Exosomes from TNF-α preconditioned human umbilical cord mesenchymal stromal cells inhibit the autophagy of acinar cells of severe acute pancreatitis via shuttling bioactive metabolites.

Severe acute pancreatitis (SAP) is a common critical disease of the digestive system, with high mortality and a lack of effective prevention and treatment measures. Despite mesenchymal stromal cell transplantation having the potential to treat SAP, its clinical application prospect is limited, and the mechanism is unclear. Here, we reveal the therapeutic role of exosomes from TNF-α-preconditioned human umbilical cord mesenchymal stromal cells (HUCMSCs) in attenuating SAP and show that it is partly dependent on exosomal metabolites. Bioactive metabolomics analysis showed that 48 metabolites be significantly differentially expressed between the two groups (Exo-Ctrl group versus Exo-TNF-α group). Then, the further functional experiments indicated that 3,4-dihydroxyphenylglycol could be a key molecule mediating the therapeutic effect of TNF-α-preconditioned HUCMSCs. The animal experiments showed that 3,4-dihydroxyphenylglycol reduced inflammation and oxidative stress in the pancreatic tissue and inhibited acinar cell autophagy in a rat model of SAP. Mechanistically, we revealed that 3,4-dihydroxyphenylglycol activated the mTOR pathway to inhibit acinar cell autophagy and alleviate SAP. In summary, our study demonstrated that exosomes from TNF-α-preconditioned HUMSCs inhibit the autophagy of acinar cells of SAP by shuttling 3,4-dihydroxyphenylglycol and inhibiting the mTOR pathway. This study revealed the vital role and therapeutic potential of metabolite-derived exosomes in SAP, providing a new promising method to prevent and therapy SAP.

Tumor Necrosis Factor Alpha Preconditioned Umbilical Cord Mesenchymal Stem Cell-Derived Extracellular Vesicles Enhance the Inhibition of Necroptosis of Acinar cells in Severe Acute Pancreatitis.

Severe acute pancreatitis (SAP) is a common abdominal emergency with a high mortality rate and a lack of effective therapeutic options. Although mesenchymal stem cell (MSC) transplantation is a potential treatment for SAP, the mechanism remains unclear. It has been suggested that MSCs may act mainly through paracrine effects; therefore, we aimed to demonstrate the therapeutic efficacy of extracellular vesicles (EVs) derived from human umbilical cord mesenchymal stem cells (UCMSCs) for SAP. Na-taurocholate was used to induce a rat SAP model through retrograde injection into the common biliopancreatic duct. After 72 h of EVs transplantation, pancreatic pathological damage was alleviated, along with a decrease in serum amylase activity and pro-inflammatory cytokine levels. Interestingly, when UCMSCs were preconditioned with 10 ng/mL tumor necrosis factor alpha (TNF-α) for 48 h, the obtained EVs (named TNF-α-EVs) performed an enhanced efficacy. Furthermore, both animal and cellular experiments showed that TNF-α-EVs alleviated the necroptosis of acinar cells of SAP through RIPK3/MLKL axis. In conclusion, our study demonstrated that TNF-α-EVs were able to enhance the therapeutic effect on SAP by inhibiting necroptosis compared to normal EVs. This study heralds that TNF-α-EVs may be a promising therapeutic approach for SAP in the future.

MSCs Deliver Hypoxia-Treated Mitochondria Reprogramming Acinar Metabolism to Alleviate Severe Acute Pancreatitis Injury.

Mitochondrial function impairment due to abnormal opening of the mitochondrial permeability transition pore (MPTP) is considered the central event in acute pancreatitis; however, therapeutic choices for this condition remain controversial. Mesenchymal stem cells (MSCs) are a family member of stem cells with immunomodulatory and anti-inflammatory capabilities that can mitigate damage in experimental pancreatitis. Here, it is shown that MSCs deliver hypoxia-treated functional mitochondria to damaged pancreatic acinar cells (PACs) via extracellular vesicles (EVs), which reverse the metabolic function of PACs, maintain ATP supply, and exhibit an excellent injury-inhibiting effect. Mechanistically, hypoxia inhibits superoxide accumulation in the mitochondria of MSCs and upregulates the membrane potential, which is internalized into PACs via EVs, thus, remodeling the metabolic state. In addition, cargocytes constructed via stem cell denucleation as mitochondrial vectors are shown to exert similar therapeutic effects to MSCs. These findings reveal an important mechanism underlying the role of mitochondria in MSC therapy and offer the possibility of applying mitochondrial therapy to patients with severe acute pancreatitis.

