Michael Pedersen

Background: Routine use of the chorioallantoic membrane (CAM) tumor model in nuclear imaging studies is hampered by small tumors, embryonic movements and laborious volume-restricted intravenous tracer/drug administration. We sought a workaround by using fast-growing tumors, high-resolution autoradiography and non-intravenous tracer administration. Methods: Dekalb White chicken eggs were grafted with C3H mammary carcinoma fragments or MOC2 oral squamous cell carcinoma fragments from donor mice. The tumor uptake of ¹⁸F-fluorodeoxyglucose (FDG) following in-yolk-sac injection, dripping after CAM scoring or allantoic cavity injection was evaluated using positron emission tomography (PET) and autoradiography. Using in-yolk-sac injection, eggs were administered different tracer mixtures, namely (1) pimonidazole (hypoxia-marker), FDG and ¹⁴C-2-deoxyglucose (¹⁴C-2DG), (2) pimonidazole, FDG and ¹⁴C-acetate or (3) pimonidazole, the hypoxia-selective tracer ¹⁸F-fluoroazomycin-arabinoside (FAZA) and ¹⁴C-2DG. For comparison, tumor-bearing mice were administered FDG/¹⁴C-acetate/pimonidazole. Gross tumor uptake was evaluated using PET. Tumor cryosections were analyzed using dual-tracer autoradiography. Complementary autoradiograms were co-registered, covered by a square grid (0.5 × 0.5 mm). Pearson correlation coefficients (PCC) were calculated from scatterplots. Results: C3H tumors reached a mean weight (with 95% confidence interval) of 0.32 g (0.28–0.37 g), while for MOC2, it was 0.19 g (0.09–0.29 g). In-yolk-sac tracer injection was simple and effective, producing high tracer uptake and contrast 3 h post-administration. Spatial tracer overlap (PCC) was: FDG vs. ¹⁴C-2DG, 0.95–0.97; FAZA vs. ¹⁴C-2DG, 0.71–0.79 and FDG vs. ¹⁴C-acetate, 0.26–0.84 (0.15–0.76 in mice). Pimonidazole revealed tumor hypoxia. Conclusions: Direct-grafting from donor mice generated larger tumors than previously reported. In-yolk-sac tracer administration was practical and allowed larger injected volumes. Autoradiography revealed that: (1) FDG and ¹⁴C-2DG can be used interchangeably, (2) ¹⁴C-2DG was elevated in FAZA-positive areas, suggesting that in some tumors FDG-PET may provide information on the intratumoral distribution of hypoxic areas, and (3) FDG and ¹⁴C-acetate showed variable overlap. We conclude that in-yolk-sac tracer injection and autoradiography simplify and optimize CAM-based nuclear imaging research.

Purpose This study aimed to investigate the correlation between Eustachian tube (ET) dimensions and Eustachian tube dysfunction (ETD). Methods A total of 28 patients with ETD symptoms ≥ three months and ten controls underwent 3 Tesla magnetic resonance imaging (MRI) and Cone beam computed tomography (CBCT) scans. The images were fused with software using anatomical landmarks. ET dimensions and angles were registered. Results Patient and control demographics were comparable. The length of ET was longer in ETD ears compared to controls (p = 0.035) but not compared to the ETD patient’s asymptomatic ears (p > 0.05). ET length was longer in males compared to females in the ETD group (p < 0.001). The osseous ET was longer in the patients’ ETD ears compared to their asymptomatic ears. Cartilaginous ET was shorter in controls compared to ETD ears. No significant length differences (p > 0.05) were observed between sides in ET, CET, or OET. A positive correlation was found between ET length and height (p < 0.001). No significant differences in angles were found between ETD ears, asymptomatic ears, or controls against either the horizontal or the sagittal plane. Conclusion Fusion of MRI and CBCT is feasible for evaluating ET. Adjusting for height, no differences in ET length between sexes were found. OET was longer in symptomatic ears, and CET was shorter in controls. ETD seems associated with a longer ET. Ostmann’s Fat Pad and the levator veli palatini muscle were smaller in ETD ears, suggesting atrophy of ET components.

