Sympathetic reinnervation of rat kidney grafts

Sympathetic Reinnervation of Intact and Upper Follicle Xenografts into BALB/c-nu/nu Mice

Increasing concerns about hair loss affect people's quality of life. Recent studies have found that sympathetic nerves play a positive role in regulating hair follicle stem cell activity to promote hair growth. However, no study has investigated sympathetic innervation of transplanted follicles. Rat vibrissa follicles were extracted and implanted under the dorsal skin of BALB/c-nu/nu mice using one of two types of follicles: (1) intact follicles, where transplants included bulbs, and (2) upper follicles, where transplants excluded bulbs. Follicular samples were collected for hematoxylin and eosin staining, immunofluorescence staining for tyrosine hydroxylase (TH, a sympathetic marker) and enzyme-linked immunosorbent assays. At 37 days after implantation in both groups, follicles had entered anagen, with the growth of long hair shafts; tyrosine-hydroxylase-positive nerves were innervating follicles (1.45-fold); and norepinephrine concentrations (2.03-fold) were significantly increased compared to 5 days, but did not return to normal. We demonstrate the survival of intact and upper follicle xenografts and the partial restoration of sympathetic reinnervations of both transplanted follicles.

The Effects of Renal Nerve Denervation on Blood Pressure and Target Organs in Different Hypertensive Rat Models

Background

Hypertension contributes to the progression of cardiac remodeling and renal damage. In turn, renal sympathetic hyperactivation showed elevated sympathetic nervous system activity and led to blood pressure increase in certain patients. The purpose of this study was to observe the effect of renal nerve denervation on blood pressure and target organ changes in two hypertensive rat models.

Methods

Hypertensive rats were randomly divided into a renal denervation (RDN) group and sham operation group. Wistar–Kyoto (WKY) rats of the same age were set as the baseline control group. In the secondary hypertension model, SD rats were randomly divided into five groups. Blood pressure and bodyweight were measured every week until they were euthanized.

Results

The two rat models underwent RDN at key timepoints. At these timepoints, the hearts and kidneys were collected for norepinephrine and angiotensin II measurements and histological analysis.

Conclusion

RDN performed before development of hypertension showed a significant antihypertensive effect on the secondary hypertension model.

Complex reinnervation pattern after unilateral renal denervation in rats

Renal denervation (DNX) is a treatment for resistant arterial hypertension. Efferent sympathetic nerves regrow, but reinnervation by renal afferent nerves has only recently been shown in the renal pelvis of rats after unilateral DNX. We examined intrarenal perivascular afferent and sympathetic efferent nerves after unilateral surgical DNX. Tyrosine hydroxylase (TH), CGRP, and smooth muscle actin were identified in kidney sections from 12 Sprague-Dawley rats, to distinguish afferents, efferents, and vasculature. DNX kidneys and nondenervated kidneys were examined 1, 4, and 12 wk after DNX. Tissue levels of CGRP and norepinephrine (NE) were measured with ELISA and mass spectrometry, respectively. DNX decreased TH and CGRP labeling by 90% and 95%, respectively (P < 0.05) within 1 wk. After 12 wk TH and CGRP labeling returned to baseline with a shift toward afferent innervation (P < 0.05). Nondenervated kidneys showed a doubling of both labels within 12 wk (P < 0.05). CGRP content decreased by 72% [3.2 ± 0.3 vs. 0.9 ± 0.2 ng/gkidney; P < 0.05] and NA by 78% [1.1 ± 0.1 vs. 0.2 ± 0.1 pmol/mgkidney; P < 0.05] 1 wk after DNX. After 12 wk, CGRP, but not NE, content in DNX kidneys was fully recovered, with no changes in the nondenervated kidneys. The use of phenol in the DNX procedure did not influence this result. We found morphological reinnervation and transmitter recovery of afferents within 12 wk after DNX. Despite morphological evidence of sympathetic regrowth, NE content did not fully recover. These results suggest a long-term net surplus of afferent influence on the DNX kidney may be contributing to the blood pressure lowering effect of DNX.

