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.

In situ mapping identifies distinct vascular niches for myelopoiesis

In contrast to nearly all other tissues, the anatomy of cell differentiation in the bone marrow remains unknown. This is owing to a lack of strategies for examining myelopoiesis-the differentiation of myeloid progenitors into a large variety of innate immune cells-in situ in the bone marrow. Such strategies are required to understand differentiation and lineage-commitment decisions, and to define how spatial organizing cues inform tissue function. Here we develop approaches for imaging myelopoiesis in mice, and generate atlases showing the differentiation of granulocytes, monocytes and dendritic cells. The generation of granulocytes and dendritic cells-monocytes localizes to different blood-vessel structures known as sinusoids, and displays lineage-specific spatial and clonal architectures. Acute systemic infection with Listeria monocytogenes induces lineage-specific progenitor clusters to undergo increased self-renewal of progenitors, but the different lineages remain spatially separated. Monocyte-dendritic cell progenitors (MDPs) map with nonclassical monocytes and conventional dendritic cells; these localize to a subset of blood vessels expressing a major regulator of myelopoiesis, colony-stimulating factor 1 (CSF1, also known as M-CSF)¹. Specific deletion of Csf1 in endothelium disrupts the architecture around MDPs and their localization to sinusoids. Subsequently, there are fewer MDPs and their ability to differentiate is reduced, leading to a loss of nonclassical monocytes and dendritic cells during both homeostasis and infection. These data indicate that local cues produced by distinct blood vessels are responsible for the spatial organization of definitive blood cell differentiation.

Professional attitudes toward denture adhesives: A Delphi technique survey of academic prosthodontists

STATEMENT OF PROBLEM

The use of denture adhesives and their role in prosthodontics has been an intriguing and conflicted topic, both in clinical practice and dental education.

PURPOSE

This study generated discussion, and if possible, obtained a consensus on a series of issues related to denture adhesives among a group of leading academic prosthodontists.

MATERIAL AND METHODS

The Delphi Technique survey method was used. It consists of a series of survey questionnaire rounds to a panel of experts to either develop a consensus (>70% agreement) or to clarify the reasons for multiple schools of thought on a topic. A 24-item Delphi questionnaire was sent to an expert panel that consisted of a 33% regionally stratified random sample of program directors of undergraduate complete denture courses in US dental schools. The 5 major topic areas on denture adhesives addressed by the questionnaire items were (1) general perceptions, (2) specific clinical uses/misuses, (3) patient education, (4) inclusion in dental curricula, and (5) overall opinions of utility.

RESULTS

Of the 18 randomly selected panelists, 94% (n = 17) agreed to participate, with either 16 or 17 fully participating in each of the 3 survey rounds. The panel achieved consensus and clearly concluded that denture adhesives: (1) are a useful adjunct in denture prosthesis services, having specific roles in both the fabrication and postinsertion phases; (2) had the potential for misuse, both by dentists and by patients; and (3) should be an integral part of patient education for all denture patients and of the undergraduate dental curriculum. However, the panel was unable to achieve consensus on whether denture adhesives should be used at the postinsertion phase for immediate denture patients and whether, on the whole, they were a beneficial adjunct in denture patient management (59% agreed they were). The panelists also clearly expressed their concerns that neither dentists nor patients should use denture adhesives as a substitute for either good clinical practices or proper denture maintenance routines.

CONCLUSIONS

This panel of leading academic prosthodontists concluded that denture adhesives are a useful adjunct in denture prosthesis services, with specific roles in both fabrication and postinsertion phases. They also indicated that only through education, for dentists and patients, would the dual goals of maximizing the beneficial aspects of denture adhesive use while minimizing the misuse of denture adhesives be achieved.