SUMMARY Colony-forming units – fibroblast (CFU-Fs), analogous to those giving rise to bone marrow (BM) mesenchymal stem cells (MSCs), are present in many organs, although the relationship between BM and organ-specific CFU-Fs in homeostasis and tissue repair is unknown. Here we describe a population of adult cardiac-resident CFU-Fs (cCFU-Fs) that occupy a perivascular, adventitial niche and show broad trans-germ layer potency in vitro and in vivo. CRE lineage tracing and embryo analysis demonstrated a proepicardial origin for cCFU-Fs. Furthermore, in BM transplantation chimeras, we found no interchange between BM and cCFU-Fs after aging, myocardial infarction, or BM stem cell mobilization. BM and cardiac and aortic CFU-Fs had distinct CRE lineage signatures, indicating that they arise from different progenitor beds during development. These diverse origins for CFU-Fs suggest an underlying basis for differentiation biases seen in different CFU-F populations, and could also influence their capacity for participating in tissue repair.

Secreted phospholipase B (PLB) activity promotes the survival and replication of Cryptococcus neoformans in macrophages in vitro. We therefore investigated the role of mononuclear phagocytes and cryptococcal PLB in the dissemination of infection in a mouse model, using C. neoformans var. grubii wild-type strain H99, a PLB1 deletion mutant (⌬plb1), and a reconstituted strain (⌬plb1 rec ). PLB facilitated the entry of endotracheally administered cryptococci into lung IM. PLB was also required for lymphatic spread from the lung to regional lymph nodes and for entry into the blood. Langhans-type giant cells containing budding cryptococci were seen free in the lymphatic sinuses of hilar nodes of H99-and ⌬plb1 rec -infected mice, suggesting that they may have a role in the dissemination of cryptococcal infection. The transfer of infected lung macrophages to recipient mice by tail vein injections demonstrated that these cells can facilitate hematogenous dissemination of cryptococci to the brain, independent of cryptococcal PLB secretion. PLB activities of cryptococci isolated from lung macrophages or infected brains were not persistently increased. We conclude that mononuclear phagocytes are a vehicle for cryptococcal dissemination and that PLB activity is necessary for the initiation of interstitial pulmonary infections and for dissemination from the lung via the lymphatics and blood. PLB is not, however, essential for the establishment of neurological infections when cryptococci are presented within, or after passage through, mononuclear phagocytes.Cryptococcus neoformans is a common cause of potentially fatal fungal meningoencephalitis, especially in immunocompromised patients. Primary infections are acquired by inhalation of infectious propagules from environmental sources (1). However, mechanisms by which C. neoformans establishes pulmonary disease and disseminates to the central nervous system (CNS) are not understood.Recent studies using murine models and macrophage-like cell lines have implicated secreted phospholipase B (PLB), the protein produced by the PLB1 gene (5), in intracellular survival, growth, and replication of C. neoformans within macrophages (5,7,15). Furthermore, the persistence of cryptococcal infections has been correlated with the presence of viable cryptococci within macrophages (8, 10). Cryptococcal PLB also enhances pulmonary infections, possibly by inhibiting the development of a protective immune response in the lung, and is required for dissemination to pulmonary lymph nodes and the brain (15). It has been proposed that PLB initiates invasion of the lung interstitium by cryptococci since phospholipids in the pulmonary surfactant and the outer leaflet of mammalian cell membranes are preferred substrates of the enzyme (3, 17). The mechanisms by which cryptococcosis is established in the CNS are unknown, although it has been suggested that cryptococci cross the blood-brain barrier within monocytes or after the penetration of endothelial cells (4) and that CNS infection is associated with su...

We previously demonstrated that human osteosarcoma cells (SAOS‐2) induce contact‐dependent apoptosis in endothelium, and expected similar apoptosis in human gingival fibroblasts (h‐GF) using SAOS‐2 alkaline phosphatase (AP) to identify cells. However, h‐GF apoptosis did not occur, despite reduction in AP‐negative h‐GF number (p < 0.01) and enhancement of this by h‐GF TNFα pretreatment (p < 0.01). We suggest that TNFα‐enhanced transfer of membrane AP from SAOS‐2 to h‐GF would explain these data. This idea was investigated using fluorescence prelabelled cells and confocal laser scanning microscopy. Co‐cultures of membrane‐labelled h‐GF (marker‐DiO) and SAOS‐2 (marker‐DiD) generated dual‐labelled cells, primarily at the expense of single labelled h‐GF (p < 0.001), suggesting predominant membrane transfer from SAOS‐2 to h‐GF. However, opposite directional transfer predominated when membrane labels were reversed; SAOS‐2 further expressed green fluorescent protein (GFP) in cytoplasm and nuclei, and h‐GF additionally bore nuclear label (Syto59) (p < 0.001). Cytoplasmic exchange was investigated using h‐GF prelabelled with cytoplasmic DDAO‐SE and nuclear Syto59, co‐cultured with SAOS‐2 expressing GFP in cytoplasm and nuclei, and predominant cytoplasmic marker transferred from h‐GF to SAOS‐2 (p < 0.05). Pretreating h‐GF with TNFα increased exchange of membrane markers (p < 0.04) but did not affect either cell surface area profile or circularity. Dual‐labelled cells had a morphological phenotype differing from SAOS‐2 and h‐GF (p < 0.001). Time‐lapse microscopy revealed extensive migration of SAOS‐2 and cell process contact with h‐GF, with the appearance of SAOS‐2 indulging in ‘cellular sipping’ from h‐GF. Similar exchange of membrane was seen between h‐GF and with other cell lines (melanoma MeIRMu, NM39, WMM175, MM200‐B12; osteosarcoma U20S; ovarian carcinoma cells PE01, PE04 and COLO316), while cytoplasmic sharing was also seen in all cell lines other than U20S. We suggest that in some neoplasms, cellular sipping may contribute to phenotypic change and the generation of diverse tumour cell populations independent of genetic change, raising the possibility of a role in tumour progression. Copyright © 2012 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.