Feasibility of pedicled vascularized inguinal lymph node transfer in a mouse model: A preliminary study

Treatment of Rat Lymphedema by Propeller Lymphatic Tissue Flap Combined with Nanofibrillar Collagen Scaffolds

BACKGROUND

 The aim of our study was to evaluate a new propeller vascularized lymphatic tissue flap (pVLNT) combined with aligned nanofibrillar collagen scaffolds (CS) (BioBridge) in reducing lymphedema in the rat lymphedema model.

METHODS

 Unilateral left hindlimb lymphedema was created in 15 female Sprague-Dawley rats following inguinal and popliteal lymph nodes (LN) resection and radiation. An inguinal pVLNT was elevated from the contralateral groin and transferred through a skin tunnel to the affected groin. Four collagen threads were attached to the flap and inserted in the hindlimb at the subcutaneous level in a fan shape. The three study groups consisted of group A (control), group B (pVLNT), and group C (pVLNT + CS). Volumetric analysis of both hindlimbs was performed using micro-computed tomography imaging before the surgery (at initial time point) and then at 1 and 4 months, postoperatively, and the relative volume difference (excess volume) was measured for each animal. Lymphatic drainage was assessed by indocyanine green (ICG) fluoroscopy for number and morphology of new collectors and the time required for ICG to move from injection point to the midline.

RESULTS

 Four months after the induction of lymphedema, an increased relative volume difference remained in group A (5.32 ± 4.74%), while there was a significant relative volume reduction in group B (-13.39 ± 8.55%) and an even greater reduction in group C (-14.56 ± 5.04%). ICG fluoroscopy proved the functional restoration of lymphatic vessels and viability of pVLNT in both B and C groups. Notably, only group C demonstrated statistically significant improvements in lymphatic pattern/morphology and in the number of lymphatic collectors as compared with the control group A.

CONCLUSION

 The pedicle lymphatic tissue flap combined with SC is an effective procedure for the treatment of lymphedema in rats. It can be easily translated into treatment of humans' lower and upper limb lymphedema and further clinical studies are warranted.

Sentinel node restoration by vascularized lymph node transfer in mice

BACKGROUND

Recent reports have indicated that vascularized lymph node transfer (VLNT) may improve the impaired immunity in lymphedema but there has been no report concerning anti-cancer immunity. In the early tumor immune response, dendritic cells (DCs) participate in tumor recognition and antigen presentation in local lymphatics. Here, we investigated the impact of VLNT on DC dynamics against cancer in mouse models.

METHODS

Forty-seven 8-week-old C57BL/6 N male mice were divided into three surgical groups: a VLNT model in which a vascularized inguinal lymph node (LN) flap was transferred into the ipsilateral fossa after a popliteal LN was removed; a LN dissection (LND) model in which the popliteal LN was dissected; and a control model in which a skin incision was made at the popliteal fossa and an ipsilateral inguinal LN was removed. Postoperative lymphatic flows were observed by indocyanine green lymphography and B16-F10-luc2 mouse melanoma were implanted into the ipsilateral footpad. The proportion of DCs in the transplanted nodes was measured by CD11c immunohistochemistry using digital imaging analysis 4 days after cancer implantation. Metastases to the lungs and LNs were quantitatively evaluated by luciferase assay 4 weeks after cancer implantation.

RESULTS

After VLNT, lymphatic reconnection was observed in 59.2% of mice. The proportion of DCs was significantly higher in the VLNT group with lymphatic reconnection (8.6% ± 1.0%) than in the naïve LN (4.3% ± 0.4%) (p < .001). The tumor burden of lung metastases was significantly less in the VLNT group with lymphatic reconnection compared with the LND group (p = .049).

CONCLUSIONS

Metastasis decreased in mice with reconnected lymphatics after VLNT. A possible explanation was that lymphatic restoration may have contributed to the tumor immune response by allowing DC migration to LNs.