The efficacy and safety of laparoscopic common bile duct exploration and cholecystectomy for the treatment of difficult common bile duct stones combined with gallstones: a multicenter retrospective study.

PURPOSE: To analyze the benefits of laparoscopic common bile duct exploration and laparoscopic cholecystectomy (LCBDE + LC) versus endoscopic retrograde cholangiopancreatography and/or endoscopic sphincterotomy following laparoscopic cholecystectomy (ERCP/EST + LC) for difficult common bile duct stones combined with gallstones. METHODS: A retrospective analysis of consecutive patients with difficult common bile duct stones combined with gallstones in three hospitals from January 2016 to January 2021 was performed. RESULTS: ERCP/EST + LC contributed to reducing postoperative drainage time. However, LCBDE + LC showed a higher rate of complete clearance, along with lower postoperative hospital stays, expenses and incidence of postoperative hyperamylasemia, pancreatitis, re-operation and recurrence. In addition, LCBDE + LC showed safe and feasible performance in the elderly and patients with previous upper abdominal surgery. CONCLUSION: It is an effective and safe method for LCBDE + LC for difficult common bile duct stones combined with gallstones.

Is T-tube drainage no longer needed for laparoscopic common bile duct exploration? A retrospective analysis and literature review.

Introduction: Primary closure (PC) following laparoscopic common bile duct exploration (LCBDE) is increasingly becoming a safe and effective option for choledocholithiasis. However, whether T-tube drainage (TTD) is no longer needed for LCBDE remains under debate. Aim: To evaluate the safety and efficacy of PC and TTD following LCBDE, and discuss their indications for selection of the procedure, combined with a literature review. Material and methods: 826 consecutive patients who underwent LCBDE with PC or TTD at Shanghai Tenth People's Hospital were reviewed. The clinical data of postoperative outcomes were compared and analyzed. Propensity score matching (PSM) was used to adjust for potential baseline confounding. Results: Of these patients, 796 underwent PC and 30 underwent TTD. Twenty-eight (3.52%) cases occurred in bile leakage in PC, and all of them were treated successfully with conservative therapy. Additionally, there was no evidence of bile duct stricture and death in all PC cases. TTD was mainly performed in patients with a higher rate of cholangitis (50.00%), large stones (26.67%), impacted stones (23.33%) and laser lithotripsy (26.67%). After PSM, 23 cases with PC and TTD were included. In the PC group, the operative time, postoperative stay, hospital expenses and recurrence rate were significantly shorter or less than in the TTD group. However, there were no significant differences between the two groups in postoperative drainage time, complications, reoperations and bile duct stricture rate. Conclusions: PC following LCBDE is safe and effective for choledocholithiasis. TTD is a safe alternative method for bile duct closure in certain special cases, such as acute cholangitis, large stones, impacted stones, and laser lithotripsy.

Mesenchymal Stromal Cell-Based Targeted Therapy Pancreatic Cancer: Progress and Challenges.

Pancreatic cancer is an aggressive malignancy with high mortality rates and poor prognoses. Despite rapid progress in the diagnosis and treatment of pancreatic cancer, the efficacy of current therapeutic strategies remains limited. Hence, better alternative therapeutic options for treating pancreatic cancer need to be urgently explored. Mesenchymal stromal cells (MSCs) have recently received much attention as a potential therapy for pancreatic cancer owing to their tumor-homing properties. However, the specific antitumor effect of MSCs is still controversial. To this end, we aimed to focus on the potential anti-cancer treatment prospects of the MSC-based approach and summarize current challenges in the clinical application of MSCs to treat pancreatic cancer.

Low aspartate aminotransferase/alanine aminotransferase (DeRitis) ratio assists in predicting diabetes in Chinese population.

