Kari L Christe

Compared with cyclosporine, ISATX247 significantly prolongs renal-allograft survival in a nonhuman primate model

Background. ISATX247 is a novel calcineurin inhibitor that has shown more potency than cyclosporine in vitro. This is the first study to compare the survival times of renal allografts in nonhuman primates treated with either ISATX247 or cyclosporine. Methods. Adult, male cynomolgus monkeys were divided into blood-group compatible and mixed-lymphocyte, stimulation-mismatched, donor-recipient pairs. Heterotopic renal transplantation and bilateral native nephrectomies were performed. The monkeys were placed into either an ISATX247 or cyclosporine treatment group. Both groups were dosed twice daily to maintain a 12-hour drug-trough level of 150 ng/mL. Whole-blood concentrations of ISATX247 and cyclosporine, complete blood counts, and serum chemistry profiles were performed three times a week. Euthanasia was performed if the serum creatinine concentration became 7 or more mg/dL or a serious complication developed. Results. The group receiving ISATX247 (n=8) survived significantly (P=0.0036) longer than the group receiving cyclosporine (n=7). The mean trough blood concentration of ISATX247 was 120±32 ng/mL and cyclosporine was 189±130 ng/mL. The average area under the curve0–12 for ISATX247 was 6045±1679 ng/mL/hr and for cyclosporine was 4919±823 ng/mL/hr. The average calcineurin inhibition at trough blood concentrations was 80±11% for ISATX247 and 48±12% for cyclosporine. Conclusions. Allografts in monkeys treated with ISATX247 survived significantly longer than those treated with cyclosporine. On the basis of survival times and degree of calcineurin inhibition, ISATX247 is a more potent immunosuppressive agent than cyclosporine in this nonhuman primate model of renal-allograft transplantation.

Noninvasive neurophysiological mapping of the lower urinary tract in adult and aging rhesus macaques

The lower urinary tract (LUT) may be activated by spinal cord stimulation, but the physiological mapping characteristics of LUT activation with noninvasive transcutaneous spinal cord stimulation (TSCS) are not known. The effects of aging on the contractile properties of the detrusor are also not well understood. Therefore, TSCS was applied over the T10/T11 to L6/L7 spinous processes in adult ( n = 6) and aged ( n = 9) female rhesus macaques. A combination of urodynamic studies and electromyography recordings of the external urethral sphincter (EUS), external anal sphincter (EAS), and pelvic floor muscles was performed. Distinct functional maps were demonstrated for TSCS-evoked detrusor and urethral pressures and for the activation of the EUS, EAS, and pelvic floor muscles. The magnitude of responses for each peripheral target organ was dependent on TSCS location and strength. The strongest detrusor contraction was observed with TSCS at the L1/L2 site in adults and the L3/L4 site in aged subjects. TSCS-evoked bladder pressure at the L1/L2 site was significantly higher for the adults compared with the aged subjects ( P < 0.05). Cumulative normalized TSCS-evoked pressures, calculated for five consecutive sites between the T11/T12 and L3/L4 levels, were significantly lower for aged compared with adult subjects ( P < 0.05). The aged animals also showed a caudal shift for the TSCS site that generated the strongest detrusor contraction. We conclude that natural aging in rhesus macaques is associated with decreased detrusor contractility, a finding of significant translational research relevance as detrusor underactivity is a common occurrence with aging in humans. NEW & NOTEWORTHY Transcutaneous spinal cord stimulation (TSCS) was used to map lower urinary tract function in adult and aged rhesus macaques. Aging was associated with decreased peak pressure responses to TSCS, reduced cumulative normalized evoked bladder pressure responses, and a caudal shift for the site generating the strongest TSCS-induced detrusor contraction. We demonstrate the utility of TSCS as a new diagnostic tool for detrusor contractility assessments and conclude that aging is associated with decreased detrusor contractility in primates.

EMG Characteristics of the External Anal Sphincter Guarding Reflex and Effects of a Unilateral Ventral Root Avulsion Injury in Rhesus Macaques (Macaca mulatta).

