Novel Cytosine Deaminase Fusion Gene Enhances the Effect of Radiation on Breast Cancer in Bone by Reducing Tumor Burden, Osteolysis, and Skeletal Fracture

BACKGROUND

Painful breast carcinoma metastases in bone are a common manifestation of malignant disease. Eradication of these tumors can be evasive, and as a result, skeletal morbidity increases with disease progression.

EXPERIMENTAL DESIGN

The treatment potential of cytosine deaminase (CD) gene therapy combined with radiation treatment was evaluated in vitro and in vivo using a 4T1 murine breast carcinoma model. 4T1 carcinoma cells were transduced with a fusion gene encoding the extracellular and transmembrane domains of the human nerve growth factor receptor and the cytoplasmic portion of the yeast CD gene (NGFR-CD(y)).

RESULTS AND CONCLUSIONS

CD-expressing tumor cells (4TCD(y)) were highly sensitive to treatment by 5-fluorocytosine prodrug (P < 0.0001). 5-Fluorocytosine treatment of 4TCD(y), but not 4T1 cells, enhanced the effects of radiation in vitro (P < 0.0001). 5-Fluorocytosine prodrug treatment also increased the therapeutic potential of radiation in vivo. Mice with 4TCD(y) intrafemoral tumors showed increased effectiveness of radiation based on improved reductions in tumor size, reductions in tumorigenic osteolysis, and a decrease in skeletal fractures (P < 0.01).

State-level adjusted ESRD incident rates: use of observed vs model-predicted category-specific rates

Because of differences in case-mix across states, state-level case-mix-adjusted end-stage renal disease (ESRD) incident rates are reported in each United States Renal Data System Annual Data Report to make the across-state comparisons valid. The adjusted rates were estimated by the direct adjustment method, a widely used method for adjusted event rate calculation, based on observed category-specific ESRD incident rates in each state (called the observation-based method). However, when some adjusting categories in a state are small, the adjusted rate and the standard error for this state as estimated by this method may be inaccurate. This report proposes a model-based method that can overcome the disadvantages of the observation-based method and can be extended to continuous adjusting variables. National ESRD incident data and national population data from 1990 to 1999 were used. State-level adjusted ESRD incident rates were estimated by both the observation- and the model-based methods. For the model-based method, a Poisson regression model was used to estimate category-specific ESRD incident rates. For large-population states, both observation- and model-based methods produced similar estimates for adjusted ESRD incident rates. For small-population states, however, the observation-based method produced year-to-year estimates of adjusted ESRD incident rates that varied considerably and also had very large standard errors. In contrast, the model-based method produced stable estimates. The model-based method can overcome the disadvantages of the observation-based method for estimating state-level adjusted ESRD incident rates, especially for small states.

Differential BBB interactions of three ingestive peptides: obestatin, ghrelin, and adiponectin

Endogenous compounds, including ingestive peptides, can interact with the blood-brain barrier (BBB) in different ways. Here we used in vivo and in vitro techniques to examine the BBB permeation of the newly described satiety peptide obestatin. The fate of obestatin in blood and at the BBB was contrasted with that of adiponectin. By the sensitive multiple time-regression method, obestatin appeared to have an extremely fast influx rate to the brain whereas adiponectin did not cross the BBB. HPLC analysis, however, showed the obestatin result to be spurious, reflecting rapid degradation. Absence of BBB permeation by obestatin and adiponectin was in contrast to the saturable transport of human ghrelin reported previously. As a positive control, ghrelin showed saturable binding and endocytosis in RBE4 cerebral microvessel endothelial cells. By comparison, obestatin lacked specific binding and endocytosis, and the small amount internalized showed rapid intracellular degradation before the radioactivity was released by exocytosis. The differential interactions of obestatin, adiponectin, and ghrelin with the BBB illustrate their distinctive physiological interactions with the CNS.

