Recommendations for the organization of the teleconsultation service in a telestroke network.

Telestroke networks aim to improve acute stroke care within their catchment area. Through a teleconsultation service, the network centers provide support to network hospitals that lack continuous neurological expertise for acute stroke management decisions. Although the importance of telemedical treatment in stroke care is steadily increasing, so far no standards exist for the organization of the teleconsultation service in networks.To ensure a high-level of quality for all processes and measures concerning telemedical stroke treatment, the commission for telemedical stroke care of the German Stroke Society (Deutsche Schlaganfall-Gesellschaft, DSG) created the following recommendations on how to organize a teleconsultation service within a telestroke network. The recommendations are the result of an adjustment process between the authors and include guidance on requirements, qualifications, processes and quality management within the teleconsultation service.

Inflammation biomarkers in acute ischemic stroke according to different etiologies.

BACKGROUND: High throughput technologies provide new opportunities to further investigate the pathophysiology of ischemic strokes. The present cross-sectional study aimed to evaluate potential associations between the etiologic subtypes of ischemic stroke and blood-based proteins. METHODS: We investigated the associations between ischemic stroke subtypes and a panel of circulating inflammation biomarkers in 364 patients included in the Stroke Cohort Augsburg (SCHANA). Stroke etiologies were categorized according to the TOAST (Trial of Org 10172 in Acute Stroke Treatment) classification. Serum concentrations of 52 biomarkers were measured using the Bio-Plex Pro™ Human Cytokine Screening Panel, ICAM-1 set and VCAM-1 set, plus the Pro™ Human TH17 cytokine sCD40L set and IL31 set (all Bio-Rad, USA). Multivariable linear regression models were used to examine associations. Point estimates were calculated as the mean difference in σ -standardized cytokine levels on the log2 -scale. RESULTS: Stromal-cell-derived-factor 1 alpha (SDF-1a) showed significantly higher serum levels in cardioembolic compared with large vessel atherosclerotic stroke (ß = 0.48; 95% CI 0.22; 0.75; Padj = 0.036). Significantly lower levels of interleukin-6 (IL-6) (ß = -0.53; 95% CI -0.84; -0.23; Padj = 0.036) and macrophage migration inhibitory factor (MIF) (ß = -0.52; 95% CI -0.84; -0.21; Padj = 0.043) were found in the small vessel versus large vessel stroke subtype. CONCLUSIONS: Immune dysregulations observed in different stroke subtypes might help uncover pathophysiological mechanisms of the disease. Further studies are needed to validate identified biomarkers in diverse study populations before they can potentially be used in clinical practice to further improve stroke management and patient outcomes.

Association of post-stroke-depression and health-related quality of life three months after the stroke event. Results from the Stroke Cohort Augsburg (SCHANA) study.

Approximately one-third of patients with stroke show depressive symptoms. The so-called post-stroke depression (PSD) has a negative influence on mortality as well as physical and mental conditions. The aim of this study was to analyse the association between PSD and health-related quality of life (HRQOL) in patients with stroke. The analysis was based on data of 326 patients from the Stroke Cohort Augsburg (SCHANA Study) collected after the stroke event by interview and three months later using a postal survey. Depressive symptoms were measured with the Patient-Health Questionnaire (PHQ-9), subjective health status with the EuroQol 5D visual analogue scale (EQ-5D VAS), and HRQOL with the Stroke Impact Scale (SIS). Patients with depressive symptoms were compared to those without depressive symptoms in terms of sociodemographic characteristics and scores of the SIS and the EQ-5D VAS. Multiple linear regression models were calculated to investigate the association between PSD and subjective health status and HRQOL. Three months after the stroke, 17.8% of patients had depressive symptoms. Patients with PSD showed significantly worse SIS and EQ-5D VAS scores. In addition, an independent negative linear association between PSD and subjective health status and between PSD and all domains of SIS could be found. The study confirmed that PSD is common in patients with mild stroke and negatively related to all stroke-specific HRQOL domains. The results underline the importance of early screening for PSD in stroke patients since it may hinder a successful rehabilitation.

Influence of educational status and migration background on the long-term health-related quality of life after stroke.

