A global bibliometric and visualized analysis in the status and trends of corneal tissue engineering research from 1991 to 2021.

Corneal tissue engineering has developed rapidly in recent years, with a large number of publications emerging worldwide. This study focused on exploring the global status and research trends in this field. Publications related to corneal tissue engineering from 1991 to 2021 were acquired from the Science Citation Index-Expanded (SCI-Expanded) of Web of Science (WoS). Firstly, the VOS viewer software was chosen for visualizing bibliometric networks, including bibliographic coupling analysis, co-citation analysis, co-authorship analysis, and co-occurrence analysis, and the CiteSpace software was used to detect burst keywords. Subsequently, the publication trends in corneal tissue engineering research were also predicted. In present study, 953 publications were selected and analyzed. The number of annual publications was increasing globally and was predicted to continue the current trend. While Japan ranked top 1 in terms of average citation, the USA contributed the most to the corneal tissue engineering research with highest number of citations and highest H-index. The journal of Biomaterials contributed the largest publication number. The top-ranked institutions were National University of Singapore and Singapore National Eye Center. Additionally, researches could be manually divided into four clusters: "biomaterial related research," "cell related research," "transplantation therapy," and "mechanism research on biomaterials." Specifically, the research topic "hydrogel" was predicted to be hotspots which may help researchers to explore new directions for future research.

The Use of Infrared Thermography in Determining Timing for Early Pedicle Division of the Preexpanded Bipedicled Visor Flap after Ischemic Preconditioning.

Background: The preexpanded bipedicled visor flap, supported by the bilateral superficial temporal vessels, stands as an ideal choice for upper and lower lip reconstruction in males. However, the bilateral tissue bridges after flap transfer caused patients significant cosmetic deformity and psychological burden. Early division of bilateral pedicles reduced the length of hospitalization and expenses. In this study, infrared thermography (IRT) was used to guide the early pedicle division after ischemic preconditioning. Methods: This study retrospectively analyzed patients who underwent preexpanded bipedicled visor flap surgery from April 2018 to October 2021. Pedicle division was scheduled at two weeks postflap transfer. Ischemic preconditioning was initiated 3-5 days in advance by repeatedly clamping both pedicles. The temperature alteration of the flap and the temperature difference compared to the normal adjacent tissue were evaluated by IRT. The division surgery was not scheduled until the perfusion assessment indicated adequate. This comprised of subjective examination and indocyanine green angiography. The threshold of temperature difference to determine the pedicle division was analyzed based on the temperature changes between the clamps. Results: A total of 8 male patients successfully conducted the pedicle division without any complications. The delay period after ischemic preconditioning ranged from 14 to 19 days (average 16 days). Through ischemic preconditioning training, the average temperature of the flap gradually increased from 31.85 ± 0.36°C to 33.89 ± 0.50°C, and the temperature difference with the normal surrounding tissues decreased from 2.89 ± 0.30°C to 1.15 ± 0.46°C (95% confidence interval (1.5, 0.8)). The temperature difference stayed unchanged after pedicle division. Conclusion: Ischemic preconditioning shortens the perioperative period to pedicle division. Monitoring the temperature change reflects the revascularization between the flap and the recipient site, thus guiding the pedicle division. The temperature difference less than 1.5°C after clamping both pedicles can be set as the safe threshold for pedicle division.

An Innovative and Economical Device for Ischemic Preconditioning of the Forehead Flap Prior to Pedicle Division: A Comparative Study.

BACKGROUND: Ischemic preconditioning of the forehead flap prior to pedicle division helps to improve angiogenesis. Clamping the pedicle by a clamped rubber band with vessel forceps is often clinically applied. However, the severe pain and unstable blocking effect influenced the preconditioning process. In this study, we described an innovative device designed for ischemic preconditioning and compared its efficacy with the clamped rubber band. METHODS: The device consists of a self-locking nylon cable tie with a buckle and a rubber tube. The rubber tube is fed over the cable tie to act as a soft outer lining and the cable tie is tightened across the pedicle to block the perfusion for ischemic preconditioning. This device and the standard clamped rubber band were applied respectively before division surgery. The constriction effect, reliability, reproducibility, and the patients' pain tolerance were compared. RESULTS: A total of 20 forehead flaps were included. The cable tie had less incidence of loosening (7.7% vs. 16.6%, p < 0.05) and maintained the pressure more effectively. The pain score for the nylon cable tie was significantly lower than the clamped rubber band (4.25 ± 1.02 vs. 6.75 ± 1.12, p < 0.05), especially for 10 pediatric patients (4.50 ± 0.85 vs. 8.10 ± 1.20, p < 0.01). All 20 pedicles were successfully divided at 19 to 22 days with no surgical complications. CONCLUSION: Compared with the clamped rubber band, the cable tie produces a more reliable and reproducible ischemic preconditioning effect. It is also better tolerated by the patients. Therefore, we recommend using the nylon cable tie as the preferred device for ischemic preconditioning of the forehead flap.

Infrared thermography-guided designing and harvesting of pre-expanded pedicled flap for head and neck reconstruction.

