Methyl helicterate inhibits hepatic stellate cell activation through downregulating the ERK1/2 signaling pathway.

The present study was to investigate the inhibitory effect of methyl helicterate (MH) on hepatic stellate cells (HSC-T6), primarily elucidating the underlying mechanism of MH against liver fibrosis. HSC-T6 cells were activated by platelet-derived growth factor (PDGF) stimulation, and then the effects of MH on cell viability, cytomembrane integrity, colony, migration, apoptosis, and cell cycle were detected. Moreover, the regulative mechanism of MH on HSCs was investigated by detecting the activation of the extracellular signal-regulated kinase (ERK1/2) signaling pathway. The results showed that MH significantly inhibited HSC-T6 cell viability and proliferation in a concentration-dependent manner. It notably promoted the release of lactate dehydrogenase, destroying cell membrane integrity. MH also markedly inhibited HSC-T6 cell clonogenicity and migration. Moreover, MH treatment significantly induced cell apoptosis and arrested cell cycle at the G2 phase. The further study showed that MH inhibited the expression of ERK1, ERK2, c-fos, c-myc, and Ets-1, blocking the ERK1/2 pathway. In conclusion, this study demonstrates that MH significantly inhibits HSC activation and promotes cell apoptosis via downregulation of the ERK1/2 signaling pathway.

Assessment of platelet-derived growth factor using A splinted full thickness dermal wound model in bearded dragons (Pogona vitticeps).

Wounds in reptiles are a common reason for presentation to a veterinarian. At this time there is limited information on effective topical medications to aid in wound closure. The objectives of this study were to translate the splinted, full-thickness dermal wound model, validated in mice, to the bearded dragon (Pogona vitticeps) and to determine the effect of topical becaplermin (BP), a platelet-derived growth factor (0.01%), on the rate of wound closure. Ten bearded dragons were anesthetized and two full-thickness cutaneous wounds were made on the dorsum of each lizard. Encircling splints were applied surrounding each wound and subsequently covered by a semi-occlusive dressing. Five lizards had one wound treated with BP and the adjacent wound treated with a vehicle control. Five additional lizards had one wound treated with saline and the second wound treated with a vehicle control. Wounds were imaged daily, and the wound area was measured using digital image analysis. The change in percentage wound closure over 17 days and the time to 50% wound closure was compared among the four treatment groups. There was no significant difference in wound closure rates between BP-treated and saline-treated wounds or in the time to 50% wound closure between any treatments. Vehicle-treated wounds adjacent to saline-treated wounds closed significantly slower than did BP (P < 0.010), saline (P < 0.001), and vehicle-treated wounds adjacent to BP-treated wounds (P < 0.013). Our preliminary study indicates that the splinted wound model, with modifications, may be used to determine wound closure rates in bearded dragons. When compared with saline, BP did not have a significant effect on wound closure rates, while the vehicle alone delayed wound closure. Histologic analysis of experimentally created wounds throughout the wound healing process is needed to further evaluate the effects of these treatments on reptile dermal wound healing.

Assessment of platelet growth factors in supernatants from rehydrated freeze-dried equine platelets and their effects on fibroblasts in vitro.

OBJECTIVE: To determine whether platelet growth factors are preserved in supernatants obtained from rehydrated trehalose-stabilized, freeze-dried (lyophilized) equine platelets and whether those growth factors stimulate fibroblast proliferation and migration and enhance fibroblast-associated contraction in a collagen gel assay. ANIMALS: 6 clinically normal adult horses. PROCEDURES: Blood samples were obtained from 6 horses, and washed platelets were prepared via differential centrifugation. Washed platelets were freeze-dried in a physiologic buffer with a mixture of trehalose and polyethylene glycol 4000. Rehydrated platelet supernatants and releasates prepared from fresh washed platelets stimulated with thrombin or platelet-activating factor were evaluated for transforming growth factor beta1 and platelet-derived growth factor-BB by use of ELISAs. Effects of rehydrated freeze-dried platelet supernatants on fibroblast proliferation, migration, and collagen gel contraction were compared with effects of 1%, 2.5%, or 10% fetal bovine serum (FBS). RESULTS: Supernatants from freeze-dried platelets contained similar amounts of growth factors as thrombin- and platelet-activating factor-stimulated platelet releasates. The supernatants significantly enhanced fibroblast proliferation and migration in a scratch assay, compared with FBS-free control or low (1%) FBS conditions. Additionally, supernatants from freeze-dried platelets enhanced contraction of fibroblast-seeded collagen gels, compared with the effect of 1% FBS. CONCLUSIONS AND CLINICAL RELEVANCE: The preparation technique preserved platelet growth factors, enhanced fibroblast proliferation and migration, and improved fibroblastseeded collagen gel contraction under conditions of low FBS concentration; these platelet supernatant preparations may prove useful as an aid to conventional wound management.

Dynamic assessment of fibroblast mechanical activity during Rac-induced cell spreading in 3-D culture.

