promotion-survival-differentiation-neural-stem-cells-with-fibrin

Promotion of Survival and Differentiation of Neural Stem Cells with Fibrin and Growth Factor Cocktails after Severe Spinal Cord Injury

Neural stem cells (NSCs) can self-renew and differentiate into neurons and glia. Transplanted NSCs can replace lost neurons and glia after spinal cord ...

University of California, San Diego

Campylobacter fetus is a Gram-negative bacterial pathogen of humans and ungulates and is normally transmitted via ingestion of contaminated food or water with infection resulting in mild to severe enteritis. However, despite clinical evidence that C. fetus infection often involves transient bacteremic states from which systemic infection may develop and the frequent isolation of C. fetus from extra-intestinal sites, this organism displays very poor invasiveness in in vitro models of infection. In this study, immunofluorescence microscopy and gentamicin protection assays were used to investigate the ability of six clinical isolates and one reference strain of C. fetus to adhere to and invade the human intestinal epithelial cell line, INT 407. During an initial 4-h infection period, all C. fetus strains were detected intracellularly using both techniques, though adherence and internalization levels were very low when determined from gentamicin protection assays. Microscopy results indicated that during a 4-h infection period, four of the five clinical strains tested were adherent to 41.3-87.3% of INT 407 cells observed and that 25.2-34.6% of INT 407 cells contained intracellular C. fetus. The C. fetus reference strain displayed the lowest levels of adherence and internalization. A modified infection assay revealed that C. fetus adherence did not necessarily culminate in internalization. Despite the large percentage of INT 407 cells with adherent bacteria, the percentage of INT 407 cells with intracellular bacteria remained unchanged when incubation was extended from 4 h to 20 h. However, microscopy of INT 407 cells 24 h postinfection (p.i.) revealed that infected host cells contained clusters of densely packed C. fetus cells. Gentamicin protection assays revealed that intracellular C. fetus cells were not only viable 24 h p.i. but also that C. fetus had increased in number approximately three- to fourfold between 4 and 24 h p.i., indicative of intracellular replication. Investigation of the role of the host cell cytoskeleton revealed that pretreatment of host cells with cytochalasin D, colchicine, vinblastine, taxol, or dimethyl sulfoxide (DMSO) did not impact upon C. fetus adherence or internalization of INT 407 cells. Microscopy indicated neither rearrangement nor colocalization of either microtubules or microfilaments in INT 407 cells in response to C. fetus adherence or internalization. Together, these data indicate that clinical isolates of C. fetus are capable of adhering, entering, and surviving within the nonphagocytic epithelial cell line, INT 407.

Campylobacter fetus adheres to and enters INT 407 cells.

Olfactory ensheathing cells (OECs) have been reported to migrate long distances and to bridge lesion sites, guiding axonal regeneration after spinal cord injury (SCI). To understand mechanisms of OEC migration and axonal guidance, we injected lamina propria OECs 1 mm rostral and caudal to C4 SCI sites. One month later, OECs formed an apparent migrating cell tract continuously extending from the injection site through the lesion, physically bridging the lesion. Confocal immunolabeling demonstrated that, whereas this cell tract displaced host astrocytes, descending or ascending long tract axons did not preferentially extend into the cell tract and OECs failed to support bridging of corticospinal axons. Notably, the "bridging" tract of OECs formed within 1 h of cell injection, raising the possibility that cells passively spread from the pressure injection site rather than actively migrating. Control injections of bone marrow stromal cells (MSCs) or fibroblasts 1 mm from the lesion site also rapidly dispersed into the lesion cavity. Cell tracts extending into the lesion site were not seen when cells were injected either at low volumes, into spinal cord gray matter, or 3 d before or 9 d after SCI. OECs proliferated in injection sites, cell tracts, and lesion sites, indicating that OECs can also accumulate through cell proliferation. Thus, OECs do not appear to exhibit significant migratory properties when grafted to the spinal cord, exhibit no detectable difference in promoting axon growth into a SCI site compared with MSCs or fibroblasts, and do not support bridging of corticospinal axons beyond a dorsal column lesion.

Olfactory ensheathing cells do not exhibit unique migratory or axonal growth-promoting properties after spinal cord injury.

Two reasons may be responsible for the poor grasp of the linguistic concepts related to literacy acquisition by preservice and in-service teachers: a lack of attention given to such concepts by teacher educators (college faculty members) and a lack of relevant information provided in the textbooks used in college courses. In an earlier study, the authors found that many teacher educators involved in the training of preservice and in-service teachers were not well acquainted with these concepts. In this study, the authors examined the extent to which textbooks used in reading education courses contain the information about the five components of literacy instruction (phonemic awareness, phonics, fluency, vocabulary, and text comprehension) recommended by the National Reading Panel. Such scrutiny shows that many textbooks do not adequately cover these five components and the related instructional procedures for teaching them. In addition to the paucity of information about teaching the five components, some textbooks present inaccurate information.

Do textbooks used in university reading education courses conform to the instructional recommendations of the national reading panel?

We subjected rats to either partial midcervical or complete upper thoracic spinal cord transections and examined whether combinatorial treatments support motor axonal regeneration into and beyond the lesion. Subjects received cAMP injections into brainstem reticular motor neurons to stimulate their endogenous growth state, bone marrow stromal cell grafts in lesion sites to provide permissive matrices for axonal growth, and brain-derived neurotrophic factor gradients beyond the lesion to stimulate distal growth of motor axons. Findings were compared with several control groups. Combinatorial treatment generated motor axon regeneration beyond both C5 hemisection and T3 complete transection sites. Yet despite formation of synapses with neurons below the lesion, motor outcomes worsened after partial cervical lesions and spasticity worsened after complete transection. These findings highlight the complexity of spinal cord repair and the need for additional control and shaping of axonal regeneration.

