Biomedical Engineering Reference
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red blood cell stage of the disease, HO-1 expression was found to
increase susceptibility to liver infection. To address this hepatic role
of HO-1 therapeutically, siRNA targeting HO-1 was complexed with
98N
mice at a dose
of 5 mg/kg. The resultant 60% silencing of HO-1 achieved through
systemic siRNA treatment conferred the same effect as genomic
deletion of the gene, namely prevention of blood-stage infection.
-5 and administered intravenously to Hmox
+/+
12
34
This investigation illustrates that genetically modified mice can
serve as an important control in siRNA studies. Conversely, in the
case that modified mice are not readily available, siRNA-mediated
silencing might be used in place of genetic models. In this way,
systemic gene silencing can be used to answer interesting biological
questions. For example, 98N
-5 was also used to answer a question
critical to the field of RNAi: Whether exogenous siRNAs disrupted
endogenous microRNA (miRNA) pathways
12
36
miRNAs are
small RNAs produced in the nucleus and exported to the cytoplasm,
where they regulate genes controlling critical cell processes, including
proliferation and survival.
in vivo
.
37, 38
Previously, it was reported that
genomically integrated short hairpin RNA (shRNA) disrupted miRNA
pathways, leading to acute and non-specific toxicity.
39
To investigate
whether the introduction of exogenous small RNAs downstream of
exportin-5 — which had been saturated in the shRNA experiments,
resulting in the observed toxicity — would mitigate this deleterious
effect, 98N
-5 was complexed with siRNA targeting F7 or ApoB and
injected intravenously into mice at a dose of either 2 or 5 mg/kg.
After confirming target gene silencing, the levels of miRNAs miR-
122, miR-16, and let-7 were found to be unaltered relative to saline
control, demonstrating that siRNA delivery did not disrupt miRNA
production.
12
This was corroborated by the mRNA levels of seven
miR-122 targets, which remained unaffected by siRNA delivery.
After demonstrating that intravenously injected lipidoids could
efficiently silence hepatic genes, we investigated whether they could
be used to silence genes in monocytes
36
40
and epithelial ovarian cancer
cells.
Monocytes are precursors to the phagocytotic macrophages
of the innate immune system, mediating inflammatory responses
to a variety of diseases, including cancer, myocardial infarction, and
diabetes.
41, 42
43
Although paramount to the initial immune response, one
subset termed “inflammatory monocytes” often supports disease
by promoting chronic inflammation. Such inflammatory monocytes
are thus an attractive therapeutic target; however, inactivating
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