Concepts in Preterm Birth Research: Interview with a Stakeholder

Preterm birth continues to be a clinical problem of vast significance all over the world [1, 2]. The complexities of the biology of preterm birth suggest a syndrome with multiple mechanisms leading to uterine contraction, cervical dilation and rupture of membranes. Multiple genetic, environmental, and basic biological factors are associated with preterm birth. Despite many years of effort, we still do not completely understand preterm birth, the basic mechanisms underlying parturition, or the relationship(s) between the two. My position has always been that breakthroughs in this area will come from an inclusive, integrative, and interdisciplinary approach that hears the voices of multiple stakeholders, encompasses “outside the box” thinking and utilizes novel methodologies. To document the voices of stakeholders, alternative thinking and the seeds of development of novel methodologies, I have begun to interview stakeholders in preterm birth. This is an interview with Ramkumar Menon, MS, PhD, Department of Obstetrics and Gynecology, Division of Maternal-Fetal Medicine & Perinatal Research, The University of Texas Medical Branch at Galveston. Dr. Menon is past president and current Executive Director of PREBIC Global. He has fought against increasing odds from all areas to not only produce outstanding science from his own laboratory, but also to bring together collaborators and support from all over the world to bear upon the problem of preterm birth. What follows is an interview I did with him in 2014.

EB: I am interested in the idea of the pre-pregnancy phenotype that indicates risk for preterm birth. It would be important to understand this before a woman’s first pregnancy. Phenotype in this sense means an expression of not only genotype, but also environment and specific exposures. Knowledge of this phenotype could alter management (placement in a high-risk clinic, drugs, diet etc.), or alter treatment upon the onset of preterm labor. Does this make sense to you?

Dr. Menon: Absolutely. I have put forth a model that incorporates the many layers of complexity in preterm birth[3]. Starting from the pre-pregnancy period, there are static components of the risk of preterm birth. These include race, nutritional and behavioral habits and BMI (Body Mass Index). As for environment, 100 or more different ways define this factor, each affecting the risk of preterm birth for every pregnancy a woman has.

EB: When does the risk for preterm birth occur (i.e. when should we look for the expression of this phenotype and try to modulate its expression)?

Dr. Menon: Start as early as possible. If you start to look at pregnancy, start looking at day 1, not just 16–18 weeks, which is common in the literature. If for example there is a behavioral risk or exposure, such as smoking, bacterial vaginosis, or psychosocial stress, this could affect oxidative stress and inflammation in the uterus well before implantation and the development of the fetus, placenta and fetal membranes. The damage to the uterus could affect feto-placental development and determine the outcome of preterm birth. Many risks that a pregnant subject encounters at later stages of gestation (e.g. infection) are likely secondary to an underlying structural or mechanical defect due to a risk the mother has been exposed prior to conception[3].

EB: I have begun to try to examine in mice and in human populations whether exposures in the peri-pubertal stage might alter the risk for preterm birth. Do you think this is a good idea?

Dr. Menon: Yes, for the reasons stated above. Your important work in animal models and conceptual reviews [4, 5] in this area and that of multitudes of others have shown similarities pathways of preterm birth. However, this knowledge often does not translate to promote research using these models. As long as we understand strengths and weaknesses of a ‘model’, we should use them for gaining more knowledge.

EB: For example, uterine or pelvic irradiation in the context of cancer therapy in girls is associated with an increased risk for preterm birth [6]. Perhaps this might generate a small uterus that does not expand well and that this leads to the outcome.

Dr. Menon: This is interesting, but I can also see a pathway whereby radiation of the uterus leads to damage of susceptible nucleotides and the induction of damage repair responses and chronic inflammation. Dysregulation of DNA damage repair enzymes have been reported in fetal tissues in response to stressors[7]. This may then be aggravated by the pregnancy environment and therefore lead to preterm birth.

EB: How, in your mind could a specific gene or group of genes affect such a complex trait as preterm birth in women?

