Type I interferon signaling pathway enhances immune-checkpoint inhibition in KRAS mutant lung tumors.

Lung cancer is the leading cause of cancer mortality worldwide. KRAS oncogenes are responsible for at least a quarter of lung adenocarcinomas, the main subtype of lung cancer. After four decades of intense research, selective inhibitors of KRAS oncoproteins are finally reaching the clinic. Yet, their effect on overall survival is limited due to the rapid appearance of drug resistance, a likely consequence of the high intratumoral heterogeneity characteristic of these tumors. In this study, we have attempted to identify those functional alterations that result from KRAS oncoprotein expression during the earliest stages of tumor development. Such functional changes are likely to be maintained during the entire process of tumor progression regardless of additional co-occurring mutations. Single-cell RNA sequencing analysis of murine alveolar type 2 cells expressing a resident Kras oncogene revealed impairment of the type I interferon pathway, a feature maintained throughout tumor progression. This alteration was also present in advanced murine and human tumors harboring additional mutations in the p53 or LKB1 tumor suppressors. Restoration of type I interferon (IFN) signaling by IFN-ß or constitutive active stimulator of interferon genes (STING) expression had a profound influence on the tumor microenvironment, switching them from immunologically "cold" to immunologically "hot" tumors. Therefore, enhancement of the type I IFN pathway predisposes KRAS mutant lung tumors to immunotherapy treatments, regardless of co-occurring mutations in p53 or LKB1.

Measuring Team Functioning During the COVID-19 Pandemic: Perspectives of Cancer Care Team Members.

Background: In a public health crisis such as COVID-19, cancer teams face significant challenges including acute work disruptions, rapid shifts in clinical practice, and burnout. Within this context, it is crucial to explore team functioning from the perspectives of multiple stakeholders. Objective: This quantitative pilot study aimed to 1) measure perceptions of multi-stakeholders on key indicators of team functioning (Team Effectiveness, TE, and Team Relational Coordination, TRC) during COVID-19 and its transition, and 2) document whether patient perceptions of TE/TRC are significantly associated with their cancer care experiences. Methods: A descriptive design with repeated measures was used. Through convenience sampling, participants were recruited from two outpatient cancer clinics at a large university-affiliated hospital, in Montréal, Qc, Canada. Sixty-six participants (ie, 13 healthcare professionals, 40 patients, 6 informal caregivers, and 7 volunteers) completed e-measures at T1 (years 2021-2022) and n = 44 at T2 (year 2023). Results: At T1, participants reported high perceptions of Team Effectiveness (scale 1 to 6) M = 4.47; SD = 0.7 (Mdn = 4.54; IQR: 4.06-5) and Relational Coordination (scale 1 to 5) M = 3.77; SD = 0.77 (Mdn = 3.81; IQR: 3.12-4.38) with no significant differences in perceptions across the four groups. At T2, no significant changes in TE/TRC perceptions were found. At both time points, patient perceptions of TE/TRC were significantly correlated with positive cancer care experiences (Spearman rank correlation rs ranging from 0.69 and 0.83; p < 0.01). Conclusion: To our knowledge, this is the first study documenting perceptions of cancer team functioning amidst the pandemic as reported by multiple stakeholders. Significant relationships between patient perceptions of TE/TRC and their cancer care experiences underscore the importance of including patients' views in team functioning processes. Future work should rely on larger sample sizes to further explore key elements of optimal team functioning.

Breast Metastasis From Cutaneous Melanoma: Beyond the Infiltrating Ductal Carcinoma.

Breast metastases of extramammary origin are an extremely rare entity. Solid organ metastases to the breast include malignant melanoma, epithelial carcinoma (adenocarcinoma and squamous cell carcinoma of the lung and gastrointestinal tract), and sarcoma. A breast neoplasm can be caused by a primary tumor, in-transit metastasis, breast metastasis, and skin metastasis. A 42-year-old female patient presented with a hyperpigmented lesion on the first finger of her left hand. An incisional biopsy was carried out, reporting pigmented epithelioid melanoma. Amputation of the finger was performed, as well as an axillary sentinel lymph node excision. Later during the treatment and follow-up by medical oncology, a breast tumor was located, followed by a protocol and the approach of possible differential diagnoses. Finally, it was characterized as metastatic cutaneous melanoma. The therapeutic approach regarding the possible origin of the metastatic neoplastic character of breast tumors culminated in this case in the palliative treatment with immunotherapy of cutaneous malignant melanoma. The diagnosis of breast metastases from cutaneous malignant melanoma is a real challenge, so an extensive history and high clinical suspicion are crucial in order to provide adequate treatment, despite the gloomy prognosis.

