Sarras, Michael P.

As a member of the phylum Cnidaria, the body wall of hydra is organized as an epithelium bilayer (ectoderm and endoderm) with an intervening extracellular matrix (ECM). Previous studies have established the general molecular structure of hydra ECM and indicate that it is organized as two subepithelial zones that contain basement membrane components such as laminin and a central fibrous zone that contains interstitial matrix components such as a unique type I fibrillar collagen. Because of its simple structure and high regenerative capacity, hydra has been used as a developmental model to study cell-ECM interaction during epithelial morphogenesis. The current study extends previous studies by focusing on the relationship of ECM biogenesis to epithelial morphogenesis in hydra, as monitored during head regeneration or after simple incision of the epithelium. Histological studies indicated that decapitation or incision of the body column resulted in an immediate retraction of the ECM at the wound site followed by a re-fusion of the bilayer within 1 hour. After changes in the morphology of epithelial cells at the regenerating pole, initiation of de novo biogenesis of an ECM began within hours while full reformation of the mature matrix required approximately 2 days. These processes were monitored using probes to three matrix or matrix-associated components: basement membrane-associated hydra laminin β1 chain (HLM-β1), interstitial matrix-associated hydra fibrillar collagen (Hcol-I) and hydra matrix metalloproteinase (HMMP). While upregulation of mRNA for both HLM-β1 and Hcol-I occurred by 3 hours, expression of the former was restricted to the endoderm and expression of the latter was restricted to the ectoderm. Upregulation of HMMP mRNA was also associated with the endoderm and its expression paralleled that for HLM-β1. As monitored by immunofluorescence, HLM-β1 protein first appeared in each of the two subepithelial zones (basal lamina) at about 7 hours, while Hcol-I protein was first observed in the central fibrous zone (interstitial matrix) between 15 and 24 hours. The same temporal and spatial expression pattern for these matrix and matrix-associated components was observed during incision of the body column, thus indicating that these processes are a common feature of the epithelium in hydra. The correlation of loss of the ECM, cell shape changes and subsequent de novo biogenesis of matrix and matrix-associated components were all functionally coupled by antisense experiments in which translation of HLM-β1 and HMMP was blocked and head regeneration was reversibly inhibited. In addition, inhibition of translation of HLM-β1 caused an inhibition in the appearance of Hcol-I into the ECM, thus suggesting that binding of HLM-β1 to the basal plasma membrane of ectodermal cells signaled the subsequent discharge of Hcol-I from this cell layer into the newly forming matrix. Given the early divergence of hydra, these studies point to the fundamental importance of cell-ECM interactions during epithelial morphogenesis.

Gestational diabetes mellitus (GDM) is a frequently observed complication of pregnancy and is associated with an elevated risk of adverse maternal and neonatal outcomes. Many women with GDM will go on to have future pregnancies, and these pregnancies may or may not be affected by GDM. We conducted a literature search, and based on data from key studies retrieved during the search, we describe the epidemiology of GDM recurrence. This includes a summary of the observed clinical risk factors of increasing maternal age, weight, ethnicity, and requirement for insulin in the index pregnancy. We then present our data from Mayo Clinic (January 2013–December 2017) which identifies a GDM recurrence rate of 47.6%, and illustrates the relevance of population-based studies to clinical practice. Lastly, we examine the available evidence on strategies to prevent GDM recurrence, and note that more research is needed to evaluate the effect of interventions before, during and after pregnancy.

The Center for Disease Control and Prevention ranks diabetes mellitus (DM) as the seventh leading cause of death in the USA. The most prevalent forms of DM include Type 2 DM, Type 1 DM, and gestational diabetes mellitus (GDM). While the acute problem of diabetic hyperglycemia can be clinically managed through dietary control and lifestyle changes or pharmacological intervention with oral medications or insulin, long-term complications of the disease are associated with significant morbidity and mortality. These long-term complications involve nearly all organ systems of the body and share common pathologies associated with endothelial cell abnormalities. To better understand the molecular mechanisms underlying DM as related to future long-term complications following hyperglycemia, we have undertaken a study to determine the frequency that GDM did or did not occur in the second pregnancy of women who experienced GDM in their first pregnancy between 2013 and 2018 at Mayo Clinic, Rochester, MN. Within the five-year period of the study, the results indicate that 7,330 women received obstetrical care for pregnancy during the study period. Of these, 150 developed GDM in their first pregnancy and of these, 42 (28%) had a second pregnancy. Of these 42 women, 20 again developed GDM and 22 did not develop GDM in their second pregnancy within the study period. Following the occurrence of GDM in the first pregnancy, the study (1) established the number of women with and without GDM in the second pregnancy and (2) confirmed the feasibility to study diabetic metabolic memory using maternal placental tissue from GDM women. These studies represent Phase I of a larger research project whose goal is to analyze epigenetic mechanisms underlying true diabetic metabolic memory using endothelial cells isolated from the maternal placenta of women with and without GDM as described in this article.

