Relationship of DNA damage and embryotoxicity induced by 4-hydroperoxydechlorocyclophosphamide in postimplantation rat embryos

Modelling the equilibrium partitioning of low concentrations of airborne volatile organic compounds in human IVF laboratories

RESEARCH QUESTION

Can volatile organic compounds (VOC) be modelled in an IVF clinical setting?

DESIGN

The study performed equilibrium modelling of low concentrations of airborne VOC partitioning from the air phase into the oil cover layer into the water-based culture media and into/onto the embryo (air-oil-water-embryo). The air-phase VOC were modelled based on reported VOC concentrations found in modern assisted reproductive technology (ART) suites, older IVF clinics, and hospitals, as well as at 10 parts per billion (ppb) and 100 ppb for all compounds. The modelling was performed with 23 documented healthcare-specific VOC.

RESULTS

Based on the partitioning model, seven compounds (acrolein, formaldehyde, phenol, toluene, acetaldehyde, ethanol and isopropanol) should be of great concern to the embryologist and clinician. Acrolein, formaldehyde, phenol, toluene and acetaldehyde are the VOC with the most potent cytotoxic factor and the highest toxic VOC concentration in media. In addition, ethanol and isopropanol are routinely found in the greatest air-phase concentrations and modelled to have the highest water-based culture concentrations.

CONCLUSIONS

The results of the equilibrium partitioning modelling of VOC provides a fundamental understanding of how airborne VOC partition from the air phase and negatively influence human IVF outcomes. The results presented here are based on the theoretical model and the values presented have not yet been measured in a laboratory or clinical setting. High air-phase concentrations and toxic concentrations of VOC in culture media are likely indicators of poor clinical outcomes. Based on this model, improved air quality in IVF laboratories reduces the chemical burden imparted on embryos, which supports findings of improved IVF outcomes with reduced air-phase VOC concentrations.

[Impact of air quality on practices and results in the IVF laboratory]

The concept of Air Quality often refers to particulate and microbiological contamination of ambiant air. European Directive 2006/86/CE encompass the IVF process and specify a class A air quality for manipulation of tissue and cells, in a class D environment (A over D rule). Recognizing the paramount importance of ensuring the highest microbiological and particulate safety in the IVF laboratory, it is equally important to take into account practicability issues and the financial burden of these recommendations, as well as the utter need to protect gametes and embryo viability during their IVF journey. The usefulness of such stringent recommendations may also be questionned given the absence of published cases of airborne contaminations and related patients infections after embryo transfer. The European directive stems from pharmaceutical standards and were not specifically designed for human IVF. Gametes and embryos are indeed extremely sensitive to physical and chemical stress and require strict temperature, osmolarity and pH control, as well as an absence of chemical contamination during manipulation and culture. These conditions are hardly obtained when using laminar flow hoods. Following concerns raised by many experts in the field, exceptions to the A over D rule were added in the 2006/86/CE Directives. This narrative review discusses all these aspects in a critical way and compare scientific and legal requirements applying to IVF practices in different regions of the world.

Air quality control in the ART laboratory is a major determinant of IVF success

A recently published article described how a fertility center in the United States implemented air quality control to newly designed in vitro fertilization (IVF) laboratory.1 A highly-efficient air filtration was achieved by installing a centered system supplying filtered air to the IVF laboratory and related critical areas, combining air particulate and volatile organic compound (VOC) filtration. As a consequence, live birth rates were increased by improvements in air quality. This article highlights the key aspects of air contamination in the IVF context. The topic is important not only to IVF specialists but also to Andrologists due to the great number of male infertility patients referred to assisted reproductive technology (ART) treatments. The evidence is growing that laboratory air quality is paramount importance for improved IVF outcome.

Better IVF outcomes following improvements in laboratory air quality

BACKGROUND

It has been proved that air quality is crucial for the success of IVF because of the presence of volatile organic compounds (VOCs), microbes, and perfumes, all of which can be harmful to embryo development in vitro. Therefore IVF laboratories are equipped with high efficiency particulate air (HEPA), and activated carbon filters plus positive pressure for air particulate control, with or without CODA system. Here we introduce a new technology using specially treated Honeycomb matrix media aligned in the Landson ™ series system for our laboratory air purification and its impact on IVF outcome.

