ADAMTS5 has been implicated in the degradation of cartilage aggrecan in human osteoarthritis. Here, we describe a novel role for the enzyme in the regulation of TGF1 signaling in dermal fibroblasts both in vivo and in vitro. Dermal wound healing involves a series of cellular responses that depend on the coordinated temporal and spatial expression of inflammatory cytokines, proteases, growth factors, and extracellular matrix molecules. The early phases of hemostasis, inflammation, and re-epithelialization are followed by granulation tissue formation and finally dermal remodeling (1, 2). The granulation tissue is a loosely organized collagenous matrix that serves as a template for cellular regeneration (3) of the collagen (4) and proteoglycan (5-7) structures of the dermis proper.There has been a long held consensus that proteinases, such as plasmin and matrix metalloproteinases, are major players in dermal repair; however, many questions remain regarding substrate and product identification and to what extent cleavage of particular proteins is destructive or reparative (reviewed in Ref. 8). Although much interest has focused on matrix metalloproteinases (9), the ADAMTSs have now also been found to play a major role in a range of repair and regeneration processes. For example, evidence of a role for ADAMTS activity in dermal repair comes from the finding that human skin contains abundant aggrecanase-generated catabolic fragments of versican V0 and V1 (5) and that both aggrecan and versican are associated with the dermal region of the hair follicle (7). Moreover, to place dermal matrix turnover in a broader context, cleavage of the hyalectans aggrecan, versican, and brevican by one or more aggrecanases (ADAMTS1, -4, -5, -8, -9, and -15) occurs in the remodeling of cartilage (10), aorta (11, 12), spinal cord (13), meniscus (14, 15) intervertebral disc (16), adipose tissue (17), and brain (18). HA 2 in the skin is most abundant in the epidermal layer (6), and it undergoes partial fragmentation in both the dermis and epidermis of human skin explants (19). Its role in skin biology has largely focused on its binding to the cell-surface receptor CD44, an interaction that prevents PDGF-BB receptor activation and human fibroblast migration (20). It also appears to be required for MMP9-mediated activation of TGF1 (21). HA has been shown to ligate RHAMM to promote the association of CD44 and p-ERK, an interaction that directly activates cell migration and thereby is required for efficient dermal repair (22,23). HA also regulates the proliferative response of dermal fibroblasts to TGF1 (24), and HA12 oligosaccharides stimulate Col3 and TGF1 expression (25), a finding that is very relevant to the data described here.TGF1 is a key regulator of multiple processes in dermal wound healing (26). In the context of this study, TGF1 stimulates col1 and col3 production by fibroblasts and is required for terminal differentiation of myofibroblasts during wound * This work was supported, in whole or in part, by National Institutes o...