Pilot Randomized Controlled Trial of Lymfit: A Theory-Guided Exercise Intervention for Young Adults with Lymphoma.

Despite the rapidly emerging evidence on the contributions of physical activity to improving cancer-related health outcomes, adherence to physical activity among young adults with lymphoma remains suboptimal. Guided by self-determination theory (SDT), the Lymfit intervention (a 12-week individualized exercise program with bi-weekly kinesiologist support and an activity tracker) aimed to foster autonomous motivation toward physical activity. This pilot randomized controlled trial aimed to evaluate the feasibility, acceptability, and preliminary effects of Lymfit. Young adults (N = 26; mean age of 32.1 years) with lymphoma who were newly diagnosed and those up to six months after completing treatment were recruited and randomly assigned one-to-one to either the intervention group (n = 13) or a wait-list control group (n = 13). All a priori feasibility benchmarks were met, confirming the feasibility of the study in terms of recruitment uptake, retention, questionnaire completion, intervention fidelity, missing data, Fitbit wear adherence, and control group design. The intervention acceptability assessment showed high ratings, with eight out of ten items receiving >80% high ratings. At post-intervention, an analysis of covariance models showed a clinically significant increase in self-reported physical activity levels, psychological need satisfaction, and exercise motivation in the intervention group compared to controls. Lymfit also led to meaningful changes in six quality-of-life domains in the intervention group, including anxiety, depression, fatigue, sleep disturbance, social roles and activities, and pain interference. The findings support Lymfit as a promising means to meet psychological needs and increase the autonomous motivation for physical activity in this group. A fully powered efficacy trial is warranted to assess the validity of these findings.

Evidence of the Existence of Site-Specific Female Contact Pheromones Involved in the Sexual Interaction Behavior of the Pacific Whiteleg Shrimp Penaeus vannamei.

Although the presence of female contact sex pheromones in P. vannamei has been hypothesized, to date its existence has not been proven. To gather more evidence of their existence, cuticular liposoluble extracts were obtained from the following samples of adult females to be used as the experimental treatments: (1) ventral exoskeleton of immature female (VI), (2) dorsolateral exoskeleton of immature female (DI), (3) ventral exoskeleton of mature female (VM), and (4) dorsolateral exoskeleton of mature female (DM). Polyvinyl chloride tubes (artificial females; AF) were coated with each extract and the behavior displayed by sexually mature males in contact with the AF was recorded and classified as follows: 0 = no response; 1 = contact; 2 = pushing; and 3 = prolonged contact (≥10 s). To test the hypothesis that the extracts collected from the ventral portion of the abdomen exoskeleton have a higher effect on the behavior of males than the extracts collected from the dorsolateral portion of the abdomen exoskeleton, the experiment was divided into two bioassays: Bioassay I (VI vs. DI) and Bioassay II (VM vs. DM). In each bioassay, all experimental treatments were significantly different (p > 0.05) from the CTL group (AF coated with hexane). Notably, the pushing behavior was significantly higher (p < 0.05) in the VI treatment compared to the CTL and DI treatment. These results provide evidence of the existence of contact female sex pheromones with sexual recognition function located primarily in the ventral portion of the abdomen exoskeleton of P. vannamei.

Sudoscan's Effectiveness in Identifying Chronic Kidney Disease in Patients With Type 2 Diabetes.

Chronic kidney disease (CKD) represents a significant public health issue, particularly prevalent among patients with type 2 diabetes mellitus (T2DM). CKD occurs in approximately 20% to 40% of adults with diabetes mellitus. Sudoscan potentially detects CKD early, providing a non-invasive and convenient alternative to traditional screening methods that rely on serum creatinine and urine albumin levels. This research involves 271 patients from a single medical center over one year, with all participants providing informed consent. The prevalence of CKD in our group was 26.5% (n = 72). This study integrates a comprehensive examination, including anthropometric measurements, biochemical profiles, and Sudoscan's electrochemical skin conductance testing. CKD diagnosis was confirmed via estimated glomerular filtration rate (eGFR) and albumin-to-creatinine ratio (ACR). The aim of this study was to explore the utility of Sudoscan in detecting CKD among patients with T2DM. Statistical analysis reveals moderate correlations between Sudoscan scores and traditional CKD markers like eGFR and albuminuria. It is beneficial in settings where conventional testing is less accessible, suggesting potential for broader CKD screening programs. Key findings suggest that Sudoscan can identify early renal dysfunction with reasonable sensitivity and specificity. Integrating Sudoscan in regular CKD screening could enhance early detection, allowing for timely interventions to prevent progression to end-stage renal disease and reduce healthcare burdens associated with advanced CKD. The results contribute to the ongoing assessment of innovative technologies in managing chronic diseases related to diabetes.

