Experimental Study On The Establishment Of Animal Model Of Secondary Lymphedema After Axillary Lymph Node Dissection

Objective:Secondary upper limb lymphedema(SULL)is among the most common complications after breast cancer surgery.A progressive lymphatic system disease caused by local injury of lymphatic vessels after axillary lymph node dissection and ionizing radiation therapy,SULL can cause disability and adversely impact the physical and mental health.In spite of some major progress in the diagnosis and treatment of lymphedema,post-operative lymphedema of the upper limbs remains one of the biggest challenges of clinical practice.A number of studies have been conducted involving SULL after breast cancer surgery in the hope of improving the quality of life.Building an animal model is an important step in conducting research on the treatment for SULL.To date,different animal models of SULL have been created,including models using rodents and carnivores.Although studies on the pathogenesis and treatment of lymphedema in non-primates have been encouraging,success in building a SULL model in non-primates has been limited.In addition,the physiology,anatomy,and function of the limbs in non-primates differ significantly from primates.Therefore,the results in a non-primate model cannot be directly applied to humans.The conventional non-primate model of SULL is not an ideal method to mimic the physiopathology of SULL in humans.We built a SULL model in rhesus monkeys that shares similar traits with humans with respect to physiology,anatomy,and genetics.The feasibility of building a SULL model in primates was discussed and the relevant evaluation indicators were analyzed.Methods:Healthy female rhesus monkey,4-5 years of age,were used.To mimic standard axillary lymph node dissection,ionizing radiation therapy was administered to the axillary region to cause injury of the residual lymphatic vessels 2 weeks before surgery and 4 weeks after surgery.Ultrasonography indicated non-obstructed axillary blood flow.based on which lymphedema caused by vascular factors was excluded.Changes in the circumference of the mid-forearm,elbow,and mid-upper arm were measured.Magnetic resonance imaging(MRI)lymphangiography of the upper limbs was performed.Bioelectrical impedance analysis(BIA)was used to monitor the changes in extracellular fluid volume and distribution.Morphologic changes in lymphatic vessels were observed by conventional pathologic examination.Immunohistochemical staining for lymphoepithelial markers was performed to detect the morphologic changes in lymphatic vessels.Results:1.Progressive lymphedema was observed in the operated limb and this condition persisted.The ratio of the circumference of the operated limb to the contralateral upper limb was 100%-137%within 24 months after surgery;the palm thickness increased by 15%-40%,which was typical of lymphedema.2.MRI 3 months after surgery showed significant changes in the upper limb lymphatic vessels.Compared with the contralateral normal upper limb,the lymphatic trunk disappeared in the operated limb.The lymphatic vessels were replaced by a bright,dotted pattern against a nebulous background.Lymphedema presents as an extrafascial distribution in all animals,and as hyper-intensities on T2-weighted images.High-resolution 3D gradient-echo imaging(GRE)and digital subtraction angiography(DSA)lymphangiography revealed dilated lymphatic vessels in a reticular distribution pattern with delayed lymphatic return.This finding indicated lymphangiogenesis related to obstruction.3.BIA revealed an increase in the extracellular fluid volume in the upper limbs,which was linearly related to the pathologic changes of lymphedema.4.Based on pathologic sections and immunohistochemical staining,there was an obvious increase in the number of lymphatic vessels,which were dilated,and the curvature changes of the lymphatic vessels were typical of lymphedema.Conclusions:1.It was easy to build a SULL model in rhesus monkeys and the success rate was high;2.The SULL model in rhesus monkeys can satisfactorily mimic the pathophysiologic changes in humans due to the similar genetic background.3.Evaluation of the constructed animal model can be done easily.This SULL model in primates contributes to our understanding of SULL and the development of new treatment.