A family of cell-adhering peptides homologous to fibrinogen C-termini.

A family of cell-adhesive peptides homologous to sequences on different chains of fibrinogen was investigated. These homologous peptides, termed Haptides, include the peptides Cß, preCγ, and CαE, corresponding to sequences on the C-termini of fibrinogen chains ß, γ, and αE, respectively. Haptides do not affect cell survival and rate of proliferation of the normal cell types tested. The use of new sensitive assays of cell adhesion clearly demonstrated the ability of Haptides, bound to inert matrices, to mediate attachment of different matrix-dependent cell types including normal fibroblasts, endothelial, and smooth muscle cells. Here we present new active Haptides bearing homologous sequences derived from the C-termini of other proteins, such as angiopoietin 1&2, tenascins C&X, and microfibril-associated glycoprotein-4. The cell adhesion properties of all the Haptides were found to be associated mainly with their 11 N-terminal residues. Mutated preCγ peptides revealed that positively charged residues account for their attachment effect. These results suggest a mechanism of direct electrostatic interaction of Haptides with the cell membrane. The extended Haptides family may be applied in modulating adhesion of cells to scaffolds for tissue regeneration and for enhancement of nanoparticulate transfection into cells.

A 3D rotary renal and mesenchymal stem cell culture model unveils cell death mechanisms induced by matrix deficiency and low shear stress.

BACKGROUND: In epithelial and endothelial cells, detachment from the matrix results in anoikis, a form of apoptosis, whereas stromal and cancer cells are often anchorage independent. The classical anoikis model is based on static 3D epithelial cell culture conditions (STCK). METHODS: We characterized a new model of renal, stromal and mesenchymal stem cell (MSC) matrix deprivation, based on slow rotation cell culture conditions (ROCK). This model induces anoikis using a low shear stress, laminar flow. The mechanism of cell death was determined via FACS (fluorescence-activated cell sorting) analysis for annexin V and propidium iodide uptake and via DNA laddering. RESULTS: While only renal epithelial cells progressively died in STCK, the ROCK model could induce apoptosis in stromal and transformed cells; cell survival decreased in ROCK versus STCK to 40%, 52%, 62% and 7% in human fibroblast, rat MSC, renal cell carcinoma (RCC) and human melanoma cell lines, respectively. Furthermore, while ROCK induced primarily apoptosis in renal epithelial cells, necrosis was more prevalent in transformed and cancer cells [necrosis/apoptosis ratio of 72.7% in CaKi-1 RCC cells versus 4.3% in MDCK (Madin-Darby canine kidney) cells]. The ROCK-mediated shift to necrosis in RCC cells was further accentuated 3.4-fold by H(2)O(2)-mediated oxidative stress while in adherent HK-2 renal epithelial cells, oxidative stress enhanced apoptosis. ROCK conditions could also unveil a similar pattern in the LZ100 rat MSC line where in ROCK 44% less apoptosis was observed versus STCK and 45% less apoptosis versus monolayer conditions. Apoptosis in response to oxidative stress was also attenuated in the rat MSC line in ROCK, thereby highlighting rat MSC transformation. CONCLUSIONS: The ROCK matrix-deficiency cell culture model may provide a valuable insight into the mechanism of renal and MSC cell death in response to matrix deprivation.

Heat denaturation of fibrinogen to develop a biomedical matrix.

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.

Rescue from lethal acute radiation syndrome (ARS) with severe weight loss by secretome of intramuscularly injected human placental stromal cells.

