A novel FIP1L1-PDGFRA mutant destabilizing the inactive conformation of the kinase domain in chronic eosinophilic leukemia/hypereosinophilic syndrome

BACKGROUND: The Fip1-like-1-platelet-derived growth factor receptor alpha (FIP1L1-PDGFRA) gene fusion is a common cause of chronic eosinophilic leukemia (CEL)/hypereosinophilic syndrome (HES), and patients suffering from this particular subgroup of CEL/HES respond to low-dose imatinib therapy. However, some patients may develop imatinib resistance because of an acquired T674I mutation, which is believed to prevent drug binding through steric hindrance. METHODS: In an imatinib resistant FIP1L1-PDGFRA positive patient, we analyzed the molecular structure of the fusion gene and analyzed the effect of several kinase inhibitors on FIP1L1-PDGFRA-mediated proliferative responses in vitro. RESULTS: Sequencing of the FIP1L1-PDGFRA fusion gene revealed the occurrence of a S601P mutation, which is located within the nucleotide binding loop. In agreement with the clinical observations, imatinib did not inhibit the proliferation of S601P mutant FIP1L1-PDGFRA-transduced Ba/F3 cells. Moreover, sorafenib, which has been described to inhibit T674I mutant FIP1L1-PDGFRA, failed to block S601P mutant FIP1L1-PDGFRA. Structural modeling revealed that the newly identified S601P mutated form of PDGFRA destabilizes the inactive conformation of the kinase domain that is necessary to bind imatinib as well as sorafenib. CONCLUSIONS: We identified a novel mutation in FIP1L1-PDGFRA resulting in both imatinib and sorafenib resistance. The identification of novel drug-resistant FIP1L1-PDGFRA variants may help to develop the next generation of target-directed compounds for CEL/HES and other leukemias.

Hypereosinophilic syndrome: a multicenter, retrospective analysis of clinical characteristics and response to therapy

BACKGROUND: Hypereosinophilic syndrome (HES) is a heterogeneous group of rare disorders defined by persistent blood eosinophilia > or =1.5 x 10(9)/L, absence of a secondary cause, and evidence of eosinophil-associated pathology. With the exception of a recent multicenter trial of mepolizumab (anti-IL-5 mAb), published therapeutic experience has been restricted to case reports and small case series. OBJECTIVE: The purpose of the study was to collect and summarize baseline demographic, clinical, and laboratory characteristics in a large, diverse cohort of patients with HES and to review responses to treatment with conventional and novel therapies. METHODS: Clinical and laboratory data from 188 patients with HES, seen between January 2001 and December 2006 at 11 institutions in the United States and Europe, were collected retrospectively by chart review. RESULTS: Eighteen of 161 patients (11%) tested were Fip1-like 1-platelet-derived growth factor receptor alpha (FIP1L1-PDGFRA) mutation-positive, and 29 of 168 patients tested (17%) had a demonstrable aberrant or clonal T-cell population. Corticosteroid monotherapy induced complete or partial responses at 1 month in 85% (120/141) of patients with most remaining on maintenance doses (median, 10 mg prednisone equivalent daily for 2 months to 20 years). Hydroxyurea and IFN-alpha (used in 64 and 46 patients, respectively) were also effective, but their use was limited by toxicity. Imatinib (used in 68 patients) was more effective in patients with the FIP1L1-PDGFRA mutation (88%) than in those without (23%; P < .001). CONCLUSION: This study, the largest clinical analysis of patients with HES to date, not only provides useful information for clinicians but also should stimulate prospective trials to optimize treatment of HES.

