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Κυριακή 23 Οκτωβρίου 2022

Expression of Glial Cell‐Derived Neurotrophic Factor Receptors Within Nucleus Ambiguus During Rat Development

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Expression of Glial Cell-Derived Neurotrophic Factor Receptors Within Nucleus Ambiguus During Rat Development

In this paper, we show differences of Glial Cell-Derived Neurotrophic Factor (GDNF)receptors in the nucleus ambiguus during development from E14 to E20 and in the rat adulthood. We observed that there is timing of production of the different members of GDNF receptors in the motoneurons innervating the larynx and we try to establish differences between nucleus ambiguus and the other motor nuclei of the medulla oblongata such as facial and hypoglossus nuclei. These findings support the idea that GDNF may play a role during motor innervation of the rat larynx.


Objective

The nucleus ambiguus (NAmb) is a column of neurons in the medulla oblongata, involved in bulbar functions. Expression of Glial Cell-Derived Neurotrophic Factor (GDNF) and its receptors (GDNFR) is observed within the cell bodies during reinnervation following recurrent laryngeal nerve (RLN) injury. Little is known regarding GDNFR expression in the formation of the NAmb and the laryngeal innervation during embryogenesis. Understanding the timing and pattern of GDNFR expression in embryogenesis versus after RLN injury may provide insights into therapeutic targets for regeneration after RLN injury.

Study Design

Laboratory experiment.

Methods

Rat brainstems at E14.5/E16.5/E18.5/E20.5/adult were stained for GDNFR: GFRα-1/GFRα-2/GFRα-3/Ret. Islet1 and choline acetyltransferase were used as cell body markers. Sections were observed using fluorescent microscopy and quantified through manual cell counting.

Results

Expression of GFRα-1, GFRα-3, and Ret was identified within the NAmb, hypoglossal, and facial nuclei of the adult medulla. During development, GFRα-1 immunoreactivity was seen at E20.5. GFRα-2 expression was not observed at any timepoint. GFRα-3 expression began at E16.5. Ret expression within nerve fibers in the NAmb were observed beginning at E14.5, but never in the cell bodies.

Conclusion

Embryonic GDNFR expression in the NAmb differs from that of the adult after RLN injury. The developing brainstem experienced upregulation at discrete timepoints with signaling sustained through adulthood. In contrast, adult RLN-transected rats experienced patterns of up and down regulation. GFRα-1 may contribute to muscle targeting and neuromuscular junction maturation, GFRα-3 may contribute to both, as well as axon guidance. It is likely that GDNF is functioning via a Ret-independent pathway.

Level of Evidence

NA Laryngoscope, 2022

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A minimally invasive method for titanium mesh fixation with resorbable sutures in guided bone regeneration: A retrospective study

alexandrossfakianakis shared this article with you from Inoreader

Abstract

Objectives

Titanium mesh has become a mainstream choice for guided bone regeneration (GBR) owing to its excellent space maintenance. However, the traditional fixation method using titanium screws impacts surgery efficiency and increases patient trauma. We report a novel method of fixing a titanium mesh using resorbable sutures. We assessed the feasibility of resorbable sutures for fixing a titanium mesh and whether it can serve as a stable, universal, and minimally invasive fixation method for a broader application of titanium meshes.

Methods

Patients undergoing GBR with a digital titanium mesh fixed using titanium screws (TS group) and resorbable sutures (RS group) were observed at different time points. The stability of the fixation methods was evaluated on parameters such as titanium mesh spatial displacement, bone augmentation, and bone resorption.

Results

A total of 36 patients were included in this study. The exposure rate of the titanium mesh in the TS group was 16.67%, while no exposure was noted in the RS group. There was no significant difference in the parameters of titanium mesh spatial displacement, bone augmentation, and bone resorption between the two groups (p > 0.05).

Conclusion

The use of resorbable sutures for fixing a titanium mesh can achieve similar results to traditional fixation using titanium screws. Although this new fixation method can improve the efficiency of the surgery and reduce the risk of complications, the long-term clinical effects require further follow-up investigation.

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Epigenetic upregulation of Schlafen11 renders WNT- and SHH- activated medulloblastomas sensitive to cisplatin

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Abstract
Background
Intensive chemotherapeutic regimens with craniospinal irradiation have greatly improved survival in medulloblastoma patients. However, survival markedly differs among molecular subgroups and their biomarkers are unknown. Through unbiased screening, we found Schlafen family member 11 (SLFN11), which is known to improve response to DNA damaging agents in various cancers, to be one of the top prognostic markers in medulloblastomas. Hence, we explored the expression and functions of SLFN11 in medulloblastoma.
Methods
SLFN11 expression for each subgroup was assessed by immunohistochemistry in 98 medulloblastoma patient samples and by analyzing transcriptomic databases. We genetically or epigenetically modulated SLFN11 expression in medulloblastoma cell lines and determined cytotoxic response to the DNA damaging agents cisplatin and topoisomerase I inhibitor SN-38 in vitro and in vivo.
Results
High SLFN11 expressing cases exhibited significantly longer survival than low expressing cases. SLFN11 was highly expressed in the WNT-activated subgroup and in a proportion of the SHH-activated subgroup. While WNT activation was not a direct cause of the high expression of SLFN11, a specific hypomethylation locus on the SLFN11 promoter was significantly correlated with high SLFN11 expression. Overexpression or deletion of SLFN11 made medulloblastoma cells sensitive and resistant to cisplatin and SN-38, respectively. Pharmacological upregulation of SLFN11 by the brain-penetrant histone deacetylase-inhibitor RG2833 markedly increased sensitivity to cisplatin and SN-38 in SLFN11-negative medulloblastoma cells. Intracranial xenograft studies also showed marked sensitivity to cisplatin by SLFN11-overexpression in medulloblastoma cells.
Conclusio ns
High SLFN11 expression is one factor which renders favorable outcomes in WNT-activated and a subset of SHH-activated medulloblastoma possibly through enhancing response to cisplatin.
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