Sympathetic reinnervation of unilaterally denervated rat lung

Use of human airway smooth muscle in vitro and ex vivo to investigate drugs for the treatment of chronic obstructive respiratory disorders

Isolated airway smooth muscle has been extensively investigated since 1840 to understand the pharmacology of airway diseases. There has often been poor predictability from murine experiments to drugs evaluated in patients with asthma or chronic obstructive pulmonary disease (COPD). However, the use of isolated human airways represents a sensible strategy to optimise the development of innovative molecules for the treatment of respiratory diseases. This review aims to provide updated evidence on the current uses of isolated human airways in validated in vitro methods to investigate drugs in development for the treatment of chronic obstructive respiratory disorders. This review also provides historical notes on the pioneering pharmacological research on isolated human airway tissues, the key differences between human and animal airways, as well as the pivotal differences between human medium bronchi and small airways. Experiments carried out with isolated human bronchial tissues in vitro and ex vivo replicate many of the main anatomical, pathophysiological, mechanical and immunological characteristics of patients with asthma or COPD. In vitro models of asthma and COPD using isolated human airways can provide information that is directly translatable into humans with obstructive lung diseases. Regardless of the technique used to investigate drugs for the treatment of chronic obstructive respiratory disorders (i.e., isolated organ bath systems, videomicroscopy and wire myography), the most limiting factors to produce high-quality and repeatable data remain closely tied to the manual skills of the researcher conducting experiments and the availability of suitable tissue.

Transection of the cervical sympathetic trunk inhibits the progression of pulmonary arterial hypertension via ERK-1/2 Signalling

Background

Abnormal sympathetic hyperactivity has been shown to lead to pulmonary arterial hypertension (PAH) deterioration. The purpose of this study was to examine whether the transection of the cervical sympathetic trunk (TCST) can inhibit the progression of PAH in a monocrotaline (MCT)-induced PAH model and elucidate the underlying mechanisms.

Methods

Rats were randomly divided into four groups, including a control group, an MCT group, an MCT + sham group and an MCT + TCST group. After performing haemodynamic and echocardiographic measurements, the rats were sacrificed for the histological study, and the norepinephrine (NE) concentrations and protein expression level of tyrosine hydroxylase (TH) were evaluated. The protein expression levels of extracellular signal-regulated kinase (ERK)-1/2, proliferating cell nuclear antigen (PCNA), cyclin A2 and cyclin D1 in pulmonary artery vessels and pulmonary arterial smooth muscle cells (PASMCs) were determined.

Results

Compared with the MCT + sham group, TCST profoundly reduced the mean pulmonary arterial pressure (mPAP) (22.02 ± 4.03 mmHg vs. 31.71 ± 2.94 mmHg), right ventricular systolic pressure (RVSP) (35.21 ± 5.59 mmHg vs. 48.36 ± 5.44 mmHg), medial wall thickness (WT%) (22.48 ± 1.75% vs. 46.10 ± 3.16%), and right ventricular transverse diameter (RVTD) (3.78 ± 0.40 mm vs. 4.36 ± 0.29 mm) and increased the tricuspid annular plane systolic excursion (TAPSE) (2.00 ± 0.12 mm vs. 1.41 ± 0.24 mm) (all P < 0.05). The NE concentrations and protein expression levels of TH were increased in the PAH rats but significantly decreased after TCST. Furthermore, TCST reduced the increased protein expression of PCNA, cyclin A2 and cyclin D1 induced by MCT in vivo. We also found that NE promoted PASMC viability and activated the ERK-1/2 pathway. However, the abovementioned NE-induced changes could be suppressed by the specific ERK-1/2 inhibitor U0126.

Conclusion

TCST can suppress pulmonary artery remodelling and right heart failure in MCT-induced PAH. The main mechanism may be that TCST decreases the NE concentrations in lung tissues, thereby preventing NE from promoting PASMC proliferation mediated by the ERK-1/2 signalling pathway.

Electronic supplementary material

The online version of this article (10.1186/s12931-019-1090-2) contains supplementary material, which is available to authorized users.

Transthoracic Pulmonary Artery Denervation for Pulmonary Arterial Hypertension

Objective—

Pulmonary arterial hypertension is characterized by progressive pulmonary vascular remodeling and persistently elevated mean pulmonary artery pressures and pulmonary vascular resistance. We aimed to investigate whether transthoracic pulmonary artery denervation (TPADN) attenuated pulmonary artery (PA) remodeling, improved right ventricular (RV) function, and affected underlying mechanisms. We also explored the distributions of sympathetic nerves (SNs) around human PAs for clinical translation.

Approach and Results—

We identified numerous SNs in adipose and connective tissues around the main PA trunks and bifurcations in male Sprague Dawley rats, which were verified in samples from human heart transplant patients. Pulmonary arterial hypertensive rats were randomized into TPADN and sham groups. In the TPADN group, SNs around the PA trunk and bifurcation were completely and accurately removed under direct visualization. The sham group underwent thoracotomy. Hemodynamics, RV function, and pathological changes in PA and RV tissues were measured via right heart catheterization, cardiac magnetic resonance imaging, and pathological staining, respectively. Compared with the sham group, the TPADN group had lower mean pulmonary arterial pressures, less PA and RV remodeling, and improved RV function. Furthermore, TPADN inhibited neurohormonal overactivation of the sympathetic nervous system and renin-angiotensin-aldosterone system and regulated abnormal expressions and signaling of neurohormone receptors in local tissues.

