Impacts of arterial ischemia or venous occlusion on vascularized groin lymph nodes in a rat model

Clinical and Histological Effects of Partial Blood Flow Impairment in Vascularized Lymph Node Transfer

Regarding vascularized lymph node transfer (VLNT) for lymphedema, partial blood flow impairment in transferred lymph node (LN) flaps may adversely affect the therapeutic results. We investigated the clinical and histological effects of partial blood flow impairment in LN flaps. In upper extremity lymphedema cases, based on ultrasonographic examination at 2 weeks after VLNT, we compared the treatment results depending on whether the postoperative blood flow in transferred LNs was good (Group G) or poor (Group P). Novel partial ischemia and congestion of LN flap mouse models were developed to determine their histological features. In 42 cases, significant differences were observed between Group G (n = 37) and Group P (n = 5) based on the amount of volume reduction (136.7 ± 91.7 mL and 55.4 ± 60.4 mL, respectively; p = 0.04) and lymph flow recanalization rate in indocyanine green fluorescent lymphography (67.6% and 0%, respectively; p = 0.0007). In mouse models, thrombi formation in the marginal sinus and numerous Myl9/12-positive immunocompetent cells in follicles were observed in congested LNs. Blood flow maintenance in the transferred LNs is an essential factor influencing the therapeutic effect of VLNT. Postoperatively, surgeons should closely monitor blood flow in the transferred LNs, particularly in cases of congestion.

Distal facial vein catheterization for prevention and management of thrombosis in vascularized lymph node transfers

BACKGROUND

This study investigated the outcomes of the distal facial vein catheterization (DFVC) to manage venous thrombosis in vascularized submental lymph nodes (VSLN) flap transplantations.

METHODS

Between March 2017 and December 2020, patients who underwent VSLN flaps were divided into Group I: combined delayed primary retention sutures (DPRS) with DFVC, and Group II: DPRS alone. Primary outcomes were early (within 72 h) and late venous thrombosis. Secondary outcomes included other nonvascular complications and mechanical factors of the thrombosis.

RESULTS

A total of 105 patients who underwent 106 VSLN flaps, including 37 and 69 flaps in Groups I and II, respectively, were included. There were no statistically significant differences in age, body mass index, Taiwan lymphoscintigraphy staging, and surgical factors between the two groups (all p > 0.05). Early venous thrombosis requiring re-exploration developed in one (2.7%) and three (4.3%) flaps in Groups I and II, respectively (p = 0.20). One flap (2.7%) and eight (11.5%) flaps developed late venous thrombosis in Groups I and II, respectively (p < 0.01). There was no statistically significant difference in total complication rates between both groups (p = 0.9).

CONCLUSION

VSLN flap transplantation had a significantly higher risk of late venous thrombosis. DFVC significantly decreased the late venous thrombosis.

Long-term outcomes of arterial ischemia or venous occlusion on vascularized groin lymph nodes in a rat model

BACKGROUND

This study investigated the long-term effects of arterial ischemia and venous occlusion on lymph node drainage function in a rat model.

METHODS

Bilateral groin lymph node flaps of 18 Lewis rats were dissected. The pedicle artery was clamped for 4, 5, and 6 h (A4, A5, and A6 groups), and the vein for 3, 4, and 5 h (V3, V4, and V5 groups) in six flaps. At 4 weeks, the evaluations included gross morphomics, indocyanine green (ICG) lymphography, histological section, immunofluorescence of terminal deoxynucleotidyl transferase assay, and heme oxygenase-1 (HO-1) stain.

RESULTS

The lymph node flaps developed shrinkage and partial necrosis in A5, A6, V4, and V5 groups. Hemorrhage in the lymph node cortex and medulla was observed histologically in A5, A6, and V5 groups. ICG lymphography showed loss of lymphatic drainage function in 2 of 6 flaps in A6 and V5 groups. Cell death was shown partly in cortical follicles in A5 and V4 groups and completely in A6 and V5 groups. The HO-1 expression was statistically increased in A5 and V5 groups, respectively (p < 0.05).

