Prolymphangiogenic Effects of 9-cis Retinoic Acid Are Enhanced at Sites of Lymphatic Injury and Dependent on Treatment Duration in Experimental Postsurgical Lymphedema.

Background: Patients undergoing surgical treatment for solid tumors are at risk for development of secondary lymphedema due to intraoperative lymphatic vessel injury. The damaged lymphatic vessels fail to adequately regenerate and lymphatic obstruction leads to fluid and protein accumulation in the interstitial space and chronic lymphedema develops as a result. There are currently no effective pharmacological agents that reduce the risk of developing lymphedema or treat pre-existing lymphedema, and management is largely palliative. The present study investigated the efficacy of various 9-cis retinoic acid (9-cis RA) dosing strategies in reducing postsurgical lymphedema by utilizing a well-established mouse tail lymphedema model. Methods and Results: Short-duration treatment with 9-cis RA did not demonstrate a significant reduction in postoperative tail volume, nor an improvement in lymphatic clearance. However, long-term treatment with 9-cis RA resulted in decreased overall tail volume, dermal thickness, and epidermal thickness, with an associated increase in functional lymphatic clearance and lymphatic vessel density, assessed by LYVE-1 immunostaining, compared with control. These effects were seen at the site of lymphatic injury, with no significant changes observed in uninjured sites such as ear skin and the diaphragm. Conclusions: Given the reported results indicating that 9-cis RA is a potent promoter of lymphangiogenesis and improved lymphatic clearance at sites of lymphatic injury, investigation of postoperative 9-cis RA administration to patients at high risk of developing lymphedema may demonstrate positive efficacy and reduced rates of postsurgical lymphedema.

Risk Factors for Wound Complications After Soft Tissue Sarcoma Resection.

ABSTRACT: Soft tissue sarcomas are a heterogenous group of malignant tumors that represent approximately 1% of adult malignancies. Although these tumors occur throughout the body, the majority involved the lower extremity. Management may involve amputation but more commonly often includes wide local resection by an oncologic surgeon and involvement of a plastic surgeon for reconstruction of larger and more complex defects. Postoperative wound complications are challenging for the surgeon and patient but also impact management of adjuvant chemotherapy and radiation therapy. To explore risk factors for wound complications, we reviewed our single-institution experience of lower-extremity soft tissue sarcomas from April 2009 to September 2016. We identified 127 patients for retrospective review and analysis. The proportion of patients with wound complications in the cohort was 43.3%. Most notably, compared with patients without wound complications, patients with wound complications had a higher proportion of immediate reconstruction (34.5% vs 15.3%; P = 0.05) and a marginally higher proportion who received neoadjuvant radiation (30.9% vs 16.7%; P = 0.06).

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.

Small Peptide Modulation of Fibroblast Growth Factor Receptor 3-Dependent Postnatal Lymphangiogenesis.

BACKGROUND: The fibroblast growth factor receptor (FGFR) family includes transmembrane receptors involved in a wide range of developmental and postdevelopmental biologic processes as well as a wide range of human diseases. In particular, FGFR3 has been implicated in the mechanism by which 9-cis retinoic acid (9-cisRA) induces lymphangiogenesis and improves lymphedema. The purpose of this study was to validate the efficacy of a novel small peptide FGFR3 inhibitor, peptide P3 (VSPPLTLGQLLS), and to elucidate the role of FGFR3 in 9-cisRA-induced lymphangiogenesis using this peptide. METHODS AND RESULTS: Peptide P3 effectively inhibited FGFR3 phosphorylation. In vitro, peptide P3-mediated FGFR3 inhibition did not decrease lymphatic endothelial cell (LEC) proliferation, migration, or tubule formation. However, peptide P3-mediated FGFR3 inhibition did block 9-cisRA-stimulated LEC proliferation, migration, and tubule formation. In vivo, peptide P3-mediated FGFR3 inhibition was sufficient to inhibit 9-cisRA-induced tracheal lymphangiogenesis. CONCLUSION: FGFR3 does not appear to be essential to nonpromoted LEC proliferation, migration, and tubule formation. However, FGFR3 may play a key role in LEC proliferation, migration, tubule formation, and postnatal in vivo lymphangiogenesis when pharmacologically induced by 9-cisRA. P3 may have the potential to be used as a precise regulatory control element for 9-cisRA-mediated lymphangiogenesis.

