Smits T, van Laarhoven A I M, Staassen A, van de Kerkhof P C M, van Erp P E J, Gerritsen M-J P
Department of Dermatology, Radboud University Nijmegen Medical Centre, PO Box 9101, 6500 HB Nijmegen, the Netherlands.
Br J Dermatol. 2009 Apr;160(4):849-57. doi: 10.1111/j.1365-2133.2008.09012.x. Epub 2009 Jan 27.
In photodynamic therapy the endogenous photosensitizer protoporphyrin IX (PpIX) is synthesized following topical application of aminolaevulinic acid (ALA). However, different tissues have distinct PpIX-accumulating properties, due to differences in penetration of ALA through the stratum corneum and/or alterations in the haem cycle. Preferential PpIX accumulation has been reported in terminally differentiated cell cultures but ex vivo data are lacking.
To study the intrinsic PpIX-accumulating capabilities of skin explants from lesional and nonlesional skin in psoriasis and actinic keratosis, with normal skin serving as a control, and to study PpIX accumulation in relation to differentiation status in normal skin.
Skin explants from patients with psoriasis, actinic keratosis and normal skin were incubated with ALA and PpIX was measured spectrofluorometrically. PpIX was measured in basal (beta1-integrin-positive) and suprabasal (beta1-integrin-negative) keratinocytes in normal skin. In addition, PpIX accumulation was studied in cell cultures at different levels of confluence and after induction of terminal differentiation.
No significant differences in PpIX content were found between the different tissues. However, increased PpIX was found in beta1-integrin-negative compared with beta1-integrin-positive cells. In addition, in subconfluent cell cultures less PpIX was found compared with confluent cell cultures. Induction of terminal differentiation in vitro, however, resulted in less PpIX, which was likely to be related to cell volume.
As no significant differences in PpIX synthesis could be found between the different tissue types, these data emphasize the importance of the penetration route of ALA through the stratum corneum. Preferential PpIX accumulation observed in suprabasal epidermal keratinocytes and confluent cell cultures points towards a terminal differentiation-specific effect.
在光动力疗法中，外用氨基乙酰丙酸（ALA）后可合成内源性光敏剂原卟啉IX（PpIX）。然而，由于ALA透过角质层的渗透率不同和/或血红素循环的改变，不同组织具有不同的PpIX积累特性。在终末分化细胞培养中已报道有PpIX的优先积累，但缺乏离体数据。
以正常皮肤为对照，研究银屑病和光化性角化病患者病变皮肤和非病变皮肤的皮肤外植体的固有PpIX积累能力，并研究正常皮肤中PpIX积累与分化状态的关系。
将银屑病、光化性角化病患者及正常皮肤的皮肤外植体与ALA一起孵育，并用荧光分光光度法测定PpIX。在正常皮肤的基底（β1整合素阳性）和基底上层（β1整合素阴性）角质形成细胞中测量PpIX。此外，还研究了不同汇合度的细胞培养物以及诱导终末分化后PpIX的积累情况。
不同组织之间未发现PpIX含量有显著差异。然而，与β1整合素阳性细胞相比，β1整合素阴性细胞中的PpIX增加。此外，与汇合的细胞培养物相比，亚汇合细胞培养物中发现的PpIX较少。然而，体外诱导终末分化导致PpIX减少，这可能与细胞体积有关。
由于不同组织类型之间未发现PpIX合成有显著差异，这些数据强调了ALA透过角质层的渗透途径的重要性。在基底上层表皮角质形成细胞和汇合细胞培养物中观察到的PpIX优先积累指向终末分化特异性效应。