BACKGROUND AND PURPOSE: Acute stroke treatment and secondary prevention have tremendously improved functional outcomes after stroke. However, this does not always imply a likewise improvement in health-related quality of life (HRQoL). Knowledge on factors influencing HRQoL after stroke is still scarce, especially regarding social aspects like the level of education and the presence of migration background. METHODS: In the present stroke cohort study, participants were interviewed during their hospital stay and completed a postal questionnaire at 3 and 12 months post stroke. Functional outcomes were assessed by the modified Rankin Scale and HRQoL by evaluating the detailed Stroke Impact Scale (SIS). Logistic regression models were used to determine associations between education, migration background and quality of life end-points. RESULTS: A total of 945 (mean age 69 years; 56% male) stroke patients were enrolled. After adjusting for confounders, a lower educational level was associated with worse functional outcomes in the SIS domain 'strength' (odds ratio 2.67, 95% confidence interval 1.6-4.4, p < 0.001). Migration background was associated with worse outcomes in the SIS domain 'emotion' (p = 0.007, odds ratio 1.71, 95% confidence interval 1.2-2.5). Additionally, for female patients worse HRQoL outcomes were found in multiple other SIS domains. CONCLUSIONS: Migration background and a lower educational level were significantly associated with lower long-term HRQoL after stroke. These aspects should be considered in targeted rehabilitation programmes and follow-up support of stroke patients.

Associations between pre-stroke physical activity and physical quality of life three months after stroke in patients with mild disability.

BACKGROUND: Much is known about the association between physical activity and the occurrence of stroke. However, the evidence about the correlation between pre-stroke physical activity and post-stroke quality of life remains inconsistent. Thus, there is a high public health relevance to the topic. AIM: The aim of this study was to investigate the association between pre-stroke physical activity and physical quality of life after three months. METHODS: Data arises from 858 patients with stroke included a prospective single-centre observational cohort study in Augsburg, Germany, between September 2018 and November 2019. The participants were recruited at the Department of Neurology and Clinical Neurophysiology, University Hospital of Augsburg after their stroke event. The level of physical activity was determined following the short form of the International Physical Activity Questionnaire at baseline. Physical quality of life was assessed three months after hospital discharge using the German version of the Stroke Impact Scale (SIS). A multiple linear regression model and a quantile regression were carried out. RESULTS: A total of 497 patients were included in the analysis (mean age 69.6, 58.8% male), 26.2% had a high, 18.9% a moderate and 54.9% a low level of pre-stroke physical activity. Patients with high pre-stroke physical activity had a significantly better physical quality of life three months after stroke in the SIS physical domain (beta = 4.1) and in the SIS subdomains hand function (beta = 5.6), mobility (beta = 4.1) and activities of daily living (beta = 3.7). In the physical domain and the subdomain mobility, the effect was especially strong for persons with low physical quality of life after three months. CONCLUSION: Pre-stroke physical activity seems to have an important and positive association with physical quality of life after three months in patients with mild disability. Further studies are needed to confirm these results.

Factors Associated With Early and Late Post-stroke Fatigue in Patients With Mild Impairment. Results From the Stroke Cohort Study Augsburg.

Background: Post-stroke fatigue is a common symptom after stroke. However, studies on the factors associated with early and late fatigue are scarce. The objective of this study was to identify variables associated with early and late fatigue. Methods: In the German Stroke Cohort Augsburg (SCHANA) study, participants were interviewed during their hospital stay and completed a postal questionnaire 3 and 12 months post-stroke. Fatigue was assessed using the Fatigue Assessement Scale (FAS). In addition, depression was measured by the Patient Health Questionnaire (PHQ-9), general health status by the EQ-5D visual analog scale, and physical activity by the International Physical Activity Questionnaire (IPAQ). Multivariable regression models were used to determine the associations between FAS scores at 3 and 12 months post-stroke and demographic, psychosocial and health-related covariables. Results: Among 505 participants, the frequency of fatigue was 31.1% 3 months and 29.1% 12 months post-stroke. Prior stroke (ß = 2.37, p = 0.0076), prior diagnosis of depression (ß = 5.04, p = 0.0001), higher NIHSS (ß = 0.25, p = 0.0360) and higher PHQ-9 scores (ß = 0.55, p < 0.0001) were significantly associated with higher fatigue levels 3 months post-stroke. Additionally, younger age (ß = -0.07, p = 0.0219), a worse rating of general health at baseline (ß = -0.04, p = 0.0287) and low pre-stroke physical activity (ß = -0.0004, p = 0.0089) were significantly associated with higher fatigue levels 12 months after stroke. Conclusions: Fatigue is a common and persisting symptom even in patients with mild impairment. Prior depressive disorder and early depressive symptoms were the most relevant predictors of both early and late fatigue.

