Growth hormone promotes the reconstruction of injured axons in the hypothalamo-neurohypophyseal system.

JOURNAL/nrgr/04.03/01300535-202410000-00026/figure1/v/2024-02-06T055622Z/r/image-tiff Previous studies have shown that growth hormone can regulate hypothalamic energy metabolism, stress, and hormone release. Therefore, growth hormone has great potential for treating hypothalamic injury. In this study, we established a specific hypothalamic axon injury model by inducing hypothalamic pituitary stalk electric lesions in male mice. We then treated mice by intraperitoneal administration of growth hormone. Our results showed that growth hormone increased the expression of insulin-like growth factor 1 and its receptors, and promoted the survival of hypothalamic neurons, axonal regeneration, and vascular reconstruction from the median eminence through the posterior pituitary. Altogether, this alleviated hypothalamic injury-caused central diabetes insipidus and anxiety. These results suggest that growth hormone can promote axonal reconstruction after hypothalamic injury by regulating the growth hormone-insulin-like growth factor 1 axis.

A procedure in mice to obtain intact pituitary-infundibulum-hypothalamus preparations: a method to evaluate the reconstruction of hypothalamohypophyseal system.

PURPOSE: The histopathological study of brain tissue is a common method in neuroscience. However, efficient procedures to preserve the intact hypothalamic-pituitary brain specimens are not available in mice for histopathological study. METHOD: We describe a detailed procedure for obtaining mouse brain with pituitary-hypothalamus continuity. Unlike the traditional methods, we collect the brain via a ventral approach. We cut the intraoccipital synchondrosis, transection the endocranium of pituitary, broke the spheno-occipital synchondrosis, expose the posterior edge of pituitary, separate the trigeminal nerve, then the intact pituitary gland was preserved. RESULT: We report an more effective and practical method to obtain continuous hypothalamus -pituitary preparations based on the preserve of leptomeninges. COMPARED WITH THE EXISTING METHODS: Our procedure effectively protects the integrity of the fragile infundibulum preventing the pituitary from separating from the hypothalamus. This procedure is more convenient and efficient. CONCLUSION: We present a convenient and practical procedure to obtain intact hypothalamic-pituitary brain specimens for subsequent histopathological evaluation in mice.

Adult neurogenesis of the median eminence contributes to structural reconstruction and recovery of body fluid metabolism in hypothalamic self-repair after pituitary stalk lesion.

Body fluid homeostasis is critical to survival. The integrity of the hypothalamo-neurohypophysial system (HNS) is an important basis of the precise regulation of body fluid metabolism and arginine vasopressin (AVP) hormone release. Clinically, some patients with central diabetes insipidus (CDI) due to HNS lesions can experience recovery compensation of body fluid metabolism. However, whether the hypothalamus has the potential for structural plasticity and self-repair under pathological conditions remains unclear. Here, we report the repair and reconstruction of a new neurohypophysis-like structure in the hypothalamic median eminence (ME) after pituitary stalk electrical lesion (PEL). We show that activated and proliferating adult neural progenitor cells differentiate into new mature neurons, which then integrate with remodeled AVP fibers to reconstruct the local AVP hormone release neural circuit in the ME after PEL. We found that the transcription factor of NK2 homeobox 1 (NKX2.1) and the sonic hedgehog signaling pathway, mediated by NKX2.1, are the key regulators of adult hypothalamic neurogenesis. Taken together, our study provides evidence that adult ME neurogenesis is involved in the structural reconstruction of the AVP release circuit and eventually restores body fluid metabolic homeostasis during hypothalamic self-repair.

An Efficient Method for the Isolation and Cultivation of Hypothalamic Neural Stem/Progenitor Cells From Mouse Embryos.

