Darren J Day

Expression of components of the renin-angiotensin system in proliferating infantile haemangioma may account for the propranolol-induced accelerated involution.

Infantile haemangioma is a benign tumour of the microvasculature characterised by excessive proliferation of immature endothelial cells. It typically undergoes rapid proliferation during infancy followed by spontaneous slow involution during childhood often leaving a fibro-fatty residuum. In 2008, propranolol, a non-selective β-blocker, was serendipitously discovered to induce accelerated involution of a proliferating infantile haemangioma. However, the mechanism by which propranolol causes this dramatic effect is unclear. Using immunohistochemical staining, we show that the CD34+ endothelial progenitor cells of the microvessels in proliferating infantile haemangioma express angiotensin-converting enzyme and angiotensin II receptor-2, but not angiotensin II receptor-1. We have also shown using our in vitro explant model that the cells emanating from proliferating haemangioma biopsies form blast-like structures that proliferate in the presence of angiotensin II. We present here a plausible model involving the renin-angiotensin system that may account for the propranolol-induced accelerated involution of proliferating infantile haemangioma.

Opioidergic regulation of astroglial/neuronal proliferation: where are we now?

Opiate drugs, such as codeine, morphine, and heroin, are powerful analgesics, but also are used as drugs of abuse because of their psychogenic properties. Many studies have shown that opiates impact on cellular proliferation in the adult and developing brain, although anatomical pathologies are lacking in in utero exposed infants and opioid knockout mice. Recent research has defined a context‐dependent role for the opioid system in neurogenesis in the adult hippocampus with exercise. Opioids have been shown to interact with proliferating cells of the postnatal subventricular zone of the lateral ventricles. The subventricular zone is also a region of adult neurogenesis, a fact that was not well established at the time this earlier research was conducted. Although a relationship between opioids and fetal neurogenesis has yet to be firmly established, many studies have implicated the opioid system in this process. One common factor that links neurogenesis in adult, postnatal, and fetal structures is the involvement of neuronal progenitor cells of the astrocytic lineage. It is therefore of interest that opioids have been consistently shown to impact upon astrocytic proliferation. It is the intention of this paper to review the literature that has established a role for the opioid system in neurogenesis in vivo in fetal, postnatal, and adult animals and to examine the links of opioids to modulation of astrocytic proliferation.

Primitive mesodermal cells with a neural crest stem cell phenotype predominate proliferating infantile haemangioma

Aims Infantile haemangioma is a tumour of the microvasculature characterised by aggressive angiogenesis during infancy and spontaneously gradual involution, often leaving a fibro-fatty residuum. The segmental distribution of a subgroup of infantile haemangioma, especially those associated with midline structural anomalies that constitute posterior fossa malformations–hemangiomas–arterial anomalies–cardiac defects–eye abnormalities–sternal cleft and supraumbilical raphe syndrome (PHACES), led us to investigate whether neural crest cells might be involved in the aetiology of this tumour. Methods Immunohistochemical staining on paraffin embedded infantile haemangioma sections and immunocytochemical staining on cells derived from proliferating haemangioma cultures were performed. Results The endothelium of proliferating infantile haemangioma contains abundant cells that express the neurotrophin receptor (p75), a cell surface marker that identifies neural crest cells, and also for brachyury, a transcription factor expressed in cells of the primitive mesoderm. The endothelium is also immunoreactive for the haematopoietic stem cell marker, CD133; the endothelial-haematopoietic stem/progenitor marker, CD34; the endothelial cell markers, CD31 and VEGFR-2; and the mesenchymal stem cell markers, CD29 and vimentin. Additionally, immunoreactivity for the transcription factors, Sox 9 and Sox 10, that are expressed by prospective neural crest cells was also observed. Cells from microvessel-like structures were isolated from in vitro cultured haemangioma tissue explants embedded in a fibrin matrix. Immunostaining of these cells showed that they retained expression of the same lineage-specific markers that are detected on the paraffin embedded tissue sections. Conclusions These data infer that infantile haemangioma is derived from primitive mesoderm and that the cells within the lesion have a neural crest stem cell phenotype, and they express proteins associated with haematopoietic, endothelial, neural crest and mesenchymal lineages. The authors propose a model to account for the natural progression of infantile haemangioma based upon the multipotent expression profile of the primitive mesoderm and their neural crest stem cell phenotype to form all the cell lineages detected during infantile haemangioma proliferation and involution.