Acute Glomerulonephritis as a Paraneoplastic Syndrome Secondary to Urachal Adenocarcinoma: An Unknown Entity.

Urachal carcinoma is an uncommon malignancy with a peculiar biomolecular characterization and therefore a complex approach. It was incorporated by the World Health Organization in 2004 in the tumors of the urinary system classification. This neoplasm is generally diagnosed in advanced stages. The standard treatment is surgical, however, due to the rarity and relatively late clinical manifestation of urachal carcinomas, the survival data are mostly case reports, as well as information about medical-surgical treatment based on evidence. The data used were extracted from both the physical and electronic clinical records. Among atypical presentations reported in the literature, we report a case of urachal adenocarcinoma with simultaneous glomerulonephritis as a paraneoplastic syndrome of which there is no report to date. Surgery was carried out in our patient, unfortunately with lifetime morbidity from kidney function replacement secondary to kidney function damage by glomerulonephritis, despite previous immunosuppression treatment for rapidly progressive glomerulonephritis. It is worth mentioning that if the initial diagnosis represents a clinical challenge, treatment is even more complex, given the little information that currently exists about it. Urachal carcinoma is a diagnostic and treatment challenge. Up to now, surgery has been the treatment of choice in localized or locally advanced disease, however, with a high morbidity for the patient.

Intraspecific Variation in Mercury Contamination of Alligator Snapping Turtles (Macrochelys temminckii).

Macrochelys temminckii (alligator snapping turtle) is an aquatic turtle endemic to the southeastern United States that was proposed for listing under the Endangered Species Act in 2021. In the present study we analyzed total mercury (THg) concentrations in skeletal muscle, tail clips, and nail tissue of 93 M. temminckii sampled from 14 waterbodies in eastern Texas (USA). Our objectives were to assess (1) the degree of correlation between internal tissue (skeletal muscle and tail clip samples) and keratin (nail samples), (2) the influence of ecological factors (turtle size and waterbody/sampling site) on THg concentrations, and (3) whether THg concentrations were high enough to pose a risk to human consumers. The mean (±SE) THg concentrations of muscle and nail were 1.16 ± 0.08 µg/g dry weight and 4.21 ± 0.24 µg/g dry weight, respectively, and THg concentrations were highly dependent on the sampling site. The THg concentrations of nails were correlated with muscle concentrations (R2 = 0.56, p < 0.001). The effect of body size on THg concentrations varied by sampling site, indicating that size is not a good predictor of Hg concentration across sites. Finally, THg concentrations in M. temminckii of eastern Texas were high enough to pose a potential risk to human health based on US Environmental Protection Agency dietary guidelines. Environ Toxicol Chem 2024;43:1903-1913. © 2024 SETAC. This article has been contributed to by U.S. Government employees and their work is in the public domain in the USA.

Comparing Leadership Skills of Senior Emergency Medicine Residents in 3-Year Versus 4-Year Programs During Simulated Pediatric Resuscitation: A Pilot Study.

OBJECTIVES: The majority of pediatric patients in the United States (US) are evaluated and treated at general emergency departments. It is possible that discrepancies in length of emergency medicine (EM) residency training may allow for variable exposure to pediatric patients, critical resuscitations, and didactic events. The goal of this pilot study was to compare leadership skills of graduating EM residents from 3- to 4-year programs during simulated pediatric resuscitations using a previously validated leadership assessment tool, the Concise Assessment of Leader Management (CALM). METHODS: This was a prospective, multicenter, simulation-based cohort pilot study that included graduating 3 rd - and 4 th -year EM resident physicians from 6 EM residency programs. We measured leadership performance across 3 simulated pediatric resuscitations (sepsis, seizure, cardiac arrest) using the CALM tool and compared leadership scores between the 3 rd - and 4 th -year resident cohorts. We also correlated leadership to self-efficacy scores. RESULTS: Data was analyzed for 47 participating residents (24 3 rd -year residents and 23 4 th -year residents). Out of a total possible CALM score of 66, residents from 3-year programs scored 45.2 [SD ± 5.2], 46.8 [SD ± 5.0], and 46.6 [SD ± 4.7], whereas residents from 4-year programs scored 45.5 [SD ± 5.2], 46.4 [SD ± 5.0], and 48.2 [SD ± 4.3] during the sepsis, seizure, and cardiac arrest cases, respectively. The mean leadership score across all 3 cases for the 3-year cohort was 46.2 [SD ± 4.8] versus 46.7 [SD ± 4.5] ( P = 0.715) for the 4-year cohort. CONCLUSIONS: These data show feasibility for a larger cohort project and, while not statistically significant, suggest no difference in leadership skills between 3 rd - and 4 th -year EM residents in our study cohort. This pilot study provides the basis of future work that will assess a larger multicenter cohort with the hope to obtain a more generalizable dataset.

