Table 1. Characteristics of fibroblast-like cell (FBLC) type I–IV.

Type of FBLC	Portion	Distinctive ultrastructure and localization	3D shape	Estimated correspondence with the cells in the previous report
I and II	CB~CL	• Expanded ER with spherical shape (I) or thin and multi-layered ER (II)	Irregular shape	• Fibloblast [41] • Telocyte [6, 7, 28] • CD34+CD31− cell [28, 40]
		• Cellular process extended along the epithelial basal lamina and toward LP
		• Localizing subepithelial region farer away than FBLC type III
III	CL~IV-A	• Non-organelle region with high electron density at the epithelial sides • Cellular process extended along the epithelial basal lamina • Forming the thin reticular structure just beneath the epithelium	Thin mesh shape	• Subepithelial myofibroblast [22]
				• Subepithelial fibroblast [12,13,14]
				• PDGFRα+αSMA+ cell (crypt) [28]
				• PDGFRα+αSMA− cell (villus) [28]
IV	IV-B~IV-A	• Irregularly scattered non-organelle region with high electron density • Localizing along the villous myocytes in LP • Interacion with FBLC type III especially in IV-A	Irregular shape	• Fibroblast [15]
				• Reticular cell [30]
				• Myofibroblast [17]

αSMA, alpha smooth muscle actin. CB, base of crypt. CL, lateral portion of crypt. ER, endoplasmic reticulum. IV-A, apical portion of intestinal villus. IV-B, basal portion of intestinal villus. LP, lamina propria. PDGFRα, platelet-derived growth factor receptor alpha.