The goal of this study was to determine the morphological and sub-cellular mechanical effects of Rac activation on fibroblasts within 3-D collagen matrices. Corneal fibroblasts were plated at low density inside 100 microm thick fibrillar collagen matrices and cultured for 1-2 days in serum-free media. Time-lapse imaging was then performed using Nomarski DIC. After an acclimation period, perfusion was switched to media containing PDGF. In some experiments, Y-27632 or blebbistatin were used to inhibit Rho-kinase (ROCK) or myosin II, respectively. PDGF activated Rac and induced cell spreading, which resulted in an increase in cell length, cell area, and the number of pseudopodial processes. Tractional forces were generated by extending pseudopodia, as indicated by centripetal displacement and realignment of collagen fibrils. Interestingly, the pattern of pseudopodial extension and local collagen fibril realignment was highly dependent upon the initial orientation of fibrils at the leading edge. Following ROCK or myosin II inhibition, significant ECM relaxation was observed, but small displacements of collagen fibrils continued to be detected at the tips of pseudopodia. Taken together, the data suggests that during Rac-induced cell spreading within 3-D matrices, there is a shift in the distribution of forces from the center to the periphery of corneal fibroblasts. ROCK mediates the generation of large myosin II-based tractional forces during cell spreading within 3-D collagen matrices, however residual forces can be generated at the tips of extending pseudopodia that are both ROCK and myosin II-independent.

Cost-effective management of recalcitrant diabetic foot ulcers.

The worldwide increase in prevalence of type 2 diabetes has resulted in a parallel increase in diabetic foot ulcers--a pervasive and significant problem associated with this disease [2]. Currently, an estimated 10.3 million people have been diagnosed with diabetes, while an additional estimated 5.4 million people with diabetes remain undiagnosed, representing a sixfold increase in the incidence of diabetes over the past four decades [9]. Approximately 15% (more than 2 million individuals, based on these estimates) of all people with diabetes will develop a lower-extremity ulcer during the course of the disease [10-12]. While most of these ulcers can be treated successfully on an outpatient basis, some will persist and become infected. Ultimately, between 14% and 20% of patients with lower-extremity diabetic ulcers will require amputation of the affected limb [13-15]. Diabetic foot ulcers can result in staggering financial burdens for both the healthcare system and the patient. For example, analysis of the 1995 Medicare claims revealed that lower-extremity ulcer care accounted for $1.45 billion in Medicare costs and contributed substantially to the high cost of care for diabetics, compared with Medicare costs for the general population [5]. Therapies that promote rapid and complete healing and reduce the need for expensive surgical procedures would impact these costs substantially. Results of this analysis suggest that becaplermin may ultimately be more cost-effective for the treatment of chronic diabetic foot ulcers than other treatment modalities, despite its higher initial dollar cost. This finding may be attributed to a combination of factors. First, expenses incurred in more prolonged treatment, such as office visits and the need for additional dressings, can be avoided when healing completes in a shorter period. Second, rapid and complete ulcer healing may reduce the incidence of significant morbidities (such as amputation or infection) and premature mortality; consequently, the financial burden associated with these complications would be reduced. Finally, the value of improved quality of life in patients with healed ulcers and the reduction in financial burden for patients who return to work cannot be ignored. These promising results warrant further investigation in larger controlled clinical studies to define more clearly the cost-effectiveness of becaplermin in this patient population.

Quantitative assessment of cerebral neocapillary network and its remodeling in mice using intravital fluorescence videomicroscopy.

To assess the responses of different growth factors on cerebral neocapillary density (NCD), cerebral angiogenesis was induced in mice using growth factors, basic fibroblast growth factor (bFGF) and platelet-derived growth factor (PDGF) at a concentration of 6 ng/ml each. Intravital fluorescence videomicroscopy was used to quantitatively evaluate microhemodynamic parameters such as diameter and red cell velocity. The gel-nylon mesh-sandwich system was implanted over the exposed cortex. After incubation for different periods of time (days 7, 14 or 28), fluorescein isothiocyanate (FITC)-labeled red cells were injected through a carotid artery and the neocapillaries on the upper surface of the nylon mesh were observed under a fluorescence videomicroscope. Based on the recorded videoimages, we evaluated the density, diameter and red cell velocity of the neocapillaries. The NCD in the bFGF group on day 7 was significantly higher than that in the PDGF group on day 7 (P < 0.01). The NCD (index) reached 100% on day 14, while it reduced significantly in both the groups on day 28. The neocapillary diameter was greater than that of the pre-existing capillaries on day 7. On day 14, a clear difference appeared in the capillary density between large and small vessels. The red cell velocity increased with the number of days after incubation. The response of cerebral neocapillaries to acetylcholine was measured after 28 days of incubation with growth factor bFGF and with PDGF. The red cell velocity increased significantly from its basal value in the PDGF group. These results suggest that the neocapillaries in the PDGF group matured earlier than those in the bFGF group.

