Resilient anatomy and local plasticity of naive and stress haematopoiesis.

The bone marrow adjusts blood cell production to meet physiological demands in response to insults. The spatial organization of normal and stress responses are unknown owing to the lack of methods to visualize most steps of blood production. Here we develop strategies to image multipotent haematopoiesis, erythropoiesis and lymphopoiesis in mice. We combine these with imaging of myelopoiesis1 to define the anatomy of normal and stress haematopoiesis. In the steady state, across the skeleton, single stem cells and multipotent progenitors distribute through the marrow enriched near megakaryocytes. Lineage-committed progenitors are recruited to blood vessels, where they contribute to lineage-specific microanatomical structures composed of progenitors and immature cells, which function as the production sites for each major blood lineage. This overall anatomy is resilient to insults, as it was maintained after haemorrhage, systemic bacterial infection and granulocyte colony-stimulating factor (G-CSF) treatment, and during ageing. Production sites enable haematopoietic plasticity as they differentially and selectively modulate their numbers and output in response to insults. We found that stress responses are variable across the skeleton: the tibia and the sternum respond in opposite ways to G-CSF, and the skull does not increase erythropoiesis after haemorrhage. Our studies enable in situ analyses of haematopoiesis, define the anatomy of normal and stress responses, identify discrete microanatomical production sites that confer plasticity to haematopoiesis, and uncover unprecedented heterogeneity of stress responses across the skeleton.

Diabéticos devem ter a artéria torácica interna esqueletizada? Avaliação da perfusão esternal por cintilografia / Should the diabetics have the internal thoracic artery skeletonized? Assessment of sternal perfusion by scintillography

OBJETIVO: Avaliar o impacto na vascularização do esterno, por cintilografia óssea, da utilização de ambas as artérias torácicas internas (ATIs), preparadas por duas técnicas diferentes. MÉTODOS: Trinta e cinco pacientes coronarianos foram divididos em dois grupos: Grupo A - 18 pacientes tiveram as duas ATIs dissecadas de forma esqueletizada; Grupo B - 17 pacientes tiveram as duas ATIs dissecadas pela técnica pediculada. Não houve diferença nos dois grupos com relação a gênero, idade e características demográficas. Realizou-se cintilografia óssea 7 dias após a cirurgia. A análise estatística foi realizada utilizando-se o teste de t de Student. com significância estabelecida em 95 por cento. RESULTADOS: No grupo A (ATI esqueletizada), o nível de captação do esterno foi de 11,5 por cento mais alto em comparação com a média dos 17 pacientes do grupo B (ATI pediculada), mas essa diferença não foi estatisticamente significante (P = 0,127). Entretanto, a média dos níveis de captação do esterno nos sete pacientes diabéticos do Grupo A (ATI esqueletizada) foi 47,4 por cento mais alta em comparação à média dos sete pacientes diabéticos do grupo B (ATI pediculada), e esta diferença foi estatisticamente significante (P = 0,004). CONCLUSÃO: 1- A forma de dissecção das ATIs não altera de maneira estatisticamente significativa a perfusão esternal, avaliada por cintilografia óssea, no conjunto geral da população estudada. 2- No subgrupo de pacientes diabéticos, observou-se melhor perfusão do esterno nos pacientes submetidos à dissecção esqueletizada. Embora a confirmação desse achado num maior número de casos seja necessária, pacientes diabéticos devem ter as artérias torácicas internas dissecadas de forma esqueletizada.

OBJECTIVE: To assess, by scintillography, the effect of using bilateral internal thoracic arteries (BITAs) - prepared by two different techniques - on the sternal perfusion. METHODS: 35 patients undergone coronary artery bypass grafting (CABG) were divided into two groups: Group A (18) had both ITA's dissected using skeletonization technique and group B (17) as pedicle preparation. There was no difference in the two groups relating gender, age and demographic characteristics. On the 7th postoperative day the patients underwent bone scintillography. The statistical analysis was performed using the Student's t test with 95 percent significance. RESULTS: Group A (skeletonized ITA) showed higher perfusion (11.5 percent) of the sternum as a mean, than Group B (pedicled ITA) patients; however this was not statistically significant (P = 0.127). On the other hand, comparing the diabetic population, seven in each group, there was a marked 47.4 percent higher perfusion of the sternum in Group A patients (skeletonized ITA) comparing to Group B (pedicled ITA) and this difference reached statistical significance (P = 0.004). CONCLUSION: 1- Sternal perfusion is not affected significantly apart from the dissection technique used for both internal thoracic arteries in the general population when assessed by bone scintillography. 2 - In the diabetic subgroup, a significant preservation of the sternal perfusion was observed in patients undergone skeletonized dissection of the internal thoracic arteries. Although these findings should be confirmed in a greater number of cases, diabetic patients should have the internal thoracic arteries dissected using skeletonization techinque.