Canine Oral Melanoma: Questioning the Existing Information through a Series of Clinical Cases.

Twelve dogs with oral malignant melanomas (MM) were evaluated in this study, with demographic details indicating a balanced distribution of gender, age, and weight among various breeds. Tumor locations varied, with diverse surgical procedures being performed, including mandibulectomies and maxillectomies. Lymphadenectomies were conducted, revealing a 16.66% metastatic rate in regional lymph nodes. At the time of surgery, clinical staging identified stages I, II, and III, with most cases having non-infiltrated margins and a high mitotic index. Follow-up revealed local recurrences and metastases, prompting additional surgeries and affecting survival rates. This study reports varying outcomes, with some dogs completing one year without recurrence, while others experienced progressive disease, leading to six oral melanoma-related deaths. The characteristics of melanotic melanoma and amelanotic melanoma are observed in order to study differences between them, the degree of aggressiveness, the mortality rate and the possibility of future therapeutic targets. Although high pigmentation has been correlated with a better outcome, we could not find any significant correlation between survival and achromia. Oral benign melanomas might exist, and this could justify variabilities between stage and survival; however, carefulness is required due to their unpredictable behavior. The findings underscore the complexity of oral melanoma cases and highlight the need for further research on effective management strategies.

Isolation of Intestinal Macrophage Subpopulations for High-Quality Total RNA Purification in Zebrafish.

Intestinal macrophages have been poorly studied in fish, mainly due to the lack of specific molecular markers for their identification and isolation. To address this gap, using the zebrafish Tg(mpeg1:EGFP) transgenic line, we developed a fluorescence-activated cell sorting strategy (FACS) that allows us to isolate different intestinal macrophage subpopulations, based on GFP expression and morphological differences. Also, we achieved the purification of high-quality total RNA from each population to perform transcriptomic analysis. The complete strategy comprises three steps, including intestine dissection and tissue dissociation, the isolation of each intestinal macrophage population via FACS, and the extraction of total RNA. To be able to characterize molecularly different macrophage subpopulations and link them to their functional properties will allow us to unravel intestinal macrophage biology.

Effects of antidiabetic drugs on bone metabolism.

Objectives: The prevalence of diabetes mellitus type 2 (DMT2) is increasing exponentially worldwide. DMT2 patients have been found to be at a higher risk for bone fractures than the healthy population. Hence, improving our understanding of the impact of antidiabetic drugs on bone metabolism is crucial. Methods: A descriptive, retrospective study involving 106 patients receiving six groups of antidiabetic drugs: insulin; dipeptidylpeptidase four inhibitors (DPP4i); glucagon-like peptide type 1 receptor agonists (GLP1ra); sulfonylureas; sodium-glucose cotransporter two inhibitors (SGLT2i); and pioglitazone, in which osteocalcin (OC), bone alkaline phosphatase (BAP) and C-terminal telopeptide of collagen type 1 or beta-crosslaps (ß-CTx) were determined. Results: ß-CTx concentrations were higher in the patients treated with pioglitazone, as compared to patients treated with DPP4i (p=0.035), SGLT2i (p=0.020) or GLP1ra (p<0.001). The lowest ß-CTx concentrations were observed in the patients treated with GLP1ra. Conclusions: Bone remodeling is influenced by the type of antidiabetic drug administered to DMT2 patients. In our study, the patients who received pioglitazone showed higher ß-CTx concentrations, as compared to patients treated with other types of antidiabetic drugs. This finding highlights the convenience of avoiding these drugs, especially in postmenopausal women with DMT2. GLP1ra drugs were associated with the lowest ß-CTx concentrations, which suggests that these agents could exert beneficial effects on bone metabolism.

