Transforming growth factor-beta 1 and basic fibroblast growth factor in the injured CNS

Therapeutic Strategies Targeting Respiratory Recovery after Spinal Cord Injury: From Preclinical Development to Clinical Translation

High spinal cord injuries (SCIs) lead to permanent functional deficits, including respiratory dysfunction. Patients living with such conditions often rely on ventilatory assistance to survive, and even those that can be weaned continue to suffer life-threatening impairments. There is currently no treatment for SCI that is capable of providing complete recovery of diaphragm activity and respiratory function. The diaphragm is the main inspiratory muscle, and its activity is controlled by phrenic motoneurons (phMNs) located in the cervical (C3-C5) spinal cord. Preserving and/or restoring phMN activity following a high SCI is essential for achieving voluntary control of breathing. In this review, we will highlight (1) the current knowledge of inflammatory and spontaneous pro-regenerative processes occurring after SCI, (2) key therapeutics developed to date, and (3) how these can be harnessed to drive respiratory recovery following SCIs. These therapeutic approaches are typically first developed and tested in relevant preclinical models, with some of them having been translated into clinical studies. A better understanding of inflammatory and pro-regenerative processes, as well as how they can be therapeutically manipulated, will be the key to achieving optimal functional recovery following SCIs.

The promise of the TGF-β superfamily as a therapeutic target for Parkinson's disease

A large body of evidence underscore the regulatory role of TGF-β superfamily in the central nervous system. Components of the TGF-β superfamily modulate key events during embryonic brain development and adult brain tissue injury repair. With respect to Parkinson's disease (PD), TGF-ß signaling pathways are implicated in the differentiation, maintenance and synaptic function of the dopaminergic neurons, as well as in processes related to the activation state of astrocytes and microglia. In vitro and in vivo studies using toxin models, have interrogated on the dopaminotrophic and protective role of the TGF-β superfamily members. The evolution of genetic and animal models of PD that more closely recapitulate the disease condition has made possible the dissection of intracellular pathways in response to TGF-ß treatment. Although the first clinical trials using GDNF did not meet their primary endpoints, substantial work has been carried out to reappraise the TGF-β superfamily's clinical benefit.

Progression in translational research on spinal cord injury based on microenvironment imbalance

Spinal cord injury (SCI) leads to loss of motor and sensory function below the injury level and imposes a considerable burden on patients, families, and society. Repair of the injured spinal cord has been recognized as a global medical challenge for many years. Significant progress has been made in research on the pathological mechanism of spinal cord injury. In particular, with the development of gene regulation, cell sequencing, and cell tracing technologies, in-depth explorations of the SCI microenvironment have become more feasible. However, translational studies related to repair of the injured spinal cord have not yielded significant results. This review summarizes the latest research progress on two aspects of SCI pathology: intraneuronal microenvironment imbalance and regenerative microenvironment imbalance. We also review repair strategies for the injured spinal cord based on microenvironment imbalance, including medications, cell transplantation, exosomes, tissue engineering, cell reprogramming, and rehabilitation. The current state of translational research on SCI and future directions are also discussed. The development of a combined, precise, and multitemporal strategy for repairing the injured spinal cord is a potential future direction.

Photobiomodulation Promotes Repair Following Spinal Cord Injury by Regulating the Transformation of A1/A2 Reactive Astrocytes

After spinal cord injury (SCI), reactive astrocytes can be classified into two distinctive phenotypes according to their different functions: neurotoxic (A1) astrocytes and neuroprotective (A2) astrocytes. Our previous studies proved that photobiomodulation (PBM) can promote motor function recovery and improve tissue repair after SCI, but little is known about the underlying mechanism. Therefore, we aimed to investigate whether PBM contributes to repair after SCI by regulating the activation of astrocytes. Male rats subjected to clip-compression SCI were treated with PBM for two consecutive weeks, and the results showed that recovery of motor function was improved, the lesion cavity size was reduced, and the number of neurons retained was increased. We determined the time course of A1/A2 astrocyte activation after SCI by RNA sequencing (RNA-Seq) and verified that PBM inhibited A1 astrocyte activation and promoted A2 astrocyte activation at 7 days postinjury (dpi) and 14 dpi. Subsequently, potential signaling pathways related to A1/A2 astrocyte activation were identified by GO function analysis and KEGG pathway analysis and then studied in animal experiments and preliminarily analyzed in cultured astrocytes. Next, we observed that the expression of basic fibroblast growth factor (bFGF) and transforming growth factor-β (TGF-β) was upregulated by PBM and that both factors contributed to the transformation of A1/A2 astrocytes in a dose-dependent manner. Finally, we found that PBM reduced the neurotoxicity of A1 astrocytes to dorsal root ganglion (DRG) neurons. In conclusion, PBM can promote better recovery after SCI, which may be related to the transformation of A1/A2 reactive astrocytes.

[Inhibition of TGF-β promotes functional recovery of spinal cord injury in mice by reducing fibronectin deposition]

OBJECTIVE

To investigate the effect of transforming growth factor (TGF-β) inhibition on functional recovery of spinal cord injury in mice.

METHODS

Twelve mice were divided into treatment group, control group and sham-operated group (n=4). The mice in the treatment group were subjected to hemisection of the spinal cord and received intraperitoneal injection of TGF-β neutralizing antibody (1D11) 3 times a week (25 μL each time), and those in control group were injected with the vehicle antibody (13C4) following spinal cord hemisection. The sham-operated mice underwent sham operation to expose the spinal cord without hemisection. Four weeks later, the heart of the mice was perfused and 1-2 cm of the spinal cord spanning the injury site was harvested. Immunofluorescence staining of FSP1, fibronectin, and PGP9.5 was performed to assess fibroblast recruitment in the injury area, fibronectin deposition, and neurological recovery. For further verification of the results, we used a mouse model of spinal cord clamp injury to observe the survival of axons and distribution of astrocytes by detecting expressions of 5-HT and GFAP with immunofluorescence assay.

RESULTS

In the hemisection injury model, fibroblasts recruitment and fibronectin deposition in the injured area was significantly reduced and the neurological function was improved in 1D11 treatment group as compared with those in 13C4-treated group (P < 0.05). In the spinal cord clamp injury model, treatment with 1D11, as compared with the 13C4, resulted in significantly increased number of 5-HT-positive axons with extended axonal length and obviously increased the number of GFAP-positive astrocytes in the injured area (P < 0.05).

CONCLUSION

Inhibiting TGF-β after spinal cord injury can reduce the recruitment of fibroblasts and fibronectin deposition to promote recovery of neurological function and repair of the injured spinal cord in mice.

Radiotherapy induces an immediate inflammatory reaction in malignant glioma: a clinical microdialysis study

The knowledge of response to radiation in the immuno-microenvironment of high grade gliomas is sparse. In vitro results have indicated an inflammatory response of myeloid cells after irradiation. Therefore, microdialysis was used to verify whether this is operative in tumor tissue and brain adjacent to tumor (BAT) after clinical radiotherapy of patients with high grade glioma. Stereotactic biopsies and implantation of microdialysis catheters in tumor tissue and BAT were performed in eleven patients with high-grade glioma. The patients were given daily radiation fractions of 2–3.4 Gy. Microdialysis samples were collected before radiotherapy and during the first five days of radiation. Cytokines, glucose metabolites, glutamate and glycerol were analyzed. Immunohistochemistry was performed to detect macrophages (CD68) and monocytes (CD163) as well as IL-6, IL-8 and MCP-1. A significant increase of IL-8, MCP-1 and MIP-1a were detected in tumor tissue already after the first dose of radiation and increased further during 5 days of radiation. IL-6 did also increase but after five fractions of radiation. In BAT, the cytokine response was modest with significant increase of IL-8 after third dose of radiation. We found a positive correlation between baseline IL-8 and IL-6 microdialysis levels in tumor tissue and survival. Glucose metabolites or glycerol and glutamate did not change during radiation. In all tumors staining for macrophages was demonstrated. IL-6 was found in viable tumor cells while MCP-1 was demonstrated in macrophages or tumor matrix. Our findings suggest that radiation induces a rapid enhancement of the prevailing inflammation in high-grade glioma tissue. The microdialysis technique is feasible for this type of study and could be used to monitor metabolic changes after different interventions.

