Mapping putative enhancers in mouse oocytes and early embryos reveals TCF3/12 as key folliculogenesis regulators.

Dynamic epigenomic reprogramming occurs during mammalian oocyte maturation and early development. However, the underlying transcription circuitry remains poorly characterized. By mapping cis-regulatory elements using H3K27ac, we identified putative enhancers in mouse oocytes and early embryos distinct from those in adult tissues, enabling global transitions of regulatory landscapes around fertilization and implantation. Gene deserts harbour prevalent putative enhancers in fully grown oocytes linked to oocyte-specific genes and repeat activation. Embryo-specific enhancers are primed before zygotic genome activation and are restricted by oocyte-inherited H3K27me3. Putative enhancers in oocytes often manifest H3K4me3, bidirectional transcription, Pol II binding and can drive transcription in STARR-seq and a reporter assay. Finally, motif analysis of these elements identified crucial regulators of oogenesis, TCF3 and TCF12, the deficiency of which impairs activation of key oocyte genes and folliculogenesis. These data reveal distinctive regulatory landscapes and their interacting transcription factors that underpin the development of mammalian oocytes and early embryos.

Fabrication of the SiC/HfC Composite Aerogel with Ultra-Low Thermal Conductivity and Excellent Compressive Strength.

Aerogels, as a new type of high-temperature-resistant insulation material, find extensive application in aerospace, high-temperature industrial furnaces, new energy batteries, and various other domains, yet still face some limitations such as inadequate temperature resistance and pronounced brittleness. In this work, SiC/HfC composite aerogels were prepared through a combination of sol-gel method, atmospheric pressure drying technique, and carbothermal reduction reaction. The effects of different molar ratios, calcination time, and temperatures on the microstructural features and physicochemical properties of the resulting SiC/HfC composite aerogels were investigated. The aerogel exhibited an elevated BET-specific surface area of 279.75 m2/g, while the sample displayed an extraordinarily low thermal conductivity of 0.052 W/(m·K). Most notably, the compressive strength reached an outstanding 5.93 MPa after a carbonization temperature of 1500 °C, far exceeding the values reported in prior aerogel studies. This research provided an innovative approach for advancing the development of carbide aerogels in the realm of high-temperature applications.

Impact of Anterior and Posterior Vault Distraction Osteogenesis (A-PVDO) and 3D-Printed Positioning/Shaping Templates in Apert Syndrome: A Case Series Study.

OBJECTIVE: This study seeks to examine the impact of anterior and posterior vault distraction osteogenesis (A-PVDO) in conjunction with 3D-printed positioning and shaping templates for the management of Apert syndrome. METHODS: From January 2018 to February 2022, a retrospective analysis was conducted on 6 cases of Apert syndrome employing fronto-orbital 3D-printed positioning and molding templates. The cranium underwent surgical modification in accordance with the template's configuration and was affixed with absorbable plates. Subsequently, distraction devices were applied, encompassing both anterior and posterior craniotomies. The evaluation encompassed clinical outcomes, complications (including cerebrospinal fluid leakage and infection), safety, and the feasibility of the distraction osteogenesis procedure. RESULTS: Six patients diagnosed with Apert syndrome underwent treatment involving the integration of fronto-orbital 3D-printed positioning and shaping templates in conjunction with anterior and posterior cranial distraction osteoplasty. Follow-up durations ranged from 18 to 32 months (average: 22 mo). No instances of fronto-orbital retraction, cerebrospinal fluid leakage, or intracranial infection were noted during the follow-up period. The sole reported complication entailed an infection at the extension rod site in 1 case. All patients conveyed satisfaction with the treatment outcomes. CONCLUSIONS: The application of 3D-printed positioning and shaping templates in tandem with anterior and posterior cranial distraction osteogenesis demonstrates efficacy in addressing Apert syndrome. Notably, significant enhancements in head shape and orbit were observed, and the incidence of postoperative complications such as cerebrospinal fluid leakage and infection remained minimal. Moreover, long-term follow-up affirmed stability.

