TDP43 Interacts with MLH1 and MSH6 Proteins in A DNA Damage-Inducible Manner.

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease that affects the motor neuron. One aspect of the neuropathology involved in ALS includes increased genomic damage and impaired DNA repair capability. The TAR-DNA binding protein 43 (TDP43) has been associated with both sporadic and familial forms of ALS, and is typically observed as cytosolic mislocalization of protein aggregates, termed TDP43 proteinopathy. TDP43 is a ubiquitous RNA/DNA binding protein with functional implications in a wide range of disease processes, including the repair of DNA double strand breaks (DSBs). While TDP43 is widely known to regulate RNA metabolism, our lab has reported it also functions directly at the protein level to facilitate DNA repair. Here, we show that TDP43 protein interacts with DNA mismatch repair (MMR) proteins MLH1 and MSH6 in a DNA damage-inducible manner. We utilized differentiated SH-SY5Y neuronal cultures to identify this inducible relationship using complimentary approaches of proximity ligation assay (PLA) and co-immunoprecipitation (CoIP) assay. We observed that signals of TDP43 interaction with MLH1 and MSH6 increased significantly following a 2 hr treatment of 10µM methylmethanesulfonate (MMS), a DNA alkylating agent used to induce MMR repair. Likewise, we observed this effect was abolished in cell lines treated with siRNA directed against TDP43. Finally, we demonstrated these protein interactions were significantly increased in lumbar spinal cord samples of ALS-affected patients compared to age-matched controls. These results will inform our future studies to understand the mechanisms and consequences of this TDP43-MMR interaction in the context of ALS affected neurons.

TDP43 interacts with MLH1 and MSH6 proteins in a DNA damage-inducible manner.

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease that affects the motor neuron. One aspect of the neuropathology involved in ALS includes increased genomic damage and impaired DNA repair capability. The TAR-DNA binding protein 43 (TDP43) has been associated with both sporadic and familial forms of ALS, and is typically observed as cytosolic mislocalization of protein aggregates, termed TDP43 proteinopathy. TDP43 is a ubiquitous RNA/DNA binding protein with functional implications in a wide range of disease processes, including the repair of DNA double-strand breaks (DSBs). While TDP43 is widely known to regulate RNA metabolism, our lab has reported it also functions directly at the protein level to facilitate DNA repair. Here, we show that the TDP43 protein interacts with DNA mismatch repair (MMR) proteins MLH1 and MSH6 in a DNA damage-inducible manner. We utilized differentiated SH-SY5Y neuronal cultures to identify this inducible relationship using complementary approaches of proximity ligation assay (PLA) and co-immunoprecipitation (CoIP) assay. We observed that signals of TDP43 interaction with MLH1 and MSH6 increased significantly following a 2 h treatment of 10 µM methylmethanesulfonate (MMS), a DNA alkylating agent used to induce MMR repair. Likewise, we observed this effect was abolished in cell lines treated with siRNA directed against TDP43. Finally, we demonstrated these protein interactions were significantly increased in lumbar spinal cord samples of ALS-affected patients compared to age-matched controls. These results will inform our future studies to understand the mechanisms and consequences of this TDP43-MMR interaction in the context of ALS-affected neurons.

Characterization of pain-related behaviors in a rat model of acute-to-chronic low back pain: single vs. multi-level disc injury.

