Deconstruction of Polymers through Olefin Metathesis.

The consumption of synthetic polymers has ballooned; so has the amount of post-consumer waste generated. The current polymer economy, however, is largely linear with most of the post-consumer waste being either landfilled or incinerated. The lack of recycling, together with the sizable carbon footprint of the polymer industry, has led to major negative environmental impacts. Over the past few years, chemical recycling technologies have gained significant traction as a possible technological route to tackle these challenges. In this regard, olefin metathesis, with its versatility and ease of operation, has emerged as an attractive tool. Here, we discuss the developments in olefin-metathesis-based chemical recycling technologies, including the development of new materials and the application of olefin metathesis to the recycling of commercial materials. We delve into structure-reactivity relationships in the context of polymerization-depolymerization behavior, how experimental conditions influence deconstruction outcomes, and the reaction pathways underlying these approaches. We also look at the current hurdles in adopting these technologies and relevant future directions for the field.

[Progress of electrical stimulation to promote peripheral nerve regeneration].

This study reviews the latest progress on the research of electrical stimulation（ES） in peripheral nerve regeneration, summarizes the parameters in preclinical experiments and discusses the effect on nerve regeneration. A detailed description is given in the study of conditioning electrical stimulation and nerve conduit scaffolding technology combined with ES, which have been hotly researched in recent years.

[Analysis of the effect of different facial nerve managements applied to tumor resection in the jugular foramen region].

Objective:To summarize the results of different facial nerve management modalities applied to tumor resection in the jugular foramen region. Methods:The clinical data of 54 patients with tumors in the jugular foramen region who underwent surgery from January 2015 to March 2023 were retrospectively analyzed: 18 males and 36 females; Age ranges from 21 to 67 years, with an average age of 44.4 years; and median follow-up time: 12 months. The House-Brackmann（HB） grading system was applied to assess the patients' facial nerve function before surgery, 1-2 weeks after surgery and at the final follow-up （HBⅠ-Ⅱ grade for good function）: 42 cases with preoperative HB grades Ⅰ-Ⅱ; partial facial nerve transposition（9 cases）, complete facial nerve transposition（28 cases）, and facial nerve excision and re-construction（17 cases） were used, respectively（stage Ⅰor Ⅱ）. Relevant factors affecting postoperative facial nerve function were analyzed. Results:Postoperative pathology confirmed 39 cases of paraganglioma, 9 cases of nerve sheath tumor, 3 cases of meningioma, and 1 case each of fibromucinous sarcoma, chondrosarcoma, and intravascular myofibroma. Facial nerve function after partial facial nerve transposition was HB grade Ⅰ-Ⅱ in 89%（8/9）; after complete facial nerve transposition was HB grade Ⅰ-Ⅱ in 86%（24/28） in 28 cases; after facial nerve severance and reconstruction was HB grade Ⅰ-Ⅱ in 2/7（Stage Ⅰ） and 0/3（Stage Ⅱ）, respectively. Tumor size and surgical approach were correlated with postoperative facial nerve function in patients with facial nerve transposition（P<0.05）. There was no statistically significant difference in facial nerve function after complete and partial facial nerve transposition（P>0.05）. Conclusion:Intraoperative stretching of the facial nerve may be an important factor affecting facial nerve function during surgical treatment of tumors in the jugular venous foramen region; for patients with facial nerve dissection, facial nerve reconstruction should be adopted according to the situation, aiming at the recovery of facial nerve function.

[Application of the follower arm endoscope holder in type i tympanoplasty].

