Using human iPSC-derived neural progenitor cells to increase integrin expression in the CNS

Repair of the adult mammalian spinal cord is prohibited by several extrinsic and intrinsic factors. As the CNS matures, growth-promoting proteins such as integrins are developmentally downregulated resulting in a reduced capacity for axonal outgrowth. Integrins are heterodimeric receptors involved in cell-cell and cell-matrix interactions. Specifically, within mature corticospinal tract (CST) axons, integrins are not transported into the axonal compartment. One integrin heterodimer, α9β1, is of particular interest for its ability to promote neurite outgrowth when bound to a component of the injury-induced milieu, tenascin-C. This project aimed to increase integrin expression within the CNS using induced pluripotent stem cell-derived human neural progenitor cells (iPSC-hNPCs). Using immunocytochemistry and western blotting, endogenous integrin expression within iPSC-hNPCs was determined. In addition, overexpression of α9 integrin was achieved using transfection and lentiviral transduction. The capacity of wild type (WT) and α9-hNPCs to extend neurites on tenascin-C was assessed using neurite outgrowth assays. Results revealed increasing α9 integrin expression in hNPCs significantly promoted neurite outgrowth when cultured on tenascin-C. Interestingly, increasing the concentration of human tenascin-C, resulted in increasingly longer neurites from WT hNPCs suggesting hNPCs could actively upregulate integrin expression. Subsequently, WT and α9-hNPCs were transplanted into layer V of the neonatal rat sensorimotor cortex, which projects to the CST. WT and α9-hNPCs survived up to 8 weeks post-transplantation and produced projections along white matter tracts, including areas of the CST. Additionally, hNPCs retained α9-eYFP protein expression in vivo over time and was localised within axonal projections. These results highlight the capabilities of iPSC-hNPCs to promote integrin expression within the rodent CNS presenting one potential avenue to target neuronal replacement following spinal injury. Future research should focus on assessing the regenerative capacity of WT and α9-hNPCs within an injury model concentrating on the ability of these cells to adapt within an injured environment

Antecedents of Attachment Disorganization across the First Year: Interactions among Child and Parent Variables

Disorganized attachmentis seen as reflecting an infant’s lack of strategyfor coping with the stress of the Strange Situation procedure (SSP; Ainsworth et al., 1978) The identification of disorganized attachment by Main and Solomon (1986) generated a large body of research into its antecedents and consequences. Despite these advances, however, 1)few studies have employed a prospective longitudinal designto clarify antecedents of disorganization, and 2)most research has focused on predicting disorganization from single risk factors, rarely investigating possible interactions among child and parent or environmental variables. The current study investigated the development of disorganized attachment across the first year from a prospective longitudinal perspectivefrom 3 –13 months. A primary goal was to employ a transactional modelto predict disorganization at the end of the first year, with a focus on interactions among a variety of child (gender, stressful child characteristics) and parent variables (parenting stress, maternal behaviour, child care)

Behavioural and Affective Precursors to Disorganized Attachment in the Still-face Procedure at 4-months

We explored whether disorganization in the SSP at 13-months could be predicted from infant affect and behaviour in the SFP at 4- months. We hypothesized that infants in disorganized relationships would have the most difficulty regulating their affect and behaviour in the SFP. Infants in disorganized relationships were expected to display greater negativity (e.g., crying, negative vocalizations, stress indicators such as spitting up) throughout the SFP, compared to those in organized relationships

Both Maternal Sensitivity and Atypical Maternal Behavior Independently Predict Attachment Security and Disorganization in Adolescent Mother–infant Dyads

On the basis of these findings, at odds with current models of the origins of secure vs disorganized attachment, the current study examined the association between distinct qualities of maternal interaction and attachment in a single study. The participants in the current study were adolescent mothers and their infants, a population that has been shown to be at substantial developmental risk and to exhibit a range of markedly atypical interactions with their infants (Jaffee, Caspi, Moffitt, Belsky, and Silva, 2001)

