Transient non-viral cutaneous gene delivery in burn wounds

BACKGROUND

Gene transfer to burn wounds could present an alternative to conventional and often insufficient topical and systemic application of therapeutic agents to aid in wound healing. The goals of this study were to assess and optimize the potential of transient non-viral gene delivery to burn wounds.

METHODS

HaCaT cells were transfected with luciferase or beta-galactosidase transgene using either pure plasmid DNA (pDNA) or complexed with Lipofectamine 2000, FuGENE6, or DOTAP-Chol. Expression was determined by bioluminescence and fluorescence. Forty male Sprague-Dawley rats received naked pDNA, lipoplexes, or carrier control intradermally into either unburned skin, superficial, partial, or full-thickness scald burn. Animals were sacrificed after 24 h, 48 h, or 7 days, and transgene expression was assessed.

RESULTS

Gene transfer to HaCaT cells showed the overall highest expression for DOTAP/Chol (77.85 ng luciferase/mg protein), followed by Lipofectamine 2000 (33.14 ng luciferase/mg protein). pDNA-derived gene transfer to superficial burn wounds showed the highest expression among burn groups (0.77 ng luciferase/mg protein). However, lipoplex-derived gene transfer to superficial burns and unburned skin failed to show higher expression.

CONCLUSIONS

Lipofectamine 2000 and DOTAP/Chol lipoplex showed significantly enhanced gene transfer, whereas no transfection was detectable for naked DNA in vitro. In contrast to the in vitro study, naked DNA was the only agent with which gene delivery was successful in experimental burn wounds. These findings highlight the limited predictability of in vitro analysis for gene delivery as a therapeutic approach.

Antimicrobial activity of the recombinant designer host defence peptide P-novispirin G10 in infected full-thickness wounds of porcine skin

OBJECTIVES

The growing number of patients with impaired wound healing and the development of multidrug-resistant bacteria demand the investigation of alternatives in wound care. The antimicrobial activity of naturally occurring host defence peptides and their derivatives could be one alternative to the existing therapy options for topical treatment of wound infection. Therefore, the aim of this study was to investigate the antimicrobial activity of proline-novispirin G10 (P-novispirin G10) in vitro and in the infected porcine titanium wound chamber model.

METHODS

The new derived designer host defence peptide P-novispirin G10 was tested in vitro against Gram-positive and Gram-negative bacterial strains. Additionally, cytotoxicity and haemolytic activities of P-novispirin G10 and protegrin-1 were measured. For in vivo studies, six wound chambers were implanted on each flank of Göttinger minipigs (n = 2, female, 6 months old, 15-20 kg). Eleven wound chambers were inoculated 8 days post-operatively with 5 x 10(8) of Staphylococcus aureus; one wound chamber remained uninfected as a system control. After wound infection had been established (4 days after inoculation), each wound chamber was topically treated with P-novispirin G10, protegrin-1 or carrier control. Wound fluid was harvested every hour for a total follow up of 3 h.

RESULTS

P-novispirin G10 demonstrated broad-spectrum antimicrobial activity with moderate haemolytic and cytotoxic activities compared with protegrin-1. In the infected wound chamber model P-novispirin G10 demonstrated a 4 log(10) reduction in bacterial counts.

CONCLUSIONS

This implicates the potential of P-novispirin G10 as an alternative in future antimicrobial wound care. However, more studies are necessary to further define clinical applications and potential side effects in greater detail.

Polybrene improves transfection efficacy of recombinant replication-deficient adenovirus in cutaneous cells and burned skin

BACKGROUND

The hostile environment found in acute and chronic wounds decreases the physiological half-life of purified synthetic or recombinant peptides dramatically. Gene therapy, on the other hand, may be a viable option since it relies on the cellular machinery of the host to locally manufacture the proteins of interest. The aim of this study was to evaluate and optimize the local administration of transient cutaneous adenoviral gene delivery in wounds.

METHODS

Primary human keratinocytes (HKC) and HaCaT cells were transfected with replication-deficient adenovirus (Ad5) containing the reporter gene for beta-galactosidase (LacZ). The vector was used alone or precoated with either (1) Lipofectamine 2000, (2) FuGENE 6, or (3) Polybrene. For in vivo testing a rat burn model was used. Animals were randomized into three groups: (1) Ad5-LacZ alone; (2) Ad5-LacZ precoated with Polybrene, or (3) carrier control (phosphate-buffered saline (PBS)). Samples were harvested from burned and unburned tissue sections after either 48 h or 7 days. Transgene expression was quantified by bioluminometric assay and localized using immunohistochemistry. A BrdU assay was performed to determine the influence of the used transfection reagents on cell proliferation.

