Ultrastructural and immunohistochemical characteristics of telocytes in human scalp tissue

Abstract

This study was designed to characterize the location, morphology and ultrastructure of telocytes (TCs) in human scalp tissue. After obtaining approval for this study and informed consent from the patient, a scalp specimen was obtained. The distribution and morphology of TCs in human scalp tissue was assessed by immunohistochemical staining of CD34 and CD117/c-KIT, and the ultrastructure of TCs was investigated using transmission electron microscopy (TEM). Immunohistochemical staining of CD34 revealed that TCs were located in the connective tissue of human scalp, and were concentrated around hair follicles (HFs), blood vessels, sweat glands, sebaceous glands and adipose lobules. Immunohistochemical staining of CD117 revealed that TCs were mainly located in the dermis of human scalp, surrounding the HFs and sweat glands. Under TEM, TCs were seen and confirmed by their special morphological features. These cells were spindle-shaped, had small cell bodies and long thin processes, and surrounded stem cell clusters in the bulge region of HFs. These results demonstrate that TCs in human scalp were positive for CD34 and CD117, and their strategic positioning surrounding stem cells suggests their possible involvement in local regeneration, remodeling and homeostasis of the skin.

Figure 1

Human scalp tissue stained immunohistochemically for CD34. (a) CD34⁺ cells (TCs) (black arrow) were in the deep dermis and subcutaneous tissue (40×). (b) A few TCs body (black arrows) with their Tps (red arrows) extended parallel to the adjacent epidermis (100×). (c) The spatial relationship of TCs body (black arrows) with their Tps (red arrows) and a blood vessel (yellow arrow) (100×). (d–g) TCs body (black arrows) and their Tps (red arrows) surrounded deep segments of HFs (d, 100×), sebaceous glands (e, 200×), secretory or ductal parts of the sweat glands (f, 200×) and intervals of adipose lobules (g, 200×). (h) TCs body (black arrows) and their Tps (red arrows) bordering the bulge and sub-bulge areas of HFs (200×).

Figure 2

Human scalp tissue stained immunohistochemically for CD117. CD117+ cells (TCs body) (black arrows) with their Tps (red arrows) were observed surrounding HFs (a, 100×), sweat glands (b, 200×) and sebaceous glands (c, 200×).

Figure 3

Human scalp tissue stained immunohistochemically for CD117 and CD34. CD117+ cells (TCs body) (black arrows) with their Tps (red arrows) were observed in the reticular dermis, subcutaneous tissue of normal scalp (a, 200×; b, 400×), and around the middle of HFs (c, 100×; d, 200×; e, 200×). Figure (b) is an enlargement of the rectangular frame of Figure (a). Figure (d) is an enlargement of the rectangular frame a of Figure (c). Figure (e) is an enlargement of the rectangular frame b of Figure (c).

Figure 4

Ultrastructural analysis of TCs in the dermis of human scalp. TCs presented two or three extremely long and thin Tps (white arrows), which were close to the basal layer of the epidermis (a, 1500×) and ran parallel to it (b, 2,500×).

Figure 5

The fine structure of TCs (black arrow). TC mostly occupied by a nucleus and encircled by a small quantity of cytoplasm. The cytoplasm contained mitochondria (red arrow), rough (yellow arrow) and smooth (red arrow) endoplasmic reticulum (a, 7,000×). (b) Narrow segments (podomer, white rhombus) on a Tp (white arrow) alternating with dilations (podoms, black rhombus) (20,000×). (c) Extracellular vesicles released by a TC (20,000×).