Reproductive fitness in roe bucks (Capreolus capreolus): seasonal timing of testis function

An updated insight on testicular hemodynamics: Environmental, physiological, and technical perspectives in farm and companion animals

In all organs, control of blood flow is important but might be particularly critical for testicular functions. This is because of the very low oxygen concentration and high metabolic rate of the seminiferous tubules, the physiological temperature of the testis, and its location outside the abdominal cavity. Many factors affect the characteristics of TBF in farm and companion animals, such as environment (thermal and seasonal effects) and physiological (species, breeds, age, body weight, and sexual maturity). Thermal environment stress has detrimental effects on spermatogenesis and consequently has more serious impacts on both human and animal fertility. Numerous studies have been performed to assess TBF in different animal species including bulls, rams, bucks, alpacas, stallions, and dogs with varied results. Hence, assessment of TBF by Doppler ultrasonography is of great importance to estimate the effect of high environment temperature on testicular functions. Also, differences observed in the TBF may result from different technical aspects such as the identification of the segment of the testicular artery to be examined. In the current review, we focused on the imperative roles of TBF in various animal species. Besides, we discussed in detail various factors that could affect TBF. These factors can significantly modify the TBF and thus should be considered when establishing reference values in farm animals for better clinical diagnosis. The information provided in this review is valuable for researchers and veterinarians to help them a better understanding of testicular hemodynamics for the proper evaluation of breeding soundness examination in males.

Uncovering the Physiological Mechanisms Underlying the Roe Deer (Capreolus capreolus) Testicular Cycle: Analyses of Gelatinases and VEGF Patterns and Correlation with Testes Weight and Testosterone

Simple Summary

The roe deer (Capreolus capreolus) is a wild, small ruminant common in Europe and Asia with a peculiar reproductive cycle. The adult male shows a complete suspension of spermatozoa production during the winter that start again in spring with the peak of sexual activity in summer (July–August). The physiological mechanism underlying such a cycle is yet to be clarified. The work aimed at the analysis of some molecules, like gelatinases (MMP) and vascular growth factor, physiologically involved in tissue remodeling, in roe deer samples collected before (June–July) and after (August–September) the rutting period. Samples were provided by hunters of the Bologna Apennines area (Italy) according to the regional hunting plan. The result showed a post-rut reduction of testicular weight and testosterone, indicative of testes involution, correlated with an increase in pro-MMP2, the latent gelatinase capable of sustaining spermatogenesis once activated. It can be assumed that gelatinases are involved in the testicular cycle and start accumulating after the rutting period to be then activated in preparation of the next reproductive season inducing spermatozoa development and migration. Future studies on this pathway during all seasonal testicular cycles will provide more information about the interesting reproductive physiology of roe deer.

Abstract

The roe deer (Capreolus capreolus) represents a spontaneous model of testicular inactivation: During winter, bucks show a suspension of spermatogenesis that starts again in spring and peaks during the breeding season (July–August). The underlying mechanisms to the regulation of the cyclic testicular changes are still not fully clear but seem to be imputable to the spermatogenic cell line since other testicular cell populations remain stable without apoptotic phenomena. The aim of the study was to investigate apoptosis, gelatinases (MMP2 and 9), their inhibiting factors (TIMP 1-2), and two isoforms of vascular endothelial growth factor (VEGF121 and 165) with its receptors (VEGFR1-2) in testes collected during pre- and post-rut periods, and to correlate them with testicular weight (TW) and testosterone (TEST). Testes from 18 adult sexually mature bucks were collected in Bologna Apennines (Italy). Samples were weighed and parenchyma collected. Radioimmunoassay, real-time PCR, and zymography were performed. The results showed a post-rut decrease in TW and TEST and an increase in proMMP2, also highlighting a correlation between the gelatinases and the testicular functionality. The VEGF pattern did not show modifications nor correlation with TW and TEST. Overall, gelatinases and their inhibitors, described herein for the first time in roe deer testes, seem to play an important role in the testicular cycle.

Vascular endothelial growth factor A is a putative paracrine regulator in seasonally controlled spermatogenesis: insights from a ruminant model, the roe deer

Vascular endothelial growth factor A (VEGFA) influences spermatogenesis, but its impact on seasonally regulated sperm production is still not fully understood. Thus, we investigated both expression levels and localisation of VEGFA and its receptors VEGFR1 and 2 in roe buck testis via real-time reverse transcription polymerase chain reaction and immunohistochemistry in relation to seasonal changes in the cellular composition of the testis. VEGFA was expressed by interstitial cells while its receptors were found on endothelial and perivascular cells. Inside the tubules, VEGFA was located in spermatogonia and spermatocytes, VEGFR1 was present on elongating spermatids and VEGFR2 on Sertoli cells. VEGFR1 mRNA was expressed tenfold lower than VEGFR2 and VEGF mRNAs. Relative VEGF and VEGFR2 expression (divided by the number of VEGFA and VEGFR2 expressing cells) showed an increase towards the rut (July/August) and a decrease thereafter. The results suggest involvement of VEGFA in the adjustment of vascular permeability as well as in spermiogenesis and the proliferation of spermatogonia.

Moderate Seasonality in Testis Function of Domestic Cat

Adult male domestic cats are known to produce sperm throughout the year, although sexual activity is influenced by geographical location. In the northern hemisphere, feral domestic cats reproduce usually between January and July. Thus, seasonality in testicular activity might be suggested. The aim of the present study was to investigate gametogene and endocrine activity of cat testis throughout the entire year. Testes and epididymides (n = 10-12 per month) were collected after castration. Spermatogenesis was quantified by assessment of testicular sperm per testis and by flow cytometric analysis of the cells with different DNA content. Sperm from cauda epididymis were evaluated according to motility and morphological integrity. Testicular testosterone concentration was determined by enzyme immunoassay. Testis mass and sperm production varied moderately throughout the year. Significant seasonal variations were observed in the proportion of cells in the G2/M phase of cell cycle (p = 0.004) and the meiotic transformation (ratio of haploid : tetraploid cells; p = 0.021). Changes in testicular testosterone concentration were more pronounced and showed periods with high (spring) and significantly reduced testosterone levels (autumn). A marked seasonal alteration (p < 0.001) with a peak in March was assessed in the percentage of progressively motile sperm. The proportion of morphological intact sperm was also significantly higher in spring compared with winter time (p < 0.001). In conclusion, the study suggests moderate seasonal changes in quantity of sperm, more pronounced annual variation in hormone production and a distinct seasonal influence on functional sperm parameters in domestic cat.