Receptor-mediated transport of LIF across blood-spinal cord barrier is upregulated after spinal cord injury

Leukemia inhibitory factor (LIF) crosses the normal blood-brain and blood-spinal cord barrier (BBB) by a saturable transport system [Pan, W., Kastin, A.J., Brennan, J.M., 2000. Saturable entry of leukemia inhibitory factor from blood to the central nervous system. J. Neuroimmunol. 106, 172-180]. Since LIF is a cytokine beneficial to spinal cord regeneration, understanding the regulation of its transport across the injured BBB may help in the design of strategies for the treatment of spinal cord injury (SCI). In this study, we initially showed that transport of LIF is mediated by its specific receptor LIFRalpha (gp190), using both adult mice and monolayers of mouse brain microvessel endothelial cells. Permeation of radioactively labeled LIF was inhibited not only by excess unlabeled LIF, but also by a blocking antibody to the extracellular domain of gp190 LIFRalpha receptor. This showed that the saturable transport of LIF across the BBB involves LIFRalpha. We then tested the hypothesis that this transport system can be upregulated after SCI. SCI was generated by an established compression method at the upper lumbar level. Transport was studied 1 week after SCI, a time of tissue repair following ischemia and inflammation. Spinal cord uptake of 99mTc-albumin 10 min after intravenous injection was used as an indicator of paracellular permeability of the BBB, its small but significant increase at the injury site indicating the level of persistent BBB disruption. The uptake of 125I-LIF by the injured lumbar spinal cord was significantly greater than that in the uninjured controls as well as that of 99mTc-albumin. Both excess unlabeled LIF and the blocking antibody against LIFRalpha significantly suppressed the increased entry of 125I-LIF without affecting that of 99mTc-albumin. Thus, the increased blood-to-spinal cord permeation of LIF was not solely explained by barrier disruption but involved LIFRalpha. This enhanced transport correlated with increased expression of LIFRalpha shown by immunofluorescent staining and Western blot. Therefore, LIFR at the BBB provides an important target for therapeutic intervention.

Intervalley gap anomaly of two-dimensional electrons in silicon

We report here a systematic study of the energy gaps at the odd-integer quantum Hall states nu = 3 and 5 under tilted magnetic (B) fields in a high quality Si two-dimensional electron system. Out of the coincidence region, the valley splitting is independent of the in-plane fields. However, the nu = 3 valley gap differs by about a factor of 3 (Deltav approximately 0.4 vs 1.2 K) on different sides of the coincidence. More surprisingly, instead of reducing to zero, the energy gaps at nu = 3 and 5 rise rapidly when approaching the coincidence angles. We believe that such an anomaly is related to strong couplings of the nearly degenerate Landau levels.

Stroke upregulates TNFalpha transport across the blood-brain barrier

To determine how cytokine transport systems at the blood-brain barrier (BBB) participate in stroke progression and recovery, we generated a mouse model of transient middle cerebral artery occlusion (tMCAO). After 1 h of occlusion followed by nearly complete reperfusion, the neurological deficits lasted more than a week as shown by several behavioral tests. Despite the prominent infarct area indicated by reduced cerebral perfusion and confirmed by vital staining, the volume of distribution of (131)I-albumin in various brain regions was not significantly altered over time (12 h to 14 days). In sharp contrast, the blood-to-brain permeation of 125I-TNFalpha was significantly increased 5 days after tMCAO. Furthermore, excess unlabeled TNFalpha abolished this enhanced 125I-TNFalpha uptake. Thus, not only did the known saturable transport system for TNFalpha persist, but it functioned at a higher capacity in tMCAO mice. Upregulation of TNFR1 and TNFR2 partially explains the increased transport, as mRNA for both receptors showed the most pronounced increase (15-fold and 30-fold, respectively) in the ischemic hemisphere 5-7 days after tMCAO. However, even in the hemisphere contralateral to the ischemia induced by stroke, there was increased TNFalpha transport. The bilateral increase in 125I-TNFalpha entry from blood to brain suggests that TNFalpha trafficking in cerebral endothelial cells is influenced by global mediators in addition to the transporting receptors. Given the known multiple modulatory effects of TNFalpha after stroke, the results indicate that the TNFalpha transport system at the BBB facilitates neuroplasticity and plays an important role in stroke recovery.

cisRED: a database system for genome-scale computational discovery of regulatory elements

We describe cisRED, a database for conserved regulatory elements that are identified and ranked by a genome-scale computational system (www.cisred.org). The database and high-throughput predictive pipeline are designed to address diverse target genomes in the context of rapidly evolving data resources and tools. Motifs are predicted in promoter regions using multiple discovery methods applied to sequence sets that include corresponding sequence regions from vertebrates. We estimate motif significance by applying discovery and post-processing methods to randomized sequence sets that are adaptively derived from target sequence sets, retain motifs with p-values below a threshold and identify groups of similar motifs and co-occurring motif patterns. The database offers information on atomic motifs, motif groups and patterns. It is web-accessible, and can be queried directly, downloaded or installed locally.