Introduction: Low back pain is the most common type of chronic pain. We examined pain-related behaviors across 18 weeks in rats that received injury to one or two lumbar intervertebral discs (IVD) to determine if multi-level disc injuries enhance/prolong pain. Methods: Twenty-three Sprague-Dawley adult female rats were used: 8 received disc puncture (DP) of one lumbar IVD (L5/6, DP-1); 8 received DP of two lumbar IVDs (L4/5 & L5/6, DP-2); 8 underwent sham surgery. Results: DP-2 rats showed local (low back) sensitivity to pressure at 6- and 12-weeks post-injury, and remote sensitivity to pressure (upper thighs) at 12- and 18-weeks and touch (hind paws) at 6, 12 and 18-weeks. DP-1 rats showed local and remote pressure sensitivity at 12-weeks only (and no tactile sensitivity), relative to Sham DP rats. Both DP groups showed reduced distance traveled during gait testing over multiple weeks, compared to pre-injury; only DP-2 rats showed reduced distance relative to Sham DP rats at 12-weeks. DP-2 rats displayed reduced positive interactions with a novel adult female rat at 3-weeks and hesitation and freezing during gait assays from 6-weeks onwards. At study end (18-weeks), radiological and histological analyses revealed reduced disc height and degeneration of punctured IVDs. Serum BDNF and TNFα levels were higher at 18-weeks in DP-2 rats, relative to Sham DP rats, and levels correlated positively with remote sensitivity in hind paws (tactile) and thighs (pressure). Discussion: Thus, multi-level disc injuries resulted in earlier, prolonged and greater discomfort locally and remotely, than single-level disc injury. BDNF and TNFα may have contributing roles.

Adjuvant Human Papillomavirus Vaccination in Recurrent Respiratory Papilloma Patients Older than 45.

OBJECTIVES: The primary objective was to examine the intersurgical interval (ISI) of recurrent respiratory papillomatosis (RRP) in patients older than 45 years before and after a Gardasil vaccination series. METHODS: We conducted a retrospective chart review of adult patients >45 years of age diagnosed with RRP from 2012 to 2022. Patients were excluded if they did not receive at least two doses of the Gardasil vaccine series or if they underwent two or fewer surgeries during the study period. RESULTS: Thirteen patients met the inclusion criteria, 11 males and two females. The age at initial diagnosis ranged from 46 to 80 years, with a mean of 59 years. There was a significant increase in the average ISI, from 126 ± 87 days pre-vaccination compared to 494 ± 588 days post-vaccination (p < 0.01). The average number of surgeries per patient was 6.8 ± 2.4 over an average follow-up of 49.7 ± 30.3 months. CONCLUSION: Adjuvant Gardasil use in RRP patients older than 45 years significantly increases the ISI. Current CDC recommendations include only patients ages 9 to 45, but this study provides evidence that RRP patients outside this age range may benefit from adjuvant HPV vaccination. LEVEL OF EVIDENCE: 4 Laryngoscope, 134:3226-3229, 2024.

Surgical Outcomes in Zenker Diverticula: A Multicenter, Prospective, Longitudinal Study.

OBJECTIVE: To compare improvement in patient-reported outcomes (PROM) in persons undergoing endoscopic and open surgical management of Zenker diverticula (ZD). METHODOLOGY: Prospective, multicenter cohort study of all individuals enrolled in the Prospective OUtcomes of Cricopharyngeus Hypertonicity (POUCH) Collaborative who underwent surgery for ZD. Patient survey, radiography reports, and the 10-item Eating Assessment Tool (EAT-10) pre- and post-procedure were abstracted from a REDCap database, which summarized means, medians, percentages, and frequencies of. Outcome based on operative intervention (endoscopic vs. open) was compared using t-test, Wilcoxon rank sum test or chi-square test, as appropriate. RESULTS: One hundred and forty-seven persons were prospectively followed. The mean age (SD) of the cohort was 68.7 (11.0). Overall, 66% of patients reported 100% improvement in EAT-10; 81% of patients had greater than 75% improvement; and 88% had greater than 50% improvement. Endoscopic was used for n = 109 patients, and open surgical intervention was used for n = 38. The median [interquartile range, IQR] EAT-10 percent improvement for endoscopic treatment was 93.3% [72, 100], and open was 100% [92.3, 100] (p = 0.05). The incidence of intraoperative complications was 3.7% for endoscopic and 7.9% for open surgical management. The median [IQR] in follow-up was 86 and 97.5 days, respectively. CONCLUSION: Both endoscopic and open surgical management of ZD provide significant improvement in patient-reported outcomes. The data suggest that open diverticulectomy may provide a modest advantage in symptomatic improvement compared to endoscopic management. The data suggest that the postoperative complication rate is higher in the open surgical group. LEVEL OF EVIDENCE: 3 Laryngoscope, 134:97-102, 2024.