Haemogenic endothelium in infantile haemangioma

Background Proliferating infantile haemangioma (IH) is a tumour of the microvasculature composed predominantly of immature endothelial cells. The origin of IH is unclear, but it has been shown to express markers of both endothelial and haematopoietic lineages, and a role for endothelial progenitor cells in the aetiology of IH has been suggested. Haemangioblasts are precursors of both endothelial and haematopoietic cells, and their characterisation has identified the expression of cell surface and intracellular proteins that collectively can be used for assigning a haemangioblast phenotype. Methods The authors used immunohistochemical staining to characterise the expression of primitive haematopoietic-associated proteins in proliferating IHs. Results and discussion The authors show that the cells forming the capillary endothelium express markers associated with primitive haematopoietic cells. Additionally, many of these cells express the transcription factors brachyury and GATA-2, indicating a primitive mesodermal origin. They hypothesise that the immature capillaries in IH are derived from primitive mesodermal cells with haemangioblastic differentiation capabilities. The expression of primitive mesodermal, endothelial and haematopoietic markers by the cells forming the endothelium suggests that the immature capillaries that predominate in proliferating IH are a haemogenic endothelium phenotype, derived from haemangioblasts.

Infantile haemangioma expresses embryonic stem cell markers

Background The origin of infantile haemangioma (IH) remains enigmatic. A primitive mesodermal phenotype origin of IH with the ability to differentiate down erythropoietic and terminal mesenchymal lineages has recently been demonstrated. Aims To investigate the expression of human embryonic stem cell (hESC) markers in IH and to determine whether IH-derived cells have the functional capacity to form teratoma in vivo. Methods Immunohistochemical staining and quantitative reverse transcription PCR were used to investigate the expression of hESC markers in IH biopsies. The ability of cells derived from proliferating IH to form teratomas in a mouse xenograft model was investigated. Results The hESC markers, Oct-4, STAT-3 and stage-specific embryonic antigen 4 were collectively expressed on the endothelium of proliferating IH lesions, whereas Nanog was not. Nanog was expressed by cells in the interstitium and these cells did not express Oct-4, stage-specific embryonic antigen 4 or STAT-3. Proliferating IH-derived cells were unable to form teratomas in severely compromised immunodeficient/non-obese diabetic mice. Conclusion The novel expression of hESC on two different populations of cells in proliferating IH and their inability to form teratomas in vivo infer the presence of a primitive cellular origin for IH downstream from hESC.

Treatment of infantile haemangioma with captopril.

Background  Infantile haemangioma (IH) has recently been reported as an aberrant proliferation and differentiation of a primitive mesoderm‐derived haemogenic endothelium regulated by the renin‐angiotensin system (RAS), leading us to propose angiotensin converting enzyme (ACE) as a potential therapeutic target.

A placental chorionic villous mesenchymal core cellular origin for infantile haemangioma

Aims To investigate the expression of the placental cell-specific associated proteins in infantile haemangioma (IH). Methods Immunohistochemical staining was used to investigate the expression of human chorionic gonadotrophin (hCG), human placental lactogen (hPL), human leucocyte antigen-G (HLA-G), cytokeratin 7 (CK7) and smooth muscle actin in paraffin-embedded sections of proliferating and involuted IHs. Results The proteins hCG and hPL were expressed by the endothelium but not the pericyte layer of proliferating IH, but these proteins were not detected in involuted lesions. There was no expression of CK7 and HLA-G in IH. Conclusions The expression of hCG and hPL, but not CK7 or HLA-G, by the endothelium of proliferating IH supports a placental chorionic villous mesenchymal core cellular origin for IH rather than a trophoblast origin.