Osteoclasts direct bystander killing of cancer cells in vitro

Cytosine deaminase (CD) catalyzes the deamination of 5-fluorocytosine (5FC) to produce the highly toxic chemotherapeutic agent 5-fluorouracil (5FU). A unique feature of the CD/5FC enzyme/prodrug system is its ability to kill adjacent cells via bystander killing. Bystander killing of cancer cells can be mediated by non-cancerous accessory cells transduced with the CD gene; one type of non-cancerous accessory cell found in primary bone cancer and breast cancer metastases to bone is the osteoclast. This manuscript determines if osteoclast precursor cells, transduced with the CD gene, can function as a gene delivery system capable of killing cancer cells. An osteoclast precursor cell line (RAW 264.7, RAW) and authentic bone marrow-derived osteoclast precursor cells were transduced with a retroviral vector containing the cytosine deaminase fusion gene (NCD) composed of the human nerve growth factor receptor and CD genes. RAW cells and bone marrow-derived osteoclast precursor cells transduced with NCD expressed NCD protein and converted 5FC to 5FU. Treatment of NCD-transduced osteoclast precursor cells with the 5FC prodrug resulted in significant killing in vitro. NCD-transduced osteoclasts were co-cultured with either DsRed2-labeled sarcoma cells (2472-DSR) or green fluorescent protein (GFP)-labeled breast cancer cells (GFP-4T1). Treatment of the NCD osteoclast/tumor cell co-cultures with 5FC resulted in bystander killing of 2472-DSR cells (P < 0.006) and GFP-4T1 cells (P < 0.004). These findings demonstrate that NCD-transduced osteoclasts can promote killing of cancer cells and introduce the exciting possibility for developing osteoclast-mediated, CD-based treatment of primary bone cancers and breast cancer metastases to bone.

Circadian and extracircadian exploration during daytime hours of circulating corticosterone and other endocrine chronomes

During 7 consecutive days, blood and several tissues were collected during daytime working hours only, three times per day at 4-h intervals from inbred Wistar rats, which had been previously standardized for 1 month in two rooms on a regimen of 12 h of light (L) alternating with 12 h of darkness (LD12:12). In one room, lights were on from 09:00 to 21:00 and in the other room, lights were on from 21:00 to 09:00 (DL12:12; reversed lighting regimen). This setup provides a convenient design to study circadian and extracircadian variations over long (e.g., 7-day) spans. Prior checking of certain circadian rhythms in animals reared in the room on reversed lighting (DL) as compared with animals in the usual (LD) regimen provided evidence that the 180 degrees phase-shift had occurred. These measurements were limited to the circadian (and not extended to infradian) variation. As marker rhythm, the core temperature of a subsample of rats was measured every 4 h around the clock (by night as well as by day) before the start of the 7-day sampling. An antiphase of the circadian rhythm in core temperature was thus demonstrated between rats in the LD vs. DL rooms. A sex difference in core temperature was also found in each room. A reversed rhythm in animals kept in DL and an antiphase between rats kept in DL vs. LD was again shown for the circulating corticosterone rhythm documented in subsamples of 8 animals of each sex sampled around the clock during the first approximately 1.5 day of the 7-day sampling. The findings were in keeping with the proposition that sampling rats at three timepoints 4 h apart during daytime from two rooms on opposite lighting regimens allows the assessment of circadian changes, the daytime samples from animals kept on the reversed lighting regimen accounting for the samples that would have to be obtained by night from animals kept in the room with the usual lighting regimen. During the 7-day-long follow-up, circadian and extracircadian spectral components were mapped for serum corticosterone, taking into account the large day-to-day variability. A third check on the synchronization of the animals to their respective lighting regimen was a comparison (and a good agreement) between studies carried out earlier on the same variables and the circadian results obtained on core temperature and serum corticosterone in this study as a whole. The present study happened to start on the day of the second extremum of a moderate double magnetic storm. The study of any associations of corticosterone with the storm is beyond our scope herein, as are the results on circulating prolactin, characterized by a greater variability and a larger sex difference than corticosterone. Sex differences and extracircadian aspects of prolactin and endothelin determined in the same samples are reported elsewhere, as are results on melatonin. Prior studies on melatonin were confirmed insofar as a circadian profile is concerned by sampling on two antiphasic lighting regimens, as also reported elsewhere. Accordingly, a circadian map for the rat will eventually be extended by the result of this study and aligned with other maps with the qualification of the unassessed contribution in this study of a magnetic storm.