Dr. Menon: I am now backtracking a bit from this idea. From 2001 forward, several studies, including our own, found an association betweenIL-1β expression[8] or polymorphisms in the IL-1β gene[9] and preterm birth. It made a big splash because of our ability, using PCR technology, to do the study. After finding a statistically significant association between SNP (single nucleotide polymorphisms) in this gene and preterm birth, the field advanced to detect gene variants in several genes using multiplexed assays and moved on to increasing numbers of genes and found statistically significant associations in one cohort but that unfortunately did not reproduce in other populations due to various reasons. Since that time, we have progressed to GWAS (genome wide association studies) to find a genotype for preterm birth. Promising results have come out recently from Lou Muglia’s group including several promising candidates with functional relevance. The critical problem however, is that a SNP—even in a gene well known to be important in a pathway related to preterm birth- is not likely a good predictor of this outcome. The SNP must be expressed in the context of a specific environment in order to result in the disease. Many factors can change the course of the expression of a gene. Within a person’s body, other biological mechanisms can compensate for an abnormal SNP. Disease occurs only when these compensatory mechanisms are compromised. This makes study of the genotype difficult. Which of hundreds of compensatory mechanisms do we take into account in delineation of the preterm birth phenotype? At best, we may use SNPs in important genes that are associated with preterm birth in more than one population, irrespective of their function, in the development of a risk scoring system and studies to examine preterm birth risk.

EB: Several studies have suggested African Americans experience a higher rate of preterm birth regardless of socioeconomic status. Why is this true?

Dr. Menon: There is a clear increased risk of preterm birth in African Americans. There is likely a genetic component, but it is complex. The migratory pattern of humans over time has produced older populations (African) that have a disintegrated haplotype compared to new populations (Caucasian). By “disintegrated,” I mean there is more linkage disequilibrium, with fewer blocks of SNPs remaining intact and being present together within the genome. This reflects adaptive pressure to changing environments. This may result in both increased susceptibility to infection and enhanced responsiveness—including inflammation. This may be the genetic basis for increased preterm birth in African versus Caucasian populations[10]. This would not explain differences in preterm birth risk in African Americans as compared to Africans, since the longest time Africans have been in America—less than 500 years- is probably not enough to cause significant changes in haplotype stability. Somewhat paradoxically, African immigrants in the United States, as compared to their African American counterparts, have a lower risk of preterm birth, [11–13]. Again, environment must play a role.

EB: You and I have written about oxidative stress and preterm birth, and there is clearly biological evidence that this pathway and its mediators can interact with numerous pathways, including apoptosis, etc. that relate to preterm birth. Yet clinical trials have failed to show benefit from antioxidant therapy. Do you think this failure relates to not choosing women with the right preterm birth phenotype?

Dr. Menon: Absolutely. These trials suffer from several problems: 1) wrong choice of population, i.e. who is truly at risk due to antioxidant deficiency 2) wrong choice of anti-oxidants, 3) inadequate knowledge of mechanisms involved and 4) incorrect choice of biomarkers to follow antioxidant response. For an example, we know that inflammation relates to oxidative stress. However, we do not know the specific type of inflammation generated by a particular stress (i.e. heterogeneity of inflammatory markers due to distinct form of oxidative stress), nor do we know the particular population that might be at risk for preterm birth given this inflammation. This scenario points to your issue of the pre pregnancy phenotype. For another example, the trials have used Vitamin E, which affects peroxidation at the level of the cellular membrane- but not elsewhere. How do we expect this to affect the inflammatory response when the critical mediators are within the cell nucleus or cytoplasm? Other antioxidants used for trials only modify oxidation of lipids but not proteins or DNA—we say that failure of these treatments constitutes failure to modify oxidative stress-induced damage to various cellular components—the damage that in turn generates various inflammatory pathways leading to preterm birth. Supplementation may enhance overall deficiency of particular antioxidants but it will not reverse oxidative stress- induced damage to relevant tissues. Such damage may cause problems more widespread than antioxidant deficiency by itself. This is where early intervention, prior to pregnancy and during early stages of feto-placental development, may benefit subjects with oxidative stress induced damage to reproductive tissues. Antioxidant supplementation may still work in a very small subset of subjects where that deficiency is directly causing the problem. If oxidative stress induced tissue damage due to various risk exposures and not due to antioxidant deficiency are contributing to preterm birth, such cases are unlikely to benefit from supplementation. We need to stop those tissue damage associated pathways[7].

EB: We have begun to use progesterone for prevention of preterm birth in women with a previous preterm birth and in women who present with a shortened cervix. Yet, many women do not respond, and overall we have not significantly decreased anything but late preterm birth. Do you think that understanding/developing a phenotype will increase our success rate?

Dr. Menon: Absolutely. Progesterone appears to prevent preterm birth in subset of women who present with a short cervix and or with a history of previous preterm birth. However, the proportion of the population, particularly in some countries, that meet this criterion is very low. Moreover, not all treated women respond. Just like antioxidant therapy, progesterone treatment cannot be used population wide. While some suggest that progesterone may act as an anti-inflammatory agent, this is not completely clear and in addition, we really do not know the mechanisms by which progesterone may exert its action. Most concerning is that we have no idea what are the long-term effects of the administration of large doses of progesterone. Particularly, we do not know if exposure to progesterone during pregnancy will increase women’s risk of breast and other gynecologic tumors over their lifetime. Moreover, we have no idea the effects of in utero exposure to large doses of progesterone on IQ, growth, behavior, metabolic syndrome, etc. during child development. We must carefully examine these effects.

