Enucleation of mammalian cells in suspension

Genetically engineered and enucleated human mesenchymal stromal cells for the targeted delivery of therapeutics to diseased tissue

Targeting the delivery of therapeutics specifically to diseased tissue enhances their efficacy and decreases their side effects. Here we show that mesenchymal stromal cells with their nuclei removed by density-gradient centrifugation following the genetic modification of the cells for their display of chemoattractant receptors and endothelial-cell-binding molecules are effective vehicles for the targeted delivery of therapeutics. The enucleated cells neither proliferate nor permanently engraft in the host, yet retain the organelles for energy and protein production, undergo integrin-regulated adhesion to inflamed endothelial cells, and actively home to chemokine gradients established by diseased tissues. In mouse models of acute inflammation and of pancreatitis, systemically administered enucleated cells expressing two types of chemokine receptor and an endothelial adhesion molecule enhanced the delivery of an anti-inflammatory cytokine to diseased tissue (with respect to unmodified stromal cells and to exosomes derived from bone-marrow-derived stromal cells), attenuating inflammation and ameliorating disease pathology. Enucleated cells retain most of the cells' functionality, yet acquire the cargo-carrying characteristics of cell-free delivery systems, and hence represent a versatile delivery vehicle and therapeutic system.

The in vivo control of prostaglandin H synthase-2 messenger ribonucleic acid expression in the human amnion at parturition

Prostaglandin H synthase-2 (PGHS-2) activity and mRNA rise in the human amnion at late gestation, contributing to the increase in intrauterine PG production crucial for labor and delivery. In the present investigation we have determined the mechanism that controls amniotic PGHS-2 mRNA levels in vivo at term parturition. Amnion membranes were collected after elective cesarean section (n = 20), and after spontaneous labor (n = 20). PGHS-2 relative gene transcription rates were determined by transcriptional run-on, and PGHS-2 mRNA and heterogeneous nuclear RNA (hnRNA) relative abundance were measured by quantitative real-time RT-PCR. The PGHS-2 mRNA degradation rate was determined by incubating amnion in the presence of the transcription inhibitor 5,6-dichlorobenzimidazole riboside. The dynamics of PGHS-2 hnRNA and mRNA abundance were characterized in 0- to 24-h tissue incubations. The PGHS-2 relative gene transcription rate was a significant (P < 0.05) predictor of PGHS-2 hnRNA and mRNA abundance, and PGHS-2 hnRNA was also a predictor (P < 0.01) of PGHS-2 mRNA levels both before and after labor. Interestingly, even though PGHS-2 gene activity remained unchanged, PGHS-2 mRNA abundance increased with labor and displayed constitutive stability before and after labor. PGHS-2 mRNA levels spontaneously increased by 400% (P < 0.01) upon incubation for 24 h, whereas the transcription rate dropped by 95% during the first 2 h, then rebounded significantly between 6-24 h. Thus, PGHS-2 mRNA abundance is transcriptionally controlled in term amnion. Labor does not increase PGHS-2 gene activity or mRNA stability. The PGHS-2 gene is probably induced before labor by a factor(s) originating in the amnion membrane, and the resulting stable mRNA accumulates progressively in the tissue throughout labor and delivery.

Sequence analysis of mitochondrial DNA in a mouse cell line resistant to chloramphenicol and oligomycin

A mouse L-cell line, designated 111-OB3, is described which is resistant to two drugs, chloramphenicol and oligomycin. The cells contain two types of mitochondrial DNA molecules, in roughly equal proportions, which differ in that one is cleaved by endonuclease EcoRI at a novel site within the coding sequence for subunit 6 of the mitochondrial ATPase (ATPase-6). Sequence analysis reveals that the cleavage site was created by a single transversion which predicts a replacement of valine in the wild-type ATPase-6 by glutamic acid. The replacement occurs in a hydrophobic amino acid sequence which is highly conserved in mouse, human, and bovine proteins. The position of the replacement is similar to a substitution observed in one class of yeast mutants resistant to oligomycin. Both of the mitochondrial DNA molecules in 111-OB3 also have a single nucleotide change in the gene encoding the large (16S) rRNA. These observations are consistent with the hypothesis that oligomycin resistance in mammalian cells can be cytoplasmically determined and can result from alterations in ATPase-6. The appearance of the mutation before selection in oligomycin suggests a model for the origin of mitochondrial mutations in mammalian cells.

Sequence analysis of mitochondrial DNA in a mouse cell line resistant to chloramphenicol and oligomycin

A mouse L-cell line, designated 111-OB3, is described which is resistant to two drugs, chloramphenicol and oligomycin. The cells contain two types of mitochondrial DNA molecules, in roughly equal proportions, which differ in that one is cleaved by endonuclease EcoRI at a novel site within the coding sequence for subunit 6 of the mitochondrial ATPase (ATPase-6). Sequence analysis reveals that the cleavage site was created by a single transversion which predicts a replacement of valine in the wild-type ATPase-6 by glutamic acid. The replacement occurs in a hydrophobic amino acid sequence which is highly conserved in mouse, human, and bovine proteins. The position of the replacement is similar to a substitution observed in one class of yeast mutants resistant to oligomycin. Both of the mitochondrial DNA molecules in 111-OB3 also have a single nucleotide change in the gene encoding the large (16S) rRNA. These observations are consistent with the hypothesis that oligomycin resistance in mammalian cells can be cytoplasmically determined and can result from alterations in ATPase-6. The appearance of the mutation before selection in oligomycin suggests a model for the origin of mitochondrial mutations in mammalian cells.

Most iodinatable fibroblast surface proteins accompany the cytoplast membrane during cytochalasin B-mediated enucleation of chick embryo fibroblasts

Six different proteins are found to be reproducibly exposed on the cell surface of chicken embryo fibroblasts (CEF) by the criterion of lactoperoxidase-catalyzed iodination (250,000, 185,000, 130,000, 100,000, 87,000, and 75,000 daltons). We wondered whether cell enucleation might lead to a differential partition of these surface proteins with the karyoplast or cytoplast membrane. We found that there is a marked enrichment of most iodinatable cell surface proteins in the cytoplast after cytochalasin-mediated enucleation of cell monolayers. Nearly all the iodinatable fibronectin remains with the cytoplast. Of the six labeled proteins, the karyoplast membrane contains a small amount of the 130 kdalton protein as well as trace levels of the 100-, 85-, and 75-kdalton proteins. Proteolysis or selective shedding of membrane proteins were not significant factors in the relative exclusion of iodinatable membrane proteins from the karyoplast. The cytoplast could replace some exposed membrane proteins after removal by trypsinization; however, fibronectin was not detectable within 10 h. That the karyoplast was not capable of membrane protein synthesis and/or insertion was suggested by the lack of any change in the labeling pattern of karyoplasts up to 8-h incubation after enucleation. A variety of control studies indicated that the surface proteins identified in this report were cell-derived and not adsorbed serum components. That some of the iodinatable proteins are intrinsic membrane proteins was suggested by their resistance to removal by conditions thought to extract extrinsic membrane proteins (i.e., low salt, high salt, and NaOH washes). lack of effect of cytoskeletal disrupting agents (preliminary evidence) suggests the nonrandom partition of membrane proteins may depend on anchoring of membrane proteins by a system(s) in the cytoplast other than intact microtubules and microfilaments.