Effects of renal denervation on renal pelvic contractions and connexin expression in rats

AIMS

The renal pelvis shows spontaneous rhythmic contractile activity. We assessed to what extent this activity depends on renal innervation and studied the role of connexins in pelvic contractions.

METHODS

Rats underwent unilateral renal denervation or renal transplantation. Renal pelvic pressure and diuresis were measured in vivo. Spontaneous and agonist-induced contractions of isolated renal pelves were investigated by wire myography. Rat and human renal pelvic connexin mRNA abundances and connexin localization were studied by real-time PCR and immunofluorescence respectively.

RESULTS

Renal denervation or transplantation increased renal pelvic pressure in vivo by about 60 and 150%, respectively, but did not significantly affect pelvic contraction frequency. Under in vitro conditions, isolated pelvic preparations from innervated or denervated kidneys showed spontaneous contractions. Pelves from denervated kidneys showed about 50% higher contraction frequencies than pelves from innervated kidneys, whereas contraction force was similar in pelves from denervated and innervated kidneys. There was no denervation-induced supersensitivity to noradrenaline or endothelin-1. Renal denervation did not increase pelvic connexin37, 40, 43 or 45 mRNA abundances. Gap junction blockade had no effect on spontaneous pelvic contractile activity.

CONCLUSIONS

The denervation-induced effect on pelvic pressure may be the consequence of the enhanced diuresis. The mechanisms underlying the denervation-induced effects on pelvic contraction frequency remain unknown. Our data rule out a major role for two important candidates, by showing that renal denervation neither induced supersensitivity to contractile agonists nor increased connexin mRNA abundance in the pelvic wall.

Renal Sympathetic Denervation in Rats

Experimental renal sympathetic denervation is a well-established technique. Classically, renal sympathetic denervation is achieved by dorsal rhizotomy. While more recently, direct renal sympathetic denervation is typically applied by stripping all visible renal nerve bundles followed by painting with a solution of 10 % phenol in ethanol to remove the remaining nerves. In clinical settings, a reliable marker of renal sympathetic denervation or renal sympathetic overactivity has not been established. However, in experimental models, successful renal sympathetic denervation is validated by a decrease in renal norepinephrine content levels. This facilitates the assessment of incomplete denervation by technical failure and reinnervation for long-term experimental models. In this chapter, we introduce comprehensive methods for direct renal sympathetic denervation and measurement of renal norepinephrine content levels.

Renal denervation in the management of resistant hypertension: current evidence and perspectives

PURPOSE OF REVIEW

Catheter-based renal denervation has emerged as a novel treatment modality for resistant hypertension. This review summarizes the current evidence on this procedure in treatment of resistant hypertension, limitations of available evidence and questions to be answered.

RECENT FINDINGS

The SYMPLICITY studies showed that renal denervation is feasible in treating resistant hypertension, but failed to provide conclusive evidence on the size and durability of the antihypertensive, renal and sympatholytic effects, as well as the long-term safety. The definition of resistant hypertension was loose in the SYMPLICITY studies and the management of resistant hypertension was suboptimal. Future studies should have a randomized design and enroll truly resistant hypertension patients by excluding secondary hypertension, white-coat hypertension and nonadherent patients. Questions to be addressed by the ongoing and future trials include the long-term efficacy and safety of this procedure, identification of responders and uncovering of the underlying mechanisms.

SUMMARY

Only well-designed, randomized clinical trials addressing the limitations of the SYMPLICITY studies will be able to demonstrate whether renal denervation is an efficacious treatment modality in resistant hypertension and in which patients. For now, renal denervation remains an experimental procedure and should only be offered to truly resistant hypertensive patients in a research context after careful selection.