Metabolic memory (MM) is defined as the persistence of diabetic (DM) complications even after glycemic control is pharmacologically achieved. Using a zebrafish diabetic model that induces a MM state, we previously reported that, in this model, tissue dysfunction was of a heritable nature based on cell proliferation studies in limb tissue and this correlated with epigenetic DNA methylation changes that paralleled alterations in gene expression. In the current study, control, DM, and MM excised fin tissues were further analyzed by MeDIP sequencing and microarray techniques. Bioinformatics analysis of the data found that genes of theDNA replication/DNA metabolism processgroup (with upregulation of theapex1, mcm2, mcm4, orc3,lig1, anddnmt1 genes) were altered in the DM state and these molecular changes continued into MM. Interestingly, DNA methylation changes could be found as far as 6–13 kb upstream of the transcription start site for these genes suggesting potential higher levels of epigenetic control. In conclusion, DNA methylation changes in members of theDNA replication/repair processgroup best explain the heritable nature of cell proliferation impairment found in the zebrafish DM/MM model. These results are consistent with human diabetic epigenetic studies and provide one explanation for the persistence of long term tissue complications as seen in diabetes.

AbstractAs previously reported by our laboratory, streptozocin‐induced diabetes mellitus (DM) in adult zebrafish results in an impairment of tissue regeneration as monitored by caudal fin regeneration. Following streptozocin withdrawal, a recovery phase occurs to reestablish euglycemia, via pancreatic beta‐cell regeneration. However, DM‐associated impaired fin regeneration continues indefinitely in the metabolic memory (MM) state, allowing for subsequent molecular analysis of the underlying mechanisms of MM. This study focuses on elucidating the molecular basis that explains the DM‐associated impaired fin regeneration and why it persists into the MM state with the aim of better understanding MM. Using a combination of microarray analysis and bioinformatics approaches, our study found that of the 14,900 transcripts analyzed, aberrant expression of 71 genes relating to tissue developmental and regeneration processes were identified in DM fish and the altered expression of these 71 genes persisted in MM fish. Key regulatory genes of major development and signal transduction pathways were identified among this group of 71. The aberrant expression of key regulatory genes in the DM state that persist into the MM state provides a plausible explanation on how hyperglycemia induced impaired fin regeneration in the adult zebrafish DM/MM model.

Metabolic memory (MM) is the phenomenon whereby diabetes complications persist and progress after glycemic recovery is achieved. Here, we present data showing that MM is heritable and that the transmission correlates with hyperglycemia-induced DNA hypomethylation and aberrant gene expression. Streptozocin was used to induce hyperglycemia in adult zebrafish, and then, following streptozocin withdrawal, a recovery phase was allowed to reestablish a euglycemic state. Blood glucose and serum insulin returned to physiological levels during the first 2 weeks of the recovery phase as a result of pancreatic β-cell regeneration. In contrast, caudal fin regeneration and skin wound healing remained impaired to the same extent as in diabetic fish, and this impairment was transmissible to daughter cell tissue. Daughter tissue that was never exposed to hyperglycemia, but was derived from tissue that was, did not accumulate AGEs or exhibit increased levels of oxidative stress. However, CpG island methylation and genome-wide microarray expression analyses revealed the persistence of hyperglycemia-induced global DNA hypomethylation that correlated with aberrant gene expression for a subset of loci in this daughter tissue. Collectively, the data presented here implicate the epigenetic mechanism of DNA methylation as a potential contributor to the MM phenomenon.