Parathyroid-induced angiogenesis is VEGF-dependent

Random Occurrence or Real Association? Primary Hyperparathyroidism in a Young Man With Sickle Cell Disease

A 32-year-old man with sickle cell disease (SCD) was admitted to the hospital for sickle cell crisis, during which laboratory workup revealed primary hyperparathyroidism. His treatment regimen included hydration, calcitonin, and calcimimetics. A parathyroid nuclear scan revealed anomalous parathyroid tissue. The precise relationship between primary hyperparathyroidism (PHPT) and SCD remains incompletely understood but may involve factors such as vitamin D deficiency, elevated erythropoietin levels, and the influence of growth factors on the development of parathyroid adenomas. Furthermore, the concurrent occurrence of both PHPT and SCD at an earlier age may potentiate adverse long-term outcomes. Effective management of PHPT in SCD entails addressing hypercalcemia and treating the underlying cause of hyperparathyroidism. While a potential association between PHPT and SCD exists, further research is essential to better elucidate their interaction, prevalence, clinical presentations, and outcomes.

Isolated Fragments of Intact Microvessels: Tissue Vascularization, Modeling, and Therapeutics

The microvasculature is integral to nearly every tissue in the body, providing not only perfusion to and from the tissue, but also homing sites for immune cells, cellular niches for tissue dynamics, and cooperative interactions with other tissue elements. As a microtissue itself, the microvasculature is a composite of multiple cell types exquisitely organized into structures (individual vessel segments and extensive vessel networks) capable of considerable dynamics and plasticity. Consequently, it has been challenging to include a functional microvasculature in assembled or fabricated tissues. Isolated fragments of intact microvessels, which retain the cellular composition and structures of native microvessels, are proving effective in a variety of vascularization applications including tissue in vitro disease modeling, vascular biology, mechanistic discovery, and tissue prevascularization in regenerative therapeutics and grafting. In this review, we will discuss the importance of recapitulating native tissue biology and the successful vascularization applications of isolated microvessels.

Investigating the optimal parathyroid autotransplantation strategy in transareolar endoscopic thyroidectomy: A retrospective cohort study

BACKGROUND

There is ongoing debate about whether intraoperative parathyroid autotransplantation effectively prevents permanent hypoparathyroidism after thyroidectomy. This study aims to examine its impact on postoperative parathyroid function and determine the best autotransplantation strategy.

METHODS

A retrospective analysis was conducted on 194 patients who underwent total thyroidectomy with central lymph node dissection (CLND) for papillary thyroid carcinoma (PTC). Patients were divided into four groups based on the number of parathyroid autotransplants during surgery: Group 1 (none, n = 43), Group 2 (1 transplant, n = 60), Group 3 (2 transplants, n = 67), and Group 4 (3 transplants, n = 24). Various clinical parameters were collected and compared among the groups.

RESULTS

Parathyroid autotransplantation was identified as a risk factor for temporary hypoparathyroidism (OR: 1.74; 95% CI: 1.27-2.39, P = 0.001) and a protective factor for permanent hypoparathyroidism (OR: 0.27; 95% CI: 0.14-0.55, P < 0.001). At 12 months postoperative, systemic parathyroid hormone (PTH) levels increased progressively from Groups 1 to 4, with significant differences observed only between Group 1 and Group 2 (P < 0.02). Difference values in systemic PTH levels between Month 1 and Day 1 postoperative increased progressively from Groups 1 to 4, with statistically significant differences observed between adjacent groups (P < 0.02). The number of dissected positive lymph nodes increased progressively across the four groups, showing statistical differences (P < 0.02).

CONCLUSION

Parathyroid autotransplantation can prevent permanent hypoparathyroidism. Additionally, we recommend preserving parathyroids in situ whenever possible. If autotransplantation is required, it should involve no more than two glands.

Preservation of parathyroid glands during thyroid and neck surgery

The parathyroid glands are situated in close proximity to the thyroid gland. They have an important endocrine function maintaining calcium and phosphate homeostasis in the body by the secretion of parathormone (PTH), which is responsible for this function. The parathyroid glands are commonly damaged during thyroid surgeries. This could lead to transient or permanent hypoparathyroidism in 30% of cases. Preservation of the parathyroid glands, is an important and integral part of thyroidectomy and other surgical interventions in the neck. The main principle underlying this is a thorough understanding of parathyroid anatomy in relation to the thyroid gland and other important structures in the area. There can also be significant variation in the anatomical location of the glands. Various techniques and methods have been described for parathyroid preservation. They include intraoperative identification utilizing indocyanine green (ICG) fluorescence, carbon nanoparticles, loupes, and microscopes. The techniques of surgery (meticulous capsular dissection), expertise, central compartment neck dissection, preoperative vitamin D deficiency, extent and type of thyroidectomy are the risk factors associated with damaged thyroids, inadvertent parathyroidectomy and subsequent hypoparathyroidism. Parathyroid Autotransplantation is a treatment option for inadvertent parathyroidectomy. Ultimately, the best way to assure normal parathyroid function is to preserve them in situ intraoperatively undamaged.