Updated ESH position paper on interventional therapy of resistant hypertension

Out of the overall hypertensive population it is estimated that approximately 10% have treatment resistant hypertension (TRH). Percutaneous catheter-based transluminal renal ablation (renal denervation [RDN] by delivery of radiofrequency energy) has emerged as a new approach to achieve sustained blood pressure reduction in patients with TRH. This innovative interventional technique is now available across Europe for severe TRH for those patients in whom pharmacologic strategies and lifestyle changes have failed to control blood pressure below target (usually <140/90 mmHg). In 2012, the "ESH position paper: renal denervation - an interventional therapy of resistant hypertension" was published to facilitate a better understanding of the effectiveness, safety, limitation and unresolved issues. We have now updated this position paper since numerous studies have been published over the last year providing more data about the rationale, therapeutic efficacy and safety of RDN. In the upcoming ESH/ESC guidelines for the management of arterial hypertension, therapeutic options of treatment resistant hypertension will be addressed, but only briefly, and thus it is the focus of this paper to provide detailed and updated information on this innovative interventional technique.

Renal denervation: intractable hypertension and beyond

BACKGROUND

Hypertension continues to be a major burden of public health concern despite the recent advances and proven benefit of pharmacological therapy. A certain subset of patients has hypertension resistant to maximal medical therapy and appropriate lifestyle measures. A novel catheter-based technique for renal denervation (RDN) as a new therapeutic avenue has great promise for the treatment of refractory hypertension.

SUMMARY

This review included the physiology of the renal sympathetic nervous system and the renal nerve anatomy. Furthermore, the RDN procedure, technology systems, and RDN clinical trials as well as findings besides antihypertensive effects were discussed. Findings on safety and efficacy seem to suggest that renal sympathetic denervation could be of therapeutic benefit in refractory hypertensive patients. Despite the fast pace of development in RDN therapies, only initial and very limited clinical data are available. Large gaps in knowledge concerning the long-term effects and consequences of RDN still exist, and solid, randomized data are warranted.

Redo of percutaneous renal denervation in a patient with recurrent resistant hypertension after primary treatment success

A 79-year-old patient was treated with percutaneous renal denervation (RDN) due to resistant arterial hypertension in the summer of 2010. After primary treatment success with a decrease of blood pressure from 170/100 to 130/80 mm Hg 6 months postablation, the blood pressure rose again at 12 months despite maintenance of the pharmacologic regimen and the decision was made to perform a second RDN procedure. Three months following the second RDN procedure, blood pressure was lowered to 130/77 mm Hg.

Renal denervation for treatment-resistant hypertension

Hypertension is a major public health concern that is increasing in prevalence. Lifestyle and pharmacological management are not always sufficient to control blood pressure and treatment-resistant hypertension is a recognized clinical challenge. Renal sympathetic denervation (RSD) represents a new frontier in the treatment of resistant hypertension.

RESULTS

from the Symplicity HTN-1 and HTN-2 trials have demonstrated evidence that suggests RSD can safely reduce blood pressure in patients with this condition. More research is needed to verify these data, clarify unanswered questions and assess future applications of RSD. This review provides a detailed overview on the history of hypertension, treatment-resistant hypertension, the rationale behind RSD, current evidence and potential future applications of RSD. An overview of current and upcoming RSD devices is also included.

Sprouted innervation into uterine transplants contributes to the development of hyperalgesia in a rat model of endometriosis