Neurocognitive Deficits After Radiation Therapy for Brain Malignancies

Radiotherapy (RT) has proven to be an effective therapeutic tool in treatment of a wide variety of brain tumors; however, it has a negative impact on quality of life and neurocognitive function. Cognitive dysfunction associated with both the disease and adverse effects of RT is one of the most concerning complication among long-term survivors. The effects of RT to brain can be divided into acute, early delayed, and late delayed. It is, however, the late delayed effects of RT that lead to severe neurological consequences such as minor-to-severe cognitive deficits due to irreversible focal or diffuse necrosis of brain parenchyma. In this review, we discuss current and emerging data regarding the relationship between RT and neurocognitive outcomes, and therapeutic strategies to prevent/treat postradiation neurocognitive deficits.

Improved fracture healing in patients with concomitant traumatic brain injury: proven or not?

Over the last 3 decades, scientific evidence advocates an association between traumatic brain injury (TBI) and accelerated fracture healing. Multiple clinical and preclinical studies have shown an enhanced callus formation and an increased callus volume in patients, respectively, rats with concomitant TBI. Over time, different substances (cytokines, hormones, etc.) were in focus to elucidate the relationship between TBI and fracture healing. Until now, the mechanism behind this relationship is not fully clarified and a consensus on which substance plays the key role could not be attained in the literature. In this review, we will give an overview of current concepts and opinions on this topic published in the last decade and both clinical and pathophysiological theories will be discussed.

Intra-articular decorin influences the fibrosis genetic expression profile in a rabbit model of joint contracture

OBJECTIVES

The goal of this study was to determine whether intra-articular administration of the potentially anti-fibrotic agent decorin influences the expression of genes involved in the fibrotic cascade, and ultimately leads to less contracture, in an animal model.

METHODS

A total of 18 rabbits underwent an operation on their right knees to form contractures. Six limbs in group 1 received four intra-articular injections of decorin; six limbs in group 2 received four intra-articular injections of bovine serum albumin (BSA) over eight days; six limbs in group 3 received no injections. The contracted limbs of rabbits in group 1 were biomechanically and genetically compared with the contracted limbs of rabbits in groups 2 and 3, with the use of a calibrated joint measuring device and custom microarray, respectively.

RESULTS

There was no statistical difference in the flexion contracture angles between those limbs that received intra-articular decorin versus those that received intra-articular BSA (66° vs 69°; p = 0.41). Likewise, there was no statistical difference between those limbs that received intra-articular decorin versus those who had no injection (66° vs 72°; p = 0.27). When compared with BSA, decorin led to a statistically significant increase in the mRNA expression of 12 genes (p < 0.01). In addition, there was a statistical change in the mRNA expression of three genes, when compared with those without injection.

CONCLUSIONS

In this model, when administered intra-articularly at eight weeks, 2 mg of decorin had no significant effect on joint contractures. However, our genetic analysis revealed a significant alteration in several fibrotic genes. Cite this article: Bone Joint Res 2014;3:82-8.

Brain tissue interaction with three-dimensional, honeycomb polycaprolactone-based scaffolds designed for cranial reconstruction following traumatic brain injury

Following traumatic brain injury (TBI), resultant voids are unable to support injections of suspension treatments, leading to ineffective healing. Moreover, without a structure to support the large defect, the defect site suffers from mechanical instability, which may impair the healing process. Therefore, having a delivery vehicle that can temporarily fill and provide mechanical support to the defect site may alleviate the healing process. In this work, we reported for the first time, the inflammatory response of brain tissue with polycaprolactone (PCL) and PCL-tricalcium phosphate (TCP) scaffolds designed and fabricated for cranial reconstruction. After cranial defects were created in Sprague-Dawley rats, PCL and PCL-TCP scaffolds were implanted for a period of 1 week and 1 month. Following histology and immunofluorescence staining with the ionized calcium binding adaptor molecule-1 (IBA-1), glial fibrillary acidic protein (GFAP), nestin, and neuronal nuclei (NeuN), results indicated that IBA-1-positive activated microglia were observed across all groups, and declined significantly by 1 month (p<0.05). Interestingly, IBA-1-positive microglia were significantly fewer in the PCL-TCP group (p<0.05), suggesting a relatively milder inflammatory response. A decrease in the number of GFAP-positive cells among all groups over time (>29%) was also observed. Initially, astrocyte hypertrophy was observed proximal to the TBI site (55% in PCL and PCL-TCP groups, 75% in control groups), but it subsided by 1 month. Proximal to the TBI site, nestin immunoreactivity was intense during week 1, and which reduced by 1 month across all groups. NeuN-positive neurons were shrunken proximal to the TBI site (<0.9 mm), 32% smaller in the PCL-TCP group and 27% smaller in the PCL group. Based on above data indicating the comparatively milder, initial inflammatory response of brain tissue to PCL-TCP scaffolds, it is suggested that PCL-TCP scaffolds have notable clinical advantages as compared to PCL scaffolds.

What is the potential of oligodendrocyte progenitor cells to successfully treat human spinal cord injury?

Background

Spinal cord injury is a serious and debilitating condition, affecting millions of people worldwide. Long seen as a permanent injury, recent advances in stem cell research have brought closer the possibility of repairing the spinal cord. One such approach involves injecting oligodendrocyte progenitor cells, derived from human embryonic stem cells, into the injured spinal cord in the hope that they will initiate repair. A phase I clinical trial of this therapy was started in mid 2010 and is currently underway.

Discussion

The theory underlying this approach is that these myelinating progenitors will phenotypically replace myelin lost during injury whilst helping to promote a repair environment in the lesion. However, the importance of demyelination in the pathogenesis of human spinal cord injury is a contentious issue and a body of literature suggests that it is only a minor factor in the overall injury process.

Summary

This review examines the validity of the theory underpinning the on-going clinical trial as well as analysing published data from animal models and finally discussing issues surrounding safety and purity in order to assess the potential of this approach to successfully treat acute human spinal cord injury.

Spinal cord injury induces differential expression of the profibrotic semaphorin 7A in the developing and mature glial scar

Semaphorin 7A (Sema7A) is involved in the formation of the central nervous system during development by operating axon guidance and neuronal migration. We investigated the expression of the TGFβ-inducible Sema7A following spinal cord injury (SCI). After SCI, Sema7A(+) cells accumulated specifically in lesion areas resulting in significantly enhanced Sema7A expression at the injury site (P < 0.0001). During the first days lesional Sema7A expression was confined to neurons, ballooned neurite fibers/retraction bulbs, and endothelial cells. At day 7, we observed Sema7A expression by components of the glial scar, such as reactive astrocytes and pronounced extracellular Sema7A deposition. In the direct perilesional rim, Sema7A(+) astrocytes coexpressed the activation-associated intermediate filament vimentin. In the injured spinal cord, numbers of Sema7A(+) cells reached maximum levels at day 14. The restricted accumulation of Sema7A(+) reactive astrocytes and Sema7A deposition in fibronectin(+) extracellular matrix territories suggests a participation of the fibrostimulatory Sema7A in the developing and maturating scar following SCI. In addition, Sema7A appears to be marker a for astrocyte activation.

Effect of TGF-β1 polymorphism on the susceptibility to schizophrenia and treatment response to atypical antipsychotic agent

Lee H-Y, Kim Y-K. Effect of TGF-β1 polymorphism on the susceptibility to schizophrenia and treatment response to atypical antipsychotic agent.

