IL-1β + TGF-β2 dual-licensed mesenchymal stem cells have reduced major histocompatibility class I expression and positively modulate tenocyte migration, metabolism, and gene expression

OBJECTIVE

The study objectives were to 1) determine the mesenchymal stem cell (MSC) surface expression of major histocompatibility complex (MHC) class I and transcriptome-wide gene expression changes following IL-1β + TGF-β2 dual licensing and 2) evaluate if IL-1β + TGF-β2 dual-licensed MSCs had a greater ability to positively modulate tenocyte function compared to naive MSCs.

SAMPLES

Equine bone marrow-derived MSCs from 6 donors and equine superficial digital flexor tenocytes from 3 donors.

METHODS

Experiments were performed in vitro. Flow cytometry and bulk RNA sequencing were utilized to determine naive and dual-licensed MSC phenotype and transcriptome-wide changes in gene expression. Conditioned media were generated from MSCs and utilized in tenocyte cell culture assays as a method to determine the effect of MSC paracrine factors on tenocyte function.

RESULTS

Dual-licensed MSCs have a reduced expression of MHC class I and exhibit enrichment in functional pathways associated with the extracellular matrix, cell signaling, and tissue development. Additionally, dual-licensed MSC-conditioned media significantly improved in vitro tenocyte migration and metabolism to a greater degree than naive MSC-conditioned media. In tenocytes exposed to IL-1β, dual-licensed conditioned media also positively modulated tenocyte gene expression.

CLINICAL RELEVANCE

Our data indicate that conditioned media containing paracrine factors secreted from dual-licensed MSCs significantly modulates in vitro tenocyte function, which may confer benefits in vivo to healing tendons following injury. Additionally, due to reduced MHC class I expression in dual-licensed MSCs, this technique may also provide an avenue to provide an effective "off-the-shelf" allogenic source of MSCs.

Surgical procedure of intratympanic injection and inner ear pharmacokinetics simulation in domestic pigs

Introduction: One major obstacle in validating drugs for the treatment or prevention of hearing loss is the limited data available on the distribution and concentration of drugs in the human inner ear. Although small animal models offer some insights into inner ear pharmacokinetics, their smaller organ size and different barrier (round window membrane) permeabilities compared to humans can complicate study interpretation. Therefore, developing a reliable large animal model for inner ear drug delivery is crucial. The inner and middle ear anatomy of domestic pigs closely resembles that of humans, making them promising candidates for studying inner ear pharmacokinetics. However, unlike humans, the anatomical orientation and tortuosity of the porcine external ear canal frustrates local drug delivery to the inner ear. Methods: In this study, we developed a surgical technique to access the tympanic membrane of pigs. To assess hearing pre- and post-surgery, auditory brainstem responses to click and pure tones were measured. Additionally, we performed 3D segmentation of the porcine inner ear images and used this data to simulate the diffusion of dexamethasone within the inner ear through fluid simulation software (FluidSim). Results: We have successfully delivered dexamethasone and dexamethasone sodium phosphate to the porcine inner ear via the intratympanic injection. The recorded auditory brainstem measurements revealed no adverse effects on hearing thresholds attributable to the surgery. We have also simulated the diffusion rates for dexamethasone and dexamethasone sodium phosphate into the porcine inner ear and confirmed the accuracy of the simulations using in-vivo data. Discussion: We have developed and characterized a method for conducting pharmacokinetic studies of the inner ear using pigs. This animal model closely mirrors the size of the human cochlea and the thickness of its barriers. The diffusion time and drug concentrations we reported align closely with the limited data available from human studies. Therefore, we have demonstrated the potential of using pigs as a large animal model for studying inner ear pharmacokinetics.

Reappraisal of duplex criteria to assess significant carotid stenosis with special reference to reports from the North American Symptomatic Carotid Endarterectomy Trial and the European Carotid Surgery Trial

PURPOSE

Duplex examination is today the principal initial method of assessing extracranial carotid or vertebral artery disease. However, varying haemodynamic criteria have been described to categorize the degree of internal carotid artery stenosis, and similarly the degree of stenosis detected with angiography has been assessed with different methods as highlighted in studies performed by the North American Symptomatic Carotid Endarterectomy Trial and the European Carotid Surgery Trial. This study looks at the correlation between two commonly used methods of assessing carotid artery stenosis with duplex criteria and the two methods of angiographic interpretation used in these trials. Duplex parameters are also identified to determine the greater than 70% stenosis group identified as at risk in these studies.

METHODS

A total of 120 carotid bifurcations were studied in patients who underwent both carotid duplex and angiography. Correlations of duplex with angiography were assessed with duplex criteria described by Zwiebel and by Strandness and the angiographic methods used in studies performed by the North American Symptomatic Carotid Endarterectomy Trial and the European Carotid Surgery Trial. Receiver operator curves were constructed from the duplex data for the detection of stenosis greater than 70% based on the angiographic assessment used in the study performed by the North American Symptomatic Carotid Endarterectomy Trial.

RESULTS

The duplex criteria described by Zwiebel and Strandness differed in their accuracy depending on which of the two methods was used to report the angiograms. Zwiebel's criteria agreed more with the angiographic method used in the study performed by the European Carotid Surgery Trial (sensitivity 98%, specificity 81%, accuracy 88%), whereas Strandness' criteria agreed more with the angiographic method used in the study performed by the North American Symptomatic Carotid Endarterectomy Trial (sensitivity 96%, specificity 85%, accuracy 89%). For the detection of a stenosis greater than 70%, a peak systolic velocity greater than 270 cm/sec and end diastolic velocity greater than 110 cm/sec provided a sensitivity of 96%, specificity of 91%, and accuracy of 93%.

CONCLUSIONS

The accuracy of duplex studies compared with angiography in the assessment of extracranial vascular disease depends on the method of angiographic determination of carotid stenosis. Vascular laboratories should validate the duplex criteria they use against a standard method of angiographic assessment of carotid artery stenosis, with special reference to the recently reported studies noting the significance of a stenosis greater than 70% in patients with symptoms.