Placement of a drainage tube in the ileac lumen following laparoscopic appendectomy: A case report and literature review.

RATIONALE: Ileal perforation caused by the insertion of a drainage tube is a rare complication. Hence, the utilization of surgical drains in abdominal surgery remains controversial. At present, there is a trend to reduce the utilization of drains in abdominal surgery, although certain situations may necessitate their application. PATIENT CONCERNS: A 25-year-old Chinese woman presented with a history of right lower abdominal pain persisting for 10 days. Imaging examinations, including abdominal computed tomography and ultrasound, identified low-density lesions measuring 10 × 8 × 8cm3 in the right lower abdomen, which are consistent with perforated appendicitis complicated by a peri-appendiceal abscess. A laparoscopic appendectomy was carried out. On the 5th postoperative day, the drainage fluid changed to a grass-green color (80mL). Imaging with retrograde contrast through the drainage tube revealed that the 26 Fr silicon rubber drainage tube tip was positioned 50cm away from the ileocecal junction within the ileum. Both the ileal and ileocecal regions appeared well-developed. INTERVENTION AND OUTCOMES: Oral intake was suspended, and the patient received antacids, somatostatin, antibiotics, and total parenteral nutrition. On the 19th postoperative day, a follow-up imaging procedure using retrograde contrast through the drainage tube indicated that the tube tip was sealed. The treatment concluded on day 33 postoperatively, and the patient was discharged. DISCUSSION AND CONCLUSION: Ileal perforation due to an abdominal drainage tube following laparoscopic appendectomy constitutes a rare but serious complication. However, due to the adhesion and inflammatory changes around the abscess, laparoscopic dissection becomes a challenging and risky process, and the surgical skills and experiences are particularly important. Removing the abdominal drainage tube promptly based on the characteristics of the drainage fluid is recommended. The findings provide valuable insights for surgeons navigating similar challenges.

Rare retroperitoneal giant sacral schwannoma: A case report.

Schwannomas localized in the sacrum are relatively infrequent, accounting for 1-5% of all spinal axis schwannomas; they present with vague symptoms or are symptomless, so often grow to a considerable size before detection. Sacral schwannomas occasionally present with enormous dimensions, and these tumors are termed giant sacral schwannomas. However, their surgical removal is challenging owing to an abundant vascularity. The present study retrospectively analyzed the clinical and follow-up data of a patient with a giant sacral schwannoma. The patient experienced numbness in the left buttock and lower extremity, with radiating pain in the sole of the foot that had persisted for 3 years. A presacral mass was found by computed tomography examination 6 months after the stool had become thin. A tumor resection was performed using the anterior abdominal approach. A schwannoma was diagnosed by postoperative pathology. The postoperative course was uneventful, with the complete resolution of symptoms during the 21-month clinical follow-up. Overall, the present study reports the case of a giant sacral schwannoma with pelvic pain that was resected without complications and also discusses its successful management. Additionally, the study presents a systematic review of the literature. We consider that the surgical treatment of giant sacral schwannomas with piecemeal subtotal excision can achieve good outcomes, avoiding unnecessary neurological deficits.

Phenotype and function of smooth muscle cells derived from the human normal great saphenous vein in response to hypoxia.

OBJECTIVE: The contribution of hypoxia to the pathophysiology of vascular smooth muscle cells (VSMCs) has not yet been fully elucidated. This study evaluated the effect of hypoxia on the phenotype and function of SMCs derived from the human normal great saphenous veins (NGSVs). METHODS: Fifteen NGSV tissue samples were collected. SMCs were isolated and cultured. Proliferation, migration, adhesion, senescence, and the structure of cytoskeletal filaments in SMCs were observed. mRNA and protein expression of Bax, Bcl-2, caspase-3, matrix metalloproteinases (MMP)-2, MMP-9, tissue inhibitor of metalloproteinases (TIMP)-1, and TIMP-2 was detected by fluorescent quantitative polymerase chain reaction and immunoblotting in the cobalt chloride (CoCl2) and the control groups. RESULTS: A decrease in the number of cytoskeletal filaments was observed. mRNA and protein expression of Bas and caspase-3 was significantly decreased, while the quantity of proliferation, migration, adhesion, senescence, and mRNA and protein expression of Bcl-2, MMP-2, MMP-9, TIMP-1, and TIMP-2 in SMCs in the CoCl2 group were significantly increased compared with the control group. CONCLUSION: Under hypoxic conditions, the phenotype and function of SMCs derived from the human NGSVs were dysregulated, suggesting that VSMCs switch from the contractile phenotype to the secretory or synthetic phenotype, and more dedifferentiate, resulting in extracellular matrix deposition and apoptotic decrease through the intrinsic pathway.