Long-Term Outcomes of Parathyroid Autografts in Primary Hyperparathyroidism

Context

Autologous implantation of parathyroid tissue is frequently utilized after parathyroidectomy in patients with heritable forms of primary hyperparathyroidism (PHPT). Data on long-term functional outcome of these grafts is sparse.

Objective

To investigate long-term outcomes of parathyroid autografts.

Methods

Retrospective study of patients with PHPT who underwent parathyroid autografts from 1991 to 2020.

Results

We identified 115 patients with PHPT who underwent 135 parathyroid autografts. Median follow-up duration since graft was 10 (4-20) years. Of the 111 grafts with known functional outcome, 54 (49%) were fully functional, 13 (12%) partially functional, and 44 (40%) nonfunctional at last follow-up. Age at time of graft, thymectomy prior to autograft, graft type (delayed vs immediate), or duration of cryopreservation did not predict functional outcome. There were 45 (83%) post-graft PHPT recurrences among 54 fully functional grafts at a median duration of 8 (4-15) years after grafting. Surgery was performed in 42/45 recurrences, but cure was attained in 18/42 (43%) only. Twelve of 18 (67%) recurrences were graft-related while remaining 6 (33%) had a neck or mediastinal source. Median time to recurrence was 16 (11-25) years in neck or mediastinal source vs 7 (2-13) years in graft-related recurrences. Median parathyroid hormone (PTH) gradient was significantly higher at 23 (20-27) in graft-related recurrence vs 1.3 (1.2-2.5) in neck or mediastinal source (P = .03).

Conclusions

Post-graft recurrence of PHPT occurs frequently within the first decade after graft and is challenging to localize. Time to recurrence after graft is significantly shorter and PTH gradient higher for graft-related recurrence. Clinical Trial Number: NCT04969926.

Vascularized Tissue Organoids

Tissue organoids hold enormous potential as tools for a variety of applications, including disease modeling and drug screening. To effectively mimic the native tissue environment, it is critical to integrate a microvasculature with the parenchyma and stroma. In addition to providing a means to physiologically perfuse the organoids, the microvasculature also contributes to the cellular dynamics of the tissue model via the cells of the perivascular niche, thereby further modulating tissue function. In this review, we discuss current and developing strategies for vascularizing organoids, consider tissue-specific vascularization approaches, discuss the importance of perfusion, and provide perspectives on the state of the field.

The Evaluation of Neovessel Angiogenesis Behavior at Tissue Interfaces

Angiogenesis, the formation of new vessel elements from existing vessels, is important in homeostasis and tissue repair. Dysfunctional angiogenesis can contribute to numerous pathologies, including cancer, ischemia, and chronic wounds. In many instances, growing vessels must navigate along or across tissue-associated boundaries and interfaces tissue interfaces. To understand this dynamic, we developed a new model for studying angiogenesis at tissue interfaces utilizing intact microvessel fragments isolated from adipose tissue. Isolated microvessels retain their native structural and cellular complexity. When embedded in a 3D matrix, microvessels, sprout, grow, and connect to form a neovasculature. Here, we discuss and describe methodology for one application of our microvessel-based angiogenesis model, studying neovessel behavior at tissue interfaces.

Parathyroid Tumor Microenvironment

Parathyroid tumors are the second most common endocrine neoplasia, and it is almost always associated with hypersecretion of the parathormone (PTH), involved in calcium homeostasis, causing primary hyperparathyroidism (PHPT). Parathyroid neoplasia has a stromal component particularly represented in atypical adenomatous and carcinomatous lesions. Recently, data about the features and the function of the parathyroid tumor microenvironment (TME) have been accumulated. Parathyroid TME includes heterogeneous cells: endothelial cells, myofibroblasts, lymphocytes and macrophages, and mesenchymal stem cells have been identified, each of them presenting a phenotype consistent with tumor-associated cells. Parathyroid tumors overexpress proangiogenic molecules including vascular endothelial growth factor (VEGF-A), fibroblast growth factor-2 (FGF-2), and angiopoietins that promote both recruitment and proliferation of endothelial cell precursors, thus resulting in a microvessel density higher than that detected in normal parathyroid glands. Moreover, parathyroid tumor endocrine cells operate multifaceted interactions with stromal cells, partly mediated by the CXCL12/CXCR4 pathway, while, at present, the immune landscape of parathyroid tumors has just begun to be investigated. Studies about TME in parathyroid adenomas provide an example of the role of TME in benign tumors, whose molecular mechanisms and functions comprehension are limited.

Short and long-term impact of parathyroid autotransplantation on parathyroid function after total thyroidectomy

The most common complication of total thyroidectomy is parathyroid insufficiency. Acute, transient, post-operative hypoparathyroidism increases length of hospitalization, morbidity and cost associated with total thyroidectomy. While permanent hypoparathyroidism poses a significant medical burden with lifetime medication, regular follow up and considerable disease burden related to chronic renal failure and other sequelae. Parathyroid autotransplantation has been demonstrated to result in biochemically functional grafts, leading to the procedures' common use during total thyroidectomy. The clearest indications for parathyroid auto transplantation are inadvertently removed or devascularized parathyroid glands. Some centers utilize routine autotransplantation to reduce the risk of permanent hypoparathyroidism. Novel fluorescence techniques to aid in parathyroid detection during thyroid surgery are under evaluation. This review aims to define the role and impact of parathyroid autotransplantation undertaken during total thyroidectomy.

