SDF1/CXCR4 contributes to neural regeneration in hemiplegic mice with a monkey ES-cell-derived neural graft

Interaction between SDF1 and CXCR4 Promotes Photoreceptor Differentiation via Upregulation of NFκB Pathway Signaling Activity in Pax6 Gene-Transfected Photoreceptor Precursors

BACKGROUND

CCL2 (also known as monocyte chemoattractant protein 1) and CX3CR1 (also known as Fractalkine receptor)-deficient mice have damaged photoreceptors.

OBJECTIVES

We examined the interaction of SDF1 and CXCR4 on the differentiation of retinal progenitors into rhodopsin-positive photoreceptors.

METHODS

Cloned retinal progenitors were obtained by Pax6 gene transfection of mouse iPS cells followed by serial dilution. Clones were selected by expression of nestin, Musashi1, Six3, and Chx10 mRNA. Cell surface protein expression was analyzed by flow cytometry. The levels of mRNA and intracellular protein were examined by real-time PCR and immunochemistry, respectively. Transient transfection experiments of retinal progenitors were conducted using a human rhodopsin promoter luciferase plasmid.

RESULTS

We selected 10 clones that expressed Six3, Chx10, Crx, Rx1, Nrl, CD73, and rhodopsin mRNA, which, except for rhodopsin, are photoreceptor precursor markers. Clones expressed both CD73 and CXCR4 on the cell surface and differentiated into rhodopsin-positive photoreceptors, which was reinforced by the addition of exogenous SDF1. A CXCR4 inhibitor AMD3100 blocked SDF1-mediated differentiation of progenitors into photoreceptors. SDF1 enhanced human rhodopsin promoter transcription activity, possibly via the NFκB pathway. Addition of SDF1 to the cell culture induced nuclear translocation of NFκB on retinal progenitor cell clones. Neonatal and newborn mouse retinas expressed SDF1 and CXCR4. Cells in the outer nuclear layer where photoreceptors are located expressed CXCR4 at P14 and P56. Cells in the inner nuclear layer expressed SDF1.

CONCLUSIONS

These findings suggest that retinal progenitor cell differentiation was at least partly regulated by SDF1 and CXCR4 via upregulation of NFκB activity.

Neuronal Cell Sheets of Cortical Motor Neuron Phenotype Derived from Human iPSCs

Transplantation of stem cells that differentiate into more mature neural cells brings about functional improvement in preclinical studies of stroke. Previous transplant approaches in the diseased brain utilized injection of the cells in a cell suspension. In addition, neural stem cells were preferentially used for grafting. However, these cells had no specific relationship to the damaged tissue of stroke and brain injury patients. The injection of cells in a suspension destroyed the cell–cell interactions that are suggested to be important for promoting functional integrity of cortical motor neurons. In order to obtain suitable cell types for grafting in patients with stroke and brain damage, a protocol was modified for differentiating human induced pluripotent stem cells from cells phenotypically related to cortical motor neurons. Moreover, cell sheet technology was applied to neural cell transplantation, as maintaining the cell–cell communications is regarded important for the repair of host brain architecture. Accordingly, neuronal cell sheets that were positive Forebrain Embryonic Zinc Finger (Fez) family zinc finger 2 (FEZF2), COUP-TF-interacting protein 2, insulin-like growth factor–binding protein 4 (IGFBP4), cysteine-rich motor neuron 1 protein precursor (CRIM1), and forkhead box p2 (FOXP2) were developed. These markers are associated with cortical motoneurons that are appropriate for the transplant location in the lesions. The sheets allowed preservation of cell–cell interactions shown by synapsin1 staining after transplantation to damaged mouse brains. The sheet transplantation brought about partial structural restoration and the improvement of motor functions in hemiplegic mice. Collectively, the novel neuronal cell sheets were transplanted into damaged motor cortices; the cell sheets maintained cell–cell interactions and improved the motor functions in the hemiplegic model mice. The motoneuron cell sheets are possibly applicable for stroke patients and patients with brain damage by using patient-specific induced pluripotent stem cells.

Matrix metalloproteinase 9 (MMP-9) mediated release of MMP-9 resistant stromal cell-derived factor 1α (SDF-1α) from surface modified polymer films

Preparation of smart materials by coatings of established surfaces with biomolecules will lead to the next generation of functionalized biomaterials. Rejection of implants is still a major problem in medical applications but masking the implant material with protein coatings is a promising approach. These layers not only disguise the material but also equip it with a certain biological function. The anti-inflammatory chemokine stromal cell-derived factor 1α (SDF-1α) is well suited to take over this function, because it efficiently attracts stem cells and promotes their differentiation and proliferation. At least the initial stem cell homing requires the formation of a concentration gradient. Thus, a reliable and robust release mechanism of SDF-1α from the material is essential. Several proteases, most notably matrix metalloproteinases, are upregulated during inflammation, which, in principle, can be exploited for a tightly controlled release of SDF-1α. Herein, we present the covalent immobilization of M-[S4V]-SDF-1α on novel biodegradable polymer films, which consist of heterobifunctional poly(ethylene glycol) and oligolactide-based functionalized macromers. A peptidic linker with a trimeric matrix metalloproteinase 9 (MMP-9) cleavage site (MCS) was used as connection and the linkage between the three components was achieved by combination of expressed protein ligation and Cu(I) catalyzed azide/alkyne cycloaddition. The MCS was used for MMP-9 mediated release of M-[S4V]-SDF-1α from the biomaterial and the released SDF-1α derivative was biologically active and induced strong cell migration, which demonstrates the great potential of this system.

Role of SDF1/CXCR4 interaction in experimental hemiplegic models with neural cell transplantation

Much attention has been focused on neural cell transplantation because of its promising clinical applications. We have reported that embryonic stem (ES) cell derived neural stem/progenitor cell transplantation significantly improved motor functions in a hemiplegic mouse model. It is important to understand the molecular mechanisms governing neural regeneration of the damaged motor cortex after the transplantation. Recent investigations disclosed that chemokines participated in the regulation of migration and maturation of neural cell grafts. In this review, we summarize the involvement of inflammatory chemokines including stromal cell derived factor 1 (SDF1) in neural regeneration after ES cell derived neural stem/progenitor cell transplantation in mouse stroke models.