Bone and bone marrow interactions: hematological activity of osteoblastic growth peptide (OGP)-derived carboxy-terminal pentapeptide. II. Action on human hematopoietic stem cells

A CD10-OGP Membrane Peptolytic Signaling Axis in Fibroblasts Regulates Lipid Metabolism of Cancer Stem Cells via SCD1

Carcinoma-associated fibroblasts (CAFs) consist of heterogeneous subpopulations that play a critical role in the dynamics of the tumor microenvironment. The extracellular signals of CAFs have been attributed to the extracellular matrix, cytokines, cell surface checkpoints, and exosomes. In the present study, it is demonstrated that the CD10 transmembrane hydrolase expressed on a subset of CAFs supports tumor stemness and induces chemoresistance. Mechanistically, CD10 degenerates an antitumoral peptide termed osteogenic growth peptide (OGP). OGP restrains the expression of rate-limiting desaturase SCD1 and inhibits lipid desaturation, which is required for cancer stem cells (CSCs). Targeting CD10 significantly improves the efficacy of chemotherapy in vivo. Clinically, CD10-OGP signals are associated with the response to neoadjuvant chemotherapy in patients with breast cancer. The collective data suggest that a nexus between the niche and lipid metabolism in CSCs is a promising therapeutic target for breast cancer.

Mesenchymal Stem Cells on Plasma-Deposited Acrylic Acid Coatings: An In Vitro Investigation to Improve Biomaterial Performance in Bone Reconstruction

In this in vitro investigation of a heterogeneous range of bio-functional and modulatory performances of mesenchymal stem cells (MSCs) grown on two plasma-deposited acrylic acid (pdAA) coatings, which differed in chemical characteristics, a view of their potential utility as hybrid scaffolds for bone tissue engineering was obtained. The in vitro behavior of MSCs was compared to that of MG-63 cells, an osteoblast-like cell line that is commonly used to test biocompatibility of materials intended for bone-tissue interface. The coatings exerted a greater stimulus on MSCs and on MG-63 cells in comparison with control cultures. Both studied coatings exhibited satisfactory compatibility and modulatory effects on MSCs, thus they may be suitable for use in 2D or 3D scaffolds for bone tissue reconstruction.

The small peptide OGP(10-14) reduces proliferation and induces differentiation of TPO-primed M07-e cells through RhoA/TGFbeta1/SFK pathway

Background

Osteogenic growth peptide (OGP) is a 14-mer peptide found in relevant concentration in blood, and its carboxy-terminal fragment [OGP(10-14)] represents the active portion of the full-length peptide. In addition to stimulating bone formation, OGP(10-14) shows hematological activity. In fact, it highly enhances hematopoiesis-affecting stem progenitors. Moreover, OGP(10-14) reduces the growth and induces the differentiation of the hematological tumour cell line trombophoietin(TPO)-primed M07-e by interfering with RhoA and Src kinase pathways. In the present report, we went deeper into this mechanism and evaluated the possible interference of the OGP(10-14) signal pathway with TGFβ1 and TPO receptor Mpl.

Material/Methods

In OGP(10-14)-treated M07-e cells cultured with or without RhoA and Src kinases inhibitors (C3 and PP2), expression of TGFβ1, Mpl, and Src kinases was analyzed by immunoperoxidase technique. Activated RhoA expression was studied using the G-LISA™ quantitative test.

Results

In M07-e cells, both OGP(10-14) and PP2 activate RhoA, inhibit Src kinases, reduce Mpl expression and increase TGFβ1 expression. OGP(10-14) and PP2 show the same behavior, causing an additive effect when associated.

Conclusions

OGP(10-14) induces TPO-primed M07-e cells differentiation through RhoA/TGFβ1/SFKs signalling pathway. In particular OGP(10-14) acts as a Src inhibitor, showing the same effects of PP2.

C-terminal pentapeptide of osteogenic growth peptide regulates hematopoiesis in early stage

Osteogenic growth peptide (OGP) was characterized in regenerating bone marrow, which can increase osteogenesis and hematopoiesis. The carboxy-terminal pentapeptide is a naturally occurring human and murine mitogen equipotent to OGP. In this study, we evaluated the potential role of OGP10-14 in regulation of hematopoiesis in human hematopoietic stem cells and animal model. Our results showed CD34+ stem cells from umbilical cord blood (UBC) were significantly increased in OGP10-14 treated samples, which is nearly equivalent to the results obtained from the combinations of IL3, IL11, G-CSF, and EPO group. OGP10-14 can also stimulate the differentiation of stem cells from bone marrow at the level of noncommitted progenitor stem cells, thus increasing the number of reconstituted red and white cells as well as platelets after injected i.m. everyday continuing for 5 days in hematopoietic function damage mice comparing with the OGP-untreated group. These data implicate that the role of OGP10-14 regulating hematopoiesis is in the early stage of the whole hematopoietic growth factors (HGFs) regulating network, just like the position of interleukin 13 in the hematopoiesis network.