Endometriosis is an enigmatic painful disorder whose pain symptoms remain difficult to alleviate in large part because the disorder is defined by extrauteral endometrial growths whose contribution to pain is poorly understood. A rat model (ENDO) involves autotransplanting on abdominal arteries uterine segments that grow into vascularized cysts that become innervated with sensory and sympathetic fibers. ENDO rats exhibit vaginal hyperalgesia. We used behavioral, physiological, and immunohistochemical methods to test the hypothesis that cyst innervation contributes to the development of this hyperalgesia after transplant. Rudimentary sensory and sympathetic innervation appeared in the cysts at two weeks, sprouted further and more densely into the cyst wall by four weeks, and matured by six weeks post-transplant. Sensory fibers became abnormally functionally active between two and three weeks post-transplant, remaining active thereafter. Vaginal hyperalgesia became significant between four and five weeks post-transplant, and stabilized after six to eight weeks. Removing cysts before they acquired functional innervation prevented vaginal hyperalgesia from developing, whereas sham cyst removal did not. Thus, abnormally-active innervation of ectopic growths occurs before hyperalgesia develops, supporting the hypothesis. These findings suggest that painful endometriosis can be classified as a mixed inflammatory/neuropathic pain condition, which opens new avenues for pain relief. The findings also have implications beyond endometriosis by suggesting that functionality of any transplanted tissue can be influenced by the innervation it acquires.

Body mass index and glomerular hyperfiltration in renal transplant recipients: cross-sectional analysis and long-term impact

Obesity is a risk factor for renal graft loss. Higher body mass index (BMI) in native kidneys is associated with glomerular hyperfiltration. Whether higher BMI in renal transplants is associated with hyperfiltration is unknown. We investigated the impact of BMI on renal hemodynamics 1 year post-transplant. We analyzed glomerular filtration rate (GFR, (125)I-iothalamate) and effective renal plasma flow (ERPF, (131)I-hippurate) in 838 kidney transplants. Data were analyzed for all patients and for the subpopulation without diabetes. Long-term impact of BMI and renal hemodynamics were explored by Cox-regression. With higher BMI GFR and filtration fraction (FF) increased significantly. Multivariate analysis supported impact of BMI on GFR (adjusted r(2) of the model 0.275) and FF (adjusted r(2) of the model 0.158). This association was not explained by diabetes mellitus. On Cox-regression analysis, lower GFR and higher FF were independent determinants of overall graft loss and graft loss by patient mortality. Lower GFR and higher BMI were determinants of death-censored graft loss, with borderline contribution of higher FF. In renal transplants higher BMI is independently associated with higher GFR and FF one year posttransplant, suggesting glomerular hyperfiltration with altered afferent-efferent balance. Mechanisms underlying the long-term prognostic impact of hyperfiltration deserve further exploration.

BOLD-MRI assessment of intrarenal oxygenation and oxidative stress in patients with chronic kidney allograft dysfunction

Blood oxygen level-dependent (BOLD) magnetic resonance imaging (MRI) uses deoxyhemoglobin as an endogenous contrast agent for the noninvasive assessment of tissue oxygen bioavailability. We hypothesized that intrarenal oxygenation was impaired in patients with chronic allograft nephropathy (CAN). Ten kidney-transplant recipients with CAN and nine healthy volunteers underwent BOLD-MRI. Medullary R2* (MR2*) and cortical R2* (CR2*) levels (measures directly proportional to tissue deoxyhemoglobin levels) were determined alongside urine and serum markers of oxidative stress (OS): hydrogen peroxide (H(2)O(2)), F(2)-isoprostanes, total nitric oxide (NO), heat shock protein 27 (HSP27), and total antioxidant property (TAOP). Mean MR2* and CR2* levels were significantly decreased in CAN (increased local oxyhemoglobin concentration) compared with healthy volunteers (20.7 +/- 1.6 vs. 23.1 +/- 1.8/s, P = 0.03 and 15.9 +/- 1.9 vs. 13.6 +/- 2.3/s, P = 0.05, respectively). There was a significant increase in serum and urine levels of H(2)O(2) and serum HSP27 levels in patients with CAN. Conversely, urine NO levels and TAOP were significantly increased in healthy volunteers. Multiple linear regression analyses showed a significant association between MR2* and CR2* levels and serum/urine biomarkers of OS. BOLD-MRI demonstrated significant changes in medullary and cortical oxygen bioavailability in allografts with CAN. These correlated with serum/urine biomarkers of OS, suggesting an association between intrarenal oxygenation and OS.