Phenotypic and Functional Transformation in Smooth Muscle Cells Derived from a Superficial Thrombophlebitis-affected Vein Wall.

BACKGROUND: Superficial thrombophlebitis (ST) is a frequent pathology, but its exact incidence remains to be determined. This study tested the hypothesis whether relationships exist among smooth muscle cells (SMCs) derived from ST, varicose great saphenous veins (VGSVs), and normal great saphenous veins (GSVs). METHODS: Forty-one samples of ST, VGSVs, and GSVs were collected. SMCs were isolated and cultured. Proliferation, migration, adhesion, and senescence in SMCs from the three vein walls were compared by various methods. Bax, Bcl-2, caspase-3, matrix metalloproteinase-2 (MMP-2), MMP-9, tissue inhibitor of metalloproteinase-1 (TIMP-1), and TIMP-2 messenger RNA (mRNA) and protein expressions were detected by fluorescence quantitative PCR and Western blot. RESULTS: An obvious decrease in cytoskeletal filaments was observed in thrombophlebitic vascular smooth muscle cells (TVSMCs). The quantity of proliferation, migration, adhesion, and senescence in TVSMCs was significantly higher than in varicose vascular smooth muscle cells and normal vascular smooth muscle cells (NVSMCs) (all P < 0.05). Bax and caspase-3 mRNA and protein expression were decreased, while Bcl-2 mRNA and protein expression were increased in the TVSMCs compared with the varicose vascular smooth muscle cells and the NVSMCs (all P < 0.05). MMP-2, MMP-9, TIMP-1, and TIMP-2 mRNA and protein expression were significantly increased in the TVSMCs compared with the VVGSVs and the NVSMCs (all P < 0.05). CONCLUSION: SMCs derived from ST are more dedifferentiated and demonstrate increased cell proliferation, migration, adhesion, and senescence, as well as obviously decreased cytoskeletal filaments. These results suggest that the phenotypic and functional differences could be related to the presence of atrophic and hypertrophic vein segments during the disease course among SMCs derived from ST, VGSVs, and GSVs.

The expression of matrix metalloproteinases and their tissue inhibitors in the vein wall following superficial venous thrombosis.

OBJECTIVES: Superficial venous thrombosis (SVT) is the complications of varicose great saphenous veins (VGSVs), but its pathogenesis remains unclear. This study was designed to measure the changes in expression of matrix metalloproteinases (MMPs) and the tissue inhibitor of metalloproteinases (TIMPs) from SVT, VGSVs, and great saphenous veins (GSVs). METHODS: In the venous walls of the three groups, the expression of MMP-2, MMP-9, TIMP-1, and TIMP-2 proteins, protein-positive expression ratios, mRNA expression, and protein expression were determined by immunohistochemistry, polymerase chain reaction, and western blot. RESULTS: The MMP-2, MMP-9, TIMP-1, and TIMP-2 protein-positive expression ratios, mRNA and protein expression in the SVT group were significantly higher than those in the VGSV and the GSV groups. The corresponding expression in the VGSV group were significantly higher than those in the GSV group. CONCLUSION: Disequilibrium of MMPs and TIMPs in SVT wall occurs due to underlying high hydrostatic pressure and inflammation. These results suggested that MMPs and TIMPs participate in the process of venous wall remodeling.

Warshaw Technique in Laparoscopic Spleen-Preserving Distal Pancreatectomy: Surgical Strategy and Late Outcomes of Splenic Preservation.