Chronomics, neuroendocrine feedsidewards and the recording and consulting of nowcasts--forecasts of geomagnetics

A multi-center four-hourly sampling of many tissues for 7 days (00:00 on April 5-20:00 to April 11, 2004), on rats standardized for 1 month in two rooms on antiphasic lighting regimens happened to start on the day after the second extremum of a moderate double magnetic storm gauged by the planetary geomagnetic Kp index (which at each extremum reached 6.3 international [arbitrary] units) and by an equatorial index Dst falling to -112 and -81 nT, respectively, the latter on the first day of the sampling. Neuroendocrine chronomes (specifically circadian time structures) differed during magnetically affected and quiet days. The circadian melatonin rhythm had a lower MESOR and lower circadian amplitude and tended to advance in acrophase, while the MESOR and amplitude of the hypothalamic circadian melatonin rhythm were higher during the days with the storm. The circadian parameters of circulating corticosterone were more labile during the days including the storm than during the last three quiet days. Feedsidewards within the pineal-hypothalamic-adrenocortical network constitute a mechanism underlying physiological and probably also pathological associations of the brain and heart with magnetic storms. Investigators in many fields can gain from at least recording calendar dates in any publication so that freely available information on geomagnetic, solar and other physical environmental activity can be looked up. In planning studies and before starting, one may gain from consulting forecasts and the highly reliable nowcasts, respectively.

Selective tissue uptake of agouti-related protein(82-131) and its modulation by fasting

The blood concentration of agouti-related protein (AgRP), a protein related to hyperphagia and obesity, is increased in obese human and fasted lean subjects. Because there is no saturable transport system at the blood-brain barrier for circulating AgRP to reach its central nervous system target, uptake of AgRP by peripheral organs might be physiologically meaningful. Using the biologically active fragment AgRP(82-131), we determined the pharmacokinetics of its radioactively labeled tracer after iv bolus injection and compared it with that of the vascular marker albumin. AgRP enters peripheral organs at different influx rates, all of which were higher than into brain and spinal cord. At 10 min after iv injection, the radioactivity recovered in the liver, which had the fastest influx rate for AgRP, represented intact (125)I-AgRP. The adrenal gland had a moderately fast uptake (but the highest initial volume of distribution), followed by the heart, lungs, and skeletal muscle. By comparison, epididymal fat, testis, and pancreas had low permeability to AgRP. Saturation of influx was determined by coadministration of excess unlabeled AgRP and was shown to be present in the liver and adrenal gland. The influx rate and initial volume of distribution did not show a linear correlation with vascular permeability or regional blood flow. AgRP uptake by the liver and epididymal fat was significantly increased by overnight fasting, whereas that by the adrenal gland was significantly decreased in fasted mice. Thus, the differential uptake of AgRP by peripheral organs could be a regulated process that is modulated by food deprivation.

Permeation of growth hormone across the blood-brain barrier

Exogenous GH can affect central nervous system function when given peripherally to animals and as a supplemental therapy to humans. This study tested whether GH crosses the blood-brain barrier (BBB) by a specific transport system and found that both mice and rats have small but significant uptake of GH into the brain without a species difference. Determined by multiple-time regression analysis, the blood-to-brain influx transfer constants of 125I-labeled rat GH in mice (0.23+/-0.07 microl/g.min) and rats (0.32+/-0.04 microl/g.min) were comparable to those of some cytokines of similar size, with a half-time disappearance of 125I-GH of 3.8-7.6 min in blood. Intact 125I-GH was present in both serum and brain homogenate 20 min after iv injection. At this time, about 26.8% of GH in brain entered the parenchyma, whereas 10% was entrapped in endothelial cells. Neither excess GH nor insulin showed acute modulation of the influx, indicating lack of a saturable transport system for GH at the BBB. Binding and cellular uptake studies in cultured cerebral microvessel endothelial cells (RBE4) further ruled out the presence of high-capacity adsorptive endocytosis. The brain influx of GH by simple diffusion adds definitive value to the long-disputed question of whether and how GH crosses the BBB. The central nervous system effects of peripheral GH can be attributed to permeation of the BBB despite the absence of a specific transport system.