Repair of cervicothoracic skin defects with extra-long transverse cervical flaps by stepwise pressure packing in children: a technical innovation.

Objective: To investigate the clinical effect of prolonging predilated transverse cervical flap with stepwise pressure packing for neck and chest lesions in children. Methods: A retrospective review of children with large cervicothoracic lesions admitted to our department from January 2011 to June 2021 was conducted to compare stepwise pressure packing with normal dressing in the surgical method of transverse cervical pedicled flaps after expansion. Among 58 included children, 22 (14 males and 8 females) were allocated to the extended and expanded transverse cervical flap with stepwise compression dressing group, and 36 (19 males and 17 females) to the transverse cervical flap group. The causes of skin defects were: scars (37 cases) and giant nevus (21 cases). The course of the disease ranged from 0.5 to 8 years. The two groups were compared in terms of child satisfaction, the occurrence of infection, recurrence of the contracture, secondary operation, and repaired area. Results: In 22 cases of extended transverse cervical flaps, 8 cases were embedded with two expanders, resulting in a total of 30 expanded flaps, which were successfully transferred to the neck and chest without necrosis at the distal end of compression, with good effect. Comparison of pedicled transverse cervical flaps with stepwise pressure packing and pedicled transverse cervical flaps alone revealed no significant difference in child satisfaction, the occurrence of infection, recurrence of the contracture, and secondary surgery (all P > 0.05). Yet, there was a significant difference in the repair area between two groups (P < 0.05). Conclusion: Prolongation of pedicled cervical flaps after expansion with stepwise pressure packing resulted in an effective method for repairing the large skin defect of children's face and neck caused by various diseases. In terms of increasing neck repair area, the operation with stepwise pressure dressing was significantly superior to the simple packing.

Cellular senescence contributes to mechanical ventilation-induced diaphragm dysfunction by upregulating p53 signalling pathways.

BACKGROUND: Mechanical ventilation can cause acute atrophy and injury in the diaphragm, which are related to adverse clinical results. However, the underlying mechanisms of ventilation-induced diaphragm dysfunction (VIDD) have not been well elucidated. The current study aimed to explore the role of cellular senescence in VIDD. METHODS: A total of twelve New Zealand rabbits were randomly divided into 2 groups: (1) spontaneously breathing anaesthetized animals (the CON group) and (2) mechanically ventilated animals (for 48 h) in V-ACV mode (the MV group). Respiratory parameters were collected during ventilation. Diaphragm were collected for further analyses. RESULTS: Compared to those in the CON group, the percentage and density of sarcomere disruption in the MV group were much higher (p < 0.001, both). The mRNA expression of MAFbx and MuRF1 was upregulated in the MV group (p = 0.003 and p = 0.006, respectively). Compared to that in the CON group, the expression of MAFbx and MuRF1 detected by western blotting was also upregulated (p = 0.02 and p = 0.03, respectively). Moreover, RNA-seq showed that genes associated with senescence were remarkably enriched in the MV group. The mRNA expression of related genes was further verified by q-PCR (Pai1: p = 0.009; MMP9: p = 0.008). Transverse cross-sections of diaphragm myofibrils in the MV group showed more intensive positive staining of SA-ßGal than those in the CON group. p53-p21 axis signalling was elevated in the MV group. The mRNA expression of p53 and p21 was significantly upregulated (p = 0.02 and p = 0.05, respectively). The western blot results also showed upregulation of p53 and p21 protein expression (p = 0.03 and p = 0.05, respectively). Moreover, the p21-positive staining in immunofluorescence and immunohistochemistry in the MV group was much more intense than that in the CON group (p < 0.001, both). CONCLUSIONS: In a rabbit model, we demonstrated that mechanical ventilation in A/C mode for 48 h can still significantly induce ultrastructural damage and atrophy of the diaphragm. Moreover, p53-dependent senescence might play a role in mechanical ventilation-induced dysfunction. These findings might provide novel therapeutic targets for VIDD.