Objective:To investigate the surgical outcomes and safety of the follower arm endoscope holder in assisting type Ⅰ tympanoplasty. Methods:The clinical data of 16 patients who underwent type Ⅰ tympanoplasty at the Department of Otorhinolaryngology, Peking Union Medical College Hospital, from November 2022 to September 2023 were retrospectively analyzed, among which 8 cases were operated by traditional otoscopy and 8 cases were operated by supported endoscopy.The surgical procedure was analyzed and the completion of supported endoscopic operation was observed, while the duration of the operation, the time consumed by the main steps, the frequency of wiping the lenses, the perioperative complications, and the improvement of the postoperative hearing were recorded and statistically analyzed. Results:Supporting endoscopic technology achieved real-time suction of bleeding, simultaneous traction and separation of tissues, precise removal of calcified spots on the inner side of the eardrum, trimming of the external auditory canal flap, stable separation of the handle of the malleus and the eardrum, and tensioned repositioning of the skin-cartilage flap. The average duration of surgery, time for external auditory canal flap preparation, and time for repositioning the skin-cartilage flap were reduced in the supporting endoscopic surgery group compared to the control group. The average lens wiping frequency was significantly lower in the supporting endoscopic surgery group compared to the control group. There was no statistically significant difference in postoperative hearing improvement between the two groups, and no infections or the need for secondary surgery due to eardrum re-perforation occurred postoperatively. Conclusion:Supported endoscopy technology realizes the need for endoscopic two-handed operation and convenient switching between one and two hands, accomplishes many operations that cannot be done by traditional endoscopic surgery, solves the problems of previous intraoperative one-handed operation and image instability, shortens the average operation time compared with traditional otoscopic surgery, and decreases the frequency of intraoperative wiping of the lens significantly compared with traditional otoscopic surgery, which is potentially worthwhile in terms of shortening the learning curve.

Mechanisms of Resistance to Tyrosine Kinase Inhibitors in ROS1 Fusion-Positive Nonsmall Cell Lung Cancer.

BACKGROUND: ROS1 fusion-positive (ROS1+) nonsmall cell lung cancer (NSCLC) patients are highly sensitive to tyrosine kinase inhibitor (TKI) treatments. However, acquired TKI resistance remains the major hurdle preventing patients from experiencing prolonged benefits. METHODS: 107 advanced or metastatic ROS1+ NSCLC patients who progressed on crizotinib and lorlatinib were recruited. Tissue and plasma samples were collected at baseline (N = 50), postcrizotinib (N = 91), and postlorlatinib (N = 21), which were all subject to the 139-gene targeted next-generation DNA sequencing. Molecular dynamics modeling was performed to investigate the effects of ROS1 mutations on binding to different TKIs. RESULTS: In patients with postcrizotinib and postlorlatinib samples, an accumulation of on- and off-target resistance alterations after multiple TKI treatments was observed. ROS1 G2032R and MET amplification were the most common on-target and off-target alterations, respectively. Patients with CD74-ROS1 and SLC34A2-ROS1 had longer progression-free survival (PFS) (P < 0.001) and higher rates of resistance mutations (on-target, P = 0.001; off-target, P = 0.077) than other ROS1 fusion variants following crizotinib treatment. Ten distinct on-target resistance mutations were detected after TKI therapies, of which 4 were previously unreported (ROS1 L2010M, G1957A, D1988N, L1982V). Molecular dynamics simulations showed that all 4 mutations were refractory to crizotinib, while G1957A, D1988N, and L1982V were potentially sensitive to lorlatinib and entrectinib. CONCLUSIONS: This study provided a comprehensive portrait of TKI-resistance mechanisms in ROS1+ NSCLC patients. Using in silico simulations of TKI activity, novel secondary mutations that may confer TKI resistance were identified and may support clinical therapeutic decision-making.

Research progress of procyanidins in repairing cartilage injury after anterior cruciate ligament tear.

Anterior cruciate ligament (ACL) tear is a common sports-related injury, and cartilage injury always emerges as a serious complication following ACL tear, significantly impacting the physical and psychological well-being of affected individuals. Over the years, efforts have been directed toward finding strategies to repair cartilage injury after ACL tear. In recent times, procyanidins, known for their anti-inflammatory and antioxidant properties, have emerged as potential key players in addressing this concern. This article focuses on summarizing the research progress of procyanidins in repairing cartilage injury after ACL tear. It covers the roles, mechanisms, and clinical significance of procyanidins in repairing cartilage injury following ACL tear and explores the future prospects of procyanidins in this domain. This review provides novel insights and hope for the repair of cartilage injury following ACL tear.

Diapause-like Drug-Tolerant Persister State: The Key to Nirvana Rebirth.

Cancer is one of the leading causes of death in the world. Various drugs have been developed to eliminate it but to no avail because a tumor can go into dormancy to avoid therapy. In the past few decades, tumor dormancy has become a popular topic in cancer therapy. Recently, there has been an important breakthrough in the study of tumor dormancy. That is, cancer cells can enter a reversible drug-tolerant persister (DTP) state to avoid therapy, but no exact mechanism has been found. The study of the link between the DTP state and diapause seems to provide an opportunity for a correct understanding of the mechanism of the DTP state. Completely treating cancer and avoiding dormancy by targeting the expression of key genes in diapause are possible. This review delves into the characteristics of the DTP state and its connection with embryonic diapause, and possible treatment strategies are summarized. The authors believe that this review will promote the development of cancer therapy.