Chronomics reveal and quantify circadian rhythmic melatonin in duodenum of rats

A circadian rhythm is documented in duodenal melatonin in rats, peaking 16.8 hours after light onset. This component is more readily detected after log10-transformation of the data. It differs between male and female rats, females having a larger circadian amplitude and an earlier acrophase. The circadian rhythm in duodenal melatonin is also found to lead that of pineal melatonin. The results are qualified by the presence at the start of mapping of the second extremum of a double magnetic storm.

Chronomics: circadian lead of extrapineal vs. pineal melatonin rhythms with an infradian hypothalamic exploration

A circadian rhythm is documented for plasma, pineal, and hypothalamic melatonin of male and female rats kept on staggered lighting regimens. Log[_10]-transformation of the data usually normalizes, when need be, the distribution of residuals from the 24-hour cosine curve fits. A tentative circadian acrophase chart is presented that shows a lead in circadian acrophase of duodenal over pineal melatonin. The use of antiphasic lighting regimens facilitates circadian studies that can be carried out for several days, thereby allowing the assessment of infradian components such as a circasemiseptan variation in hypothalamic melatonin documented herein. The results are qualified by the presence of a second extremum of a double magnetic storm at the start of mapping.

Impact of school-based health centers on children with asthma

PURPOSE

To quantitatively assess the impact of school-based health centers (SBHCs) on hospitalization and emergency department (ED) visits for children with asthma.

METHODS

The study was conducted at four SBHC intervention school districts and two comparable non-SBHC school districts in Greater Cincinnati, Ohio. A longitudinal quasi-experimental time-series repeated measures design was used with a study period from 1997 to 2003. Children with asthma with at least 2 years of continuous enrollment who had medical claims for asthma diagnosis and antiasthmatic medications were selected. The primary data sources were student enrollment data from the schools and the Ohio Medicaid claims database. Generalized estimating equation (GEE) analysis and analysis of covariance were used to assess the intervention effect before and after the SBHC program.

RESULTS

Asthma was one of the major diseases for SBHC encounters. Major prescription drugs that SBHC staff managed for children with asthma included albuterol, montelukast, fluticasone, budesonide, and triamcinolone. Of 273 children (196 in SBHC schools and 77 in non-SBHC schools), 42% were female, 41.7% African-Americans, and the average age was 8.2 years. After the opening of the SBHC, relative risks of hospitalization and ED visits in the SBHC group decreased 2.4-fold and 33.5%, respectively. The cost of hospitalization per child decreased significantly over time for children in SBHC schools (F = 4.115, p = .044). After SBHCs opened, cost of hospitalization decreased for African-American children (F = 5.198, p = .023). Costs of ED visits for children in SBHC schools were significantly lower than children in non-SBHC schools (F = 19.8, p < .0001).

CONCLUSIONS

The risk of hospitalization and ED visits for children with asthma decreased significantly with SBHC programs. The potential cost-savings for hospitalization was estimated as 970 dollars per child.

Chronomics affirm extending scope of lead in phase of duodenal vs. pineal circadian melatonin rhythms

In Göttingen, Germany, circadian variations in melatonin had been determined time-macroscopically in pineal glands, blood plasma and duodenum of chicken and rats. When these data were meta-analyzed, they agreed with the results from an independent survey on tissues from rats collected in a laboratory in Pécs, Hungary. In the latter study, tissues were analyzed chemically in Bratislava, Slovakia, and numerically in Minneapolis, MN, USA, all by single- and multiple-component cosinor and parameter tests. In rats and chickens, these inferential statistical procedures clearly demonstrated a lead in phase of the 24-h cosine curves best fitting all of the duodenal vs. those best fitting all of the pineal melatonin values in each species in 2 geographic (geomagnetic) locations. The 24-h cosine curve of circulating melatonin was found to be in an intermediate phase position. Mechanisms of the phase differences and the contribution of gastrointestinal melatonin to circulating hormone concentrations are discussed.