Background: Few studies discussed the predictive ability of aspartate aminotransferase/alanine aminotransferase (AST/ALT, DeRitis) ratio for diabetes risk. The aim of this study was to characterize the role of AST/ALT ratio in the prediction of Chinese diabetes. Methods: This retrospective cohort study analyzed a Chinese population comprising 87,883 participants without diabetes at baseline between 2010 and 2016. Cox proportional hazards regression was used to identify independent risk factors. Restricted cubic spline (RCS) was performed to investigate the non-linear correlation between AST/ALT ratio and diabetes risk. Results: During a median follow-up period of 3.01 years, 1,877 participants developed diabetes. Comparing the baseline characteristics, diabetes group exhibited lower AST/ALT ratio. The Kaplan-Meier curve showed that participants with low AST/ALT ratio had higher cumulative incidence, and Cox regression also demonstrated that the lower AST/ALT ratio, the higher diabetes risk (HR: 0.56, 95% CI: 0.37-0.85, P = 0.006). The RCS model revealed a non-linear correlation between AST/ALT ratio and diabetes risk. In the condition of AST/ALT ratio ≤1.18, diabetes risk increased as it decreased (HR: 0.42, 95% CI: 0.19-0.91, P = 0.028). In contrast, AST/ALT ratio did not independently affect diabetes when beyond 1.18. Conclusion: AST/ALT ratio is a valuable predictor of diabetes. Diabetes risk increases rapidly in the condition of AST/ALT ratio ≤1.18.

Chinese and Global Burdens of Gastrointestinal Cancers From 1990 to 2019.

Background: Gastrointestinal (GI) cancers are an important component of the tumor. This study aimed to investigate the burden of six major GI cancers in China and globally from 1990 to 2019. Methods: We conducted a cross-sectional study based on the Global Burden of Disease Study (GBD) 2019. Indicators on incidence, deaths, disability-adjusted life-years (DALYs), and risk factors for esophageal, stomach, liver, pancreatic, colon and rectum, and gallbladder and biliary tract cancers were collected and analyzed for time trends. The contribution of each cancer and the proportion of cases in China among global cases were further reported. Results: Global incidence cases, death cases, and DALYs of GI cancers showed an overall ascending trend over the past 30 years, but there was temporal and geographical variation across cancer types. By 2019, colon and rectum cancer had overtaken stomach cancer as the most burdensome GI cancer globally. However, stomach cancer narrowly continued to be the most burdensome GI in China. In addition, the proportion of incidence and death cases of stomach, pancreatic, colon and rectum, and gallbladder and biliary tract cancers among global cases had further increased. It was noteworthy that the burden of liver cancer in China has been alleviated significantly. Conclusion: GI cancers remain a major public health problem in China and globally. Despite the temporal and geographic diversity of different cancers, targeted primary and secondary prevention are still necessary for the future to face these unknown challenges.

A nomogram for predicting stones recurrence in patients with bile duct stones undergoing laparoscopic common bile duct exploration.

Background: The recurrence of bile duct stones is a long-term outcome for patients undergoing laparoscopic common bile duct exploration (LCBDE) that is worthy of attention. This study aimed to investigate long-term risk factors for stones recurrence after LCBDE and develop a nomogram for predicting the risk. Methods: The clinical data on consecutive patients with bile duct stones undergoing LCBDE at Shanghai Tenth People's Hospital between January 2014 and February 2019 with a follow-up period longer than 2 years were reviewed. Independent risk factors of stones recurrence identified by the Cox regression model were used to develop a nomogram in predicting stones recurrence after LCBDE. Results: Eight hundred and twenty-two patients were eventually included in this study. Of these patients, 42 (5.11%) developed stones recurrence. The cumulative incidences of stones recurrence at 1, 3, and 5 years after LCBDE were 1.34%, 4.36%, and 7.14%, respectively. Independent risk factors of stones recurrence were identified to be age (HR = 1.04, 95% CI = 1.02-1.07), T-tube drainage (HR = 3.28, 95% CI = 1.23-8.72), fatty liver (HR = 2.69, 95% CI = 1.39-5.20), urinary calculus (HR = 4.68, 95% CI = 2.29-9.56), post-cholecystectomy (HR = 5.21, 95% CI = 2.39-11.33), and post-ERCP + EST (HR = 2.87, 95% CI = 1.18-6.96). By these factors, a developed nomogram showed a C-index of 0.770 to predict stones recurrence. Conclusions: The nomogram, based on identified risk factors, showed good accuracy for predicting stones recurrence, which is valuable to guide these patients' follow-up and prevention.

Immune Persistence and Safety After SARS-CoV-2 BNT162b1 mRNA Vaccination in Chinese Adults: A Randomized, Placebo-Controlled, Double-Blind Phase 1 Trial.