BACKGROUND: Pre-expanded pedicled flaps possess a more flexible transfer pattern and higher tissue utilization than random flaps, but the perfusion is fully dependent on the chosen axial vessels. A precise mapping of the vessels would assist the surgical design and increase the likelihood of success. The application of Infrared thermography (IRT) has been previously reported for perforator location. The aim of this study is to report the use of IRT in mapping the course and distribution of axial vessels in the pre-expanded flap to guide the designing and harvesting. METHODS: Patients who underwent head and neck reconstruction using pre-expanded flaps were included. After tissue expansion, IRT was used to mark the vessel distribution along the expanded flap. The results were compared with color Doppler ultrasound (CDU) and/or computed tomographic angiography (CTA). The flap was designed and raised based on the pre-operative marking by IRT. The mark was verified intraoperatively. RESULTS: A total of 26 expanded flaps were performed, including 20 pedicled flaps and 6 free flaps. IRT succeeded to map the vessel distribution in all cases. All marked results were verified by CDU, CTA, and intraoperative dissection (26/26, 100%). IRT showed more comprehensive distribution of vascular branches than CDU or CTA, and could be utilized intraoperatively to identify the arteries. CONCLUSION: IRT provides accurate and comprehensive mapping of the axial vessel distribution in the pre-expanded flaps, assisting with flap design and harvest. It is easy to use and non-invasive as an important tool pre- or intraoperatively to ensure the safe elevation.

Development of Animal Models for Lens and Corneal Diseases Using N-Methyl-N-Nitrosourea.

Purpose: N-methyl-N-nitrosourea (MNU) is an alkylating toxicant with potent mutagenic ability. This study was designed to induce apoptosis in lens epithelial cells (LECs) and corneal endothelial cells (CECs) via MNU administration. We sought to build ocular disease models of cataract and corneal endothelial decompensation. Methods: MNU was delivered into the intraperitoneal cavities of neonatal rats and the anterior chambers of adult rabbits. The MNU-treated animals were then subjected to a series of functional and morphological analyses at various time points. Results: MNU treatment induced pervasive apoptosis of LECs and CECs. These effects were dose and time dependent. Mature cataracts were found in neonatal rats 3 weeks after MNU treatment. Histological analysis revealed that MNU toxicity induced swelling, vacuolation, and liquefaction in lens fibers of MNU-treated rats. Pentacam examination showed that the average density of rat lens increased significantly after MNU administration. Terminal deoxynucleotidyl transferase-mediated nick end labeling (TUNEL) analysis showed pervasive apoptotic staining in the lenses of MNU-treated rats. In rabbit eyes, intracameral treatment with MNU induced corneal edema and significantly increased central corneal thickness, which peaked at P14. Morphological and immunohistochemical analysis showed that CECs were effectively ablated in the MNU-treated rabbits. The expression of 8-OHdG increased significantly in the cornea of MNU-treated rabbits, compared with vehicle-treated controls. Conclusions: MNU is sufficient to induce ocular cell apoptosis in animal models. These models of MNU-induced cataract and corneal endothelial decompensation represent valuable tools for efforts to develop relevant therapies.

A Prospective Comparative Study of Color Doppler Ultrasound and Infrared Thermography in the Detection of Perforators for Anterolateral Thigh Flaps.

BACKGROUND: Preoperative localization of the perforators allows precise planning of the flap design and improves surgical efficiency. Recently, infrared thermography is introduced as a reliable alternative, where the perforator corresponds to the "hot spot" on the thermogram. This study aims to compare the application of color Doppler ultrasound (CDU) and infrared thermography in preoperative perforator mapping of the anterolateral thigh (ALT) perforator flap. PATIENTS AND METHODS: From September 2017 to January 2019, CDU and infrared thermography were both applied on 20 patients to locate the perforators originated from lateral circumflex femoral artery preoperatively. The perforators identified using each modality were marked on the anterolateral thigh region. The accuracy of both mapping methods was analyzed according to the intraoperative findings. The relation between location bias and the thickness of subcutaneous tissue was analyzed. RESULTS: A total of 20 ALT flaps were included. Fifty-three perforators were detected by CDU, and 51 "hot spots" were identified by infrared thermography, in which 50 "hot spots" corresponded to CDU, and the consistency test showed that the κ index was 0.712 (P < 0.05), representing high consistency. The infrared thermography has a sensitivity of 94.3% and a specificity of 85.7% compared with CDU. The deviation between thermal imaging and CDU was positively correlated with the thickness of the subcutaneous tissue. The Pearson correlation coefficient was 0.84 (R = 0.84). Forty-four perforators marked by CDU were selected for designing the flap. Anatomical findings showed that the accuracy rate of CDU and infrared thermal was 93.2% (41 of 44) and 86.3% (38 of 44), respectively. There was no statistical difference (P > 0.05). CONCLUSIONS: Compared with CDU, infrared thermography can be used to locate perforators, in this case, the ALT perforators, with a high degree of consistency. It is portable, economical, noninvasive, and easy to operate. It has higher accuracy in patients with thinner subcutaneous tissue. We believe that infrared thermography can be a useful technique for perforator mapping, especially in patients where the subcutaneous tissue is thinner.