Laparoscopic spleen-preserving distal pancreatectomy (LSPDP) can be accomplished with either the preservation or the resection of splenic vessels; the latter is also known as Warshaw technique. Our study is designed to investigate the operation selection strategy when proceeding LSPDP and to evaluate the long-term outcomes of patients undergoing Warshaw surgery. The medical records and follow-up data of patients who underwent LSPDP in Qilu Hospital, Shandong University, were reviewed retrospectively. A total of thirty-five patients were involved in this study, including 17 cases of patients who were treated with Warshaw procedure (WT) while the other 18 cases had splenic vessels preserved (SVP). Compared with the SVP group, the operative time and intraoperative blood loss in WT group were improved significantly. The incidence of early postoperative splenic infarction was higher in WT group. However, there was no report of splenic abscess or second operation. Follow-up data confirmed that there was no significant difference in spleen phagocytosis and immune function compared with normal healthy population. Our study confirms that LSPDP-Warshaw procedure is a safe and efficient treatment for the benign or low grade malignant tumors in distal pancreas in selected patients. The long-term spleen function is normal after Warshaw procedure. Preoperative assessment and intraoperative exploration are recommended for the selection of operation approaches.

Disequilibrium in MMPs and the tissue inhibitor of metalloproteinases in different segments of the varicose great saphenous vein wall.

BACKGROUND: Varicose great saphenous veins (VGSVs) are a common disorder with a high incidence, but the pathogenesis is unclear. This study was designed to measure the changes in matrix metalloproteinases (MMPs) and the tissue inhibitor of metalloproteinases (TIMPs) in different segments from VGSV walls to determine the relationship between MMPs, TIMPs expression, and expansion of the venous wall. METHODS: Twenty-one VGSV and 12 normal great saphenous vein (GSV) specimens were collected. Venous walls in the two groups, expression of MMP-2, MMP-9, TIMP-1, and TIMP-2 proteins, protein-positive expression ratios, mRNA expression, and protein content were determined by immunohistochemistry, PCR, and western blot. RESULTS: The MMP-2, MMP-9, TIMP-1, and TIMP-2 protein-positive expression ratios, mRNA expression in the upper, middle, and lower segments in the VGSV group were significantly higher than the corresponding regions in the GSV group, respectively. The MMP-2, MMP-9, TIMP-1, and TIMP-2 protein-positive expression ratios, mRNA expression, and protein concentrations in the lower segments in the VGSV group were also significantly higher than the upper and middle segments in the VGSV group and the corresponding regions in the GSV group, respectively. CONCLUSIONS: Under high hemodynamics, disequilibrium of MMPs and TIMPs from VGSVs exists within the upper, middle, and lower segments of VGSVs. These results suggested that MMPs and TIMPs participate in the process of venous wall remodeling and may be one of the mechanisms associated with the formation and development in varicose veins.

Phenotypic and functional transformation in smooth muscle cells derived from varicose veins.

OBJECTIVE: Varicose veins (VVs) are a common disorder of venous dilation and tortuosity, but the underlying mechanism is unclear. The functional integrity and phenotypic differences of VVs are also unclear. This study tested the hypothesis that phenotypic and functional differences exist between smooth muscle cells (SMCs) derived from VVs and normal veins. METHODS: SMCs were isolated from 28 samples of varicose great saphenous veins (VGSVs) and normal great saphenous (NGSVs) and cultured. Proliferation, migration, adhesion, and aging capacity in SMCs were compared in the two veins. Bas, Bcl-2, caspase-3, matrix metalloproteinase (MMP)-2 MMP-9, tissue inhibitor of metalloproteinases (TIMP)-1, and TIMP-2 messenger (m)RNA expression and protein content were detected by fluorescence quantitative polymerase chain reaction and immunoblotting. RESULTS: The microfilament structure of the framework was increased in SMCs in the VGSV group. Proliferation, migration, adhesion, and the aging cell count in SMCs in the VGSV group were significantly higher than the corresponding regions in the NGSV group (P < .05). Bas and caspase-3 mRNA expression and protein content were decreased, whereas Bcl-2 mRNA expression and protein content were increased in the VGSV group compared with the NGSV group (P < .05). MMP-2, MMP-9, TIMP-1, and TIMP-2 mRNA expression and protein content in the VGSV group were increased compared with the NGSV group (P < .05). CONCLUSIONS: SMCs derived from VGSVs are more dedifferentiated and demonstrate increased proliferative and synthetic capacity. These results suggest the presence of phenotypic and functional differences between SMCs derived from VGSVs and NGSVs. The phenotypic and functional abnormalities in SMCs may be associated with the pathogenesis in VGSVs.

[TIE's flying acupuncture for acute cerebral infarction hemiplegia: a randomized controlled trial].