CONCLUSIONS

The critical arterial ischemia and venous occlusion time were 4 h at 4 weeks of follow-up.

Lower Limb Lymphedema Patients Can Still Benefit from Supermicrosurgical Lymphaticovenous Anastomosis (LVA) after Vascularized Lymph Node Flap Transfer (VLNT) as Delayed Lymphatic Reconstruction-A Retrospective Cohort Study

Background: For lymphedema patients who received a vascularized lymph node flap transfer (VLNT) as their primary treatment, what are the treatment options when they seek further improvement? With recent publications supporting the use of lymphaticovenous anastomosis (LVA) for treating severe lymphedema, we examined whether LVA could benefit post-VLNT patients seeking further improvement. Methods: This retrospective cohort study enrolled eight lymphedema patients with nine lymphedematous limbs (one patient suffered from bilateral lower limb lymphedema) who had received VLNT as their primary surgery. Patients with previous LVA, liposuction, excisional therapy, or incomplete data were excluded. LVA was performed on nine lower lymphedematous limbs. Demographic data and intraoperative findings were recorded. Preoperative and postoperative limb volumes were measured with magnetic resonance volumetry. The primary outcome was the limb volume measured 6 months post-LVA. Results: The median duration of lymphedema before LVA was 10.5 (4.9–15.3) years. The median waiting time between VLNT and LVA was 41.4 (22.3–97.9) months. The median volume gained in the lymphedematous limb was 3836 (2505–4584) milliliters (mL). The median post-LVA follow-up period was 18 (6–30) months. Significant 6-month and 1-year post-LVA percentage volume reductions were found compared to pre-LVA volume (both p < 0.001). Conclusion: Based on the results from this study, the authors recommend the use of LVA as a secondary procedure for post-VLNT patients seeking further improvement.

Short-term molecular and cellular effects of ischemia/reperfusion on vascularized lymph node flaps in rats

Vascularized lymph node (VLN) transfer is an emerging strategy to re-establish lymphatic drainage in chronic lymphedema. However, the biological processes underlying lymph node integration remain elusive. This study introduces an experimental approach facilitating the analysis of short-term molecular and cellular effects of ischemia/reperfusion on VLN flaps. Lymph node flaps were dissected pedicled on the lateral thoracic vessels in 44 Lewis rats. VLN flaps were exposed to 45 or 120 minutes ischemia by in situ clamping of the vascular pedicle with subsequent reperfusion for 24 hours. Flaps not exposed to ischemia/reperfusion served as controls. Lymph nodes and the perinodal adipose tissue were separately analyzed by Western blot for the expression of lymphangiogenic and angiogenic growth factors. Moreover, morphology, microvessel density, proliferation, apoptosis and immune cell infiltration of VLN flaps were further assessed by histology and immunohistochemistry. Ischemia for 120 minutes was associated with a markedly reduced cellularity of lymph nodes but not of the perinodal adipose tissue. In line with this, ischemic lymph nodes exhibited a significantly lower microvessel density and an increased expression of VEGF-D and VEGF-A. However, VEGF-C expression was not upregulated. In contrast, analyses of the perinodal adipose tissue revealed a more subtle decrease of microvessel density, while only the expression of VEGF-D was increased. Moreover, after 120 minutes ischemia, lymph nodes but not the perinodal adipose tissue exhibited significantly higher numbers of proliferating and apoptotic cells as well as infiltrated macrophages and neutrophilic granulocytes compared with non-ischemic flaps. Taken together, lymph nodes of VLN flaps are highly susceptible to ischemia/reperfusion injury. In contrast, the perinodal adipose tissue is less prone to ischemia/reperfusion injury.

