Assessment of cryopreserved donor skin viability: the experience of the regional tissue bank of Siena

Abstract

Skin allografts from cadaver donors are an important resource for treating extensive burns, slow-healing wounds and chronic ulcers. A high level of cell viability of cryopreserved allografts is often required, especially in burn surgery, in Italy. Thus, we aimed to determine which conditions enable procurement of highly viable skin in our Regional Skin Bank of Siena. For this purpose, we assessed cell viability of cryopreserved skin allografts procured between 2011 and 2013 from 127 consecutive skin donors, before and after freezing (at day 15, 180, and 365). For each skin donor, we collected data concerning clinical history (age, sex, smoking, phototype, dyslipidemia, diabetes, cause of death), donation process (multi-tissue or multi-organ) and timing of skin procurement (assessment of intervals such as death-harvesting, harvesting-banking, death-banking). All these variables were analysed in the whole case study (127 donors) and in different groups (e.g. multi-organ donors, non refrigerated multi-tissue donors, refrigerated multi-tissue donors) for correlations with cell viability. Our results indicated that cryopreserved skin allografts with higher cell viability were obtained from female, non smoker, heartbeating donors died of cerebral haemorrhage, and were harvested within 2 h of aortic clamping and banked within 12 h of harvesting (13-14 h from clamping). Age, cause of death and dyslipidaemia or diabetes did not appear to influence cell viability. To maintain acceptable cell viability, our skin bank needs to reduce the time interval between harvesting and banking, especially for refrigerated donors.

Current insights into skin banking: storage, preservation and clinical importance of skin allografts

“…13,15,16,27,30,36 However, three main problems are encountered. First, tissue viability is difficult to measure in the laboratory: since in vivo setting conditions are very different, laboratory tests cannot achieve 100% accuracy.…”

“…Second, since different skin viability assessment methods, both quantitative (e.g., glucose or oxygen consumption assay, vital staining methods, lactate production, etc.) and qualitative (e.g., cell count by trypan blue test) are used, [36][37][38] and they cannot be compared. Third, because different authors have developed their own formulae to calculate skin viability, study results cannot always be compared.…”

“…14,17,[33][34][35]38,39 It will therefore be necessary to harmonize laboratory methods and standardize viability testing and measurement in order to compare study results. 36 …”

“…13,17,[33][34][35] Viable CSAs are deemed to have better transplant performance, to promote neovascularization, speed up healing, stimulate immunomodulatory response and reduce mortality risk. 13,14,[31][32][33][34][35][36] Some authors speculate that high cell viability may not be necessary for skin allograft function as a temporary dressing or permanent substitute. 37,38 However, comparison of viable CSAs with unviable glycerol-preserved allografts (GPAs) has shown superior clinical outcomes (e.g., lower mortality and morbidity rate, reduced healing time) in both adult and child burn patients treated with viable CSAs.…”

“…However, this assumption comes largely from direct observation and clinical experience, since large-scale standardized studies on whether CSAs are clinically superior to GPAs are yet to be performed. 36 …”