Cell therapy for full-thickness wounds: are fetal dermal cells a potential source?

The application of autologous dermal fibroblasts has been shown to improve burn wound healing. However, a major hurdle is the availability of sufficient healthy skin as a cell source. We investigated fetal dermal cells as an alternative source for cell-based therapy for skin regeneration. Human (hFF), porcine fetal (pFF) or autologous dermal fibroblasts (AF) were seeded in a collagen-elastin substitute (Novomaix, NVM), which was applied in combination with an autologous split thickness skin graft (STSG) to evaluate the effects of these cells on wound healing in a porcine excisional wound model. Transplantation of wounds with NVM+hFF showed an increased influx of inflammatory cells (e.g., neutrophils, macrophages, CD4(+) and CD8(+) lymphocytes) compared to STSG, acellular NVM (Acell-NVM) and NVM+AF at post-surgery days 7 and/or 14. Wounds treated with NVM+pFF presented only an increase in CD8(+) lymphocyte influx. Furthermore, reduced alpha-smooth muscle actin (αSMA) expression in wound areas and reduced contraction of the wounds was observed with NVM+AF compared to Acell-NVM. Xenogeneic transplantation of NVM+hFF increased αSMA expression in wounds compared to NVM+AF. An improved scar quality was observed for wounds treated with NVM+AF compared to Acell-NVM, NVM+hFF and NVM+pFF at day 56. In conclusion, application of autologous fibroblasts improved the overall outcome of wound healing in comparison to fetal dermal cells and Acell-NVM, whereas application of fetal dermal fibroblasts in NVM did not improve wound healing of full-thickness wounds in a porcine model. Although human fetal dermal cells demonstrated an increased immune response, this did not seem to affect scar quality.

Evaluation of saline, RPMI and DMEM/F12 for storage of split-thickness skin grafts.

Skin grafting is standard of care for severe burn and trauma patients. Graft sites are often accompanied with more pain than the burn sites. To minimize graft site areas, excess skin remaining after harvesting, is stored in saline at 4°C to be used for transplantation up to 1 week later. However, the optimal storage solution and maximum storage time are not known. We set out to determine the storage time after which stored skin is still viable. In addition, different storage solutions were tested. Split-thickness skin from 15 donors with a thickness of 0.3 mm was stored in normal saline, in medium, RPMI or DMEM/F12, allowing pairwise comparison. Biopsies were taken up to 3 weeks for histology and for skin viability assessment using an MTT based activity assay. Activity of the saline stored control decreased to 62% at day 7 and to 27% at day 14. Activity was retained at a higher level in RPMI and was 78% at day 7 and 70% at day 14. Results with DMEM/F12 showed a similar trend as the saline control. Based on activity, RPMI was found to be superior to DMEM/F12 (on days 3 and 10) and both saline and DMEM/F12 (on days 14 and 21). Capability to proliferate (BrdU incorporation) did not differ between media, up to 7 days. Histologically, the number of apoptotic cells increased in time but differences between media were not noted. Based on these results, RPMI would be an improvement over saline in retaining viability of skin grafts during storage, and possibly in improved take rate.

The effect of a honey based gel and silver sulphadiazine on bacterial infections of in vitro burn wounds.

Bacterial contamination remains a constant threat in burn wound care. Topical treatments to combat contaminations have good bactericidal effects but can have detrimental effects for the healing process. Treatments with for example silver can increase healing times. Honey based products can be a good alternative as it is antibacterial and patient-friendly. We evaluated the bactericidal and cytotoxic effects of a honey based gel and silver sulphadiazine in a human burn wound model with Pseudomonas aeruginosa. After adding 10(5)colony forming units of P. aeruginosa, topical treatments were applied on the burn wound models. After 2, 12, 24, 28 and 70 h, bacteria were dislodged and counted by plating dilutions. Cytotoxic effects were evaluated histologically in samples of burn wound models treated topically for 3 weeks, without bacteria. L-Mesitran Soft significantly reduced the bacterial load (5-log reduction) up to 24h but did not completely eliminate bacteria from the burn wounds. After Flammazine(®) treatment, only a few colony forming units were observed at all time points. In contrast, re-epithelialization was significantly reduced after application of Flammazine(®) compared to L-Mesitran Soft or control. This in vitro model of burn wound infection can be used to evaluate topical treatments. L-Mesitran Soft is a good alternative for treating burn wounds but the slightly lower bactericidal activity in the burn wound model warrants a higher frequency of application.

Digital image analysis versus clinical assessment of wound epithelialization: a validation study.

To evaluate the progress in wound healing, wound assessment is mandatory. Epithelialization is traditionally assessed subjectively by the clinician. In a previous study, subjective assessment of epithelialization was shown to be reliable. In this study, reliability of epithelialization measured by digital image analysis was investigated and then, we validated the subjective evaluation by comparing this assessment to measurements with digital image analysis. Clinicians assessed epithelialization in 50 burn wounds that were treated with a split skin graft. Epithelialization of these wounds was also measured by three observers using digital image analysis. Reliability of digital image analysis was tested using the intraclass correlation (IC). To test validity, subjective clinical assessment was correlated with digital image analysis (IC). The results showed that interobserver reliability of epithelialization measured by digital image analysis was good (IC coefficient 0.74). Subjective clinical assessment of epithelialization showed a strong correlation with digital image analysis (IC coefficient 0.80). In conclusion, subjective clinical evaluation of wound epithelialization is as good as an objective measure, in this study digital image analysis. Since digital image analysis is more time-consuming, we recommend the use of the subjective evaluation for daily practice.