1. The effect of PDRN, an adenosine receptor A2A agonist, on the healing of chronic diabetic foot ulcers: results of a clinical trial.

2. The effects of polydeoxyribonucleotide on the survival of random pattern skin flaps in rats.

● Abstract

BACKGROUND : Partial or complete necrosis of a skin flap is a common problem. Polydeoxyribonucleotide (PDRN) can be extracted from trout sperm and used as a tissue repair agent. The aim of this study was to investigate whether PDRN could improve the survival of random pattern skin flaps in rats.

METHODS : Twenty-two male Sprague-Dawley rats were randomly divided into two groups: the PDRN treatment group (n=11) and the control group (n=11). Caudally pedicled random pattern skin flaps were elevated on their dorsal skin and resutured. The treatment group received daily intraperitoneal administration of PDRN (8 mg/kg/day), and the control group received fluid vehicle (NaCl 0.9%, 8 mg/kg/day) from day 0 to day 6. On day 7, the flap survival was evaluated and the harvested tissue surrounding the demarcation line of the necrotic area was stained with H&E, anti-rat vascular endothelial cell growth factor (VEGF) antibody, and PECAM-1/CD31 antibody.

RESULTS : The average necrotic area of the flap in the PDRN group was significantly smaller when compared with that of the control group. Histologic and immunohistochemical evaluation showed that granulation thickness score and VEGF-positive staining cells were marked higher in thePDRN group than in the control group. PECAM-1/CD31-positive microvascular densities were significantly higher in the PDRN group when compared with the control group.

CONCLUSIONS : This study confirms that PDRN improves the survival of random pattern skin flaps in rats. These results may represent a new therapeutic approach to enhancing flap viability and achieving faster wound repair.

3. Polydeoxyribonucleotide restores blood flow in an experimental model of ischemic skin flaps.

● Abstract

BACKGROUND : Ischemia is a major factor contributing to failure of skin flap surgery, which is routinely used for coverage of wounds to prevent infection and to restore form and function. An emerging concept is that adenosine A(2A) receptors can improve tissue oxygenation by stimulating angiogenesis, likely through vascular endothelial growth factor (VEGF). This study assessed the ability of polydeoxyribonucleotide (PDRN) to restore blood flow and improve wound healing, acting through the A(2A) receptor, in a rat model of ischemic skin flaps.

METHODS : The H-shaped double-flap model was used in male Sprague-Dawley rats. After surgical procedures, the animals were randomized to receive intraperitoneal PDRN (8 mg/kg) or vehicle (NaCl 0.9%). Rats were euthanized 3, 5, and 10 days after skin injury, after the evaluation of skin perfusion by laser Doppler. The wounds underwent histologic analysis and were measured for VEGF messenger RNA and protein expression, hypoxia inducible factor-1-α (HIF-1α), and inducible nitric oxide synthase (iNOS) protein expression, and nitrite content.

RESULTS : Blood flow markedly increased in blood flow in ischemic flaps treated with PDRN, with a complete recovery starting from day 5 (ischemic flap + vehicle, 1.80 ± 0.25; ischemic flap + PDRN, 2.46 ± 0.25; P < .001). Administration of PDRN enhanced the expression of VEGF (ischemic flap + vehicle, 5.3 ± 0.6; ischemic flap + PDRN, 6.2 ± 0.5; P < .01) at day 5, and iNOS (ischemic flap + vehicle, 3.9 ± 0.6; ischemic flap + PDRN, 5.3 ± 1; P < .01), but reduced HIF-1α expression (ischemic flap + vehicle, 7 ± 1.1; ischemic flap + PDRN, 4.8 ± 0.5; P < .05) at day 3. Histologically, the PDRN-treated group showed complete re-epithelialization and well-formed granulation tissue rich in fibroblasts.

CONCLUSIONS : These results suggest that PDRN restores blood flow and tissue architecture, probably by modulating HIF-1α and VEGF expression, and may be an effective therapeutic approach in improving healing of ischemic skin flaps.