Postoperative Care of Zenker Diverticula: Contemporary Perspective from the Prospective OUtcomes Cricopharyngeaus Hypertonicity (POUCH) Collaborative.

OBJECTIVES: The aim of the study was to identify trends in postoperative management of persons undergoing surgery for Zenker diverticula (ZD) by evaluating length of stay (LOS), diet on discharge, and imaging with or without surgical complication. METHODS: Prospectively enrolled adult patients with cricopharyngeal muscle dysfunction with diverticula undergoing surgery from August 1, 2017 to February 1, 2023 were included. Data were extracted from a multi-institutional REDCap database, summarizing means, medians, percentages, and frequencies. Fisher's exact or chi squared analyses were utilized, as appropriate, to compare subsets of data. Descriptive analysis assessed differences in clinical course and the relationship to postoperative management. RESULTS: There were 298 patients with a mean (standard deviation) age of 71.8 (11.2) years and 60% male. Endoscopic surgery was performed in 79.5% (237/298) of patients versus 20.5% (61/298) open surgery. Sixty patients (20.1%) received postoperative imaging, with four leaks identified. Complications were identified in 9.4% of cases (n = 29 complications in 28 patients), more commonly in open surgery. Most (81.2%) patients were discharged within 23 h. About half of patients (49%) were discharged from the hospital on a pureed/liquid diet; 36% had been advanced to a soft diet. In patients without complications, LOS was significantly longer following open cases (p = 0.002); postoperative diet was not different between open and endoscopic (p = 0.26). CONCLUSIONS: Overall, most patients are discharged within 23 h without imaging. However, LOS was affected by surgical approach. Postoperative complications are different in endoscopic versus open surgery. Complications with either approach were associated with prolonged LOS, need for imaging, and diet restriction. LEVEL OF EVIDENCE: Level III Laryngoscope, 134:2678-2683, 2024.

Coxsackievirus B3 infects and disrupts human induced-pluripotent stem cell derived brain-like endothelial cells.

Coxsackievirus B3 (CVB3) is a significant human pathogen that is commonly found worldwide. CVB3 among other enteroviruses, are the leading causes of aseptic meningo-encephalitis which can be fatal especially in young children. How the virus gains access to the brain is poorly-understood, and the host-virus interactions that occur at the blood-brain barrier (BBB) is even less-characterized. The BBB is a highly specialized biological barrier consisting primarily of brain endothelial cells which possess unique barrier properties and facilitate the passage of nutrients into the brain while restricting access to toxins and pathogens including viruses. To determine the effects of CVB3 infection on the BBB, we utilized a model of human induced-pluripotent stem cell-derived brain-like endothelial cells (iBECs) to ascertain if CVB3 infection may alter barrier cell function and overall survival. In this study, we determined that these iBECs indeed are susceptible to CVB3 infection and release high titers of extracellular virus. We also determined that infected iBECs maintain high transendothelial electrical resistance (TEER) during early infection despite possessing high viral load. TEER progressively declines at later stages of infection. Interestingly, despite the high viral burden and TEER disruptions at later timepoints, infected iBEC monolayers remain intact, indicating a low degree of late-stage virally-mediated cell death, which may contribute to prolonged viral shedding. We had previously reported that CVB3 infections rely on the activation of transient receptor vanilloid potential 1 (TRPV1) and found that inhibiting TRPV1 activity with SB-366791 significantly limited CVB3 infection of HeLa cervical cancer cells. Similarly in this study, we observed that treating iBECs with SB-366791 significantly reduced CVB3 infection, which suggests that not only can this drug potentially limit viral entry into the brain, but also demonstrates that this infection model could be a valuable platform for testing antiviral treatments of neurotropic viruses. In all, our findings elucidate the unique effects of CVB3 infection on the BBB and shed light on potential mechanisms by which the virus can initiate infections in the brain.