Conclusions—

There are numerous SNs around the rat and human main PA trunks and bifurcations. TPADN completely and accurately removed the main SNs around PAs and attenuated pulmonary arterial hypertensive progression by inhibiting excessive activation of the sympathetic nervous system and renin-angiotensin-aldosterone system neurohormone-receptor axes.

Degeneration and regeneration of perivascular innervation in arterial grafts

Because the understanding of postoperative changes in arterial graft innervation is limited, this study was performed to characterize neuronal degeneration and regeneration events immunohistochemically in femoral arterial grafts transplanted to carotid arteries in rats. Specimens taken 1 day, 3 days, 7 days, 1 month, 3 months, and 5 months after surgery were assessed for vasoactive intestinal peptide, neurofilaments, growth-associated protein 43, tyrosine hydroxylase, and nitric oxide synthase isoenzymes. During neuronal degeneration, vasoactive intestinal peptide disappeared within 1 day, transmitter-synthesizing enzymes (nitric oxide synthase and tyrosine hydroxylase) had vanished by day 7, and neurofilaments (cytoskeletal markers) had essentially disappeared after 1 week. In the regeneration phase, the most robust axonal growth, as visualized by growth-associated protein 43, was observed at 1 month, followed by a gradual increase in neurotransmitter markers at 1 and 3 months, whereas the neurofilaments increased gradually up to the end of the 5-month observation period. Reinnervation proceeded from the proximal carotid (host) trunk distally to the graft. Axonal re-growth occurred mainly in arterial adventitia. Innervation density, as visually assessed, was denser in the graft than in the host. These findings suggest that 1) the main sequence of degeneration and regeneration follows that reported in other models of neuronal degeneration; 2) reinnervation of the arterial grafts comes mainly from the host arteries; and 3) the innervation density in the graft may differ from that in the host, which may suggest target-derived regulation of innervation. The latter finding may have clinical implications. It suggests that for a good outcome it would be beneficial to choose a sparsely innervated graft rather than a densely innervated one.

Innervation of ectopic endometrium in a rat model of endometriosis

Endometriosis (ENDO) is a disorder in which vascularized growths of endometrial tissue occur outside the uterus. Its symptoms include reduced fertility and severe pelvic pain. Mechanisms that maintain the ectopic growths and evoke symptoms are poorly understood. One factor not yet considered is that the ectopic growths develop their own innervation. Here, we tested the hypothesis that the growths develop both an autonomic and a sensory innervation. We used a rat model of surgically induced ENDO whose growths mimic those in women. Furthermore, similar to women with ENDO, such rats exhibit reduced fertility and increased pelvic nociception. The ENDO was induced by autotransplanting, on mesenteric cascade arteries, small pieces of uterus that formed vascularized cysts. The cysts and healthy uterus were harvested from proestrous rats and immunostained using the pan-neuronal marker PGP9.5 and specific markers for calcitonin gene-related peptide (CGRP) (sensory C and A delta fibers), substance P (SP) (sensory C and A delta fibers) and vesicular monoamine transporter (sympathetic fibers). Cysts (like the uterus) were robustly innervated, with many PGP9.5-stained neurites accompanying blood vessels and extending into nearby luminal epithelial layers. CGRP-, SP-, and vesicular monoamine transporter-immunostained neurites also were observed, with CGRP and SP neurites extending the furthest into the cyst lining. These results demonstrate that ectopic endometrial growths develop an autonomic and sensory innervation. This innervation could contribute not only to symptoms associated with ENDO but also to maintenance of the ectopic growths.

Autotransplantation of rat parathyroid glands: a study on morphological changes

BACKGROUND

Autotransplantation of parathyroid glands in man is performed to preserve parathyroid function after surgery. In a rat model, we performed autotransplantation into the renal subcapsular space to examine reinnervation and changes in cell activity in the transplanted glands.

METHODS

Parathyroids grafted for 1-20 weeks were examined immunocytochemically for general and specific neuroendocrine markers to visualize nerve fibers and glandular cells and for bromodeoxyuridine to determine cell proliferation. In situ hybridization was used to localize and quantitate chromogranin A and parathyroid hormone (PTH) mRNA expression.

RESULTS

Reinnervation was observed as early as 1 week after transplantation in that nerve fibers containing the general neuronal marker protein gene product 9.5 appeared along blood vessels. During the following 20 weeks, the nerve fiber density increased gradually. One week after transplantation, the immunoreaction intensity for PTH, chromogranin A, and pancreastatin was lower than in control glands. Bromodeoxyuridine-labeled cells were fewer than in control glands at 1 week and at 5-10 weeks after transplantation. The density of PTH mRNA labeling was lower than in control glands during the whole time period studied and reached a minimum after 10 weeks. The density of chromogranin A mRNA labeling was unaffected at 1 and 3 weeks after transplantation and then decreased to a minimum at 10 weeks after transplantation; at 20 weeks, the chromogranin A mRNA labeling had again reached the level in control glands.

CONCLUSION

The changes in PTH and chromogranin A immunoreaction intensity and mRNA density indicate reduced hormone production for several weeks after transplantation. Our results using transmitter-specific markers indicate a rapid ingrowth of mostly sympathetic nerve fibers, preferentially around blood vessels. Later on, parasympathetic and sensory nerve fibers reached the grafts. The parathyroid innervation may be of importance for parathyroid hormone regulation, and the finding of an early reinnervation could be of clinical importance.