Mu opioid receptors are expressed on radial glia but not migrating neuroblasts in the late embryonic mouse brain.

Mu opioid receptor ligands such as morphine and met-enkephalin are known to modulate normal brain development by perturbing gliogenesis and inhibiting neuronal proliferation. Surprisingly, the distribution of the mu opioid receptor (MOR) in the embryonic brain, especially in proliferative regions, is poorly defined and subject to conflicting reports. Using an immunohistochemical approach, we found that MOR protein was expressed in the neuroepithelia of the lateral ventricles, third ventricle, and aqueduct within the late embryonic (E15.5 and E18.5) mouse brain. In contrast to the ventricular neuroepithelia, the proliferative external granule layer of the embryonic cerebellum did not express MOR protein, although the Purkinje cell layer did. Within the ventricular neuroepithelium, GLAST-positive radial glia that incorporate BrdU expressed MOR, while migrating neuroblasts (doublecortin-positive) do not. BrdU labeling of proliferating cells showed an anterior to posterior gradient of proliferation (P<0.05), while an opposing posterior to anterior gradient of MOR expression (P<0.05) was found. The localization of MOR immunoreactivity within the embryonic ventricular neuroepithelia is consistent with a role for opioids in modulating neurogenesis.

Mesenchymal stem cells in infantile haemangioma

Background Fibro-fatty deposition commonly occurs during involution of infantile haemangioma (IH). Mesenchymal stem cells have been identified in this tumour and have been proposed to be recruited from the bone marrow and/or adjacent niches, and then give rise to the fibro-fatty tissue. The authors have recently demonstrated that the capillary endothelium of proliferating IH co-expresses primitive mesodermal, mesenchymal and neural crest markers and proposed that this same endothelium has the ability to give rise to cells of mesenchymal lineage that constitute the fibro-fatty deposition. Methods Immunohistochemistry and real-time RT-PCR were used to further characterise proliferating IHs and haemangioma explant-derived cells (HaemEDCs). Results The authors have further confirmed expression of the mesenchymal-associated proteins including preadipocyte factor-1, a mesenchymal differentiation inhibition-associated cytokine. The HaemEDCs could be differentiated into osteoblasts and adipocytes, indicating their functional potential for terminal differentiation. Discussion The collective expression of neural crest, mesenchymal and mesenchymal differentiation inhibition-associated proteins on the endothelium of proliferating IH suggests that the cells in the capillary endothelium within the lesion possess the ability to undergo terminal mesenchymal differentiation during the proliferating phase, but are inhibited from doing so.

MDMA causes a redistribution of serotonin transporter from the cell surface to the intracellular compartment by a mechanism independent of phospho-p38-mitogen activated protein kinase activation

3,4-methylenedioxymethamphetamine (MDMA) causes long-term serotonin depletion and reduced serotonin transporter (SERT) function in humans and in animal models. Using quantitative Western blotting and real-time PCR, we have shown that total SERT protein in the striatum and nucleus accumbens and mRNA levels in the dorsal raphe nucleus were not significantly changed following MDMA exposure in rats (4 x 2 h i.p. injections, 10 mg/kg each). In mouse neuroblastoma (N(2)A) cells transiently expressing green fluorescent protein-tagged human SERT (GFP-hSERT), we have shown redistribution of SERT from the cell surface to intracellular vesicles on exposure to MDMA using cell surface biotinylation, total internal reflection fluorescence microscopy (TIRFM) and live-cell confocal microscopy. To investigate the mechanism responsible for SERT redistribution, we used specific antibodies to phospho-p38-mitogen activated protein kinase (p38 MAPK), a known signalling pathway involved in SERT membrane expression. We found that p38 MAPK activation was not involved in the MDMA-induced redistribution of SERT from the cell-surface to the cell interior. A loss of SERT from the cell surface on acute exposure to MDMA may contribute to the decreased SERT function seen in rats exposed to MDMA.