DAXX drives de novo lipogenesis and contributes to tumorigenesis.

Cancer cells exhibit elevated lipid synthesis. In breast and other cancer types, genes involved in lipid production are highly upregulated, but the mechanisms that control their expression remain poorly understood. Using integrated transcriptomic, lipidomic, and molecular studies, here we report that DAXX is a regulator of oncogenic lipogenesis. DAXX depletion attenuates, while its overexpression enhances, lipogenic gene expression, lipogenesis, and tumor growth. Mechanistically, DAXX interacts with SREBP1 and SREBP2 and activates SREBP-mediated transcription. DAXX associates with lipogenic gene promoters through SREBPs. Underscoring the critical roles for the DAXX-SREBP interaction for lipogenesis, SREBP2 knockdown attenuates tumor growth in cells with DAXX overexpression, and DAXX mutants unable to bind SREBP1/2 have weakened activity in promoting lipogenesis and tumor growth. Remarkably, a DAXX mutant deficient of SUMO-binding fails to activate SREBP1/2 and lipogenesis due to impaired SREBP binding and chromatin recruitment and is defective of stimulating tumorigenesis. Hence, DAXX's SUMO-binding activity is critical to oncogenic lipogenesis. Notably, a peptide corresponding to DAXX's C-terminal SUMO-interacting motif (SIM2) is cell-membrane permeable, disrupts the DAXX-SREBP1/2 interactions, and inhibits lipogenesis and tumor growth. These results establish DAXX as a regulator of lipogenesis and a potential therapeutic target for cancer therapy.

Synthesis and Characterization of Quercetin-Iron Complex Nanoparticles for Overcoming Drug Resistance.

Quercetin, one of the major natural flavonoids, has demonstrated great pharmacological potential as an antioxidant and in overcoming drug resistance. However, its low aqueous solubility and poor stability limit its potential applications. Previous studies suggest that the formation of quercetin-metal complexes could increase quercetin stability and biological activity. In this paper, we systematically investigated the formation of quercetin-iron complex nanoparticles by varying the ligand-to-metal ratios with the goal of increasing the aqueous solubility and stability of quercetin. It was found that quercetin-iron complex nanoparticles could be reproducibly synthesized with several ligand-to-iron ratios at room temperature. The UV-Vis spectra of the nanoparticles indicated that nanoparticle formation greatly increased the stability and solubility of quercetin. Compared to free quercetin, the quercetin-iron complex nanoparticles exhibited enhanced antioxidant activities and elongated effects. Our preliminary cellular evaluation suggests that these nanoparticles had minimal cytotoxicity and could effectively block the efflux pump of cells, indicating their potential for cancer treatment.

Smoking and Carcinoma Trends in Recurrent Respiratory Papillomatosis Patients.

INTRODUCTION: Recurrent respiratory papillomatosis (RRP) is a chronic disease of the upper respiratory tract caused by human papillomavirus types 6 and 11. The disease course is characteristically unpredictable, ranging from spontaneous remission to aggressive, recurrent disease. Thus, management is often challenging and requires unique approaches tailored to each individual patient. While recent literature has described risk factors for more aggressive disease, few sources have investigated the impact of smoking on RRP disease course and risk for malignant transformation. METHODS: A retrospective chart review was conducted for adult RRP patients evaluated at an academic tertiary care center between 2005 and 2020. A total of 188 patients were identified. Demographic and clinical data were collected, including smoking and alcohol history, HPV subtype, history of dysplasia and/or carcinoma, voice handicap index scores, Derkay scores, debulkings (in office and operating room), and days to papilloma recurrence. RESULTS: Malignant degeneration in RRP occurred in 16.3% of smokers and 3.6% of nonsmokers. Smokers who developed carcinoma had less debulkings per years of evaluation than those not developing carcinoma (0.21 vs 0.92, P = .004). Additionally, patients that either presented with or developed carcinoma during their course had a higher pack-year smoking history (18.0 vs 12.21, P = .0002). No difference in days to recurrence or inter-surgical interval was demonstrated between smokers and nonsmokers. CONCLUSIONS: The report demonstrates that smoking can increase the risk of malignant transformation in RRP patients.