Noninvasive Assessment of Early Kidney Allograft Dysfunction by Blood Oxygen Level-Dependent Magnetic Resonance Imaging

BACKGROUND

Blood oxygen level-dependent (BOLD) magnetic resonance imaging (MRI) is a noninvasive method to assess tissue oxygen bioavailability, using deoxyhemoglobin as an endogenous contrast agent. We hypothesized that BOLD-MRI could accurately discriminate different types of rejection early after kidney transplantation.

METHODS

Twenty-three patients underwent imaging in the first four months posttransplant. Five had normal functioning transplants and 18 had biopsy-proven acute allograft dysfunction (acute tubular necrosis [ATN, n=5] and acute rejection [n=13] including borderline rejection: n=3; IA rejection: n=4; IIA rejection: n=6: C4d(+) rejection: n=9).

RESULTS

Mean medullary R2* (MR2*) levels (a measure directly proportional to tissue deoxyhemoglobin levels) were significantly higher in normal functioning allografts (R2*=24.3/s+/-2.3) versus acute rejection (R2*=16.6/s+/-2.1) and ATN (R2*=20.9/s+/-1.8) (P<0.05). The lowest MR2* levels were observed in acute rejection episodes with vascular injury i.e. IIA and C4d (+). Similarly, the lowest medullary to cortical R2* ratios (MCR2*) were present in allografts with IIA (1.24+/-0.05) and C4d(+) rejection (1.26+/-0.06). ROC curve analyses suggested that MR2* and MCR2* values could accurately discriminate acute rejection in the early posttransplant period.

CONCLUSIONS

BOLD-MRI demonstrated significant changes in medullary oxygen bioavailability in allografts with biopsy-proven ATN and acute rejection, suggesting that there may be a role for this noninvasive tool to evaluate kidney function early after transplantation.

Renal vascular response to static handgrip exercise: sympathetic vs. autoregulatory control

Static exercise causes activation of the sympathetic nervous system, which results in increased blood pressure (BP) and renal vascular resistance (RVR). The question arises as to whether renal vasoconstriction that occurs during static exercise is due to sympathetic activation and/or related to a pressure-dependent renal autoregulatory mechanism. To address this issue, we monitored renal blood flow velocity (RBV) responses to two different handgrip (HG) exercise paradigms in 7 kidney transplant recipients (RTX) and 11 age-matched healthy control subjects. Transplanted kidneys are functionally denervated. Beat-by-beat analyses of changes in RBV (observed via duplex ultrasound), BP, and heart rate were performed during HG exercise in all subjects. An index of RVR was calculated as BP/RBV. In protocol 1, fatiguing HG exercise (40% of maximum voluntary contraction) led to significant increases in RVR in both groups. However, at the end of exercise, RVR was more than fourfold higher in control subjects than in the RTX group (88 vs. 20% increase over baseline; interaction, P < 0.001). In protocol 2, short bouts of HG exercise (15 s) led to significant increases in RVR at higher workloads (50 and 70% of maximum voluntary contraction) in the control subjects (P < 0.001). RVR did not increase in the RTX group. In conclusion, we observed grossly attenuated renal vasoconstrictor responses to exercise in RTX subjects, in whom transplanted kidneys were considered functionally denervated. Our results suggest that renal vasoconstrictor responses to exercise in conscious humans are mainly dependent on activation of a neural mechanism.