INTRODUCTION: BNT162b1 is a lipid nanoparticle-formulated, nucleoside-modified mRNA SARS-CoV-2 vaccine. Here, we report safety and immune persistence data following a primary two-dose vaccination schedule administered 21 days apart. METHODS: Immune persistence was determined at month 3 in 72 younger participants (aged 18-55 years) and at month 6 in 70 younger and 69 older participants (aged 65-85 years). RESULTS: In younger participants, neutralizing antibody (nAb) geometric mean titers (GMTs) for the 10 and 30 µg dose levels declined from 233 and 254 (21 days after dose 2) to 55 and 87 at month 3, respectively, and to 16 and 27 at month 6, respectively. In older participants, nAb GMTs declined from 80 and 160 (21 days after dose 2) to 10 and 21 at month 6. Overall, higher antibody titers were observed in younger participants, and the 30 µg dose induced higher levels of nAb, which declined more slowly by month 6. No serious adverse events were reported in the vaccine group. CONCLUSION: This study showed BNT162b1 maintains a favorable safety profile in younger and older participants in the 6 months after vaccination. This study further extends our understanding of immune persistence and the safety of the BNT162b1 vaccine as a candidate vaccine in the BioNTech pipeline. TRIAL REGISTRATION NUMBER: NCT04523571, registered August 21, 2020.

Bone marrow-derived mesenchymal stem cells ameliorate severe acute pancreatitis by inhibiting oxidative stress in rats.

To investigate whether bone marrow mesenchymal stem cells (BMSCs) attenuate pancreatic injury via mediating oxidative stress in severe acute pancreatitis (SAP). The SAP model was established in rats. Phosphate buffered saline (PBS) or BMSCs were injected into the rats by tail veins. ML385 was used to down-regulate Nrf2 expression in rats. Pancreatic pathological score was used to evaluated pancreatic injury. Inflammatory-associated cytokines, serum lipase and amylase, levels of myeloperoxidase, malondialdehyde, reactive oxygen species and superoxide dismutase, as well as catalase activity were measured for injury severity evaluation. ML385 aggravates oxidative stress in SAP + ML385 group, compared with SAP + PBS group. BMSCs transplantation alleviated pancreatic injury and enhance antioxidant tolerance in SAP + BMSCs group, while ML385 administration weakened this efficacy in SAP + BMSCs + ML385 group. In addition, BMSCs promoted Nrf2 nuclear translocation via PI3K/AKT signaling pathway. Besides, BMSCs reduced inflammatory response by inhibiting NF-κB signaling pathway in SAP. BMSCs can inhibit oxidative stress and reduce pancreatic injury via inducing Nrf2 nuclear translocation in SAP.

Typical scaled food web structure and total mercury enrichment characteristics in Xingkai Lake, China.

Different from the widely used constant discrimination factor Δ15N = 3.4‰ between two adjacent trophic positions (TPs), a scaled Δ15N framework for evaluating the TP of species was developed in 2014, that is, the Δ15N between two adjacent TPs decreases as the TP increases which is considered to be in closer conformity to the trophic cascade in the natural food web. In this study, we compared the two TP calculation methods and then reconsidered the evaluation of the trophic magnification factors (TMFs). Our results show that the TPscaled value is higher and the TMFs value is lower under the scaled Δ15N framework, indicating that the TMFs value under the constant Δ15N framework is often overestimated. We further constructed a diet proportion food web model, which shows that species with lower TP has higher contribution rate as food sources. In Xingkai Lake, the enrichment process of mercury in the food web is not strictly consistent with the diet proportion of the food web. Based on the diet proportion food web model and the mercury enrichment model, it can be found that the White shrimp (Exopalaemon modestus) is not only an important food source, but also the main source of mercury transmission in the food web. Overall, our findings have quantified the food web construction and thus facilitated a better understanding of the interaction between the diet proportion and the bio-concentration in the food web.

Management and long-term outcomes of acute right colonic diverticulitis and risk factors of recurrence.