Killian Jamieson Diverticulum, the Great Mimicker: A Case Series and Contemporary Review.

OBJECTIVE: To assess barium esophagram (BAS) as a diagnostic marker for patients with Killian Jamieson diverticula (KJD). METHODS: Prospective, multicenter cohort study of individuals enrolled in the Prospective OUtcomes of Cricopharyngeus Hypertonicity (POUCH) Collaborative. Patient demographics, comorbidities, radiographic imaging reports, laryngoscopy findings, patient-reported outcome measures (PROM), and operative reporting were abstracted from a REDCap database and summarized using means, medians, percentages, frequencies. Paired t-tests and Wilcoxon Signed Rank test were used to test pre- to post-operative differences in RSI, EAT-10, and VHI-10 scores. Diagnostic test evaluation including sensitivity, specificity, positive, and negative predictive value with 95% confidence intervals were calculated comparing BAS findings to operative report. RESULTS: A total of 287 persons were enrolled; 13 (4%) patients were identified with confirmed KJD on operative reports. 100% underwent open transcervical excision. BAS has a 46.2% (95% confidence interval [CI]: 23.2, 70.9) sensitivity and 97.8% (95% CI: 95.3, 99.0) specificity in detecting a KJD and 50% (95% CI: 25.4, 74.6) positive predictive value but 97.4% (95%CI: 94.8, 98.7) negative predictive value. Preoperatively, patients reported mean (SD) RSI and EAT-10 of 19.4 (9) and 8.3 (7.5) accordingly. Postoperatively, patients reported mean (SD) RSI and EAT-10 as 5.4 (6.2) and 2.3 (3.3). Both changes in RSI and EAT-10 were statistically significant (p = 0.008, p = 0.03). CONCLUSION: KJD are rare and represent <5% of hypopharyngeal diverticula undergoing surgical intervention. Open transcervical surgery significantly improves symptoms of dysphagia. BAS has high specificity but low sensitivity in detecting KJD. LEVEL OF EVIDENCE: 4 Laryngoscope, 133:2110-2115, 2023.

Pediatric Sports Trauma.

Pediatric foot and ankle fractures are common in athletic participation. Treatment of pediatric sports trauma must take into account the unique challenges this population presents, and aim to minimize long-term complications. Given the excellent remodeling potential of pediatric bone, conservative treatment can often be used. However, a thorough understanding of physeal anatomy, fracture patterns, and biomechanics is needed to guide treatment choice and determine when surgical intervention is warranted.

Melanoma differentiation-associated gene 5 amyopathic dermatomyositis following an acute Mycoplasma pneumoniae infection: a case report.

BACKGROUND: A previously healthy young male of Southeast Asian descent presented with 6 weeks of fevers, cough, mucocutaneous ulcers, arthritis, and myalgias. Initial workup revealed positive Mycoplasma pneumoniae immunoglobulin M, and the patient was treated with antibiotics without relief of symptoms. Rheumatologic workup revealed highly positive melanoma differentiation-associated gene 5 antibody. Viral infections are thought to potentially trigger loss of self tolerance, and prompt the autoimmunity cascade that can result in conditions such as dermatomyositis. To our knowledge, this is the first case report demonstrating a non-viral infection, specifically Mycoplasma pneumoniae, as the inciting infectious trigger for the anti-melanoma differentiation-associated gene 5 dermatomyositis subtype. CASE PRESENTATION: A 20-year-old southeast Asian-American male with no significant past medical history presented with symptoms of intermittent fevers, nonproductive cough, dry eyes, oral ulcers, rash, arthritis, and myalgias. The patient was noted to have erythematous papules across the bilateral hands along the lateral digits and palms, as well as synovitis involving the bilateral hands and feet. Immunoglobulin M antibodies were positive for Mycoplasma pneumoniae. The patient was diagnosed with mycoplasma pneumonia. The patient did not respond to a course of antibiotics, leading to rheumatological testing that found highly positive melanoma differentiation-associated gene 5 autoantibody. Muscle enzyme and electromyography testing were normal, indicating clinically amyopathic disease. Methylprednisolone was initiated, with resolution of fevers and improvement of arthritis and myalgias. The cutaneous lesions on the digits and palms improved. CONCLUSIONS: This patient presented with symptoms of fever, cough, oral ulcers, rashes, and arthritis, and blood work demonstrated the presence of immunoglobulin M antibodies to Mycoplasma pneumoniae. Despite antibiotic treatment for the presumed diagnosis of Mycoplasma pneumoniae infection, the patient did not improve, prompting rheumatological workup and revealing melanoma differentiation-associated gene 5 autoantibodies. This case suggests that infections, other than viral, can trigger the autoinflammatory cascade, leading to the development of amyopathic melanoma differentiation-associated gene 5 dermatomyositis.