Sympatho-renal interactions in the determination of arterial pressure: role in hypertension

Renal mechanisms and the sympathetic nervous system contribute to the development of arterial hypertension. Renal transplantation experiments in spontaneously hypertensive rats (SHRs) were performed to investigate how the sympathetic nervous system and the kidneys interact during the development and maintenance of hypertension. Our findings indicate that the rise in arterial pressure that occurs after transplantation of a kidney from a SHR into normotensive recipients is not mediated by elevations in sympathetic activity. However, chronic reductions in sympathetic tone reduce the rise in arterial pressure which can be induced by SHR renal grafts in normotensive recipients. Untreated SHRs transplanted with a kidney from sympathectomized donors have lower arterial pressure and reduced sodium sensitivity of arterial pressure compared to SHRs transplanted with a kidney from hydralazine-treated donors. It is concluded that chronic non-adapting changes in sympathetic activity modulate the degree to which renal mechanisms can cause hypertension in SHRs. Severe reduction in sympathetic tone during early ontogeny causes long-term changes in renal function that mitigate hypertension development in SHRs even when the extrarenal neuro-hormonal environment is restored.

The outcome of renal denervation for managing loin pain haematuria syndrome

OBJECTIVE

To evaluate the outcome of renal denervation for the treatment of loin pain-haematuria syndrome (LPHS), a rare syndrome of unknown cause associated with debilitating and intractable loin pain.

PATIENTS AND METHODS

The case notes of 32 patients having 41 renal denervations were reviewed. Data collected included patient demographics, possible causes, cure or not after renal denervation, time to recurrence of pain after denervation and further operative intervention for managing LPHS.

RESULTS

Full data were available for 24 patients (13 women; median age 43 years, range 28-74) having 33 denervations (eight bilateral and one repeat) with a median follow-up of 39.5 months. Most patients had no identifiable underlying cause although many had initially been diagnosed as having stone disease (42%) or pyelonephritis (25%), but with no corroborative evidence. All patients had been extensively investigated and had normal urine samples and cytology, and no abnormality on intravenous urography, renal tract ultrasonography and isotopic renography. Twenty-four renal denervations (73%) were followed by recurrent ipsilateral pain at a median (range) of 11 (0-120) months after surgery. Nine denervations (25%) in six men and two women were curative (median follow-up 16.5 months). Of those with recurrent pain, nine (38%) proceeded to nephrectomy, of whom three then developed loin pain on the contralateral side and two developed disabling wound pain. The analgesic requirement was less after eight non-curative denervations. There were no significant postoperative complications.

CONCLUSIONS

Renal denervation has only a 25% success rate for managing pain associated with LPHS and should be used cautiously for this indication. Men had more benefit from the treatment; a third of patients had less requirement for analgesic after non-curative denervation.

Impact of renal transplantation on small vessel reactivity

BACKGROUND

The function of large arteries is altered after renal transplantation. Whether transplantation also induces agonist-dependent functional changes in small arterial renal and extrarenal vessels has not yet been studied.

METHODS

Chronic rejection was induced by grafting Lewis rats with kidneys from Fischer rats (FL). Rats that underwent transplantation were bilaterally nephrectomized. Rats that underwent syngeneic transplantation, uninephrectomized rats, uninephrectomized rats with denervated kidneys or with kidneys made ischemic, and native rats served as controls. All animals were treated with cyclosporine for 10 days. Eighteen weeks after surgery, the reactivity of small arteries (220-270 microm) was tested by myography.

RESULTS

Weight gain, glomerular filtration rate, and arterial pressure were similar in all groups, whereas proteinuria was elevated in FL. Only kidneys from FL showed glomerular lesions, tubular atrophy, and vasculopathy. Responsiveness of coronary, mesenteric, and femoral resistance vessels to both constrictor and dilator agonists was similar in transplanted and nontransplanted animals. Resistance vessels obtained from both allogeneically and syngeneically transplanted kidneys were more sensitive to norepinephrine, phenylephrine, angiotensin II, and vasopressin than renal vessels from weight-matched controls. Vasodilation in response to acetylcholine and sodium nitroprusside was mitigated in transplanted versus nontransplanted kidneys.

CONCLUSIONS

In rat renal transplantation, renal resistance vessel responsiveness to constrictor or dilator stimuli is altered. Extrarenal small vessel function is not affected. The changes in function of renal resistance vessels are not explained by reduction of nephron mass, denervation, ischemia, or chronic rejection.