EB: So do you think that progesterone has the capacity to be the Diethylstilbestrol of our time?

Dr. Menon: Absolutely. Progesterone has a major role in maintaining pregnancy and its function and different feto-maternal tissues regulate its function through progesterone’s genomic and non-genomic receptors. This receptor – ligand interaction is tissue and receptor type and their activation status dependent. Supplementing progesterone often has negative effects on some of these cell types.

EB: Preterm birth is a complex problem, affecting pregnancies around the world. Yet, the number of researchers involved in the study of this problem is relatively small. How do we increase the number of researchers interested in preterm birth?

Dr. Menon: The recent awareness created by efforts of such organizations such as the March of Dimes, the World Health Organization, and other philanthropic foundations (e.g. Bill and Melinda Gates Foundation, Burroughs Welcome etc.), and emerging agencies in Europe and elsewhere will create interest in the problem. In addition, the recent interest in the data surrounding fetal programming for adult cardiovascular and metabolic disease has created an awareness of this condition outside of perinatology and neonatology fields. This awareness will increase the interest in research and educational activities in preventing preterm birth. I hope that National Research Institutes, such as the NIH in the US will come to the table with more funding to support our understanding of the pre-pregnancy state and reproductive development in girls and to support our basic understanding of normal labor. This may encourage entrance of more basic researchers into the field. We also need a coordinated effort amongst NGOs around the world to generate efforts to support research and training for the effective ways to deliver current technologies to prevent preterm birth. Finally, we need to find a way to get industry interested in the problem. Many companies are not interested in devoting research and development funds to the problem because they are wary of the liability associated with giving pregnant women medication—somehow we must address this issue. Moreover, companies need to get increased incentives to continue any current successful projects.

EB: The tendency in research is towards larger programs run by a smaller number of principal scientists. The alternative is collaborations amongst a large number of independent scientists, each with their own voice and perspective. Which do you think is going to be more successful in solving the pre pregnancy phenotype for preterm birth? Why?

Dr. Menon: Lack of interdisciplinary collaborations have hurt the fields of reproductive and perinatal biology, as we are often restricted to limited resources we have for our use. Each pregnancy is different, and we need more thinking around evaluation of static risk factors, as well as dynamic changes over time in that specific pregnancy. Research in this problem needs to start with individual patients, then proceed according to the saying “locally, regionally, globally”. Organizations such as PREBIC are in existence to bring researchers together for open and unbiased discussions, integrating knowledge, identifying knowledge gaps to formulate a research agenda, not in one lab but around the globe [14, 15].

EB: what about research on preterm birth in resource-poor settings?

Dr. Menon: I do not really have an answer to that. We have tried and need to continue to try to build strong interdisciplinary teams that show that such research is possible. We need to engage all kinds of scientists, health care workers, and public health specialists. We have identified gaps in our knowledge and understanding, and now we need to pool our resources—wherever we are- to solve this problem. We need to acknowledge that important resources are not just money. They include knowledge and all matter of skills: social, organizational, clinical, and political. Both governmental and non-governmental agencies and foundations are currently active in setting up cohort studies for identifying risk factors, biomarkers, and providing needed care as well as organizing educational activities to minimize the risk of preterm birth.

EB: Thanks so much for taking the time to interview with me and for your insight and efforts to solve a very real problem in the world.

Dr. Menon: Thanks so much for interviewing me.

Since this time, PREBIC Global has evolved and enhanced its worldwide focus to include regional branches in Europe, Australasia, Africa/South America and North America. As a group, PREBIC continues to think about the many issues around doing preterm birth research: problems of translational research, clinical trials and commercialization, integration of animal models, the roles of biomarkers, genetics, and nutrition, the relationship between mechanisms driving normal parturition and premature labor, and the critical differences between populations in developed and developing countries. National Research Institutes, such as the National Institute of Child Health and Human development in the US, are putting more emphasis in fields such as pediatric gynecology, which I believe is relevant research in this area. In addition to animal models and the role of the immune system in preterm birth, I continue to think about the interaction between developmental programing and the timing of environmental exposure that leads to preterm birth. I also seek to highlight the importance of the role of diversity in and inclusion of women’s voices in preterm birth research.