METHODS

Air samples were collected outside and inside the laboratory, and intra-incubator at three different time points, before and after changing carbon filters and after Landson system installation, and we correlated air compounds measure variation with IVF outcome from 1403 cycles.

RESULTS

An improvement of air quality was confirmed with passages of total VOCs from 0.42 mg/m(3), 30.48 mg/m(3), 9.62 mg/m3, to 0.1 mg/m(3), 2.5 mg/m(3), 2.19 mg/m(3) through 0.07 mg/m(3), 0.16 mg/m(3), 0.29 mg/m(3), outside the laboratory, inside laboratory and intra-incubator respectively at three separated air sampling times. A clear decrease was observed in some VOCs such as formaldehyde, ethylene, acethylene, propylene, SO2, pentane, NOx, benzene, Hallon-1211, CFC and alcohol. At the same time a significant difference (P<0.05) was found between the third testing time TT3 after carbon filter change and Landson system installation and the first testing time TT1 before carbon filter change in fertilization rate 83.7 % vs 70.1 %, embryo cleavage rate 97.35 % vs 90.8 %, day 5 blastocyst formation rate 51.1 % vs 41.7 %, and pregnancy/implantation rates 54.6 %, 34.4 % vs 40.6 %, 26.4 %.

CONCLUSION

Air purification by the new technology of Landson ™ series significantly improved IVF laboratory air quality, and embryo quality, thus increased pregnancy and implantation rates.

Detection of the embryotoxic potential of cyclophosphamide by using a combined system of metabolic competent cells and embryonic stem cells

In order to develop a method for detecting metabolism-mediated embryotoxicity, differentiating embryonic stem (ES) cells were exposed to the well-known proteratogen, cyclophosphamide (CPA). CPA was tested in a scientifically validated embryonic stem-cell test (EST), and in the newly developed reporter-gene assay for developmental cardiotoxicity. Both assays gave false-negative results. Because no metabolic competence (cytochrome P450 [CYP] activity) was found in the ES cells under the selected culture conditions, a simple biotransformation system was combined with the reporter-gene assay. As the metabolic pathway of CPA is well characterised, the genetically engineered mammalian cell line V79, transfected with CYP2B1 cDNA, was selected as a biotransformation system. CYP2B1 is responsible for transforming CPA into teratogenically active metabolites. The supernatants of genetically engineered V79 cells were analysed in the reporter-gene assay for developmental cardiotoxicity. In preliminary experiments, the combined system was able to detect the embryotoxic potential of the proteratogen, CPA.

Spatial glutathione and cysteine distribution and chemical modulation in the early organogenesis-stage rat conceptus in utero

Glutathione (GSH), cysteine, and other low-molecular-weight thiols (LMWT) play a vital role in the detoxication of xenobiotics and endogenous chemicals. Differential alterations of LMWT status in various cell types of the developing embryo may underlie cell-specific sensitivity or resistance to xenobiotics and contribute to embryotoxicity. This study describes the spatial and temporal distribution of LMWTs in rat conceptuses and alterations produced by the non-teratogenic GSH modulator, acetaminophen (APAP). Pregnant female rats were given 125, 250, or 500 mg/kg APAP (po) on gestational day 9. Conceptal LMWT was localized histochemically using mercury orange in cryosections, and GSH and cysteine concentrations were measured by HPLC analysis. Mercury orange histofluorescence revealed a non-uniform distribution of LMWT in untreated conceptal tissues, with strongest staining observed in the ectoplacental cone (EPC), visceral yolk sac (VYS), and embryonic heart. Less intense staining was observed in the neuroepithelium. Following treatment with APAP, tissue-associated LMWT decreased dramatically except in the EPC, while exocoelomic fluid LMWT, and LMWT within embryonic lumens, increased. Exposure to 250 mg/kg APAP decreased embryonic GSH after 6 and 24 h by 46% and 38%, respectively. Acetaminophen (500 mg/kg) decreased embryonic and VYS cysteine content by 54% and 83%, respectively, after 24 h. Acetaminophen alters the spatial distribution of LMWT in rat conceptuses, particularly with respect to cysteine. The mobilization of cysteine following chemical insult may influence the ability of conceptal cells to maintain normal GSH status due to reduced availability of cysteine for de novo GSH synthesis.

