Effects of the KIR7.1 Blocker VU590 on Spontaneous and Agonist-Induced Contractions of Human Pregnant Myometrium

Innovations in the prevention and treatment of postpartum hemorrhage: Analysis of a novel medicines development pipeline database

Background

A significant barrier to improving prevention and treatment of postpartum hemorrhage (PPH) is a lack of innovative medicines that meet the needs of women and providers, particularly those in low‐and middle‐income countries (LMICs). The Accelerating Innovation for Mothers (AIM) project established a new database of candidate medicines under development for five pregnancy‐related conditions between 2000 and 2021.

Objective

To systematically identify and rank candidates for prevention and treatment of PPH.

Search Strategy

Adis Insight, Pharmaprojects, WHO ICTRP, PubMed, and grant databases were searched to develop the AIM database.

Selection Criteria

AIM database was searched for candidates being evaluated for PPH prevention and treatment, regardless of phase.

Data Collection and Analysis

Candidates were ranked as high, medium, or low potential based on prespecified criteria. Analysis was primarily descriptive, describing candidates and development potential.

Main Results

Of the 444 unique candidates, only 39 pertained to PPH. One was high potential (heat‐stable/inhaled oxytocin) and three were medium potential (melatonin, vasopressin and dofetilide via nanoparticle delivery).

Conclusion

The pipeline for new PPH medicines is concerningly limited, lacking diversity, and showing little evidence of novel technologies. Without significant investment in early‐phase research, it is unlikely that new products will emerge.

A new database of maternal medicine development shows few new PPH candidates are in the pipeline. Significant investment is needed, particularly in early‐phase research.

Uterine Excitability and Ion Channels and Their Changes with Gestation and Hormonal Environment

We address advances in the understanding of myometrial physiology, focusing on excitation and the effects of gestation on ion channels and their relevance to labor. This review moves through pioneering studies to exciting new findings. We begin with the myometrium and its myocytes and describe how excitation might initiate and spread in this myogenic smooth muscle. We then review each of the ion channels in the myometrium: L- and T-type Ca²⁺ channels, K_ATP (Kir6) channels, voltage-dependent K channels (Kv4, Kv7, and Kv11), twin-pore domain K channels (TASK, TREK), inward rectifier Kir7.1, Ca²⁺-activated K⁺ channels with large (KCNMA1, Slo1), small (KCNN1-3), and intermediate (KCNN4) conductance, Na-activated K channels (Slo2), voltage-gated (SCN) Na⁺ and Na⁺ leak channels, nonselective (NALCN) channels, the Na K-ATPase, and hyperpolarization-activated cation channels. We finish by assessing how three key hormones- oxytocin, estrogen, and progesterone-modulate and integrate excitability throughout gestation.

A critical role for the inward rectifying potassium channel Kir7.1 in oligodendrocytes of the mouse optic nerve

Inward rectifying potassium channels (Kir) are a large family of ion channels that play key roles in ion homeostasis in oligodendrocytes, the myelinating cells of the central nervous system (CNS). Prominent expression of Kir4.1 has been indicated in oligodendrocytes, but the extent of expression of other Kir subtypes is unclear. Here, we used qRT-PCR to determine expression of Kir channel transcripts in the mouse optic nerve, a white matter tract comprising myelinated axons and the glia that support them. A novel finding was the high relative expression of Kir7.1, comparable to that of Kir4.1, the main glial Kir channel. Significantly, Kir7.1 immunofluorescence labelling in optic nerve sections and in isolated cells was localised to oligodendrocyte somata. Kir7.1 are known as a K⁺ transporting channels and, using patch clamp electrophysiology and the Kir7.1 blocker VU590, we demonstrated Kir7.1 channels carry a significant proportion of the whole cell potassium conductance in oligodendrocytes isolated from mouse optic nerves. Notably, oligodendrocytes are highly susceptible to ischemia/hypoxia and this is due at least in part to disruption of ion homeostasis. A key finding of this study is that blockade of Kir7.1 with VU590 compromised oligodendrocyte cell integrity and compounds oligodendroglial loss in ischemia/hypoxia in the oxygen-glucose deprivation (OGD) model in isolated intact optic nerves. These data reveal Kir7.1 channels are molecularly and functionally expressed in oligodendrocytes and play an important role in determining oligodendrocyte survival and myelin integrity.