The Role of Sperm Chromatin, Sperm Compactness and Sperm Maturity to Fertility and Embryo Development

The analysis of semen has been used to diagnose complications associated with reproductive health. It is also worth noting how the same diagnostic procedure is accurate in determining fertility as well as embryo development. The objective of this systematic reviewed was to assess the role of sperm chromatin and sperm maturity to fertility and embryo development. The study included 28 articles from the PROQUEST online data base. Several inclusion criteria were used in the selection of relevant articles. The criteria were: (1) the year of publishing, where studies published in 2000 or earlier were included, (2) studies that applied primary data, and (3) the relevance of the articles as per the independent and dependent variables. The results showed that sperm chromatin and sperm maturity play critical roles in male fertility and embryo development. Regarding the former, the researchers agreed that sperm chromatin plays a major role in the transmission of genetic information. Therefore, the resulting genetic makeup of the embryo depends on the normality or abnormalities of the sperm chromatin. Concerning the latter, this review confirmed a high level of agreement among scholars that a mature spermatozoon is more likely to fertilize than an immature one. The practical implication of this study is the justification of fertility diagnostic tests that examines the sperm chromatin structure and functionality.

The Role of Sperm Chromatin, Sperm Compactness and Sperm Maturity to Fertility and Embryo Development: A Systematic Review

INTRODUCTION

Rationale

Fertility and embryo development are critical aspects in reproductive health, as scientists seek new ways to solve the problem of infertility. A study by Tandara et al. 1 revealed that infertility affects at least 15% of couples around the globe. The current body of literature shows that sperm chromatin and sperm maturity are linked to fertility and embryo development. However, it remains unclear whether the findings from various groups of scholars from different parts of the globe match or differ.2 This systematic review bridges the gap of knowledge by providing a platform for comparing the findings of studies on the role of sperm chromatin and sperm maturity to fertility and embryo development.

Objectives

To determine the role of sperm chromatin in fertility and embryo development

To determine the role of sperm maturity in fertility and embryo development

To assess the combined role of sperm chromatin and sperm maturity to fertility and embryo development

METHODS

Protocol and Registration

This systematic review focused on peer-reviewed articles from PROQUEST, an online database dealing with various types of articles. Using the filter provided by the search engine, it was possible to select peer-reviewed articles only.

Eligibility Criteria and Information Sources

The review focused on findings regarding role of sperm chromatin and sperm maturity on fertility and embryo development. Hence, studies that were published since the beginning of the 21st Century were included. As mentioned above, articles were selected from the PROQUEST database. Specifically, the articles were searched between 12th January 2018 and 14th January 2018.

Searching

This study focused on determining the relationship between two independent variables (sperm chromatin and sperm maturity) and two dependent variables (fertility and embryo development). The information was searched using the variables as key words. Therefore, two sets of keywords were used in line with the first two objectives. The key were words were: (1) sperm chromatin and fertility and embryo development and (2) sperm maturity and fertility and embryo development.

Study Selection

Once the key words were entered on the search engine and processed, three steps were used to select the relevant articles. Firstly, reading the title allowed the identification of the promising articles. Secondly, reading the abstract assisted in narrowing down to the most relevant studies as far as the research objectives, variables, and findings were concerned. Finally, reading the full text of the selected articles allowed further elimination to the specific articles that qualified all the inclusion criteria. The same procedure was repeated as per the two independent variables.

Data Collection Process

Since this is a systematic review, the collection of data focused on the interpretation of the findings in line with the variables. As part of the data collection, information regarding the research method use and the data collection applied, the findings, and the conclusions were put together. The idea was to compare the studies and determine similarities and differences of their outcomes.

Data Items, Risk and Bias in Individual Studies

As indicated above, the independent variables were sperm chromatin and sperm maturity while the dependent variables were fertility and embryo development. These variables were used as the data items to determine how the independent variables lead to the dependent variables. Regarding the risk and bias, the study focused on the outcome and recommendations.

Summary Measures, Synthesis of Results, Risk and Bias across Studies

Since this is systematic review, the summary measure for this study was the interpretation of qualitative analysis. Therefore, the synthesis of results was done by interpreting the common keywords used to define the relationship between the independent and the dependent variables. In this study, the selection bias was the main possible factor which affected the cumulative evidence. For instance, it was necessary to identify enough articles for each independent variable to ensure a well-balanced systematic review. In doing so, some weaker articles were selected for the study on sperm maturity just to ensure that at least 12 studies are included. Additional analysis focused on the assessing the practicality of the recommendations by other researchers based on the findings in this study.