Development of a bead-based multiplex assay for the simultaneous detection of porcine inflammation markers using xMAP technology

Commercially available assays for the simultaneous detection of multiple inflammatory and cardiac markers in porcine blood samples are currently lacking. Therefore, this study was aimed at developing a bead-based, multiplexed flow cytometric assay to simultaneously detect porcine cytokines [interleukin (IL)-1β, IL-6, IL-10, and tumor necrosis factor alpha], chemokines (IL-8 and monocyte chemotactic protein 1), growth factors [basic fibroblast growth factor (bFGF), vascular endothelial growth factor, and platelet-derived growth factor-bb], and injury markers (cardiac troponin-I) as well as complement activation markers (C5a and sC5b-9). The method was based on the Luminex xMAP technology, resulting in the assembly of a 6- and 11-plex from the respective individual singleplex situation. The assay was evaluated for dynamic range, sensitivity, cross-reactivity, intra-assay and interassay variance, spike recovery, and correlation between multiplex and commercially available enzyme-linked immunosorbent assay as well as the respective singleplex. The limit of detection ranged from 2.5 to 30,000 pg/ml for all analytes (6- and 11-plex assays), except for soluble C5b-9 with a detection range of 2-10,000 ng/ml (11-plex). Typically, very low cross-reactivity (<3% and <1.4% by 11- and 6-plex, respectively) between analytes was found. Intra-assay variances ranged from 4.9 to 7.4% (6-plex) and 5.3 to 12.9% (11-plex). Interassay variances for cytokines were between 8.1 and 28.8% (6-plex) and 10.1 and 26.4% (11-plex). Correlation coefficients with singleplex assays for 6-plex as well as for 11-plex were high, ranging from 0.988 to 0.997 and 0.913 to 0.999, respectively. In this study, a bead-based porcine 11-plex and 6-plex assay with a good assay sensitivity, broad dynamic range, and low intra-assay variance and cross-reactivity was established. These assays therefore represent a new, useful tool for the analysis of samples generated from experiments with pigs.

Study of the cellular mechanism of Sunitinib mediated inactivation of activated hepatic stellate cells and its implications in angiogenesis

The development of hepatocellular carcinomas from malignant hepatocytes is frequently associated with intra- and peritumoral accumulation of connective tissue arising from activated hepatic stellate cells (HSC). Inhibition of receptor tyrosine kinase (RTK) signaling showed promise in the treatment of hepatocellular carcinoma. However, there is a lack of knowledge about the effects of RTK inhibitors on the tumor supportive cells. We performed in vitro experiments to study whether Sunitinib, a platelet-derived growth factor (PDGF) and vascular endothelial growth factor (VEGF) RTKs' inhibitor, could block both activated HSC functions and angiogenesis and thus prevent the progression of cirrhotic liver to hepatocellular carcinoma. In immortalized human activated HSC LX-2, treatment with Sunitinib 100 nM blocked collagen synthesis by 47%, as assessed by Sirius Red staining, attenuated HSC contraction by 65%, and reduced cell migration by 28% as evaluated using a Boyden's chamber, without affecting cell viability, measured by Trypan blue staining, and apoptosis, measured by propidium iodide (PI) incorporation assay. Our data revealed that Sunitinib treatment blocked the transdifferentiation of primary human HSC (hHSC) to activated myofibroblast-like cells by 65% without affecting hHSC apoptosis and migration. In in vitro angiogenic assays, Sunitinib 100 nM reduced endothelial cells (EC) ring formation by 46% and tube formation by 68%, and decreased vascular sprouting in aorta ring assay and angiogenesis in vascular bed of chick embryo. In conclusion, the present study demonstrates that the RTK inhibitor Sunitinib blocks the activation of HSC and angiogenesis suggesting its potential as a drug candidate in pathological conditions like liver fibrosis and hepatocellular carcinoma.

Split for the cure: VEGF, PDGF-BB and intussusception in therapeutic angiogenesis

Therapeutic angiogenesis is an attractive strategy to treat patients suffering from ischaemic conditions and vascular endothelial growth factor-A (VEGF) is the master regulator of blood vessel growth. However, VEGF can induce either normal or aberrant angiogenesis depending on its dose localized in the microenvironment around each producing cell in vivo and on the balanced stimulation of platelet-derived growth factor-BB (PDGF-BB) signalling, responsible for pericyte recruitment. At the doses required to induce therapeutic benefit, VEGF causes new vascular growth essentially without sprouting, but rather through the alternative process of intussusception, or vascular splitting. In the present article, we briefly review the therapeutic implications of controlling VEGF dose on one hand and pericyte recruitment on the other, as well as the key features of intussusceptive angiogenesis and its regulation.

Refinement of tourniquet-induced peripheral ischemia/reperfusion injury in rats: comparison of 2 h vs 24 h reperfusion.