Development of a multicellular in vitro model of the meningeal blood-CSF barrier to study Neisseria meningitidis infection.

BACKGROUND: Bacterial meningitis is a life-threatening disease that occurs when pathogens such as Neisseria meningitidis cross the meningeal blood cerebrospinal fluid barrier (mBCSFB) and infect the meninges. Due to the human-specific nature of N. meningitidis, previous research investigating this complex host-pathogen interaction has mostly been done in vitro using immortalized brain endothelial cells (BECs) alone, which often do not retain relevant barrier properties in culture. Here, we developed physiologically relevant mBCSFB models using BECs in co-culture with leptomeningeal cells (LMCs) to examine N. meningitidis interaction. METHODS: We used BEC-like cells derived from induced pluripotent stem cells (iBECs) or hCMEC/D3 cells in co-culture with LMCs derived from tumor biopsies. We employed TEM and structured illumination microscopy to characterize the models as well as bacterial interaction. We measured TEER and sodium fluorescein (NaF) permeability to determine barrier tightness and integrity. We then analyzed bacterial adherence and penetration of the cell barrier and examined changes in host gene expression of tight junctions as well as chemokines and cytokines in response to infection. RESULTS: Both cell types remained distinct in co-culture and iBECs showed characteristic expression of BEC markers including tight junction proteins and endothelial markers. iBEC barrier function as determined by TEER and NaF permeability was improved by LMC co-culture and remained stable for seven days. BEC response to N. meningitidis infection was not affected by LMC co-culture. We detected considerable amounts of BEC-adherent meningococci and a relatively small number of intracellular bacteria. Interestingly, we discovered bacteria traversing the BEC-LMC barrier within the first 24 h post-infection, when barrier integrity was still high, suggesting a transcellular route for N. meningitidis into the CNS. Finally, we observed deterioration of barrier properties including loss of TEER and reduced expression of cell-junction components at late time points of infection. CONCLUSIONS: Here, we report, for the first time, on co-culture of human iPSC derived BECs or hCMEC/D3 with meningioma derived LMCs and find that LMC co-culture improves barrier properties of iBECs. These novel models allow for a better understanding of N. meningitidis interaction at the mBCSFB in a physiologically relevant setting.

Outcomes Following Open Reduction Internal Fixation of Ankle Fractures (ORIF) By Podiatric Surgeons.

Open reduction internal fixation of closed ankle fractures is a common procedure performed by podiatric surgeons. This is the first study to specifically evaluate complication rates of this procedure among podiatric surgeons using a large patient cohort. The rates of podiatric surgical complications were also compared to the complication rates reported in the orthopedic literature. There was no significant difference between podiatric surgeons and orthopedic surgeons with regards to surgical site infection. However, complication rates, including 1-year postsurgery deep vein thrombosis (DVT), malunion, and unplanned revision surgery within 90-day, were lower in our study, compared to the average rates reported in the orthopedic literature. The authors believe that the most important determinant for post ankle surgical complications is related to surgical volume and experience, rather than professional degree type.

Non-Hodgkin Lymphoma with Synovial Involvement of the Knee.

