@2024 Afarand., IRAN

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ISSN: 2251-8215    Sarem Journal of Reproductive Medicine 2018;2(2):45-50

Background
At least 15% of diagnosed pregnancies leads to spontaneous abortion and recurrent abortions occur in ‎about 1% of all pregnancies. Unusual chromosomal structures are the only common symptom for the ‎loss of pregnancy that is due to the end of a pregnancy before the 20th gestational week. ‎
Previous Studies
The prevalence of chromosomal abnormalities in the first trimester of pregnancy is more than 50%. In ‎cases where there are at least two abortions, the probability that one of the couples have a moderate ‎chromosomal abnormality is 7% [1] and the probability of abortion is 25-50% in these cases [2, 3]. ‎The extent of moderate chromosomal abnormalities in the standard examination of this group of ‎patients should include the karyotype of both parents for chromosomal abnormalities [4]. The risks of ‎the resulting cases depend on the chromosomal rearrangement of the type of novelty and whether the ‎male or female parent is carrier. Visible chromosomal reversals which are observable under the ‎optical microscope are a common group of balanced structural rearrangements. In reversals, a piece of ‎a chromosome turns off 180 degrees after being disconnected from the chromosome and then restored. ‎For reversal, the chromosome must be broken at two points. If the broken part contains the ‎centromere, the type of revision is pericentric. The second reversal mode occurs when the broken part ‎does not contain a centromere and only contains one arm of the chromosome, that in this case the ‎reversal type is paracentric. Increase and decrease of the genetic material is an unbalanced abnormality ‎structure. However, in the reversion, the genetic material is not increased or decreased and it is ‎considered to be a structural malformation, and only the order of the genes changes. Reversals often ‎have no phenotypic effects, however, failure may occur within a gene, and part of it goes to another ‎location and the entire gene action is degraded. Another phenotypic effect is that the location and ‎position of the gene through reversal may have an effect on the expression and effect of the gene and ‎has a spatial effect [5]. ... [5-7].‎
Aim(s)
The aim of this study was to evaluate the prevalence of pericentric and paracentric chromosomal ‎reversal in patients with abortion history.‎
Research type
This is a descriptive study.‎
Research society, place and time
In this study, couples who had referred to the cytogenetic lab of Sarem Hospital in Tehran from 2006 to ‎‎2014 due to a history of one abortion or more were studied.
Sampling method and number
‎2299 couples were examined. The incidence of abortion in these women was between the ages of 16 ‎and 57.‎
Used devices&materials
The structure of all 44 autosomal chromosomes and 2 sexual chromosomes was investigated. ‎Chromosomal study was performed using T lymphocytes and standard cytogenetic methods. The specimens were studied using GTG banding method with high distinction power. In this method, ‎the cell cycle stops in step S using thymidine and the chromosomes are collected for a short time in the ‎pro-metaphase or early metaphase stage using calcimid. As a result, longer chromosomes with high ‎resolution spanning stains (bph 850-500) can be obtained and chromosomal abnormalities can be ‎detected with high precision. At first, 5 ml of patient's blood sample was prepared using a syringe with ‎‎100 μL antidiabetic heparin sodium hydrate with a concentration of 5000 IU / cc and without any ‎preservative. The amount of 0.4 cc of blood was poured into 4 cc of complete RPMI-1640 medium at ‎pH = 7, and one cc of FBS and 125 micro liter of phytohaemagglutinin and 1% of penicillin or ‎streptomycin were added. The contents of the culture tube were shaken for a few times and then placed ‎in a 37 ° C incubator at 30 degrees. After 48 hours, 100 μl of thymidine was added to the culture ‎medium and placed in a 37 ° C incubator for 16 to 17 hours. Then, the tubes were centrifuged for 8 ‎minutes and the supernatant was discarded, and after mixing the precipitate, 5 cc of complete culture ‎medium without PHA was added. Subsequently, the contents of the tubes were mixed and placed in a ‎‎37 ° C incubator for 4 hours and 45 minutes. Then, 100 μl of calcimid was added to the tubes and ‎placed in an incubator for 15 minutes. Finally, the cultured samples were harvested, placed on the ‎slides, strained and analyzed using GTG standard bonding method [8]. In this method, the slides are ‎placed in an incubator at 37 ° C for a week or at 70 ° C for one day. Then, the slides were placed in ‎‎0.05% trypsin at room temperature for 10 to 60 seconds, and they were washed into the physiologic ‎serum containing 1% FBS serum and then stained with Giemsa. For each patient, at least 15 samples ‎were examined in the metaphase step and 5 