Human Acellular Dermis as Spacer for Small-Joint Arthroplasty: Analysis of Revascularization in a Rabbit Trapeziectomy Model.

BACKGROUND: Carpometacarpal joint osteoarthritis affects 8 to 12 percent of the general population. Surgical management provides symptomatic relief for 78 percent of patients who fail conservative therapy, but little consensus exists regarding which surgical procedure provides superior patient outcomes. Recent human trials substituted exogenous acellular dermal matrices in the bone space, but there are no quantitative histologic data on the outcome of acellular dermal matrices in this environment. The authors aimed to quantify the revascularization and recellularization of acellular dermal matrices in the joint space using a rabbit model. METHODS: Bilateral lunate carpal bones were surgically removed in New Zealand rabbits. Acellular dermal matrix and autologous tissue were implanted in place of the lunate of the right and left wrists, respectively. Acellular dermal matrix was also implanted subcutaneously as a nonjoint control. Histologic and immunofluorescence analysis was performed after collection at 0, 6, and 12 weeks. RESULTS: Quantitative analysis of anti-α-smooth muscle actin and CD31 immunofluorescence revealed a sequential and comparable increase of vascular lumens in joint space and subcutaneous acellular dermal matrices. In contrast, autologous tissue implanted in the joint space did not have a similar increase in α-smooth muscle actin-positive or CD31-positive lumens. Semiquantitative analysis revealed increased cellularity in both autologous and acellular dermal matrix wrist implants at each time point, whereas average cellularity of subcutaneous acellular dermal matrix peaked at 6 weeks and regressed by 12 weeks. Trichrome and Sirius red staining revealed abundant collagen at all time points. CONCLUSION: The trapeziectomy joint space supports both cellular and vascular ingrowth into human acellular dermal matrix.

Development and Characterization of A Novel Prox1-EGFP Lymphatic and Schlemm's Canal Reporter Rat.

The lymphatic system plays a key role in tissue fluid homeostasis, immune cell trafficking, and fat absorption. We previously reported a bacterial artificial chromosome (BAC)-based lymphatic reporter mouse, where EGFP is expressed under the regulation of the Prox1 promoter. This reporter line has been widely used to conveniently visualize lymphatic vessels and other Prox1-expressing tissues such as Schlemm's canal. However, mice have a number of experimental limitations due to small body size. By comparison, laboratory rats are larger in size and more closely model the metabolic, physiological, and surgical aspects of humans. Here, we report development of a novel lymphatic reporter rat using the mouse Prox1-EGFP BAC. Despite the species mismatch, the mouse Prox1-EGFP BAC enabled a reliable expression of EGFP in Prox1-expressing cells of the transgenic rats and allowed a convenient visualization of all lymphatic vessels, including those in the central nervous system, and Schlemm's canal. To demonstrate the utility of this new reporter rat, we studied the contractile properties and valvular functions of mesenteric lymphatics, developed a surgical model for vascularized lymph node transplantation, and confirmed Prox1 expression in venous valves. Together, Prox1-EGFP rat model will contribute to the advancement of lymphatic research as a valuable experimental resource.

Topical Fibronectin Improves Wound Healing of Irradiated Skin.

Wound healing is significantly delayed in irradiated skin. To better understand global changes in protein expression after radiation, we utilized a reverse phase protein array (RPPA) to identify significant changes in paired samples of normal and irradiated human skin. Of the 210 proteins studied, fibronectin was the most significantly and consistently downregulated in radiation-damaged skin. Using a murine model, we confirmed that radiation leads to decreased fibronectin expression in the skin as well as delayed wound healing. Topically applied fibronectin was found to significantly improve wound healing in irradiated skin and was associated with decreased inflammatory infiltrate and increased angiogenesis. Fibronectin treatment may be a useful adjunctive modality in the treatment of non-healing radiation wounds.