Prolonged ischemia of skeletal muscle tissue, followed by reperfusion, leads to ischemia/reperfusion injury (IRI), which is a feared local and systemic inflammatory reaction. With respect to the 3Rs, we wanted to determine which parameters for assessment of IRI require a reperfusion time of 24 h and for which 2 h of reperfusion are sufficient. Rats were subjected to 3 h of hind limb ischemia and 2 h or 24 h of reperfusion. Human plasma derived C1 inhibitor was used as a drug to prevent reperfusion injury. For 2 h of reperfusion the rats stayed under anesthesia throughout (severity grade 1), whereas for 24 h they were awake under analgesia during reperfusion (grade 2). The femoral artery was clamped and a tourniquet was placed, under maintenance of venous return. C1 esterase inhibitor was systemically administered 5 min before the induction of ischemia. No differences in local muscle edema formation and depositions of immunoglobulin G and immunoglobulin M were observed between 2 h and 24 h (P > 0.05), whereas lung edema was only observed after 24 h. Muscle viability was significantly lower after 24 h vs 2 h reperfusion (P < 0.05). Increased plasma creatine kinase (CK)-MM and platelet-derived growth factor (PDGF)-bb could be detected after 2 h, but not after 24 h of reperfusion. By contrast, depositions of C3b/c and fibrin in muscle were only detected after 24 h (P < 0.001). In conclusion, for a first screening of drug candidates to reduce IRI, 2 h reperfusions are sufficient, and these reduce the severity of the animal experiment. Twenty-four-hour reperfusions are only needed for in-depth analysis of the mechanisms of IRI, including lung damage.

Spatio-temporal co-ordination of RhoA, Rac1 and Cdc42 activation during prototypical edge protrusion and retraction dynamics

The three canonical Rho GTPases RhoA, Rac1 and Cdc42 co-ordinate cytoskeletal dynamics. Recent studies indicate that all three Rho GTPases are activated at the leading edge of motile fibroblasts, where their activity fluctuates at subminute time and micrometer length scales. Here, we use a microfluidic chip to acutely manipulate fibroblast edge dynamics by applying pulses of platelet-derived growth factor (PDGF) or the Rho kinase inhibitor Y-27632 (which lowers contractility). This induces acute and robust membrane protrusion and retraction events, that exhibit stereotyped cytoskeletal dynamics, allowing us to fairly compare specific morphodynamic states across experiments. Using a novel Cdc42, as well as previously described, second generation RhoA and Rac1 biosensors, we observe distinct spatio-temporal signaling programs that involve all three Rho GTPases, during protrusion/retraction edge dynamics. Our results suggest that Rac1, Cdc42 and RhoA regulate different cytoskeletal and adhesion processes to fine tune the highly plastic edge protrusion/retraction dynamics that power cell motility.

Leukocyte- and Platelet-Rich Fibrin (L-PRF) for Long-Term Delivery of Growth Factor in Rotator Cuff Repair: Review, Preliminary Results and Future Directions

Surgical repair of the rotator cuff repair is one of the most common procedures in orthopedic surgery. Despite it being the focus of much research, the physiological tendon-bone insertion is not recreated following repair and there is an anatomic non-healing rate of up to 94%. During the healing phase, several growth factors are upregulated that induce cellular proliferation and matrix deposition. Subsequently, this provisional matrix is replaced by the definitive matrix. Leukocyte- and platelet-rich fibrin (L-PRF) contain growth factors and has a stable dense fibrin matrix. Therefore, use of LPRF in rotator cuff repair is theoretically attractive. The aim of the present study was to determine 1) the optimal protocol to achieve the highest leukocyte content; 2) whether L-PRF releases growth factors in a sustained manner over 28 days; 3) whether standard/gelatinous or dry/compressed matrix preparation methods result in higher growth factor concentrations. 1) The standard L-PRF centrifugation protocol with 400 x g showed the highest concentration of platelets and leukocytes. 2) The L-PRF clots cultured in medium showed a continuous slow release with an increase in the absolute release of growth factors TGF-β1, VEGF and MPO in the first 7 days, and for IGF1, PDGF-AB and platelet activity (PF4=CXCL4) in the first 8 hours, followed by a decrease to close to zero at 28 days. Significantly higher levels of growth factor were expressed relative to the control values of normal blood at each culture time point. 3) Except for MPO and the TGFβ-1, there was always a tendency towards higher release of growth factors (i.e., CXCL4, IGF-1, PDGF-AB, and VEGF) in the standard/gelatinous- compared to the dry/compressed group. L-PRF in its optimal standard/gelatinous-type matrix can store and deliver locally specific healing growth factors for up to 28 days and may be a useful adjunct in rotator cuff repair.