Oxidative stress and angiogenesis in primary hyperparathyroidism

Background

The inappropriate elevation of parathormone (PTH), which regulates the process of angiogenesis in parathyroid tissue, causes the changes of activity of enzymes responsible for the removal of free radicals. Parathyroidectomy (PTX) in patients with primary hyperparathyroidism (PHPT) lowers the level of PTH and leads to the reduction of risk of cardiovascular and all-cause mortality by normalization of the antioxidant status. Therefore, the aims of the study were to assess the activity of antioxidant enzymes and free radical reaction products in patients after parathyroidectomy, and to evaluate the correlation between the systemic oxidative stress and angiogenic parameters.

Materials and methods

Patients with PHPT treated surgically were enrolled into the study. Total antioxidant capacity (TAC), total oxidative status (TOS), oxidative stress index (OSI), superoxide dismutase (SOD), ceruloplasmin (CER), lipid hydroperoxides (LHP) and malondialdehyde (MDA) were measured before and after parathyroidectomy. The immunohistological expression of angiogenic factors in parathyroid specimens was assessed by the BrightVision method from ImmunoLogic using murine monoclonal anti-human: anti-VEGF, anti-CD31 and anti-CD106 antibodies.

Results

The significant increase of TAC, CER, reduction of TOS, MDA, SOD, especially for cytoplasmic form, and significant decrease of OSI, LHP were observed after PTX. There was no significant correlation between changes of oxidative stress markers and angiogenic parameters: VEGF, CD-31, CD-106 in parathyroid tissue. The correlation level was low and medium.

Conclusions

Parathyroidectomy causes down-regulation of lipid peroxidation processes and leads to reduction of oxidative stress in patients with PHPT. The decrease in the OSI is the results of down-regulation of oxidative stress in the postoperative period. The change of the antioxidant status has no impact on angiogenesis processes in parathyroid tissue.

Parathyroid Reimplantation in Forearm Subcutaneous Tissue During Thyroidectomy: A Simple and Effective Way to Avoid Hypoparathyroidism

INTRODUCTION

Parathyroid autotransplantation plays an important role in preventing hypoparathyroidism following thyroidectomy. The preferred reimplantation site is still the sternocleidomastoid muscle, but this approach does not permit to check graft vitality postoperatively. The authors report the first prospective evaluation of normal parathyroid gland reimplantation in forearm subcutaneous tissue (using the same technique proposed during parathyroidectomy for hyperplasia) in case of devascularized or inadvertently removed glands during thyroid surgery.

MATERIALS AND METHODS

From January 2013 to August 2014, we performed 348 consecutive thyroidectomies for various disease, both benign and malignant. In 25 cases, due to inadvertent parathyroid removal or evidence of insufficient blood supply, we removed and fragmented the gland into 0.5-1 mm slices (one for frozen section) and reimplanted it into two subcutaneous pockets on the non-dominant forearm. After surgery we checked grafted gland function by evaluation of serum parathormone gradient between reimplanted versus non-reimplanted arm (considering significant a ratio of 1.5 or more), at 1 week, 1 and 3 months after surgery.

RESULTS

We observed recovery of reimplanted graft function in 48, 88 and 96% of patients respectively at 1 week, 1 and 3 months after surgery. All patients showed normal parathormone levels in peripheral blood (non-reimplanted arm). In one case we observed post-operative wound hematoma on graft-site. This patient showed no graft functionality in post-operative period (even at 3 months follow-up).

CONCLUSIONS

Parathyroid gland reimplantation in forearm subcutaneous tissue during thyroid surgery is a safe, easy and effective procedure; furthermore, it allows a good control of graft functionality and would allow an easy grafted gland removal if needed.

Tumour-associated fibroblasts contribute to neoangiogenesis in human parathyroid neoplasia

Components of the tumour microenvironment initiate and promote cancer development. In this study, we investigated the stromal component of parathyroid neoplasia. Immunohistochemistry for alpha-smooth muscle actin (α-SMA) showed an abundant periacinar distribution of α-SMA(+) cells in normal parathyroid glands (n=3). This pattern was progressively lost in parathyroid adenomas (PAds; n=6) where α-SMA(+)cells were found to surround new microvessels, as observed in foetal parathyroid glands (n=2). Moreover, in atypical adenomas (n=5) and carcinomas (n=4), α-SMA(+) cells disappeared from the parenchyma and accumulated in the capsula and fibrous bands. At variance with normal glands, parathyroid tumours (n=37) expressed high levels of fibroblast-activation protein (FAP) transcripts, a marker of tumour-associated fibroblasts. We analysed the ability of PAd-derived cells to activate fibroblasts using human bone-marrow mesenchymal stem cells (hBM-MSCs). PAd-derived cells induced a significant increase in FAP and vascular endothelial growth factor A (VEGFA) mRNA levels in co-cultured hBM-MSCs. Furthermore, the role of the calcium-sensing receptor (CASR) and of the CXCL12/CXCR4 pathway in the PAd-induced activation of hBM-MSCs was investigated. Treatment of co-cultures of hBM-MSCs and PAd-derived cells with the CXCR4 inhibitor AMD3100 reduced the stimulated VEGFA levels, while CASR activation by the R568 agonist was ineffective. PAd-derived cells co-expressing parathyroid hormone (PTH)/CXCR4 and PTH/CXCL12 were identified by FACS, suggesting a paracrine/autocrine signalling. Finally, CXCR4 blockade by AMD3100 reduced PTH gene expression levels in PAd-derived cells. In conclusion, i) PAd-derived cells activated cells of mesenchymal origin; ii) PAd-associated fibroblasts were involved in tumuor neoangiogenesis and iii) CXCL12/CXCR4 pathway was expressed and active in PAd cells, likely contributing to parathyroid tumour neoangiogenesis and PTH synthesis modulation.

