In agreement with previous studies, no statistical difference was observed in the duration of hospital based on receiving CAK following the adjustment for TBSA% [19-21]. In a retrospective study involved 20 children who survived massive burns, the use of CAK, cultured as sheets was associated with longer hospital stay (128 compared to 89 days in controls) [22]. The median duration of hospital stay in our treatment group was 1.8 days (1.2- 2.8)/ TBSA%, which is similar to that of other burn centres that treat adult patients with moderate -sized burns who require operation [23]. Among patients who have been treated with CAK, hospital stay has been reported to be between 0.8- 5 days/TBSA%, usually about 1.5 days/TBSA%, which is similar to our findings [6, 10, 19, 20, 22, 24-27].
Other evaluated parameters showed no difference between the two study groups, which was not in agreement with previous studies. For example, more survivors in the group treated with CAK was reported in an earlier paper [19]. Our “take” rate was lower than [28], similar to [6], or better than [29] which used the same techniques. Scarring was assessed after three months, when the median Vancouver score was 8, which is “severe” compared with others who have reported scores between 2.4 [9] and 5.8 [29]. The assessments were made later in these studies of more mature scars, which may explain why they had a better scoring than our patients [11, 30]. The method of using CAK has been reported to reduce the need for donor sites as well as accelerating the healing of donor sites of split thickness skin grafts. When it has been used for deep burns, several limitations were described, such as the time needed to culture cells, the fragility of the epidermal layer, the lack of dermis that results in the formation of blisters, prolonged hospital stay, severe scarring and related expenses [24, 27, 31]. Our culture time was somehow longer than what have been reported before (12 - 21 days) [9, 28, 29, 32]. Alternatives to the classical CAK, tissue-engineered products that combine keratinocytes with other cell types, micro barriers, or scaffolds could be considered [22, 31, 33-37].
In another direction, we investigated the possibility of the differentiation of a mesenchymal stem cell line into keratinocyte-like cell with different culturing conditions. Cytokeratin 14 is an important protein that found mainly in the keratinocytes of the basal layer of epidermis, which is responsible for giving the rest of the epidermal cells. This protein is important for the cell protection as well as their proliferative capacity [38]. Short term culture for 7 days was associated with the expression of this marker under different culturing conditions. Glass, as an available and cheap culture material was associated with enhanced proliferative and differentiation capacity of iMSC. The possible explanation was providing an adhesion and migration surface of iMSC during their culture and differentiation. Such effect has been shown before in stem cell differentiation into the osteogenic lineage with various biomaterials [39]. These results would provide a new direction in cell-based therapy for our burn victims.
Limitations
The retrospective design of the study is a limitation. Patients treated with CAK were those with large wounds that had not healed at the time when the cell culture was ready. Another important factor is the possible heterogeneity of the isolated cells. Melanocytes, fibroblasts, angioblasts as well as epidermal stem cells might have been included during the isolation process. In additions, keratinocytes can un-differentiate in the culture system into earlier precursors [40, 41]. The one centre approach with results generated from a relatively small group is another limitation that makes it difficult to generalise, although this sample is a usual trend in similar studies [29].
Based on the results we will also start a new program for culturing patient’s autologous stem cells and their differentiation into keratinocyte like cells. This step will need to follow the strict regulations of advanced therapeutic medical products in order to be applied clinically.