Platelet released growth factors boost expansion of bone marrow derived CD34(+) and CD133(+) endothelial progenitor cells for autologous grafting

Stem cell based autologous grafting has recently gained mayor interest in various surgical fields for the treatment of extensive tissue defects. CD34(+) and CD133(+) cells that can be isolated from the pool of bone marrow mononuclear cells (BMC) are capable of differentiating into mature endothelial cells in vivo. These endothelial progenitor cells (EPC) are believed to represent a major portion of the angiogenic regenerative cells that are released from bone marrow when tissue injury has occurred. In recent years tissue engineers increasingly looked at the process of vessel neoformation because of its major importance for successful cell grafting to replace damaged tissue. Up to now one of the greatest problems preventing a clinical application is the large scale of expansion that is required for such purpose. We established a method to effectively enhance the expansion of CD34(+) and CD133(+) cells by the use of platelet-released growth factors (PRGF) as a media supplement. PRGF were prepared from thrombocyte concentrates and used as a media supplement to iscove's modified dulbecco's media (IMDM). EPC were immunomagnetically separated from human bone morrow monocyte cells and cultured in IMDM + 10% fetal calf serum (FCS), IMDM + 5%, FCS + 5% PRGF and IMDM + 10% PRGF. We clearly demonstrate a statistically significant higher and faster cell proliferation rate at 7, 14, 21, and 28 days of culture when both PRGF and FCS were added to the medium as opposed to 10% FCS or 10% PRGF alone. The addition of 10% PRGF to IMDM in the absence of FCS leads to a growth arrest from day 14 on. In histochemical, immunocytochemical, and gene-expression analysis we showed that angiogenic and precursor markers of CD34(+) and CD133(+) cells are maintained during long-term culture. In summary, we established a protocol to boost the expansion of CD34(+) and CD133(+) cells. Thereby we provide a technical step towards the clinical application of autologous stem cell transplantation.

Prolyl hydroxylase inhibitors increase the production of vascular endothelial growth factor in dental pulp-derived cells

Introduction: Prolyl hydroxylase (PHD) inhibitors can induce a proangiogenic response that stimulates regeneration in soft and hard tissues. However, the effect of PHD inhibitors on the dental pulp is unclear. The purpose of this study was to evaluate the effects of PHD inhibitors on the proangiogenic capacity of human dental pulp–derived cells. Methods: To test the response of dental pulp–derived cells to PHD inhibitors, the cells were exposed to dimethyloxalylglycine, desferrioxamine, L-mimosine, and cobalt chloride. To assess the response of dental pulp cells to a capping material supplemented with PHD inhibitors, the cells were treated with supernatants from calcium hydroxide. Viability, proliferation, and protein synthesis were assessed by formazan formation, 3[H]thymidine, and 3[H]leucine incorporation assays. The effect on the proangiogenic capacity was measured by immunoassays for vascular endothelial growth factor (VEGF). Results: We found that all 4 PHD inhibitors can reduce viability, proliferation, and protein synthesis at high concentrations. At nontoxic concentrations and in the presence of supernatants from calcium hydroxide, PHD inhibitors stimulated the production of VEGF in dental pulp–derived cells. When calcium hydroxide was supplemented with the PHD inhibitors, the supernatants from these preparations did not significantly elevate VEGF levels. Conclusions: These results show that PHD inhibitors can stimulate VEGF production of dental pulp–derived cells, suggesting a corresponding increase in their proangiogenic capacity. Further studies will be required to understand the impact that this might have on pulp regeneration.

