Emerging evidence suggests that intracellular molecules and organelles transfer between cells during embryonic development, tissue homeostasis and disease. We and others recently showed that transplanted and host photoreceptors engage in bidirectional transfer of intracellular material in the recipient retina, a process termed material transfer (MT). We used cell transplantation, advanced tissue imaging approaches, genetic and pharmacologic interventions and primary cell culture to characterize and elucidate the mechanism of MT. We show that MT correlates with donor cell persistence and the accumulation of donor-derived proteins, mitochondria and transcripts in acceptor cells in vivo. MT requires cell contact in vitro and is associated with the formation of stable microtubule-containing protrusions, termed photoreceptor nanotubes ( Ph NTs), that connect donor and host cells in vivo and in vitro. Ph NTs mediate GFP transfer between connected cells in vitro. Furthermore, interfering with Ph NT outgrowth by targeting Rho GTPase-dependent actin remodelling inhibits MT in vivo. Collectively, our observations provide evidence for horizontal exchange of intracellular material via nanotube-like connections between neurons in vivo.

ObjectiveInformation on adverse pregnancy outcomes is important to monitor the impact of public health interventions. Miscarriage is a challenging end point to ascertain and there is scarce information on its rate in low-income countries. The objective was to estimate the background rate and cumulative probability of miscarriage in rural western Kenya.DesignThis was a population-based prospective cohort.Participants and settingWomen of childbearing age were followed prospectively to identify pregnancies and ascertain their outcomes in Siaya County, western Kenya. The cohort study was carried out in 33 adjacent villages under health and demographic surveillance.Outcome measureMiscarriage.ResultsBetween 2011 and 2013, among 5536 women of childbearing age, 1453 pregnancies were detected and 1134 were included in the analysis. The cumulative probability was 18.9%. The weekly miscarriage rate declined steadily with increasing gestation until approximately 20 weeks. Known risk factors for miscarriage such as maternal age, gravidity, occupation, household wealth and HIV infection were confirmed.ConclusionsThis is the first report of weekly miscarriage rates in a rural African setting in the context of high HIV and malaria prevalence. Future studies should consider the involvement of community health workers to identify the pregnancy cohort of early gestation for better data on the actual number of pregnancies and the assessment of miscarriage.

In Alzheimer’s disease, histochemically visualized cholinesterases with altered pH optimum for activity and inhibitable by indoleamines and the protease inhibitor bacitracin emerge in association with plaques and tangles. It has been suggested that these cholinesterases may participate in the pathologic process. However, it is not known whether the properties of cholinesterases observed in Alzheimer’s disease are due to requirements of histochemical procedures or actual biochemical properties of these enzymes. Using biochemical assays of acetylcholinesterase and butyrylcholinesterase activities, we demonstrate here that serotonin and bacitracin result in a significantly greater and dose-dependent inhibition of cholinesterases in Alzheimer’s disease cortex when compared with age-matched controls. In contrast, variations in pH did not distinguish cholinesterases in Alzheimer’s disease and control cortex. We also confirmed significant reduction of acetylcholinesterase activity in Alzheimer’s disease cortex and increased butyrylcholinesterase activity that only approached significance. We conclude that inhibition by indoleamines and bacitracin is a biochemical characteristic of a proportion of cholinesterases in Alzheimer’s disease that most likely represents the pool associated with plaques and tangles. Most of the available cholinesterase inhibitors are relatively incapable of inhibiting cholinesterases associated with plaques and tangles. The findings of the present investigation open the way for attempts to isolate cholinesterases associated with plaques and tangles and design or discovery of inhibitors specifically targeted to cholinesterases in these lesions.

The goal of photoreceptor transplantation is to establish functional synaptic connectivity between donor cells and second-order neurons in the host retina. There is, however, limited evidence of donor-host photoreceptor connectivity post-transplant. In this report, we investigated the effect of the host retinal environment on donor photoreceptor neurite outgrowth in vivo and identified a neurite outgrowth-promoting effect of host Crx (−/−) retinas following transplantation of purified photoreceptors expressing green fluorescent protein (GFP). To investigate the noncell autonomous factors that influence donor cell neurite outgrowth in vitro, we established a donor-host coculture system using postnatal retinal aggregates. Retinal cell aggregation is sensitive to several factors, including plate coating substrate, cell density, and the presence of Müller glia. Donor photoreceptors exhibit motility in aggregate cultures and can engraft into established aggregate structures. The neurite outgrowth-promoting phenotype observed in Crx (−/−) recipients in vivo is recapitulated in donor-host aggregate cocultures, demonstrating the utility of this surrogate in vitro approach. The removal of Müller glia from host aggregates reduced donor cell neurite outgrowth, identifying a role for this cell type in donor-host signaling. Although disruption of chondroitin sulfate proteoglycans in aggregates had no effect on the neurite outgrowth of donor photoreceptors, disruption of Rho/ROCK signaling enhanced outgrowth. Collectively, these data show a novel role of Crx, Müller glia, and Rho/ROCK signaling in controlling neurite outgrowth and provide an accessible in vitro model that can be used to screen for factors that regulate donor-host connectivity. STEM CELLS 2019;37:529-541 SIGNIFICANCE STATEMENTPoor photoreceptor connectivity in transplants is an unresolved issue. Results of the study show that photoreceptor neurite extension is regulated by Rho/ROCK signaling and report the use of primary retinal cultures as an in vitro platform to investigate donor photoreceptor neurite outgrowth. The results could be used in future work to enhance the connectivity of transplanted photoreceptors.