Parathyroid hormone 1-84 alters circulating vascular endothelial growth factor levels in hypoparathyroidism

CONTEXT

We previously reported on four patients treated with PTH(1-84) who recovered from postoperative hypoparathyroidism many years after onset. Because vascular endothelial growth factor (VEGF) has been shown to be necessary for the induction of PTH-mediated angiogenesis, we postulated a possible role for VEGF in the recovery of parathyroid function in these subjects.

OBJECTIVE

Our objective was to measure VEGF levels in subjects with hypoparathyroidism who regained parathyroid gland function and matched controls.

SETTING AND DESIGN

Subjects with hypoparathyroidism who regained parathyroid gland function were each matched to two hypoparathyroid controls by postoperative etiology, age (within 5 y), menopausal status, and duration of hypoparathyroidism. We measured serum VEGF levels at baseline and through 48 months of PTH(1-84) therapy.

RESULTS

VEGF levels increased after the initiation of PTH(1-84) therapy for the entire cohort, from 309.7 ± 162 pg/ml at baseline to 380.2 ± 178 pg/ml at 12 months (P = .03). Levels trended downward thereafter. There were no significant differences in VEGF levels between the subjects with recovery of parathyroid function and the matched controls.

CONCLUSIONS

PTH(1-84) alters serum VEGF levels in subjects with hypoparathyroidism. Additional investigation is necessary to understand the mechanisms by which some subjects with postoperative hypoparathyroidism recover parathyroid gland function.

The surgical management of thyroid cancer

Thyroid cancer has been increasing in incidence, with the number of reported cases in the US rising by 25% over the last 3 years. With growing technological advances in the field and improved contributions of diagnostics, surgical decision-making and operative planning have taken on new challenges. Herein, we review the current clinical practice recommendations and active areas of surgical controversy, reflective of the most recently published professional consensus guidelines and a systematic review of the literature.

Recovery of parathyroid hormone secretion and function in postoperative hypoparathyroidism: a case series

CONTEXT

Transient and permanent postoperative hypoparathyroidism are recognized complications of neck surgery. Postoperative hypoparathyroidism is usually considered permanent when it persists for 6 months; in rare cases, recovery of hypoparathyroidism through 1 year has been described. Recovery of hypoparathyroidism years after diagnosis has not previously been reported.

OBJECTIVE

We report four patients being treated with PTH(1-84) in a research protocol who recovered from postoperative hypoparathyroidism many years after onset.

METHODS

Recovery from hypoparathyroidism was established by: 1) serum calcium and PTH levels within the normal range off PTH(1-84) treatment for at least 1 week; 2) requirement for daily calcium supplementation reduced to ≤1 g; and 3) no supplemental active vitamin D therapy.

RESULTS

Hypoparathyroidism developed in three subjects after repeated neck surgery for primary hyperparathyroidism and in one subject after total thyroidectomy for Graves' disease. Parathyroid tissue autotransplant was performed in two of the four subjects. Two had undetectable PTH levels at study entry, whereas the other two subjects had detectable, although low, PTH levels. Hypoparathyroidism had been present for at least 8 years, and in one case for 16 years. The recovery of parathyroid function followed treatment with PTH(1-84) for 36 to 63 months.

CONCLUSIONS

Although it remains relatively rare, this report documents recovery of long-term postoperative hypoparathyroidism many years after the initial diagnosis. A potential role for exogenous PTH is intriguing with several plausible mechanisms.

Localized delivery of growth factors for angiogenesis and bone formation in tissue engineering

Angiogenesis is a key component of bone formation. Delivery of growth factors for both angiogenesis and osteogenesis is about to gain important potential as a future therapeutic tool. This review focuses on these growth factors that have dual functions in angiogenesis and osteogenesis, and their localized application. A major hurdle in the clinical development of growth factor therapy so far is how to assure safe and efficacious therapeutic use of such factors and avoid unwanted side effects and toxicity. It is now firmly established from the available information that the type, dose, combinations and delivery kinetics of growth factors all play a decisive role for the success of growth factor therapy. All of these parameters have to be adapted and optimized for each animal model or clinical case. In this review we discuss some important parameters associated with growth factor therapy and present an overview of selected preclinical studies, followed by a conceptual description of both established and proposed delivery strategies meeting therapeutic needs.

