p21^cip/WAFis a key regulator of long-term radiation damage in mesenchyme-derived tissues

Abstract

This study aimed to determine the mechanisms responsible for long-term tissue damage following radiation injury. We irradiated p21-knockout (p21(-/-)) and wild-type (WT) mice and determined the long-term deleterious effects of this intervention on mesenchyme-derived tissues. In addition, we explored the mechanisms of radiation-induced mesenchymal stem cell (MSC) dysfunction in isolated bone marrow-derived cells. p21 expression was chronically elevated >200-fold in irradiated tissues. Loss of p21 function resulted in a >4-fold increase in the number of skin MSCs remaining after radiation. p21(-/-) mice had significantly less radiation damage, including 6-fold less scarring, 40% increased growth potential, and 4-fold more hypertrophic chondrocytes in the epiphyseal plate (P<0.01). Irradiated p21(-/-) MSCs had 4-fold increased potential for bone or fat differentiation, 4-fold greater proliferation rate, and nearly 7-fold lower senescence as compared to WT MSCs (P<0.01). Ectopic expression of p21 in knockout cells decreased proliferation and differentiation potential and recapitulated the WT phenotype. Loss of p21 function markedly decreases the deleterious effects of radiation injury in mesenchyme-derived tissues and preserves tissue-derived MSCs. In addition, p21 is a critical regulator of MSC proliferation, differentiation, and senescence both at baseline and in response to radiation.

IL-6 regulates adipose deposition and homeostasis in lymphedema

“…To circumvent these difficulties, we used two different mouse models to study the effects of variable degrees of lymphatic injury on IL-6 expression. We have previously shown that ALND in mice results in significant but subtle increases in arm volume peaking at 3 wk and returning to normal by 6 wk (24,39). In this model, similar to clinical findings after lymphadenectomy, the ipsilateral limb is essentially normal in appearance by 6 wk.…”

Adipose-Derived Stem Cells Promote Lymphangiogenesis in Response to VEGF-C Stimulation or TGF-β1 Inhibition

“…ASCs were characterized for expression of known MSC markers (Sca1, CD29, CD73 and CD105) and absence of hematopoietic cell markers (CD34, CD45 and CD31) using our previously described flow cytometry techniques [21,22]. Briefly, cells were trypsinized, washed and 1 × 10 6 cells were incubated with fluorescent-tagged primary antibodies (from eBioscience; catalogue numbers as follows: Sca1 17-5981–81, CD29 12-0291-81, CD73 12-0731-81, CD105 12-1051-81, CD34 12-0341-81, CD45 15-045-81 [San Diego, CA, USA]; and CD31 from Biolegend [San Diego, CA, USA]) for 30 min at 4°C.…”

“…In order to analyze the pluripotential differentiation capacity of harvested ASCs, we induced bone, fat and cartilage differentiation using our previously published techniques [22,23]. Briefly, bone differentiation was induced by exposing cells to MesenCult ® stem cell media supplemented with 5 mM β-glycerophosphate, 10 −8 M dexamethasone and 0.28 mM ascorbic acid (all from Sigma-Aldrich, St Louis, MO, USA) for 14 days.…”

“…Briefly, bone differentiation was induced by exposing cells to MesenCult ® stem cell media supplemented with 5 mM β-glycerophosphate, 10 −8 M dexamethasone and 0.28 mM ascorbic acid (all from Sigma-Aldrich, St Louis, MO, USA) for 14 days. Von Kossa staining was then performed as previously described to stain mineralized bone nodules [22,23]. For fat differentiation, cells were initially cultured in MesenCult stem cell media supplemented with 10 −6 M dexamethasone (Sigma), 1 mM insulin (Sigma) and 0.25 mM 3-isobutyl-1-methyl-xanthine for 4 days and then maintained in MesenCult supplemented with just insulin (1 mM) for 10 days.…”

Comparable Senescence Induction in Three-dimensional Human Cartilage Model by Exposure to Therapeutic Doses of X-rays or C-ions

“…Several proteins are of interest according to their function in cartilage homeostasis and/or differentiation. The cyclin-dependent kinase inhibitor (CKI) p21 has been associated with cellular senescence in different cell lines (8) and plays a major role in the regulation of long-term radiation damage in mesenchymederived tissues (9). Furthermore, H2A.J has recently been described as a novel histone variant accumulating in human senescent cells (10), and cyclooxygenase-2 (COX-2) protein has been associated with chondrocyte differentiation (11).…”