OBJECTIVE

Several studies have suggested that cytokine alterations could be related to the pathophysiology of schizophrenia. Transforming growth factor-beta1 (TGF-β1) is believed to be an important factor in regulation of inflammatory responses and to have anti-inflammatory effects. TGF-β1 also has trophic effects on dopaminergic neurons. We tested the hypothesis TGF-β1 is associated with the pathophysiology of schizophrenia.

METHODS

The polymorphisms at codon 10 (T869C) and codon 25 (G915C) of TGF-β1 were analysed in 99 schizophrenia patients and 130 normal controls. At baseline and after 8 weeks of treatment, clinical symptoms were evaluated on Positive and Negative Syndrome Scale (PANSS).

RESULTS

None of the subjects were polymorphic at codon 25. However, the C allele at codon 10 was more frequent in schizophrenia (p = 0.05). Although schizophrenia group showed a higher tendency of allele frequency in the subjects with C allele (p = 0.05), the allelic difference did not reach statistical significance after correction for multiple comparisons (p = 0.1). PANSS scores showed no significant correlation with genotypes. The genotype distribution was not significantly different between responders and non-responders. However, the C allele was more frequent among responders (p = 0.03).

CONCLUSION

These results suggest that the TGF-β1 polymorphism is associated with therapeutic response to antipsychotics. However, further studies with larger numbers of subjects are needed to confirm the effect of TGF-β1 in schizophrenia.

Complement C5 regulates the expression of insulin-like growth factor binding proteins in chronic experimental allergic encephalomyelitis

Complement activation plays a central role in autoimmune demyelination. To explore the possible effects of C5 on post-inflammatory tissue repair, we investigated the transcriptional profile induced by C5 in chronic experimental allergic encephalomyelitis (EAE) using oligonucleotide arrays. We used C5-deficient (C5-d) and C5-sufficient (C5-s) mice to compare the gene expression profile and we found that 390 genes were differentially regulated in C5-s mice as compared to C5-d mice during chronic EAE. Among them, a group of genes belonging to the family of insulin-like growth factor binding proteins (IGFBP) and transforming growth factor (TGF)-beta3 were found most significantly differentially regulated by C5. The dysregulation of these genes suggests that these proteins might be responsible for the gliosis and lack of remyelination seen in C5-d mice with chronic EAE.

Mechanisms of radiation-induced brain toxicity and implications for future clinical trials

Radiation therapy is widely used in the treatment of primary malignant brain tumors and metastatic tumors of the brain with either curative or palliative intent. The limitation of cancer radiation therapy does not derive from the inability to ablate tumor, but rather to do so without excessively damaging the patient. Among the varieties of radiation-induced brain toxicities, it is the late delayed effects that lead to severe and irreversible neurological consequences. Following radiation exposure, late delayed effects within the CNS have been attributable to both parenchymal and vascular damage involving oligodendrocytes, neural progenitors, and endothelial cells. These reflect a dynamic process involving radiation-induced death of target cells and subsequent secondary reactive neuroinflammatory processes that are believed to lead to selective cell loss, tissue damage, and functional deficits. The progressive, late delayed damage to the brain after high-dose radiation is thought to be caused by radiation-induced long-lived free radicals, reactive oxygen species, and pro-inflammatory cytokines. Experimental studies suggest that radiation-induced brain injury can be successfully mitigated and treated with several well established drugs in wide clinical use which exert their effects by blocking pro-inflammatory cytokines and reactive oxygen species. This review highlights preclinical and early clinical data that are translatable for future clinical trials.

Mannose-6-phosphate, an inhibitor of transforming growth factor-beta, improves range of motion after flexor tendon repair

BACKGROUND

Adhesion formation between the flexor tendon and its surrounding fibro-osseous sheath results in a decreased postoperative range of motion in the hand. Transforming growth factor-beta (TGF-beta) is a key cytokine in the pathogenesis of tissue fibrosis. In this study, the effects of two natural inhibitors of TGF-beta, decorin and mannose-6-phosphate, were investigated in vitro and in vivo.

METHODS

In the in vitro investigation, primary cell cultures from rabbit flexor tendon sheath, epitenon, and endotenon were established and each was supplemented with TGF-beta along with increasing doses of decorin or mannose-6-phosphate. Collagen-I production was measured with enzyme-linked immunosorbent assay (ELISA). For the in vivo study, rabbit zone-II flexor tendons were transected and then immediately repaired. Single intraoperative graded doses of decorin, mannose-6-phosphate, or phosphate-buffered saline solution (control) were added to the repair sites, and the forepaws were tested for the range of motion and repair strength at eight weeks postoperatively.

RESULTS

Decorin and mannose-6-phosphate both reduced TGF-beta upregulated collagen production. Intraoperative application of low-dose mannose-6-phosphate significantly improved the range of motion of the operatively treated digits. The effect on breaking strength of the tendon repair was inconclusive.

CONCLUSIONS

Mannose-6-phosphate is effective in reducing TGF-beta upregulated collagen production in an in vitro model. This finding correlated with our in vivo finding that a single intraoperative dose of mannose-6-phosphate improved the postoperative range of motion.

Mitigation of radiation-induced optic neuropathy in rats by ACE inhibitor ramipril: importance of ramipril dose and treatment time

PURPOSE

Radiation-induced optic nerve damage was reduced by ramipril, a prodrug angiotensin-converting enzyme inhibitor (ACEI). This study was to determine the optimum dose and administration time of ramipril for mitigating radiation-induced optic neuropathy.

MATERIALS AND METHOD

Adult Fischer 344 male rats were treated with a single dose radiation 30 Gy by using radiosurgical technique. After irradiation, the animals were randomly assigned into groups of different ramipril doses and administration time; control (no treatment), radiation alone, radiation+ramipril in different doses and starting times of drug. Ramipril was given 0.5-1.5 mg/kg/day and AT1R blocker Losartan 20 mg/kg/day in drinking water for 180 days. Functional endpoint with visual evoked potential (VEP) and anatomical endpoint with gross and histological analysis with immunohistochemical (IHC) stain were used.

RESULTS

Normal VEP measurements in un-irradiated rats were 46.2+/-7.9 ms. There was no change of VEP value until 4 months, but was lengthened to 188.1+/-58.7 ms at 6 months after radiation. By ramipril treatment with the dose of 1.5 mg starting at 2 weeks after radiation, VEP was significantly shortened to 105.7+/-88.5 ms at 6 months. Gross and microscopic structure of the irradiated optic nerve was well preserved in the ramipril-treated group.

CONCLUSION

Ramipril can mitigate the radiation-induced optic nerve damage and preserve the functional integrity of the nerve. The results support early treatment with a high dose of ramipril after radiation.

Identification of an Antiangiogenic FGF2-binding Site in the N Terminus of the Soluble Pattern Recognition Receptor PTX3

Long-pentraxin 3 (PTX3) is a soluble pattern recognition receptor with non-redundant functions in inflammation and innate immunity. PTX3 comprises a pentraxin-like C-terminal domain involved in complement activation via C1q interaction and an N-terminal extension with unknown functions. PTX3 binds fibroblast growth factor-2 (FGF2), inhibiting its pro-angiogenic and pro-restenotic activity. Here, retroviral transduced endothelial cells (ECs) overexpressing the N-terminal fragment PTX3-(1-178) showed reduced mitogenic activity in response to FGF2. Accordingly, purified recombinant PTX3-(1-178) binds FGF2, prevents PTX3/FGF2 interaction, and inhibits FGF2 mitogenic activity in ECs. Also, the monoclonal antibody mAb-MNB4, which recognizes the PTX3-(87-99) epitope, prevents FGF2/PTX3 interaction and abolishes the FGF2 antagonist activity of PTX3. Consistently, the synthetic peptides PTX3-(82-110) and PTX3-(97-110) bind FGF2 and inhibit the interaction of FGF2 with PTX3 immobilized to a BIAcore sensor chip, FGF2-dependent EC proliferation, and angiogenesis in vivo. Thus, the data identify a FGF2-binding domain in the N-terminal extension of PTX3 spanning the PTX3-(97-110) region, pointing to a novel function for the N-terminal extension of PTX3 and underlining the complexity of the PTX3 molecule for modular humoral pattern recognition.