Facile Preparation of a Novel HfC Aerogel with Low Thermal Conductivity and Excellent Mechanical Properties.

Aerogels emerge as captivating contenders within the realm of high-temperature thermal resistance and thermal insulation. Nevertheless, their practical applications are usually constrained by their inherent brittleness when subjected to rigorous conditions. Herein, employing hafnium dichloride oxide octahydrate (HfOCl2·8H2O) as the hafnium source and resorcinol-formaldehyde (RF) as the carbon precursor, hafnium carbide (HfC) aerogels are fabricated via the sol-gel method complemented with carbothermal reduction reaction. Investigations are conducted into the effects of various molar ratios, duration, and temperatures of calcination on the microstructural features and physico-chemical characteristics of the as-prepared HfC aerogel. The aerogel shows a high BET-specific surface area (601.02 m2/g), which is much larger than those of previously reported aerogels. Furthermore, the HfC aerogel exhibits a low thermal conductivity of 0.053 W/(m·K) and a compressive strength of up to 6.12 MPa after carbothermal reduction at 1500 °C. These excellent thermal insulation and mechanical properties ensure it is ideal for the utilization of high-temperature thermal resistance and thermal insulation in the fields of aerospace.

Temporospatial inhibition of Erk signaling is required for lymphatic valve formation.

Intraluminal lymphatic valves (LVs) and lymphovenous valves (LVVs) are critical to ensure the unidirectional flow of lymphatic fluid. Morphological abnormalities in these valves always cause lymph or blood reflux, and result in lymphedema. However, the underlying molecular mechanism of valve development remains poorly understood. We here report the implication of Efnb2-Ephb4-Rasa1 regulated Erk signaling axis in lymphatic valve development with identification of two new valve structures. Dynamic monitoring of phospho-Erk activity indicated that Erk signaling is spatiotemporally inhibited in some lymphatic endothelial cells (LECs) during the valve cell specification. Inhibition of Erk signaling via simultaneous depletion of zygotic erk1 and erk2 or treatment with MEK inhibitor selumetinib causes lymphatic vessel hypoplasia and lymphatic valve hyperplasia, suggesting opposite roles of Erk signaling during these two processes. ephb4b mutants, efnb2a;efnb2b or rasa1a;rasa1b double mutants all have defective LVs and LVVs and exhibit blood reflux into lymphatic vessels with an edema phenotype. Importantly, the valve defects in ephb4b or rasa1a;rasa1b mutants are mitigated with high-level gata2 expression in the presence of MEK inhibitors. Therefore, Efnb2-Ephb4 signaling acts to suppress Erk activation in valve-forming cells to promote valve specification upstream of Rasa1. Not only do our findings reveal a molecular mechanism of lymphatic valve formation, but also provide a basis for the treatment of lymphatic disorders.

Measurement of the normal mandible in neonates in east China.

