Motor training promotes both synaptic and intrinsic plasticity of layer V pyramidal neurons in the primary motor cortex

Layer V neurons in the primary motor cortex (M1) are important for motor skill learning. Since pretreatment of either CNQX or APV in rat M1 layer V impaired rotor rod learning, we analysed training-induced synaptic plasticity by whole-cell patch-clamp technique in acute brain slices. Rats trained for 1 day showed a decrease in small inhibitory postsynaptic current (mIPSC) frequency and an increase in the paired-pulse ratio of evoked IPSCs, suggesting a transient decrease in presynaptic GABA release in the early phase. Rats trained for 2 days showed an increase in miniature excitatory postsynaptic current (mEPSC) amplitudes/frequency and elevated AMPA/NMDA ratios, suggesting a long-term strengthening of AMPA receptor-mediated excitatory synapses. Importantly, rotor rod performance in trained rats was correlated with the mean mEPSC amplitude and the frequency obtained from that animal. In current-clamp analysis, 1-day-trained rats transiently decreased the current-induced firing rate, while 2-day-trained rats returned to pre-training levels, suggesting dynamic changes in intrinsic properties. Furthermore, western blot analysis of layer V detected decreased phosphorylation of Ser^408-409 in GABA_A receptor β₃ subunits in 1-day-trained rats, and increased phosphorylation of Ser⁸³¹ in AMPA receptor GluA1 subunits in 2-day-trained rats. Finally, live-imaging analysis of Thy1-YFP transgenic mice showed that the training rapidly recruited a substantial number of spines for long-term plasticity in M1 layer V neurons. Taken together, these results indicate that motor training induces complex and diverse plasticity in M1 layer V pyramidal neurons. KEY POINTS: Here we examined motor training-induced synaptic and intrinsic plasticity of layer V pyramidal neurons in the primary motor cortex. The training reduced presynaptic GABA release in the early phase, but strengthened AMPA receptor-mediated excitatory synapses in the later phase: acquired motor performance after training correlated with the strength of excitatory synapses rather than inhibitory synapses. As to the intrinsic property, the training transiently decreased the firing rate in the early phase, but returned to pre-training levels in the later phase. Western blot analysis detected decreased phosphorylation of Ser^408-409 in GABA_A receptor β₃ subunits in the acute phase, and increased phosphorylation of Ser⁸³¹ in AMPA receptor GluA1 subunits in the later phase. Live-imaging analysis of Thy1-YFP transgenic mice showed rapid and long-term spine plasticity in M1 layer V neurons, suggesting training-induced increases in self-entropy per spine.

Transcriptomic intratumor heterogeneity of breast cancer patient-derived organoids may reflect the unique biological features of the tumor of origin

BACKGROUND

The intratumor heterogeneity (ITH) of cancer cells plays an important role in breast cancer resistance and recurrence. To develop better therapeutic strategies, it is necessary to understand the molecular mechanisms underlying ITH and their functional significance. Patient-derived organoids (PDOs) have recently been utilized in cancer research. They can also be used to study ITH as cancer cell diversity is thought to be maintained within the organoid line. However, no reports investigated intratumor transcriptomic heterogeneity in organoids derived from patients with breast cancer. This study aimed to investigate transcriptomic ITH in breast cancer PDOs.

METHODS

We established PDO lines from ten patients with breast cancer and performed single-cell transcriptomic analysis. First, we clustered cancer cells for each PDO using the Seurat package. Then, we defined and compared the cluster-specific gene signature (ClustGS) corresponding to each cell cluster in each PDO.

RESULTS

Cancer cells were clustered into 3-6 cell populations with distinct cellular states in each PDO line. We identified 38 clusters with ClustGS in 10 PDO lines and used Jaccard similarity index to compare the similarity of these signatures. We found that 29 signatures could be categorized into 7 shared meta-ClustGSs, such as those related to the cell cycle or epithelial-mesenchymal transition, and 9 signatures were unique to single PDO lines. These unique cell populations appeared to represent the characteristics of the original tumors derived from patients.

CONCLUSIONS

We confirmed the existence of transcriptomic ITH in breast cancer PDOs. Some cellular states were commonly observed in multiple PDOs, whereas others were specific to single PDO lines. The combination of these shared and unique cellular states formed the ITH of each PDO.

Learning Promotes Subfield-Specific Synaptic Diversity in Hippocampal CA1 Neurons

The hippocampus is functionally heterogeneous between the dorsal and ventral subfields with left–right asymmetry. To determine the possible location of contextual memory, we performed an inhibitory avoidance task to analyze synaptic plasticity using slice patch-clamp technique. The training bilaterally increased the AMPA/NMDA ratio at dorsal CA3–CA1 synapses, whereas the training did not affect the ratio at ventral CA3–CA1 synapses regardless of the hemisphere. Moreover, sequential recording of miniature excitatory postsynaptic currents and miniature inhibitory postsynaptic currents from the same CA1 neuron clearly showed learning-induced synaptic plasticity. In dorsal CA1 neurons, the training dramatically strengthened both excitatory and inhibitory postsynaptic responses in both hemispheres, whereas the training did not promote the plasticity in either hemisphere in ventral CA1 neurons. Nonstationary fluctuation analysis further revealed that the training bilaterally increased the number of AMPA or GABA_A receptor channels at dorsal CA1 synapses, but not at ventral CA1 synapses, suggesting functional heterogeneity of learning-induced receptor mobility. Finally, the performance clearly impaired by the bilateral microinjection of plasticity blockers in dorsal, but not ventral CA1 subfields, suggesting a crucial role for contextual learning. The quantification of synaptic diversity in specified CA1 subfields may help us to diagnose and evaluate cognitive disorders at the information level.

