Iron Chelation with Transdermal Deferoxamine Accelerates Healing of Murine Sickle Cell Ulcers

Abstract

Objective: Sickle cell ulcers (SCUs) are a devastating comorbidity affecting patients with sickle cell disease (SCD). SCUs form over the medial or lateral malleoli of the lower extremity, are slow to heal, and prone to recidivism. Some SCUs may never heal, leading to chronic pain and foot deformities. There is no specific and effective therapy for SCUs. Systemic deferoxamine (DFO) has been demonstrated to prevent some of the sequelae of SCD by chelating iron. In this study, we tested the ability of DFO delivered via a transdermal delivery system (DFO-TDDS) to accelerate healing in a murine model of SCU. Approach: Excisional wounds were created in a transgenic murine model of SCD expressing >99% human sickle hemoglobin, and healing rates were compared with wounds in wild-type mice. Next, excisional wounds in SCD mice were treated with DFO-TDDS, DFO injection, or left untreated. Wound closure rates, histology, and iron in the healed wounds were analyzed. Results: Wounds in SCD mice healed significantly slower than wild-type mice (***p < 0.001). DFO-TDDS-treated wounds demonstrated significantly accelerated time to closure, reduced size, and improved wound remodeling compared with untreated wounds (***p < 0.001) and DFO injection treatment (*p < 0.05). DFO released from the TDDS into wounds resulted in chelation of excessive dermal-free iron. Innovation: DFO-TDDS is a novel therapeutic that is effective in healing wounds in sickle cell mice. Conclusion: DFO-TDDS significantly accelerates healing of murine SCUs by chelation of excessive free iron and is currently manufactured in an FDA-compliant facility to be translated for treating human SCUs.

Keywords: deferoxamine; iron chelator; sickle cell disease; sickle cell ulcers; wound healing.

Geoffrey C. Gurtner, MD, FACS

Figure 1.

HbSS-BERK mice demonstrate wound healing impairments compared with wild-type mice. (A) Photographs of wounds taken every other day after wounding until closure in the untreated HbSS and wild-type groups. (B) Wound healing curves demonstrate reduction in wound size every other day until closure. (C) Denotes the time of closure of wounds. At least eight wounds were analyzed in each cohort. *p < 0.05, **p < 0.01, ***p < 0.001 by ANOVA.

Figure 2.

DFO-TDDS accelerates wound healing and is more effective than injected DFO at treating wounds in HbSS-BERK mice. (A) Photographs of wounds taken every other day after wounding until closure in the untreated, DFO-TDDS, and DFO injection groups. (B) Wound healing curves demonstrate reduction in wound size every other day until closure. (C) Denotes the time of closure of wounds. At least eight wounds were analyzed in each group. *p < 0.05, **p < 0.01, ***p < 0.001 by ANOVA. DFO, deferoxamine; DFO-TDDS, deferoxamine transdermal delivery system.

Figure 3.

Wounds in HbSS-BERK mice treated with DFO-TDDS display increased collagen deposition and dermal thickness. (A) Trichrome staining of histological sections of healed wounds from HbSS-BERK mice in the untreated, DFO-TDDS, and DFO injection groups demonstrates collagen deposition (blue). (B) Dermal thickness is measured from the photomicrographs of each wound in the DFO-TDDS-treated, DFO injection-treated, and untreated groups. ***p < 0.001 by Student's t-test.

Figure 4.

Wounds in HbSS-BERK mice treated with DFO-TDDS display reduced iron by Perl's Prussian blue stain. (A, B) Healed wounds in the untreated, DFO-TDDS-treated, and DFO injection-treated groups were subjected to Perl's Prussian blue stain. Iron (blue) was detected in the untreated wounds but not in DFO-TDDS- or DFO injection-treated groups, indicating chelation of iron by DFO. (C) Chemical structure of deferoxamine. (D) Chemical structure of ferrioxamine, the stable chemical compound formed by binding of iron (Fe³⁺) and deferoxamine. *p < 0.05 by Student's t-test.

Figure 5.

Schematic demonstration of the effectiveness of DFO-TTDS in healing sickle cell ulcers. (A) Normal skin is unlike (B) skin in sickle cell disease, which has excessive free iron, increased inflammation, and lesser dermal strength. Thus, sickle cell skin is exposed to (C) recurrent breakage in regions of excessive iron accumulation causing sickle cell ulcers. (D) Topical application of DFO-TDDS on sickle cell ulcers results in the release of DFO into the dermis and (E) chelation of excessive free iron in a 1:1 ratio. (F) Continued application of DFO-TDDS until closure of the ulcer results in a thicker dermis and a remodeled wound, which can resume normal homeostasis.