Objective: To explore the mechanism of dendritic epidermal T lymphocytes (DETCs) in promoting healing of full-thickness skin defect wound on mice by regulating the proliferation and differentiation of epidermal stem cells (ESCs) in mice. Methods: (1) Ten 8-week-old wild type (WT) male C57BL/6 mice (the same sex and kind below) were sacrificed to collect the skin of back for extracting DETCs to culture. Five WT and five 8-week-old T cell receptor (TCR) δ(-)/(-) mice were selected and enrolled in WT control group and TCR δ(-)/(-) control group, respectively. A full-thickness skin defect wound with diameter of 6 mm was made on both sides of spinal line on the back of mice without any treatment after injury. Another fifteen 8-week-old TCR δ(-)/(-) mice were selected and divided into phosphate buffer solution (PBS), DETC, and insulin-like growth factor-Ⅰ(IGF-Ⅰ) groups according to the random number table (the same grouping method below), with 5 mice in each group, and the same full-thickness skin defect wound was made on each mouse. Immediately after injury, mice in PBS, DETC, and IGF-Ⅰ groups were injected subcutaneously around each wound with 10 μL sterile PBS , DETCs (cell concentration of 1×10(6)/mL), and 5 mg/mL recombinant mice IGF-Ⅰ, respectively. The percentage of the residual wound area was calculated on post injury day (PID) 2, 4, 6, and 8. (2) Three 8-week-old WT mice were enrolled in WT control group and nine 8-week-old TCR δ(-)/(-) mice were divided into TCR δ(-)/(-) control group, PBS group, and DETC group, with 3 mice in each group. The full-thickness skin defect wound was made as in experiment (1) . On PID 3, the protein expression of IGF-Ⅰ in the epidermis tissue of wound margin was detected by chemiluminescence imaging analyzer. (3) Three 8-week-old WT mice were enrolled in WT control group and six 8-week-old TCR δ(-)/(-) mice were divided into PBS and DETC groups, with 3 mice in each group, and the full-thickness skin defect wound was made as in experiment (1). On PID3, DETCs were extracted from the wound margin epidermis tissue to detect the percentage of DETCs expressing IGF-Ⅰ by flow cytometer. (4) The mice were taken as in experiment (2) and divided into WT control, PBS, DETC, and IGF-Ⅰ groups. A straight full-thickness skin defect incision with length of 3 cm was made in the direction of one inner ear. Mice in WT control group didn't have any other treatment after injury, and immediately after injury, mice in PBS, DETC, and IGF-Ⅰ groups were injected subcutaneously around each wound with 10 μL sterile PBS, DETCs (cell concentration of 1×10(6)/mL), and 5 mg/mL recombinant mice IGF-Ⅰ, respectively. On PID 12, epidermis tissue of wound margin was collected, and immunofluorescence staining was performed to observe the number of keratin 15 positive cells. (5) The same mice were collected, grouped, and treated as in experiment (4). On PID12, the epidermis tissue of wound margin was collected and immunofluorescence staining was performed to observe the number of keratin 10 positive cells. (6) Twenty 3-day-old WT mice (the same below) were sacrificed to collect the