Objective: We aimed to measure the related indicators of the neonatal mandible in East China. This provides basic data for the study of the mandible position and morphology of normal newborns and can also provide data support for the diagnosis, evaluation, and treatment of the Pierre Robin sequence. Methods: First, we collected the CT data of normal neonates at the Nanjing Children's Hospital Affiliated with Nanjing Medical University between January 2013 and January 2019. The data included the maxilla and mandible, and neonates had no craniomaxillofacial-related malformation. We exported the data in DICOM format. In the second step, we imported the data into MIMICS 21.0 to reconstruct the data into a 3D model, and then we used the model to measure the different measurement items. Specific measurement items were as follows: ① Measurement of the angle α: We imported the CT data of the neonate into the software and reconstructed a 3D model. We observed the 3D model to find the left and right gonions (LGo and RGo) and the Menton (Me) and used the angle measurement tool of the software to appoint Me as the apex, and we connected the points LGo, Me, and RGo as angle α. ② Measurement of the distance between the left and right gonions: The distance measurement tool of the software was used to measure the distance between the bilateral gonions as a. ③ Measurement of the distance from the Me to the line between LGo and RGo: The LGo and RGo were connected as a line on the 3D model, then the distance between Me and the line was measured as b. ④ Measurement of the distance between the upper and lower jaw: The median sagittal view was found and the distance c between the foremost point of the upper jaw and the foremost point of the lower jaw was measured. We imported the measurement results into the SPSS software for statistical analysis. Results: Specific measurement results: ① Angle α: 86.34 ± 8.58°. ② Distance a: 63.63 ± 6.83 mm. ③ Distance b: 31.99 ± 3.70 mm. ④ Distance c: 2.28 ± 1.04 mm. Among all the above indicators, there was no statistical difference between gender. Conclusions: In this study, 132 neonates were initially screened, of which 117 met the inclusion criteria and were finally included. There were 69 male and 48 female neonates. The indicators α, a, b, and c showed no statistical differences between male and female neonates; therefore, we combined the results to obtain the normal reference value: angle α: 86.34 ± 8.58°; distance a: 63.63 ± 6.83 mm; distance b: 31.99 ± 3.70 mm; distance c: 2.28 ± 1.04 mm.

Closure of Giant Dorsal Lumbosacral Myelomeningocele in Children Using Double Expanded Flaps: A Case Report and Literature Review.

INTRODUCTION: Myelomeningocele (MMC) is the most common neural tube defect that can occur due to neural tube's failure to fuse properly during embryonic life. To prevent this, expanded flaps can be used for closure of large MMCs. PRESENTATION OF CASE: A 4-year and 6-month girl was diagnosed with multiple congenital anomalies including hydrocephalus, dorsal lumbosacral MMC, and congenital tethered cord syndrome. Preoperative evaluation showed no lower limb movements and the size of the sacrococcygeal region was about 10 cm × 8 cm × 15 cm mass, prominent thoracic kyphosis, and no obvious urogenital or limb anomalies. The large dorsal lumbosacral MMC was treated with a double expanded flap to reconstruct, the soft tissue defect following the neurosurgical reconstruction. DISCUSSION: The expanded flap was deemed as viable as all wounds were healed without any complications, such as dehiscence, leakage of cerebrospinal fluid, or infection. The technique described in the case report offers an effective method of closure. CONCLUSION: This flap can be an effective method for reconstruction of large dorsal lumbosacral MMC defects that might improve outcomes and minimize complications. It also ensures minimal wound tension and breakdown.

Role of UDP-glucose ceramide glucosyltransferase in venous malformation.

Venous malformation (VM) results from the abnormal growth of the vasculature; however, the detailed molecular mechanism remains unclear. As a glycosyltransferase, UDP-glucose ceramide glucosyltransferase (UGCG) is localized to the Golgi body and is a key enzyme in the first step of glycosphingolipid synthesis. Here, we aimed to explore the relationship between UGCG and the development of VM. First, investigations using RT-qPCR and Western blotting on the diseased vasculature of VM patients and normal vascular tissues revealed that UGCG expression was markedly elevated in the diseased vessels. Subsequently, immunofluorescence assay showed that UGCG was co-localized with CD31, an endothelial cell marker, in tissues from patients with VM and healthy subjects. Then, we established TIE2-L914F-mutant human umbilical vein endothelial cells (HUVECs) by lentivirus transfection. Next, Western blotting revealed that UGCG expression was considerably higher in HUVECsTIE2-L914F. In addition, we established a UGCG-overexpressing HUVECs line by plasmid transfection. With the CCK8 cell proliferation experiment, wound healing assay, and tube formation assay, we found that UGCG could promote the proliferation, migration, and tube formation activity of HUVECs, whereas the inhibition of UGCG could inhibit the proliferation, migration, and tube formation activity of HUVECsTIE2-L914F. Finally, Western blotting revealed that UGCG regulates the AKT/mTOR pathway in HUVECs. These data demonstrated that UGCG can affect the activity of vascular endothelial cells and regulate the AKT/mTOR signaling pathway; this is a potential mechanism underlying VM pathogenesis.

