Creatine supports propagation and promotes neuronal differentiation of inner ear progenitor cells

Construction of organ of Corti organoid to study the effects of berberine sulfate on damaged auditory cells

Sensorineural hearing loss (SNHL) is mainly caused by injury or loss of hair cells (HCs) and associated spiral ganglion neurons (SGNs) in the inner ear. At present, there is still no effective treatment for SNHL in clinic. Recently, advances in organoid bring a promising prospect for research and treatment of SNHL. Meanwhile, three-dimensional (3D) printing provides a tremendous opportunity to construct versatile organoids for tissue engineering and regenerative medicine. In this study, gelatin (Gel), sodium alginate (SA), and polyvinyl alcohol (PVA) were used to fabricate biomimetic scaffold through 3D printing. The organ of Corti derived from neonatal mice inner ear was seeded on the PVA/Gel/SA scaffold to construct organ of Corti organoid. Then, the organ of Corti organoid was used to study the potential protective effects of berberine sulfate on neomycin-juried auditory HCs and SGNs. The results showed that the PVA/Gel/SA biomimetic 3D scaffolds had good cytocompatibilities and mechanical properties. The constructed organoid could maintain organ of Corti activity well in vitro. In addition, the injury intervention results showed that berberine sulfate could significantly inhibit neomycin-induced HC and SGN damage. This study suggests that the fabricated organoid is highly biomimetic to the organ of Corti, which may provide an effective model for drug development, cell and gene therapy for SNHL.

Selective Alteration of the Left Arcuate Fasciculus in Two Patients Affected by Creatine Transporter Deficiency

(1) Background: In hereditary creatine transporter deficiency (CTD), there is an absence of creatine in the brain and neurological symptoms are present, including severe language impairment. However, the pathological changes caused by creatine deficiency that generate neuropsychological symptoms have been poorly studied. (2) Aims: To investigate if the language impairment in CTD is underpinned by possible pathological changes. (3) Methods: We used MRI tractography to investigate the trophism of the left arcuate fasciculus, a white matter bundle connecting Wernicke's and Broca's language areas that is specifically relevant for language establishment and maintenance, in two patients (28 and 18 y.o.). (4) Results: The T1 and T2 MRI imaging results were unremarkable, but the left arcuate fasciculus showed a marked decrease in mean fractional anisotropy (FA) compared to healthy controls. In contrast, the FA values in the corticospinal tract were similar to those of healthy controls. Although white matter atrophy has been reported in CTD, this is the first report to show a selective abnormality of the language-relevant arcuate fasciculus, suggesting a possible region-specific impact of creatine deficiency.

Stem Cell-Based Therapeutic Approaches to Restore Sensorineural Hearing Loss in Mammals

The hair cells that reside in the cochlear sensory epithelium are the fundamental sensory structures responsible for understanding the mechanical sound waves evoked in the environment. The intense damage to these sensory structures may result in permanent hearing loss. The present strategies to rehabilitate the hearing function include either hearing aids or cochlear implants that may recover the hearing capability of deaf patients to a limited extent. Therefore, much attention has been paid on developing regenerative therapies to regenerate/replace the lost hair cells to treat the damaged cochlear sensory epithelium. The stem cell therapy is a promising approach to develop the functional hair cells and neuronal cells from endogenous and exogenous stem cell pool to recover hearing loss. In this review, we specifically discuss the potential of different kinds of stem cells that hold the potential to restore sensorineural hearing loss in mammals and comprehensively explain the current therapeutic applications of stem cells in both the human and mouse inner ear to regenerate/replace the lost hair cells and spiral ganglion neurons.

The biological strategies for hearing re-establishment based on the stem/progenitor cells

The cochlea is the essential organ for hearing and includes both auditory sensory hair cells and spiral ganglion neurons. The discovery of inner ear stem cell brings hope to the regeneration of hair cell and spiral ganglion neuron as well as the followed hearing re-establishment. Thus the investigation on characteristics of inner ear stem/progenitor cells and related regulating clue is important to make such regeneration a reality. In addition, attempts have also been made to transplant exogenous stem cells into the inner ear to restore hearing function. In this review, we describe recent advances in the characterization of mammalian inner ear progenitor/stem cells and the mechanisms of regulating their proliferation and differentiation, and summarize studies that have used exogenous stem cells to repair damaged hair cells and neurons in the inner ear.