RESULTS

Transfection efficacy was significantly improved in vitro (p < 0.001) as well as in partial thickness burned (p = 0.015) and unburned skin (p > 0.001) after precoating Ad5 with Polybrene compared to Ad5 alone. Transgene expression was 10-fold higher in burned skin (9305 pg/mg protein) compared to unburned skin (859 pg/mg protein).

CONCLUSIONS

It is feasible to improve transfection efficacy in vitro and in vivo by precoating the adenovirus with Polybrene.

Transient cutaneous adenoviral gene therapy with human host defense peptide hCAP-18/LL-37 is effective for the treatment of burn wound infections

Host defense peptides (HDP) are naturally occurring effector molecules of the innate immune system, which might be an alternative to currently used antibiotics. The objective of this study was to investigate the efficiency of transient cutaneous adenoviral transfection with human cathelicidin hCAP-18/LL-37 in infected burn wounds. Specific transgene expression was analyzed in vitro on mRNA and protein level using real-time PCR and Western-blot. Male Sprague-Dawley rats (n=40) received a second degree scald burn on both flanks (5% BSA), which were inoculated with 10(8) colony-forming units (CFU) Pseudomonas aeruginosa. Two days later, rats were randomized into the following groups: (1) adenoviral delivery of LL-37 (Ad5-hCAP-18, n=10), (2) synthetic host defense peptide LL-37 (1 mg; n=10), (3) carrier control (PBS, n=10) and (4) empty-virus control (Ad5-LacZ, n=10). Agents were injected intradermally and subcutaneously into both flanks. After either 2 or 7 days, skin samples were harvested and homogenized. CFU per gram tissue were determined. The hCAP-18/LL-37 expression was confirmed by real-time PCR and localized using in situ hybridization. In vitro transfection of cutaneous cells delivered a specific response on mRNA production. Western blot analysis revealed protein expression of hCAP-18/LL-37 in conditioned medium and cell pellet. The host defense peptide LL-37 was detectable after cleavage of the inactive pro-form hCAP-18/LL-37 with human elastase. Ad5-hCAP-18 showed a significant bacterial inhibition of approximately 10 000 fold compared to the control group (P<0.001) and 1000-fold (P<0.001) compared to the synthetic HDP LL-37 7 post-transfection. No inhibition was observed for the carrier or empty-virus control. Real-time PCR and in situ hybridization confirmed expression of hCAP-18/LL-37. In conclusion, transient cutaneous adenoviral delivery of the host defense peptide hCAP-18/LL-37 is significantly more effective than administration of synthetic host defense peptides and might be a potential adjunct for wound treatment in the near future.

Activity of histone H1.2 in infected burn wounds

OBJECTIVES

Infections with multidrug-resistant microorganisms (e.g. Pseudomonas aeruginosa and Staphylococcus aureus) cause immense complications in wound care and in the treatment of immunosuppressed patients. Like most antimicrobial peptides, histones are relatively small polycationic proteins located in each eukaryotic nucleus, which naturally supercoil DNA. The aim of this study was to investigate the in vitro and in vivo activity of histone H1.2 in infected burn wounds and its potential toxicity.

METHODS

To characterize the antimicrobial properties of histone H1.2 against potential causative organisms of burn wound infections, the in vitro radial diffusion assay and modified NCCLS microbroth dilution MIC assay were carried out. Haemolytic and cytotoxic properties were determined in human red blood cells and primary human keratinocytes. In vivo antimicrobial activity was tested in an infected rat burn model with P. aeruginosa (ATCC 27853). All results were compared with the naturally occurring broad-spectrum antimicrobial peptide protegrin-1 and with antibiotics clinically used against the corresponding bacteria.

RESULTS

Human histone H1.2 exerted good antimicrobial activity against all tested microorganisms without significant haemolytic activity. Surprisingly, histone H1.2 showed cytotoxicity with an LD50 of 7.91 mg/L in primary human keratinocytes. The in vivo burn model data revealed a significant three-fold higher reduction in bacterial counts within 4 h compared with carrier control.

CONCLUSIONS

These findings indicate that histone H1.2 is a potential candidate for use as a local and, because of its low haemolytic activity, systemic antimicrobial agent. However, further investigations are needed to specify the cytotoxicity and the dose-response relationship for histone H1.2.