BACKGROUND: Most current cell-based regenerative therapies are based on the indirect induction of the affected tissues repair. Xenogeneic cell-based treatment with expanded human placenta stromal cells, predominantly from fetal origin (PLX-RAD cells), were shown to mitigate significantly acute radiation syndrome (ARS) following high dose irradiation in mice, with expedited regain of weight loss and haematopoietic function. The current mechanistic study explores the indirect effect of the secretome of PLX-RAD cells in the rescue of the irradiated mice. METHODS: The mitigation of the ARS was investigated following two intramuscularly (IM) injected 2 × 106 PLX-RAD cells, 1 and 5 days following 7.7 Gy irradiation. The mice survival rate and their blood or bone marrow (BM) cell counts were followed up and correlated with multiplex immunoassay of a panel of related human proteins of PLX-RAD derived secretome, as well as endogenous secretion of related mouse proteins. PLX-RAD secretome was also tested in vitro for its effect on the induction of the migration of BM progenitors. RESULTS: A 7.7 Gy whole body mice irradiation resulted in ~25% survival by 21 days. Treatment with two IM injections of 2 × 106 PLX-RAD cells on days 1 and 5 after irradiation mitigated highly significantly the subsequent lethal ARS, with survival rate increase to nearly 100% and fast regain of the initial weight loss (P < 0,0001). This was associated with a significant faster haematopoiesis recovery from day 9 onwards (P < 0.01). Nine out of the 65 human proteins tested were highly significantly elevated in the mouse circulation, peaking on days 6-9 after irradiation, relative to negligible levels in non-irradiated PLX-RAD injected mice (P < 0.01). The highly elevated proteins included human G-CSF, GRO, MCP-1, IL-6 and lL-8, reaching >500 pg/mL, while MCP-3, ENA, Eotaxin and fractalkine levels ranged between ~60-160pg/mL. The detected radiation-induced PLX-RAD secretome correlated well with the timing of the fast haematopoiesis regeneration. The radiation-induced PLX-RAD secretome seemed to reinforce the delayed high levels secretion of related mouse endogenous cytokines, including GCSF, KC, MCP-1 and IL-6. Additional supportive in vitro studies also confirmed the ability of cultured PLX-RAD secretome to induce accelerated migration of BM progenitors. CONCLUSIONS: A well-regulated and orchestrated secretion of major pro-regenerative BM supporting secretome in high dose irradiated mice, treated with xenogeneic IM injected PLX-RAD cells, can explain the observed mitigation of ARS. This seemed to coincide with faster haematopoiesis regeneration, regain of severe weight loss and the increased survival rate. The ARS-related stress signals activating the IM injected PLX-RAD cells for the remote secretion of the relevant human proteins deserve further investigation.

High-yield isolation, expansion, and differentiation of murine bone marrow-derived mesenchymal stem cells using fibrin microbeads (FMB).

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.

Effect of halofuginone, a collagen alpha1(I) inhibitor, on wound healing in normal and irradiated skin: implication for hematopoietic stem cell transplantation.

It is a major interest in the field of hematopoietic stem cell transplantation to reduce scarring of healing wounds with overdeposition of collagen due to radiation injury or graft-versus-host disease. Halofuginone (HF) inhibits collagen alpha1(I) gene expression and overdeposition of collagen. We examined the effect of HF on the healing of full-depth incision wounds inflicted in normal skin or skin areas compromised by local preirradiation with 18 Gy. Preirradiation significantly decreased the tensile strength of the healing wounds at day 14 (by approximately 60%, p < 0.0001). In contrast, HF treatment did not significantly decrease the strength of wounds inflicted in both normal and preirradiated skin. Histological evaluation revealed that HF induced moderate thinning of the dermis accompanied by elevated thickness of the epidermis and enhanced rejoining of subdermal muscles in the wound area. HF only minimally reduced total collagen deposition in both groups, with minor changes in the level of more matured fibrillar collagen network. Our study demonstrates that HF does not significantly affect wound strength. This encourages the possible use of HF as an antifibrotic agent with minimal complications for post-hematopoietic stem cell transplantation complications including radiation toxicity and graft-versus-host disease.

High-yield isolation, expansion, and differentiation of rat bone marrow-derived mesenchymal stem cells with fibrin microbeads.

Fibrin microbeads (FMB), made of extensively cross-linked dense and partially denatured fibrin, were used as a matrix for efficient isolation of mesenchymal stem cells (MSC) from rat bone marrow (BM). After 2 days of incubation of FMB with whole BM in suspension, a high number of cells of mesenchymal origin attached to the FMB. On the 14th day after their transfer to plastic, the yield of the cells isolated via FMB was approximately 3-4 times higher than that obtained by currently used protocols based solely on plastic adhesion. This implies that the number of MSC in BM may be higher than previously reported. FACS analyses and immunostaining showed the mesenchymal characteristics of these cells by positive staining for fibronectin, vimentin, CD49E, and CD29. Immediately after isolation, less than 20% of the cells still expressed the hematopoietic markers CD11b and CD45. Most of these cells were eventually eliminated after further expansion of the isolated cells on plastic. Cells isolated via FMB were expanded in culture for more than 4 months and could be defined as MSC along this time period based on their ability to differentiate into precursors of mesenchymal tissues, such as osteogenic, adipogenic, and chondrogenic cells. Similar differentiation plasticity was observed in clones derived from single cells from whole MSC populations isolated via FMB. Based on our results we propose that FMB can serve as a 3-dimensional biodegradable matrix for isolation, differentiation, and possibly implantation of MSC for tissue regeneration.