Simulation-based training improves process times in acute stroke care (STREAM).

BACKGROUND: The objective of the STREAM Trial was to evaluate the effect of simulation training on process times in acute stroke care. METHODS: The multicenter prospective interventional STREAM Trial was conducted between 10/2017 and 04/2019 at seven tertiary care neurocenters in Germany with a pre- and post-interventional observation phase. We recorded patient characteristics, acute stroke care process times, stroke team composition and simulation experience for consecutive direct-to-center patients receiving intravenous thrombolysis (IVT) and/or endovascular therapy (EVT). The intervention consisted of a composite intervention centered around stroke-specific in situ simulation training. Primary outcome measure was the 'door-to-needle' time (DTN) for IVT. Secondary outcome measures included process times of EVT and measures taken to streamline the pre-existing treatment algorithm. RESULTS: The effect of the STREAM intervention on the process times of all acute stroke operations was neutral. However, secondary analyses showed a DTN reduction of 5 min from 38 min pre-intervention (interquartile range [IQR] 25-43 min) to 33 min (IQR 23-39 min, p = 0.03) post-intervention achieved by simulation-experienced stroke teams. Concerning EVT, we found significantly shorter door-to-groin times in patients who were treated by teams with simulation experience as compared to simulation-naive teams in the post-interventional phase (-21 min, simulation-naive: 95 min, IQR 69-111 vs. simulation-experienced: 74 min, IQR 51-92, p = 0.04). CONCLUSION: An intervention combining workflow refinement and simulation-based stroke team training has the potential to improve process times in acute stroke care.

Association between fatigue and cytokine profiles in patients with ischemic stroke.

Background: Chronic fatigue is a common symptom after a stroke. Studies suggested that chronic fatigue is caused by inflammatory or immunological processes but data are limited and contradictory. Thus, the present study aimed to identify specific biomarkers associated with fatigue in post-stroke patients and replicated the findings in a population-based study. Methods: We investigated associations between 39 circulating biomarkers of inflammation and fatigue in 327 patients after an ischemic stroke included in the Stroke Cohort Augsburg (SCHANA) study and the "Metabolism, Nutrition and Immune System in Augsburg" (MEIA) study (n = 140). The Fatigue Assessment Scale (FAS) was used to assess the severity of fatigue. The serum concentrations of the biomarkers were measured using the Bio-Plex Pro™ Human Cytokine Screening Panel (Bio-Rad, USA). Multiple linear regression models adjusted for possible confounders were used to examine associations. Results: In patients with stroke, SCGFb was inversely associated [-1.67, 95% confidence interval (CI) (-3.05; -0.29) p = 0.018], and in healthy subjects, G-CSF was positively associated [1.56, 95% CI (0.26; 2.87), p = 0.020] with an increasing FAS-score, while SCF was positively related in both samples [1.84, 95% CI (0.27; 3.42), p = 0.022 and 1.40, 95% CI (0.29; 2.52), p = 0.015]. However, after correction for multiple testing, all of these associations lost statistical significance. Conclusion: The present findings suggested an association between the growth factor SCF and fatigue. Future research on cytokines as possible markers of fatigue should focus on a longitudinal design including a sufficiently large number of study participants to enable testing associations between certain cytokines and sub-groups of chronic fatigue.

Changes of Health-Related Quality of Life Within the 1st Year After Stroke-Results From a Prospective Stroke Cohort Study.

Introduction: As prospective data on long-term patient-reported outcome measures (PROMs) to assess Health related Quality of Life (HRQoL) after stroke are still scarce, this study examined the long-term course of PROMs and investigated influential factors such as recanalization therapies. Materials and Methods: A total of 945 (mean age 69 years; 56% male) stroke patients were enrolled with a personal interview and chart review performed at index event. One hundred forty (15%) patients received thrombolysis (IVT) and 53 (5%) patients received endovascular therapy (ET) or both treatments as bridging therapy (BT). After 3 and 12 months, a follow-up was conducted using a postal questionnaire including subjective quality of life EQ-5D-5L (European Quality of Life 5 Dimensions). At all time-points, Modified Rankin Scale (mRS) was additionally used to quantify functional stroke severity. Differences between therapy groups were identified using post-hoc-tests. Linear and logistic regression analyses were used to identify predictors of outcomes. Results: Recanalization therapies were associated with significant improvements of NIHSS (National Institutes of Health Stroke Scale [regression coefficient IVT 1.21 (p = 0.01) and ET/BT 7.6; p = 0.001] and mRS (modified Rankin Scale) [regression coefficient IVT 0.83; p = 0.001 and ET/BT 2.0; p = 0.001] between admission and discharge compared to patients with stroke unit therapy only, with a trend toward improvement of EQ-5D after 12 months [regression coefficient 4.67 (p = 0.17)] with IVT. HRQoL was considerably impaired by stroke and increased steadily in 3- and 12-months follow-up in patients with (mean EQ-5D from 56 to 68) and without recanalization therapy (mean EQ-5D from 62 to 68). In severe strokes a major and significant improvement was only detected during period of 3 to 12 months (p = 0.03 in patients with and p = 0.005 in patients without recanalization therapy). Conclusions: Despite significant and continuous improvements after stroke the HRQoL after 12 months remained below the age-matched general population, but was still unexpectedly high in view of the accumulation of permanent disabilities in up to 30% of the patients. Especially in severe strokes, it is important to evaluate HRQoL beyond a 3-months follow-up as improvements became significant only between 3 months and 1 year.