Parathyroid autotransplantation in extensive head and neck resections: case series report

Permanent or temporary hypoparathyroidism may be a debilitating result of radical cervical surgery, as noted most commonly following thyroid or parathyroid surgery. However, it can also be the outcome of any surgical procedure involving bilateral extensive manipulation of the anterior neck triangle, especially in order to ensure oncologically adequate surgical margins.

We report our experience of three patients that underwent parathyroid immediate autotransplanation following extensive surgical manipulations of the neck region for oncological reasons. PTH levels were restored to normal by the fourth postoperative week, allowing us to wean the patients off calcium and vitamin D₃ supplementation, which was attributed to full autograft function. Parathyroid autotransplantation, immediate or delayed, is a simple and safe technique which should be considered by the surgeon whenever there is a high risk for postoperative hypoparathyroidism following radical operations of the neck for oncological reasons.

Haemangioma of the parathyroid gland. Does it really exist?

We are reporting a case of a capillary haemangioma-like proliferation arising within a parathyroid gland adenoma, associated with primary hyperparathyroidism. The vessel proliferation bearing a close resemblance to a capillary haemangioma consisted of tightly packed capillaries, endothelial buds and occasional small caliber muscle-containing vessels. The observation expands the spectrum of tumour-associated vascular proliferations by adding an exuberant haemangioma-like pattern to its extreme end. These are a heterogeneous group of lesions reportedly induced by aberrant production of angiogenic factors. We investigated expression of VEGF, pKDR, FGF2, HIF1alpha and HIF2alpha and only VEGF gave a strong positive reaction in the adenoma cells entrapped in the vascular meshwork. Although this does not constitute a proof that aberrant VEGF production was a causative agent, unexpected supportive evidence for its pathogenic role emerged from a failure to detect chromogranin A. Chromogranin A is a precursor of several regulatory proteins, including vasostatin I, a multilevel suppressor of VEGF. The production of vasostatin I may have been reduced in a chromogranin A-negative adenoma which could lead to a loss of its opposing effect on VEGF-regulated processes. The only two other published cases of haemangioma of the parathyroid gland were reported in patients diagnosed with primary parathyroid hyperplasia with hyperparathyroidism, a pathophysiologic condition similar to our case. Therefore we raise the question whether these tumours could also represent a reactive phenomenon.

Vascular endothelial growth factor expression in ovarian cancer: a model for targeted use of novel therapies?

PURPOSE

Angiogenesis has a vital role in tumor growth and metastasis, and vascular endothelial growth factor (VEGF) represents a potent cytokine in this process. However, the influence of VEGF in ovarian cancer remains controversial. Interest has focused on the use of antiangiogenic drugs in ovarian cancer. This study aims to establish the pattern of expression and effect on prognosis of VEGF in a large population of ovarian cancer patients and to potentially identify a cohort in whom antiangiogenic therapy is appropriate.

EXPERIMENTAL DESIGN

Using a tissue microarray of 339 primary ovarian cancers, the expression of VEGF was assessed immunohistochemically. Coupled to a comprehensive database of clinicopathologic variables, its effect on these factors and survival was studied.

RESULTS

Tumors expressing high levels of VEGF had significantly poorer survival (P = 0.04). Factors shown to predict prognosis independently of each other were age, International Federation of Gynecologists and Obstetricians stage, and the absence of macroscopic disease after surgery. VEGF was independently predictive of prognosis on multivariate analysis (P = 0.02). There was no correlation between VEGF and any clinicopathologic variable. High expression of VEGF was seen in only 7% of the tumors, suggesting that the role of antiangiogenic drugs may be limited to a small subset of patients.

CONCLUSION

High VEGF expression occurs in a small proportion of ovarian cancers, and this independently predicts poor prognosis. The small percentage of tumors with high levels of VEGF activity suggests that the role of bevacizumab may potentially be limited to a few patients; these patients could be targeted by molecular profiling.

Evaluation of parathyroid gland angiogenesis in chronic kidney disease associated with secondary hyperparathyroidism

BACKGROUND

Secondary hyperparathyroidism (SHPT) is a common complication of chronic kidney disease. Increased parathyroid hormone (PTH) synthesis and secretion is associated with parathyroid cell hyperplasia. The exact mechanisms involved in parathyroid gland (PTG) hyperplasia are still poorly understood. There is no available data on angiogenesis in PTG of patients with chronic kidney disease and SHPT. The aim of this study is to evaluate angiogenesis and expression of the angiogenic factors, basic fibroblastic growth factor (b-FGF) and vascular endothelial growth factor A (VEGF), in secondary PTG hyperplasia.

METHODS

This study was performed on formalin-fixed paraffin-embedded archival tissues of 21 SHPT glands from haemodialysis (n = 19) and kidney transplanted (n = 2) patients submitted to surgical parathyroidectomy. For control, eight normal human parathyroid glands (NPG) encountered in surgical specimens of total thyroidectomy were used. We evaluated the immunohistochemical expression of the proliferation cell marker Ki67. Angiogenesis was evaluated by immunohistochemistry staining with anti-endoglin (CD105) antibody in 21 SPH and 5 NPG by stereological analysis. Levels of b-FGF and VEGF were determined by semi-quantitative analysis in 21 SPH and 8 NPG.