RESULTS

Study Selection

In brief, a total of 45 studies were screened. However, only 28 articles passed all the eligibility criteria after reading the full text due to a number of reasons. In particular, three articles failed the relevance criterion since the purpose of the studies diverted from the variables targeted. The remaining four articles were excluded since they were reviewed literature and meta-analyses. The exclusion of studies with secondary data was necessary to achieve uniformity and relevance. The analysis of studies with primary data only ensured the much-needed data characteristics to facilitate comparison.

Results of Individual Studies

Sperm Chromatin in Fertility and Embryo Development

The researchers agreed in unison that sperm chromatin integrity is critical factor in male fertility.3-15. Specifically, the studies showed that sperm chromatin played a critical role in transmitting paternal genetic information to the offspring.7. For instance, Shamsi, Kumar, and Dada 8 noted that the abnormal organization of genome material in the sperm cells leads to 20% of cases of male infertility. Another study by Sadeghi et al. 3 reported a higher fertilization rate for a group with less than 10% chromatin abnormality. In yet another study, Agarwal 4 revealed that defects in the chromatin structure defects leads to infertility in men. The same conclusion is evident in all the studies regarding the role of sperm chromatin in fertility and embryo development.

Sperm Maturity in Fertility and Embryo Development

The maturity of spermatozoa is yet another concept that has been linked to the fertility and embryo development. In this study, one of the questions is how sperm maturity influences fertility. This question is critical in addressing the issue of infertility since it informs the sexual behaviours, especially frequencies that lead to increased fertility. 17-22 For instance, a study on assisted reproduction technique revealed the problems associated with immature sperm cells, where the cells are unable to swim naturally to facilitate fertilization.17 According to Machtinger, Laurent,and Baccarelli 18, post-testicular sperm maturation processes such as sperm motility acquisition and the reduction of the oxidative stress are critical in facilitating the movement and fertilization. Similarly, Sellami et al. 21 revealed a strong correlation between sperm immaturity and acrosome abnormalities. Gil-Guzman et al. 23 provided an interesting explanation as to how immaturity leads to infertility. The study showed that the production of Reactive Oxygen Species (ROS), which usually mediates damage to human spermatozoa, was highest in immature spermatozoa. The immature spermatozoa were characterized by abnormal head morphology. 23

DISCUSSION

Summary of Evidence

Sperm Chromatin in Fertility and Embryo Development

The current semen screening methods such as sperm concentration, motility, and morphology do not identify any defects in sperm chromatin structure. 5-17 Also, the study by Shamsi, Kumar, and Dada8 revealed that the conventional parameters of semen analysis are insufficient for the evaluation of the reproductive potential. This limitation provides a clear picture of the role of sperm chromatin in embryo development. One common agreement in most of the studies reviewed was that sperm chromatin plays a major role in the transmission of genetic information.2, 5, 6, 9-15 Therefore, the sperm chromatin influences embryo development depending on the paternal genetic information transferred.6, 9

Sperm Maturity in Fertility and Embryo Development

The second question is how the maturity of the spermatozoa influences the development of the embryo. The review of literature revealed that poor quality and immature sperms is linked to delayed pronuclear formation and sluggish embryonic development.17-28 This is informed by the revelation that the sperm is involved in embryonic quality and development. The studies also showed that poor maturity and integrity of the sperm chromatin adversely affects the development of the zygote. 20. For instance, the study by Asmarinahet al. 20 revealed how low sperm chromatin maturity at the level of <87% correlated significantly with the cleavage rate of the zygote.

Limitations

Several limitations associated with the systematic review study approach were evident. Firstly, the study focused on a shallow assessment and interpretation of the findings from each individual study rather than a detailed analysis of the study effects. Secondly, other factors and study environment were ignored. For instance, the characteristic of the subjects involved of the study such as whether they have infertility problems was not part of the assessment. Therefore, the conclusion below is limited to just the comparison of the findings regarding the relationship between the independent and dependent variables. Thirdly, the parameters used by the various researchers were not different. Therefore, it was impossible to use meta-analysis that could give a platform for statistical analysis of the data.

Conclusions

The systematic review provided crucial insights regarding the role of sperm chromatin and sperm maturity in fertility and embryo development. As Agarwal and Said 2 noted, the sperm DNA integrity is critical in assessing the accurate transmission of the genetic information. This revelation is critical today due to the nature of screening methods used in determining the fertility and embryo development. For example, a comparison of the studies showed that semen screening methods such as sperm concentration, motility, and morphology do not identify any defects in sperm chromatin structure. Therefore, these approaches are lacking since they do not assess spe...