Exposure to high lethal dose of ionizing radiation results in acute radiation syndrome with deleterious systemic effects to different organs. A primary target is the highly sensitive bone marrow and the hematopoietic system. In the current study C3H/HeN mice were total body irradiated by 7.7 Gy. Twenty four hrs and 5 days after irradiation 2×106 cells from different preparations of human derived 3D expanded adherent placental stromal cells (PLX) were injected intramuscularly. Treatment with batches consisting of pure maternal cell preparations (PLX-Mat) increased the survival of the irradiated mice from ∼27% to 68% (P<0.001), while cell preparations with a mixture of maternal and fetal derived cells (PLX-RAD) increased the survival to ∼98% (P<0.0001). The dose modifying factor of this treatment for both 50% and 37% survival (DMF50 and DMF37) was∼1.23. Initiation of the more effective treatment with PLX-RAD injection could be delayed for up to 48 hrs after irradiation with similar effect. A delayed treatment by 72 hrs had lower, but still significantly effect (p<0.05). A faster recovery of the BM and improved reconstitution of all blood cell lineages in the PLX-RAD treated mice during the follow-up explains the increased survival of the cells treated irradiated mice. The number of CD45+/SCA1+ hematopoietic progenitor cells within the fast recovering population of nucleated BM cells in the irradiated mice was also elevated in the PLX-RAD treated mice. Our study suggests that IM treatment with PLX-RAD cells may serve as a highly effective “off the shelf” therapy to treat BM failure following total body exposure to high doses of radiation. The results suggest that similar treatments may be beneficial also for clinical conditions associated with severe BM aplasia and pancytopenia.

Transplantation of adult mesenchymal stem cells (MSCs) could provide a basis for tissue regeneration. MSCs are typically isolated from bone marrow (BM) based on their preferential adherence to plastic, although with low efficiency in terms of yield and purity. Extensive expansion is needed to reach a significant number of MSCs for any application. Fibrin microbeads (FMB) were designed to attach mesenchymal cells and to provide a matrix for their expansion. The current study was aimed at isolating a high yield of purified BM-derived mouse MSCs based on their preferential adherence and proliferation on FMB in suspension cultures. MSCs could be downloaded to plastics or further expanded on FMB. The yield of MSCs obtained by the FMB isolation technique was about one order of magnitude higher than that achieved by plastic adherence, suggesting that these cells are more abundant than previously reported. FMB-isolated cells were classified as MSCs by their fibroblastic morphology, self-renewal ability, and expression profile of their surface antigens, as examined by flow cytometry and immunostaining. In cell culture, the isolated MSCs could be induced to differentiate into three different mesodermal lineages, as demonstrated by histochemical stains and by RT-PCR analyses of tissue-specific genes. MSCs were also able to differentiate into osteocytes while still cultured on FMB. Our results suggest that FMB might serve as an efficient platform for the isolation, expansion, and differentiation of mouse BM-derived MSCs to be subsequently implanted for tissue regeneration.

Fibrin microbeads (FMBs) made using thermal treatment of fibrin drops in oil can efficiently isolate mesenchymal stem cells (MSCs) from bone marrow (BM) and other similar sources and culture them continuously in suspension culture. The pure mesenchymal profile of MSCs isolated using FMBs and their differentiation potency to different mesenchymal lineages were previously described in detail. In the current study, MSCs were isolated from the BM of (GFP+) C57/bl mice using FMBs. Addition of pro-osteogenic medium with 10 mM of ss-glycerolphosphate, 50 microg/mL of ascorbic acid, and 10(-8) M of dexamethasone for 1 month resulted in ossified bone-like solid cellular structures, as seen using fluorescence and scanning electron microscopy (SEM). Such spontaneously formed structures were implanted in full-depth approximately 5-mm-diameter drilled defects in the skulls of wild-type c57/bl mice. Two months later, the excised upper parts of the skulls with the defects were viewed using fluorescence microscopy for green fluorescence protein of the cells in the defect and using SEM. They were also scanned using micro-computed tomography to visualize the formation of new hard tissue. Then the samples were processed and sectioned for hematoxylin and eosin staining and immunohistochemistry. Implanted FMBs loaded with (GFP+) MSCs formed partially mature, dense bone-like tissue using a residual moderate inflammatory process containing remnants of FMBs and neo-angiogenesis. The filled defect with bone-like tissue had a Ca/P ratio similar to that of native bone. Limited merging of the implant with the skull indicated that the induced bone regeneration derived from the MSCs that were delivered with the implant. No repair was seen in the control animals without implants or where the defect was filled with FMBs only. Repair scoring (on a 0-5 scale) was found to be 3.38+/-0.35 in the experimental arm, relative to 0 in the controls (p < 0.001).

Calcium and phosphate regulate PTH mRNA stability through differences in binding of parathyroid (PT) proteins to a minimal 63-nucleotide (nt) cis-acting instability element in its 3'-untranslated region. One of these proteins is adenosine-uridine-rich binding factor (AUF1), whose levels are not regulated in PT extracts from rats fed the different diets. However, two-dimensional gels showed posttranslational modification of AUF1 that included phosphorylation. There is no PT cell line, but in HEK 293 cells the 63-nt element is recognized as an instability element, and RNA interference for AUF1 decreased human PTH secretion in cotransfection experiments. Stably transfected cells with a chimeric GH gene containing the PTH 63-nt cis-acting element were used to study the signal transduction pathway that regulates AUF1 modification and chimeric gene mRNA stability. Cyclosporine A, the calcineurin inhibitor, regulated AUF1 posttranslationally, and this correlated with an increase in the stability of GH-PTH 63-nt mRNA but not of the control GH mRNA. Mice with genetic deletion of the calcineurin Abeta gene had markedly increased PTH mRNA levels that were still regulated by low calcium and phosphorus diets. Therefore, calcineurin regulates AUF1 posttranslationally in vitro and PTH gene expression in vivo but still allows its physiological regulation by calcium and phosphate.

Native and heat denatured fibrinogen are the basis for various matrices used to establish hemostasis as well as for constructing biomedical devices. For example, fibrin microbeads (FMB) prepared by a heated ( approximately 70 degrees C) oil emulsion process were reported to be attractive to mesenchymal-type cells, such as fibroblasts, endothelial and smooth muscle cells, and useful for isolating mesenchymal stem cells from bone marrow. Here, we examined the solution properties of fibrinogen subjected to heat (47-60 degrees C). Fibrinogen exhibited maximal stability of pH(max stab) = 6.8. At physiologically relevant concentrations, Ca(II) stabilized and Zn(II) destabilized fibrinogen against heat denaturation. Scanning electron micrographs (SEM) of precipitated, heat denatured, fibrinogen showed globular structures ( approximately 400 nm diameter), composed of aggregates of >3000 fibrinogen monomers. Monoclonal antibodies (MAb) to various regions of fibrinogen, as well as two polyclonal antibody (Ab) to haptotactic peptides (Haptides) equivalent to or near the C-termini of beta and gamma-chains (beta(463-483) and gamma(372-391/411)), were used to monitor epitopic changes of fibrinogen bound to and heated on plastic ELISA plates. The pattern of altered Ab binding indicated that fibrinogen heat denaturation on plastic exposed the C-terminal epitope gamma(397-411) as well as Haptide epitopes (beta(463-483) and gamma(372-391)). Immuno-staining of FMB prepared by a heated (below 75 degrees C) oil emulsion process, also presented many exposed Haptide epitopes, which probably helped to attract cells. Our results indicated that moderately heat-denatured fibrinogen, in the form of FMB, could be used for cell culturing and biomedical applications.