Restoration of lymph flow by flap transfer can prevent severe lower extremity lymphedema after inguino-pelvic lymphadenectomy

PURPOSE

Severe lymphedema is difficult to treat because of the associated extensive scar formation. Therefore, preventing scar formation might alleviate the severity of lymphedema following lymphadenectomy. In this study, we evaluated the usefulness of flap transfer, performed immediately after lymphadenectomy, for preventing scar formation.

METHODS

Twenty-three patients with subcutaneous malignancy in a lower extremity, who underwent inguino-pelvic lymphadenectomy, were divided into groups based on whether flap transfer was performed. The severity of lymphedema was categorized according to the ratio of the circumference of the affected extremity to that of the unaffected extremity, as mild (< 20% increase in volume), moderate (20-40%), or severe (> 40%).

RESULTS

In the 18 patients who underwent lymphadenectomy without flap transfer, lymphedema was classified as mild in 7, moderate in 7, and severe in 4. In the five patients who underwent lymphadenectomy with flap transfer, lymphedema was classified as mild in 4 and moderate in 1. This difference between the groups did not reach significance.

CONCLUSIONS

The findings of this study suggest that flap transfer may help prevent scar formation and contribute to the restoration of lymph flow after lymphadenectomy.

Anatomy and relationships of forelimb lymph nodes in Sprague-Dawley rats: A detailed dissecting approach

Background

Constructing a reliable animal model for preclinical treatment of secondary lymphedema is challenging because the anatomical characteristics near the lymph nodes are understudied. Therefore, this study examined the detailed anatomical relationship between the axillary lymph node flaps (ALNFs) and brachial lymph node flaps (BLNFs) in the forelimb of Sprague-Dawley (SD) rats.

Materials and methods

Ten male rats, weighing 250–300 g, were used. The ALNFs and BLNFs on either side of the rat forelimbs were dissected. The two lymph node flaps (LNFs) were immediately harvested to analyze their physical characteristics (via imaging process software) and microscopic structure (via histology examinations).

Results

A total of 20 ALNFs and BLNFs from 10 rats were harvested and analyzed. ALNF dissection was simpler and lasted a shorter time than BLNF dissection (p < 0.0001). The left LNFs were more difficult to dissect than the right LNFs (p < 0.0001). In physical characteristics of LNFs, the area (p < 0.001) of LNFs and the number of lymph nodes (p < 0.0001) associated with ALNFs were greater than those associated with BLNFs, but the pedicle lengths of ALNFs were shorter than that of BLNFs (p < 0.0001). No significant difference in the diameter of the venous and arterial pedicles was noted between the two LNFs (p > 0.05).

Conclusion

This study reported detailed physical characteristics of ALNFs and BLNFs in SD rat forelimbs, assessing the respective area of LNFs, number of lymph nodes, and lengths and diameters of vascular pedicles. Moreover, this study suggested an efficient method to perform a study of LNFs by describing the operation process and repeatedly measuring the operation time.

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.

Animal Models Used in the Research of Vascularized Lymph Node Transfer: A Systematic Review

BACKGROUND

Lymphedema is a common adverse consequence of breast cancer therapy, while still relatively little is known about its pathophysiology. Several treatment options emerged over the past decades, and among them, vascularized lymph node transfer (VLNT) seems to be particularly promising. Animal models are indispensable to improve our understanding of the underlying processes surrounding the transplantation of a vascularized lymph node. This review aimed to systematically evaluate animal models of VLNT and compare their advantages and disadvantages.

MATERIALS AND METHODS

A systematic review of literature in the Scopus, Web of Science, and Ovid MEDLINE databases was conducted according to the PRISMA guidelines to identify all studies on animal models used for the research of VLNT. The algorithm used in search of articles was "Vascularized Lymph Node Transfer" AND "Model". Articles were manually verified for relevance to the topic. The resulting models were assessed for their suitability for VLNT research.

