The effects of pentoxifylline on the relative perfusion of tumours growing in three sites in the mouse

Effect of Pentoxifylline on Spinal Fusion: An Experimental Study in Rabbits

STUDY DESIGN

Randomized, double-blinded, animal model.

OBJECTIVE

The objective of this study is to evaluate the effect of pentoxifylline (PTX) on spinal fusion in a rabbit model.

SUMMARY OF BACKGROUND DATA

Previous studies assert that PTX increases new bone formation. Because PTX seems to have these profound effects on bone metabolism, it may be hypothesized that it may enhance spinal fusion.

METHODS

Twenty-four New Zealand white rabbits were randomized and each received single-level posterolateral, inter-transverse process fusion with autologous iliac crest. In group 1, 12 male New Zealand white rabbits were treated with intravenous PTX treatment in 100-mg/kg/day dose after the surgical procedure. In group 2, 12 received no PTX medication and were accepted as the control group. Nine weeks after surgery, the animals were killed. The spines were tested via a manual palpation test, biomechanical testing, plain radiography, computed tomographic scans, and histomorphometric analysis.

RESULTS

The fusion rates of manual palpation were 40% in the control group and 80% in the PTX group (P = 0.17). Using a 5-grade radiographical system, the mean fusion grade was 2.4 in the control group and 3.1 in PTX group (P = 0.012). Total displacement of the fused level for the control group under flexion and extension was 0.2515 mm and was lower for the PTX-treated group: 0.1266 mm (P = 0.012). In the control group, the mean bone volume of the fusion mass determined from computed tomographic analysis was 4.0678 cm, whereas in the PTX group it was 4.7802 cm (P = 0.009). The mean trabecular bone area was 14% and 19% for the control and PTX groups, respectively (P = 0.002).

CONCLUSION

The differences between groups was statistically significant in terms of radiological fusion grading, biomechanical testing, volume of the fusion mass, and percentage of trabecular bone area. These results suggest that PTX may have a beneficial effect on spinal fusion.

LEVEL OF EVIDENCE

2.

Effect of pentoxifylline on histopathological changes in steroid-induced osteonecrosis of femoral head: experimental study in chicken

PURPOSE

Pentoxifylline (PTX) is a derivative of methylxanthine and is used in peripheral vascular and cerebrovascular diseases for its effect on the regulation of blood circulation. We investigated whether PTX could be beneficial for femoral head osteonecrosis associated with steroid through these effects.

METHODS

Sixty mature Leghorn type chickens were chosen and divided into three groups. The 25 chickens in group A were given a weekly dose of 3 mg/kg/week methylprednisolone acetate intramuscularly. Four chickens in group B died after the first drug injection and were excluded from the study. Therefore, the remaining 21 chickens in group B were additionally given 25 mg/kg/day pentoxifylline intramuscularly, along with the steroid medication as given in group A. The ten chickens in group C were not given any injections, as they were accepted as the control group. After the sacrifice of the animals at week 14, both femoral heads were taken from each animal. The animals which died along the course of the study also underwent pathological examination but were not a part of the statistical analysis.

RESULTS

In this study, steroid induced femoral head osteonecrosis has been experimentally observed in chickens after high doses of corticosteroid therapy. The chickens were given pentoxifylline in order to prevent the effects of steroid on bones and bone marrow. The results showed that chickens are suitable osteonecrosis models, and that steroid causes adipogenesis and necrosis in the bone marrow and the death of the subchondral bone.

CONCLUSIONS

The results of this study hint at the assumption that PTX may have a positive benefit on ONFH. PTX seems to minimise the effects of the steroid and reduce the incidence of ONFH.

The biological effect of pentoxifylline on the survival of human head and neck cancer cells treated with continuous low and high dose-rate irradiation

AIM

The aim of this study was to compare the radiosensitivity effect of the G2/M arrest-abrogating substance, pentoxifylline (PTX), with high dose-rate irradiation (HDRI) and low dose-rate irradiation (LDRI), during which DNA repair and cell proliferation occur.