4. Activation of adenosine A2A receptors restores the altered cell-cycle machinery during impaired wound healing in genetically diabetic mice.

BACKGROUND : Cyclins drive cell-cycle progression by associating with their kinase partners, cyclin-dependent kinases (CDK). We investigated cyclin D1/CDK6, cyclin E/CDK2 complexes, and the cell-cycle negative regulators p15 and p27 in an incisional skin wound model.

METHODS : Wounds were produced on the back of female diabetic mice and their normoglycemic littermates. Animals were treated with polydeoxyribonucleotide (PDRN, 8 mg/kg/i.p.), an agonist of adenosine A2(A) receptors, or its vehicle daily. Granulation tissue proliferation by Ki67 immunostaining, cyclin D/CDK6 and cyclin E/CDK2 complexes, and p21 and p16 proteins (Western blot analysis), and the histologic changes were assessed at different days (3, 6, and 12 days after injury).

RESULTS : Numerous Ki67 positive cells were observed at day 3 and day 6 in the granulation tissue of normoglycemic mice. Ki67 positive cells were fewer in diabetic than in normoglycemic mice. PDRN increased Ki67 positive cells in diabetic mice. Normoglycemic mice showed the greatest upregulation of cyclin D1, CDK6, cyclin E, and CDK2 at day 6. Diabetic mice had a markedly lower expression of cyclin D1, CDK6, cyclin E, and CDK2 at day 6. They also showed a greater expression of p15 and p27 at day 6. PDRN administration in diabetic mice increased cyclin D1/CDK6 and cyclin E/CDK2 expression and reduced p15 and p27 inhibitors at day 6 after injury; moreover, it improved the impaired wound healing at day 12.

CONCLUSION : Our results suggest that adenosine A2(A) receptor activation by PDRN might represent a therapeutic strategy to overcome the diabetes-impaired cell-cycle machinery.

5. Polydeoxyribonucleotide (PDRN ): a safe approach to induce therapeutic angiogenesis in peripheral artery occlusive disease and in diabetic foot ulcers.

● Abstract

Peripheral arterial occlusive disease (PAOD) of lower extremities is becoming more prevalent worldwide. The general prognosis is particularly negative with a high prevalence of coronary heart disease and cerebrovascular disease. Diabetic foot ulcers occur in 15% of all the patients with diabetes and proceed to lower-leg amputations. In diabetic ulcers, wound healing is impaired because of delayed angiogenesis. In both pathological conditions, therapeutic angiogenesis using angiogenic growth factors, particularly Vascular Endothelial Growth Factor VEGF, is expected to be a valuable treatment. The most used approaches are based on VEGF local delivery or gene therapy, but they failed to meet the expected primary goals of therapy. Adenosine receptor stimulation can induce VEGF expression in many types of cells and this may be achieved by stimulating the A(2A) or A(2B) receptor or both, following the signalling pathways activated by hypoxia. Polideoxyribonucleotide (PDRN) is obtained from sperm trout by an extraction process. The compounds hold a mixture of deoxyribonucleotides polymers with chain lengths ranging between 50 and 2000 bp. PDRN is able to stimulate VEGF production during pathological conditions of low tissue perfusion. It likely acts through the stimulation of A(2A) receptors. Furthermore, acute and chronic toxicity studies showed a good safety profile. PDRN has been shown to be effective in an experimental model of PAOD, hind limb ischemia, impaired wound healing and burn injury. Preliminary studies and ongoing clinical trials predict a significant therapeutic efficacy in patients. These data lead to hypothesize a role for PDRN in therapeutic angiogenesis.

6. Polydeoxyribonucleotide improves angiogenesis and wound healing in experimental thermal injury.

OBJECTIVE : Polydeoxyribonucleotide contains a mixture of nucleotides and interacts with adenosine receptors, stimulating vascular endothelial growth factor expression and wound healing. The purpose of this study was to investigate the effect of polydeoxyribonucleotide on experimental burn wounds.