The hypothalamus is the key region that regulates the neuroendocrine system as well as instinct behaviors, and hypothalamic dysfunction causes refractory clinical problems. Recent studies have indicated that neural stem/progenitor cell (NSPC) in the hypothalamus play a crucial role in hypothalamic function. However, specific hypothalamic NSPC culture methods have not been established, especially not detailed or efficient surgical procedures. The present study presented a convenient, detailed and efficient method for the isolation and cultivation of hypothalamic NSPCs from embryonic day 12.5 mice. The procedure includes embryo acquisition, brain microdissection to quickly obtain hypothalamic tissue and hypothalamic NSPC culture. Hypothalamic NSPCs can be quickly harvested and grow well in both neurosphere and adherent cultures through this method. Additionally, we confirmed the cell origin and evaluated the proliferation and differentiation properties of cultured cells. In conclusion, we present a convenient and practical method for the isolation and cultivation of hypothalamic NSPCs that can be used in extensive hypothalamic studies.

Transcriptomic Analysis Reveals that Activating Transcription Factor 3/c-Jun/Lgals3 Axis Is Associated with Central Diabetes Insipidus after Hypothalamic Injury.

BACKGROUND: Hypothalamic injury causes several complicated neuroendocrine-associated disorders, such as water-electrolyte imbalance, obesity, and hypopituitarism. Among these, central diabetes insipidus (CDI), characterized by polyuria, polydipsia, low urine specific gravity, and deficiency of arginine vasopressin contents, is a typical complication after hypothalamic injury. METHODS: CDI was induced by hypothalamic pituitary stalk injury in male animals. Behavioral parameters and blood sample were collected to evaluate the characteristics of body fluid metabolism imbalance. The brains were harvested for high-throughput RNA sequencing and immunostaining to identify pathophysiological changes in corresponding hypothalamic nuclei. RESULTS: Based on transcriptomic analysis, we demonstrated the upregulation of the activating transcription factor 3 (Atf3)/c-Jun axis and identified Lgals3, a microglial activation-related gene, as the most significant target gene in response to the body fluid imbalance in CDI. Furthermore, we found that the microglia possessed elevated phagocytic ability, which could promote the elimination of arginine vasopressin neurons after hypothalamic injury. CONCLUSION: Our findings suggested that the Atf3/c-Jun/Lgals3 axis was associated with the microglial activation, and might participate in the loss of functional arginine vasopressin neurons in CDI after hypothalamic injury.

NPY alterations induced by chronic morphine exposure affect the maintenance and reinstatement of morphine conditioned place preference.

Opioid addiction is a brain disease that severely harms society and personal health. Although the tremendous numbers of patients worldwide and emerged negative events, effective treatments for opioid addiction are still lacking. Neuropeptide Y (NPY) is one of the main orexigenic peptides that play vital roles in food intake and energy metabolism. However, increasing evidence indicates that NPY may have great potential in mediating reward effects and drug dependence. In the present study, we assessed the expression changes of NPY in the nucleus accumbens at different timepoints following morphine conditioned place preference (CPP) and investigated the functional importance of potential NPY changes. Our results showed that NPY expression significantly decreased in the nucleus accumbens shell (AcbSh) immediately after chronic morphine exposure. Subsequently, it increased rapidly at first and then gradually returned to normal levels. Further data indicated that these NPY changes were involved in morphine reward memory, demonstrated by a reduction in the extinction period after blocking of the Y5 receptor by L-152,804 in the AcbSh and a prolonged duration of the extinction period following the application of NPY. More importantly, the additional results revealed that L-152,804 also remarkably suppressed the reinstatement of morphine CPP. Together, our results indicate that a complicated plasticity of the NPY pathway in AcbSh occurs following morphine CPP, and this plasticity plays an important role in modulating morphine reward memory. These findings may enhance our understanding of the role of the NPY system in opioid addiction and indicate a promising target for opioid addiction treatment.

A retaining sphenoid and dura procedure in the rat to obtain intact pituitary-infundibulum-hypothalamus preparations.