BACKGROUND: Acute right-sided colonic diverticulitis (RCD) is a common disease in Asian populations for which the optimal treatment remains controversial. The aim of this study was to investigate management and evaluate long-term outcomes of treatment in patients with acute RCD. METHODS: We retrospectively collected and analyzed clinical data for patients with acute RCD admitted to the Tongren Hospital, Shanghai Jiao Tong University School of Medicine from December 2015 to December 2020. The patients were divided into two groups, according to primary treatment strategy, which was either conservative treatment or surgical treatment. RESULTS: A total of 162 consecutive patients with acute RCD were enrolled in the study. There was no significant difference in age, sex, history of abdominal surgery, medical co-morbidities, fever, previous history of RCD, treatment success rate and incidence of complications between the conservative and surgery groups. However, the recurrence rate in conservative groups was significantly higher than in surgery groups (16.53% vs 2.44%, P = 0.020). And more frequent bowel movements and previous history of RCD increased the risk of recurrence of acute RCD. Moreover, there was no significant difference in either treatment success rate or the overall recurrence rate between the patients with uncomplicated diverticulitis and patients with complicated diverticulitis. CONCLUSIONS: Surgical treatment is also safe and effective for acute RCD. Surgical treatment should mainly be considered for patients with acute RCD with recurrence risk factors (more frequent bowel movements and previous history of RCD) or with complicated acute RCD.

Safety and efficacy of laparoscopic common bile duct exploration for the patients with difficult biliary stones: 8 years of experiences at a single institution and literature review.

BACKGROUND: Laparoscopic common bile duct exploration (LCBDE) has gained wide popularity for the treatment of choledocholithiasis. However, it remains unclear whether LCBDE is a better alternative option for the patients with difficult biliary stones. Thus, the aim of the present study was to explore the safety and efficacy of LCBDE for these patients by retrospectively analyzing our data and combing with literature review. METHODS: Between September 2011 and February 2019, 1064 consecutive patients who underwent LCBDE at Shanghai Tenth People's Hospital were reviewed. The clinical data of patients with difficult biliary stones were selected and retrospectively analyzed. RESULTS: Of these patients, 334 cases were confirmed with difficult biliary stones, and the overall complete stone clearance rate was 98.8% (330/334). 34 cases (10.2%) were performed with laser lithotripsy. A total of 296 patients (88.6%) underwent primary closure of common bile duct, and T-tube drainage was indwelled in 38 patients (11.4%). No bile duct injury, bleeding, perforation and surgery-related deaths were observed. The overall morbidity rate was 6.6%. 16 cases (4.8%) occurred in bile leakage with primary closure procedure, and all of them were managed successfully with conservative therapy. The median follow-up period was 9 months with stone recurrence occurring in 9 patients (2.7%). There was no evidence of bile duct stricture in all cases. CONCLUSIONS: The current study suggests that LCBED is a considerable safe and effective option for the patients with difficult biliary stones. A randomized clinical trial is needed to further evaluate the benefit of LCBDE in this subgroup.

Dearomatization-rearomatization strategy of tyrosine for peptide/protein modification through thiol-addition reactions.

We have developed a dearomatization-rearomatization strategy for the modification of peptides/proteins through a thiol-Michael addition to the electrophilic cyclohexadienone intermediate that is generated in situ via the oxidation of tyrosine. This strategy enriches the conjugation toolbox and has great potential for applications in medicinal chemistry and chemical biology.

Safety and immunogenicity of a recombinant COVID-19 vaccine (Sf9 cells) in healthy population aged 18 years or older: two single-center, randomised, double-blind, placebo-controlled, phase 1 and phase 2 trials.

COVID-19 vaccines from multiple manufacturers are needed to cope with the problem of insufficient supply. We did two single-center, randomised, double-blind, placebo-controlled phase 1 and phase 2 trials to assess the safety, tolerability and immunogenicity of a recombinant COVID-19 vaccine (Sf9 cells) in healthy population aged 18 years or older in China. Eligible participants were enrolled, the ratio of candidate vaccine and placebo within each dose group was 3:1 (phase 1) or 5:1 (phase 2). From August 28, 2020, 168 participants were sequentially enrolled and randomly assigned to receive the low dose vaccine, high dose vaccine or placebo with the schedule of 0, 28 days or 0, 14, 28 days in phase 1 trial. From November 18, 2020, 960 participants were randomly assigned to receive the low dose vaccine, high dose vaccine or placebo with the schedule of 0, 21 days or 0, 14, 28 days in phase 2 trial. The most common solicited injection site adverse reaction within 7 days in both trials was pain. The most common solicited systematic adverse reactions within 7 days were fatigue, cough, sore throat, fever and headache. ELISA antibodies and neutralising antibodies increased at 14 days, and peaked at 28 days (phase 1) or 30 days (phase 2) after the last dose vaccination. The GMTs of neutralising antibody against live SARS-CoV-2 at 28 days or 30 days after the last dose vaccination were highest in the adult high dose group (0, 14, 28 days), with 102.9 (95% CI 61.9-171.2) and 102.6 (95% CI 75.2-140.1) in phase 1 and phase 2 trials, respectively. Specific T-cell response peaked at 14 days after the last dose vaccination in phase 1 trial. This vaccine is safe, and induced significant immune responses after three doses of vaccination.