OBJECTIVE: To compare the efficacy difference between TIE 's flying acupuncture combined with conventional treatment and conventional treatment alone on acute cerebral infarction hemiplegia. METHODS: A total of 120 patients were randomly divided into an observation group and a control group, 60 cases in each one. The control group was treated with conventional treatment, including anti-platelet aggregation, lipid-lowering, formula of traditional Chinese medicine which could promote circulation and remove stasis, neurotrophic medication and symptomatic treatment; mannitol was used for cerebral infarction with large area or increased intracranial pressure. Based on the conventional treatment applied in the control group, the observation group was treated with flying acupuncture at the affected Jianyu (LI 15), Quchi (LI 11), Shousanli (LI 10), Waiguan (TE 5), Hegu (LI 4), Huantiao (GB 30), Biguan (ST 31), Futu (ST 32), Zusanli (ST 36), etc. The treatment was given once a day, six days per week, for totally 2 weeks. The simplified Fugl-Meyer score, National Institute of Health Stroke Scale (NIHSS) and ADL-Bathel index (BI) score were evaluated before and after treatment in the two groups. RESULTS: After the treatment, the simplified Fugl-Meyer and BI were significantly increased in both groups (all P<0.05), which was significantly higher in the observation group (both P<0.05); after the treatment, the NIHSS was significantly lowered in both groups (both P<0.05), which was significantly lower in the observation group (P<0.05). CONCLUSION: TIE 's flying acupuncture combined with conventional treatment were effective for acute cerebral infarction hemiplegia, which have better efficacy than conventional treatment on improving motor function, neurological deficit and daily living ability, and the pain is mild.

Assessment of apoptotic cells in the wall of thrombophlebitic saphenous vein.

INTRODUCTION: Programmed cell death plays a critical role in various physiological processes. In the present study, we investigated its possible pathogenic role in primary varicose veins. We studied histological changes in surgical specimens from thrombophlebitic saphenous veins. In thrombophlebitic saphenous, varicose, and healthy veins, we also determined the number of apoptotic cells, and investigated apoptosis in the role of the pathogenesis of varicose veins. METHODS: Forty-four specimens of thrombophlebitic saphenous veins and simple varicose veins were collected. Thirteen samples of normal great saphenous veins were also collected (control group). Apoptosis of venous walls was determined by terminal deoxynucleotidyl transferase-mediated nick-end labeling (TUNEL) and immunofluorescence methods. The corpuscular number per high-power field was counted under light microscopy. RESULTS: A significantly higher apoptotic ratio of the intima and media were observed in control veins as compared with thrombophlebitic saphenous veins and simple varicose veins (p < 0.01). A significant difference was not observed between thrombophlebitic saphenous veins and simple varicose veins (p > 0.05). A significant difference was not seen between the intima and media of the three groups (p > 0.05). CONCLUSION: In the walls of thrombophlebitic saphenous veins and varicose veins, the apoptotic indices were clearly decreased. The results suggest that the process of programmed cell death was inhibited in walls of thrombophlebitic saphenous veins and varicose veins.

Long-term efficacy of subtotal splenectomy due to portal hypertension in cirrhotic patients.

BACKGROUND: Portal hypertension (PHT) requires invasive measures to prevent rupture and bleeding of esophagogastric varices; however, the long-term results of subtotal splenectomy plus fixation of the retrosternal omentum majus (SSFROM) have not been reported. Specifically, the advantages and disadvantages of surgery that preserves the spleen and the long-term hematologic effects have not been described. STUDY DESIGN: Our studies relating to SSFROM commenced in February 1999. As of April 2014 we have performed 256 subtotal splenectomies The records of 65 patients with PHT who underwent SSFROM were reviewed retrospectively. RESULTS: Four patients died within 4 years of surgery, with a 4-year survival rate of 94 %; the 11-year survival rate was 60 %. Eleven patients (17 %) had re-bleeding from esophagogastric varices. The white blood cell and platelet counts were higher 6 and 11 years post-operatively compared with pre-operative values (P < 0.01). Portal venous diameter, portal venous flow volume, splenic artery flow volume, as well as splenic length, thickness, and average cross-sectional areas were shown to be significantly constricted or decreased (P < 0.01). The proportion of serum CD3+ T cells, CD4+ T cells, and CD8+ T cells was increased (P < 0.01), while the serum levels of macrophage colony-stimulating factor and granulocyte-macrophage colony-stimulating factor were significantly decreased (P < 0.01). There was no significant change in the serum levels of IgA, IgM, IgG, and Tuftsin (P > 0.05). DSA demonstrated that 15 cases formed collateral circulations between the portal vein and superior vena cava. CONCLUSION: SSFROM provide long-term hemostasis for esophagogastric variceal bleeding in PHT and corrected hypersplenism. SSFROM is an effective treatment for patients with PHT in whom long-term survival is expected.