Osteogenic growth peptide effects on primary human osteoblast cultures: potential relevance for the treatment of glucocorticoid-induced osteoporosis

The osteogenic growth peptide (OGP) is a naturally occurring tetradecapeptide that has attracted considerable clinical interest as a bone anabolic agent and hematopoietic stimulator. In vivo studies on animals have demonstrated that the synthetic peptide OGP (10-14), reproducing the OGP C-terminal active portion [H-Tyr-Gly-Phe-Gly-Gly-OH] increases bone formation, trabecular bone density and fracture healing. In vitro studies performed on cellular systems based on osteoblastic-like cell lines or mouse stromal cells, have demonstrated that OGP (10-14) increases osteoblast proliferation, alkaline phosphatase (ALKP) activity and matrix synthesis and mineralization. In view of a potential application of OGP (10-14) in clinical therapy, we have tested different concentrations of OGP (10-14) on primary human osteoblast (hOB) cultures. We have observed significant increases of hOB proliferation (+35%), ALKP activity (+60%), osteocalcin secretion (+50%), and mineralized nodules formation (+49%). Our experimental model based on mature hOBs was used to investigate if OGP (10-14) could prevent the effects on bone loss induced by sustained glucocorticoid (GC) treatments. A strong decrease in bone formation has been attributed to the effects of GCs on osteoblastogenesis and osteocyte apoptosis, while an increase in bone resorption was due to a transient osteoblastic stimulation, mediated by the OPG/RANKL/RANK system, of osteoclasts recruitment and activation. Moreover, GCs act on hOBs decreasing the release of osteoprotegerin (OPG) a regulator of the RANKL/RANK interaction. Here, we provide evidences that OGP (10-14) inhibits hOB apoptosis induced by an excess of dexamethasone (-48% of apoptotic cells). Furthermore, we show that OGP (10-14) can increase OPG secretion (+20%) and can restore the altered expression of OPG induced by GCs to physiological levels. Our results support the employment of OGP (10-14) in clinical trials addressed to the treatment of different bone remodeling alterations including the GC-induced osteoporosis.

Carboxy-terminal fragment of osteogenic growth peptide regulates myeloid differentiation through RhoA

The carboxy-terminal fragment of osteogenic growth peptide, OGP(10-14), is a pentapeptide with bone anabolic effects and hematopoietic activity. The latter activity appears to be largely enhanced by specific growth factors. To study the direct activity of OGP(10-14) on myeloid cells, we tested the pentapeptide proliferating/differentiating effects in HL60 cell line. In this cell line, OGP(10-14) significantly inhibited cell proliferation, and enhanced myeloperoxidase (MPO) activity and nitroblue tetrazolium reducing ability. Moreover, it induced cytoskeleton remodeling and small GTP-binding protein RhoA activation. RhoA, which is known to be involved in HL60 differentiation, mediated these effects as shown by using its specific inhibitor, C3. Treatment with GM-CSF had a comparable OGP(10-14) activity on proliferation, MPO expression, and RhoA activation. Further studies on cell proliferation and RhoA activation proved enhanced activity by association of the two factors. These results strongly suggest that OGP(10-14) acts directly on HL60 cells by activating RhoA signaling although other possibilities cannot be ruled out.

Leaky ribosomal scanning in mammalian genomes: significance of histone H4 alternative translation in vivo

Like alternative splicing, leaky ribosomal scanning (LRS), which occurs at suboptimal translational initiation codons, increases the physiological flexibility of the genome by allowing alternative translation. Comprehensive analysis of 22 208 human mRNAs indicates that, although the most important positions relative to the first nucleotide of the initiation codon, −3 and +4, are usually such that support initiation (A₋₃ = 42%, G₋₃ = 36% and G₊₄ = 47%), only 37.4% of the genes adhere to the purine (R)₋₃/G₊₄ rule at both positions simultaneously, suggesting that LRS may occur in some of the remaining (62.6%) genes. Moreover, 12.5% of the genes lack both R₋₃ and G₊₄, potentially leading to sLRS. Compared with 11 genes known to undergo LRS, 10 genes with experimental evidence for high fidelity A₊₁T₊₂G₊₃ initiation codons adhered much more strongly to the R₋₃/G₊₄ rule. Among the intron-less histone genes, only the H3 genes adhere to the R₋₃/G₊₄ rule, while the H1, H2A, H2B and H4 genes usually lack either R₋₃ or G₊₄. To address in vivo the significance of the previously described LRS of H4 mRNAs, which results in alternative translation of the osteogenic growth peptide, transgenic mice were engineered that ubiquitously and constitutively express a mutant H4 mRNA with an A₊₁→T₊₁ mutation. These transgenic mice, in particular the females, have a high bone mass phenotype, attributable to increased bone formation. These data suggest that many genes may fulfill cryptic functions by LRS.