Mesenchymal stromal cell therapy for pancreatitis: Progress and challenges.

Pancreatitis is a common gastrointestinal disease with no effective therapeutic options, particularly for cases of severe acute and chronic pancreatitis (CP). Mesenchymal stromal cells (MSCs) are multipotent cells with diverse biological properties, including directional migration, paracrine, immunosuppressive, and antiinflammatory effects, which are considered an ideal candidate cell type for repairing tissue damage caused by various pathogenies. Several researchers have reported significant therapeutic efficacy of MSCs in animal models of acute and CP. However, the specific underlying mechanisms are yet to be clarified and clinical application of MSCs as pancreatitis therapy has rarely been reported. This review mainly focuses on the potential and challenges in clinical application of MSCs for treatment of acute and CP, along with discussion of the underlying molecular mechanisms.

Safety and immunogenicity of the SARS-CoV-2 BNT162b1 mRNA vaccine in younger and older Chinese adults: a randomized, placebo-controlled, double-blind phase 1 study.

An effective vaccine is needed to end the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic. Here, we assess the preliminary safety, tolerability and immunogenicity data from an ongoing single-center (in Jiangsu province, China), parallel-group, double-blind phase 1 trial of the vaccine candidate BNT162b1 in 144 healthy SARS-CoV-2-naive Chinese participants. These participants are randomized 1:1:1 to receive prime and boost vaccinations of 10 µg or 30 µg BNT162b1 or placebo, given 21 d apart, with equal allocation of younger (aged 18-55 years) and older adults (aged 65-85 years) to each treatment group (ChiCTR2000034825). BNT162b1 encodes the SARS-CoV-2 spike glycoprotein receptor-binding domain (RBD) and is one of several messenger RNA-based vaccine candidates under clinical investigation. Local reactions and systemic events were generally dose dependent, transient and mild to moderate. Fever was the only grade 3 adverse event. BNT162b1 induced robust interferon-γ T cell responses to a peptide pool including the RBD in both younger and older Chinese adults, and geometric mean neutralizing titers reached 2.1-fold (for younger participants) and 1.3-fold (for the older participants) that of a panel of COVID-19 convalescent human sera obtained at least 14 d after positive SARS-CoV-2 polymerase chain reaction test. In summary, BNT162b1 has an acceptable safety profile and produces high levels of humoral and T cell responses in an Asian population.

SLC22A14 is a mitochondrial riboflavin transporter required for sperm oxidative phosphorylation and male fertility.

Ablation of Slc22a14 causes male infertility in mice, but the underlying mechanisms remain unknown. Here, we show that SLC22A14 is a riboflavin transporter localized at the inner mitochondrial membrane of the spermatozoa mid-piece and show by genetic, biochemical, multi-omic, and nutritional evidence that riboflavin transport deficiency suppresses the oxidative phosphorylation and reprograms spermatozoa energy metabolism by disrupting flavoenzyme functions. Specifically, we find that fatty acid ß-oxidation (FAO) is defective with significantly reduced levels of acyl-carnitines and metabolites from the TCA cycle (the citric acid cycle) but accumulated triglycerides and free fatty acids in Slc22a14 knockout spermatozoa. We demonstrate that Slc22a14-mediated FAO is essential for spermatozoa energy generation and motility. Furthermore, sperm from wild-type mice treated with a riboflavin-deficient diet mimics those in Slc22a14 knockout mice, confirming that an altered riboflavin level causes spermatozoa morphological and bioenergetic defects. Beyond substantially advancing our understanding of spermatozoa energy metabolism, our study provides an attractive target for the development of male contraceptives.