Penicillar arterioles of red pulp in residual spleen after subtotal splenectomy due to splenomegaly in cirrhotic patients: a comparative study.

BACKGROUND: Following splenomegaly due to portal hypertension, pathologic characteristics include passive congestion and lymphoplasia. High venous pressure and hemodynamics can result in vascular proliferation and lymphoplasia, and promote splenic microcirculation and functional changes. The aim of this study was to determine the changes in penicillar arterioles (PAs) of red pulp in residual splenic tissue after subtotal splenectomy due to splenomegaly in cirrhotic patients to provide anatomic and physiologic evidence for reserved splenic surgery. METHODS: Thirteen patients with splenomegaly due to portal hypertension, who were treated surgically, comprised the splenomegaly group. After 8 years, we obtained another specimen by puncture biopsy from the residual spleen group. We designated patients with splenic trauma as the control group. The morphology of PAs under light microscopy was facilitated by EVG staining and immunohistochemistry for CD34. Semi-thin sections were HE-stained. The ultrastructure of PA endothelial cells was observed under electron microscopy. RESULTS: In the residual spleen group, diffuse distribution, tenuous elastic intima in the arterial wall, and continuity in PA of red pulp were seen under light microscopy. A significantly lower density and average cross-sectional area of PAs were observed in the residual spleen group compared with the splenomegaly and control groups (P < 0.01). A uniform mitochondrial matrix and a decreased number of ruptured cristae in PA endothelial cells were observed under electron microscopy. While there were some beneficial changes (splenic artery flow volume, portal venous diameter, and portal venous flow volume), the platelet and leucocyte counts were markedly increased in residual spleen. CONCLUSION: Subtotal splenectomy can eliminate the factors which precipitate splenomegaly (portal hypertension), improve the reconstruction of splenic capillaries, correct hypersplenism, and restore normal splenic function.

Assessment of immune cells and function of the residual spleen after subtotal splenectomy due to splenomegaly in cirrhotic patients.

BACKGROUND: The spleen is thought to be central in regulating the immune system, a metabolic asset involved in endocrine function. Overwhelming postsplenectomy infection leads to a mortality rate of up to 50%. However, there is still controversy on performing subtotal splenectomy as treatment of splenomegaly due to portal hypertension in cirrhotic patients. In the present study, immunocytes and the indexes of splenic size, hemodynamics, hematology and immunology in the residual spleen were analyzed to support subtotal splenectomy due to splenomegaly. RESULTS: In residual spleen, T lymphocytes mainly were focal aggregation in the periarterial lymphatic sheath. While B lymphocytes densely distributed in splenic corpuscle. In red pulp, macrophages were equally distributed in the xsplenic cord and adhered to the wall of splenic sinus with high density. The number of unit area T and B lymphocytes of splenic corpuscle and marginal zone as well as macrophages of red pulp were obviously increased in the residual spleen, while the number of macrophages didn't be changed among the three groups in white pulp. While there were some beneficial changes (i.e., Counts of platelet and leucocyte as well as serum proportion of CD3+ T cells, CD4+ T cells, CD8+ T cells were increased markedly; serum levels of M-CSF and GM-CSF were decreased significantly; The proportion of granulocyte, erythrocyte, megakaryocyte in bone marrow were changed obviously; But serum IgA, IgM, IgG, Tuftsin level, there was no significant difference; splenic artery flow volume, portal venous diameter and portal venous flow volume, a significant difference was observed in residual spleen) in the clinical indices. CONCLUSION: After subtotal splenectomy with splenomegaly due to portal hypertension in cirrhotic patients, the number of unit area T and B lymphocytes, and MØ in red pulp of residual spleen increased significantly. However, whether increase of T, B lymphocytes and MØs in residual splenic tissue can enhance the immune function of the spleen, still need further research to confirm.

