Alteration of skin properties with autologous dermal fibroblasts

Abstract

Dermal fibroblasts are mesenchymal cells found between the skin epidermis and subcutaneous tissue. They are primarily responsible for synthesizing collagen and glycosaminoglycans; components of extracellular matrix supporting the structural integrity of the skin. Dermal fibroblasts play a pivotal role in cutaneous wound healing and skin repair. Preclinical studies suggest wider applications of dermal fibroblasts ranging from skin based indications to non-skin tissue regeneration in tendon repair. One clinical application for autologous dermal fibroblasts has been approved by the Food and Drug Administration (FDA) while others are in preclinical development or various stages of regulatory approval. In this context, we outline the role of fibroblasts in wound healing and discuss recent advances and the current development pipeline for cellular therapies using autologous dermal fibroblasts. The microanatomic and phenotypic differences of fibroblasts occupying particular locations within the skin are reviewed, emphasizing the therapeutic relevance of attributes exhibited by subpopulations of fibroblasts. Special focus is provided to fibroblast characteristics that define regional differences in skin, including the thick and hairless skin of the palms and soles as compared to hair-bearing skin. This regional specificity and functional identity of fibroblasts provides another platform for developing regional skin applications such as the induction of hair follicles in bald scalp or alteration of the phenotype of stump skin in amputees to better support their prosthetic devices.

Figure 1.

Flow diagram of harvesting skin, growing fibroblasts, and injecting for different uses. The location of the skin biopsy for growing fibroblasts may be directed by the therapeutic indication.

Figure 2.

Human fibroblasts injected into the hypodermis of mice survive for at least 8 weeks. (A) H&E stained sections shows the presence of injected cells visible as a non-native cluster of fibroblasts in the hypodermis below the muscle layer; (B) Fibroblasts were incubated with red dye tracer, CellTracker™Red CMTPX and are bright red in serial section evaluated using a fluorescence microscope confirming the identity, implantation and survival of human cells. Nuclei stained with DAPI. Scale bars: A, 130 μm and B, 250 μm.

Figure 3.

Microanatomic regions of the skin have distinct fibroblast populations which differ in their physical characteristics and functional capabilities.

Figure 4.

Human dermal papilla (DP) spheroids induce chimeric hair follicles in reconstitution assay. (A) Hair fibers in the hypodermis 4 weeks following injection of a mixture of human DP spheroids (10,000 cells/spheroid) and mouse epidermal cells; (B) H&E stained horizontal section of injection cyst forming HFs and sebaceous glands; and (C) Fluorescence in situ hybridization analysis of the assay site reveals that human DP cells probed with human specific pan-centromeric probe (red) co-exist with the mouse epidermal cells probed with mouse specific pan-centromeric probe (green). Scale bars: A, B and C, 35 μm.