Publications by authors named "Martha I Betancur"

5 Publications

  • Page 1 of 1

Enriching neural stem cell and anti-inflammatory glial phenotypes with electrical stimulation after traumatic brain injury in male rats.

J Neurosci Res 2021 Jul 26;99(7):1864-1884. Epub 2021 Mar 26.

Department of Biomedical Engineering, Pratt School of Engineering, Duke University, Durham, NC, USA.

Traumatic brain injury (TBI) by an external physical impact results in compromised brain function via undesired neuronal death. Following the injury, resident and peripheral immune cells, astrocytes, and neural stem cells (NSCs) cooperatively contribute to the recovery of the neuronal function after TBI. However, excessive pro-inflammatory responses of immune cells, and the disappearance of endogenous NSCs at the injury site during the acute phase of TBI, can exacerbate TBI progression leading to incomplete healing. Therefore, positive outcomes may depend on early interventions to control the injury-associated cellular milieu in the early phase of injury. Here, we explore electrical stimulation (ES) of the injury site in a rodent model (male Sprague-Dawley rats) to investigate its overall effect on the constituent brain cell phenotype and composition during the acute phase of TBI. Our data showed that a brief ES for 1 hr on day 2 of TBI promoted anti-inflammatory phenotypes of microglia as assessed by CD206 expression and increased the population of NSCs and Nestin astrocytes at 7 days post-TBI. Also, ES effectively increased the number of viable neurons when compared to the unstimulated control group. Given the salience of microglia and neural stem cells for healing after TBI, our results strongly support the potential benefit of the therapeutic use of ES during the acute phase of TBI to regulate neuroinflammation and to enhance neuroregeneration.
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http://dx.doi.org/10.1002/jnr.24834DOI Listing
July 2021

Engineered glycomaterial implants orchestrate large-scale functional repair of brain tissue chronically after severe traumatic brain injury.

Sci Adv 2021 Mar 5;7(10). Epub 2021 Mar 5.

Regenerative Bioscience Center, University of Georgia, Athens, GA 30602, USA.

Severe traumatic brain injury (sTBI) survivors experience permanent functional disabilities due to significant volume loss and the brain's poor capacity to regenerate. Chondroitin sulfate glycosaminoglycans (CS-GAGs) are key regulators of growth factor signaling and neural stem cell homeostasis in the brain. However, the efficacy of engineered CS (eCS) matrices in mediating structural and functional recovery chronically after sTBI has not been investigated. We report that neurotrophic factor functionalized acellular eCS matrices implanted into the rat M1 region acutely after sTBI significantly enhanced cellular repair and gross motor function recovery when compared to controls 20 weeks after sTBI. Animals subjected to M2 region injuries followed by eCS matrix implantations demonstrated the significant recovery of "reach-to-grasp" function. This was attributed to enhanced volumetric vascularization, activity-regulated cytoskeleton (Arc) protein expression, and perilesional sensorimotor connectivity. These findings indicate that eCS matrices implanted acutely after sTBI can support complex cellular, vascular, and neuronal circuit repair chronically after sTBI.
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http://dx.doi.org/10.1126/sciadv.abe0207DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7935369PMC
March 2021

Chondroitin Sulfate Glycosaminoglycan Matrices Promote Neural Stem Cell Maintenance and Neuroprotection Post-Traumatic Brain Injury.

ACS Biomater Sci Eng 2017 Mar 13;3(3):420-430. Epub 2017 Feb 13.

Regenerative Bioscience Center, The University of Georgia, 425 River Road, ADS Complex, Athens, Georgia 30602, United States.

There are currently no effective treatments for moderate-to-severe traumatic brain injuries (TBIs). The paracrine functions of undifferentiated neural stem cells (NSCs) are believed to play a significant role in stimulating the repair and regeneration of injured brain tissue. We therefore hypothesized that fibroblast growth factor (FGF2) enriching chondroitin sulfate glycosaminoglycan (CS-GAG) matrices can maintain the undifferentiated state of neural stem cells (NSCs) and facilitate brain tissue repair subacutely post-TBI. Rats subjected to a controlled cortical impactor (CCI) induced TBI were intraparenchymally injected with CS-GAG matrices alone or with CS-GAG matrices containing PKH26GL labeled allogeneic NSCs. Nissl staining of brain tissue 4 weeks post-TBI demonstrated the significantly enhanced ( < 0.05) tissue protection in CS-GAG treated animals when compared to TBI only control, and NSC only treated animals. CS-GAG-NSC treated animals demonstrated significantly enhanced ( < 0.05) FGF2 retention, and maintenance of PKH26GL labeled NSCs as indicated by enhanced Sox1+ and Ki67+ cell presence over other differentiated cell types. Lastly, all treatment groups and sham controls exhibited a significantly ( < 0.05) attenuated GFAP+ reactive astrocyte presence in the lesion site when compared to TBI only controls.
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http://dx.doi.org/10.1021/acsbiomaterials.6b00805DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5937277PMC
March 2017

Chondroitin Sulfate Glycosaminoglycan Hydrogels Create Endogenous Niches for Neural Stem Cells.