Novel method for the quantitative assessment of cell migration: a study on the motility of rabbit anterior cruciate (ACL) and medial collateral ligament (MCL) cells.

A novel method of quantitating cell migration has been proposed for the potential utilization of tissue engineered scaffolds. Applying Alt's conservation law to describe the motion of first passage ACL and MCL cells, we have developed a quantitative method to assess innate differences in the motility of cells from these two ligamentous tissues. In this study, first passage ACL and MCL cells were cultured from four mature New Zealand white rabbits. One side of the cell monolayer was scraped completely away to create a wound model. The cell moved into the cell-free area, and cell density profiles were analyzed at 6 h and 12 h. Values of the random motility coefficient (mu) were then estimated by curve fitting the 6 h and 12 h data to a mathematical model, derived from the conservation law of cell flux. During 6 h of incubation in medium supplemented with 1% FBS, MCL cells (mu(MCL) = 4.63 +/- 0.65 X 10(-6) mm(2)/sec) were significantly (p < 0.05) more mobile than ACL cells (mu(ACL) = 2.51 +/- 0.31 X 10(-6) mm(2)/sec). At 12 h, the MCL cells also appeared to move faster (mu(ACL) = 4.39 +/- 0.63 X 10(-6) mm(2)/sec, mu(MCL) = 6.59 +/- 1.47 X 10(-6) mm(2)/sec), but the difference was not statistically significant (p = 0.18). Exposure of the cells to growth factors PDGF-BB or bFGF for 6 h had no significant effect on the migration of the ACL and MCL cells. However, exposure of the ACL cells (p < 0.05) and the MCL cells (p = 0.19) to 1 ng/mL of PDGFBB for 12 h enhanced their migration. Incubation with a high concentration (100 ng/mL) of PDGF-BB or bFGF at concentrations tested (1 or 100 ng/mL) for 12 h, produced little or no migratory stimulation on these ligament cells. Our findings support the previous qualitative observations made by numerous investigators. The novel methodology developed in this study may provide a basis for tissue engineering, and the results may be applied to tissue reconstruction techniques of the knee ligaments.

Original articles: ease of wound closure as an endpoint of treatment efficacy.

New treatments for chronic wounds require carefully performed clinical trials with significant endpoints. Total wound closure is the only endpoint currently accepted by the Food and Drug Administration. This study describes a scale that measures ease of wound closure and applies it to a four-arm prospectively randomized, blinded pressure ulcer trial of recombinant human platelet-derived growth factor-BB. Following validation of interrater reliability, 83 evaluable subjects' photographs were given a weekly ease of closure score by four raters blinded to treatment. The change of ease of closure score was correlated with the change of wound area and volume. Each ease of closure score was given a procedural cost. Results showed ease of closure did not directly correlate with either wound area or volume, suggesting that it was measuring additional information. The mean change in ease of closure score was 6 for subjects treated with 100 microg recombinant human platelet-derived growth factor-BB daily; 5 for those treated with 300 microg growth factor daily or 100 microg recombinant human platelet-derived growth factor-BB bid; and 4 for those treated with placebo. The cost savings ranged from $7200 for the group receiving 100 microg recombinant human platelet-derived growth factor-BB daily to $6300 for the controls. Outcomes in all 4 groups were significantly improved from their starting evaluation (p < 0.001). Based on this study, ease of closure is a verifiable endpoint that can be related to cost efficiency and may be a measure of efficacy.

PDGF-stimulated cyclic AMP formation in airway smooth muscle: assessment of the roles of MAP kinase, cytosolic phospholipase A2, and arachidonate metabolites.

Platelet-derived growth factor (PDGF) stimulates cyclic AMP (cAMP) synthesis in cultured guinea-pig airway smooth muscle (ASM) cells. However, this stimulation is normally countered by the action of cAMP phosphodiesterases. Thus, cAMP synthesis was observed only in cells pre-treated with either 3-isobutyl-1-methylxanthine (IBMX) or with cholera toxin. cAMP synthesis was inhibited by pre-treating cells with well-defined inhibitors of arachidonate metabolite synthesis, such as AACOCF3 [a cytosolic phospholipase A2 (cPLA2) inhibitor] and indomethacin (a cyclooxygenase inhibitor). This suggests that arachidonate metabolites (e.g., prostaglandins) released in response to PDGF stimulate cAMP synthesis. The presence of functional prostaglandin (PG) receptors was confirmed by experiments that showed that exogenous PGE2 stimulated cAMP formation. cPLA2 is regulated by mitogen-activated protein kinase (MAPK) in a number of cell types. The presence of this pathway in ASM cells and its role in regulating arachidonate metabolism were supported by the finding that pre-treatment of cells with PD098059 (an inhibitor of mitogen-activated protein kinase kinase-1 activation) reduced PDGF-stimulated cAMP synthesis. The cAMP formed in response to the arachidonate metabolites subsequently reduced the PDGF-dependent activation of c-Raf, MAPK, and DNA synthesis, suggesting the presence of a negative feedback pathway.