Interactions of carboplatin with fibrin(ogen), implications for local slow release chemotherapy.

The effect of carboplatin (CPt) on fibrin(ogen) clot formation and the possible use of this combination for local slow release chemotherapy were examined. CPt significantly reduced thrombin-induced fibrin clotting time (CT) and increased clot turbidity in a concentration-dependent manner. When CPt was mixed with physiological levels of fibrinogen (>1 mg/ml), electron-dense nanoparticles (3 nm) were formed, as demonstrated by both optical particle counter and transmission electron microscopy (TEM). Upon thrombin-induced coagulation, the CPt nanoparticles were trapped within the fibrin mesh. At higher fibrinogen levels (>5 mg/ml), the 3-nm CPt nanoparticles aggregated, so that approximately 2% and approximately 0.5% of the CPt on the fibrinogen appeared as larger particles of 10 and 50 nm, respectively. Dialysis experiments showed that 60-70% of the CPt was released from the fibrin clot within one hour as a non-particulate soluble form, while approximately 30% of particulate CPt were retained. Up to 5 mg/ml this portion of firmly attached CPt was dependent of the initial drug level. CPt released from the fibrin by either diffusion or by fibrinolysis exhibited cytotoxic activity towards retinoblastoma (RB) cell lines (Y-79 and Weri RB1) equivalent to free drug. Our study indicates that CPt enhances fibrin clot formation and suggests the use of fibrin with high dose CPt for slow release chemotherapy against localized tumors such as retinoblastoma.

Mitigation of Lethal Radiation Syndrome in Mice by Intramuscular Injection of 3D Cultured Adherent Human Placental Stromal Cells.

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 2×10(6) 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.

Marrow-derived stromal cell delivery on fibrin microbeads can correct radiation-induced wound-healing deficits.

Skin that is exposed to radiation has an impaired ability to heal wounds. This is especially true for whole-body irradiation, where even moderate nonlethal doses can result in wound-healing deficits. Our previous attempts to administer dermal cells locally to wounds to correct radiation-induced deficits were hampered by poor cell retention. Here we improve the outcome by using biodegradable fibrin microbeads (FMBs) to isolate a population of mesenchymal marrow-derived stromal cells (MSCs) from murine bone marrow by their specific binding to the fibrin matrix, culture them to high density in vitro, and deliver them as MSCs on FMBs at the wound site. MSCs are retained locally, proliferate in site, and assist wounds in gaining tensile strength in whole-body irradiated mice with or without additional skin-only exposure. MSC-FMBs were effective in two different mouse strains but were ineffective across a major histocompatability barrier. Remarkably, irradiated mice whose wounds were treated with MSC-FMBs showed enhanced hair regrowth, suggesting indirect effect on the correction of radiation-induced follicular damage. Further studies showed that additional wound-healing benefit could be gained by administration of granulocyte colony-stimulating factor and AMD3100. Collagen strips coated with haptides and MSCs were also highly effective in correcting radiation-induced wound-healing deficits.

Fibrin microbeads loaded with mesenchymal cells support their long-term survival while sealed at room temperature.

Efficient transfer of progenitor cells without affecting their survival is a key factor in any practical cell therapy. Fibrin microbeads (FMB) were developed as hard biodegradable cell carriers. The FMB could efficiently isolate mesenchymal stem cells (MSCs) from different sources and support the expansion of matrix-dependent cell types in a three-dimensional culture in slow rotation. The cells on FMB could also undergo induced differentiation for their eventual implantation to enhance tissue regeneration. FMB loaded with isolated human MSC (hMSC) were sealed in tubes topped up with medium. Almost full cell survival was recorded when the sealed cells were maintained in room temperature for up to 10 days, followed by a recovery period of 24 hrs at optimal conditions. Assay of cells recovery after such long room temperature storage showed ∼80%-100% survival of the cells on FMB, with only a marginal survival of cells that were kept in suspension without FMB in the same conditions. The hMSC that survived storage at room temperature preserved their profile of mesenchymal cell surface markers, their rate of proliferation, and their differentiation potential. The cell protective effect was not dependent on the presence of serum in the storage medium. It was clearly shown that over-expression of hypoxia induced factor-1α in hMSC with time, which may have protected the sealed cells on FMB at room temperature storage, was not necessarily related to extreme hypoxic stress. Foreskin normal fibroblasts on FMB sealed at room temperature were similarly protected, but with no elevation of their hypoxia-induced factor-1α expression. The results also show that FMB, unlike other commercially available cell carriers, could be used for delivery and shipping of progenitor cells at room temperature for extended time intervals. This could be highly useful for cell transfer for therapeutic application and for simplified cell transfer between different research centers.