INTERVENTIONS : Mice were immersed in 80 degrees C water for 10 secs to achieve a deep-dermal second-degree burn. Animals were randomized to receive either polydeoxyribonucleotide (8 mg/kg/day intraperitoneally for 14 days) or its vehicle alone (0.9% NaCl solution at 100 microL/day intraperitoneally). On days 7 and 14 the animals were killed. Blood was collected for tumor necrosis factor-alpha measurement; burn areas were used for histologic and immunohistochemical examination, for the evaluation of vascular endothelial growth factor and nitric oxide synthases by Western blot, and for the determination of wound nitric oxide products.

MEASUREMENTS AND MAIN RESULTS : Polydeoxyribonucleotide increased burn wound re-epithelialization and reduced the time to final wound closure. Polydeoxyribonucleotide improved healing of burn wound through increased epithelial proliferation and maturation of the extracellular matrix as confirmed by fibronectin and laminin immunostaining. Polydeoxyribonucleotide also improved neoangiogenesis as suggested by the marked increase in microvessel density and by the robust expression of platelet-endothelial cell adhesion molecule-1. Furthermore, polydeoxyribonucleotide blunted serum tumor necrosis factor-alpha and enhanced inducible nitric oxide synthase and vascular endothelial growth factor expression and the wound content of nitric oxide products.

CONCLUSIONS : Our study suggests that polydeoxyribonucleotide may be an effective therapeutic approach to improve clinical outcomes after thermal injury.

7. Polydeoxyribonucleotide stimulates angiogenesis and wound healing in the genetically diabetic mouse.

● Abstract

Healing of diabetic wounds still remains a critical medical problem. Polydeoxyribonucleotide (PDRN), a compound having a mixture of deoxyribonucleotide polymers, stimulates the A2 purinergic receptor with no toxic or adverse effect. We studied the effects of PDRN in diabetes-related healing defect using an incisional skin-wound model produced on the back of female diabetic mice (db+/db+) and their normal littermates (db+/+m). Animals were treated daily for 12 days with PDRN (8 mg/kg/ip) or its vehicle (100 muL 0.9%NaCl). Mice were killed 3, 6, and 12 days after skin injury to measure vascular endothelial growth factor (VEGF) mRNA expression and protein synthesis, to assay angiogenesis and tissue remodeling through histological evaluation, and to study CD31, Angiopoietin-1 and Transglutaminase-II. Furthermore, we measured wound breaking strength at day 12. PDRN injection in diabetic mice resulted in an increased VEGF message (vehicle=1.0+/-0.2 n-fold vs. beta-actin;PDRN=1.5+/-0.09 n-fold vs. beta-actin) and protein wound content on day 6 (vehicle=0.3+/-0.07 pg/wound; PDRN=0.9+/-0.1 pg/wound). PDRNinjection improved the impaired wound healing and increased the wound-breaking strength in diabetic mice. PDRN also caused a marked increase in CD31 immunostaining and induced Transglutaminase-II and Angiopoietin-1 expression. Furthermore, the concomitant administration of 3,7-dimethyl-1-propargilxanthine, a selective adenosine A2A receptor antagonist, abolished PDRN positive effects on healing. However, 3,7-dimethyl-1-propargilxanthine alone did not affect wound healing in both diabetic mice and normal littermates. These results suggest that PDRN might be useful in wound disorders associated with diabetes.

8. Clinical evaluation of corneal epithelialization after photorefractive keratectomy in patients treated with polydeoxyribonucleotide (PDRN) eye drops: a randomized, double-blind, placebo-controlled trial.

9. Clinical evaluation of the trophic effect of polydeoxyribonucleotide (PDRN) in patients undergoing skin explants. A Pilot Study.

10. Evaluation of the trophic effect of human placental polydeoxyribonucleotide on human knee skin fibroblasts in primary culture.

11. Chromatin breakdown in the white blood cells of rats during irradiation and in combined radiation injury under cystamine protection.