[A Case of Small Bowel Perforation Caused by Malignant Lymphoma after Methotrexate Therapy for Rheumatoid Arthritis]

A 73-year-old woman had a history of medication, including methotrexate for rheumatoid arthritis, for 5 years. She had chronic epigastralgia for 2 weeks and found to have multiple submucosal tumors on upper gastrointestinal endoscopy in another hospital. She had a strong abdominal pain thereafter and diagnosed as having gastrointestinal perforation on the basis of CT scans. Abdominal examination revealed disseminated peritonitis, and emergency laparoscopic surgery was performed on the day of admission. A 1 cm perforation of the ileum was identified, and a 5 cm mass of the mesentery near the perforation was also identified. Small bowel partial resection, including both lesions, was performed. From the intraoperative findings, methotrexate-associated lymphoproliferative disorders(MTX-LPD)was suspected, and methotrexate was discontinued after the surgery. At a later date, the pathological result from both the surgical specimen and upper gastrointestinal endoscopy was diffuse large B cell lymphoma(DLBCL). CT scan, PET-CT scan, and upper gastrointestinal endoscopy were performed 1-2 months after surgery, and no tumor was identified. Currently, 6 months after the surgery, the patient is still alive without any progression of the lymphoma.

[Trastuzumab Combination Chemotherapy Followed by R0 Resection for Locally Advanced Human Epidermal Growth Factor Receptor 2-Positive Gastric Cancer-A Case Report]

A man in the 60s visited our hospital with the complaints of epigastralgia and weight loss. Following an investigation, he was diagnosed with human epidermal growth factor receptor 2(HER2)-positive gastric cancer with invasion to the pancreas (T4b[pancreas], N2, M0, Stage ⅣA[Union for International Cancer Control 8th edition]). Preoperatively, he was administered a chemotherapeutic regimen of S-1 and cisplatin plus trastuzumab. After 2 courses of chemotherapy, computed tomography revealed invasion to the abdominal wall and pyloric stenosis; however, invasion to the pancreas was obscured, and the lymph node metastases had shrunk. He underwent laparoscopic gastro-jejunostomy. After 4 courses of chemotherapy, his condition was considered stable. A laparoscopic distal gastrectomy was performed together with resection of the abdominal wall invasion. The pathological stage was pT4b(abdominal wall), pN0, M0, Stage ⅢA, and R0 resection was achieved. The patient was administered 4 courses of adjuvant capecitabine plus oxaliplatin therapy and 4 courses of capecitabine monotherapy. He has been followed-up for 1.5 years since the curative resection and has not developed recurrences. This case suggests the usefulness of multimodal therapy for locally advanced gastric cancer.

[A Case of Complete Response to Computed Tomography-Guided Celiac Plexus Neurolysis of Pain Associated with Postoperative Recurrence of Colon Cancer]

The patient was a man in his 40s, who had undergone laparoscopic ileocecal resection with lymph node dissection(D3)for cecal cancer in January 2012. Histopathological examination of the resected specimens had revealed StageⅡ primary tumor with subserosal invasion and positive metastasis in 1-3 regional lymph nodes(pT2[SS]n1[+]). The pathological stage was Ⅲa(fStage Ⅲa), and the tumor showed RAS gene mutation. The patient was administered 5 cycles of postoperative adjuvant chemotherapy with oral tegafur/uracil(UFT)in combination with calcium folinate(UZEL). Abdominal computed tomography( CT)performed 1.5 years postoperatively revealed liver metastasis, and a laparoscopic partial hepatectomy was performed in August 2015. In addition, a node in the greater omentum, located in the inferior surface of the liver, was also resected. Histopathological examination of the resected specimens revealed peritoneal metastasis, based on the identification of the same type of adenocarcinoma as the colon cancer. The patient was given 8 cycles of adjuvant chemotherapy with capecitabine and oxaliplatin(CapeOX). Then, he presented with colonic ileus, caused by recurrent dissemination, and underwent a laparoscopic transverse colectomy in October 2015. Multiple perineal disseminations were found intraoperatively, and chemotherapy was initiated with irinotecan plus tegafur/gimeracil/oteracil(S-1)plus bevacizumab(IRIS/BV)for the recurrent and unresectable disease. After 27 cycles of this regimen, lung metastasis was detected; in addition, progression of the para-aortic node metastasis around the celiac plexus was also observed, and the patient was considered as having pro- gressive disease(PD). Treatment with trifluridine/tipiracil(TAS102)was started in September 2017. Prior to the initiation of this regimen, the dose of opioid rescue medication previously started for back and abdominal pain was rapidly increased. Accordingly, the base dose was increased, but the pain could not be controlled, and the major pain was consistently located along the area of innervation in the celiac plexus. Therefore, celiac plexus neurolysis(CPN)was performed as a local therapy. A CT-guided injection technique was used to administer urografin, bupivacaine, and absolute ethanol to complete the procedure. The patient was discharged without major complications, and the base opioid dose was gradually reduced. Since the patient did not require any rescue medication during daytime on some days, the reduction of the base opioid dose was significantly effective in improving the patient's quality of life(QOL). In patients with pain possibly caused by metastasis to the para-aortic nodes, this local therapy technique may be considered.