Table 1.

Regulation of cell proliferation in skin and keratinocytes by PPARβ/δ.

Model	Effect	Reference
Homozygous Pparβ/δ-null mouse skin (disrupted by neomycin cassette in last exon of ligand binding domain) treated topically with phorbol ester	Enhanced hyperplasia in null mouse skin as compared to wild-type mouse skin	[22]
Heterozygous Pparβ/δ-null mouse skin (disrupted by neomycin cassette between exon 4 and 5 encoding the DNA binding domain) treated topically with phorbol ester	Enhanced hyperplasia in null mouse skin as compared to wild-type mouse skin	[21]
Homozygous Pparβ/δ-null mouse skin (disrupted by deleting exon 4 of the DNA binding domain)	Increased epidermal thickness and PCNA-positive keratinocytes in null mouse skin as compared to wild-type mouse skin	[23]
Mouse skin	Enhanced hyperplasia in null mouse skin as compared to wild-type mouse skin	[31]
Mouse skin	Enhanced hyperplasia in null mouse skin as compared to wild-type mouse skin, prevented by ligand activation of PPARβ/δ; an effect not found in null mouse skin	[30]
Normal human keratinocytes	0.05 – 0.5 μM L165041 and 0.2 - 5.0 μM TTA inhibit cell proliferation	[26]
N/TERT-1 human keratinocyte cell line	1.0 μM GW0742 inhibits cell proliferation	[25]
Human NCTC 2544 keratinocyte cell line	0.05 – 1.0 mM DEHP inhibits cell proliferation	[27]
Human HaCaT keratinocyte cell line	1.0 – 10 μM μM GW0742 inhibits cell proliferation and increases apoptosis; no effect on serum withdrawal-induced apoptosis	[24]
Mouse primary keratinocytes	0.1 – 1.0 μM μM GW0742 inhibits cell proliferation	[24]
Mouse primary keratinocytes	Enhanced cell proliferation in null keratinocytes as compared to wild-type	[28]
Mouse primary keratinocytes	0.01 - 0.1 μM μM GW0742 inhibits cell proliferation	[29]
Mouse skin	Topical application of 4 mM GW1514 has no effect on epidermal cell proliferation	[32]
Human primary keratinocytes from psoriasis patients	1.0 μM L165041 and 5.0 μM GW501516 increases cell proliferation	[33]