| Background:Epidemiological investigations have demonstrated that the incidence and prevalence of pressure injury remain high and it has become a global health care problem.Although preventive measures focusing on existing risk factors of pressure injury have been taken,which reduces the incidence of pressure injury some content,there are still great residual risks.Therefore,it is necessary to clarify new and modifiable related factors based on the management of traditional risk factors.Traditionally,pressure injury is mainly caused by pressure-mediated ischemia-reperfusion injury（IRI）.Recent studies have found that the occurrence and progression of various IRI diseases are closely related to iron metabolism disorders.Iron is a necessary metal element for human metabolism,but excess free iron produces hydroxyl radicals through Fenton reaction(Fe2++H2O2→Fe3++OH·+OH-),which aggravates oxidative stress in the body and leads to cell and tissue damage.As an IRI disease,the correlation between the occurrence and progression of pressure injury and iron metabolism disorder is unclear.Objective:To explore and analyze the correlation between iron metabolism disorder and the occurrence and progression of pressure injury.To construct mice pressure injury models to initially explore the mechanism of pressure injury iron metabolism disorder leading to tissue damage.Method:This study consists of two parts.The first part is a population-based case-control study conducted in the Affiliated Hospital of Qingdao University:（1）Tissue collection from December 2019 to December 2021.The wound muscle tissues of 20 patients with stage 3 or stage 4 pressure injury who underwent wound debridement were collected.The wound tissue was divided into marginal tissue and necrosis tissue according to different histopathological characteristics.The waste normal tissue of 20 non-pressure injury patients who underwent fracture internal fixation removal was collected as the control group.Hematoxylin eosin staining（HE staining）,Prussian blue staining（Perl’s Blue staining）,Inductively coupled plasma mass spectrometry（ICP-MS）and the Enzyme linked immunosorbent assay（ELISA）were used to detect and compare the iron metabolism-related indicators differences in wound tissue and normal tissue:iron ion,transferrin and ferritin concentration.（2）Serum collection.Serum and clinical information were collected from 196 pressure injury patients and 196 non-pressure injury patients.The pressure injury group was divided into four subgroups:stage 1 pressure injury,stage 2 pressure injury,stage 3 pressure injury and stage 4 pressure injury.Clinical information includes demographic data（sex,age）and clinical data（multiple laboratory test indicators including serum transferrin,comorbidities,disease history of pressure injury,pain in the compression area,state of consciousness,respiratory pattern,fecal incontinence state,and information about pressure injury wounds）.Taking the occurrence of pressure injury as the dependent variable,the binary logistic regression was used to analyze the correlation between the iron metabolism indicators and the occurrence of pressure injury.The different stages of pressure injury were used as the dependent variable,and the correlation between the iron metabolism indicators and the progression of pressure injury was analyzed by ordinal logistic regression.Stratified analysis of the correlation between serum transferrin and pressure injury was showed using serum albumin levels as stratification variable.The second part is a animal experiment:construct pressure injury mice models（n=6/group）,and take the day when the modeling is successful as the 0th day of the experiment.The serum and wound muscle tissues of pressure injury mice were collected on days 1,3,7,and 14,and the serum and muscle tissue of normal mice were collected on the 0th day of the experiment.The levels of iron metabolism indicators（iron ion,transferrin and ferritin）were evaluated by ICP-MS and ELISA to verify the correlation between pressure injury and iron metabolism disorder.RNA sequencing technology and transcriptomic analysis to explore the key genes and pathway regulating pressure injury iron metabolism disorder.Result:The results of part one study:（1）Tissue analysis results:the staining results showed that compared with normal tissue,neither the wound marginal tissue nor the necrotic tissue had normal skeletal muscle fiber structure,and both wound tissue had varying degrees of inflammatory cell infiltration and iron ion deposition（P<0.05）.ICP-MS results showed that the concentration of iron ions in the wound marginal and necrotic tissues was 4.42 and 2.63 times than those in the normal tissue,respectively（P<0.05）.In addition,the iron ion concentration in the marginal tissue was significantly higher than that in the necrotic tissue,about 1.99 times（P<0.05）.ELISA analysis showed that transferrin concentration in pressure injury marginal tissues was approximately 1.42 times than that in normal tissues（P<0.05）.There was no significant difference in ferritin concentrations among normal tissue,marginal tissue and necrotic tissue（P>0.05）.（2）Analysis results of serum iron metabolism indicators:after adjustment for covariates of traditional factors related to the occurrence and progression of pressure injury,serum transferrin levels were negatively correlated with the occurrence of pressure injury（Adjusted OR=0.020,P<0.001）,and also negatively correlated with the progression of pressure injury（Adjusted OR=0.104,P<0.001）.Stratified analysis showed that in both normal and low serum albumin groups,serum transferrin was still negatively correlated with pressure injury occurrence and development（P<0.05）.The results of part two study:（1）The results of tissue iron metabolism indicators analysis,except for Model＿1d mice,the wound iron ion concentration of other pressure injury mice was significantly higher than that of normal mice（P<0.05）.The levels of both transferrin and ferritin in wound tissue of pressure injury mice were significantly higher than those of normal mice（P<0.05）.（2）Analysis of serum iron metabolism indicators:the serum transferrin levels of Model＿1d and 3d mice were significantly lower than those of normal mice（P<0.05）,and there was no significant difference in serum transferrin levels between Model＿7d and 14d mice and normal mice（P>0.05）.Except for Model＿14d mice,the serum ferritin levels of Model＿1d,3d,and 7d mice were significantly lower than those of normal mice（P<0.05）.（3）Transcriptomic analysis showed that the target genes of transferrin,ferritin light chain 1 and heme oxygenase were significantly up-regulated in pressure injury mice（P<0.05）.The biological functions corresponding to the target genes were significantly enriched in angiogenesis,oxidative stress response,cellular iron homeostasis,transferrin transport,etc.,and significantly enriched in hypoxia-inducible factor-1 signaling pathway,ferroptosis,necroptosis and other signaling pathways（P<0.05）.Conclusion:（1）There is iron metabolism disorder in pressure injury occurrence and progression.（2）Serum transferrin in patients with pressure injury was significantly lower than that in patients without pressure injury.As pressure injury progressed from stage 1 to stage 4,the depth and severity of wounds increased,and serum transferrin gradually decreased.（3）Serum transferrin levels were negatively correlated with the occurrence and progression of pressure injury. |