RESULTS

The SHPT patients present a mean iPTH of 1314 +/- 750 pg/ml, a corrected serum calcium of 10.3 +/- 1.2 mg/dl and a serum phosphorus of 6.1 +/- 1.4 mg/dl. SHPT glands displayed a significantly higher immunoreactivity against Ki67, compared to NPG. With CD105, a significantly higher number and volume of microvessels were observed in SHPT compared to NPG. Both VEGF and b-FGF expression were increased in SHPT compared to NPG. Using the predefined subdivision into negative and positive only the b-FGF expression was significantly increased in the SHPT glands compared to NPG.

CONCLUSION

These results suggest that PTGs in this group of patients with SHPT have a significantly higher number of vessels expressing CD105, which has been reported to preferentially label activated endothelial cells associated with angiogenesis. SHPT glands have a significantly increased expression of b-FGF compared to NPG. VEGF-A expression is also increased in the examined SHPT glands but could be less relevant for angiogenesis.

Angiogenesis inhibitor attenuates parathyroid hormone-induced anabolic effect

In vivo osteogenic responses to anabolic stimuli are expected to be accompanied by angiogenesis as well as in the process of remodeling of bone. Consequently, angiogenesis might play an important role in mediating bone forming stimulating effect of parathyroid hormone (PTH). To investigate this relationship, we used actively growing young Sprague-Dawley rats and CKD-732, one of the angiogenesis inhibitor (AI) to reveal the relationship of angiogenesis in the effect of PTH. The groups were divided as (1) vehicle [VEH group], (2) PTH(1-84) [PTH group], (3) AI alone [AI group], (4) PTH(1-84)+AI concomitance [PTH-AI group] and were treated for 6 weeks. The bone mineral density (BMD) of PTH group was higher than VEH group and the gain of bone mass was attenuated in PTH-AI group. The maximal failure load in PTH group was higher than VEH group, but it was definitely attenuated by concurrent use of AI. Moreover, the toughness showed similar significant deterioration in PTH-AI group. General bone turnover was also significantly decreased in PTH-AI group as shown by the absence of increase in osteocalcin and beta-crosslaps and by decrease in metaphyseal length. The BMD or the biomechanic data of AI only group were similar to the VEH group, suggesting the minimal effect of AI itself on the normal modeling phase of the growing rats. In conclusion, the angiogenesis seemed to contribute to completing the anabolic effect of PTH especially for bone strength.

Vascular Endothelial Growth Factor Mediates Hypoxic Stimulated Embryonic Bladder Growth in Organ Culture

PURPOSE

Tissue hypoxia enhances embryonic angiogenesis at least in part by up-regulating vascular endothelial growth factor. Additionally, exogenous vascular endothelial growth factor-A enhances embryonic bladder explant growth. We hypothesized that developing bladders are hypoxic in vivo and oxygen tensions modulate explanted bladder growth by altering vascular endothelial growth factor-A expression.

MATERIALS AND METHODS

Embryonic day 14 mouse bladders were cultured in 20% O(2) or 3% O(2) atmospheres. Some cultures were supplemented with a vascular endothelial growth factor receptor 1/Fc chimera to block vascular endothelial growth factor bioactivity. After 6 days explant areas, DNA, protein, total cell numbers, and proportions expressing endothelial and smooth muscle markers were measured. Pimonidazole was administered to pregnant mice and hypoxia was sought in embryonic tissues by immunohistochemistry.

RESULTS

In vivo pimonidazole adducts and vascular endothelial growth factor-A immunolocalized to embryonic urothelium and bladders up-regulated total vascular endothelial growth factor-A between embryonic days 14 and 18. All growth parameters and vascular endothelial growth factor-A protein levels were enhanced in hypoxic vs normoxic culture. Addition of vascular endothelial growth factor receptor 1/Fc prevented this accelerated growth.

CONCLUSIONS

In vivo embryonic bladders are hypoxic and express vascular endothelial growth factor-A. In vitro, when oxygen tensions are manipulated, vascular endothelial growth factor-A protein positively correlates with the growth of whole explants as well as endothelium. Normal embryonic bladder development may be driven at least in part by hypoxic up-regulation of vascular endothelial growth factor-A.

The Impact of Single Parathyroid Gland Autotransplantation During Thyroid Surgery on Postoperative Hypoparathyroidism: A Multicenter Study

BACKGROUND

We compared the surgical outcomes in patients undergoing bilateral thyroid surgery with or without parathyroid gland autotransplantation (PTAT).

METHODS

One thousand three hundred nine patients underwent surgery for treatment of various thyroid diseases at three Academic Departments of General Surgery and one Endocrine-Surgical Unit throughout Italy. A nonviable gland or difficulties in dissection of the parathyroid glands were encountered in 160 (13.7%) patients. The subjects were divided into two groups: (1) patients undergoing PTAT during thyroidectomy (n = 79) versus (2) control group (n = 81), patients not undergoing PTAT.