Impact of the coronavirus disease 2019 pandemic on stroke teleconsultations in Germany in the first half of 2020.

BACKGROUND AND PURPOSE: The effects of the coronavirus disease 2019 (COVID-19) pandemic on telemedical care have not been described on a national level. Thus, we investigated the medical stroke treatment situation before, during, and after the first lockdown in Germany. METHODS: In this nationwide, multicenter study, data from 14 telemedical networks including 31 network centers and 155 spoke hospitals covering large parts of Germany were analyzed regarding patients' characteristics, stroke type/severity, and acute stroke treatment. A survey focusing on potential shortcomings of in-hospital and (telemedical) stroke care during the pandemic was conducted. RESULTS: Between January 2018 and June 2020, 67,033 telemedical consultations and 38,895 telemedical stroke consultations were conducted. A significant decline of telemedical (p < 0.001) and telemedical stroke consultations (p < 0.001) during the lockdown in March/April 2020 and a reciprocal increase after relaxation of COVID-19 measures in May/June 2020 were observed. Compared to 2018-2019, neither stroke patients' age (p = 0.38), gender (p = 0.44), nor severity of ischemic stroke (p = 0.32) differed in March/April 2020. Whereas the proportion of ischemic stroke patients for whom endovascular treatment (14.3% vs. 14.6%; p = 0.85) was recommended remained stable, there was a nonsignificant trend toward a lower proportion of recommendation of intravenous thrombolysis during the lockdown (19.0% vs. 22.1%; p = 0.052). Despite the majority of participating network centers treating patients with COVID-19, there were no relevant shortcomings reported regarding in-hospital stroke treatment or telemedical stroke care. CONCLUSIONS: Telemedical stroke care in Germany was able to provide full service despite the COVID-19 pandemic, but telemedical consultations declined abruptly during the lockdown period and normalized after relaxation of COVID-19 measures in Germany.

Long-Term Outcomes in Patients with Stroke after in-Hospital Treatment-Study Protocol of the Prospective Stroke Cohort Augsburg (SCHANA Study).

INTRODUCTION: In Germany, stroke is the third leading cause of death, with more than 60,000 fatalities out of approximately 260,000 cases (first-ever and recurrent strokes) each year. So far, there are only a few long-term studies investigating determinants of the natural course of the disease, especially in the era of mechanical thrombectomy. MATERIALS AND METHODS: The prospective single-center stroke cohort Augsburg (SCHANA) study will include about 1000 patients treated for stroke in the University Hospital of Augsburg. Patients aged 18 years or older with a confirmed diagnosis of ischemic or hemorrhagic stroke are included in the study. Information on demographic characteristics, onset of symptoms, etiologic factors, comorbidities, quality of life, invasive and non-invasive treatment, complications, and laboratory parameters are collected during a personal interview conducted during the patients' hospital stay and via a medical chart review. About 30 mL of blood is collected from each patient, and after processing and aliquoting, all blood specimens are frozen at -80° C. The study participants will be followed-up via postal questionnaires at three and 12 months after discharge from the hospital. Furthermore, mortality follow-ups will be conducted. Cox-regression analysis will be used to estimate relative risks. CONCLUSION: The SCHANA study will generate comprehensive data on the long-term course of the disease. In addition to the main outcomes, recurrent events and survival, patient-oriented outcomes such as health-related quality of life and depression are the focus of the study.