Downregulation of glial scarring after brain injury: the effect of purine nucleoside analogue ribavirin

The weak regenerative capacity of self-repair after injury to the adult brain is caused by the formation of glial scar due to reactive astrogliosis. In the present study the beginning of reactive astrogliosis in the adult, as shown immunocytochemically by upregulation of glial fibrillary acidic protein (GFAP) and vimentin, was seen two days after the left sensorimotor cortex lesion, being maximal during the first two weeks and declining by 30 days after the lesion. This was accompanied by intensive glial scarring. Conversely, after the neonatal lesion a lack of gliotic scar was seen until 30 days postsurgery, although the pattern of GFAP and vimentin expression during recovery period was the same. The aim of the study was to define an appropriate therapeutic intervention that could modulate astrocyte proliferation and diminish glial scar formation after adult brain lesion. For this purpose the effects of an antiproliferative agent, the purine nucleoside analogue ribavirin was examined. It was shown that daily injection of ribavirin for 5 and 10 days considerably decreased the number of reactive astrocytes, while slight GFAP labeling was restricted to the lesion site. Obtained results show that ribavirin treatment downregulates the process of reactive astrogliosis after adult brain injury, and thus may be a useful approach for improving neurological recovery from brain damage.

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.

Suitability of allogeneic sertoli cells for ex vivo gene delivery in the injured spinal cord

Cell-based gene delivery for gene therapy offers the advantages of long-term stable expression of proteins without the safety concerns associated with viral vectors. However, issues of immune rejection prevent the widespread use of allogeneic cell implants. In this study, we determine if Sertoli cells, known for their immune privileged status, are suitable vehicles for allogeneic cell-based gene delivery into the injured spinal cord. As proof of concept, Sertoli cells were modified with recombinant adenovirus expressing enhanced green fluorescent protein (eGFP) or a human trophic factor, neurotrophin-3 (hNT-3), and eGFP. Genetically modified Sertoli cells retained their immunosuppressive ability in vitro, based upon lymphocyte proliferation assays, and were capable of generating biologically relevant levels of NT-3. Similarly, modified, allogeneic cells, implanted into the acutely injured spinal cord, reduced the early inflammatory response while producing significant levels of hNT-3 for at least 3 days after grafting. Moreover, these cells survived for at least 42 days after implantation in the injured cord. Together, these results demonstrate that Sertoli cells function in immunomodulation, can be engineered to produce bioactive molecules, and show long-term survival after implantation into the hostile environment of the acutely injured spinal cord. Such long-term survival represents an important first step toward developing an optimal cell-based delivery system that generates sustained expression of a therapeutic molecule.

Matrix metalloproteases: degradation of the inhibitory environment of the transected optic nerve and the scar by regenerating axons

After injury to the central nervous system, a glial/collagen scar forms at the lesion site, which is thought to act as a physicochemical barrier to regenerating axons. We have shown that scar formation in the transected optic nerve (ON) is attenuated when robust growth of axons is stimulated. Matrix metalloproteases (MMP), modulated by tissue inhibitors of MMP (TIMP), degrade a wide variety of extracellular matrix components (ECM) and may be activated by growing axons to remodel the ECM to allow regeneration through the inhibitory environment of the glial or collagen scar. Here, we investigate whether MMP levels are modulated in a nonregenerating (scarring) versus a regenerating (nonscarring) model of ON injury in vivo. Western blotting and immunohistochemistry revealed that MMP-1, -2, and -9 levels were higher and TIMP-1 and TIMP-2 levels were lower in regenerating compared to nonregenerating ON and retinae. In situ zymography demonstrated significantly greater MMP-related gelatinase activity in the regenerating model, mainly colocalized to astrocytes in the proximal ON stump and around the lesion site. These results suggest that activation of MMP and coincident down-regulation of TIMP may act to attenuate the inhibitory scarring in the regenerating ON, thus transforming the ON into a noninhibitory pathway for axon regrowth.

Spinal cord injury induction of lesional expression of profibrotic and angiogenic connective tissue growth factor confined to reactive astrocytes, invading fibroblasts and endothelial cells

OBJECT

The glial scar composed of astrogliosis and extracellular matrix deposition represents a major impediment to axonal regeneration. The authors investigated the role of a novel profibrotic and angiogenic peptide connective tissue growth factor (CTGF [Hcs24/IGFBP-r2P]) in glial scar formation following spinal cord injury (SCI) in rats.

METHODS

The effects of SCI on CTGF expression during glial scar maturation 1 day to 1 month post-SCI were investigated using fluorescein-activated cell sorter (FACS) immunohistochemical analysis; these findings were compared with those obtained in sham-operated (control) spinal cords. The CTGF-positive cells accumulated at the spinal cord lesion site (p < 0.0001) corresponding to areas of glial scar formation. In the perilesional rim, CTGF expression was confined to invading vimentin-positive, glial fibrillary acidic protein (GFAP)-negative fibroblastoid cells, endothelial and smooth-muscle cells of laminin-positive vessels, and GFAP-positive reactive astrocytes. The CTGF-positive astrocytes coexpressed the activation-associated intermediate filaments nestin, vimentin (> 80%), and mesenchymal scar component fibronectin (50%).

CONCLUSIONS

The restricted accumulation of CTGF-reactive astrocytes and CTGF-positive fibroblastoid cells lining the laminin-positive basal neolamina suggests participation of these cells in scar formation. In addition, perilesional upregulation of endothelial and smooth-muscle CTGF expression points to a role in blood-brain barrier function modulating edema-induced secondary damage.

Therapeutic effects of rectal administration of basic fibroblast growth factor on experimental murine colitis

BACKGROUND & AIMS

Basic fibroblast growth factor (bFGF) is a promising therapeutic agent for various diseases. It remains unclear, however, whether bFGF is effective for the treatment of inflammatory bowel disease. The aim of this study was to examine the efficacy of bFGF on 2 experimental murine colitis models and to investigate its molecular mechanisms.

METHODS

We evaluated the effects of human recombinant bFGF (hrbFGF) on mice with dextran sulfate sodium (DSS)-induced colitis and mice with trinitrobenzene sulfonic acid (TNBS)-induced colitis as well as normal mice. Body weight, survival rate, and histologic findings of the colonic tissues were examined. Gene expression of tumor necrosis factor (TNF)-alpha, cyclooxygenase (COX)-2, transforming growth factor (TGF)-beta, mucin 2 (MUC2), intestinal trefoil factor (ITF), and vascular endothelial growth factor (VEGF) in the colonic tissues was determined. The proliferation activity of hrbFGF on the colonic epithelium was evaluated by immunohistochemistry.

RESULTS

Rectal administration of hrbFGF ameliorated DSS-induced colitis in a dose-dependent manner. Gene expression of TNF-alpha was significantly reduced in the colonic tissues of mice with DSS-induced colitis treated with hrbFGF, whereas MUC2 and ITF messenger RNA expression was up-regulated. Rectal administration of hrbFGF significantly improved the survival rate of mice with TNBS-induced colitis and partially ameliorated colitis. hrbFGF significantly increased the number of Ki-67-positive cells in the colonic epithelium of normal mice, and up-regulated the gene expression of COX-2, TGF-beta, MUC2, ITF, and VEGF in the colonic tissues.

CONCLUSIONS

Rectal administration of bFGF might be a promising option for the treatment of inflammatory bowel disease.

