Phenotypical differences in connective tissue cells emerging from microvascular pericytes in response to over-expression of PDGF-B and TGF-beta in normal skin in vivo

• Fibrosis is a deleterious consequence of chronic inflammation in a number of human pathological states ultimately leading to, if not perturbed to organ dysfunction and failure. Two key processes in fibrosis are activation of blood vessels and connective tissue cells leading to excess deposition of ECM components; collagen type I being the most abundant. In the present study the effects of two growth factors known to be important in the fibrotic process, namely PDGF-B and TGF-β1, were studied. Adenoviral vectors engineered to express PDGF-B or TGF-β1 were introduced into mouse skin thereby inducing a transient over-expression of either growth factor. After 3, 7 and 14 days post injection, tissues were harvested and morphology and protein expression were examined on plastic embedded 1 µm thick sections and by immunohistochemistry on frozen sections, respectively. Over-expression of both TGF-β1 and PDGF-B lead to a fibrotic response consisting of a marked macrophage influx as well as an expansion of the connective tissue cell population. In both conditions the latter originated from microvascular pericytes. The resulting phenotype of the emerging connective tissue cell population differed between PDGF-B and TGF-β1 treated skin.  In tissues over expressing PDGF-B but not TGF-β1 the fibrotic process was partially reversible. Both growth factors were able to initiate, but neither were able to sustain the process of angiogenesis, which lead to vascular regression. PDGF-B but not TGF-β1 was able to stimulate but not maintain a distinct form of angiogenesis i.e. glomeruloid body formation. In conclusion, over-expression of PDGF-B and TGF-β1 in normal skin resulted in the emergence of connective tissue cells differing in their phenotype, originating in both cases from a common cell namely the microvascular pericyte. Therefore the vasculature and the fibrotic process are linked in a previously unrecognized way.

Ämnesord

MEDICIN OCH HÄLSOVETENSKAP  -- Medicinska och farmaceutiska grundvetenskaper -- Medicinsk genetik (hsv//swe)

MEDICAL AND HEALTH SCIENCES  -- Basic Medicine -- Medical Genetics (hsv//eng)

Nyckelord

fibrosis

chronic inflammation

extracellular matrix

myofibroblast

pericyte

adenovirus

in vivo

PDGF-B

TGF-beta

Molecular medicine (genetics and pathology)

Molekylär medicin (genetik och patologi)

Molekylär medicin

Molecular Medicine

Publikations- och innehållstyp

ref (ämneskategori)

art (ämneskategori)