A Novel in vitro Model Delineating Hair Cell Regeneration and Neural Reinnervation in Adult Mouse Cochlea

The study of an adult mammalian auditory system, such as regeneration, has been hampered by the lack of an in vitro system in which hypotheses can be tested efficiently. This is primarily due to the fact that the adult inner ear is encased in the toughest bone of the body, whereas its removal leads to the death of the sensory epithelium in culture. We hypothesized that we could take advantage of the integral cochlear structure to maintain the overall inner ear architecture and improve sensory epithelium survival in culture. We showed that by culturing adult mouse cochlea with the (surrounding) bone intact, the supporting cells (SCs) survived and almost all hair cells (HCs) degenerated. To evaluate the utility of the explant culture system, we demonstrated that the overexpression of Atoh1, an HC fate-determining factor, is sufficient to induce transdifferentiation of adult SCs to HC-like cells (HCLCs). Transdifferentiation-derived HCLCs resemble developmentally young HCs and are able to attract adult ganglion neurites. Furthermore, using a damage model, we showed that degenerated adult ganglions respond to regenerated HCLCs by directional neurite outgrowth that leads to HCLC-neuron contacts, strongly supporting the intrinsic properties of the HCLCs in establishing HCLC-neuron connections. The adult whole cochlear explant culture is suitable for diverse studies of the adult inner ear including regeneration, HC-neuron pathways, and inner ear drug screening.

Development of An Efficient Protocol for Rapid Propagation of Curculigo orchioides Using Leaf Explant Culture

Curculigo orchioides is one of the most common medicinal plants used by diverse cultures and tribal groups. The roots of the plant are used medicinally in Asian countries. Curculigo orchioides have the ability to regenerate through seeds and tubers, but the regeneration rate is low. Plant tissue culture method was believed to have potential for rapid multiplication of this medicinal plant. An efficient protocol for rapid propagation of Curculigo orchioides, of the family Amaryllidaceae, was developed using leaf explants culture. The leaf explants (1 cm x 1 cm squares) cultured on Murashige and Skoog (MS) basal medium were supplemented with various concentrations and combinations of auxins and cytokinins with temperature 25 ± 2°C, relative humidity 85-90% and photoperiod of 12 hours light (2000-3000 lux). Callus induction was obtained within 4 weeks, 2,4-D at 3 mg/l formed profuse callus and the degree was found to be the highest (+++) among all the treatments. The best response to shoot induction, with maximum shoot number 5.33 (mean number of shoots per explant) was obtained using 1.0 mg/l 6-benzyl aminopurine (BAP) in combination with 1.0 mg/l Kinetin. In vitro shoots were induced for rooting on 0.5 mg/l of NAA supplemented medium. In order for seedlings propagated in vitro to adapt to natural conditions, plants were growned on a substrate coir: husk ash: sand (with the ratio of 0.5: 0.5: 1) in a greenhouse (humidity: 70%, temperature: 28-300C) gave 88.33% survival rate after 8 weeks of culture. With the results received, this is an effective approach to propagating Curculigo orchioides.

An improved organ explant culture method reveals stem cell lineage dynamics in the adult Drosophila intestine

In recent years, live-imaging techniques have been developed for the adult midgut of Drosophila melanogaster that allow temporal characterization of key processes involved in stem cell and tissue homeostasis. However, current organ culture techniques are limited to imaging sessions of <16 hours, an interval too short to track dynamic processes such as damage responses and regeneration, which can unfold over several days. Therefore, we developed a new organ explant culture protocol capable of sustaining midguts ex vivo for up to 3 days. This was made possible by the formulation of a culture medium specifically designed for adult Drosophila tissues with an increased Na+/K+ ratio and trehalose concentration, and by placing midguts at an air-liquid interface for enhanced oxygenation. We show that midgut progenitor cells can respond to gut epithelium damage ex vivo, proliferating and differentiating to replace lost cells, but are quiescent in healthy intestines. Using ex vivo gene induction to promote stem cell proliferation, we demonstrate that intestinal stem lineages can be traced through multiple cell divisions using live imaging. Both asymmetric and symmetric divisions can be identified in the reconstructed lineages. We find that daughter cells of asymmetric divisions remain in close proximity of each other, while the progeny of symmetric divisions actively move apart, with implications for cell differentiation and tissue organization. We show that the same culture set-up is useful for imaging adult renal tubules and ovaries for up to 72 hours. By enabling both long-term imaging and real-time ex vivo gene manipulation, our simple culture protocol provides a powerful tool for studies of epithelial biology and cell lineage behavior.

Growth kinetics and phenotypic markers expression in human dermal stem cells

Human dermal stem cells (DSCs) have generated significant interest in the field of regenerative medicine due to their prospects of autologous transplantation. The present study evaluated the growth kinetics and phenotypic markers expression in human DSCs. The primary cultures of DSCs (n=3) were established by explant culture and characterization of the cells was carried out by assessing morphology, viability, proliferation rate, population doubling time (PDT), cell cycle status and the expression of cell surface markers such as CD29, CD73, CD90 and CD166. The cells released from tissue explants showed spindleshaped fibroblast morphology with the mean percentage viability varying between 93.43% and 100% from passages 1 to 4. DSCs displayed a strong and steady proliferative potential with an average PDT of 42.55 hrs. Cell cycle profile of DSCs demonstrated the majority of cells (59.80% to 76.29%) at G0/G1 phase. Further, the phenotypic profile of markers confirmed the stromal origin of DSCs by exhibiting positivity for CD29, CD73, CD90 and CD166. In conclusion, the growth kinetics and expression of phenotypic markers are consistent with the notion that skin dermis contains a population of stem cells and can serve as a potential autologous source for therapeutic applications.

