Injection of genetically engineered fibroblasts corrects regenerated human epidermolysis bullosa skin tissue

Abstract

Current therapeutic strategies for genetic skin disorders rely on the complex process of grafting genetically engineered tissue to recipient wound beds. Because fibroblasts synthesize and secrete extracellular matrix, we explored their utility in recessive dystrophic epidermolysis bullosa (RDEB), a blistering disease due to defective extracellular type VII collagen. Intradermal injection of RDEB fibroblasts overexpressing type VII collagen into intact RDEB skin stably restored correctly localized type VII collagen expression in vivo and normalized hallmark RDEB disease features, including subepidermal blistering and anchoring fibril defects. This article was published online in advance of the print edition. The date of publication is available from the JCI website, http://www.jci.org.

Figure 1

Type VII collagen expression in primary skin cells. (a) Immunoblots of extracts from primary RDEB (EB) and normal (NL) patient skin fibroblasts and keratinocytes (KCs). The first lane represents RDEB⁺ fibroblasts engineered to overexpress type VII collagen. pCOL7A1 is a CMV-driven expression plasmid for type VII collagen (3) stably transfected using the φC31 integrase. Optical densitometric quantitation of type VII collagen protein levels are noted below each sample lane, normalized to BRG1 (25), a constitutively expressed control for extract loading, quality, and transfer; normal fibroblasts are assigned a relative value of 1.0. UD, undetectable. (b) Cellular expression of type VII protein expression (green) in engineered (RDEB⁺), normal (NL), and uncorrected (RDEB^–) fibroblasts. Counterstaining with Hoechst 33342 marks all cellular nuclei (blue).

Figure 2

Intradermal injection of RDEB⁺ fibroblasts delivers human type VII collagen to the murine epidermal-dermal junction. Skin from mice injected intradermally with the fibroblast types noted at the left of each row of panels was stained with either the NP185 human-specific monoclonal antibody to type VII collagen (red, first column) or rabbit polyclonal antibodies recognizing both mouse and human type VII collagen (green, second column). Note the presence of human type VII collagen at the cutaneous BMZ in skin injected with RDEB⁺ fibroblasts (top row). Note the lack of BMZ-localized type VII collagen in skin injected with normal fibroblasts (middle row) and its complete absence in skin injected with RDEB^– fibroblasts (bottom row). Circular structures in the mid to deep dermis are hair follicles; note perifollicular dermal human type VII collagen in dermis injected with RDEB⁺ fibroblasts and with the normal fibroblasts (middle row). Merged inset (×40) showing skin injected with RDEB⁺ fibroblasts (top row, far right panel) demonstrates the junction of human type VII collagen detection in the BMZ. Dotted lines denote the upper papillary dermis below the BMZ. Scale bar: 50 μm.

Figure 3

Fibroblast-mediated type VII collagen delivery to human RDEB skin. (a) Type VII collagen (green, first column) is shown in human RDEB skin regenerated on immune-deficient mice after intradermal injection with the cell types noted at left. Note the lack of type VII collagen in skin injected with RDEB^– fibroblasts (top row) and its BMZ localization in skin injected with RDEB⁺ fibroblasts (middle row; arrows in dermis denote a collection of intradermal RDEB⁺ cells). Note the blistering seen past the border of human type VII collagen protein (bottom row). The human origin of the skin tissue studied was confirmed using species-specific antibodies to involucrin (orange, second column); triple-stained specimens with serial histological sections are shown. Scale bar: 50 μm. (b) RDEB⁺ fibroblasts in RDEB skin tissue. Note type VII collagen–positive dermal cells (arrows) with typical elongated fibroblast morphology in tissue injected with RDEB⁺ cells and the complete absence of detectable type VII collagen in RDEB skin tissue injected with RDEB^– cells. Scale bars: top panels, 75 μm; bottom panels, 15 μm. E, epidermis; D, dermis; bl, blister.

Figure 4

Restoration of anchoring fibrils after intradermal fibroblast injection. BMZ ultrastructure of human skin tissue regenerated on CB.17 scid/scid mice. Note the absence of anchoring fibrils in RDEB skin injected with RDEB^– fibroblasts (middle panel) and their restoration in RDEB skin injected with RDEB⁺ fibroblasts (right panel). Normal skin control (left panel) was produced using cells from normal subjects. Arrows denote representative anchoring fibrils. Scale bar: 500 nm. ld, lamina densa.