Cláudia Alves

University of Porto, Oporto, Porto, Portugal

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Publications (11)33.32 Total impact

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    ABSTRACT: In vitro culturing of normal human seminiferous epithelium remains largely unexplored. To study normal human spermatogenesis in vitro, we used a micromethod for the purification and culture of Sertoli cells, spermatogonia A, spermatocytes, and early round spermatids. Cytological quantitative data for Sertoli and premeiotic germ cell cocultures isolated from normal testicular biopsies demonstrated that cells were able to proliferate (4%), complete meiosis (6.7%), and differentiate into late round (54%), elongating (49%), and elongated (17%) spermatids at similar in vivo time delays (up to 16 days) in response to FSH + testosterone stimulation. Cells maintained normal meiotic segregation, chromosome complements, and specific gene expression profiles. Follicle-stimulating hormone + testosterone stimulated spermatogonia proliferation and Sertoli cell survival. Follicle-stimulating hormone and especially FSH + testosterone increased diploid germ cell survival during the first week, whereas only FSH + testosterone was able to inhibit cell death during the second week of culture. Follicle-stimulating hormone and especially FSH + testosterone also stimulated meiosis resumption, although this was restricted to late pachytene and secondary spermatocytes. In contrast, spermiogenesis was only stimulated by FSH + testosterone. Expression studies showed that apoptosis was induced in the nucleus of diploid cells, and in nuclear and cytoplasmic compartments of spermatids, mainly triggered by the Fas pathway. Although junctional complexes between Sertoli and premeiotic germ cells were partially reacquired, the same did not apply to spermatids, suggesting that FSH potentiated by testosterone was unable to render Sertoli cells competent to bind round spermatids.
    Biology of Reproduction 08/2008; 79(5):962-75. DOI:10.1095/biolreprod.107.067546 · 3.32 Impact Factor
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    ABSTRACT: Haploidization is the artificial induction of meiosis in somatic cells. This new technology has been developed to offer infertile patients an alternative to gamete donation by means of the artificial construction of patient gametes. It is intended to be used by the infertile patients with absent gonads, or with gonadal dysfunction that prevents the formation of mature gametes or whose gametes present severe structural⧸genetic abnormalities. We made a complete bibliography review and present our experimental data. In this technology, donor oocytes are first enucleated and then nuclear transfer is performed using G1⧸G0 adult diploid somatic cells of the patient. Avoiding cytokinesis inhibition (as used in cloning), constructs are then activated for the induction of a premature chromosome division. This is expected as the genetic material has been induced to prematurely condense by exposure to activated MPF present in the ooplasm. Although promising, this technology still allows a low rate (9%) of induced meiosis with a correct chromosome segregation.
    Revista Internacional de Andrología 03/2006; 4(1). DOI:10.1016/S1698-031X(06)73562-2 · 0.23 Impact Factor
  • C Alves · M Sousa · C Almeida · J Silva · A Barros ·