Knee osteoarthritis (OA) is a chronic, progressive, inflammatory, and degenerative whole-joint disease. Early-stage OA treatments typically include physiotherapy, weight-loss, pain relief medications, and intra-articular knee injections, such as corticosteroids, hyaluronic acid, or platelet-rich plasma. These treatments primarily provide symptomatic relief rather than reversing or halting disease progression. Recently, mesenchymal stromal cell (MSC) injections have garnered attention due to their immunomodulatory and regenerative capacities. MSCs, which can be derived from sources such as bone marrow, umbilical cord, or adipose tissue, and can be allogeneic or autologous, have demonstrated promising results in both animal models and several human studies. However, different protocols have been employed, presenting challenges for comparing outcomes. In this review, we address these variable settings, evaluate current practices, and identify key factors critical in optimizing MSC-based therapies by critically reviewing clinical trials of ex vivo expanded MSC therapies for OA undertaken between 2008 and 2023. Specific attention was given to two key aspects: (1) the cell culture process employed in manufacturing of autologous or allogeneic MSC products, and (2) the post-culture methods employed in storage, reconstitution and administration of the MSCs. Our findings suggest that standardizing MSC production for clinical applications remains a significant challenge, primarily due to variations in tissue sources, harvesting techniques, and manufacturing protocols, and due to broad discrepancies in reporting. Thus, we propose a set of minimal reporting criteria to guide future clinical trials. A common reporting guideline is a critical step towards a more standardized MSC production across different laboratories and clinical settings, thereby enhancing reproducibility and advancing the field of regenerative medicine for knee OA, as well as other disease settings.

Background It has been suggested that intraspinal pressure (ISP) below the dura is elevated following traumatic spinal cord injury (TSCI). The dura can maintain the pressure, and hence a subdural compartment syndrome has been hypothesized to develop regardless of bony decompression. This study aimed to evaluate whether a such intradural compartment syndrome develops during the first 72 h in a porcine TSCI model. Methods First, in a randomized sham controlled-trial design, longitudinal ISP measurements were performed over a period of 72 h from onset of TSCI. TSCI was inflicted by a weight-drop contusion regime: 75-g rod, 75-mm free fall, and 5-min compression of the spinal cord. Second, in a sham-controlled dose-response design longitudinal ISP measurements were performed over a period of 16 h from the onset of TSCI, using two other contusion regimes: 75-g rod, 125-mm free fall, and 5-min compression; and 75-g rod, 75-mm free fall, and 240-min compression. Animals were kept sedated for the entire course of the study using propofol, fentanyl, and midazolam. Results Intraspinal pressure increased in TSCI and sham animals alike, but we found no significant increases in ISP following TSCI compared with the sham group, and we found no relationship between the ISP increase and larger impacts or increased time of compression. Conclusion These findings suggest that the subdural swelling of the spinal cord following thoracic TSCI is not responsible for the ISP increase measured in our TSCI model, but that the ISP increase was caused by the surgical procedure or the reconstitution of normal cerebrospinal fluid pressure.

The aim was to establish combined H₂¹⁵O PET/MRI during ex vivo normothermic machine perfusion (NMP) of isolated porcine kidneys. We examined whether changes in renal arterial blood flow (RABF) are accompanied by changes of a similar magnitude in renal blood perfusion (RBP) as well as the relation between RBP and renal parenchymal oxygenation (RPO). Methods: Pig kidneys (n = 7) were connected to a NMP circuit. PET/MRI was performed at two different pump flow levels: a blood-oxygenation-level-dependent (BOLD) MRI sequence performed simultaneously with a H₂¹⁵O PET sequence for determination of RBP. Results: RBP was measured using H₂¹⁵O PET in all kidneys (flow 1: 0.42–0.76 mL/min/g, flow 2: 0.7–1.6 mL/min/g). We found a linear correlation between changes in delivered blood flow from the perfusion pump and changes in the measured RBP using PET imaging (r² = 0.87). Conclusion: Our study demonstrated the feasibility of combined H₂¹⁵O PET/MRI during NMP of isolated porcine kidneys with tissue oxygenation being stable over time. The introduction of H215O PET/MRI in nephrological research could be highly relevant for future pre-transplant kidney evaluation and as a tool for studying renal physiology in healthy and diseased kidneys.

Tracheostomy decannulation leaves an iatrogenic passage in the upper airways. Inadequate sealing leads to pulmonary dysfunction and reduced voice quality. This study aimed to investigate the feasibility and impact of intratracheal tracheostomy sealing on laryngeal airflow and voice quality immediately after decannulation (ClinicalTrials.gov: NCT06138093). Fifteen adult, tracheostomized, intensive care unit patients were included from our hospital. A temporary, silicone-based sealing disc was inserted in the tracheostomy wound immediately after decannulation. Spirometry with measurement of forced vital capacity (FVC), forced expiratory volume in the first second (FEV₁), and peak expiratory flow (PEF) were performed as measures of airway flow. Voice recordings were assessed using an equal appearing interval scale from 1 to 5. Median FVC, FEV₁, PEF, and voice quality score with interquartile range (IQR) was 883 (510–1910) vs. 1260 (1005–1723) mL (p < 0.001), 790 (465–1255) vs. 870 (617–1297) mL (p < 0.001), 103 (55–211) vs. 107 (62–173) mL (p = 0.720), and 2 (1–2.5) vs. 4 (3–5) points (p < 0.001), respectively, with open tracheostomy vs. after sealing the tracheostomy with the intratracheal sealing disc. This feasibility study showed that tracheostomy sealing with the intratracheal disc was safe and led to immediate improvements in FVC, FEV₁, and voice quality.