BACKGROUND: The histopathological study of brain tissue is a conventional method in neuroscience. However, procedures specifically developed to recover intact hypothalamic-pituitary brain specimens, are not available. NEW METHOD: We describe a detailed protocol for obtaining intact rat brain with pituitary-hypothalamus continuity through an intact infundibulum. The brain is collected via a ventral approach through removing the skull base. Membranous structures surrounding the hypothalamus-pituitary system can be preserved, including vasculature. RESULTS: We report a retaining sphenoid and dura technique to obtain intact hypothalamic-pituitary brain preparations, and we confirm the practicability of this method. By combination of this technique with histological analysis or 3D brain tissue clearing and imaging methods, the functional morphology structure of the hypothalamus-pituitary can be further explored. COMPARISON WITH EXISTING METHOD: The current procedure is limited in showing the connection between the hypothalamus and the pituitary. Our procedure effectively protects the integrity of the fragile infundibulum and thus prevents the pituitary from separating from the hypothalamus. CONCLUSIONS: We present a convenient and practical approach to obtain intact hypothalamus-pituitary brain specimens for subsequent histopathological evaluation.

The combination of two-dimensional and three-dimensional analysis methods contributes to the understanding of glioblastoma spatial heterogeneity.

Heterogeneity is regarded as the major factor leading to the poor outcomes of glioblastoma (GBM) patients. However, conventional two-dimensional (2D) analysis methods, such as immunohistochemistry and immunofluorescence, have limited capacity to reveal GBM spatial heterogeneity. Thus, we sought to develop an effective analysis strategy to increase the understanding of GBM spatial heterogeneity. Here, 2D and three-dimensional (3D) analysis methods were compared for the examination of cell morphology, cell distribution and large intact structures, and both types of methods were employed to dissect GBM spatial heterogeneity. The results showed that 2D assays showed only cross-sections of specimens but provided a full view. To visualize intact GBM specimens in 3D without sectioning, the optical tissue clearing methods CUBIC and iDISCO+ were used to clear opaque specimens so that they would become more transparent, after which the specimens were imaged with a two-photon microscope. The 3D analysis methods showed specimens at a large spatial scale at cell-level resolution and had overwhelming advantages in comparison to the 2D methods. Furthermore, in 3D, heterogeneity in terms of cell stemness, the microvasculature, and immune cell infiltration within GBM was comprehensively observed and analysed. Overall, we propose that 2D and 3D analysis methods should be combined to provide much greater detail to increase the understanding of GBM spatial heterogeneity.

[JNK/c-Jun signaling pathway mediates arginine vasopressin neuron regeneration by promoting cytoskeleton reconstruction in rats with electrical lesions of the pituitary stalk].

OBJECTIVE: To investigate the mechanism by which doublecortin promotes the recovery of cytoskeleton in arginine vasopressin (AVP) neurons in rats with electrical lesions of the pituitary stalk (PEL). METHODS: Thirty-two SD rats were randomized into PEL group with electrical lesions of the pituitary stalk through the floor of the skull base (n=25) and sham operation group (n=7), and the daily water consumption (DWC), daily urine volume (DUV) and urine specific gravity (USG) of the rats were recorded. Four rats on day 1 and 7 rats on each of days 3, 7 and 14 after PEL as well as the sham-operated rats were sacrificed for detection of the expressions of ß-Tubulin (Tuj1), doublecortin and caspase- 3 in the AVP neurons of the supraoptic nucleus using immunofluorescence assay and Western blotting. RESULTS: After PEL, the rats exhibited a typical triphasic pattern of diabetes insipidus, with the postoperative days 1-2 as the phase one, days 3-5 as the phase two, and days 6-14 as the phase three. Immunofluorescent results indicated the repair of the AVP neurons evidenced by significantly increased doublecortin expressions in the AVP neurons following PEL; similarly, the expression of Tuj1 also increased progressively after PEL, reaching the peak level on day 7 after PEL. The apoptotic rates of the AVP neurons exhibited a reverse pattern of variation, peaking on postoperative day 3 followed by progressive reduction till day 14. Western blotting showed that the expressions of c-Jun and p-c-Jun were up-regulated significantly on day 3 (P < 0.05) and 7 (P < 0.01) after PEL, while an upregulated p-JNK expression was detected only on day 3 (P < 0.05), as was consistent with the time-courses of neuronal recovery and apoptosis after PEL. CONCLUSIONS: JNK/c-Jun pathway is activated after PEL to induce apoptosis of AVP neurons in the acute phase and to promote the repair of neuronal cytoskeleton by up-regulation of doublecortin and Tuj1 expressions.