    Reproductive biomedicine online 12/2005; 10:16. DOI:10.1016/S1472-6483(11)60270-8 · 3.02 Impact Factor
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    ABSTRACT: About one third of non-obstructive azoospermic cases are due to maturation arrest (MA). The question of why some cases have a few germ cells that escape the meiotic block and form spermatozoa (incomplete MA) whereas others completely arrest at meiosis (complete MA) remains to be determined. In the present study we compared both situations through FISH analysis of sex (X, Y) and autosomal (7, 18) chromosomes in pure populations of stage-specific germ cells. Sertoli cells, primary spermatocytes, secondary spermatocytes, round spermatids and elongated spermatids were isolated by micromanipulation from fresh testicular biopsies of 7 patients with obstructive azoospermia (controls) and 20 patients with MA (9 complete MA, 11 incomplete MA). All the patients had normal secondary sexual development and karyotypes, and absence of endocrine disorders and Yq11.2 microdeletions. Incomplete MA was characterized by increased levels of aneuploidy in Sertoli cells, decreased homologue pairing at meiosis I and an increased incidence of aneuploidy in secondary spermatocytes, thus suggesting that it may be caused by deficiencies in synaptonemal complex assembly. In contrast, complete MA was associated with increased levels of aneuploidy in primary spermatocytes, arising during mitotic divisions of spermatogonia, and normal pairing, thus suggesting that meiotic arrest might be due to deficiencies in mismatch DNA repair.
    Revista Internacional de Andrología 06/2005; 3(2). DOI:10.1016/S1698-031X(05)74690-2 · 0.23 Impact Factor
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    ABSTRACT: A de novo reciprocal translocation 46,X,t(Y;1)(q12;q12) was found in an azoospermic male with meiotic arrest. Cytogenetics and fluorescent in situ hybridization (FISH) were used to define the karyotype, translocation breakpoints and homologue pairing. SRY (Yp), Yq11.2-AZF regions, DAZ gene copies and the distal Yq12 heterochromatin were studied by PCR and restriction analysis using sequence-tagged sites and single nucleotide variants. High resolution GTL, CBL and DA-DAPI staining revealed a (Y;1) translocation in all metaphases and a normal karyotype in the patient's father. FISH showed the presence of the distal Yq12 heterochromatic region in der(1) and loss of the heterochromatic region of chromosome 1. PCR demonstrated the intactness of the Y chromosome, including the SRY locus, AZF regions, DAZ genes and distal heterochromatin. A significant decrease (P = 0.005) of Xp/Yp pairing (18.6%), as compared with controls (65.7%), was found in arrested primary spermatocytes, and cell culture and mRNA expression studies confirmed an irreversible arrest at meiosis I, with induction of apoptosis and removal of germ cells by Sertoli cells. We characterized a de novo t(Y;1)(q12;q12) balanced reciprocal translocation with loss of the heterochromatic region of chromosome 1, that caused unpairing of sex chromosomes followed by meiosis I arrest, apoptotic degeneration of germ cells and azoospermia.
    Human Reproduction 04/2005; 20(3):689-96. DOI:10.1093/humrep/deh653 · 4.57 Impact Factor
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    ABSTRACT: Deletions of the AZFc region in Yq11.2, which include the DAZ gene family, are responsible for most cases of male infertility and were associated with severe oligozoospermia and also with a variable testicular pathology. To uncover the functional contribution of DAZ to human spermatogenesis, a DAZ gene copy-specific deletion analysis was previously established and showed that DAZ1/DAZ2 deletions associate with oligozoospermia. In this study we applied the same screening method to 50 control fertile males and 91 non-obstructive azoospermic males, 39 with Sertoli cell-only syndrome (SCOS) and 52 with meiotic arrest (MA). Samples were also screened with 24 sequence-tagged sites to the different AZF regions, including 114 control fertile males. After biopsy (testicular sperm extraction, TESE), residual spermiogenesis was found in 57.7% MA and 30.8% SCOS cases (incomplete syndromes). DAZ1/DAZ2 deletions were associated with the testicular phenotype of residual spermiogenesis as they were only found in two patients (8%) with incomplete MA. Differences between incomplete (23.3%) and complete (4.5%) MA cases regarding AZFc and DAZ1/DAZ2 deletion frequencies, and between incomplete (58.3%) and complete (11.1%) SCOS cases for AZFc deletions, suggest that incomplete syndromes might represent an aggravation of the oligozoospermic phenotype. As successful TESE was achieved in 87.5% of MA cases with AZFc and DAZ1/DAZ2 deletions and in 58.3% of SCOS cases with AZFc deletions, the present results also suggest that these molecular markers might be used for the establishment of a prognosis before TESE.
    Molecular Human Reproduction 11/2004; 10(10):755-61. DOI:10.1093/molehr/gah104 · 3.75 Impact Factor
  • C Alves · F Carvalho · M Sousa · J Silva · A Barros ·

    Reproductive biomedicine online 12/2002; 4:47. DOI:10.1016/S1472-6483(12)60100-X · 3.02 Impact Factor
  • C Alves · F Carvalho · M Sousa · N Cremades · A Barros ·

