Practical use of C1 esterase inhibitor concentrate for clinical amniotic fluid embolism

Postpartum acute myometritis suppresses expression of contraction-associated proteins in the gravid uterus

Uterine atony is a major contributor to postpartum hemorrhage. We previously proposed the novel histological concept of postpartum acute myometritis (PAM) to elucidate the pathophysiology of uterine atony. This concept involves the infiltration of macrophages and neutrophils, as well as mast cell and complement activation in the myometrium. However, the pathological mechanism underlying uterine atony in the context of PAM remains unclear. Herein, we focused on uterine contraction-associated proteins (CAPs) including connexin 43 (Cx43), oxytocin receptors (OXR), prostaglandin receptors EP1, EP3, FP, and protease-activated receptor (PAR)-1. This follow-up study aimed to compare CAP expression between PAM and control groups. We selected 38 PAM subjects from the cases enrolled in our amniotic fluid embolism registry between 2011 and 2018. Control tissues from 10 parturients were collected during cesarean section. We stained the myometrial tissues with the following CAP markers, inflammatory cell markers, and other markers: Cx43, OXR, EP1, EP3, FP, PAR-1, C5a receptor, tryptase, neutrophil elastase, CD68, β-actin, and Na+/K+-ATPase. The immunostaining-positive areas of Cx43, OXR, EP1, EP3, and FP standardized by β-actin in the PAM tissue were significantly smaller than in the control group, whereas those of PAR-1 and Na+/K+-ATPase increased significantly in the PAM group. The Cx43- and OXR-positive areas correlated negatively with the immunostaining-positive cell numbers of CD68 and tryptase with halo, respectively. PAM may impair individual and synchronized myocyte contraction, leading to uterine atony refractory to uterotonics. Further cell-based studies are needed to elucidate the molecular mechanism by which inflammatory cells suppress CAP expression.

A novel modified thaw-siphon method for extracting cryoprecipitate: The Bokutoh-siphon method

BACKGROUND

Cryoprecipitate (CRYO) is neither produced nor supplied by the Japanese Red Cross Society. A novel CRYO extraction method established in-house by modifying a thaw-siphon technique was demonstrated in this study.

STUDY DESIGN AND METHODS

A pack of fresh frozen plasma was thawed and equally divided into two bags for CRYO extraction by different methods. CRYO was extracted from the blood plasma using a standard centrifugation method and our modified thaw-siphon method (Bokutoh-siphon method; B method). The two different CRYOs extracted were analyzed to compare the differences in the amount of fibrinogen recovered, clotting factors extracted, and clotting activity.

RESULTS

The amount of fibrinogen in the CRYO extracted using the B-siphon method was similar to that obtained using the standard method (recovery of fibrinogen: B-siphon method: 71.2% vs. standard method: 61.0%). The amount of clotting XIII factor extracted using the B-siphon method was significantly lower than those extracted using the standard method. On the other hand, clotting II, V factors, and C1q esterase inhibitor not concentrated in CRYO content from the B-siphon method were significantly higher than that from the standard method.

CONCLUSION

A new in-house CRYO preparation method was established by modifying a previously used thaw-siphon method. A coagulation factor-rich CRYO was extracted from plasma frozen at -40°C along with the first fraction of thawed plasma, without using a large-capacity refrigerated centrifuge for blood bags.

Elevated bradykinin receptor type 1 expression in postpartum acute myometritis: Possible involvement in augmented interstitial edema of the atonic gravid uterus

AIM

Uterine atony is a major cause of postpartum hemorrhage. We recently proposed a new concept for the histopathophysiology of refractory uterine atony, postpartum acute myometritis (PAM), characterized by acute inflammatory changes with massive stromal edema, increased numbers of complement C5a receptors and diffuse mast cell activation in the myometrium. We herein focused on the possible involvement of the kinin-kallikrein system in the rapid development of interstitial edema in PAM, particularly bradykinin receptor type 1 (B1R), which is up-regulated under inflammatory conditions. The present study investigated B1R expression with uterine interstitial edema in PAM.

METHODS

Our institution plays an important role in a Japanese amniotic fluid embolism registry project. We selected PAM cases from uterine samples delivered to us for further analyses between 2012 and 2017. Control tissues were collected during cesarean section and planned hysterectomy. B1R expression was semi-quantitatively measured by immunohistochemistry, while uterine interstitial edema was estimated by semi-quantitative measurements of the alpha smooth muscle actin-negative area using immunohistochemistry.

RESULTS

There were 36 and 8 cases in the PAM and control groups, respectively. The alpha smooth muscle actin-negative area was increased in the PAM group, concomitant with the significant up-regulation of B1R expression in uterine smooth muscle cells, vascular endothelial cells, and neutrophils. A positive correlation was observed between these two factors.

CONCLUSION

We demonstrated the up-regulated expression of B1R in the myometrium and its positive correlation with histologically estimated interstitial edema, suggesting the contribution of the kinin-kallikrein-B1R system to the development of interstitial edema in PAM cases.