The role of vitamin D through SphK1/S1P in the regulation of MS progression.

Sphingosine-1-phosphate (S1P) is biologically active lipid, leading to neuroinflammation and macrophage invasion in central nervous system, plays an important role in the development of multiple sclerosis (MS) model in experimental allergic encephalomyelitis (EAE) rats. Vitamin D is observed to be a key factor in regulating cell S1P levels. We detected vitamin D can alleviate the symptoms of EAE rats, but the exact mechanism is unclear. In PC12 cells, vitamin D can reverse S1P-induced cell death, but the signaling pathway unclear. This study was aimed to investigate S1P regulation mechanism or signaling pathway mediated by vitamin D in EAE and PC12 model. In our experiments, S1P and Sphingosine kinase type 1 (SphK1) mRNA and protein expression in EAE rats group, control group, vitamin D feeding group were detected by HPLC, ELISA, RT-PCR and western blot. PC12 cell death was detected by Propidium (PI) staining. VDR plasmid overexpression and RNA interference, immunofluorescence, real-time cell analysis, protein immunoblotting was used to detect SphK1 transcriptional regulation, cell-substrate attachment quality, the signaling pathway of cell apoptosis and inflammation related gene expression (Bax/Bcl-2, Casepase-3, Il-6, TGF-ß, TNF-α). Our study showed vitamin D can reverse the elevation of S1P level in EAE rats, reduce the severity and shorten the course of EAE. 1,25-(OH) 2D3 coupled with vitamin D receptor (VDR) inhibited SphK1 transcription. 1,25-(OH)2D3 significantly reduced PC12 cell death rate induced by S1P, in addition improved the cell substrate attachment quality. 1,25-(OH) 2D3 can block S1P-induced p-ERK activation and PI3K /Akt signaling pathway reduced Il-6, TGF-ß, TNF-α cytokine release and Bax/Bcl-2, Casepase-3 apoptosis protein expression. On the other hand, immunofluorescence staining showed 1,25-(OH) 2D3 can increase the expression of neuronal perinuclear protein MAP2 in PC12 cells probably protect nerve cells further. In summary, the ameliorative effect of vitamin D was derived from its ability to reduce S1P levels, provides an idea for vitamin D as a combination therapy for disease.

Vertical tearing of subducting plates controlled by geometry and rheology of oceanic plates.

Lateral non-uniform subduction is impacted by continuous plate segmentation owing to vertical tearing of the subducting plate. However, the dynamics and physical controls of vertical tearing remain controversial. Here, we employed 3D numerical models to investigate the effects of trench geometry (offset by a transform boundary) and plate rheology (plate age and the magnitude of brittle/plastic strain weakening) on the evolution of shear stress-controlled vertical tearing within a homogenous subducting oceanic plate. Numerical results suggest that the trench offset geometry could result in self-sustained vertical tearing as a narrow shear zone within the intact subducting oceanic plate, and that this process of tearing could operate throughout the entire subduction process. Further, the critical trench offset length for the maturation of vertical tearing is impacted by plate rheology. Comparison between numerical modelling results and natural observations suggests that vertical tearing attributed to trench offset geometry is broadly developed in modern subduction and collision systems worldwide.

Reconciling patterns of long-term topographic growth with coseismic uplift by synchronous duplex thrusting.

How long-term changes in surface topography relate to coseismic uplift is key to understanding the creation of high elevations along active mountain fronts, and remains hotly debated. Here we investigate this link by modeling the development of growth strata and the folding of river terraces above the Pishan duplex system in the southern Tarim Basin. We show that synchronous duplex thrusting of two neighboring faults with varying slip rates, associated with in-sequence propagation of the Pishan thrust system, is required to explain the presence of opposite-dipping panels of growth strata on the duplex front, and basinward migration of terrace fold crests. Importantly, this process of synchronous thrusting within the duplex reconciles the discrepancy between the deformation of terrace folds at the 10-1-100 million-year timescale and the maximum coseismic uplift of the 2015 Mw 6.4 Pishan earthquake on the frontal thrust. These results suggest that topography mismatch at different time scales can reflect the long-term kinematic evolution of fault systems. Thus, our study highlights the importance of characterizing complex subsurface fault kinematics for studying topographic growth, and motivates rethinking of the mountain building process in worldwide active fold-and-thrust belts, from short-term to long-term timescales.

