Does ischemic preconditioning increase flap survival by ADORA2B receptor activation?

BACKGROUND: Ischemic preconditioning (IPC) is defined as raising tolerance to subsequent ischemic stress by exposing tissues to sub-lethal ischemia. Although many candidates have been suggested, recent studies have clearly demonstrated that adenosine-mediated ADORA2B receptor (ADORA2BR) activation is the main mechanism involved in IPC. While the tissue-protective role of this mechanism has been demonstrated in different ischemia/reperfusion (I/R) models, its role in flap surgery-derived I/R damage has not to date been investigated. OBJECTIVE: To investigate the role of adenosine and ADORA2BR activation in IPC-mediated tissue protection in an epigastric flap model. METHODS: Animals were divided into five main groups, all of which were then divided into two subgroups depending on whether or not they were exposed to IPC before the I/R procedure, which consisted of 6 hours of ischemia and 6 days of reperfusion. No drugs were administered in Group 1 (the control group). Animals in Group 2 were pretreated with CD73-inhibitor before IPC application or the ischemic period. Animals in Group 3 were pretreated with adenosine. Animals in Group 4 were pretreated with an ADORA2BR antagonist, and those in Group 5 with an ADORA2BR agonist. After 6 days of reperfusion, tissue survival was evaluated via histological and macroscopic analysis. RESULTS: IPC application significantly enhanced CD73 expressions and adenosine concentrations (p < 0.01). Flap survivals were increased by IPC in Group 1 (p < 0.05). However, CD73 inhibition blocked this increase (Group 2). In Group 3, adenosine improved flap survival even in the absence of IPC (p < 0.01). While an ADORA2BR antagonist attenuated the tissue-protective effect of IPC (p < 0.01), the ADORA2BR agonist improved flap survival by mimicking IPC in groups 4 and 5. CONCLUSION: These results provide pharmacological evidence for a contribution of CD73 enzyme-dependent adenosine generation and signaling through ADORA2BR to IPC-mediated tissue protection. They also suggest for the first time that ADORA2BR agonists may be used as a potential preventive therapy against I/R injury in flap surgeries.

Functional lower lip reconstruction with the partial latissimus dorsi muscle free flap without nerve coaptation.

BACKGROUND: The repair of extensive lower lip defects is difficult due to the presence of both functional and esthetic requirements. This report describes functional lip repair using the partial latissimus dorsi free flap without nerve coaptation. METHODS: Reconstruction of the lower lip due to subtotal and total tissue defects was performed using latissimus dorsi free flap on twelve patients, between 2013 and 2017. The etiology was squamous cell carcinoma in six patients, malignant melanoma in one, firearm injury in three and microstomia in two. Following exposure of the lip defect, the partial latissumus dorsi muscle flap was harvested and transfered into the lower lip defect. The microvascular anastomoses was done and no nerve coaptation was performed. The muscle was covered with a skin graft taken from the thigh for mucosal and skin lining. Functional outcomes were assessed using physical examination, electromyography (EMG), electroneuromyography, cold/warm and pain sensation, two point discrimination (TPD), and Semmes Weinstein (SMW) tests. RESULTS: Postoperative course was uneventful for all of the flaps. Patients were followed for between fifteen months and four years (mean 28.2 months).Color match between the flap and the face and functional outcome was satisfactory. Reinnervation was detected at EMG in eleven patients undergoing surgery six months postoperatively.After 1 year, the patients demonstrated quite normal results of the test with SMW and TDP results. None of patients perceived both hot and cold sensation. CONCLUSION: The technique is an alternative option in lower lip reconstruction since it provides satisfactory functional and esthetic results despite absence of any neural coaptation.

Circumflex scapular artery myocutaneous and/or vascularized scapular chimeric flap.

BACKGROUND: Chimeric osteomyocutaneous flaps harvested from the subscapular artery system have been used in clinical practice. We describe the use of a novel circumflex scapular artery myocutaneous and/or vascularized scapular chimeric flap in a rat model and demonstrate optimal skin flap dimensions. MATERIALS AND METHODS: An 8 × 4-cm-rectangular skin flap based on the circumflex scapular artery flap was harvested, and the mean percentage of the surviving flap area and the necrotic area were calculated to be 71% ± 17.9% and 29% ± 17.9%, respectively. Using flap dimensions determined in the first part of our study, a 4 × 3-cm quadrangular portion of skin was marked over the scapula, and the serratus anterior muscle and a portion of the scapular bone were included in our chimeric flap model. RESULTS: The mean percentages of the surviving flap and necrotic areas were 74% ± 6% and 25% ± 6%, respectively. Microangiographic and histologic studies revealed the vascularity of the skin island and identified the branches of the circumflex scapular artery that supplied the bone and muscle. CONCLUSIONS: The circumflex scapular artery myocutaneous and/or vascularized partial scapular chimeric flap may be considered a branch-based chimeric flap and can be an acceptable flap model due to its simplicity, reliability, and consistent vascularity. Furthermore, this flap may have potential applications in studying chimeric flap hemodynamics.