RESULTS

The literature search yielded a total of 233 studies after duplicates removal. Of those, 217 were excluded based on title and abstract review. Another study was excluded after reviewing the full-text article leaving 15 eligible studies to be included in this review article.

CONCLUSIONS

Rats were found to be the most dominantly used animal model in the VLNT research, although other models had their benefits. The main areas of study were the functionality of VLNT within or without a preinduced lymphedema, its response to ischemia, and clarification of lymphatic pathways reestablishment following VLNT.

Mesenteric Lymph Node Transplantation in Mice to Study Immune Responses of the Gastrointestinal Tract

Mesenteric lymph nodes (mLNs) are sentinel sites of enteral immunosurveillance and immune homeostasis. Immune cells from the gastrointestinal tract (GIT) are constantly recruited to the mLNs in steady-state and under inflammatory conditions resulting in the induction of tolerance and immune cells activation, respectively. Surgical dissection and transplantation of lymph nodes (LN) is a technique that has supported seminal work to study LN function and is useful to investigate resident stromal and endothelial cell biology and their cellular interactions in experimental disease models. Here, we provide a detailed protocol of syngeneic mLN transplantation and report assays to analyze effective mLN engraftment in congenic recipients. Transplanted mLNs allow to study T cell activation and proliferation in preclinical mouse models. Donor mLNs proved viable and functional after surgical transplantation and regenerated blood and lymphatic vessels. Immune cells from the host completely colonized the transplanted mLNs within 7-8 weeks after the surgical intervention. After allogeneic hematopoietic cell transplantation (allo-HCT), adoptively transferred allogeneic CD4+ T cells from FVB/N (H-2q) mice homed to the transplanted mLNs in C57BL/6 (H-2b) recipients during the initiation phase of acute graft-versus-host disease (aGvHD). These CD4+ T cells retained full proliferative capacity and upregulated effector and gut homing molecules comparable to those in mLNs from unmanipulated wild-type recipients. Wild type mLNs transplanted into MHCII deficient syngeneic hosts sufficed to activate alloreactive T cells upon allogeneic hematopoietic cell transplantation, even in the absence of MHCII+ CD11c+ myeloid cells. These data support that orthotopically transplanted mLNs maintain physiological functions after transplantation. The technique of LN transplantation can be applied to study migratory and resident cell compartment interactions in mLNs as well as immune reactions from and to the gut under inflammatory and non-inflammatory conditions.

Changes in high endothelial venules in lymph nodes after vascularized and nonvascularized lymph node transfer in a murine autograft model

BACKGROUND AND OBJECTIVES

Vascularized lymph node transfer (LNT) is gaining popularity in the treatment of lymphedema. However, it is unclear whether the vascularization of transferred lymph nodes (LNs) contributes to functional improvement. High endothelial venules (HEVs) are specialized vessels that allow lymphocytes to enter LNs. In this study, we compared the numbers of HEVs and lymphocytes in LNs after vascularized and nonvascularized LNT.

METHODS

Fifty mice were divided into three groups (group 1, pedicled vascularized LNT; group 2, pedicled nonvascularized LNT; group 3, free nonvascularized LNT). Afferent lymphatic reconnection was confirmed by patent blue staining. The transferred LNs were harvested 4 weeks after surgery. HEVs, B-cells, and T-cells were subjected to immunohistochemical staining and quantified.

RESULTS

Afferent lymphatic reconnection was observed in 13 of 20 transferred LNs in group 1, 11 of 15 in group 2, and 7 of 15 in group 3. The ratio of dilated/total HEVs in transferred LNs with afferent lymphatic reconnection was significantly higher in group 1 than in groups 2 and 3. No significant differences in numbers of B-cells and T-cells were found in the transferred LNs.

CONCLUSIONS

We found that more functional HEVs were preserved in cases with successful afferent lymphatic reconnection after vascularized LNT than after nonvascularized LNT.