Patterns of gene expression reveal a temporally orchestrated wound healing response in the injured spinal cord

Spinal cord injury (SCI) induces a progressive pathophysiology affecting cell survival and neurological integrity via complex and evolving molecular cascades whose interrelationships are not fully understood. The present experiments were designed to: (1) determine potential functional interactions within transcriptional expression profiles obtained after a clinically relevant SCI and (2) test the consistency of transcript expression after SCI in two genetically and immunologically diverse rat strains characterized by differences in T cell competence and associated inflammatory responses. By interrogating Affymetrix U34A rat genome GeneChip microarrays, we defined the transcriptional expression patterns in midcervical contusion lesion sites between 1 and 90 d postinjury of athymic nude (AN) and Sprague Dawley (SD) strains. Stringent statistical analyses detected significant changes in 3638 probe sets, with 80 genes differing between the AN and SD groups. Subsequent detailed functional categorization of these transcripts unveiled an overall tissue remodeling response that was common to both strains. The functionally organized gene profiles were temporally distinct and correlated with repair indices observed microscopically and by magnetic resonance microimaging. Our molecular and anatomical observations have identified a novel, longitudinal perspective of the post-SCI response, namely, that of a highly orchestrated tissue repair and remodeling repertoire with a prominent cutaneous wound healing signature that is conserved between two widely differing rat strains. These results have significant bearing on the continuing development of cellular and pharmacological therapeutics directed at tissue rescue and neuronal regeneration in the injured spinal cord.

Prevention of fibrosis in experimental colitis by captopril: the role of tgf-beta1

BACKGROUND & AIMS

There is a body of evidence to suggest that the local activation of angiotensin II (ANG II) plays a pivotal role in fibrogenic response involving the kidney, heart, lung, pancreas and liver. In such conditions, fibrosis is mediated, at least partially, through ANG II induction of the cytokine transforming growth factor-beta1 (TGF-beta1). Both ANG II and TGF-beta1 also seem to be involved in intestinal fibrosis and stenosis, particularly in Crohn's disease. The aim of the present study was, firstly, to determine the effects of the angiotensin-converting enzyme inhibitor, captopril, on colonic fibrosis in experimental colitis in rats and, secondly, to check the role of TGF-beta1 on these effects.

METHODS

Colitis was induced in rats by intracolonic administration of TNBS. Colonic fibrosis was assessed 21 days later by macroscopic and microscopic evaluation. Levels of collagen alpha1 gene expression, hydroxyproline, angiotensin II and TGF-beta1 proteins, and TGF-beta1 mRNA were measured on the colonic tissue.

RESULTS

In chronic colitis, captopril significantly reduced the score of macroscopic and histologic lesions, as well as the colonic tissue levels of collagen alpha1, hydroxyproline, ANG II and TGF-beta1 proteins, and TGF-beta1 mRNA.

CONCLUSIONS

These data demonstrate for the first time that the prophylactic administration of captopril is effective in preventing colonic fibrosis in TNBS-induced colitis. The antifibrotic action of captopril could be due to the blockade of TGFbeta-1 overexpression, and/or to a direct down-regulation of TGFbeta-1 transcript.

Chronic response of adult rat brain tissue to implants anchored to the skull

Using quantitative immunohistological methods, we examined the brain tissue response to hollow fiber membranes (HFMs) that were either implanted intraparenchymally, as in a cell encapsulation application, or were attached to the skull as in a biosensor application (transcranially). We found that the reaction surrounding transcranially implanted HFMs was significantly greater than that observed with intraparenchymally implanted materials including increases in immunoreactivity against GFAP, vimentin, ED-1 labeled macrophages and microglia, and several extracellular matrix proteins including collagen, fibronectin, and laminin. In general, these markers were elevated along the entire length of transcranially implanted HFMs extending into the adjacent parenchyma up to 0.5 mm from the implant interface. Intraparenchymal implants did not appear to have significant involvement of a fibroblastic component as suggested by a decreased expression of vimentin, fibronectin and collagen-type I at the implant tissue interface. The increase in tissue reactivity observed with transcranially implanted HFMs may be influenced by several mechanisms including chronic contact with the meninges and possibly motion of the device within brain tissue. Broadly speaking, our results suggest that any biomaterial, biosensor or device that is anchored to the skull and in chronic contact with meningeal tissue will have a higher level of tissue reactivity than the same material completely implanted within brain tissue.

Selective recognition of fibroblast growth factor-2 by the long pentraxin PTX3 inhibits angiogenesis

The long pentraxin PTX3 is a soluble pattern recognition receptor produced by monocytes and endothelial cells that plays a nonredundant role in inflammation. Several pathologic conditions are characterized by local production of both PTX3 and the angiogenic fibroblast growth factor-2 (FGF2). Here, solid-phase binding assays demonstrated that PTX3 binds with high affinity to FGF2 but not to a panel of cytokines and growth factors, including FGF1, FGF4, and FGF8. Accordingly, PTX3 prevented (125)I-FGF2 binding to endothelial cell receptors, leading to specific inhibition of FGF2-induced proliferation. PTX3 hampered also the motogenic activity exerted by endogenous FGF2 on a wounded endothelial cell monolayer. Moreover, PTX3 cDNA transduction in FGF2-transformed endothelial cells inhibited their autocrine FGF2-dependent proliferation and morphogenesis in vitro and their capacity to generate vascular lesions when injected in nude mice. Finally, PTX3 suppressed neovascularization triggered by FGF2 in the chick embryo chorioallantoic membrane with no effect on physiologic angiogenesis. In contrast, the short pentraxin C-reactive protein was a poor FGF2 ligand/antagonist. These results establish the selective binding of a member of the pentraxin superfamily to a growth factor. PTX3/FGF2 interaction may modulate angiogenesis in various physiopathologic conditions driven by inflammation, innate immunity, and/or neoplastic transformation.

Differences in cytokine gene expression profile between acute and secondary injury in adult rat spinal cord

It is likely that the environment within the injured spinal cord influences the capacity of fetal spinal cord transplants to support axonal growth. We have recently demonstrated that fetal spinal cord transplants and neurotrophin administration support axonal regeneration after spinal cord transection, and that the distance and amount of axonal growth is greater when these treatments are delayed by several weeks after injury. In this study, we sought to determine whether differences in inflammatory mediators exist between the acutely injured spinal cord and the spinal cord after a second injury and re-section, which could provide a more favorable environment for the axonal re-growth. The results of this study show a more rapid induction of transforming growth factor (TGF) beta1 mRNA expression in the re-injured spinal cord than the acutely injured spinal cord and an attenuation of proinflammatory cytokine mRNA expression. Furthermore, there was a rapid recruitment of activated microglia/macrophages in the degenerating white matter rostral and caudal to the injury but fewer within the lesion site itself. These findings suggest that the augmentation of TGFbeta-1 gene expression and the attenuation of pro-inflammatory cytokine gene expression combined with an altered distribution of activated microglia/macrophages in the re-injured spinal cord might create a more favorable milieu for transplants and axonal regrowth as compared to the acutely injured spinal cord.

Fibroblast growth factors and neuroprotection

Several members of the FGF family, in particular FGF2, are intimately involved in neuronal protection and repair after ischemic, metabolic or traumatic brain injury. Expression of Fgf2 mRNA and protein is strongly upregulated after neuronal damage, with glial cells as the predominant source. Given its survival-promoting effects on cultured neurons, exogenous FGF2 was tested in several animal models of stroke and excitotoxic damage, in which it consistently proved protective against neuronal loss. FGF2 affords neuroprotection by interfering with a number of signaling pathways, including expression and gating of NMDA receptors, maintenance of Ca2+ homeostasis and regulation of ROS detoxifying enzymes. FGF2 prevents apoptosis by strengthening anti-apoptotic pathways and promotes neurogenesis in adult hippocampus after injury. The protective action of FGF2 has been linked to its augmenting effect on the lesion-induced upregulation of activin A, a member of the TGF-beta superfamily. Despite the well-documented benefits of FGF2 in animal models of stroke, there is currently no clinical development in stroke, after a phase II/III trial with FGF2 in acute stroke patients was discontinued because of an unfavorable risk-to-benefit ratio. As the molecular targets of FGF2 are going to be unraveled over the next years, new therapeutic strategies will hopefully emerge that enable us to influence the various protective mechanisms of FGF2 in a more specific fashion.