Teratogen-induced activation of ERK, JNK, and p38 MAP kinases in early postimplantation murine embryos

BACKGROUND

Although many teratogens are known to activate apoptotic pathways culminating in abnormal development, little is known about how the embryo transduces a teratogenic exposure into specific responses. Signal reception and transduction are regulated by a number of signal transduction pathways, including the extracellular signal-regulated protein kinases (ERKs), c-Jun N-terminal kinases (JNKs) and the stress-activated protein kinase, p38.

METHODS

To analyze the effects of teratogens on MAP kinases, we used whole embryo culture, Western blot analyses, and antibodies recognizing inactive or active MAP kinases, or both.

RESULTS

We show that heat shock (HS) induces a rapid, strong, but transient activation of ERK, JNK, and p38 with maximal activation occurring within 30 min of the heat shock. By contrast, cyclophosphamide (CP) and staurosporine (ST) failed to activate ERK or JNK during the time period studied (7. 5 hr). ST and CP did induce a low but reproducible activation of p38 beginning at around 3 hr and 5 hr, respectively, after the initiation of exposure. Previous work has shown that heat shock induces elevated cell death in the embryo, primarily in the developing neuroepithelium, but not in the embryonic heart. Thus, we also compared the activation of these three MAP kinase pathways in heads, hearts, and trunks isolated from day 9 embryos exposed to 43 degrees C for 15 min. The results show that ERK, JNK, and p38 are activated in heads, hearts, and trunks.

CONCLUSIONS

Our results show that day 9 embryos do activate MAP kinase signaling pathways in response to teratogenic exposures; however, activation of a particular pathway does not appear to be required for teratogen-induced apoptosis.

Cyclophosphamide-induced teratogenesis in ICR mice: the role of apoptosis

It is known that programmed cell death (apoptosis) is an important physiological determinant of embryonic development. In parallel, it may be one of the major events involved in induced teratogenesis. The present study was designated to evaluate to what extent is apoptosis involved in the formation of some final abnormalities induced by cyclophosphamide (CP) in ICR mice. The level of apoptosis in limbs, tail, liver, and whole embryo was assessed 24 h after administration of various doses of CP (day 12 of pregnancy) by flow cytometric analysis and by DNA fragmentation assay. In parallel, the rate of limb and tail malformations, resorptions, and growth retardation induced by various doses of CP was evaluated in animals sacrificed on day 19 of pregnancy using routine teratological methods. A striking correlation between the rate of CP-induced apoptosis in limb and tail cells and the severity of limb and tail anomalies was found after administration of CP ranging from 10 to 40 mg/kg. Thus, the percent of apoptotic cells collected from limbs and tails increased from 18 to 78%. In parallel, the severity of limb and tail anomalies increased from digit anomalies to amely and from crooked to short or absent tail. CP-induced embryolethality and fetal growth retardation also correlated with the level of apoptosis in cells collected from whole embryos but to a lesser extent. These results claim that CP-induced apoptosis is one of the inevitable events in the pathway leading to the formation of CP-induced abnormalities and also suggest that the extent of the involvement of apoptosis in the formation of different types of final abnormalities, may be different.

Role of apoptosis in mediating phosphoramide mustard-induced rat embryo malformations in vitro