Reduction of acetylcholine in the hippocampus of hippocampal cholinergic neurostimulating peptide precursor protein knockout mice

The cholinergic efferent network from the medial septal nucleus to the hippocampus plays an important role in learning and memory processes. This cholinergic projection can generate theta oscillations in the hippocampus to encode novel information. Hippocampal cholinergic neurostimulating peptide (HCNP), which induces acetylcholine (Ach) synthesis in the medial septal nuclei of an explant culture system, was purified from the soluble fraction of postnatal rat hippocampus. HCNP is processed from the N-terminal region of a 186-amino acid, 21-kDa HCNP precursor protein, also known as Raf kinase inhibitory protein and phosphatidylethanolamine-binding protein 1. Here, we confirmed direct reduction of Ach release in the hippocampus of freely moving HCNP-pp knockout mice under an arousal state by the microdialysis method. The levels of vesicular acetylcholine transporter were also decreased in the hippocampus of these mice in comparison with those in control mice, suggesting there was decreased incorporation of Ach into the synaptic vesicle. These results potently indicate that HCNP may be a cholinergic regulator in the septo-hippocampal network.

TUB and ZNF532 Promote the Atoh1-Mediated Hair Cell Regeneration in Mouse Cochleae

Hair cell (HC) regeneration is a promising therapy for permanent sensorineural hearing loss caused by HC loss in mammals. Atoh1 has been shown to convert supporting cells (SCs) to HCs in neonatal cochleae; its combinations with other factors can improve the efficiency of HC regeneration. To identify additional transcription factors for efficient Atoh1-mediated HC regeneration, here we optimized the electroporation procedure for explant culture of neonatal mouse organs of Corti and tested multiple transcription factors, Six2, Ikzf2, Lbh, Arid3b, Hmg20 a, Tub, Sall1, and Znf532, for their potential to promote Atoh1-mediated conversion of SCs to HCs. These transcription factors are expressed highly in HCs but differentially compared to the converted HCs based on previous studies, and are also potential co-reprograming factors for Atoh1-mediated SC-to-HC conversion by literature review. P0.5 cochlear explants were electroporated with these transcription factors alone or jointly with Atoh1. We found that Sox2+ progenitors concentrated within the lateral greater epithelial ridge (GER) can be electroporated efficiently with minimal HC damage. Atoh1 ectopic expression promoted HC regeneration in Sox2+ lateral GER cells. Transcription factors Tub and Znf532, but not the other six tested, promoted the HC regeneration mediated by Atoh1, consistent with previous studies that Isl1 promotes Atoh1-mediated HC conversionex vivo and in vivo and that both Tub and Znf532 are downstream targets of Isl1. Thus, our studies revealed an optimized electroporation method that can transfect the Sox2+ lateral GER cells efficiently with minimal damage to the endogenous HCs. Our results also demonstrate the importance of the Isl1/Tub/Znf532 pathway in promoting Atoh1-mediated HC regeneration.

A Novel Method of Mouse RPE Explant Culture and Effective Introduction of Transgenes Using Adenoviral Transduction for In Vitro Studies in AMD

Degeneration of retinal pigment epithelium (RPE) is one of the most critical phenotypic changes of age-related macular degeneration (AMD), the leading cause of vision loss in the elderly. While cultured polarized RPE cells with original properties are valuable in in vitro models to study RPE biology and the consequences of genetic and/or pharmacological manipulations, the procedure to establish mouse primary PRE cell culture or pluripotent stem cell-derived RPE cells is time-consuming and yields a limited number of cells. Thus, establishing a mouse in situ RPE culture system is highly desirable. Here we describe a novel and efficient method for RPE explant culture that allows for obtaining biologically relevant RPE cells in situ. These RPE explants (herein referred to as RPE flatmounts) are viable in culture for at least 7 days, can be efficiently transduced with adenoviral constructs, and/or treated with a variety of drugs/chemicals followed by downstream analysis of the signaling pathways/biological processes of interest, such as assessment of the autophagy flux, inflammatory response, and receptor tyrosine kinases stimulation. This method of RPE explant culture is highly beneficial for pharmacological and mechanistic studies in the field of RPE biology and AMD research.

Role of FBXW2 in explant cultures of bovine periosteum-derived cells

Objective Bone regeneration is a potential technique for treating osteoporosis. A previous study reported that F-box and WD-40 domain-containing protein 2 (FBXW2) localized with osteocalcin in bovine periosteum after 5 weeks of explant culture. However, the osteoblastic functions of FBXW2 remain unclear. In this study, double-fluorescent immunostaining was used to investigate the potential role of FBXW2 and its relationship with osteocalcin. Results At day 0, FBXW2 was expressed in the cambium layer between the bone and periosteum, while osteocalcin was expressed in bone. After explant culture, changes in the periosteum were observed from weeks 1 to 7. At week 1, partial FBXW2 expression was seen with a small amount of osteocalcin. At week 2, a layer of FBXW2 was observed. From weeks 3 to 7, tube-like structures of FBXW and osteocalcin were observed, and periosteum-derived cells were released from the periosteum in areas where no FBXW2 was observed. Bovine periosteum-derived cells can form a three-dimensional cell pellet, because multilayered cell sheets are formed inside of the periosteum in vitro. It is shown that in results FBXW2 is produced in periosteal explants near sites where initial osteogenic activity is observed, suggesting that it may be involved in periosteal osteogenesis.