Development of a combined radiation and full thickness burn injury minipig model to study the effects of uncultured adipose-derived regenerative cell therapy in wound healing

<b>Purpose:</b> To develop an approach that models the cutaneous healing that occurs in a patient with full thickness thermal burn injury complicated by total body radiation exposure sufficient to induce sub-lethal prodromal symptoms. An assessment of the effects of an autologous cell therapy on wound healing on thermal burn injury with concomitant radiation exposure was used to validate the utility of the model. <b>Methods:</b> Göttingen minipigs were subjected to a 1.2 Gy total body irradiation by exposure to a 6 MV X-ray linear accelerator followed by ∼10 cm² full thickness burns (pre-heated brass block with calibrated spring). Three days after injury, wounds were excised to the underlying fascia and each animal was randomized to receive treatment with autologous adipose-derived regenerative cells (ADRC) delivered by local or intravenous injection, or vehicle control. Blood counts were used to assess radiation-induced marrow suppression. All animals were followed using digital imaging to assess wound healing. Full-thickness biopsies were obtained at 7, 14, 21 and 30 days’ post-treatment. <b>Results:</b> Compared to animals receiving burn injury alone, significant transient neutropenia and thrombocytopenia were observed in irradiated subjects with average neutrophil nadir of 0.79 × 10³/μl (day 15) and platelet nadir of 60 × 10³/μl (day 12). Wound closure through a combination of contraction and epithelialization from the wound edges occurred over a period of approximately 28 days’ post excision and treatment. Re-epithelialization was accelerated in wounds treated with ADRC (mean 3.5-fold increase at 2 weeks post-treatment relative to control). This acceleration was accompanied by an average 67% increase in blood vessel density and 30% increase in matrix (collagen) deposition. Similar results were observed when ADRC were injected either directly into the wound or by intravenous administration. <b>Conclusions:</b> Although preliminary, this study provides a reproducible minipig model of thermal burn injury complicated by myelosuppressive total body irradiation that utilizes standardized procedures to evaluate novel countermeasures for potential use following attack by an improvised nuclear device.

**研究目的**：构建可模拟全层热烧伤合并足以诱发亚致死前驱症状的全身辐射暴露患者皮肤愈合过程的实验方法。本研究通过评估自体细胞疗法对合并辐射暴露的热烧伤创面愈合的影响，验证该模型的实用性。
**研究方法**：选用哥廷根小型猪，先通过6 MV X射线直线加速器给予1.2 Gy全身辐射，随后在其体表造成约10 cm²的全层烧伤（采用带校准弹簧的预加热黄铜模具制备）。造模后第3天，对创面进行清创至皮下筋膜层，随后将所有实验动物随机分组，分别接受局部或静脉注射自体脂肪来源再生细胞（autologous adipose-derived regenerative cells, ADRC）治疗，或给予赋形剂对照。通过血常规检测评估辐射诱导的骨髓抑制情况；采用数字成像对所有动物进行随访，以评估创面愈合进程；分别于治疗后第7、14、21和30天获取全层组织活检样本。
**研究结果**：与仅接受热烧伤造模的动物相比，全身辐射组动物出现显著的一过性中性粒细胞减少症与血小板减少症，其中中性粒细胞谷值平均为0.79 × 10³/μl（治疗后第15天），血小板谷值平均为60 × 10³/μl（治疗后第12天）。清创与治疗后约28天内，创面通过收缩及创缘上皮化的联合方式实现闭合。接受ADRC治疗的创面再上皮化进程显著加快，治疗后第2周的再上皮化面积较对照组平均提升3.5倍。该加速进程同时伴随血管密度平均提升67%，以及基质（胶原蛋白）沉积量平均增加30%。无论是直接创面注射还是静脉注射ADRC，均可获得相似的实验结果。
**研究结论**：尽管本研究属于初步探索，但本研究构建了一种可重复的热烧伤合并骨髓抑制性全身辐射的小型猪模型，该模型采用标准化流程，可用于评估针对简易核装置袭击后潜在救治需求的新型防护措施。