Ca substitution improves the catalytic activity of perovskite LaCoO3 toward toluene: comprehension of electronic structure alteration.

For perovskite La1-xCaxCoO3 (Ca-x, x = 0-0.3), Ca-0.2 with the closest O p band center to the Fermi level, displays the best catalytic activity for toluene oxidation. The O p band center determines the reducibility and active oxygen content. This finding is beneficial for the design of highly active perovskite catalysts.

Utilizing metagenomic next-generation sequencing for diagnosis and lung microbiome probing of pediatric pneumonia through bronchoalveolar lavage fluid in pediatric intensive care unit: results from a large real-world cohort.

Background: Metagenomic next-generation sequencing (mNGS) is a powerful method for pathogen detection in various infections. In this study, we assessed the value of mNGS in the pathogen diagnosis and microbiome analysis of pneumonia in pediatric intensive care units (PICU) using bronchoalveolar lavage fluid (BALF) samples. Methods: A total of 104 pediatric patients with pneumonia who were admitted into PICU between June 2018 and February 2020 were retrospectively enrolled. Among them, 101 subjects who had intact clinical information were subject to parallel comparison of mNGS and conventional microbiological tests (CMTs) for pathogen detection. The performance was also evaluated and compared between BALF-mNGS and BALF-culture methods. Moreover, the diversity and structure of all 104 patients' lung BALF microbiomes were explored using the mNGS data. Results: Combining the findings of mNGS and CMTs, 94.06% (95/101) pneumonia cases showed evidence of causative pathogenic infections, including 79.21% (80/101) mixed and 14.85% (15/101) single infections. Regarding the pathogenesis of pneumonia in the PICU, the fungal detection rates were significantly higher in patients with immunodeficiency (55.56% vs. 25.30%, P =0.025) and comorbidities (40.30% vs. 11.76%, P=0.007). There were no significant differences in the α-diversity either between patients with CAP and HAP or between patients with and without immunodeficiency. Regarding the diagnostic performance, the detection rate of DNA-based BALF-mNGS was slightly higher than that of the BALF-culture although statistically insignificant (81.82% vs.77.92%, P=0.677) and was comparable to CMTs (81.82% vs. 89.61%, P=0.211). The overall sensitivity of DNA-based mNGS was 85.14% (95% confidence interval [CI]: 74.96%-92.34%). The detection rate of RNA-based BALF-mNGS was the same with CMTs (80.00% vs 80.00%, P>0.999) and higher than BALF-culture (80.00% vs 52.00%, P=0.045), with a sensitivity of 90.91% (95%CI: 70.84%-98.88%). Conclusions: mNGS is valuable in the etiological diagnosis of pneumonia, especially in fungal infections, and can reveal pulmonary microecological characteristics. For pneumonia patients in PICU, the mNGS should be implemented early and complementary to CMTs.

A Hierarchical Motion Planning Method for Mobile Manipulator.

This paper focuses on motion planning for mobile manipulators, which includes planning for both the mobile base and the manipulator. A hierarchical motion planner is proposed that allows the manipulator to change its configuration autonomously in real time as needed. The planner has two levels: global planning for the mobile base in two dimensions and local planning for both the mobile base and the manipulator in three dimensions. The planner first generates a path for the mobile base using an optimized A* algorithm. As the mobile base moves along the path with the manipulator configuration unchanged, potential collisions between the manipulator and the environment are checked using the environment data obtained from the on-board sensors. If the current manipulator configuration is in a potential collision, a new manipulator configuration is searched. A sampling-based heuristic algorithm is used to effectively find a collision-free configuration for the manipulator. The experimental results in simulation environments proved that our heuristic sampling-based algorithm outperforms the conservative random sampling-based method in terms of computation time, percentage of successful attempts, and the quality of the generated configuration. Compared with traditional methods, our motion planning method could deal with 3D obstacles, avoid large memory requirements, and does not require a long time to generate a global plan.

Immune microenvironment analysis and novel biomarkers of early-stage lung adenocarcinoma evolution.