RESULTS

Clinical manifestations occurred in 5.0% of PTAT patients and in 13.6% of control patients (P = NS). Total postoperative hypocalcemia was less among PTAT than control patients (17.7% and 48.1%, respectively; P = .0001). There was no significant difference between the two groups in terms of definitive hypocalcemia (0% vs 2.5% in PTAT and control, respectively). Transient postoperative hypocalcemia was less among PTAT than controls (17.7% vs 45.7%; P = .0002). PTAT was associated with decreased occurrence of hypocalcemia in the two subgroups of patients operated for benign euthyroid disease (P < .0001), as compared with the control group.

CONCLUSIONS

PTAT is an effective procedure to reduce the incidence of permanent hypoparathyroidism. Transient hypoparathyroidism appears to not be influenced by PTAT. Moreover, we observed that damage to one parathyroid gland has more side effects (ie, transient hypocalcemia) among patients who were preoperatively at low rather than at high risk of postoperative hypocalcemia.

Vascular endothelial growth factor stimulates embryonic urinary bladder development in organ culture

OBJECTIVES

To determine whether vascular endothelial growth factor A (VEGF) and its receptors are expressed during bladder development in mice when capillaries are forming, and whether exogenous VEGF might enhance the growth of endothelia and other types of bladder cells, using an embryonic organ-culture model.

MATERIALS AND METHODS

Whole bladders from wild-type mice, at embryonic day (E) 14, were grown in serum-free organ culture in an air/5% CO2 atmosphere; some cultures were supplemented with VEGF and/or with VEGF receptor 1/Fc chimera (VEGFR1/Fc), which blocks VEGF bioactivity. Organs were harvested after 6 days and the expression of VEGF and related molecules assessed using immunohistochemistry.

RESULTS

VEGF, VEGFR1 and VEGFR2 positive cells were immunodetected in E14 and E18 bladders. Exogenous VEGF increased whole-organ growth, as assessed by explant areas, total cell numbers, DNA and protein content; proliferation was enhanced, and apoptosis decreased, in urothelium and surrounding tissues. VEGF also increased the proportions of cells expressing endothelial (CD31) and smooth muscle (alpha smooth muscle actin) markers. VEGFR1/Fc blocked the growth-enhancing effects of exogenous VEGF.

CONCLUSIONS

In organ culture, exogenous VEGF not only stimulated embryonic bladder endothelial cells but also strikingly enhanced the growth of the whole organ. Whether the effects of VEGF on diverse bladder cell populations are direct or indirect requires further investigation. The finding that VEGF protein is present in embryonic bladders in vivo raises the possibility that it has similar actions during normal development. The results also illuminate the pathobiology of certain bladder diseases in which VEGF levels have been shown to be increased.

The non-proteolytically active thrombin peptide TP508 stimulates angiogenic sprouting

Thrombin is a serine protease that promotes platelet aggregation, blood coagulation, and tissue repair. A peptide derived from a non-proteolytically active region of thrombin, TP508, also promotes tissue repair and increased vascularity, yet does not activate platelet and inflammatory cascades. TP508 binds to cells with high affinity and stimulates cells independent of the proteolytically active thrombin receptors (PARs) and thus is considered to activate a non-proteolytically active receptor (non-PAR) pathway. Using a model of angiogenic sprouting, we further defined the angiogenic potential of TP508 and investigated the role of non-proteolytic, thrombin-mediated pathways in angiogenesis. The assay involves measuring angiogenic sprouting from cultured, intact microvessel fragments. In this assay, TP508 stimulated angiogenic sprouting to an extent similar to or greater than the potent angiogenic factor, VEGF. However, TP508 had no significant effect on the number of sprouts that formed per vessel. In contrast to TP508, proteolytically active receptor agonists had no effect or inhibited angiogenic sprouting. The increased sprouting activity stimulated by TP508 was VEGF dependent but did not involve an increase in VEGF mRNA expression above baseline levels. These results suggest that TP508 acts early in angiogenesis and directly on microvascular cells to accelerate sprouting, but not to induce more sprouting, in a manner different than the intact thrombin molecule.

A new animal model to assess angiogenesis and endocrine function of parathyroid heterografts in vivo

BACKGROUND

It is still a matter of investigation how angiogenesis and restoration of gland perfusion determine graft function after free parathyroid autotransplantation. We provide a new animal model allowing simultaneous and repetitive in vivo assessment of angiogenesis and endocrine function of parathyroid transplants.

METHODS

Fresh human parathyroid tissue from patients with secondary hyperparathyroidism was grafted into dorsal skinfold chamber preparations of athymic nude mice (CD1-nu; n=8). Equivalent pieces of the same human donor specimens were heat-inactivated and served as control grafts (n=7).

RESULTS

In all animals receiving parathyroid transplants, intact human parathyroid hormone levels were detectable by species-specific enzyme-linked immunosorbent assay analysis of plasma samples on day 5 after transplantation and increased by 2.5-fold over the observation period (19 days) in contrast with controls. Plasma Ca levels revealed no differences between the groups. On day 5 after transplantation, intravital fluorescence microscopy revealed murine angiogenic microvessels sprouting along nonperfused human donor vessels, and 1 week later functional microvasculature was established in all parathyroid transplants. Histologic analysis revealed well-vascularized endocrine tissue. In contrast, control grafts were necrotic and partly resorbed; they exhibited no angiogenic activity or well-vascularized fat cells indicating fatty degeneration. In addition, species-specific Western blot analysis revealed vascular endothelial growth factor expression of parathyroid transplants rather than functional vessel density as the functional parameter of angiogenesis determining transplant function in vivo.

