Role of Mitochondria in Repeated Pregnancy Loss (Pages: 0-0)


Seyedhassani S.M *, Hushmand M , Kalantar S.M , Hashemi gorji F , Aflatunian A ,

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Objectives: Pregnancy loss is the most common complication of pregnancy. About 1 in 300 couples involve with Repeated Pregnancy Loss ( RPL ) and the main part of them remains unknown. Apoptosis plays a role in early human development and embryonic loss.The aberrant expression of apoptotic related genes is seen in RPL. It seems internal apoptotic pathway and mitochondria as a main core of it, have important role in fertilization and proliferation of the cells. Mitochondrial DNA (mtDNA) is not transmitted through nuclear DNA (nDNA), and in most multicellular organisms, virtually all mitochondria are inherited from the mother's ovum, as it is unusual for sperm cells to contribute mitochondria when fertilizing ova. Bax is an important nuclear gene in mitochondrial pathway of apoptosis.The protein encoded by this gene belongs to the BCL2 protein family. This protein forms a heterodimer with BCL2, and functions as an apoptotic activator. We believe that the mitochondria, Bax and Bcl2 genes are good candidate for investigation of pregnancy loss . Materials and Methods: 335 consecutive cases were studied. Genetic counseling, clinical, paraclinical, and cytogenetic studies were done for each couple. We analyzed the familial pedigree of them and then screened the idiopathic cases. In total 96 females who were suffered from idiopathic RPL. 1- Four multiplex PCR are done on each sample for detection of mitochondrial deletions. 2- Mitochondrial D-loop part consisting of the hyper variable regions is analyzed by PCR-sequencing method. 3- Bax gene is evaluated by PCR-sequencing method for promoter region and all seven exons. 4- Bcl2 gene is evaluated by PCR-sequencing method for promoter region and PCR-SSCP for the exons. Results: 1- No mitochondrial deletions were found in 96 DNA samples. 2- Mononucleotide repeat (poly C) from 303 to 315 nucleotide positions (D310) exhibited a polymorphic length variation and mutations (C ins. in 37,CC ins. in 8 ,CCC ins. in 1,T-CCC in 1 , T-CCCC in 1, and T-CCCCC in 1 female) 3- D-loop region was evaluated by direct sequencing and we found 166 different variations in our study population. Among them, 95 variations were seen in RPL cases , 28 in control samples , and also 43 in both of them . 4- Change of A to G in promoter region of Bax gene was seen at nt. -55 in 93 females (96.87%) . Conclusion: 1- Because of oxidative stress is one of the important cause of mtDNA deletions we suggest that this phenomenon seems is less involving in pregnancy loss. 2- Some of these nucleotide alterations might be involved in repeated pregnancy loss and could be included in a panel of molecular biomarkers for susceptibility in pregnancy loss and even failure of in-vitro fertilization. 3- A high rate of mutation in mitochondrial DNA in the D loop was found in samples from patients with RPL relative to healthy controls . 4- In seven SNPs that were found in case and control groups, we found significant difference between groups (P