Musculoskeletal involvement occurs in approximately 25% of patients diagnosed with non-Hodgkin lymphoma (NHL). Skeletal involvement is typically secondary, with primary lymphoma of the bone being much rarer. We describe a case in which a 52-year-old man initially presented features suggestive of Lyme arthritis in his left knee. A synovial biopsy performed as part of a synovectomy procedure revealed a proliferative synovium with dense lymphoplasmacytic B cell infiltrate, suggestive of NHL. An inguinal lymph node biopsy was also performed but did not produce results pathologically similar to those of the left knee synovial biopsy.

Extracellular nucleotides enhance agonist potency at the parathyroid hormone 1 receptor.

Parathyroid hormone (PTH) activates the PTH/PTH-related peptide receptor (PTH1R) on osteoblasts and other target cells. Mechanical stimulation of cells, including osteoblasts, causes release of nucleotides such as ATP into the extracellular fluid. In addition to its role as an energy source, ATP serves as an agonist at P2 receptors and an allosteric regulator of many proteins. We investigated the effects of concentrations of extracellular ATP, comparable to those that activate low affinity P2X7 receptors, on PTH1R signaling. Cyclic AMP levels were monitored in real-time using a bioluminescence reporter and ß-arrestin recruitment to PTH1R was followed using a complementation-based luminescence assay. ATP markedly enhanced cyclic AMP and ß-arrestin signaling as well as downstream activation of CREB. CMP - a nucleotide that lacks a high energy bond and does not activate P2 receptors - mimicked this effect of ATP. Moreover, potentiation was not inhibited by P2 receptor antagonists, including a specific blocker of P2X7. Thus, nucleotide-induced potentiation of signaling pathways was independent of P2 receptor signaling. ATP and CMP reduced the concentration of PTH (1-34) required to produce a half-maximal cyclic AMP or ß-arrestin response, with no evident change in maximal receptor activity. Increased potency was similarly apparent with PTH1R agonists PTH (1-14) and PTH-related peptide (1-34). These observations suggest that extracellular nucleotides increase agonist affinity, efficacy or both, and are consistent with modulation of signaling at the level of the receptor or a closely associated protein. Taken together, our findings establish that ATP enhances PTH1R signaling through a heretofore unrecognized allosteric mechanism.

Feasibility of microvascular head and neck reconstruction in the setting of calcified arteriosclerosis of the vascular pedicle.

OBJECTIVE To report outcomes in free flap reconstructive surgery in the setting of calcified arteriosclerosis affecting the flap pedicle. DESIGN Retrospective review, including a detailed analysis of medical records, histopathologic findings, and a comprehensive review of the literature. METHODS A total of 1329 consecutive microvascular free tissue transfers were performed by 2 reconstructive surgeons at a university-affiliated tertiary care medical center from January 1, 1996, through December 31, 2011. Clinical notes, operative notes, and pathology reports were systematically reviewed to identify 44 patients (3%) with calcified arteriosclerosis involving the flap vascular pedicle. A comprehensive medical record review was performed for the included patients, detailing patient-related characteristics, flap survival, and incidence of perioperative complications. RESULTS A history of arteriosclerosis was identified preoperatively in 18 patients (41%). Eight patients (18%) were specifically recognized clinically and histologically to have a variant of arteriosclerosis known as Mönckeberg medial calcific sclerosis. In total, fibula osteocutaneous free flap was performed in 30 patients, radial forearm in 8 patients, rectus abdominus in 3 patients, latissimus dorsi in 2 patients, and parascapular in 1 patient. Perioperative complications occurred in 17 patients (39%), with the most common being pulmonary (14%) and cardiac (9%). Patient follow-up ranged from 3 to 137 months, with a mean postoperative follow-up of 21 months. The mean length of hospital stay was 12 days. There was a 0% incidence of total flap failure and a 7% incidence of partial flap necrosis. CONCLUSION Although technically challenging, successful microvascular free flap reconstruction can be achieved despite the presence of vascular calcifications affecting the flap vascular pedicle.