Biologic Transplantation and Neurotrophin-Induced Neuroplasticity After Traumatic Brain Injury

OBJECTIVE

In this review, we analyze progress in the treatment of traumatic brain injury with neurotrophins, growth factors and cell and tissue neurotransplantation. The primary objective of these therapies is to reduce neurologic deficits associated with the trauma by inducing neuroplasticity. These therapies are restorative and not necessarily neuroprotective.

MAIN OUTCOME MEASURES

An extensive literature on administration of neurotrophics factors and cell and tissue cerebral transplantation is reviewed. The effects of these therapeutic approaches on brain biochemical, molecular, cellular, and tissue responses are summarized.

CONCLUSION

The cumulative data indicate that cell therapy shows substantial promise in the treatment of neural injury.

Changes in neurocan expression in the distal spinal cord stump following complete cord transection: a comparison between infant and adult rats

The distal transected cords of infant rats are more permissive for axon extension than those of adults. To elucidate the biomolecular basis for this phenomenon, we examined the expression pattern of neurocan using semi-quantitative reverse transcription polymerase chain reaction and immunostaining in the distal cord of both adult and infant rats after transection. Neurocan is a chondroitin sulfate proteoglycan with well-documented axon growth-inhibitory properties in the central nervous system. Neurocan mRNA was up-regulated in the distal cord of adult rats shortly after transection, followed by a longer wide distribution of neurocan immunoreactivity (IR) in both neurons and astrocytes; by contrast, upregulation of neurocan mRNA was not seen in infant rats, although transient expression of neurocan IR was seen in neurons. Combined with the different regenerative capacity of infant and adult rats, the present results suggest that neurocan inhibits spinal cord regeneration.

Transforming growth factor beta2 is released from PC12 cells via the regulated pathway of secretion

Transforming growth factor beta2 (TGF-beta2), a prototypic member of a large superfamily of multifunctional cytokines, is expressed by neurons and glial cells. Its subcellular compartmentalization and release from neurons, however, are largely unknown. Here we show that TGF-beta2 colocalizes with the trans-Golgi network marker TGN38 and a marker molecule for secretory granules, chromogranin B (CgB), in PC12 cells. Similarly, primary hippocampal neurons show colocalization of TGN38 and TGF-beta2. A substantial amount of endogenous as well as transfected TGF-beta2 in PC12 cells comigrates with CgB on an equilibrium gradient, suggesting costorage in secretory granules. TGF-beta biological activity peaks in identical fractions. Depolarization of PC12 cells with high potassium triggers colocalization of CgB and TGF-beta2 at the cell surface, suggesting their regulated corelease from secretory granules. High potassium also liberates biologically active TGF-beta from PC12 cells and primary neurons. Our results indicate that a substantial portion of TGF-beta2 is secreted by the regulated secretory pathway in PC12 cells and hippocampal neurons.

Chondroitin sulphate proteoglycans in the CNS injury response

As the preceding discussion has demonstrated, experimental data now indicate that the expression of a number of different CSPGs is increased following CNS injury. The hyalectans neurocan, versican and [figure: see text] brevican, plus NG2 and phosphacan are upregulated following injury and all have been shown to exhibit inhibitory effects on neurite outgrowth in vitro. It is likely therefore that the increased expression of these molecules contributes to the non-permissive nature of the glial scar. The relative contributions of individual molecules remain, however, to be determined. It is important to remember also that not only does the glial scar contain many different inhibitory molecules, but that these are the products of a number of different cells, including not just astrocytes, but also oligodendrocyte progenitor and meningeal cells. It is arguable that the latter two cell types make a greater contribution than astrocytes to the inhibitory environment of the injured CNS. Recently, attempts have been made to alter the CSPG component of the glial scar in the hope that this will facilitate improved axonal regeneration. Three studies (Bradbury et al., 2002; Yick et al., 2000; Moon et al., 2001) have reported an improved regenerative response following treatment of the injured CNS with chondroitinase ABC. CSPGs represent a significant source of inhibition within the injured CNS; these studies indicate that successful CNS regeneration may be brought about by interventions which target these molecules and/or the cells which produce them.

Matrix metalloproteases and their inhibitors are produced by overlapping populations of activated astrocytes

Matrix metalloproteases (MMPs) and tissue inhibitors of metalloproteases (TIMPs) are involved in many cell migration phenomena and produced by many cell types, including neurons and glia. To assess their possible roles in brain injury and regeneration, we investigate their production by glial cells, after brain injury and in tissue culture, and we investigate whether they are capable of digesting known axon-inhibitory proteoglycans. To determine the action of MMPs, we incubated astrocyte conditioned medium with activated MMPs, then did western blots for several chondroitin sulphate proteoglycans. MMP-3 digested all five proteoglycans tested, whereas MMP-2 digested only two and MMP-9 none. To determine whether MMPs or TIMPs are produced by astrocytes in vitro, we tested both primary cultures and astrocyte cell lines by western blotting, and compared them with Schwann cells. All cultures produced at least some MMPs and TIMPs, with no obvious correlation with the ability of axons to grow on those cells. Both MMP-9 and TIMP-3 were regulated by various cytokines. To determine which cells produce MMPs and TIMPs after brain injury, we made lesions of adult rat cortex, and did immunohistochemistry. MMP-2 was seen to be induced in activated astrocytes through the whole thickness of the cortex but not deeper, but MMP-3 was not seen in the injured brain. TIMP-2 and TIMP-3 immunoreactivities were induced in activated astrocytes in deep cortex and the underlying white matter. In situ hybridisation confirmed induction of TIMP-2 in glia as well as neurons, but showed no expression of TIMP-4. These results show that both MMPs and TIMPs are produced by some astrocytes, but TIMP production is particularly strong, especially in deep cortex and white matter which is more inhibitory for axon regeneration. Conversely the MMPs produced may not be adequate to promote migration of cells and axons within the glial scar.

Induction of type IV collagen and other basement-membrane-associated proteins after spinal cord injury of the adult rat may participate in formation of the glial scar

We investigated the spatial and temporal expression of basement-membrane-forming and neurite-outgrowth-supporting matrix proteins after a unilateral dorsal root injury combined with a collagen I/laminin-1 graft and a stab wound lesion to the dorsal horn of the adult rat spinal cord. Ten days after injury, the gamma1 laminin was induced in the reactive glia. At this early stage, the glial cells failed to express type IV collagen and the alpha1 laminin. One month after injury, reactive astrocytes in the dorsal horn of the lesioned side expressed gamma1 laminin, type IV collagen, and the alpha1 laminin whereas astrocytes of the normal spinal cord or the uninjured contralateral dorsal horn were negative. Both astrocytes and neurons of the ipsilateral ventral horn were induced to express laminin-1 and gamma1 laminin. Astrocytes of the ipsilateral ventral horn also expressed type IV collagen. Simultaneously with the changes in expression of the extracellular matrix proteins, the expression pattern of basic fibroblast growth factor (FGF-2) was markedly altered after spinal cord injury. In normal and contralateral spinal cord, FGF-2 was expressed in nerve fibers, but its expression changed from neuronal into glial in the ipsilateral spinal cord within 1 month after injury. Four months after injury, expression of both type IV collagen and the alpha1 laminin had declined, but the astrocytes at the injury site continued expressing the gamma1 laminin. Cultured astrocytes were negative for type IV collagen, but several cytokines, including IL-1beta and TGFbeta1, induced expression of type IV collagen in the astrocytes. These factors also increased deposition of type IV collagen matrix in the glial cultures. These results indicate that type IV collagen and the alpha1 laminin are induced in reactive astrocytes after spinal cord injury in vivo. Induction of type IV collagen in astrocytes in vitro by cytokines indicates that blood-borne or local factors at the injury site may induce the spinal cord glial expression of type IV collagen in vivo. Simultaneous expression of laminin-1 and alpha1 laminin with type IV collagen is known to lead to production of basement membranes. This may hamper the neurite-outgrowth-promoting potential of the gamma1 laminin by initiating formation of the glial scar.