Placental growth factor-1 attenuates vascular endothelial growth factor-A-dependent tumor angiogenesis during beta cell carcinogenesis

Members of the vascular endothelial growth factor (VEGF) family are critical players in angiogenesis and lymphangiogenesis. Although VEGF-A has been shown to exert fundamental functions in physiologic and pathologic angiogenesis, the exact role of the VEGF family member placental growth factor (PlGF) in tumor angiogenesis has remained controversial. To gain insight into PlGF function during tumor angiogenesis, we have generated transgenic mouse lines expressing human PlGF-1 in the beta cells of the pancreatic islets of Langerhans (Rip1PlGF-1). In single-transgenic Rip1PlGF-1 mice, intra-insular blood vessels are found highly dilated, whereas islet physiology is unaffected. Upon crossing of these mice with the Rip1Tag2 transgenic mouse model of pancreatic beta cell carcinogenesis, tumors of double-transgenic Rip1Tag2;Rip1PlGF-1 mice display reduced growth due to attenuated tumor angiogenesis. The coexpression of transgenic PlGF-1 and endogenous VEGF-A in the beta tumor cells of double-transgenic animals causes the formation of low-angiogenic hPlGF-1/mVEGF-A heterodimers at the expense of highly angiogenic mVEGF-A homodimers resulting in diminished tumor angiogenesis and reduced tumor infiltration by neutrophils, known to contribute to the angiogenic switch in Rip1Tag2 mice. The results indicate that the ratio between the expression levels of two members of the VEGF family of angiogenic factors, PlGF-1 and VEGF-A, determines the overall angiogenic activity and, thus, the extent of tumor angiogenesis and tumor growth.

Role of hypoxia and growth and differentiation factor-5 on differentiation of human mesenchymal stem cells towards intervertebral nucleus pulposus-like cells

There is evidence that mesenchymal stem cells (MSCs) can differentiate towards an intervertebral disc (IVD)-like phenotype. We compared the standard chondrogenic protocol using transforming growth factor beta-1 (TGFß) to the effects of hypoxia, growth and differentiation factor-5 (GDF5), and coculture with bovine nucleus pulposus cells (bNPC). The efficacy of molecules recently discovered as possible nucleus pulposus (NP) markers to differentiate between chondrogenic and IVD-like differentiation was evaluated. MSCs were isolated from human bone marrow and encapsulated in alginate beads. Beads were cultured in DMEM (control) supplemented with TGFß or GDF5 or under indirect coculture with bNPC. All groups were incubated at low (2 %) or normal (20 %) oxygen tension for 28 days. Hypoxia increased aggrecan and collagen II gene expression in all groups. The hypoxic GDF5 and TGFß groups demonstrated most increased aggrecan and collagen II mRNA levels and glycosaminoglycan accumulation. Collagen I and X were most up-regulated in the TGFß groups. From the NP markers, cytokeratin-19 was expressed to highest extent in the hypoxic GDF5 groups; lowest expression was observed in the TGFß group. Levels of forkhead box F1 were down-regulated by TGFß and up-regulated by coculture with bNPC. Carbonic anhydrase 12 was also down-regulated in the TGFß group and showed highest expression in the GDF5 group cocultured with bNPC under hypoxia. Trends in gene expression regulation were confirmed on the protein level using immunohistochemistry. We conclude that hypoxia and GDF5 may be suitable for directing MSCs towards the IVD-like phenotype.

Controlled angiogenesis in the heart by cell-based expression of specific vascular endothelial growth factor levels