Blood pressure modulation following activation of mast cells by cationic cell penetrating peptides.

Short cell penetrating peptides (CPP) are widely used in vitro to transduce agents into cells. But their systemic effect has not been yet studied in detail. We studied the systemic effect of the cell penetrating peptides, penetratin, transportan and pro-rich, on rat hemodynamic functions. Intra-arterial monitoring of blood pressure showed that injection of the positively charged penetratin and transportan in a wide range of concentrations (2.5-320 µg/kg) caused highly significant transient decrease in the systolic and diastolic blood pressure in a dose dependent manner (p<0.01). Pretreatment with histamine receptors blockers or with cromolyn, a mast cell stabilizing agent, significantly attenuated this effect. Furthermore, in vitro incubation of these both peptides with mast cells line, LAD2, caused a massive mast cell degranulation. In vitro studies showed that these CPP in a wide range of concentrations were not cytotoxic without any effect on the survival of LAD2 mast cell line. In contrast, the less positively charged and proline-rich CPP, pro-rich, had no systemic effects with no effect on mast cell degranulation. Our results indicate that intravenously administrated positively charged CPP may have deleterious consequences due to their induced BP drop, mediated by mast cell activation. Therefore, the major effect of mast cell activation on BP should be considered in developing possible future drug therapies based on the injection of membrane-permeable and positively charged CPP. Nevertheless, lower levels of such CPP may be considered as a treatment of systemic high BP through moderate systemic mast cell activation.

Efficient isolation and chondrogenic differentiation of adult mesenchymal stem cells with fibrin microbeads and micronized collagen sponges.

BACKGROUND: Mesenchymal stem cells (MSCs) have been demonstrated to potentially undergo chondrogenic differentiation. We propose a new matrix for stem cell-based chondrogenesis using dense fibrin microbeads (FMBs) combined with grounded dehydrothermally crosslinked collagen sponges (micronized collagen). METHODS: In this study, MSCs were isolated from bone marrow of transgenic green fluorescent protein C57/Bl mice by FMBs in high yield. After 48 h in slowly rotating suspension culture, micronized collagen was added. RESULTS: The cells on the FMBs migrated to the collagen pieces and formed aggregates that developed into cartilage-like structures. Following chondrogenic differentiation, alcian blue staining and collagen type II immunohistochemistry demonstrated the presence of chondrocytes in the 3D structures. PCR for the expression of aggrecan and collagen type II genes supported these findings. The in vitro structures that formed were used for ectopic subdermal implantation in wild-type C57/Bl mice. However, the chondrogenic markers faded relative to the pre-implant in vitro structures. CONCLUSION: We propose that FMBs with micronized collagen could serve as a simple technology for MSC isolation and chondrogenesis as a basis for implantation.

Isolation and implantation of bone marrow-derived mesenchymal stem cells with fibrin micro beads to repair a critical-size bone defect in mice.

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).

New cell attachment peptide sequences from conserved epitopes in the carboxy termini of fibrinogen.

Fibrinogen seems to contribute significantly to cell binding and recruitment into wounds besides its major role in clot formation. We describe 19- to 21-mer cell-binding (haptotactic) peptides from the C-termini of fibrinogen beta-chain (Cbeta), the extended alphaE chain, and near the C-terminal of the gamma-chain. When these peptides were covalently bound to a biologically inert matrix such as Sepharose beads (SB), they elicited beads attachment to cells, mostly of mesenchymal origin (including fibroblasts, endothelial cells, and smooth muscle cells) as well as some transformed cell lines. Based on such haptotactic activity, these peptides were termed "haptides." By contrast, peptides homologous to fibrinogen C-termini alpha- and gamma-chains elicited no such activity. The haptide Cbeta could not block the interaction of fibroblasts with antibodies directed against integrins beta(1), alpha(v), alpha(v)beta(1), alpha(v)beta(3), and alphaIIbeta(3). Moreover, GRGDS peptide could not inhibit enhanced cell binding to SB-Cbeta, as expected from an integrin-mediated process. In soluble form the haptides were accumulated in cells with nonsaturable kinetics without any toxic or proproliferative effects in concentrations up to 80 microM. These findings suggest that the conserved haptidic sequences within fibrin(ogen) can be associated with the adhesion and migration of cells into fibrin clots and may have a significant role in normal wound healing and in various pathological conditions.