The external anal sphincter (EAS) is important for the maintenance of bowel continence and may be compromised by a variety of neuropathic conditions. However, large animal models for the study of EAS functions have been sparse. The EAS guarding reflex was examined by electromyography (EMG) in neurologically intact rhesus macaques ( n = 6) and at 4-6 wk after a unilateral EAS denervation from an L6-S3 ventral root avulsion (VRA) injury ( n = 6). Baseline EAS EMG recordings were quiescent in all subjects, and evoked responses showed an initial large-amplitude EMG activity, which gradually returned to baseline within 1-2 min. At 4-6 wk postoperatively, the EAS guarding reflex showed a significantly reduced EMG response duration of 47 ± 15 s and area under the curve (AUC) of 0.198 ± 0.097 mV·s compared with the corresponding evoked EAS EMG duration of 102 ± 19 s and AUC of 0.803 ± 0.225 mV·s ( P < 0.05) in the control group. Detailed time- and frequency-domain analysis of the evoked EAS EMG responses for the first 40 s showed no difference between groups for the maximum amplitude but a significant decrease for the mean amplitude across the study period and an early AUC reduction for the first 10 s in the VRA injury group. Time-frequency analysis and power spectrum plots indicated decreased intensity and a narrower midrange of frequencies in the VRA injury group. We conclude that the EAS guarding reflex in rhesus macaques shows characteristic EMG features in control subjects and signs of partial target denervation after a unilateral L6-S3 VRA injury. NEW & NOTEWORTHY The external anal sphincter guarding reflex showed initial large-amplitude peaks and a gradual return to a quiescent baseline after a rectal probe stimulus in rhesus macaques. At 4-6 wk after a unilateral ventral root avulsion (VRA) injury, the electromyography duration, mean amplitude, and area under the curve measurements were decreased. Time-frequency analysis and power spectrum plots indicated decreased intensity and a narrowed midrange of frequencies in the VRA injury cohort.

MP85-04 DEVELOPMENT OF AN UNDERACTIVE SYNDROME OF PELVIC TARGETS IN LONG-TERM STUDIES AFTER A UNILATERAL AVULSION INJURY OF LUMBOSACRAL VENTRAL ROOTS IN RHESUS MACAQUES

INTRODUCTION AND OBJECTIVES: A conus medullaris syndrome results from an Injury to the conus medullaris and cauda equine portions of the spinal cord. The clinical presentation is characterized by a lower motor neuron weakness affecting both skeletal muscles and pelvic organs with signs of paralysis, sensory disturbance and impairments of bladder, bowel, and sexual functions. The goal of the present study was to translate the unilateral lumbosacral ventral root avulsion (VRA) injury model from the rat to rhesus macaques, and to determine early and late effects of pelvic target denervation on lower urinary tract and external anal sphincter (EAS) function. METHODS: A total of 6 female rhesus macaques were included. A unilateral L6-S3 VRA injury was performed and resulted in a lesion of all preganglionic parasympathetic fibers of the ipsilateral pelvic nerve and all somatic motor fibers of the ipsilateral pudendal nerve. Urodynamic studies and EAS electromyography (EMG) were performed under ketamine anesthesia in control subjects (n1⁄46), and at 1 month and 6 months after the unilateral VRA injury (n1⁄44). RESULTS: The bladder infusion rate was between 85 and 120 mL/min to partially fill the bladder and induce reflex voiding. Poor voiding efficiency and compliance, and a slower urine flow rate were found in VRA subjects. The EAS guarding reflex was tested using a rectal probe. The maximum amplitude and area under the curve of EAS EMG were significantly decreased at 1 month after injury, but recovered at 6 months. Power spectrum (Fig. 1) showed that the peak frequency increased at 1 month after injury, but it was reduced to normal state at 6 month. The mean frequency was decreased at 1 and 6 months after injury. CONCLUSIONS: This model eliminated the parasympathetic fibers of pelvic nerve and the somatic motor fibers of pudendal nerve, which resulted in detrusor underactivity and poor EAS contractility. Power spectrum analysis indicated that fewer motor units fired during EAS contraction after injury. This model in rhesus macaques mimics the clinical phenotype of conus medullaris syndrome using a lumbosacral VRA injury approach in long-term studies. It may provide a useful model to test the utility of emerging treatments after denervation of pelvic targets. Source of Funding: LAH (California Institute for Regenerative Medicine RT3-07616; Department of Defense SC090273; Adelson Medical Research Foundation; NIH P51 OD011107); HHC (NIH DK106181)