Bone and bone marrow interactions: hematological activity of osteoblastic growth peptide (OGP)-derived carboxy-terminal pentapeptide

The increase of megakaryocytes and platelets that characterizes essential thrombocythemia (ET) appears to be secondary to a deregulation of megakaryocytopoiesis. The carboxy-terminal fragment of osteogenic growth peptide (OGP10-14) promotes bone formation and hemopoiesis, while it inhibits megakaryocytopoiesis. In this paper we show that treatment with synthetic OGP10-14 (sOGP10-14) induces a significant reduction of mid and large colony-forming unit-megakaryocytes (CFU-Mk) in ET patients as well as in controls, and is associated with a significant inhibition of thrombopoietin (TPO)-primed MO-7e megakaryoblastic cells proliferation. These actions appear to be related to sOGP10-14 modulation of TGF-beta(1) synthesis and/or secretion, although a direct effect on TGF-beta receptor expression cannot be excluded.

Osteogenic growth peptide modulates fracture callus structural and mechanical properties

The osteogenic growth peptide (OGP) is a key factor in the mechanism of the systemic osteogenic response to local bone marrow injury. Recent histologic studies have shown that OGP enhances fracture healing in experimental animals. To assess the effect of systemically administered OGP on the biomechanical and quantitative structural properties of the fracture callus, the present study used an integrated approach to evaluate the early stages (up to 4 weeks) of healing of unstable mid-femoral fractures in rats, which included biomechanical, micro-computed tomographic (microCT) and histomorphometric measurements. During the first 3 weeks after fracture, all the quantitative microCT parameters increased in the OGP- and vehicle-treated animals alike. After 4 weeks, the volume of total callus, bony callus, and newly formed bone was approximately 20% higher in animals administered with OGP, consequent to a decrease in the controls. The 4-week total connectivity was 46% higher in the OGP-treated animals. At this time, bridging between the fracture ends by newly formed bone was observed predominantly in the OGP-treated fractures. After 3 and 4 weeks, the OGP-treated animals showed higher biomechanical toughness of the fracture callus as compared to the PBS controls. Significant correlations between structural and biomechanical parameters were restricted to the OGP-treated rats. These data imply that the osteogenic effect of OGP results in enhanced bridging across the fracture gap and consequently improved function of the fracture callus. Therefore, OGP and/or its derivatives are suggested as a potential therapy for the acceleration of bone regeneration in instances of fracture repair and perhaps other bone injuries.

Carboxy-terminal fragment of osteogenic growth peptide in vitro increases bone marrow cell density in idiopathic myelofibrosis

Idiopathic myelofibrosis (IMF) is a clonal stem cell disorder characterized by reactive fibrosis of bone marrow sustained by a complex cytokine network. At present, no efficacious therapy for this disease exists. Synthetic carboxy-terminal pentapeptide of osteogenic growth factor (sOGP10-14) can increase bone marrow cellularity and the number of haematopoietic colonies; this study evaluated the activity of sOGP10-14 in IMF. Fragments of bone marrow biopsies from patients affected by IMF were cultured with or without the addition of sOGP10-14. Cellular density was evaluated by image analysis, and transforming growth factor-beta1 (TGF-beta1) concentration was immunologically assayed in the supernatant of cultured bone marrow biopsies. The proliferation rate of the megakaryoblastic M07-e cell line, cultured in the presence of either granulocyte-macrophage colony stimulating factor or thrombopoietin (TPO), and with or without sOGP10-14, was evaluated. Megakaryocyte colony forming unit (CFU-Mk) assay was performed on bone marrow samples of IMF patients with or without sOGP10-14. After 14 d, bone marrow cellularity was significantly increased in samples cultured with the pentapeptide. Moreover, sOGP10-14 induced a significant increase of TGF-beta in culture supernatants. TPO-primed proliferation of M07-e was reduced by sOGP10-14, and the pentapeptide significantly reduced CFU-Mk on IMF bone-marrow-derived cells. sOGP10-14 increased ex vivo bone marrow cellularity in IMF. This action could be related to the megakaryocyte inhibition induced by the interference of this pentapeptide with growth factor activities. These findings suggest that a deficiency of osteoblast-related factors may play a role in bone marrow failure in IMF.