From: Spermatogenesis. 2012 Oct 1; 2(4): 273–278.
Effects of Vasectomy and Vasectomy Reversal in Humans
Vasectomy is performed by transection of the vas deferens with suture, clips, cautery or a combination of these in the scrotal portion of the vas. This transection disrupts the mucosal, muscular, and adventitial components of the vas deferens, including the autonomic nerves that mediate vasal secretory function and peristalsis. Vasal obstruction results in increased intraluminal pressures within the testicular remnant of the vas deferens. The increased pressure may have physiologic effects on epithelial cell morphology, cellular ultrastructure, and gene expression in the vas deferens and epididymis. Moreover, sperm cannot traverse the intentionally obstructed vasal lumen, and as such they accumulate and die within the testicular remnant of the vas deferens and the epididymis. A resultant local inflammatory response occurs in reaction to dying sperm, which has significant downstream sequelae, including a systemic cellular and humoral immunologic response that may impair testicular and sperm function.The clinical importance of this response is not clear in humans. Vasal transection and occlusion cause significant, independent pathophysiologic sequelae that may or may not be reversible by microsurgical bypass of vasal and/or epididymal obstruction during vasectomy reversal in humans.
Perhaps the most relevant study on the effects of vasal transection during vasectomy on vasal innervation was conducted by Dixon et al. in 1987.8 This group utilized immunohistochemical staining and electron microscopy to evaluate the intramural autonomic innervation of the human vas deferens after vasectomy. Vasal segments were harvested during vasectomy reversal and compared with nonobstructed vasal segments acquired at the time of initial vasectomy. They found that there were marked decreases in the noradrenergic innervation of the testicular vasal remnants in previously vasectomized men. These findings imply that vasal peristalsis, which is mediated by sympathetic autonomic activity, may be irreversibly impaired after vasectomy unless significant regeneration of autonomic nerve fibers occurs in the months and years following vasectomy reversal. Unfortunately, no studies have adequately assessed the regenerative capacity of vasal intramural nerves in humans after vasovasostomy or vasoepididymostomy.
Despite the paucity of anatomic and histologic data in the literature concerning vasal nerve recovery after vasectomy reversal, a study by Shafik et al. did provide further insight regarding vasal autonomic nerve function after vasectomy and vasectomy reversal.9 Shafik utilized transcutaneous electrovasography (EVG) to record the velocity, frequency and amplitude of nerve conduction in the vas deferens in 22 healthy men, 20 vasectomized men, and 18 men after vasectomy reversal. In normal, fertile men there was minimal temporal or individual variability in vasal conduction frequency, amplitude and velocity. In contrast, vasectomized patients exhibited lower conduction frequency and amplitude in the testicular vasal remnant and irregular, described as aberrant “vasoarrhythmic” conduction patterns. One to seven years after vasectomy reversal 7 of 22 patients had successfully conceived. Interestingly, 4 of these 7 patients had a normal electrovasographic evaluation during follow-up while 3 had decreased conduction frequencies and amplitudes but did not exhibit any vasoarrhythmia. This is in contrast to the 11 patients who failed to conceive, all of whom demonstrated electrovasographic evidence of vasoarrhythmia. Notably, the likelihood of abnormal vasal conduction studies was correlated with the interval of vasal obstruction prior to vasectomy reversal. This study suggests that nerve conduction recovery may be variable after vasectomy reversal, and seems to depend upon the interval of vasal obstruction.
Significant changes also occur in epithelial cell ultra-structure within the vas deferens after vasectomy, most of which are thought to result from changes in the intraluminal pressure after vasal ligation (increased pressure in the testicular vasal remnant and decreased pressure in the abdominal vasal remnant). Andonian et al. documented this phenomenon by comparing the ultra-structural features of the abdominal and testicular vasal remnants after vasectomy (harvested at the time of vasectomy reversal) to vasal segments harvested from fertile men undergoing vasectomy.10 Transmission electron microscopic analysis of vasal segments from healthy fertile men revealed the presence of many apical cytoplasmic protrusions from epithelial principle cells into the vasal lumen. Some of these protrusions remained attached to the principle cells by a stalk, whereas others were self-contained within the lumen of the vas deferens, suggesting a secretory process. The cytoplasmic protrusions, termed “apical blebs,” contain ribosomes and endoplasmic reticulum. Interestingly, these investigators observed a marked reduction in the number of apical blebs within the testicular remnants of the vas deferens in vasectomized patients undergoing vasectomy reversal. In addition, they observed dramatic luminal narrowing, epithelial cell flattening, reduction in organelle density, and absence of apical blebs on the abdominal vasal remnant. These findings are suggestive of de-differentiation of vasal epithelium within the abdominal vasal remnant in the absence of contact with seminal plasma. Whether or not these ultra-structural changes are clinically relevant and reversible with vasovasostomy or vasoepididymostomy remains to be determined.