Protocol for imaging nuclear pore complexes on isolated nuclei of zebrafish early embryos by field emission scanning electron microscopy.

Here, we present a protocol to observe the three-dimensional surface of nuclear pore complexes (NPCs) of vertebrate early embryos by field emission scanning electron microscopy (FESEM). We describe steps from zebrafish early embryo collection and nuclei exposure to FESEM sample preparation and final NPC state analysis. This approach provides an easy way to observe surface morphology of NPCs from the cytoplasmic side. Alternatively, additional purification steps after nuclei exposure supply intact nuclei for further mass spectrometry analysis or other utilization. For complete details on the use and execution of this protocol, please refer to Shen et al.1.

Optimizing surgical management of iatrogenic bile duct injury: transhepatic percutaneous cholangial drainage combined with end-to-end biliary anastomosis.

Iatrogenic bile duct injury remains the most severe complication of gallbladder surgeries. To reduce post-operation complication, we introduce an improved approach for bile duct injury repairment, named transhepatic percutaneous cholangial drainage (TPCD) which combined with end-to-end biliary anastomosis. Clinical data obtained from 12 patients between February 2012 and May 2022 were retrospectively analyzed. Patient demographic, clinical, operative, and follow-up data were analyzed using descriptive statistics. All injuries were repaired successfully and no fatal cases occurred. The mean operative time and hospital stay duration were 367.5 ± 103.2 min and 11.3 ± 3.5 days, respectively. In two cases (16.7%), bile leakage occurred at the bile duct anastomosis site. Three patients (25.0%) developed low-grade fever and one patient (8.3%) developed a postoperative infection of the incision site. No postoperative bleeding or bile duct strictures occurred in any of the cases. The patients were followed up from 12 to 122 months (median, 70.5 months). No cholangitis or bile duct restenosis was observed after biliary drainage tube removal. There were no long-term bile duct-related complications seen in the follow-up time. It is safe and feasible for TPCD combined with end-to-end biliary anastomosis using in bile duct injury.

Accuracy and safety of robotic navigation-assisted distraction osteogenesis for hemifacial microsomia.

Introduction: This study aimed to verify the accuracy and safety of distraction osteogenesis for hemifacial microsomia assisted by a robotic navigation system based on artificial intelligence. Methods: The small sample early-phase single-arm clinical study, available at http://www.chictr.org.cn/index.aspx, included children aged three years and older diagnosed with unilateral hemifacial microsomia (Pruzansky-Kaban type II). A preoperative design was performed, and an intelligent robotic navigation system assisted in the intraoperative osteotomy. The primary outcome was the accuracy of distraction osteogenesis, including the positional and angular errors of the osteotomy plane and the distractor, by comparing the preoperative design plan with the actual images one week postoperatively. Perioperative indicators, pain scales, satisfaction scales, and complications at one week were also analyzed. Results: Four cases (mean 6.5 years, 3 type IIa and 1 type IIb deformity) were included. According to the craniofacial images one week after surgery, the osteotomy plane positional error was 1.77 ± 0.12 mm, and the angular error was 8.94 ± 4.13°. The positional error of the distractor was 3.67 ± 0.23 mm, and the angular error was 8.13 ± 2.73°. Postoperative patient satisfaction was high, and no adverse events occurred. Discussion: The robotic navigation-assisted distraction osteogenesis in hemifacial microsomia is safe, and the operational precision meets clinical requirements. Its clinical application potential is to be further explored and validated.

Occurrence of Rhabdomyosarcoma After Surgery Combined with oral Sirolimus for Mixed Vascular Malformation of the Tongue.