Phosphoramide mustard, an active metabolite of the anticancer drug cyclophosphamide, causes malformations in rat embryos undergoing organogenesis in vitro. The purpose of the present study was to investigate the hypothesis that apoptosis plays an important role in mediating the teratogenicity of phosphoramide mustard. Apoptosis is a process of active or programmed cell death which is characterized by internucleosomal DNA fragmentation and de novo RNA and protein synthesis. Sulphated glycoprotein-2 (SGP-2) or clusterin is induced in some models of apoptosis and is one of the proteins likely to be involved in the maintenance of cell integrity. In the present study, day 10 rat embryos were cultured for 6, 12, 24, and 45 hr, with or without the addition of 10 microM phosphoramide mustard. After culture for 24 or 45 hr with exposure to 10 microM phosphoramide mustard, the embryos were both growth-retarded and malformed. Exposure to phosphoramide mustard for 6 or 12 hr did not significantly alter the relative amounts of either the mRNA or protein for SGP-2; this treatment also had no effect on DNA fragmentation in embryos or their yolk sacs. After 24 hr in culture, the relative amounts of SGP-2 protein, but not mRNA, were increased 2-fold in the yolk sacs of the phosphoramide mustard-exposed embryos, but not in the embryos themselves. At this time, DNA fragmentation was detected in phosphoramide mustard-exposed embryos, but not in their yolk sacs or in control embryos. After 45 hr in culture, SGP-2 protein and mRNA levels were increased 2-4-fold above the controls in the phosphoramide mustard-exposed embryos and their yolk sacs. Immunohistochemical analysis revealed that in control embryos cultured for 45 hr, the SGP-2 reaction product was localized in the heart, hindgut, and yolk sac. In contrast, in phosphoramide mustard-treated embryos cultured for 45 hr, SGP-2 immunostaining was found throughout the embryo, with a strong immunoreaction in the mesenchyme and ectoplacental cone. DNA fragmentation in the embryos exposed to phosphoramide mustard for 45 hr was more extensive than that found after 24 hr, but fragmentation was still not detected in the yolk sac. Thus exposure in vitro to a teratogenic concentration of phosphoramide mustard resulted in DNA fragmentation and an increased expression of SGP-2 in the embryo. These data suggest that apoptosis is involved in mediating the teratogenicity of phosphoramide mustard.

In vitro approaches to the elucidation of mechanisms of chemical teratogenesis

This article describes some of the contributions that in vitro methods have made to our progress, albeit slow, toward understanding mechanisms of chemical teratogenesis. Emphasis is given to the painstaking and time consuming nature of approaches required to elucidate mechanisms. The examples considered are cyclophosphamide, 2-methoxyethanol, and retinoids. Some of the newer methods that take advantage of the recent advances in molecular biology and analytical chemistry have already been applied to studies on teratogenic mechanisms. Prospects for the 1990s are excellent and promise more rapid progress than during the past decade toward unraveling the mysteries of normal developmental biology. That knowledge in turn should be immediately applicable for investigations on developmental toxicant-induced abnormal development.

Effects of 4-hydroperoxycyclophosphamide (4-OOH-CP) and 4-hydroperoxydechlorocyclophosphamide (4-OOH-deCICP) on the cell cycle of post implantation rat embryos

In this study, we used preactivated forms of cyclophosphamide (CP) and dechlorocyclophosphamide (deClCP) to examine the effects of phosphoramide mustard (PM) and acrolein, respectively, on the cell cycle of postimplantation rat embryos. The percentage distribution of cells in the G1/G0, S, and G2/M phases of the cell cycle was determined by flow-cytometric analysis. At embryotoxic concentrations, 4-OOH-CP (PM) induced major cell cycle perturbations whereas 4-OOH-deClCP (acrolein) caused no major perturbation of the cell cycle. These data support the hypothesis that the mechanism of the embryotoxic action of PM involves alkylation of DNA, whereas the mechanism of action of acrolein does not. The primary effect of PM on the cell cycle was an initial delay in the S phase followed by a G2/M arrest. At low embryotoxic concentrations of 4-OOH-CP, there was apparent reversal of the G2/M arrest; at higher embryotoxic concentrations there was little recovery from the G2/M arrest. The high level of cell death found at higher drug concentrations suggests that prolonged G2/M arrest leads to cell death. Using radiolabeled CP and cell sorting, it was determined that PM predominantly alkylated DNA in the S phase of the cell cycle. Overall, the data from this study support the hypothesis that DNA cross-links, induced by the alkylation of DNA by PM, induce cell cycle perturbations. Furthermore, these cell cycle alterations may be one of the early steps in the mechanism leading to the embryotoxicity of PM.