whole skin, which was used to extract ESCs, with 5 mice detecting one index. The ESCs were divided into DETC co-culture group and control group, which were added with 1 mL DETCs (cell concentration of 1.25×10(6)/mL) and DETC medium, respectively. The percentage of 5-ethynyl-2'-deoxyuridine (EdU) positive cell on culture day (CD) 3, the percentages of CD49f(+) CD71(-) and keratin 14 positive cells on CD 5, and the percentage of keratin 10 positive cell on CD 10 in 2 groups were detected by flow cytometer. (7) Twenty mice were taken to extract ESCs, with 5 mice detecting one index. The ESCs were divided into control group and IGF-Ⅰ group, which were added with 1 mL sterile PBS and 10 ng/mL recombinant mice IGF-Ⅰ, respectively. The percentages of EdU positive cell, CD49f(+) CD71(-) cell, keratin10 positive cell, and keratin 14 positive cell were detected as in experiment (6). The sample in each group of experiments (6) and (7) was three. Data were statistically analyzed with analysis of variance for repeated measurement, one-way analysis of variance, and t test. Results: (1) On PID 4, 6, and 8, the percentage of residual wound area in TCR δ(-)/(-) control group was significantly higher than that in WT control group (t=2.78, 3.39, 3.66, P<0.05 or P<0.01). The percentage of residual wound area in DETC group and IGF-Ⅰgroup on PID 4, 6, and 8 was apparently lower than that in PBS group (t=2.61, 3.21, 3.88, 2.84, 2.91, 2.49, P<0.05 or P<0.01). (2) On PID 3, the protein expression of IGF-Ⅰ in the epidermis tissue of wound margin of mice in TCR δ(-)/(-) control group was significantly lower than that in WT control group (t=17.34, P<0.01). The protein expression of IGF-Ⅰ in the epidermis tissue of wound margin of mice in DETC group was significantly higher than that in PBS group (t=11.71, P<0.01). (3) On PID 3, the percentage of DETCs expressing IGF-Ⅰ in the epidermis tissue of wound margin of mice in PBS group was significantly lower than that in WT control group and DETC group (t=24.95, 27.23, P<0.01). (4) On PID 12, the number of keratin 15 positive cells in the epidermis tissue of wound margin of mice in PBS group was significantly lower than that in WT control group, DETC group, and IGF-Ⅰ group (t=17.97, 11.95, 7.63, P<0.01). (5) The number of keratin 10 positive cells in the epidermis tissue of wound margin of mice in PBS group was significantly higher than that in WT control group, DETC group, and IGF-Ⅰ group (t=11.59, 9.51, 3.48, P<0.05 or P<0.01). (6) The percentages of EdU positive cells on CD 3, CD49f(+) CD71(-) cells on CD 5, and keratin 14 positive cells on CD 5 in DETC co-culture group were respectively (43.5±0.6)%, (66.5±0.5)%, (69.3±1.7)%, apparently higher than (32.3±1.3)%, (56.4±0.3)%, (54.9±1.3)% in control group (t=7.97, 17.10, 6.66, P<0.01). The percentage of keratin 10 positive cells on CD 10 in DETC co-culture group was (55.7±0.7)%, significantly lower than (67.1±1.2)% in control group (t=8.34, P<0.01). (7) The percentages of EdU positive cells on CD 3, CD49f(+) CD71(-) cells on CD 5, and keratin 14 positive cells on CD 5 in IGF-Ⅰ group were respectively (42.1±0.9)%, (81.1±1.3)%, (66.8±1.0)%, apparently higher than (32.4±0.7)%, (74.9±0.7)%, (52.0±1.9)% in control group (t=8.39, 4.24, 7.25, P<0.05 or P<0.01). The percentage of keratin 10 positive cells on CD 10 in IGF-Ⅰ group was (53.5±1.1)% , significantly lower than (58.2±0.3)% in control group (t=3.99, P<0.05). Conclusions: DETCs can promote the proliferation and anti-apoptotic potential of ESCs and inhibit their differentiation into end-stage by secreting IGF-Ⅰ, thus promoting wound healing of full-thickness skin defects in mice.
目的： 探讨树突状表皮T细胞(DETC)调节小鼠表皮干细胞增殖和分化，促进小鼠全层皮肤缺损创面愈合的机制。 方法： (1)取10只8周龄野生型雄性C57BL/6(品系和性别下同)小鼠，剪取整块背部皮肤，分离培养DETC。取5只8周龄野生型小鼠设为野生对照组，5只8周龄T细胞受体(TCR)δ(-)/(-)型小鼠设为TCRδ(-)/(-)对照组，于背部脊柱线两侧各制作一个直径为6 mm的全层皮肤缺损创面，伤后不做任何处理。另取15只8周龄TCRδ(-)/(-)型小鼠，按随机数字表法(分组方法下同)分为磷酸盐缓冲液(PBS)组、DETC组和胰岛素样生长因子Ⅰ(IGF-Ⅰ)组，每组5只，同前制作全层皮肤缺损创面，伤后即刻，分别于每个创面周围皮下注射10 μL无菌PBS、DETC(细胞浓度为1×10(6)个/mL)、5 mg/mL重组小鼠IGF-Ⅰ。伤后2、4、6、8 d，计算剩余创面面积百分比。(2)取3只8周龄野生型小鼠，设为野生对照组。另取9只8周龄TCRδ(-)/(-)型小鼠，分为TCRδ(-)/(-)对照组、PBS组和DETC组，每组3只，同实验(1)制作全层皮肤缺损创面。伤后3 d，化学发光成像分析仪检测创缘表皮组织IGF-Ⅰ蛋白表达水平。(3)取3只8周龄野生型小鼠，设为野生对照组。另取6只8周龄TCRδ(-)/(-)型小鼠，分为PBS组和DETC组，每组3只，同实验(1)制作全层皮肤缺损创面。伤后3 d，取创缘表皮组织，分离DETC，流式细胞仪检测表达IGF-Ⅰ的DETC百分比。(4)同实验(2)取小鼠并分为野生对照组、PBS组、DETC组、IGF-Ⅰ组，在任意一侧耳朵朝内耳方向做一长3 cm的直线切口，深达皮肤全层。野生对照组小鼠伤后不进行任何处理，DETC组、IGF-Ⅰ组、PBS组小鼠伤后即刻分别于创面周围皮下注射10 μL DETC(细胞浓度为1×10(6)个/mL)、5 mg/mL重组小鼠IGF-Ⅰ、无菌PBS。伤后12 d，取创缘表皮组织，免疫荧光染色观察角蛋白15阳性细胞数。(5)同实验(4)取小鼠并进行分组、处理。伤后12 d，取创缘表皮组织，免疫荧光染色观察角蛋白10阳性细胞数。(6)取20只3 d龄野生型小鼠(下同)，每个指标检测取5只，剪取全身皮肤，分离培养表皮干细胞，分为对照组、DETC共培养组。DETC共培养组细胞加入1 mL DETC(细胞浓度为1.25×10(6)个/mL)，对照组细胞加入1 mL DETC培养基，培养3 d，流式细胞仪(下同)检测5-乙炔基-2′-脱氧尿苷(EdU)阳性细胞百分比；培养5 d，检测CD49f(＋)CD71(-)细胞百分比、角蛋白14阳性细胞百分比；培养10 d，检测角蛋白10阳性细胞百分比。(7)取20只小鼠，每个指标检测取5只，分离培养表皮干细胞，分为对照组和IGF-Ⅰ组。IGF-Ⅰ组细胞加入1 mL重组小鼠IGF-Ⅰ(10 ng/mL)，对照组细胞加入1 mL无菌PBS，同实验(6)检测EdU阳性细胞百分比、CD49f(＋)CD71(-)细胞百分比、角蛋白14阳性细胞百分比、角蛋白10阳性细胞百分比。实验(6)和(7)各组样本数均为3。对数据行重复测量方差分析、单因素方差分析、t检验。 结果： (1)伤后4、6、8 d，TCRδ(-)/(-)对照组小鼠剩余创面面积百分比显著高于野生对照组(t＝2.78、3.39、3.66，P<0.05或P<0.01)；DETC组、IGF-Ⅰ组小鼠剩余创面面积百分比显著低于PBS组(t＝2.61、3.21、3.88，2.84、2.91、2.49，P<0.05或P<0.01)。(2)伤后3 d，TCRδ(-)/(-)对照组小鼠创缘表皮组织中IGF-Ⅰ蛋白表达水平显著低于野生对照组(t＝17.34，P<0.01)。DETC组小鼠创缘表皮组织中IGF-Ⅰ蛋白表达水平显著高于PBS组(t＝11.71，P<0.01)。(3)伤后3 d，PBS组小鼠创缘表皮组织中表达IGF-Ⅰ的DETC百分比显著低于野生对照组和DETC组(t＝24.95、27.23，P<0.01)。(4)伤后12 d，PBS组小鼠创缘表皮组织中角蛋白15阳性细胞数显著少于野生对照组、DETC组和IGF-Ⅰ组(t＝17.97、11.95、7.63，P<0.01)。(5)PBS组小鼠创缘表皮组织中角蛋白10阳性细胞数显著多于野生对照组、DETC组和IGF-Ⅰ组(t＝11.59、9.51、3.48，P<0.05或P<0.01)。(6)DETC共培养组培养3 d EdU阳性细胞百分比、培养5 d CD49f(＋)CD71(-)细胞百分比、培养5 d角蛋白14阳性细胞百分比分别为(43.5±0.6)%、(66.5±0.5)%、(69.3±1.7)%，显著高于对照组的(32.3±1.3)%、(56.4±0.3)%、(54.9±1.3)%，t＝7.97、17.10、6.66，P<0.01。DETC共培养组培养10 d角蛋白10阳性细胞百分比为(55.7±0.7)%，显著低于对照组的(67.1±1.2)%，t＝8.34, P<0.01。(7)IGF-Ⅰ组培养3 d EdU阳性细胞百分比、培养5 d CD49f(＋)CD71(-)细胞百分比、培养5 d角蛋白14阳性细胞百分比分别为(42.1±0.9)%、(81.1±1.3)%、(66.8±1.0)%，显著高于对照组的(32.4±0.7)%、(74.9±0.7)%、(52.0±1.9)%，t＝8.39、4.24、7.25，P<0.05或P<0.01。IGF-Ⅰ组培养10 d角蛋白10阳性细胞百分比为(53.5±1.1)%，显著低于对照组的(58.2±0.3)%，t＝3.99, P<0.05。 结论： DETC通过分泌IGF-Ⅰ促进表皮干细胞的增殖和抗凋亡潜能并抑制其向终末期细胞分化，从而促进小鼠全层皮肤缺损创面愈合。.
Keywords: Cell differentiation; Cell proliferation; Dendritic epidermal T lymphocyte; Insulin-like growth factor Ⅰ; Wound healing; Wounds and injuries.