PTH pulsatility but not calcium sensitivity is restored after total parathyroidectomy with heterotopic autotransplantation

In healthy humans, parathyroid hormone (PTH) is secreted via basal mode with superimposed oscillatory bursts every 8 to 12 min. Amplitude and frequency changes mediate the instantaneous response of the parathyroids to changes in ambient Ca(2+) concentrations. The parathyroid gland tetrad may be synchronized by autonomic innervation. This study investigated the effect of total parathyroidectomy and heterotopic autotransplantation of parathyroid tissue (PTX) on PTH secretion patterns in nine patients with end-stage renal disease. Intact-PTH versus time concentration profiles were obtained early (1 to 8 wk, n = 4) or late (15 to 33 mo, n = 5) after PTX. In four patients late after PTX, Ca(2+) responsiveness of PTH secretion was additionally investigated by citrate and calcium clamp studies. The nonrandomness of plasma PTH fluctuations was assessed by the approximate entropy (ApEn) statistic, and secretion characteristics by multiparametric deconvolution analysis. Results were compared with those of matched normal subjects and chronic renal failure (CRF) patients without PTX. PTH burst frequency was 2.9 +/- 0.1 h(-1) early and 7 +/- 0.4 h(-1) late after PTX as compared with 8.1 +/- 0.4 h(-1) in CRF and 7 +/- 0.3 h(-1) in healthy controls. Fractional pulsatile PTH secretion was diminished after PTX (18 +/- 2%) compared with healthy controls (32 +/- 5%, P < 0.05) and CRF patients (25 +/- 4%, P = 0.05). The orderliness of PTH release was significantly reduced after PTX (ApEn: 1.59 +/- 0.03 versus 1.41 +/- 0.09 in healthy and 1.46 +/- 0.03 in CRF controls, P < 0.01). Acute hypocalcemia elicited a lesser increase in pulsatile PTH secretion in PTX patients (147 +/- 134%) than in the CRF (500 +/- 92%, P = 0.05) and healthy controls (1410 +/- 290%, P < 0.05), mainly due to a diminished mass of PTH secreted per burst. Pulsatile PTH secretion was also resistant to hypercalcemia, wherein the suppression of burst mass was significantly reduced compared with that in healthy controls. In conclusion, pulsatile PTH secretion is partially restored within 2 yr of PTX. However, the capacity of the autotransplanted tissue to adapt to changes in ionized calcium remains profoundly disturbed.

Experimental study on hepatic reinnervation after orthotopic liver transplantation in rats

BACKGROUND/AIMS

The present study examined whether extrinsic hepatic reinnervation occurred after orthotopic liver transplantation (OLT) in rats.

METHODS

Inbred male Lewis rats were the recipients and females the donors. Tissue specimens were obtained postoperatively from the stump of a recipient's hepatoduodenal ligament (A), and the hepatic hilus (B) and peripheral parenchyma (C) of liver allografts, up to 6 months post-operation. Specimens were subjected to immunohistochemical examination using growth-associated protein (GAP)-43 as an axonal marker and transmission electron microscopy (TEM) for observing regenerating axons, as well as the polymerase chain reaction assay to detect the rat sex-determining region Y (SRY) protein gene of the regenerating nerves.

RESULTS

At site A, GAP-43-positive nerve axons were identified from day 1 to 1 month post-OLT and SRY protein genes were expressed at and after 3 days post-OLT. At site B, GAP-43-positive axons were observed between 3 days and 1 month, and SRY protein genes were detected at 1 month post-OLT and thereafter. TEM confirmed the presence of regenerating axons at and after 3 days post-OLT.

CONCLUSIONS

The results demonstrated that regenerating nerve fibers originating from the recipients reinnervated liver allografts. This extrinsic innervation occurred shortly after OLT, and most likely terminated after about 3 months.