Unité de Biologie moléculaire du Développement, Institut Pasteur, 25 rue du Docteur Roux, F-75724 Paris Cedex 15, France.
Development. 2012 Oct;139(20):3741-51. doi: 10.1242/dev.081091.
The hair follicle (HF) is a multi-tissue mini-organ that self-renews periodically. However, the cellular organisation of this much-studied model is not fully understood. The structures of the outer layer and of the bulb, which ensures HF growth, have not been completely established. To clarify these points, we have conducted in vivo clonal analyses with 3D imaging in mice. The upper two-thirds of the HF outer layer consists of two clonally unrelated groups of cells that exhibit different modes of growth. They correspond to the basal outer root sheath (ORS) and the companion layer (Cp). The basal ORS has an unusual anisotropic mode of growth from a suprabulbar zone, which we named the privileged proliferation zone. The Cp has a stem/transient-amplifying mode of growth and is shown to be an HF internal structure. Furthermore, we describe an additional element, the bulb outer layer, which is contiguous and shares markers (e.g. Lgr5) with the basal ORS but is formed by a separate lineage that belongs neither to the ORS nor Cp lineage. It represents a novel element with proximal cells that are contiguous with the germinative layer in the bulb. In reference to its shape and position we named it the lower proximal cup (LPC). These clonal hierarchies reveal a novel model of HF organisation and growth based on two major entities: the basal ORS and the LPC plus the seven internal layers.
毛囊（HF）是一个多组织的微型器官，能够周期性地自我更新。然而，这个经过大量研究的模型的细胞组织尚未被完全理解。外层和保证 HF 生长的球部结构尚未完全建立。为了澄清这些问题，我们利用 3D 成像在小鼠体内进行了克隆分析。HF 外层的上三分之二由两组不相关的克隆细胞组成，它们表现出不同的生长模式。它们对应于基底外根鞘（ORS）和伴层（Cp）。基底 ORS 具有一种异常的各向异性生长模式，从一个超球区开始，我们将其命名为特权增殖区。Cp 具有干细胞/短暂扩增的生长模式，被证明是 HF 的内部结构。此外，我们描述了一个额外的元素，即球部外层，它与基底 ORS 连续且具有共同的标记物（例如 Lgr5），但由一个单独的谱系形成，既不属于 ORS 也不属于 Cp 谱系。它代表了一个具有与球部生发层相邻的近端细胞的新元素。根据其形状和位置，我们将其命名为下部近端杯（LPC）。这些克隆层次揭示了一个基于两个主要实体的 HF 组织和生长的新模型：基底 ORS 和 LPC 加上七个内部层。