Ischemia and reperfusion injury in superficial inferior epigastric artery-based vascularized lymph node flaps

Vascularized lymph node transfer (VLNT) is a promising treatment modality for lymphedema; however, how lymphatic tissue responds to ischemia has not been well defined. This study investigates the cellular changes that occur in lymph nodes in response to ischemia and reperfusion. Lymph node containing superficial epigastric artery-based groin flaps were isolated in Prox-1 EGFP rats which permits real time identification of lymphatic tissue by green fluorescence during flap dissection. Flaps were subjected to ischemia for either 1, 2, 4, or 8 hours, by temporarily occluding the vascular pedicle. Flaps were harvested after 0 hours, 24 hours, or 5 days of reperfusion. Using EGFP signal guidance, lymph nodes were isolated from the flaps and tissue morphology, cell apoptosis, and inflammatory cytokines were quantified and analyzed via histology, immunostaining, and rtPCR. There was a significant increase in collagen deposition and tissue fibrosis in lymph nodes after 4 and 8 hours of ischemia compared to 1 and 2 hours, as assessed by picrosirius red staining. Cell apoptosis significantly increased after 4 hours of ischemia in all harvest times. In tissue subject to 4 hours of ischemia, longer reperfusion periods were associated with increased rates of CD3+ and CD45+ cell apoptosis. rtPCR analysis demonstrated significantly increased expression of CXCL1/GRO-α with 2 hours of ischemia and increased PECAM-1 and TNF-α expression with 1 hour of ischemia. Significant cell death and changes in tissue morphology do not occur until after 4 hours of ischemia; however, analysis of inflammatory biomarkers suggests that ischemia reperfusion injury can occur with as little as 2 hours of ischemia.

Efficacy validation of a lymphatic drainage device for lymphedema drainage in a rat model

BACKGROUND

Vascularized lymph node transfer (VLNT) is an effective surgery for extremity lymphedema. This study evaluated a lymphatic drainage device (LDD) for the drainage of accumulated fluid into the venous system.

METHODS

Micropore filtering membranes with pore sizes of 5, 0.65, and 0.22 μm polyvinylidene difluoride, and 0.8 μm Nylon Net Filter were evaluated to determine the in vitro efficiency of drainage flow of an LDD. The two superior membranes were further used for the evaluation of the inflow and outflow of the LDD in vivo using 5% albumin.

RESULTS

At 5 minutes, the volumes drained with 5, 0.65, and 0.22 μm polyvinylidene difluoride and 0.8 μm nylon membranes were 15.2, 2.77, 2.37, and 0.59 mL, respectively (P < .01). At 10 minutes, the collected volumes of 5 and 0.65 μm polyvinylidene difluoride were 1788 and 1051 μL (P = .3). The indocyanine green fluorescence was detected at 50 seconds for the 5 μm polyvinylidene difluoride membrane but not for the 0.65 μm membrane.

CONCLUSIONS

The study successfully demonstrated the proof-of-concept of the LDD prototype that mimicked VLNT with drainage of 5% albumin into the venous system in a rat model.

Long-term outcome of lower extremity lymphedema treated with vascularized lymph node flap transfer with or without venous complications

BACKGROUND

Vascularized submental lymph node (VSLN) transfer is an emerging approach for extremity lymphedema. This study investigated the long-term outcome and venous complications of VSLN for unilateral lower extremity lymphedema.

METHODS

Between 2010 and 2018, patients who underwent VSLN for unilateral lower extremity lymphedema were retrospectively evaluated. Patient demographics, operative records, complications, circumferential improvement, and episodes of cellulitis were analyzed. Further comparisons were performed between different types, numbers, and techniques of venous anastomoses.

RESULTS

A total of 75 VSLNs in 70 patients survived, giving a 100% success rate. Six flaps (8%) had venous complications (VC group) and 69 flaps (92%) did not (No-VC group). There were no statistical differences in types, numbers, and techniques of anastomoses between two groups (P = .65, 1, and .56, respectively). At a mean follow-up of 32.0 ± 23.0 months, mean circumferential improvement and episodes of cellulitis between two groups did not statistically differ significantly (P = .31 and .09, respectively).

CONCLUSIONS

VSLN is an effective treatment for lower extremity lymphedema. The types, numbers of veins, and techniques of venous anastomoses did not statistically affect the venous complication rates. Functional outcomes of the VSLNs were not compromised if venous complications were salvaged promptly.