Subtotal splenectomy for splenomegaly in cirrhotic patients.

BACKGROUND: In recent years, the spleen has become to be recognized as the "control center" of the immune-metabolic-endocrine network. However, It is controversial that splenomegaly due to portal hypertension is treated by subtotal splenectomy. The aim of this study was to evaluate the distribution of fibrous tissue, morphology of cells as well as splenic size, hemodynamics, hematological and immunological indexes in the residual spleen after subtotal splenectomy. This information may help finding the basis for the operation of subtotal splenectomy. METHODS: Ten cases of splenomegaly due to portal hypertension were investigated. Two groups were created: Splenomegaly and Residual spleen. Control group was 10 cases of trauma-induced splenic rupture. Samples were sliced, and morphological changes were observed under light microscopy and electron microscopy. Indexes of splenic size, hemodynamics, hematology and immunology of the spleen were measured. RESULTS: Under light microscopy, the number of collagen fibers and elastic fibers was increased, and the number of reticular fibers was decreased in the residual spleen and splenomegaly groups. Under electron microscopy, the ultrastructure of endothelial cells, lymphocytes, macrophages, and reticular cells in the residual spleen group were noticeably improved more than in the splenomegaly group. Flow volume in the residual spleen and portal vein decreased obviously, with number of platelet rising to normal, and there was no significant difference in the indexes of immunology. CONCLUSION: After subtotal splenectomy, the residual spleen will not experience a high-pressure environment, and the fibrosis of splenic tissue and remodelling of corpuscular morphology will cease.

Mechanistic insights of sulfur mustard-induced acute tracheal injury in rats.

Sulfur mustard (SM) is believed to be a major threat to civilian populations because of the persistent asymmetric threat by nonstate actors, such as terrorist groups, the ease of synthesis and handling, and the risk of theft from stockpiles. The purpose of this study was to establish mechanisms of acute tracheal injury in rats induced by SM using histopathologic, immunohistochemical, and biochemical parameters. Male rats (Sprague-Dawley) were anesthetized, intratracheally intubated, and exposed to 2 mg/kg of SM. Animals were euthanized 6-, 24-, 48-, and 72-hour postexposure, and intracavitary blood samples from the heart and tracheal tissues were collected. Exposure of rats to SM resulted in rapid tracheal injury, including tracheal epithelial cell shedding, focal ulceration, and abundant lymphocyte invasion of the submucosa. There was also evidence of a large number of apoptotic cells in the epithelium and submucosa, the serum levels of tumor necrosis factor α, interleukin 1ß (IL) 1ß, IL-6, and γ-glutamyl transferase peaked at 24 hours, and the serum levels of lactate dehydrogenase, glutathione peroxidase, and thiobarbituric acid reactive substance peaked at 6 hours. The SM exposure also resulted in a loss of the cellular membrane, leakage of cytoplasm, fuzzy mitochondrial cristae, medullary changes in ciliated and goblet cells, and the nuclear chromatin appeared marginated in basal cells and fibroblasts. The results in the propylene glycol group were the same as the control group. These data demonstrated the histologic changes, inflammatory reactions, apoptosis, oxidative stress, and DNA damage following SM (2 mg/kg)-induced acute tracheal injury; the severity of changes was time dependent.

Assessment of the infiltration of inflammatory cells in the walls of thrombotic varicose veins.

The purpose of this study is to describe the infiltration of mast cells as well as T and B cells in the walls of thrombotic varicose great saphenous veins. Sections were obtained from venous segments of patients with varicose veins and stained with toluidine blue for mast cells, while immunohistochemistry for T cells (using CD45RO antibody) and B cells (CD20) was analyzed using light microscopy after staining. The number of mast cells, T, and B cells observed in thrombotic varicose veins was 1.925 ± 1.203, 72.038 ± 34.707, and 19.519 ± 9.899, respectively. In varicose veins, the corresponding values were 0.265 ± 0.099, 0.600 ± 0.432, and 0.488 ± 0.400. Significantly higher number of mast cells, T cells, and B cells were observed in thrombotic varicose veins compared with control veins. A significant difference was not observed between the varicose group and control group. Thrombi in varicose veins can induce infiltration of mast cells, T cells, and B cells, which may be involved in the remodeling of venous walls.