Distinct vascular zones in the canine prostate

Canine prostate models in preclinical studies of minimally invasive interventions: part I, canine prostate anatomy and prostate cancer models

The high prevalence of prostate cancer (PCa) in elderly men and technical advances in early detection of localized PCa have led to continued efforts to develop new therapeutic options of minimally invasive nature in current urologic oncology community. Increasing newly emerging therapies are undergoing preclinical tests on the technical feasibility, efficacy and safety in animal experiments. The dog is an ideal large animal because of its similar anatomy to human and the capability allowing the use of the same medical devices applied in future clinical trials. Awareness of the local anatomy, microvascular structure, and histological features of the prostate in dogs is essential to experimental design and performance of the tested procedures and techniques. Although dogs with spontaneous PCa may be used in preclinical investigation, the low incidence and pathological features limit its utility. Alternatively, canine orthotopic PCa models have a great potential in preclinical research for this purpose. The goal of this review is to provide detailed anatomic and histological information of the canine prostate, outline the pathological and clinical characteristics of spontaneous PCa in dogs and discuss the current status of canine orthotopic PCa models.

Embolization therapy for benign prostatic hyperplasia: influence of embolization particle size on gland perfusion

PURPOSE

To assess the influence of embolic size on the therapy response of prostatic arterial embolization (PAE) based on perfusional changes seen on dynamic contrast-enhanced (DCE) magnetic resonance imaging (MRI).

MATERIALS AND METHODS

Twelve beagles underwent PAE, four dogs with each particle size: A: 100-300 μm; B: 300-500 μm; and C: 500-700 μm. Prior to and 1 month after the embolization all dogs underwent prostate DCE MRI.

RESULTS

After embolization, time to maximal perfusion intensity for prostate parenchyma increased in B (188 vs. 135 sec, P = 0.023) and C (200 vs. 120 sec, P = 0.001), while it did not change for A (139 vs. 124 sec, P = 0.39). The maximal relative intensity increased after embolization in C (3.84 vs. 2.38, P < 0.001), while it did not change for A (2.50 vs. 2.44, P = 0.36) and B (3.23 vs. 2.9, P = 0.21). The extent of visualized intraprostatic urethral wall increased after embolization in B compared with A and C, 239.5 ± 138.1% vs. 56.1 ± 34.3, P = 0.04. Enhancement changes correlated with prostate volume changes: prostate volumes in A decreased less as compared with B and C (77 ± 34% vs. 56 ± 14%), P = 0.02.

CONCLUSION

The enhancement and morphological data are useful to monitor response to therapy after embolization. Embolization with 300-500 and 500-700 μm particle may provide better results than with 100-300 μm particles in a canine model.

Variability in Weight and Histological Appearance of the Prostate of Beagle Dogs Used in Toxicology Studies

This review was performed to assess variations in weight and histologic appearance of the prostate of untreated male beagle dogs between 23 and 108 weeks of age, from two breeding centers. Data from 125 control beagle dogs from twenty-seven regulatory toxicology studies were used. Age, terminal body weight, and prostate weight were analyzed. Prostate sections were examined microscopically, and histological changes—such as development of acini, amount of secretion, and patterns of dilation and inflammation—were recorded and graded when appropriate. The influence of age, terminal body weight, and source on the weight and histological appearance of the prostate, and the degree of interanimal variation were evaluated

Intraprostatic chemotherapy: distribution and transport mechanisms

PURPOSE

The present study evaluated the tissue distribution and targeting advantage of intraprostatic chemotherapy.

EXPERIMENTAL DESIGN

We studied the delivery and spatial distribution of a fluorescent drug, doxorubicin, in the prostate of beagle dogs, after intraprostatic or i.v. administration. Drug concentrations were measured using high-performance liquid chromatography and confocal fluorescence microscopy.

RESULTS

I.v. and intraprostatic injections yielded qualitatively and quantitatively different doxorubicin distribution in the prostate. A relatively homogeneous distribution was found after i.v. administration, whereas intraprostatic injection yielded a highly heterogeneous distribution with >10-fold higher concentrations localized in a cone-shaped glandular lobule bound by fibromuscular stroma, compared with other parts of the prostate. Compared with i.v. injection, intraprostatic injection yielded, on average, approximately 100-fold higher tissue-to-plasma concentration ratio, ranging from 963-fold near the injection site to 19-fold in the contralateral half of the prostate. The drug distribution within the prostate further suggests an important role for acinar flow in intraprostatic drug transport.

CONCLUSIONS

Intraprostatic administration represents a viable option to deliver high drug concentrations within the prostate. The results further suggest the fibromuscular stroma separating the prostatic lobules as a major barrier to drug transport and convective flow as an important drug transport mechanism in the prostate.

Extraglandular and intraglandular vascularization of canine prostate

The literature on the vascularization of the canine prostate is reviewed and the clinical significance of prostate morphology is described. Scanning Electron Microscopy (SEM), combined with improved corrosion casting methods, reveal new morphological details that promise better diagnostics and treatment but also require expansion of clinical nomenclature. A proposal is made for including two previously unnamed veins in Nomina Anatomica Veterinaria (NAV). The canine prostate has two lobes with independent vascularization. Each lobe is supplied through the left and right a. prostatica, respectively. The a. prostatica sprouts three small vessels (cranial, middle, and caudal) towards the prostate gland. A. prostatica is a small-size artery whose wall structure is similar to the arteries of the muscular type. V. prostatica is a small-size valved vein. The canine prostate has capsular, parenchymal, and urethral vascular zones. The surface vessels of the capsule are predominantly veins and the diameter of arterial vessels is larger than that of the veins. The trabecular vessels are of two types: direct and branched. The prostate parenchyma is supplied by branches of the trabecular vessels. The periacinary capillaries are fenestrated and form a net in a circular pattern. The processes of the myoepithelial cells embrace both the acins and the periacinar capillaries. In the prostate ductal system. there are spermatozoa. The prostatic part of the urethra is supplied by an independent branch of a. prostatica. The prostatic urethral part is drained by v. prostatica, the vein of the urethral bulb and the ventral prostate veins. M. urethralis begins as early as the urethral prostatic part. The greater part of the white muscle fibers in m. urethralis suggest an enhanced anaerobic metabolism.