Motor axonal regeneration after partial and complete spinal cord transection.

Training the Biofilm Generation--a tribute to J. W. Costerton.

Neural stem cells (NSCs) expressing GFP were embedded into fibrin matrices containing growth factor cocktails and grafted to sites of severe spinal cord injury. Grafted cells differentiated into multiple cellular phenotypes, including neurons, which extended large numbers of axons over remarkable distances. Extending axons formed abundant synapses with host cells. Axonal growth was partially dependent on mammalian target of rapamycin (mTOR), but not Nogo signaling. Grafted neurons supported formation of electrophysiological relays across sites of complete spinal transection, resulting in functional recovery. Two human stem cell lines (566RSC and HUES7) embedded in growth-factor-containing fibrin exhibited similar growth, and 566RSC cells supported functional recovery. Thus, properties intrinsic to early-stage neurons can overcome the inhibitory milieu of the injured adult spinal cord to mount remarkable axonal growth, resulting in formation of new relay circuits that significantly improve function. These therapeutic properties extend across stem cell sources and species.

Long-distance growth and connectivity of neural stem cells after severe spinal cord injury.

Campylobacter fetus is a Gram negative bacterium recognized for its virulence in animals and humans. This bacterium possesses a paracrystalline array of high molecular weight proteins known as surface-layer proteins covering its cell surface. A mathematical model has been made of the outer membrane of this bacterium, both with its surface-layer proteins (S+) and without (S-). Monte Carlo computer simulation was used to understand the stability of the surface-layer protein structure as a function of ionic concentration. The interactions of an electrically-charged antimicrobial agent, the cationic antimicrobial peptide protamine, with surface-layer proteins and with the lipopolysaccharides of the outer membrane were modeled and analyzed. We found that (1) divalent ions stabilize the surface-layer protein array by reducing the fluctuations perpendicular and parallel to the membrane plane thereby promoting adhesion to the LPS region. This was achieved via (2) divalent ions bridging the negatively-charged LPS Core. The effect of this bridging is to bring individual Core regions closer together so that the O-antigens can (3) increase their attractive van der Waals interactions and "collapse" to form a surface with reduced perpendicular fluctuations. These findings provide support for the proposal of Yang et al. [1]. (4) No evidence for a significant increase in Ca(2+) concentration in the region of the surface-layer protein subunits was observed in S+ simulations compared to S- simulations. (5) We predicted the trends of protamine MIC tests performed on C. fetus and these were in good agreement with our experimental results.

Modeling the surface of Campylobacter fetus: protein surface layer stability and resistance to cationic antimicrobial peptides.

Vibrio parahaemolyticus is a significant human pathogen associated with gastroenteritis. Two V. parahaemolyticus type 3 secretion systems, T3SS-1 and T3SS-2, secrete effector proteins and have been implicated in host-cell cytotoxicity and enterotoxicity, respectively. Vibrio parahaemolyticus T3SS-1 substrates have been identified, although many predicted substrates (based on homologies) remain undetected in secreted fractions and therefore uncharacterized. We have experimentally developed and optimized a secretion assay protocol allowing for reliable and reproducible detection of V. parahaemolyticus T3SS-1 secreted proteins within culture supernatants. The presence of magnesium and absence of calcium were critical factors in promoting type III secretion of protein substrates. Proteomic approaches identified known V. parahaemolyticus secreted effectors in addition to previously unidentified proteins. Isogenic mutants in putative low calcium response genes were generated, and experiments further implicated the genes in secretion and V. parahaemolyticus-mediated host-cell cytotoxicity during infection. These approaches should be valuable towards future detailed genetic and biochemical analyses of T3SS-1 in V. parahaemolyticus.

Characterization of the type III secretion associated low calcium response genes of Vibrio parahaemolyticus RIMD2210633.

High-level spinal cord injury can lead to cardiovascular dysfunction, including disordered hemodynamics at rest and autonomic dysreflexia during noxious stimulation. To restore supraspinal control of sympathetic preganglionic neurons (SPNs), we grafted embryonic brainstem-derived neural stem cells (BS-NSCs) or spinal cord-derived neural stem cells (SC-NSCs) expressing green fluorescent protein into the T4 complete transection site of adult rats. Animals with injury alone served as controls. Implanting of BS-NSCs but not SC-NSCs resulted in recovery of basal cardiovascular parameters, whereas both cell grafts alleviated autonomic dysreflexia. Subsequent spinal cord retransection above the graft abolished the recovery of basal hemodynamics and reflexic response. BS-NSC graft-derived catecholaminergic and serotonergic neurons showed remarkable long-distance axon growth and topographical innervation of caudal SPNs. Anterograde tracing indicated growth of medullar axons into stem cell grafts and formation of synapses. Thus, grafted embryonic brainstem-derived neurons can act as functional relays to restore supraspinal regulation of denervated SPNs, thereby contributing to cardiovascular functional improvement.

Lori Graham

Department of Neurosciences

University of California, San Diego

Promotion of Survival and Differentiation of Neural Stem Cells with Fibrin and Growth Factor Cocktails after Severe Spinal Cord Injury