METHODS

Three squamous cell carcinoma cell lines, FaDu, RPMI 2650 and SCC-61, with differences in genomic imbalance and intrinsic radiosensitivity, were irradiated with 140 cGy/min (HDRI) and 0.7 cGy/min (LDRI) in the presence and absence of 2.0 mM PTX. The surviving fraction at 2.0 Gy (SF2) and cell-cycle phase distribution were assessed by DNA flow cytometry analysis and bromodeoxyuridine incorporation.

RESULTS

With HDRI and LDRI the SF2 of FaDu cells decreased by 38.5% and 27.6%, respectively, while the corresponding figures for RPMI 2650 were 28.5% and 48.5%, and for SCC-61 were 44.2% and 28.6%. Increases in G2 populations were evident after both HDRI and LDRI of all cell lines.

CONCLUSIONS

The enhancement in the cytotoxic effect of PTX was statistically significant after HDRI as well as after LDRI in all three cell lines. We therefore conclude that PTX in combination with LDRI is worth further study, both in vitro, for disclosing underlying mechanisms, and in vivo, to confirm the findings.

Enhancement of bone morphogenetic protein-2-induced new bone formation in mice by the phosphodiesterase inhibitor pentoxifylline

Porous collagen disks (6 mm diameter, 1 mm thickness) were impregnated with recombinant human bone morphogenetic protein-2 (rhBMP-2) (5 microg/disk) and implanted onto the back muscles of mice. Pentoxifylline (PTX), which is a methylxanthine-derived inhibitor of phosphodiesterases (PDEs), or vehicle, was injected (5, 25, 50, 100, 200, and 300 mg/kg body weight/day) into the mice subcutaneously once a day for 3 weeks from the day of implantation of the bone morphogenetic protein (BMP)-laden disks. The rhBMP-2-induced ectopic ossicles were harvested and examined using radiographic, histological, and biochemical methods to determine size, bone quality, and calcium content. When compared with controls, ossicles from mice treated with >50 mg/kg per day of PTX were significantly larger in size and had a greater calcium content. However, no differences were noted in mice treated with lower doses (5 and 25 mg/kg per day) of PTX. The temporal sequence of the bone-forming process was unchanged by PTX based on histological examination. The histology of the ossicles from high- and low-dose PTX-treated mice was essentially identical to that observed in the control mice. These experimental results indicate that PTX enhanced the bone-inducing capacity of BMP-2. The underlying mechanism of action most likely involves the inhibition of intracellular phosphodiesterases and a resulting elevation of the intracellular content of cyclic nucleotides. Further studies are warranted to understand how BMP-induced bone formation is pharmacologically modified by PTX.

The effect of pentoxifylline on spontaneous and experimental metastasis of the mouse Neuro2a neuroblastoma

Pentoxifylline (PTX) has been reported to have both direct and indirect anti-tumor effects in experimental tumor models. We studied the effect of PTX on (1) the proliferation of Neuro2a mouse neuroblastoma cells in vitro and in vivo, (2) spontaneous and experimental metastasis, (3) tumor cell membrane fluidity and (4) adhesion to a fibronectin-coated surface. PTX significantly reduced the proliferation of Neuro2a cells in vitro as determined by DNA measurement (P < 0.01) and total cell count (P < 0.02). In vivo, PTX reduced the growth of subcutaneously transplanted primary tumors in syngeneic A/J mice (P < 0.01; n = 15). All seven animals (100%) receiving intravenous tumor cells developed extensive liver metastasis. In contrast, only 1/11 (9%) of animals pre-treated with oral PTX and injected with PTX-treated cells developed liver metastases. Of five mice receiving PTX-treated cells without oral pretreatment of PTX, two out of five (40%) developed liver metastases. There was a slight, but not significant (P = 0.08) increase in both experimental and spontaneous lung metastases formation in PTX-treated animals. However, tumor nodule formation on the lung surface was inefficient. PTX also increased membrane fluidity of the Neuro2a cells and significantly decreased tumor cell adhesion to fibronectin-coated microtiter wells (P < 0.01). We conclude that PTX has a cytostatic effect on the Neuro2a mouse neuroblastoma and exerts an anti-tumor effect on liver metastases following intravenous administration of neuroblastoma cells. Whether these results are directly related to the changes in membrane properties caused by pentoxifylline remains to be established.