The Importance of Evaluating Sudomotor Function in the Diagnosis of Cardiac Autonomic Neuropathy.

INTRODUCTION:  Cardiac autonomic neuropathy (CAN) is a disorder affecting the autonomic nerves that regulate the cardiovascular system, leading to irregular heart rate and blood pressure control. It is commonly associated with diabetes mellitus but can also result from other conditions such as autoimmune disorders, chronic kidney disease, alcohol abuse, and certain medications. Screening for CAN is essential, particularly in individuals with poor glycemic control, cardiovascular risk factors, or complications. Early identification of CAN is vital for timely intervention to prevent or manage cardiovascular complications effectively. Regular screening helps detect CAN before symptoms emerge, enabling early intervention to slow or halt its progression. This study examined the relationship between sudomotor function and cardiovascular reflex tests. MATERIAL AND METHODS:  This was a cross-sectional study conducted between June 2019 and June 2020. The study included 271 subjects aged 18 years and above who provided informed consent, were diagnosed with type 2 diabetes mellitus (T2DM), and were overweight or obese. Exclusion criteria encompassed patients with other types of diabetes, pregnant women, those with recent neoplasm diagnoses, stroke sequelae, history of myocardial infarction, or pelvic limb amputations. The assessment of cardiac autonomic neuropathy involved conducting an electrocardiogram and evaluating the QTc interval in the morning before taking medication. Additionally, cardiovascular reflex tests (CART) were conducted, including assessments of heart rate variability during deep breathing, the Valsalva maneuver, and changes in orthostatic position. Simultaneously, the diagnosis of CAN was assessed by performing a sweat test using a Sudoscan assessment (Impeto Medical, Moulineaux, France).  Results: More than half of the participants (52%, n=143) were female. Significant differences in statistical measures were noted between females and males regarding age, systolic blood pressure, fasting blood glucose, A1c level, total cholesterol, triglycerides, gamma-glutamyl transferase, and bilirubin levels. Within the CAN-diagnosed group (CAN+), 40.92% were classified as mild cases (n=90), 47.27% as moderate cases (n=104), and 11.81% as severe cases (n=26). Among the CAN+ group, 54% (n=119) were women. Electrochemical skin conductance was lower in the CAN+ group than the CAN- group in hands (67.34±15.51 µS versus 72.38±12.12 µS, p=0.008) and feet (73.37±13.38 µS versus 82.84 ±10.29 µS, p<0.001). The Sudoscan-CAN score significantly correlated with Ewing scores (r= 0.522, p<0.001). In multiple linear regression analysis, the Sudoscan-CAN score remained significantly associated with age, high BMI, long-standing diabetes, and Ewing score. CONCLUSIONS:  Sudoscan demonstrates potential in identifying patients with an increased risk of CAN. Its integration into clinical practice can improve patient outcomes through early detection, risk stratification, and personalized treatment approaches. Its non-invasive, portable, and user-friendly features render it suitable for utilization in outreach programs or resource-constrained settings as part of screening efforts designed to pinpoint high-risk individuals for additional assessment.

In vivo assessment of marine vs bovine origin collagen-based composite scaffolds promoting bone regeneration in a New Zealand rabbit model.

The ability of human tissues to self-repair is limited, which motivates the scientific community to explore new and better therapeutic approaches to tissue regeneration. The present manuscript provides a comparative study between a marine-based composite biomaterial, and another composed of well-established counterparts for bone tissue regeneration. Blue shark skin collagen was combined with bioapatite obtained from blue shark's teeth (mColl:BAp), while bovine collagen was combined with synthetic hydroxyapatite (bColl:Ap) to produce 3D composite scaffolds by freeze-drying. Collagens showed similar profiles, while apatite particles differed in their composition, being the marine bioapatite a fluoride-enriched ceramic. The marine-sourced biomaterials presented higher porosities, improved mechanical properties, and slower degradation rates when compared to synthetic apatite-reinforced bovine collagen. The in vivo performance regarding bone tissue regeneration was evaluated in defects created in femoral condyles in New Zealand rabbits twelve weeks post-surgery. Micro-CT results showed that mColl:BAp implanted condyles had a slower degradation and an higher tissue formation (17.9 ± 6.9 %) when compared with bColl:Ap implanted ones (12.9 ± 7.6 %). The histomorphometry analysis provided supporting evidence, confirming the observed trend by quantifying 13.1 ± 7.9 % of new tissue formation for mColl:BAp composites and 10.4 ± 3.2 % for bColl:Ap composites, suggesting the potential use of marine biomaterials for bone regeneration.

