Skin tumor development after UV irradiation and photodynamic therapy is unaffected by short-term pretreatment with 5-fluorouracil, imiquimod and calcipotriol. An experimental hairless mouse study

Improving the efficacy of photodynamic therapy for actinic keratosis: A comprehensive review of pharmacological pretreatment strategies

BACKGROUND

Photodynamic therapy (PDT) is approved for treatment of actinic keratoses (AKs) and field-cancerisation. Pretreatment with pharmacological compounds holds potential to improve PDT efficacy, through direct interaction with PpIX formation or through an independent response, both of which may improve PDT treatment.

OBJECTIVE

To present the currently available clinical evidence of pharmacological pretreatments prior to PDT and to associate potential clinical benefits with the pharmacological mechanisms of action of the individual compounds.

METHODS

A comprehensive search on the Embase, MEDLINE, and Web of Science databases was performed.

RESULTS

In total, 16 studies investigated 6 pretreatment compounds: 5-fluorouracil (5-FU), diclofenac, retinoids, salicylic acid, urea, and vitamin D. Two of these, 5-FU and vitamin D, robustly increased the efficacy of PDT across multiple studies, illustrated by mean increases in clearance rates of 21.88% and 12.4%, respectively. Regarding their mechanisms, 5-FU and vitamin D both increased PpIX accumulation, while 5-FU also induced a separate anticarcinogenic response. Pretreatment with diclofenac for four weeks improved the clearance rate in one study (24.9%), administration of retinoids had a significant effect in one of two studies (16.25%), while salicylic acid and urea did not lead to improved PDT efficacy. Diclofenac and retinoids demonstrated independent cytotoxic responses, whereas salicylic acid and urea acted as penetration enhancers to increase PpIX formation.

CONCLUSION

5-FU and vitamin D are well-tested, promising candidates for pharmacological pretreatment prior to PDT. Both compounds affect the haem biosynthesis, providing a target for potential pretreatment candidates.

KEY WORDS

Photodynamic Therapy, Actinic Keratosis,Pre-tretment,Review,enhancement.

Influence of Serum Vitamin D Level in the Response of Actinic Keratosis to Photodynamic Therapy with Methylaminolevulinate

In mouse models of squamous cell carcinoma, pre-treatment with calcitriol prior to photodynamic therapy with aminolevulinic acid (ALA) enhances tumor cell death. We have evaluated the association between vitamin D status and the response of actinic keratoses to photodynamic therapy with methylaminolevulinate. Twenty-five patients with actinic keratoses on the head received one session of photodynamic therapy with methylaminolevulinate. Biopsies were taken at baseline and six weeks after treatment. Immuno-histochemical staining was performed for VDR, P53, Ki67 and β-catenin. Basal serum 25(OH)D levels were determined. Cases with a positive histological response to treatment had significantly higher serum 25(OH)D levels (26.96 (SD 7.49) ngr/mL) than those without response (18.60 (SE 7.49) ngr/mL) (p = 0.05). Patients with a complete clinical response displayed lower basal VDR expression (35.71% (SD 19.88)) than partial responders (62.78% (SD 16.735)), (p = 0.002). Our results support a relationship between vitamin D status and the response of actinic keratoses to photodynamic therapy with methylaminolevulinate.

A randomized split-scalp study comparing calcipotriol-assisted methyl aminolaevulinate photodynamic therapy (MAL-PDT) with conventional MAL-PDT for the treatment of actinic keratosis

BACKGROUND

Topical photodynamic therapy (PDT) is an approved treatment for actinic keratosis (AK). To enhance the efficacy of PDT for AKs, physical and chemical pretreatments have been suggested.

OBJECTIVES

To compare the efficacy and safety of the combination of topical calcipotriol (CAL) before methyl aminolaevulinate (MAL)-PDT for AKs of the scalp vs. conventional MAL-PDT in a randomized controlled clinical trial.

METHODS

Twenty patients with multiple AKs on the scalp were randomized to receive conventional MAL-PDT with previous curettage on one side of the scalp and CAL-assisted MAL-PDT once a day for 15 days before illumination on the other side. After 3 months, patients were evaluated for clearance of AKs, side-effects and histopathology before and after the procedure. Protoporphyrin IX (PpIX) fluorescence was measured before and after illumination on both sides.

RESULTS

All 20 patients completed the study. Overall AK clearance rates were 92·1% and 82·0% for CAL-PDT and conventional PDT, respectively (P < 0·001). Grade 1 AKs showed similar response rates for both sides (P = 0·055). However, grade II AKs showed more improvement on the CAL-PDT side (90%) than on the MAL-PDT side (63%) (P < 0·001). Before illumination, PpIX fluorescence intensity was higher on the CAL-assisted side (P = 0·048). The treatment was more painful on the CAL-PDT side, although well tolerated. The mean visual analogue scale score was 5·4 ± 1·4 on the CAL-PDT side and 4·0 ± 0·69 on the conventional MAL-PDT side (P = 0·001). Side-effects such as erythema (P = 0·019), oedema (P = 0·002) and crusts (P < 0·001) were more pronounced on the CAL-assisted side. Histopathological analyses were obtained from five patients and both sides showed improved keratinocyte atypia following PDT, with slightly more improvement on the CAL-assisted side.

CONCLUSIONS

CAL-assisted PDT proved to be safe and more effective than conventional MAL-PDT for the treatment of AKs on the scalp. CAL pretreatment increased PpIX accumulation within the skin and may have enhanced the efficacy in this first human trial.

Nanomedicine and advanced technologies for burns: Preventing infection and facilitating wound healing

According to the latest report from the World Health Organization, an estimated 265,000 deaths still occur every year as a direct result of burn injuries. A widespread range of these deaths induced by burn wound happens in low- and middle-income countries, where survivors face a lifetime of morbidity. Most of the deaths occur due to infections when a high percentage of the external regions of the body area is affected. Microbial nutrient availability, skin barrier disruption, and vascular supply destruction in burn injuries as well as systemic immunosuppression are important parameters that cause burns to be susceptible to infections. Topical antimicrobials and dressings are generally employed to inhibit burn infections followed by a burn wound therapy, because systemic antibiotics have problems in reaching the infected site, coupled with increasing microbial drug resistance. Nanotechnology has provided a range of molecular designed nanostructures (NS) that can be used in both therapeutic and diagnostic applications in burns. These NSs can be divided into organic and non-organic (such as polymeric nanoparticles (NPs) and silver NPs, respectively), and many have been designed to display multifunctional activity. The present review covers the physiology of skin, burn classification, burn wound pathogenesis, animal models of burn wound infection, and various topical therapeutic approaches designed to combat infection and stimulate healing. These include biological based approaches (e.g. immune-based antimicrobial molecules, therapeutic microorganisms, antimicrobial agents, etc.), antimicrobial photo- and ultrasound-therapy, as well as nanotechnology-based wound healing approaches as a revolutionizing area. Thus, we focus on organic and non-organic NSs designed to deliver growth factors to burned skin, and scaffolds, dressings, etc. for exogenous stem cells to aid skin regeneration. Eventually, recent breakthroughs and technologies with substantial potentials in tissue regeneration and skin wound therapy (that are as the basis of burn wound therapies) are briefly taken into consideration including 3D-printing, cell-imprinted substrates, nano-architectured surfaces, and novel gene-editing tools such as CRISPR-Cas.