SUMMARYVentral tegmental area (VTA) glutamate neurons are important components of reward circuitry, but whether they are subject to cholinergic modulation is unknown. To study this, we used molecular, physiological, and photostimulation techniques to examine nicotinic acetylcholine receptors (nAChRs) in VTA glutamate neurons. Cells in the medial VTA, where glutamate neurons are enriched, are responsive to acetylcholine (ACh) released from cholinergic axons. VTA VGLUT2+ neurons express mRNA and protein subunits known to comprise heteromeric nAChRs. Electrophysiology, coupled with two-photon microscopy and laser flash photolysis of photoactivatable nicotine, was used to demonstrate nAChR functional activity in the somatodendritic subcellular compartment of VTA VGLUT2+ neurons. Finally, optogenetic isolation of intrinsic VTA glutamatergic microcircuits along with gene-editing techniques demonstrated that nicotine potently modulates excitatory transmission within the VTA via heteromeric nAChRs. These results indicate that VTA glutamate neurons are modulated by cholinergic mechanisms and participate in the cascade of physiological responses to nicotine exposure.

Antagonism of nicotinic acetylcholine receptors (nAChRs) in the medial habenula (MHb) or interpeduncular nucleus (IPN) triggerswithdrawal-like behaviors in mice chronically exposed to nicotine, implying that nicotine dependence involves the sensitization of nicotinic signaling. Identification of receptor and/or neurophysiological mechanisms underlying this sensitization is important, as it could promote novel therapeutic strategies to reduce tobacco use. Using an approach involving photoactivatable nicotine, we previously demonstrated that chronic nicotine (cNIC) potently enhances nAChR function in dendrites of MHb neurons. However, whether cNIC modulates downstream components of the habenulo-interpeduncular (Hb-IP) circuit is unknown. In this study, cNIC-mediated changes to Hb-IP nAChR function were examined in mouse (male and female) brain slices using molecular, electrophysiological, and optical techniques. cNIC enhanced action potential firing and modified spike waveform characteristics in MHb neurons. Nicotine uncaging revealed nAChR functional enhancement by cNIC on proximal axonal membranes. Similarly, nAChR-driven glutamate release from MHb axons was enhanced by cNIC. In IPN, the target structure of MHb axons, neuronal morphology, and nAChR expression is complex, with stronger nAChR function in the rostral subnucleus [rostral IPN (IPR)]. As in MHb, cNIC induced strong upregulation of nAChR function in IPN neurons. This, coupled with cNIC-enhanced nicotine-stimulated glutamate release, was associated with stronger depolarization responses to brief (1 ms) nicotine uncaging adjacent to IPR neurons. Together, these results indicate that chronic exposure to nicotine dramatically alters nicotinic cholinergic signaling and cell excitability in Hb-IP circuits, a key pathway involved in nicotine dependence.This study uncovers several neuropharmacological alterations following chronic exposure to nicotine in a key brain circuit involved in nicotine dependence. These results suggest that smokers or regular users of electronic nicotine delivery systems (i.e., "e-cigarettes") likely undergo sensitization of cholinergic circuitry in the Hb-IP system. Reducing the activity of Hb-IP nAChRs, either volitionally during smoking cessation or inadvertently via receptor desensitization during nicotine intake, may be a key trigger of withdrawal in nicotine dependence. Escalation of nicotine intake in smokers, or tolerance, may involve stimulation of these sensitized cholinergic pathways. Smoking cessation therapeutics are only marginally effective, and by identifying cellular/ receptor mechanisms of nicotine dependence, our results take a step toward improved therapeutic approaches for this disorder. Arvin et al. • Habenulo-Interpeduncular Circuits Modified by Nicotine

We describe the incorporation of β-cyclodextrin into a model CG-scaffold under development for musculoskeletal tissue engineering applications. We show β-cyclodextrin modified scaffolds promote the sequestration of soluble TGF-β1 and BMP-2 via guest-host interactions, leading to extended retention and release. Further, β-cyclodextrin modified CG scaffolds promote TGF-β1 or BMP-2 specific Smad signaling pathway activation associated with divergent osseous versus chondrogenic differentiation pathways in mesenchymal stem cells.