metaphases were used to determine the structural ‎abnormalities according to the International Cytogenetic Naming System (ISCN 2013) [8]. C banding method was used to investigate more on pericentric percentile reversals of heterochromatin ‎region of chromosome 9. The method of this method is to detect long chromosome homochromatic ‎regions of Y, 1, 9 and 16 chromosomes and to detect the heterochromatin nature of some chromosomal ‎markers. In the c-banding method, the slides were first placed in a HCl solution at a concentration of ‎‎0.2 M at room temperature for 15 to 20 minutes, then they washed with distilled water. Following that ‎the slides were then placed in Ba (OH) 2 saturated solution at room temperature for 10 to 15 minutes ‎and washed with distilled water. Then they were placed in a XSSC2 solution at 60 ° C for 2 to 3 hours. ‎Slides were then stained for 10-15 minutes with 5% Giemsa solution and were placed on the slides ‎using anthelion or DPX adhesive (8). The study of metaphases in C-banding was performed by ‎recognizing the areas of centromere and heterochromatin regions in Y, 1, and 9 chromosomes.‎
Findings by Text
In total, 49 (2.1%) patients had chromosomal reversal (Table 1). A reversal was observed around the ‎chromosome 9 centromere in 37 (1.6%) patients.‎There were 29 cases of pericentric reversal of chromosome 9 in the region (p11.2q13) including 15 ‎women and 14 males, which contained 26.1% of total cases (Figures 1 and 2).‎Reversal was observed around centromere in chromosome 9 in two patients with chromosomal ‎displacement in form of 46, XY, t (11.18) (p15.1; q23), inv (9) (p11.2q13), as well as 46, XY, t (12 ; 14) ‎‎(p11.21q21), inv (9) (p11.2q13), and in another patient with Robertsonin displacement of ‎chromosomes 13 and 14, whose karyotype was 45, XY, der (13; 14) (q10q10) , inv (9) (p11.2q13). In a ‎patient, the reversal of chromosome 9 was in the region (p11.2q13) with a paracentric reversal of ‎chromosome 3, whose karyotype was 46, XY, inv (3) (p23p26), inv (9) (p11.2q13). Pericentric ‎reversal of chromosome 9 was also observed in the region (p11q21.1) in 3 patients. There was a reversal in the heterochromatin region of chromosome 1 and in Y chromosome, each of ‎which was observed in one patient. The reversal of chromosome 2 was obtained between the points 2 ‎‎/ p11 and q13 in one patient. Chromosomal reversals that was observed in other chromosomes as well ‎as in non-heterochromatin regions were pericenteric in chromosomes 1, 5, 8, 11 and 12 (Figures.1 and ‎‎3) and in paracentric in chromosomes 3, 6, 7, 8, and 12 (Figure 4).‎
Main comparison to the similar studies
In this study, the total rate of pericentric reversal in chromosome 9 was 1.6%. The precentric reversal ‎of chromosome 9 or inv (9) usually accounts for 1 to 2% of the population [9]. Previous research ‎findings have reported the reversal of chromosome 9 at points (p11.2q13) / (p11q21) in 27.2% of ‎patients with a history of recurrent abortions [1].‎ Knowing that the observed reversal is belonged to which categories of reversal is very important [10]. ‎Reversible carriers may have the risk of removing or rearrangement of chromosomes during meiosis. ‎The results of paracentric reversals are detrimental [11].‎ Pericentric reversal carriers also have high risk of abortion. Crossing‏ ‏over results in a‏ ‏pericentric ‎reversal loop may be the removal or duplication of a chromosomal fragment. The size of the genetic ‎material obtained or lost depends on the length of the broken part [4]. ... The results of several studies ‎have shown that if a person is a carrier of balanced pericentric reversal, and that this reversal has ‎previously led to the birth of an abnormal child, the risk of having an unbalanced baby is ‎approximately 5-10% for that person. If the reversal is proven by repeated abortion, this risk would be ‎close to 1% [12].‎
Suggestions
Chromosomal reversal in the patient can lead to abortion or childbirth with abnormalities. Therefore, ‎performing karyotype as a gold diagnostic test is necessary for patients with a history of abortion or ‎abnormal child birth.‎
Limitations

Conclusions
The prevalence of pericentric and paracentric chromosomal reversals in patients with abortion history ‎is 2.1%. Also, the pericentric reversal rate of chromosome 9 in the regions of p11.2q13 is 1.26%, ‎which is similar to the prevalence in the natural population and therefore cannot be the cause of ‎abortion.‎
Acknowledgments
The efforts of our dear Dr. Saremi, the deputy chairman of the Sarem Specialized Hospital, all the ‎doctors who participated in the referral of patients and all patients and their families, as well as the ‎assistance of the staff of the hospital's cytogenetic laboratory, especially Shahnaz Ghalabeygi, Fatemeh ‎Moghaddasi and Roghieh Vahedi, are appreciated. ‎
Conflict of interest

Ethical Permissions

Funding Sources

TABLES and CHARTS

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