Gene expression differences in bipolar disorder revealed by cDNA array analysis of post-mortem frontal cortex

Previous studies have implicated a number of biochemical pathways in the etiology of bipolar disorder (BD). However, the precise abnormalities underlying this disorder remain to be established. To investigate novel factors that may be important in the pathophysiology of BD, we utilized cDNA expression arrays to examine differences in expression of up to 1200 genes known to be involved in potentially relevant biochemical processes. This investigation was undertaken in post-mortem samples of frontal cortex tissue from patients with BD and matched controls, obtained (n = 10/group) from the Stanley Foundation Neuropathology Consortium. Results include significant (greater than 35% change in signal intensity) differences between BD and controls in a number of genes (n = 24). Selected targets were analyzed by RT-PCR, which confirmed a decrease in transforming growth factor-beta1 (TGF-beta 1), and an increase in both caspase-8 precursor (casp-8) and transducer of erbB2 (Tob) expression in BD. We further observed a significant decrease of TGF-beta 1 mRNA levels in BD by RT-PCR in individual post-mortem samples. Given the neuroprotective role attributed to this inhibitory cytokine, our results suggest that the down-regulation of TGF-beta 1 may lead to various neurotoxic insults potentially involved in the etiology of certain mood disorders.

Reduction in CNS scar formation without concomitant increase in axon regeneration following treatment of adult rat brain with a combination of antibodies to TGFbeta1 and beta2

In this study we investigated whether CNS axons regenerate following attenuation of scar formation using a combination of antibodies against two isoforms of transforming growth factor beta (TGFbeta). Anaesthetized adult rats were given unilateral mechanical lesions of the nigrostriatal tract. Implantation of transcranial cannulae allowed wounds to be treated with a combination of antibodies against TGFbeta1 and TGFbeta2 once daily for 10 days postaxotomy. Eleven days post-transection brains from animals under terminal anaesthesia were recovered for histological evaluation. Gliosis, inflammation and the response of dopaminergic nigral axons were assessed by immunolabelling. Treatment with antibodies against TGFbeta1 and TGFbeta2 attenuated (but did not abolish) the response of glial fibrillary acidic protein (GFAP)-immunoreactive astrocytes and of NG2-immunoreactive glia but did not attenuate the response of CR3-immunoreactive microglia and macrophages. However, this reduction in scar formation was not accompanied by growth of cut dopaminergic nigral axons. We conclude that treatment of injured adult rat brain with a combination of antibodies against TGFbeta1 and TGFbeta2 results in a reduction of scar formation but that this is not sufficient to enhance spontaneous long distance CNS axon regeneration.

The duality of the inflammatory response to traumatic brain injury

One and a half to two million people sustain a traumatic brain injury (TBI) in the US each year, of which approx 70,000-90,000 will suffer from long-term disability with dramatic impacts on their own and their families' lives and enormous socio-economic costs. Brain damage following traumatic injury is a result of direct (immediate mechanical disruption of brain tissue, or primary injury) and indirect (secondary or delayed) mechanisms. These secondary mechanisms involve the initiation of an acute inflammatory response, including breakdown of the blood-brain barrier (BBB), edema formation and swelling, infiltration of peripheral blood cells and activation of resident immunocompetent cells, as well as the intrathecal release of numerous immune mediators such as interleukins and chemotactic factors. An overview over the inflammatory response to trauma as observed in clinical and in experimental TBI is presented in this review. The possibly harmful/beneficial sequelae of post-traumatic inflammation in the central nervous system (CNS) are discussed using three model mediators of inflammation in the brain, tumor necrosis factor-alpha (TNF-alpha), interleukin-6 (IL-6), and transforming growth factor-beta (TGF-beta). While the former two may act as important mediators for the initiation and the support of post-traumatic inflammation, thus causing additional cell death and neurologic dysfunction, they may also pave the way for reparative processes. TGF-beta, on the other hand, is a potent anti-inflammatory agent, which may also have some deleterious long-term effects in the injured brain. The implications of this duality of the post-traumatic inflammatory response for the treatment of brain-injured patients using anti-inflammatory strategies are discussed.

Differential cellular accumulation of connective tissue growth factor defines a subset of reactive astrocytes, invading fibroblasts, and endothelial cells following central nervous system injury in rats and humans

In brain injury, the primary trauma is followed by a cascade of cellular and molecular mechanisms resulting in secondary injury and scar formation. Astrogliosis and expression of transforming growth factor beta (TGF-beta) are key components of scar formation. A cytokine mediating the effects of TGF-beta is connective tissue growth factor (CTGF), a fibrogenic peptide encoded by an immediate early gene with suggested roles in tissue regeneration and aberrant deposition of extracellular matrix. In order to investigate CTGF in traumatic lesions, we evaluated 20 human brains with traumatic brain injury (TBI) and 18 rat brains with stab wound injury. Compared to remote areas and unaltered control brains, CTGF+ cells accumulated in border zones of the traumatic lesion site (p < 0.0001). In the direct peri-lesional rim, CTGF expression was confined to invading vimentin+, GFAP- fibroblastoid cells, endothelial and smooth muscle cells of laminin+ vessels, and GFAP+ reactive astrocytes. In the direct peri-lesional rim, CTGF+ astrocytes (>80%) co-expressed the activation associated intermediate filaments nestin and vimentin. In injured rat brains, numbers of CTGF+ cells peaked at day 3 and 7 and decreased to almost base level 3 weeks postinjury, whereas in humans, CTGF+ cells remained persistently elevated up to 6 months (p < 0.0001). The restricted accumulation of CTGF+-reactive astrocytes and CTGF+ fibroblastoid cells lining the adjacent laminin+ basal lamina suggests participation of these cells in scar formation. Furthermore, peri-lesional upregulation of endothelial CTGF expression points to a role in blood-brain barrier function and angiogenesis. In addition, CTGF appears to be a sensitive marker of early astrocyte activation.

Delayed changes in growth factor gene expression during slow remyelination in the CNS of aged rats

In this study we have examined whether the slower rate of CNS remyelination that occurs with age is associated with a change in growth factor expression patterns, an association that would provide further support for a causal relationship between growth factors and remyelination. Using quantitative in situ hybridization we have shown that there are differences in IGF-I, TGF-beta 1, and PDGF-A mRNA expression during remyelination of lysolecithin-induced demyelination in the spinal cord of young adult and old adult rats. IGF-I and TGF-beta1 mRNA expression in old rats had a delayed and lower peak expression compared to young rats. The initial increase in PDGF-A mRNA expression was delayed in old rats compared to young rats, but after 5 days both age groups had similar patterns of expression, as was the expression pattern of FGF-2 mRNA at all survival times. In neither age group were increases in CNTF, NT-3, or GGF-2 mRNA expression detected. An analysis of the macrophage response using oligonucleotide probes for scavenger receptor-B mRNA indicated that differences in the macrophage response in young and old animals was the likely cause of the age related change in IGF-I and TGF-beta 1 mRNA expression patterns. On the basis of these data we suggest a model of remyelination in which PDGF is involved in the initial phase of oligodendrocyte progenitor recruitment, while IGF-I and TGF-beta 1 trigger the differentiation of the recruited cells into myelinating oligodendrocytes.

Connective tissue growth factor: what's in a name?