Simulation-Based Training of the Rapid Evaluation and Management of Acute Stroke (STREAM)-A Prospective Single-Arm Multicenter Trial.

Introduction: Acute stroke care delivered by interdisciplinary teams is time-sensitive. Simulation-based team training is a promising tool to improve team performance in medical operations. It has the potential to improve process times, team communication, patient safety, and staff satisfaction. We aim to assess whether a multi-level approach consisting of a stringent workflow revision based on peer-to-peer review and 2-3 one-day in situ simulation trainings can improve acute stroke care processing times in high volume neurocenters within a 6 months period. Methods and Analysis: The trial is being carried out in a pre-test-post-test design at 7 tertiary care university hospital neurocenters in Germany. The intervention is directed at the interdisciplinary multiprofessional stroke teams. Before and after the intervention, process times of all direct-to-center stroke patients receiving IV thrombolysis (IVT) and/or endovascular therapy (EVT) will be recorded. The primary outcome measure will be the "door-to-needle" time of all consecutive stroke patients directly admitted to the neurocenters who receive IVT. Secondary outcome measures will be intervention-related process times of the fraction of patients undergoing EVT and effects on team communication, perceived patient safety, and staff satisfaction via a staff questionnaire. Interventions: We are applying a multi-level intervention in cooperation with three "STREAM multipliers" from each center. First step is a central meeting of the multipliers at the sponsor's institution with the purposes of algorithm review in a peer-to-peer process that is recorded in a protocol and an introduction to the principles of simulation training and debriefing as well as crew resource management and team communication. Thereafter, the multipliers cooperate with the stroke team trainers from the sponsor's institution to plan and execute 2-3 one-day simulation courses in situ in the emergency department and CT room of the trial centers whereupon they receive teaching materials to perpetuate the trainings. Clinical Trial Registration: STREAM is a registered trial at https://clinicaltrials.gov/ct2/show/NCT03228251.

Differential patterns of local gene regulation in crush lesions of the rat optic and sciatic nerve: relevance to posttraumatic regeneration.

Axon regrowth after nerve injury can occur in the peripheral but fails in the central nervous system. Cellular reactions at the lesion site affect axonal regrowth. We compared gene regulation in optic nerve (ON) and sciatic nerve (SN) crush lesions in adult rats by cDNA array analysis, quantitative RT-PCR and immunohistochemistry, focusing on the primary lesion site rather than the proximal or distal nerve stump. Four days after injury, identical gene regulation in ON and SN lesions was found for 19/1185 genes (15 up, 4 down). In contrast, tissue-specific regulations were identified for 48 genes in ON and 50 genes in SN crush lesions. Among these, in the ON many genes were downregulated (23 up, 25 down) whereas upregulation predominated in SN lesions (43 up, 7 down), especially for signaling, metabolism, and translation/transcription-related genes. In ON lesions aquaporin 4 downregulation corresponded to a transient loss of astrocytes. Tissue-type plasminogen activator was upregulated in the lesion and distal stump of SN while the urokinase-type plasminogen activator was upregulated only in the ON lesion indicating differences in local proteolysis between the systems. Typical neuronal genes were regulated at the crush site comprising neurotransmitter genes in ON and actin cytoskeleton-related genes in the SN. The differential orchestration of local gene regulation has implications for axonal regeneration in central nervous system lesions.

p57kip2 is dynamically regulated in experimental autoimmune encephalomyelitis and interferes with oligodendroglial maturation.

The mechanisms preventing efficient remyelination in the adult mammalian central nervous system after demyelinating inflammatory diseases, such as multiple sclerosis, are largely unknown. Partial remyelination occurs in early disease stages, but repair capacity diminishes over time and with disease progression. We describe a potent candidate for the negative regulation of oligodendroglial differentiation that may underlie failure to remyelinate. The p57kip2 gene is dynamically regulated in the spinal cord during MOG-induced experimental autoimmune encephalomyelitis. Transient down-regulation indicated that it is a negative regulator of post-mitotic oligodendroglial differentiation. We then applied short hairpin RNA-mediated gene suppression to cultured oligodendroglial precursor cells and demonstrated that down-regulation of p57kip2 accelerates morphological maturation and promotes myelin expression. We also provide evidence that p57kip2 interacts with LIMK-1, implying that p57kip2 affects cytoskeletal dynamics during oligodendroglial maturation. These data suggest that sustained down-regulation of p57kip2 is important for oligodendroglial maturation and open perspectives for future therapeutic approaches to overcome the endogenous remyelination blockade in multiple sclerosis.

