Bone marrow fibrosis represents an important structural change in the marrow that interferes with some of its normal functions. The aetiopathogenesis of fibrosis is not well established except in its primary form. The present review consolidates current understanding of marrow fibrosis. We searched PubMed without time restriction using key words: bone marrow and fibrosis as the main stem against the terms: growth factors, cytokines and chemokines, morphology, megakaryocytes and platelets, myeloproliferative disorders, myelodysplastic syndrome, collagen biosynthesis, mesenchymal stem cells, vitamins and minerals and hormones, and mechanism of tissue fibrosis. Tissue marrow fibrosis-related papers were short listed and analysed for the review. It emerged that bone marrow fibrosis is the outcome of complex interactions between growth factors, cytokines, chemokines and hormones together with their facilitators and inhibitors. Fibrogenesis is initiated by mobilisation of special immunophenotypic subsets of mesenchymal stem cells in the marrow that transform into fibroblasts. Fibrogenic stimuli may arise from neoplastic haemopoietic or non-hematopoietic cells, as well as immune cells involved in infections and inflammatory conditions. Autoimmunity is involved in a small subset of patients with marrow fibrosis. Megakaryocytes and platelets are either directly involved or are important intermediaries in stimulating mesenchymal stem cells. MMPs, TIMPs, TGF-β, PDGRF, and basic FGF and CRCXL4 chemokines are involved in these processes. Genetic and epigenetic changes underlie many of these conditions.

The 2022 Annual Review Issue of The Journal of Pathology, Recent Advances in Pathology, contains 15 invited reviews on research areas of growing importance in pathology. This year, the articles include those that focus on digital pathology, employing modern imaging techniques and software to enable improved diagnostic and research applications to study human diseases. This subject area includes the ability to identify specific genetic alterations through the morphological changes they induce, as well as integrating digital and computational pathology with \'omics technologies. Other reviews in this issue include an updated evaluation of mutational patterns (mutation signatures) in cancer, the applications of lineage tracing in human tissues, and single cell sequencing technologies to uncover tumour evolution and tumour heterogeneity. The tissue microenvironment is covered in reviews specifically dealing with proteolytic control of epidermal differentiation, cancer-associated fibroblasts, field cancerisation, and host factors that determine tumour immunity. All of the reviews contained in this issue are the work of invited experts selected to discuss the considerable recent progress in their respective fields and are freely available online (https://onlinelibrary.wiley.com/journal/10969896). © 2022 The Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

The dynamical process of cell division that underpins homeostasis in the human body cannot be directly observed in vivo, but instead is measurable from the pattern of somatic genetic or epigenetic mutations that accrue in tissues over an individual\'s lifetime. Because somatic mutations are heritable, they serve as natural lineage tracing markers that delineate clonal expansions. Mathematical analysis of the distribution of somatic clone sizes gives a quantitative readout of the rates of cell birth, death, and replacement. In this review we explore the broad range of somatic mutation types that have been used for lineage tracing in human tissues, introduce the mathematical concepts used to infer dynamical information from these clone size data, and discuss the insights of this lineage tracing approach for our understanding of homeostasis and cancer development. We use the human colon as a particularly instructive exemplar tissue. There is a rich history of human somatic cell dynamics surreptitiously written into the cell genomes that is being uncovered by advances in sequencing and careful mathematical analysis lineage of tracing data. © 2022 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

Over the last five years significant progress has been made towards the transfer of foreign genetic material to eukaryotic cells. The eventual aim to devise novel therapeutic strategies to treat human diseases, in particular solid tumours and monogenic disorders associated with various enzyme deficiency states. The easy accessibility and the ability of haemopoetic stem cells to self replicate and repopulate makes them desirable targets for gene transfer. In theory the introduction of a small number of gene modifed haemopoetic progenitor cells can allow therapy of an individual for life without any further intervention. This approach has been used for the treatment of single gene defects such as ADA deficiency. Furthermore, gene transfer technology has increasingly been exploited for bone marrow and peripheral blood stem cell marking studies, modification of cell sensitivity to cytotoxic drugs and the genetic modification of leukemic cells with the intention of inducing a leukemia specific cytotoxic T cell response. Vector development is of crucial importance for the successful delivery of genes in haemopoetic stem cells and leukemia cells. The objective of this review is to discuss in detail the properties of current vector technology that are pertinent to haemopoietic cell gene transduction.