Conversion from human haematopoietic stem cells to keratinocytes requires keratinocyte secretory factors

BACKGROUND

Recent studies have reported that bone-marrow-derived stem cells (BMSCs), including haematopoietic stem cells (HSCs) and mesenchymal stromal cells, differentiate in order to regenerate various cellular lineages. Based on these findings, it is known that BMSCs can be used clinically to treat various disorders, such as myocardial infarction and neurotraumatic injuries. However, the mechanism of HSC conversion into organ cells is incompletely understood. The mechanism is suspected to involve direct cell-cell interaction between BMSCs, damaged organ cells, and paracrine-regulated soluble factors from the organ, but to date, there have been no investigations into which of these are essential for keratinocyte differentiation from HSCs.

AIM

To elucidate the mechanism and necessary conditions for HSC differentiation into keratinocytes in vitro.

METHODS

We cultured human (h)HSCs under various conditions to try to elucidate the mechanism and necessary conditions for hHSCs to differentiate into keratinocytes.

RESULT

hHSCs cocultured with mouse keratinocytes induced expression of human keratin 14 and transglutaminase I. Only 0.1% of the differentiated keratinocytes possessed multiple nuclei indicating cell fusion. Coculture of hHSCs with fixed murine keratinocytes (predicted to stabilize cellular components) failed to induce conversion into keratinocytes. Conversely, keratinocyte-conditioned medium from both human and mouse keratinocytes was found to mediate hHSC conversion into keratinocytes.

CONCLUSIONS

Human HSCs are capable of differentiation into keratinocytes, and cell fusion is extremely rare. This differentiating is mediated by the plasma environment rather than by direct cell-cell interactions.

Pyoderma gangrenosum of the eyelid: report of two cases and review of the literature

Pyoderma gangrenosum (PG) of the eyelid is extremely rare, and its proper management is essential for the preservation of visual function. Here, we report 2 cases of PG of the eyelid with intraorbital involvement. In both cases, the skin and intraorbital lesions improved after systemic immunosuppressive therapies; however, corneal perforation occurred in 1 case. In order to assess the clinical features of PG of the eyelid and to obtain clues for optimal treatment, we reviewed 15 well-documented cases in the literature, including the present cases. Corneal perforation occurred in 4 cases and defective ocular motility in 1 case. Three patients eventually underwent enucleation of the affected eye. Our cases and the literature review clearly indicate that MRI is a powerful tool for evaluating the extent of extracutaneous PG lesions around the eye and that early diagnosis and immediate immunosuppressive therapy are crucial for the preservation of visual acuity.

Two cases of atypical membranous aplasia cutis with hair collar sign: one with dermal melanocytosis, and the other with naevus flammeus

We report two atypical cases of membranous aplasia cutis surrounded by a rim of hairs, one case associated with dense dermal melanocytosis and the other with naevus flammeus, with characteristic clinical features. A rim of hypertrichosis, 'hair collar' sign, is proposed to have a close association with neuroectodermal defects. A failure of the normal closure of the cranial neural tube might have affected foetal skin development, including melanoblast migration and capillary network formation. The changes in the present cases, as well as the hair collar sign may suggest a complex hamartomatous nature of membranous aplasia cutis.

Two cases of pyoderma gangrenosum complicated with nasal septal perforation

We report two patients with pyoderma gangrenosum complicated with nasal septal perforation. An 18-year-old woman and a 65-year-old man had typical lesions of pyoderma gangrenosum on the legs that responded well to oral prednisolone. Both patients complained of mild nasal discharge, and nasal fibroscopy revealed nasal septal perforation. Biopsy of the nasal lesions showed an active inflammatory infiltrate, mainly of neutrophils. Systemic investigations failed to show any pulmonary or renal lesions of Wegener's granulomatosis. Cytoplasmic immunofluorescent pattern antineutrophil cytoplasmic antibody was negative. In both cases, intense neutrophilic infiltration was observed not only in skin lesions but also in nasal lesions, which may indicate that the nasal lesions had a pathogenesis in common with the skin lesions.