Vascular malformation is the general term of a kind of lesions originated from lymphatic vessels and vascular tissues, which contains a variety of components called mixed vascular malformation. Rhabdomyosarcoma (RMS) is a kind of soft tissue sarcoma, originating from striated muscle cells or mesenchymal cells. RMS and vascular malformation mostly occur in children, and common in the head and neck, but their simultaneous occurrence is rare. A 9-year-old boy who was hospitalized for a second attack of combined vascular malformation: hemolymphangioma. The child experienced severe upper airway obstruction and tongue bleeding. Postoperative pathology demonstrated hemolymphangioma combined with RMS. Subsequently, he was transferred to the oncology department for chemotherapy and lately died of RMS with lung metastasis. The secondary RMS may be related to the usage of sirolimus. Because of its uncertain border, vascular malformation in the oral and maxillofacial region is difficult to completely remove by surgical resection, and local recurrence could be often observed. Due to its rapid progress and continuous bleeding, the possibility of malignant tumor should be considered and multidisciplinary comprehensive treatment should be actively taken. Besides, family history of related malignant tumors and immune function should be investigated in detail before choosing the application of oral sirolimus.

Posterior Cranial Retraction Combined With Bilateral Parietal Distraction for Children With Nonsyndromic Craniosynostosis.

BACKGROUND: The nonsyndromic craniosynostosis is the most common of craniosynostoses in childhood. There are many treatments. We aim to treat 12 cases of nonsyndromic craniosynostosis via posterior cranial vault distraction osteogenesis combined with bilateral parietal distraction. METHODS: Data of a total of 12 patients (7 boys and 5 girls) with nonsyndromic sagittal synostosis who underwent distraction osteogenesis between January 2015 and August 2020 were retrospectively analyzed. Bilateral parietal bone flaps and posterior occipital flaps were designed and cut. Then, distraction device was placed, which was distracted at 5 days after surgery (twice per day, 0.4-0.6 mm/d, and lasting for 10-15 days). After 6 months of fixation, the secondary surgery was performed to remove the device. RESULTS: The scaphocephaly was corrected, and the appearance was satisfactory. Postoperative follow-up time was 6 to 14 months, with an average of 10 months, and the mean CI was 63.2 and 78.25 before and after surgery, respectively; the mean anterior-posterior skull diameter was shortened (12.63 ± 3.47) mm, the transverse diameter of both temporal regions was lengthened (15.4 ± 4.18) mm, and the scaphocephalic deformity was significantly improved. There was no detachment or rupture of the extender postoperatively. No severe complications, such as radiation necrosis or intracranial infection, were observed. CONCLUSION: Posterior cranial retraction combined with bilateral parietal distraction in children with nonsyndromic craniosynostosis, in which the proposed technique did not exhibit severe complications, and it is worthy of further promotion and application in clinical practice.

3D printing personalized guide plate in the management of recurrent intramuscular venous malformations: A single center experience.

OBJECTIVE: This study aimed to investigate the feasibility and effectiveness of 3D printing personalized guide plate in the management of recurrent intramuscular venous malformations (IVM). METHODS: Fifteen patients with recurrent IVM were retrospectively assessed. 3D-slicer software was used to extract and reconstruct the imaging data from CT and/or MRI to highlight the morphology, size, and puncture depth of the lesion. With the guidance of personalized plate, complete excision of the IVM was adopted along the pre-marked (methylene blue, MB) margin. RESULTS: Personalized guide plate matched involved extremity well, and MB-puncture approach was consistent with preoperative design. All IVMs were removed radically in one single session. Complete pain relief was obtained in all cases postoperatively. CONCLUSION: The application of 3D printing guide plate can be safe, effective, and reliable to confirming the precise margin of IVM, renders a promising technique with a high practical value in resection of recurrent lesion.

Exercise pretreatment alleviates neuroinflammation and oxidative stress by TFEB-mediated autophagic flux in mice with ischemic stroke.