Vascular endothelial growth factor (VEGF) can induce normal angiogenesis or the growth of angioma-like vascular tumors depending on the amount secreted by each producing cell because it remains localized in the microenvironment. In order to control the distribution of VEGF expression levels in vivo, we recently developed a high-throughput fluorescence-activated cell sorting (FACS)-based technique to rapidly purify transduced progenitors that homogeneously express a specific VEGF dose from a heterogeneous primary population. Here we tested the hypothesis that cell-based delivery of a controlled VEGF level could induce normal angiogenesis in the heart, while preventing the development of angiomas. Freshly isolated human adipose tissue-derived stem cells (ASC) were transduced with retroviral vectors expressing either rat VEGF linked to a FACS-quantifiable cell-surface marker (a truncated form of CD8) or CD8 alone as control (CTR). VEGF-expressing cells were FACS-purified to generate populations producing either a specific VEGF level (SPEC) or uncontrolled heterogeneous levels (ALL). Fifteen nude rats underwent intramyocardial injection of 10(7) cells. Histology was performed after 4 weeks. Both the SPEC and ALL cells produced a similar total amount of VEGF, and both cell types induced a 50%-60% increase in both total and perfused vessel density compared to CTR cells, despite very limited stable engraftment. However, homogeneous VEGF expression by SPEC cells induced only normal and stable angiogenesis. Conversely, heterogeneous expression of a similar total amount by the ALL cells caused the growth of numerous angioma-like structures. These results suggest that controlled VEGF delivery by FACS-purified ASC may be a promising strategy to achieve safe therapeutic angiogenesis in the heart.

Cause or effect of arteriogenesis: compositional alterations of microparticles from CAD patients undergoing external counterpulsation therapy

Recently, a clinical study on patients with stable coronary artery disease (CAD) showed that external counterpulsation therapy (ECP) at high (300 mmHg) but not at low inflation pressure (80 mmHg) promoted coronary collateral growth, most likely due to shear stress-induced arteriogenesis. The exact molecular mechanisms behind shear stress-induced arteriogenesis are still obscure. We therefore characterized plasma levels of circulating microparticles (MPs) from these CAD patients because of their ambivalent nature as a known cardiovascular risk factor and as a promoter of neovascularization in the case of platelet-derived MPs. MPs positive for Annexin V and CD31CD41 were increased, albeit statistically significant (P<0.05, vs. baseline) only in patients receiving high inflation pressure ECP as determined by flow cytometry. MPs positive for CD62E, CD146, and CD14 were unaffected. In high, but not in low, inflation pressure treatment, change of CD31CD41 was inversely correlated to the change in collateral flow index (CFI), a measure for collateral growth. MPs from the high inflation pressure group had a more sustained pro-angiogenic effect than the ones from the low inflation pressure group, with the exception of one patient showing also an increased CFI after treatment. A total of 1005 proteins were identified by a label-free proteomics approach from MPs of three patients of each group applying stringent acceptance criteria. Based on semi-quantitative protein abundance measurements, MPs after ECP therapy contained more cellular proteins and increased CD31, corroborating the increase in MPs. Furthermore, we show that MP-associated factors of the innate immune system were decreased, many membrane-associated signaling proteins, and the known arteriogenesis stimulating protein transforming growth factor beta-1 were increased after ECP therapy. In conclusion, our data show that ECP therapy increases platelet-derived MPs in patients with CAD and that the change in protein cargo of MPs is likely in favor of a pro angiogenic/arteriogenic property.

An in vivo study of a growth-factor enhanced, cell free, two-layered collagen-tricalcium phosphate in deep osteochondral defects

Focal osteochondral defects are still a challenging problem in joint surgery. We have developed a two-layered implant consisting of a basal porous beta-tricalcium phosphate (TCP) for bone reconstruction and a superficial fibrous collagen type I/III layer for cartilage regeneration. Fifty-four osteochondral defects in the trochlear groove of 27 Göttinger Minipigs were created and either left untreated, treated with the implant alone, or the implant augmented with an additional growth factor mixture, which was assumed to stimulate cell and tissue differentiation. Follow-up was 6, 12 and 52 weeks with n=6 for each group. The repair tissue was evaluated for its gross appearance and biomechanical properties. Histological sections were semi-quantitatively scored for their histomorphological structure. Treatment with the two-layered implant improved defect filling and subchondral bone repair at 6 and 12 weeks follow-up. The TCP was replaced by cancellous bone at 52 weeks. Cartilage repair tissue mainly consisted of fibrocartilage and showed a moderate cell density up to the joint surface. Growth factor treatment improved the mechanical and histomorphological properties of the cartilage repair tissue at 12, but not at 52 weeks postoperatively. In conclusion, the two-layered collagen-TCP implant augmented with chondroinductive growth factors seems a promising new option for the treatment of deep osteochondral defects in joint surgery.