Endoplasmic reticulum stress induces apoptosis of arginine vasopressin neurons in central diabetes insipidus via PI3K/Akt pathway.

AIMS: Central diabetes insipidus (CDI), a typical complication caused by pituitary stalk injury, often occurs after surgery, trauma, or tumor compression around hypothalamic structures such as the pituitary stalk and optic chiasma. CDI is linked to decreased arginine vasopressin (AVP) neurons in the hypothalamic supraoptic nucleus and paraventricular nucleus, along with a deficit in circulating AVP and oxytocin. However, little has been elucidated about the changes in AVP neurons in CDI. Hence, our study was designed to understand the role of several pathophysiologic changes such as endoplasmic reticulum (ER) stress and apoptosis of AVP neurons in CDI. METHODS: In a novel pituitary stalk electric lesion (PEL) model to mimic CDI, immunofluorescence and immunoblotting were used to understand the underlying regulatory mechanisms. RESULTS: We reported that in CDI condition, generated by PEL, ER stress induced apoptosis of AVP neurons via activation of the PI3K/Akt and ERK pathways. Furthermore, application of N-acetylcysteine protected hypothalamic AVP neurons from ER stress-induced apoptosis through blocking the PI3K/Akt and ERK pathways. CONCLUSION: Our findings showed that AVP neurons underwent apoptosis induced by ER stress, and ER stress might play a vital role in CDI condition through the PI3K/Akt and ERK pathways.

A rat model for pituitary stalk electric lesion-induced central diabetes insipidus: application of 3D printing and further outcome assessments.

A stable and reproducible rat injury model is not currently available to study central diabetes insipidus (CDI) and the neurohypophyseal system. In addition, a system is needed to assess the severity of CDI and measure the accompanying neurobiological alterations. In the present study, a 3D-printed lesion knife with a curved head was designed to fit into the stereotaxic instrument. The neuro-anatomical features of the brain injury were determined by in vivo magnetic resonance imaging (MRI) and arginine vasopressin (AVP) immunostaining on brain sections. Rats that underwent pituitary stalk electrical lesion (PEL) exhibited a tri-phasic pattern of CDI. MRI revealed that the hyperintenseT1-weighted signal of the pituitary stalk was interrupted, and the brain sections showed an enlarged end proximal to the injury site after PEL. In addition, the number of AVP-positive cells in supraoptic nucleus (SON) and paraventricular nucleus (PVN) decreased after PEL, which confirmed the success of the CDI model. Unlike hand-made tools, the 3D-printed lesion knives were stable and reproducible. Next, we used an ordinal clustering method for staging and the k-means' clustering method to construct a CDI index to evaluate the severity and recovery of CDI that could be used in other multiple animals, even in clinical research. In conclusion, we established a standard PEL model with a 3D-printed knife tool and proposed a CDI index that will greatly facilitate further research on CDI.

Functional ectopic neural lobe increases GAP-43 expression via PI3K/AKT pathways to alleviate central diabetes insipidus after pituitary stalk lesion in rats.

Central diabetes insipidus can occur after hypothalamic-hypophyseal tract injury. This injury is linked with a deficit in circulating vasopressin and oxytocin, which are produced in the supraoptic nuclei and the hypothalamic paraventricular nuclei. Previous studies indicate that an ectopic neural lobe forms after pituitary stalk lesion in rats, and while the relationship between an ectopic neural lobe and CDI outcomes is unclear, the underlying mechanisms are also unknown. Here, we report that two different CDI characteristics are shown in rats that underwent pituitary stalk electric lesion and are defined by two different groups classified as the recovery group and the no-recovery group. Rats showed an enlarged functional ectopic neural lobe at the lesion site with a low CDI index. Moreover, growth associated protein-43, p-PI3K and p-AKT were up-regulated in the unmyelinated fibers of the ectopic neural lobe. Our findings suggest that the enlarged structure formed a functional ectopic neural lobe after the pituitary stalk lesion, and its regeneration might influence the CDI outcome. This regeneration might be due to an increase in GAP-43 expression through the PI3K/AKT pathway.