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Upper extremity reconstruction may pose clinical challenges for surgeons due to the often-critical, complex functional demands of the damaged and/or missing structures. The advent of vascularized bone grafts (VBGs) has aided in reconstruction of upper extremity (UE) defects due to their superior regenerative properties compared with nonvascularized bone grafts, ability to reconstruct large bony defects, and multiple donor site options. VBGs may be pedicled or free transfers and have the potential for composite tissue transfers when bone and soft tissue are needed. This article provides a comprehensive up-to-date review of VBGs, the commonly reported donor sites, and their indications for the treatment of specific UE defects.

Brain metastases are a leading cause of death in patients with breast cancer. The lack of clinical trials and the presence of the blood–brain barrier limit therapeutic options. Furthermore, overexpression of the human epidermal growth factor receptor 2 (HER2) increases the incidence of breast cancer brain metastases (BCBM). HER2-targeting agents, such as the monoclonal antibodies trastuzumab and pertuzumab, improved outcomes in patients with breast cancer and extracranial metastases. However, continued BCBM progression in breast cancer patients highlighted the need for novel and effective targeted therapies against intracranial metastases. In this study, we engineered the highly migratory and brain tumor tropic human neural stem cells (NSCs) LM008 to continuously secrete high amounts of functional, stable, full-length antibodies against HER2 (anti-HER2Ab) without compromising the stemness of LM008 cells. The secreted anti-HER2Ab impaired tumor cell proliferation in vitro in HER2+ BCBM cells by inhibiting the PI3K-Akt signaling pathway and resulted in a significant benefit when injected in intracranial xenograft models. In addition, dual HER2 blockade using anti-HER2Ab LM008 NSCs and the tyrosine kinase inhibitor tucatinib significantly improved the survival of mice in a clinically relevant model of multiple HER2+ BCBM. These findings provide compelling evidence for the use of HER2Ab-secreting LM008 NSCs in combination with tucatinib as a promising therapeutic regimen for patients with HER2+ BCBM.

Ventral tegmental area (VTA) glutamate neurons are important components of brain reward circuitry, but whether they are subject to cholinergic modulation is unknown. To study this, we used an array of molecular, physiological, and photostimulation techniques to examine nicotinic acetylcholine receptors (nAChRs) in VTA glutamate neurons. VTA neurons positive for the vesicular glutamate transporter 2 (VGLUT2+) are responsive to acetylcholine (ACh) released from mesopontine cholinergic axons. VTA VGLUT2+ neurons express mRNA and protein subunits known to comprise typical heteromeric nAChRs. Electrophysiology, coupled with 2-photon microscopy and laser flash photolysis of a photoactivatable nicotine probe, was used to demonstrate nAChR functional activity in the somatodendritic subcellular compartment of VTA VGLUT2+ neurons. Finally, optogenetic isolation of intrinsic VTA glutamatergic microcircuits demonstrated that nicotine potently modulates excitatory transmission within the VTA. These results indicate that VTA glutamate neurons are modulated by cholinergic mechanisms and participate in the cascade of physiological responses to nicotine exposure.

Lack of surgical access severely harms countless populations in many low- and middle-income countries (LMICs). Many types of surgery could be fulfilled by the plastic surgeon, as populations in these areas often experience trauma, burns, cleft lip and palate, and other relevant medical issues. Plastic surgeons continue to contribute significant time and energy to global health, primarily by participating in short mission trips intended to provide many surgeries in a short time frame. These trips, while cost-effective for lack of long-term commitments, are not sustainable as they require high initial costs, often neglect to educate local physicians, and can interfere with regional systems. Education of local plastic surgeons is a key step toward creating sustainable plastic surgery interventions worldwide. Virtual platforms have grown popular and effective—particularly due to the coronavirus disease 2019 pandemic—and have shown to be beneficial in the field of plastic surgery for both diagnosis and teaching. However, there remains a large potential to create more extensive and effective virtual platforms in high-income nations geared to educate plastic surgeons in LMICs to lower costs and more sustainably provide capacity to physicians in low access areas of the world.