Disorganized Attachment and Mother-Toddler Interactive Behavior in a Problem-Solving Task

PURPOSE: To examine emotional and behavioral regulation and Disorganized attachment at 24-months in a high-risk sample of adolescent mother-toddler dyads. RESULTS: Disorganization was associated with 1)increased toddler negativity and a lower quality of experience and 2)decreased levels of maternal support and assistance during the problem-solving tasks. CONCLUSION: These findings offer converging support for the suggestion that Disorganized dyads experience marked difficulties in emotional and behavioral regulation

The extracellular environment of the CNS : influence on plasticity, sprouting, and axonal regeneration after spinal cord injury

Melissa R Andrews and Shmma Quraishe are supported by a research grant from the Biotechnology and Biological Sciences Research Council (BBSRC).The extracellular environment of the central nervous system (CNS) becomes highly structured and organized as the nervous system matures. The extracellular space of the CNS along with its subdomains plays a crucial role in the function and stability of the CNS. In this review, we have focused on two components of the neuronal extracellular environment, which are important in regulating CNS plasticity including the extracellular matrix (ECM) and myelin. The ECM consists of chondroitin sulfate proteoglycans (CSPGs) and tenascins, which are organized into unique structures called perineuronal nets (PNNs). PNNs associate with the neuronal cell body and proximal dendrites of predominantly parvalbumin-positive interneurons, forming a robust lattice-like structure. These developmentally regulated structures are maintained in the adult CNS and enhance synaptic stability. After injury, however, CSPGs and tenascins contribute to the structure of the inhibitory glial scar, which actively prevents axonal regeneration. Myelin sheaths and mature adult oligodendrocytes, despite their important role in signal conduction in mature CNS axons, contribute to the inhibitory environment existing after injury. As such, unlike the peripheral nervous system, the CNS is unable to revert to a “developmental state” to aid neuronal repair. Modulation of these external factors, however, has been shown to promote growth, regeneration, and functional plasticity after injury. This review will highlight some of the factors that contribute to or prevent plasticity, sprouting, and axonal regeneration after spinal cord injury.Publisher PDFPeer reviewe

Grafted Human iPSC-Derived Neural Progenitor Cells Express Integrins and Extend Long-Distance Axons Within the Developing Corticospinal Tract

After spinal cord injury (SCI), regeneration of adult motor axons such as axons in the corticospinal tract (CST) is severely limited. Alongside the inhibitory lesion environment, most neuronal subtypes in the mature central nervous system (CNS) are intrinsically unrepairable. With age, expression of growth-promoting proteins in neurons, such as integrins, declines. Integrin receptors allow communication between the extracellular matrix (ECM) and cell cytoskeleton and their expression in axons facilitates growth and guidance throughout the ECM. The α9β1 integrin heterodimer binds to tenascin-C (TN-C), an ECM glycoprotein expressed during development and after injury. In the mature CST however, expression of the α9 integrin subunit is downregulated, adding to the intrinsic inability of axons to regenerate. Our previous work has shown the α9 integrin subunit is not trafficked within axons of mature CST or rubrospinal tracts (RSTs). Thus, here we have utilized human induced pluripotent stem cell (iPSC)-derived neural progenitor cells (NPCs) to increase expression of α9 integrinwithin the developing rat CST. We demonstrate that human NPCs (hNPCs) express endogenous levels of both α9 and β1 integrin subunits as well as cortical neuron markers such as chicken ovalbumin upstream promoter transcription factor (COUP-TF) interacting protein 2 (Ctip2) and T-box brain 1 (Tbr1). In addition, lentivirus-mediated α9 integrin overexpression in hNPCs resulted in increased neurite outgrowth in the presence of TN-C in vitro. Following transplantation into the sensorimotor cortex of newborn rats, both wild type (WT) and α9-expressing hNPCs extend along the endogenous CST and retain expression of α9 throughout the length of the axonal compartment for up to 8 weeks following transplantation. These data highlight the growth potential of transplanted human iPSCs which may be a future target for regenerative therapies after nervous system injury