    Reproductive biomedicine online 12/2002; 4:45. DOI:10.1016/S1472-6483(12)60096-0 · 3.02 Impact Factor
  • Cláudia Alves · Mário Sousa · Joaquina Silva · Alberto Barros ·
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    ABSTRACT: Preimplantation genetic diagnosis (PGD) is an alternative to prenatal diagnosis for couples at risk of transmitting genetic disorders to their offspring. We present a fluorescence in situ hybridization (FISH) analysis of embryos obtained after seven PGD cycles in six couples with Robertsonian translocations and male factor infertility: 4 der(13;14), 1 der(14;21) and 1 der(15;21). Of 74 metaphase II (MII) injected oocytes, 61 (82.4%) fertilized normally and cleaved. Of these, 37/61 (60.7%) embryos were of high morphological quality with >or=6 blastomeres. After biopsy of 44 embryos at day 3 of development, seven degenerated, seven arrested in development and 30/44 (68.2%) evolved, of which 25/30 (83.3%) reached the morula/blastocyst stage. Analysis of biopsied blastomeres showed 23/44 (52.3%) of normal/balanced embryos, of which 15 (11 at the morula/blastocyst stage) were transferred in six cycles. One term pregnancy was achieved, which ended by cesarean section at 37 weeks of gestation, giving birth to two healthy newborn. Analysis of 49 embryos (excluding 12 inconclusive cases) showed a predominance of alternate segregation (38/49, 77.6%) over adjacent segregation (7/49, 14.3%), with one (2%) being a polyploid mosaic and three (6.1%) chaotic.
    Prenatal Diagnosis 12/2002; 22(12):1153-62. DOI:10.1002/pd.503 · 3.27 Impact Factor
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    ABSTRACT: The incidence of Y/autosome translocations is low. Whereas involvement of non-acrocentric chromosomes often leads to infertility, cases related with acrocentric chromosomes are usually familial with no or minimal effect on fertility. A de novo (Yp/13p) translocation was found in a 32-year-old male referred for severe oligozoospermia. Conventional cytogenetic procedures (GTG, CBG and NOR banding) and molecular cytogenetic techniques (Fluorescence In Situ Hybridization, FISH) were performed on high-resolution chromosomes obtained after peripheral blood lymphocyte culture as also on interphase nuclei of spermatogenic cells from semen samples. Screening of AZF microdeletions in the Yq11.2 region known to be involved with spermatogenesis defects was also performed. GTG banding showed a (Yp/13p) translocation in all scored metaphases. CBG and NOR staining of the derivative chromosome revealed the maintenance of Yq heterochromatin and of the 13p NOR region. FISH with centromeric Y and 13/21 probes, SRY specific probe and X/Y (p and q arms) sub-telomeric probes gave the expected number/location of fluorescent signals. Hybridisation with a pan-telomeric repeat (TTAGGG) probe showed an absence of the telomeric sequences at the fusion point of the rearranged chromosome. FISH analysis with probes to chromosomes X, Y, 13 and 18 showed an abnormal segregation of the translocated chromosome during meiosis I, which explains that only 13.6% of the secondary spermatocytes were normal. Most of these became arrested, as after meiosis II the large majority of the round spermatids were normal (70%), as were in consequence most of the sperm (85.1%). Multiplex-PCR confirmed the intactness of the SRY region and showed absence of AZF microdeletions. We report a novel de novo (Yp;13p) translocation characterised by loss of the 13p and Yp telomeres. Meiotic studies using FISH demonstrated meiosis I chromosome unpairing and mal segregation that justifies the severe oligozoospermia. Although most sperm have a normal chromosomal constitution, preimplantation genetic diagnosis should be considered an option for this patient.
    European Journal of HumanGenetics 09/2002; 10(8):467-74. DOI:10.1038/sj.ejhg.5200835 · 4.35 Impact Factor
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    ABSTRACT: Development of an in-vitro culture system capable of supporting human early germ cell differentiation would be important for treatment of azoospermic patients. Sertoli cells, spermatogonia and spermatocytes were isolated from testicular biopsies of 61 non-obstructive azoospermic patients, and co-cultured using Vero cell conditioned medium only or supplemented with recombinant (r)FSH or rFSH plus testosterone. Germ cell purity was checked by fluorescent in-situ hybridization (FISH) analysis. Best results were achieved with both hormones, which elicited 6.9% of meiosis index and 22.7% of differentiation into normal late spermatids after 2-3 weeks of culture. In-vitro matured spermatids were microinjected into oocytes to study their developmental potential. Round spermatids elicited 37.5% of fertilization and 28.6% blastocyst rates. Abnormal elongating and elongated spermatids enabled 8.3 and 27.3% fertilization rates respectively, but none achieved the blastocyst stage. Normal elongating and elongated spermatids elicited 30.5% fertilization and 42.9% of blastocyst rates. FISH analysis showed sex chromosome anomalies in all embryos, except in the case of morulae from normal late spermatids. Results suggest that meiosis and spermiogenesis can be resumed in vitro, with normal differentiated spermatids showing a low fertilization potential but regular rates of blastocyst formation. However, most of the embryos did not reach the morula stage and showed major sex chromosome abnormalities.
    Human Reproduction 02/2002; 17(1):161-72. DOI:10.1093/humrep/17.1.161 · 4.57 Impact Factor