Quantization of the diagonal resistance: density gradients and the empirical resistance rule in a 2D system

We have observed quantization of the diagonal resistance, R(xx), at the edges of several quantum Hall states. Each quantized R(xx) value is close to the difference between the two adjacent Hall plateaus in the off-diagonal resistance, R(xy). Peaks in R(xx) occur at different positions in positive and negative magnetic fields. Practically all R(xx) features can be explained quantitatively by a 1%/cm electron density gradient. Therefore, R(xx) is determined by R(xy) and unrelated to the diagonal resistivity rho(xx). Our findings throw an unexpected light on the empirical resistivity rule for 2D systems.

Strategies to Create a Regenerating Environment for the Injured Spinal Cord

Spine cord injury (SCI) leads to devastating functional loss below the level of injury. Partially explained by the presence of a non-permissive environment, the injured spinal cord does not mount adequate regeneration to re-establish functional connections. Therefore, it is important to identify the cellular and molecular factors and their interactions that affect axonal regeneration within the changed environment. This review will discuss the current understanding of the neuronal and glial factors and the extracellular matrix in the spinal cord that inhibit axonal growth, and it will summarize some major approaches for facilitation of regeneration. The strategies are classified into the following categories: penetration of the blood-brain barrier; modulation of caspase activity to reduce apoptosis; stem cells and tissue implantation; administration of neurotrophic factors, including viral vector-mediated delivery; and modulation of the extracellular matrix. Although recent studies on genomic regulation and apoptosis have identified particularly important molecular targets, more is necessary to achieve long-term regeneration. A combination of the approaches targeting various aspects in the regenerating environment would be more effective than a single strategy. Overall, insights arising from the experimental results may eventually lead to better therapeutic intervention so as to lessen the functional disability and enhance the quality of life in patients with SCI.

Targeting Neurite Growth Inhibitors to Induce CNS Regeneration

Prominent among the several endogenous inhibitors known to limit recovery and plasticity after CNS injury are Nogo (neurite outgrowth inhibitor) and MAG (myelin associated glycoprotein). The effects of these inhibitors on axonal regeneration can be reduced by administration of specific antagonists, some of which are commercially available for experimental investigation. There are three aspects of therapeutic manipulations: targeting the inhibitory proteins, antagonizing the known receptor, and inhibiting the intracellular signal transduction of these inhibitory molecules. Infusion of an antibody against Nogo improves behavioral deficits and enhances corticospinal tract regeneration in animals after stroke and spinal cord injury (SCI). Similarly, peripheral injection of a mouse monoclonal antibody directed against MAG results in dramatic preferential motor reinnervation in mice after transection of the femoral nerve, indicating that interference with the repellant function of MAG facilitates reinnervation of correct pathways by motor neurons. Further, antagonism of the Nogo receptor by the peptide NEP 1-40 (Nogo extracellular peptide residues 1-40) can promote axonal regeneration in rats after SCI. Blockade of signal transduction also can be effective. The p75 neurotrophin receptor probably represents the signaling part of the receptor complex for neurite growth inhibitors. There is evidence in vitro that the inhibitory actions of MAG and myelin are blocked if neurons are primed with a variety of neurotrophins. Thus, there are several therapeutic approaches to overcome the actions of endogenous neurite growth inhibitors so as to promote CNS regeneration.

Neural Plasticity After Spinal Cord Injury

Spinal cord injury (SCI) has devastating physical and socioeconomical impact. However, some degree of functional recovery is frequently observed in patients after SCI. There is considerable evidence that functional plasticity occurs in cerebral cortical maps of the body, which may account for functional recovery after injury. Additionally, these plasticity changes also occur at multiple levels including the brainstem, spinal cord, and peripheral nervous system. Although the interaction of plasticity changes at each level has been less well studied, it is likely that changes in subcortical levels contribute to cortical reorganization. Since the permeability of the blood-brain barrier (BBB) is changed, SCI-induced factors, such as cytokines and growth factors, can be involved in the plasticity events, thus affecting the final functional recovery after SCI. The mechanism of plasticity probably differs depending on the time frame. The reorganization that is rapidly induced by acute injury is likely based on unmasking of latent synapses resulting from modulation of neurotransmitters, while the long-term changes after chronic injury involve changes of synaptic efficacy modulated by long-term potentiation and axonal regeneration and sprouting. The functional significance of neural plasticity after SCI remains unclear. It indicates that in some situations plasticity changes can result in functional improvement, while in other situations they may have harmful consequences. Thus, further understanding of the mechanisms of plasticity could lead to better ways of promoting useful reorganization and preventing undesirable consequences.