process outgrowth, intracellular signaling and synaptic function

Rat cortical neurons cultured in conditioned media from human monocyte-derived macrophages (MDM) show increased neuronal protein synthesis, neurite outgrowth, mitogen-activating protein kinase activity, and synaptic function. Neurotrophic properties of human MDM-conditioned media are significantly enhanced by human peripheral nerve and to a more limited extent by CD40 ligand pre-stimulation. Such positive effects of MDM secretions on neuronal function parallel the secretion of brain-derived neurotrophic factor (BDNF). MDM activation cues may serve to balance toxic activities produced during neurodegenerative diseases and thus, under certain circumstances, mitigate neuronal degeneration.