Background: Lung cancer is the deadliest and most diagnosed type of cancer worldwide. The 5-year survival rate of lung adenocarcinoma (LUAD) dropped significantly when tumor stages advanced. Patients who received surgically resecting at the pre-invasive stage had a 5-year survival rate of nearly 100%. However, the study on the differences in gene expression profiles and immune microenvironment among pre-invasive LUAD patients is still lacking. Methods: In this study, the gene expression profiles of three pre-invasive LUAD stages were compared using the RNA-sequencing data of 10 adenocarcinoma in situ (AIS) samples, 12 minimally invasive adenocarcinoma (MIA) samples, and 10 invasive adenocarcinoma (IAC) samples. Results: The high expression levels of PTGFRN (Hazard Ratio [HR] = 1.45; 95% Confidence Interval [CI]: 1.08-1.94; log-rank P = 0.013) and SPP1 (HR = 1.44; 95% CI: 1.07-1.93; log-rank P = 0.015) were identified to be associated with LUAD prognosis. Moreover, the early LUAD invasion was accompanied by the enhancement of antigen presentation ability, reflected by the increase of myeloid dendritic cells infiltration rate (Cuzick test P < 0.01) and the upregulation of seven important genes participating in the antigen presentation, including HLA-A (Cuzick test P = 0.03), MICA (Cuzick test P = 0.01), MICB (Cuzick test P = 0.01), HLA-DPA1 (Cuzick test P = 0.04), HLA-DQA2 (Cuzick test P < 0.01), HLA-DQB1 (Cuzick test P = 0.03), and HLA-DQB2 (Cuzick test P < 0.01). However, the tumor-killing ability of the immune system was inhibited during this process, as there were no rising cytotoxic T cell activity (Cuzick test P = 0.20) and no increasing expression in genes encoding cytotoxic proteins. Conclusion: In all, our research elucidated the changes in the immune microenvironment during early-stage LUAD evolution and may provide a theoretical basis for developing novel early-stage lung cancer therapeutic targets.

The differences in immune features and genomic profiling between squamous cell carcinoma and adenocarcinoma - A multi-center study in Chinese patients with uterine cervical cancer.

BACKGROUND: Squamous cell carcinoma (SCC) and adenocarcinoma (AC) of the uterine cervix have distinct biological behaviors and different treatment responses. Studies on immune features and genomic profiling of these two pathologic types were limited and mainly focused on small patient cohorts. METHODS: From 2014 to 2021, 336 (254 SCC vs. 82 AC) cervical cancer patients who were diagnosed/treated in 7 medical centers in China were enrolled in the study. Next-generation sequencing of 425 cancer-relevant genes was performed on tumor tissues and liquid biopsies. Somatic alterations and immune response-related biomarkers were analyzed. Patient prognosis and immune infiltration were analyzed using data from The Cancer Genome Atlas (TCGA). RESULTS: AC tended to have more immunotherapy resistance-related STK11 alterations (P = 0.039), a higher proportion of microsatellite instability (P = 0.21), and more actionable mutations (P = 0.161). In contrast, higher tumor mutational burdens (TMB; P = 0.01), a higher proportion of TMB-high patients (P = 0.016), and more PD-L1-high patients (P = 0.0013) were observed in SCC. Multiple genetic alterations and aberrant signaling pathways were specifically enriched in AC (e.g., TP53, KRAS, ERBB2, and ARID1A alterations) or SCC (e.g., PIK3CA, FBXW7, EP300, and BAP1 mutations). Notably, AC-enriched genetic changes were significantly associated with decreased infiltrations of various B cells, T cells, and dendritic cells, whereas SCC-associated molecular features tended to be associated with increased CD4+ T cell infiltrations. CONCLUSIONS: This was the first multi-center study revealing the immunologic and genomic features between SCC and AC in Chinese patients with cervical cancer. Our findings have illustrated the difference in genetic profiles of those two cervical cancer subtypes, which may suggest the possibility of differential treatment regimens, with better immunotherapy efficacy in SCC and targeted therapy options more favorable in AC.

Pathological characteristics and immune microenvironment of SMARCA4-deficient undifferentiated uterine sarcoma.

SMARCA4-deficient undifferentiated uterine sarcoma (SDUS) is a highly invasive single-gene malignant tumor caused by mutations in the SMARCA4 gene. SDUS has a poor prognosis, with no established treatment strategy at present. Further, there is a lack of relevant research on the role of the immune microenvironment in SDUS worldwide. Here, we report a case of SDUS that was diagnosed and analysed using morphological, immunohistochemical, and molecular detection techniques, along with the analysis of the immune microenvironment. By immunohistochemistry, the tumor cells showed retained INI-1 expression, focal CD10 expression, and loss of BRG1, CK-pan, synaptophysin, desmin, and ER expression. Further, some of the immune cells expressing CD3 and CD8 had infiltrated into the SDUS, but no PD-L1 expression was detected. The multiple immunofluorescent staining results showed that a proportion of the immune cells and SDUS cells expressed CD8/CD68/PD-1/PD-L1. Therefore, our report will help in the diagnostic awareness of SDUS.