Morphological changes are also apparent in the human epididymides after vasectomy. Older studies of cellular morphology and ultra-structure in the epididymides of vasectomized animals have demonstrated vacuolization and increases in the number and size of lysosomes within epididymal epithelial cells11,12 as well as segmental thinning of the epithelial lining of the vas deferens and epididymis near sites of luminal distension.13 In humans, dilatation of the entire epididymal tubule has been documented, with the most pronounced increase in luminal diameter noted in the cauda. Moreover, the height of the epididymal epithelium is altered by vasectomy. In normal men, maximal epididymal height occurs in the corpus of the epididymis. After vasectomy, however, the maximal height of the epididymal epithelium occurs in the caput.14 Alternations in the height of the epithelial cell layer in the epididymis after vasectomy suggest the presence of complex molecular biological effects of vasectomy on gene expression, as epithelial cellular volume and height are thought to be indicative of underlying RNA translational and protein secretory activities.
Indeed, recent analyses of the human epididymal transcriptome using microarrays have confirmed that vasectomy causes significant alterations in epididymal gene expression. Sullivan et al. characterized the epididymal transcriptomes within each region of the epididymis in both normal and vasectomized men.15Cluster analysis of nearly 3000 genes demonstrated that expression of 1363 genes did not differ based on vasectomy status, whereas 911 genes were expressed only in normal epididymides, and 660 genes were only expressed after vasectomy. Interestingly, three of the differentially expressed genes have well-established roles in sperm maturation during epididymal transit (NPC2, CRISP1, and DCXL).
Unfortunately, no studies have directly examined the impact of vasectomy reversal on gene expression in epididymal fluid or tissue, as the only candidates for such a study would be the rare patients who desire a vasectomy subsequent to successful vasectomy reversal. However, RNA and protein detection studies in semen after vasectomy reversals have suggested that some of the alterations in epididymal gene expression that result from vasectomy may not be reversible.15 The clinical significance of such studies remains to be determined.
Vasectomy with subsequent vasectomy reversal may also be associated with detectable alterations in sperm DNA integrity. Sperm DNA integrity testing has emerged as a valuable measure of sperm quality that is predictive of natural conception, pregnancy outcomes after intrauterine insemination, and pregnancy loss after in vitro fertilization cycles.16,17 The most commonly utilized assay is the sperm chromatin structure assay (SCSA), which is a flow cytometric method that sorts sperm according to their susceptibility to DNA strand breaks upon exposure to a denaturant.
A study by Smit et al. sperm looked at DNA fragmentation with the SCSA in ejaculated semen after vasectomy reversal in 70 men. They demonstrated that sperm DNA fragmentation was increased in the vasectomy reversal patients when compared with proven fertile controls (30% vs. 15%, p < 0.001). The increase in sperm DNA fragmentation was correlated with lower sperm concentrations, lower sperm motility, and a lower percentage of morphologically normal sperm.18 Interestingly, however, there was no relationship between sperm DNA fragmentation and the likelihood of pregnancy after vasectomy reversal. Though the clinical significance of sperm DNA integrity testing after vasectomy reversal remains unclear, this supports the notion that vasectomy likely causes a myriad of molecular biological sequelae, including sperm DNA damage, which may be irreversible in some cases.
Other factors have been isolated and suggested to be associated with infertility after vasectomy reversal, including antisperm antibodies,19,20 granuloma formation21and persistent mechanical partial obstruction,22which may occur despite partial patency and sperm in the ejaculate. Epididymal function, as discussed above, has been widely studied, as has epididymal dysfunction, which is believed by many to be one of the major factors contributing to infertility after vasectomy reversal when post-surgical patency has been established by demonstrating sperm in the ejaculate. Proteins isolated in epididymal fluid harvested at the time of vasectomy reversal, such as GTPase proteins in the Ras/RAB family and Syntenins, likely play a critical in sperm maturation23 and irreversible changes in protein synthesis despite microsurgical vasovasostomy or vasoepididymostomy may play a large role in infertility despite patency after vasectomy reversal.24,25