Increased thalamic neurodegeneration following ischaemic cortical stroke in osteopontin-deficient mice.

Inflammation aggravates brain injury caused by stroke and neurodegeneration. Osteopontin (OPN) is a cytokine-like glycoprotein that binds to various integrins and CD44 variants. OPN exerts proinflammatory effects in autoimmune conditions but also has cytoprotective properties and participates in wound healing. In this study, we addressed the role of OPN in ischaemic brain injury using OPN knock-out (KO) mice in models of cortical stroke. Compared with wild-type animals, OPN KO mice exhibited unaltered infarct development at the primary injury site but greatly increased retrograde degeneration of the ipsilateral thalamus. Thalamic neurodegeneration in OPN-deficient mice was associated with pronounced microglia activation and inflammatory gene expression and could be attenuated via pharmacological blockade of the inducible nitric oxide synthase (iNOS). Therefore, delayed neurodegeneration in OPN-deficient mice was at least partly due to an excessive release of nitric oxide via the iNOS pathway. Neuroprotective and anti-inflammatory effects of OPN may be relevant for a variety of neurological disease conditions.

Hematopoietic stem cell transplantation prevents diabetes in NOD mice but does not contribute to significant islet cell regeneration once disease is established.

The treatment of type I diabetes by islet cell transplantation, while promising, remains restricted due to the incomplete efficacy and toxicity associated with current immunosuppression, and by limited organ availability. Given reports suggesting bone marrow derived stem cell plasticity, we sought to determine whether such cells could give rise to pancreatic islet cells in vivo. In the context of autoimmune diabetes, we transplanted unfractionated bone marrow from beta-gal trangenic donor mice into NOD mice prior to, at, and two weeks beyond the onset of disease. Successful bone marrow engraftment before diabetes onset prevented disease in all mice and for 1 year after transplant. However, despite obtaining full hematopoietic engraftment in over 50 transplanted mice, only one mouse became insulin independent, and no beta-Gal positive islets were detected in any of the mice. To test whether tolerance to islets was achieved, we injected islets obtained from the same allogeneic donor strain as the hematopoietic cells into 4 transplant recipients, and 2 had a reversion of their diabetes. Thus allogeneic bone marrow transplantation prevents autoimmune diabetes and tolerizes the recipient to donor islet grants, even in diabetic animals, yet the capacity of bone marrow derived cells to differentiate into functional islet cells, at least without additional manipulation, is limited in our model.

Osteopontin, a macrophage-derived matricellular glycoprotein, inhibits axon outgrowth.

Transected axons can regenerate beyond the site of injury in the peripheral but not in the central nervous system (CNS). Increasing evidence implicates inflammatory processes as modulators of axon regeneration after injury. In this study, we addressed a possible role of the matricellular glycoprotein osteopontin (OPN) using crush lesions of the optic and sciatic nerve as models of central and peripheral axotomy, respectively. OPN was strongly expressed by macrophages at the crush site in the optic but not sciatic nerve, indicating fundamental differences in the molecular programming of macrophages in both systems. Functionally, OPN exerted potent growth-inhibitory effects in an in vitro assay of axon outgrowth. Therefore, OPN expression by lesion-associated macrophages may contribute to the nonpermissive nature of the adult CNS preventing axonal regeneration following injury.

Polyclonal long-term repopulating stem cell clones in a primate model.

Hematopoietic bone marrow stem cells generate differentiated blood cells and, when transplanted, may contribute to other organs, such as the brain, heart, and liver. An understanding of in vivo clonal behavior of stem cells will have important implications for cellular and gene therapy. For the first time, we have directly demonstrated the derivation of circulating peripheral blood cells from individual stem cell clones. We analyzed the clonal composition of retrovirus-marked peripheral blood leukocyte populations in 2 different primate models by a novel direct genomic sequencing technique allowing the identification of vector insertion sites. More than 80 contributing long-term hematopoietic clones were identified in individual rhesus macaque peripheral blood transplant recipients and more than 25 different clones in a baboon marrow transplant recipient. Up to 5 insertion sequences from each animal were used to trace the long-term contribution of stem cell clones in these primate models. Continuous and mostly pluripotent contributions of peripheral blood leukocytes from each of the traced clones could be detected for the entire follow-up period of 23 to 33 months. Our study provides direct molecular evidence for a polyclonal, multilineage, and sustained contribution of individual stem cells to primate hematopoiesis.