CONCLUSION

This model may serve to understand mechanisms associated with specific parathyroid transplant angiogenesis and its significance for transplant function to optimize clinical success of autotransplantation in therapy-resistant patients.

Rapid Perfusion and Network Remodeling in a Microvascular Construct After Implantation

OBJECTIVE

We have previously demonstrated the ability to construct 3-dimensional microvascular beds in vitro via angiogenesis from isolated, intact, microvessel fragments that retain endothelial cells and perivascular cells. Our objective was to develop and characterize an experimental model of tissue vascularization, based on the implantation of this microvascular construct, which recapitulated angiogenesis, vessel differentiation, and network maturation.

METHODS AND RESULTS

On implantation in a severe combined-immunodeficient mouse model, vessels in the microvascular constructs rapidly inosculated with the recipient host circulation. Ink perfusion of implants via the left ventricle of the host demonstrated that vessel inosculation begins within the first day after implantation. Evaluation of explanted constructs over the course of 28 days revealed the presence of a mature functional microvascular bed. Using a probe specific for the original microvessel source, 91.7%+/-11% and 88.6%+/-19% of the vessels by day 5 and day 28 after implantation, respectively, were derived from the original microvessel isolate. Similar results were obtained when human-derived microvessels were used to build the microvascular construct.

CONCLUSIONS

With this model, we reproduce the important aspects of vascularization, angiogenesis, inosculation, and network remodeling. Furthermore, we demonstrate that the model accommodates human-derived vessel fragments, enabling the construction of human-mouse vascular chimeras.

Angiogenesis and bone repair

The intimate connection, both physical and biochemical, between blood vessels and bone cells has long been recognized. Genetic, biochemical, and pharmacological studies have identified and characterized factors involved in the conversation between endothelial cells (EC) and osteoblasts (OB) during both bone formation and repair. The long-awaited FDA approval of two growth factors, BMP-2 and OP-1, with angiogenic and osteogenic activity confirms the importance of these two processes in human skeletal healing. In this review, the role of osteogenic factors in the adaptive response and interactive function of OB and EC during the multi-step process of bone repair will be discussed.

Parathyroid autotransplantation during thyroidectomy

Permanent hypoparathyroidism is a debilitating morbidity following thyroidectomy, with a reported incidence of up to 43%. Apart from meticulous dissection to preserve parathyroid glands and their blood supply, parathyroid autotransplantation (PA) has been increasingly employed to preserve parathyroid function. The adoption of PA during thyroidectomy has been reported to be associated with a low incidence of permanent hypoparathyroidism. Biochemical function of parathyroid autografts can be demonstrated objectively by forearm reimplantation or during long-term follow up. The clearest indication for PA is for inadvertently removed or devascularized parathyroid glands during thyroid surgery. Other strategies, including routine autotransplantation of at least one parathyroid gland, can be considered, but is associated with a high incidence of transient hypocalcaemia. Apart from refinement in technique to facilitate graft success, a reliable way to assess overall parathyroid function or viability of individual parathyroid gland may assist in monitoring parathyroid function and selecting patients requiring this procedure to prevent permanent hypoparathyroidism.

Parathyroid-produced angiopoietin-2 modulates angiogenic response

BACKGROUND

Upon explant, parathyroid tissue (PTH) upregulates vascular endothelial growth factor (VEGF), a potent endothelial cell mitogen, yet PTH induces a more robust angiogenic response than VEGF alone. This implies that other angiogenic factors are also produced. We tested PTH for production and function of angiopoietin-2 (Ang-2), a protein known to modulate VEGF response.

METHODS

With use of reverse transcriptase-polymerase chain reaction and SELDI (Surface Enhanced Laser Desorption/Ionization) (Ciphergen, Freemont, Calif) technology, we tested explanted PTH for Ang-2 production and determined the time sequence of Ang-2 upregulation. With use of an in vitro rat microvessel angiogenesis assay, we determined the angiogenic response to PTH-produced Ang-2.

RESULTS

Ang-2 messenger RNA was induced within 1 hour of parathyroid explant, with a maximum level detectable at 24 hours. Ang-2 protein production was maximal at 24 hours, with elimination by 48 hours. Ang-2 supplemented gels appeared to prompt earlier angiogenic induction, whereas sequestration of Ang-2 with soluble Tie2 receptor appeared to delay angiogenic induction. Soluble Tie2 treatment did not significantly decrease cumulative microvessel length, and no significant increase in neovessel length was seen with Ang-2 supplemented gels.

CONCLUSIONS

PTH upregulates Ang-2 upon explantation, with peak protein production by 24 hours. Ang-2 appears to functionally enhance initiation of PTH-induced angiogenesis, although the ultimate neovessel length appears to be dependent on other PTH-produced factors.