Bioconjug Chem 2015 Dec 20;26(12):2336-49. Epub 2015 Oct 20.

Regenerative Bioscience Center, ADS Complex, The University of Georgia , 425 River Road, Athens, Georgia 30602, United States.

Neural stem cells (NSCs) possess great potential for neural tissue repair after traumatic injuries to the central nervous system (CNS). However, poor survival and self-renewal of NSCs after injury severely limits its therapeutic potential. Sulfated chondroitin sulfate glycosaminoglycans (CS-GAGs) linked to CS proteoglycans (CSPGs) in the brain extracellular matrix (ECM) have the ability to bind and potentiate trophic factor efficacy, and promote NSC self-renewal in vivo. In this study, we investigated the potential of CS-GAG hydrogels composed of monosulfated CS-4 (CS-A), CS-6 (CS-C), and disulfated CS-4,6 (CS-E) CS-GAGs as NSC carriers, and their ability to create endogenous niches by enriching specific trophic factors to support NSC self-renewal. We demonstrate that CS-GAG hydrogel scaffolds showed minimal swelling and degradation over a period of 15 days in vitro, absorbing only 6.5 ± 0.019% of their initial weight, and showing no significant loss of mass during this period. Trophic factors FGF-2, BDNF, and IL10 bound with high affinity to CS-GAGs, and were significantly (p < 0.05) enriched in CS-GAG hydrogels when compared to unsulfated hyaluronic acid (HA) hydrogels. Dissociated rat subventricular zone (SVZ) NSCs when encapsulated in CS-GAG hydrogels demonstrated ∼88.5 ± 6.1% cell viability in vitro. Finally, rat neurospheres in CS-GAG hydrogels conditioned with the mitogen FGF-2 demonstrated significantly (p < 0.05) higher self-renewal when compared to neurospheres cultured in unconditioned hydrogels. Taken together, these findings demonstrate the ability of CS-GAG based hydrogels to regulate NSC self-renewal, and facilitate growth factor enrichment locally.
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http://dx.doi.org/10.1021/acs.bioconjchem.5b00397DOI Listing
December 2015

Behavior-dependent coordination of multiple theta dipoles in the hippocampus.

J Neurosci 2009 Feb;29(5):1381-94

Center for Molecular and Behavioral Neuroscience, Rutgers University, Newark, New Jersey 07102, USA.

Theta (4-10 Hz) oscillations in the hippocampus are thought to be important for plasticity, temporal coding, learning, and memory. The hippocampal system has been postulated to have two (or more) rhythmic sources of theta oscillations, but little is known about the behavior-dependent interplay of theta oscillations in different subregions and layers of the hippocampus. We tested rats in a hippocampus-dependent delayed spatial alternation task on a modified T-maze while simultaneously recording local field potentials from dendritic and somatic layers of the dentate gyrus, CA3, and CA1 regions using high-density, 96-site silicon probes. We found that while theta oscillations were generally coherent throughout the hippocampus, the power, coherence, and phase of theta oscillations fluctuated in a layer-specific manner, confirming the presence of multiple interdependent dipoles. Layer-dependent changes in the power and coherence of theta oscillations varied with aspects of both the memory and control (non-mnemonic) tasks, but only a small fraction of the variance could be explained by running speed or acceleration. Furthermore, the phase lag between theta oscillations in the CA3 and CA1 pyramidal layers was significantly smaller on the maze arm approaching the T-junction than on other arms of the alternation task or on comparable segments of control tasks. Overall, our findings reveal a consortium of layer-specific theta dipoles (current sinks and sources) generated by the rhythmic flow of ions into and out of hippocampal cells. Moreover, our data suggest that these different theta generators flexibly coordinate hippocampal regions and layers to support behavioral task performance.
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http://dx.doi.org/10.1523/JNEUROSCI.4339-08.2009DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2768079PMC
February 2009
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