Comprehensive characterization of FBXW7 mutational and clinicopathological profiles in human colorectal cancers.

Background: FBXW7 is recognized as a critical tumor suppressor gene and a component of the ubiquitin-proteasome system, mediating the degradation of multiple oncogenic proteins, including c-MYC, Cyclin E, c-Jun, Notch, p53. Around 16% of colorectal cancer (CRC) patients carried FBXW7 somatic mutations, while a comprehensive characterization of FBXW7 somatic mutations in CRC is still lacking. Methods: Colorectal cancer patients with tumor samples and matching white blood cell samples in the past five years were screened and DNA sequenced. DNA sequencing data of MSK MetTropism cohort and RNA sequencing data of TCGA COAD cohort were analyzed. Results: We discovered that the FBXW7 mutations were associated with higher tumor mutation burden (TMB), higher microsatellite instability (MSI) score, and lower chromosomal instability (CIN) score. Patients with FBXW7 mutations showed better overall survival (HR: 0.67; 95%CI: 0.55-0.80, P < 0.001). However, patients with FBXW7 R465C mutation displayed worse overall survival in multi-variate cox analysis when compared with patients carrying other FBXW7 mutations (HR: 1.6; 95%CI: 1.13-3.1, P = 0.015), and with all other patients (HR: 1.87; 95%CI: 0.99-2.5, P = 0.053). Moreover, in MSI patients, the FBXW7 mutated group showed higher M1 macrophage, CD8+ T cell, and regulatory T cell (Tregs) infiltration rates, and significant enrichment of multiple immune-related gene sets, including interferon-gamma response, interferon-alpha response, IL6 JAK STAT3 signaling, p53 pathway. Conclusion: This analysis comprehensively identified FBXW7 alterations in colorectal cancer patients and uncovered the molecular, clinicopathological, and immune-related patterns of FBXW7-altered CRC patients.

Best-Worst Scaling Survey of Inpatients' Preferences in Medical Decision-Making Participation in China.

This study assesses inpatients' preferences for participating in medical decision-making and determines the factors' rankings in order of importance and whether they vary for respondents with different characteristics. Case 1 best-worst scaling (BWS) was used for the study design. Thirteen attributes influencing inpatient medical decision-making participation were identified based on a literature review and interview results. A balanced incomplete block design was used to form choice sets for the BWS questionnaire for a cross-sectional study examining inpatients' preferences for participating in medical decision-making. Based on results from 814 inpatient participants, the three most important factors influencing inpatients' medical decision-making participation were inpatients' trust in physicians, physicians' professional expertise, and physicians' attitudes. The mixed logit model results reflect the significant heterogeneity in respondents' preferences for shared decision-making. To facilitate resource allocation, improve the physician-patient relationship, and encourage patient decision-making participation more actively and effectively, decision-makers should emphasize patients' trust, enhance physicians' ability to diagnose and treat diseases, and improve their attitudes toward providing care and communication from the perspectives of patients, physicians, and the social environment. Further research is needed on the heterogeneity of patients' preferences for participating in medical decision-making and how to improve patient participation.

Mechanochemically accessing a challenging-to-synthesize depolymerizable polymer.

Polymers with low ceiling temperatures (Tc) are highly desirable as they can depolymerize under mild conditions, but they typically suffer from demanding synthetic conditions and poor stability. We envision that this challenge can be addressed by developing high-Tc polymers that can be converted into low-Tc polymers on demand. Here, we demonstrate the mechanochemical generation of a low-Tc polymer, poly(2,5-dihydrofuran) (PDHF), from an unsaturated polyether that contains cyclobutane-fused THF in each repeat unit. Upon mechanically induced cycloreversion of cyclobutane, each repeat unit generates three repeat units of PDHF. The resulting PDHF completely depolymerizes into 2,5-dihydrofuran in the presence of a ruthenium catalyst. The mechanochemical generation of the otherwise difficult-to-synthesize PDHF highlights the power of polymer mechanochemistry in accessing elusive structures. The concept of mechanochemically regulating the Tc of polymers can be applied to develop next-generation sustainable plastics.