Normothermic regional perfusion (NRP) allows assessment of therapeutic interventions prior to donation after circulatory death transplantation. Sodium-3-hydroxybutyrate (3-OHB) increases cardiac output in heart failure patients and diminishes ischemia–reperfusion injury, presumably by improving mitochondrial metabolism. We investigated effects of 3-OHB on cardiac and mitochondrial function in transplanted hearts and in cardiac organoids. Donor pigs (n = 14) underwent circulatory death followed by NRP. Following static cold storage, hearts were transplanted into recipient pigs. 3-OHB or Ringer’s acetate infusions were initiated during NRP and after transplantation. We evaluated hemodynamics and mitochondrial function. 3-OHB mediated effects on contractility, relaxation, calcium, and conduction were tested in cardiac organoids from human pluripotent stem cells. Following NRP, 3-OHB increased cardiac output (P < 0.0001) by increasing stroke volume (P = 0.006), dP/dt (P = 0.02) and reducing arterial elastance (P = 0.02). Following transplantation, infusion of 3-OHB maintained mitochondrial respiration (P = 0.009) but caused inotropy-resistant vasoplegia that prevented weaning. In cardiac organoids, 3-OHB increased contraction amplitude (P = 0.002) and shortened contraction duration (P = 0.013) without affecting calcium handling or conduction velocity. 3-OHB had beneficial cardiac effects and may have a potential to secure cardiac function during heart transplantation. Further studies are needed to optimize administration practice in donors and recipients and to validate the effect on mitochondrial function.

The prevalence of obesity is increasing, and the origins of obesity and metabolic dysfunction may be traced back to fetal life. Currently, overweight pregnant women are advised to substitute sugar-sweetened beverages with diet drinks containing artificial sweeteners. Recent evidence suggests that the consumption of artificial sweeteners during pregnancy increases the risk of obesity in the child, but the mechanism is unknown. We hypothesized the transportation of artificial sweeteners across the placenta into the fetal circulation and the amniotic fluid. We included 19 pregnant women who were given an oral dose of acesulfame, cyclamate, saccharin, and sucralose immediately before a planned caesarean section. Nine women were included as controls, and they refrained from an intake of artificial sweeteners. The maternal and fetal blood and amniotic fluid were collected during the caesarean section, and concentrations of artificial sweeteners were measured using mass spectrometry. We found a linear relationship between the fetal plasma concentrations of artificial sweeteners and the maternal plasma concentrations, with adjusted coefficients of 0.49 (95% CI: 0.28–0.70) for acesulfame, 0.72 (95% CI: 0.48–0.95) for cyclamate, 0.51 (95% CI: 0.38–0.67) for saccharin, and 0.44 (95% CI: 0.33–0.55) for sucralose. We found no linear relationship between amniotic fluid and fetal plasma concentrations, but there were positive ratios for all four sweeteners. In conclusion, the four sweeteners investigated all crossed the placenta and were present in the fetal circulation and amniotic fluid.

Neovascularization plays an essential part in the progression of several diseases as well as recovery processes such as angiogenesis-guided neurogenesis after a spinal cord injury. To visualize and quantify neovascularization in an experimental setup, it is desirable to apply a noninvasive, repeatable, and harmless technique. Here, we apply a newly developed ultrasound-based technique to construct angiographies and quantify neovascularization in the regenerating spinal cord of a regeneration competent animal model, the Mexican axolotl. We measured vessel volume fraction prior to the induction of contusion and transection spinal cord injury and repeated this measurement directly after injury and at 3, 6, 12, and 63 days after injury. Although neither of the injury types resulted in statistically significant differences in vessel volume fraction relative to sham-operated animals, there was a statistically significant increase in neovascularization over time in all groups. Additionally, vessel volume fraction at the final time point (63 days after injury) was quantified with micro-CT imaging after vascular perfusion with a contrast agent, confirming no statistically significant difference in neovascularization between injury types. Ex vivo vessel volume fraction measured by micro-CT was significantly different from the in vivo ultrasound-based measurement at the same time point. This is likely a result of incomplete vascular perfusion with the contrast agent before micro-CT imaging, which was supported by subsequent histological evaluation. In summary, the results suggest that the ultrasound-based angiographic procedure, we demonstrate here, is applicable to visualize and quantify neovascularization in a noninvasive and harmless fashion in longitudinal experiments circumventing the limitations of contrast agent-dependent techniques.