BACKGROUND: Neuroinflammation and oxidative stress are important pathological mechanisms underlying cerebral ischemic stroke. Increasing evidence suggests that regulation autophagy in ischemic stroke may improve neurological functions. In this study, we aimed to explore whether exercise pretreatment attenuates neuroinflammation and oxidative stress in ischemic stroke by improving autophagic flux. METHODS: 2,3,5-Triphenyltetrazolium chloride staining was used to determine the infarction volume, and modified Neurological Severity Scores and rotarod test were used to evaluate neurological functions after ischemic stroke. The levels of oxidative stress, neuroinflammation, neuronal apoptosis and degradation, autophagic flux, and signaling pathway proteins were determined using immunofluorescence, dihydroethidium, TUNEL, and Fluoro-Jade B staining, western blotting, and co-immunoprecipitation. RESULTS: Our results showed that, in middle cerebral artery occlusion (MCAO) mice, exercise pretreatment improved neurological functions and defective autophagy, and reduced neuroinflammation and oxidative stress. Mechanistically, after using chloroquine, impaired autophagy abolished the neuroprotection of exercise pretreatment. And transcription factor EB (TFEB) activation mediated by exercise pretreatment contributes to improving autophagic flux after MCAO. Furthermore, we showed that TFEB activation mediated by exercise pretreatment in MCAO was regulated by the AMPK-mTOR and AMPK-FOXO3a-SKP2-CARM1 signaling pathways. CONCLUSIONS: Exercise pretreatment has the potential to improve the prognosis of ischemic stroke patients, and it can exert neuroprotective effects in ischemic stroke by inhibiting neuroinflammation and oxidative stress, which might be due to the TFEB-mediated autophagic flux. And targeting autophagic flux may be promising strategies for the treatment of ischemic stroke.

PEEP application during mechanical ventilation contributes to fibrosis in the diaphragm.

BACKGROUND: Positive end-expiratory airway pressure (PEEP) is a potent component of management for patients receiving mechanical ventilation (MV). However, PEEP may cause the development of diaphragm remodeling, making it difficult for patients to be weaned from MV. The current study aimed to explore the role of PEEP in VIDD. METHODS: Eighteen adult male New Zealand rabbits were divided into three groups at random: nonventilated animals (the CON group), animals with volume-assist/control mode without/ with PEEP 8 cmH2O (the MV group/ the MV + PEEP group) for 48 h with mechanical ventilation. Ventilator parameters and diaphragm were collected during the experiment for further analysis. RESULTS: There was no difference among the three groups in arterial blood gas and the diaphragmatic excursion during the experiment. The tidal volume, respiratory rate and minute ventilation were similar in MV + PEEP group and MV group. Airway peak pressure in MV + PEEP group was significantly higher than that in MV group (p < 0.001), and mechanical power was significantly higher (p < 0.001). RNA-seq showed that genes associated with fibrosis were enriched in the MV + PEEP group. This results were further confirmed on mRNA expression. As shown by Masson's trichrome staining, there was more collagen fiber in the MV + PEEP group than that in the MV group (p = 0.001). Sirius red staining showed more positive staining of total collagen fibers and type I/III fibers in the MV + PEEP group (p = 0.001; p = 0.001). The western blot results also showed upregulation of collagen types 1A1, III, 6A1 and 6A2 in the MV + PEEP group compared to the MV group (p < 0.001, all). Moreover, the positive immunofluorescence of COL III in the MV + PEEP group was more intense (p = 0.003). Furthermore, the expression of TGF-ß1, one of the most potent fibrogenic factors, was upregulated at both the mRNA and protein levels in the MV + PEEP group (mRNA: p = 0.03; protein: p = 0.04). CONCLUSIONS: We demonstrated that PEEP application for 48 h in mechanically ventilated rabbits will cause collagen deposition and fibrosis in the diaphragm. Moreover, activation of the TGF-ß1 signaling pathway and myofibroblast differentiation may be the potential mechanism of this diaphragmatic fibrosis. These findings might provide novel therapeutic targets for PEEP application-induced diaphragm dysfunction.