Finding a needle in a haystack: The identification of clinical practice guidelines for psychosocial oncology through an environmental scan of the academic and gray literature.

OBJECTIVE: Clinical practice guidelines (CPGs) are evidence-based tools well-suited to translate the latest research evidence into recommendations for routine clinical care. Given the rapid expansion of psychosocial oncology research, they represent a key opportunity for informing the treatment decisions of overburdened clinicians, standardizing service delivery, and improving patient-reported outcomes. Yet, there is little consensus on how clinicians can most effectively access these tools and little to no information on the current availability and scope of CPGs for the range of psychosocial symptoms and concerns experienced by patients with cancer. METHOD: Our environmental scan consisted of an academic and gray literature designed to identify currently available CPGs addressing a range of cancer-related psychosocial symptoms. RESULTS: Findings revealed a total of 23 existing psychosocial oncology CPGs that met full eligibility criteria. The gray literature search was found to be more effective at identifying CPGs (n = 22) compared to the academic search (n = 9). CONCLUSION: Several concerns arose from the systematic search. The limited publication of CPGs in peer-reviewed journals may make clinicians and stakeholders more hesitant to implement CPGs due to uncertainties about the methodological rigor of the development process. Further, many existing CPGs are outdated or failed to be updated according to guideline recommendations, meaning that the recommendations may fall short of their purpose to translate up-to-date research findings. FUTURE DIRECTIONS: Future research should seek to systematically assess the quality of existing psychosocial oncology CPGs and shed light on the current state of implementation and adherence in clinical practice in order to better inform guideline developers on the current needs of the psychosocial oncology community.

CAPO and CANO joining forces to advance a national psychosocial oncology advocacy agenda.

Patient advocacy remains a key priority within the Canadian Association of Psychosocial Oncology (CAPO) and the Canadian Association of Nurses in Oncology (CANO). Optimizing collaboration across advocacy organizations, institutions, and other stakeholders is timely as we enter an era where patients and their caregivers' voices are front and centre. In this paper, we report on ongoing efforts to advance patient advocacy - broadly defined as processes and behaviours related to proactively supporting a cause - herein specific to cancer care. Through active partnering, both organizations are well positioned to push for a representative and inclusive national psychosocial oncology advocacy agenda.

Transcriptional programming of translation by BCL6 controls skeletal muscle proteostasis.

Skeletal muscle is dynamically controlled by the balance of protein synthesis and degradation. Here we discover an unexpected function for the transcriptional repressor B cell lymphoma 6 (BCL6) in muscle proteostasis and strength in mice. Skeletal muscle-specific Bcl6 ablation in utero or in adult mice results in over 30% decreased muscle mass and force production due to reduced protein synthesis and increased autophagy, while it promotes a shift to a slower myosin heavy chain fibre profile. Ribosome profiling reveals reduced overall translation efficiency in Bcl6-ablated muscles. Mechanistically, tandem chromatin immunoprecipitation, transcriptomic and translational analyses identify direct BCL6 repression of eukaryotic translation initiation factor 4E-binding protein 1 (Eif4ebp1) and activation of insulin-like growth factor 1 (Igf1) and androgen receptor (Ar). Together, these results uncover a bifunctional role for BCL6 in the transcriptional and translational control of muscle proteostasis.

Definitive hematopoiesis is dispensable to sustain erythrocytes and macrophages during zebrafish ontogeny.

In all organisms studied, from flies to humans, blood cells emerge in several sequential waves and from distinct hematopoietic origins. However, the relative contribution of these ontogenetically distinct hematopoietic waves to embryonic blood lineages and to tissue regeneration during development is yet elusive. Here, using a lineage-specific "switch and trace" strategy in the zebrafish embryo, we report that the definitive hematopoietic progeny barely contributes to erythrocytes and macrophages during early development. Lineage tracing further shows that ontogenetically distinct macrophages exhibit differential recruitment to the site of injury based on the developmental stage of the organism. We further demonstrate that primitive macrophages can solely maintain tissue regeneration during early larval developmental stages after selective ablation of definitive macrophages. Our findings highlight that the sequential emergence of hematopoietic waves in embryos ensures the abundance of blood cells required for tissue homeostasis and integrity during development.