Connective tissue growth factor (CTGF) is a member of the recently described CCN gene family which contains CTGF itself, cyr61, nov, elm1, Cop1, and WISP-3. CTGF is transcriptionally activated by several factors although its stimulation by transforming growth factor beta (TGF-beta) has attracted considerable attention. CTGF acts to promote fibroblast proliferation, migration, adhesion, and extracellular matrix formation, and its overproduction is proposed to play a major role in pathways that lead to fibrosis, especially those that are TGF-beta-dependent. This includes fibrosis of major organs, fibroproliferative diseases, and scarring. CTGF also appears to play a role in the extracellular matrix remodeling that occurs in normal physiological processes such as embryogenesis, implantation, and wound healing. However, recent advances have shown that CTGF is involved in diverse autocrine or paracrine actions in several other cell types such as vascular endothelial cells, epithelial cells, neuronal cells, vascular smooth muscle cells, and cells of supportive skeletal tissues. Moreover, in some circumstances CTGF has negative effects on cell growth in that it can be antimitotic and apoptotic. In light of these discoveries, CTGF has been implicated in a diverse variety of processes that include neovascularization, transdifferentiation, neuronal scarring, atherosclerosis, cartilage differentiation, and endochondral ossification. CTGF has thus emerged as a potential important effector molecule in both physiological and pathological processes and has provided a new target for therapeutic intervention in fibrotic diseases.

Induction of reactive astrocytosis and prevention of motoneuron cell death by the I(2)-imidazoline receptor ligand LSL 60101

I(2)-imidazoline receptors are mainly expressed on glial cells in the rat brain. This study was designed to test the effect of treatment with the I(2)-imidazoline selective receptor ligand LSL 60101 [2-(2-benzofuranyl)imidazole] on the morphology of astrocytes in the neonate and adult rat brain, and to explore the putative neuroprotective effects of this glial response. Short-term (3 days) or chronic (7-10 days) treatment with LSL 60101 (1 mg kg(-1), i.p. every 12 h) enhanced the area covered by astroglial cells in sections of facial motor nucleus from neonate rats processed for glial fibrillary acidic protein (GFAP) immunostaining. Facial motoneurons surrounded by positive glial cell processes were frequently observed in sections of LSL 60101-treated rats. A similar glial response was observed in the parietal cortex of adult rats after chronic (10 days) treatment with LSL 60101 (10 mg kg(-1), i.p. every 12 h). Western-blot detection of the specific astroglial glutamate transporter GLT-1, indicated increased immunoreactivity after LSL 60101 treatment in the pons of neonate and in the parietoccipital cortex of adult rats. In the facial motor nucleus of neonate rats, the glial response after LSL 60101 treatment was associated to a redistribution of the immunofluorescence of the basic fibroblast growth factor (FGF-2) from the perinuclear area of motoneurons to cover most of their cytoplasm, suggesting a translocation of this mitogenic and neurotrophic factor towards secretion pathways. The neuroprotective potential of the above effects of LSL 60101 treatment was tested after neonatal axotomy of facial motor nucleus. Treatment with LSL 60101 (1 mg kg(-1), i.p. every 12 h from day 0 to day 10 after birth) significantly reduced (38%) motoneuron death rate 7 days after facial nerve axotomy performed on day 3 after birth. It is concluded that treatment with the I(2)-imidazoline selective receptor ligand LSL 60101 provokes morphological/biochemical changes in astroglia that are neuroprotective after neonatal axotomy.

Basic fibroblast growth factor (bFGF) enhances functional recovery following severe spinal cord injury to the rat

We have recently demonstrated that following a moderate contusion spinal cord injury (SCI) to rats, subsequent administration of basic fibroblast growth factor (bFGF) significantly enhances functional recovery and tissue sparing. To further characterize the effects of bFGF, we evaluated its efficacy after a more severe contusion injury at T(10) using the NYU impactor. Immediately after SCI, osmotic minipumps were implanted into the lateral ventricle and lumbar thecal sac to deliver bFGF at 3 or 6 microg per day versus control vehicle for 1 week. Animals were behaviorally tested for 6 weeks before histological assessment of tissue sparing through the injured segment and glial reactivity distal to the lesion. Compared to moderate SCI, all rats had more prolonged and sustained functional deficits 6 weeks after severe contusion. Subjects treated with bFGF had pronounced recovery of hindlimb movements from 2 to 6 weeks compared to controls, manifested in significantly higher behavioral scores. Only marginal tissue sparing was seen rostral to the injury in bFGF-treated spinal cords versus controls. Optical density measurements of astrocyte and microglial cell immunoreactivity in bFGF-treated spinal cords showed that after 6 weeks they approximated controls, although astrocyte immunoreactivity remained higher in controls rostrally. In summary, intrathecal infusion of bFGF following severe SCI significantly restores gross hindlimb motor function that is not correlated with significant tissue sparing. In light of previous evidence that pharmacological intervention with bFGF after moderate SCI enhances tissue preservation, the current findings indicate that yet undefined mechanisms contribute to the enhanced functional recovery following bFGF treatment.

Comparative evaluation of cytokine profiles and reactive gliosis supports a critical role for interleukin-6 in neuron-glia signaling during regeneration

Using reverse transcription polymerase chain reaction (RT-PCR), we have studied the temporal expression of interleukin-1beta (IL-1beta), interleukin-6 (IL-6), transforming growth factor-beta 1 (TGF-beta 1), and tumor necrosis factor-alpha (TNF-alpha) mRNAs in three axotomy paradigms with distinct functional outcomes. Axotomy of adult rat facial motoneurons results in neuronal regeneration, axotomy of neonatal facial motoneurons results in neuronal apoptosis, and axotomy of rubrospinal neurons results in neuronal atrophy. Our RT-PCR findings show that a significant and sustained upregulation of IL-6 mRNA is associated uniquely with the regeneration of adult facial motoneurons. Histochemical studies using IL-6 immunohistochemistry show intense IL-6 immunoreactivity in axotomized adult facial motoneurons. Assessment of reactive glial changes with astroglial and microglial markers reveals that the reactive gliosis following adult facial nerve axotomy is more intense than that observed in either of the other two paradigms. Exposure of cultured microglial cells to IL-6 stimulates microglial proliferation in a dose-dependent manner. Cultured microglia also show expression of IL-6 receptor mRNA, as determined by RT-PCR. Our findings support the idea that reactive gliosis is required for neuron regeneration to occur, and more specifically, they suggest that neuron-derived IL-6 serves as a signalling molecule that induces microglial proliferation during motoneuron regeneration.

Neurocan is upregulated in injured brain and in cytokine-treated astrocytes

Injury to the CNS results in the formation of the glial scar, a primarily astrocytic structure that represents an obstacle to regrowing axons. Chondroitin sulfate proteoglycans (CSPG) are greatly upregulated in the glial scar, and a large body of evidence suggests that these molecules are inhibitory to axon regeneration. We show that the CSPG neurocan, which is expressed in the CNS, exerts a repulsive effect on growing cerebellar axons. Expression of neurocan was examined in the normal and damaged CNS. Frozen sections labeled with anti-neurocan monoclonal antibodies 7 d after a unilateral knife lesion to the cerebral cortex revealed an upregulation of neurocan around the lesion. Western blot analysis of extracts prepared from injured and uninjured tissue also revealed substantially more neurocan in the injured CNS. Western blot analysis revealed neurocan and the processed forms neurocan-C and neurocan-130 to be present in the conditioned medium of highly purified rat astrocytes. The amount detected was increased by transforming growth factor beta and to a greater extent by epidermal growth factor and was decreased by platelet-derived growth factor and, to a lesser extent, by interferon gamma. O-2A lineage cells were also capable of synthesizing and processing neurocan. Immunocytochemistry revealed neurocan to be deposited on the substrate around and under astrocytes but not on the cells. Astrocytes therefore lack the means to retain neurocan at the cell surface. These findings raise the possibility that neurocan interferes with axonal regeneration after CNS injury.