Long-term delivery of brain-derived neurotrophic factor (BDNF) from nanoporous silica nanoparticles improves the survival of spiral ganglion neurons in vitro

Sensorineural hearing loss (SNHL) can be overcome by electrical stimulation of spiral ganglion neurons (SGNs) via a cochlear implant (CI). Restricted CI performance results from the spatial gap between the SGNs and the electrode, but the efficacy of CI is also limited by the degeneration of SGNs as one consequence of SHNL. In the healthy cochlea, the survival of SGNs is assured by endogenous neurotrophic support. Several applications of exogenous neurotrophic supply have been shown to reduce SGN degeneration in vitro and in vivo. In the present study, nanoporous silica nanoparticles (NPSNPs), with an approximate diameter of <100 nm, were loaded with the brain-derived neurotrophic factor (BDNF) to test their efficacy as long-term delivery system for neurotrophins. The neurotrophic factor was released constantly from the NPSNPs over a release period of 80 days when the surface of the nanoparticles had been modified with amino groups. Cell culture investigations with NIH3T3 fibroblasts attest a good general cytocompatibility of the NPSNPs. In vitro experiments with SGNs indicate a significantly higher survival rate of SGNs in cell cultures that contained BDNF-loaded nanoparticles compared to the control culture with unloaded NPSNPs (p<0.001). Importantly, also the amounts of BDNF released up to a time period of 39 days increased the survival rate of SGNs. Thus, NPSNPs carrying BDNF are suitable for the treatment of inner ear disease and for the protection and the support of SGNs. Their nanoscale nature and the fact that a direct contact of the nanoparticles and the SGNs is not necessary for neuroprotective effects, should allow for the facile preparation of nanocomposites, e.g., with biocompatible polymers, to install coatings on implants for the realization of implant-based growth factor delivery systems.

Differentiation of stem cells derived from carious teeth into dopaminergic-like cells

AIM

To investigate whether dental pulp stem cells from carious teeth (DPSCs-CT) can differentiate into functional dopaminergic-like (DAergic) cells and provide an alternative cell source in regenerative medicine.

METHODOLOGY

Dental pulp stem cells from healthy (DPSCs) and carious teeth (DPSCs-CT) were isolated from young donors. Both cell lines were expanded in identical culture conditions and subsequently differentiated towards DAergic-like cells using pre-defined dopaminergic cocktails. The dopaminergic efficiencies were evaluated both at gene and protein as well as at secretome levels.

RESULTS

The efficiency of DPSCs-CT to differentiate into DAergic-like cells was not equivalent to that of DPSCs. This was further reflected in both gene and protein generation whereby key neuronal markers such as nestin, NURR1 and beta-III-tubulin were expressed significantly lower as compared to differentiated DPSCs (P < 0.05). In addition, expressions of transcriptomes related to neurogenesis revealed downregulation of more than 50% of the genes as compared to differentiated DPSC (P < 0.05). Amongst the notable genes were those from the transcription factors family (FLNA, MEF2C, NEUROG2), signalling pathway family (DLL1, Notch1, TGF-β1), neuro-inducer family (BDNF) and cell communication family (APBB1).

CONCLUSIONS

DPSCs-CT were able to differentiate into DAergic-like cells but not as efficiently as DPSCs. As such, prior to use in regenerative medicine, stem cells from any source should be thoroughly investigated beyond conventional benchmarks such as that proposed by the International Society for Cellular Therapy (ISCT).

Clonal colony formation from spiral ganglion stem cells

Neural stem cells from the central nervous system have the distinct capacity to give rise to clonal neurospheres. These clonal spheres are derived from a single clone-forming cell and represent homogenous, pure cell colonies. Recently, stem/progenitor cells have been isolated from the spiral ganglion of the inner ear using sphere-forming assays. However, the clonality of spiral ganglion-derived spheres has not yet been addressed in detail. Here, we report the isolation of clonal colonies from the spiral ganglion of early postnatal mice. We analyze sphere clonality using coculture experiments with transgenic cells, a semisolid assay, and culture of single cells in isolation. Our data show that sphere clonality differs in primary and secondary cultures and indicate that clonal sphere formation is dependent on specific culture parameters. We also show that the initiation of clonal colony formation does not require cell-to-cell interactions or paracrine signaling from surrounding cells. Generation of clonal colonies from spiral ganglion stem/progenitor cells might be crucial for future clinical applications because pure cell populations are considered to be more efficient and safe for therapeutic use than chimeric, heterogeneous spheres.