Isolation of Mouse Epidermal Keratinocytes and Their In Vitro Clonogenic Culture.

The protocol described here is a reliable method of harvesting primary keratinocytes from adult female mice (54 ± 2 days old) yielding approximately 30 x 106 viable cells per mouse. Primary adult mouse keratinocytes are harvested from the dorsal skin of female mice. Male mice (~6 weeks old) can be used for keratinocyte harvesting depending on the requirements of the experiment. Euthanized mice are shaved and sterilized with serial washes in povidone iodine and ethanol solutions (70% alcohol). After disinfecting the mice, the dorsal skin is removed and the subcutaneous fat and muscle are removed with a scalpel and discarded. The skins are cut into small pieces and treated with a mild, low temperature trypsinization to detach the lower dermis from the epidermis. The scraped epidermises are stirred at low speed, filtered to remove the hairs, counted, and re-suspended in culture medium. This method provides an excellent single cell suspension of highly culturable cells for many downstream applications.

Bone marrow-derived epithelial cells and hair follicle stem cells contribute to development of chronic cutaneous neoplasms.

We used allogeneic bone marrow transplantation (BMT) and a mouse multistage cutaneous carcinogenesis model to probe recruitment of bone marrow-derived epithelial cells (BMDECs) in skin tumors initiated with the carcinogen, dimethylbenz[a]anthracene (DMBA), and promoted with 12-O-tetradecanolyphorbol-13-acetate (TPA). BMDECs clustered in the lesional epithelium, expressed cytokeratins, proliferated, and stratified. We detected cytokeratin induction in plastic-adherent bone marrow cells (BMCs) cultured in the presence of filter-separated keratinocytes (KCs) and bone morphogenetic protein 5 (BMP5). Lineage-depleted BMCs migrated towards High Mobility Group Box 1 (HMGB1) protein and epidermal KCs in ex vivo invasion assays. Naive female mice receiving BMTs from DMBA-treated donors developed benign and malignant lesions after TPA promotion alone. We conclude that BMDECs contribute to the development of papillomas and dysplasia, demonstrating a systemic contribution to these lesions. Furthermore, carcinogen-exposed BMCs can initiate benign and malignant lesions upon tumor promotion. Ultimately, these findings may suggest targets for treatment of non-melanoma skin cancers.

Hmga2 translocation induced in skin tumorigenesis.

Hmga2 protein, a transcription factor involved in chromatin architecture, is expressed chiefly during development, where it has many key biological functions. When expressed in adult tissues from in various organs, Hmga2 is always related to cancer development. The role of Hmga2 in skin tumorigenesis is, however, not yet understood. We demonstrated that Hmga2 can be found in non-transformed epidermis, specifically located to the membrane of keratinocytes (KCs) in epidermis. Ex vivo culture of KCs and development of skin carcinomas in DMBA and TPA mouse models was associated with translocation of the Hmga2 protein from the membrane into the nucleus, where Hmga2 induced its own expression by binding to the Hmga2 promoter. Panobinostat, an HDAC inhibitor, downregulated Hmga2 expression by preventing Hmga2 to bind its own promoter, and thus inhibiting Hmga2 promoter activity. Hmga2 translocation to the nucleus could in part be prevented by an inhibitor for ROCK1. Our findings demonstrate that upon program of benign papilloma to malignant cSCC of skin tumorigenesis, Hmga2 translocates in a ROCK-dependent manner from the membrane to the nucleus, where it serves as an autoregulatory transcription factor, causing cell transformation.

The spleen as an extramedullary source of inflammatory cells responding to acetaminophen-induced liver injury.

Macrophages have been shown to play a role in acetaminophen (APAP)-induced hepatotoxicity, contributing to both pro- and anti-inflammatory processes. In these studies, we analyzed the role of the spleen as an extramedullary source of hepatic macrophages. APAP administration (300mg/kg, i.p.) to control mice resulted in an increase in CD11b(+) infiltrating Ly6G(+) granulocytic and Ly6G(-) monocytic cells in the spleen and the liver. The majority of the Ly6G(+) cells were also positive for the monocyte/macrophage activation marker, Ly6C, suggesting a myeloid derived suppressor cell (MDSC) phenotype. By comparison, Ly6G(-) cells consisted of 3 subpopulations expressing high, intermediate, and low levels of Ly6C. Splenectomy was associated with increases in mature (F4/80(+)) and immature (F4/80(-)) pro-inflammatory Ly6C(hi) macrophages and mature anti-inflammatory (Ly6C(lo)) macrophages in the liver after APAP; increases in MDSCs were also noted in the livers of splenectomized (SPX) mice after APAP. This was associated with increases in APAP-induced expression of chemokine receptors regulating pro-inflammatory (CCR2) and anti-inflammatory (CX3CR1) macrophage trafficking. In contrast, APAP-induced increases in pro-inflammatory galectin-3(+) macrophages were blunted in livers of SPX mice relative to control mice, along with hepatic expression of TNF-α, as well as the anti-inflammatory macrophage markers, FIZZ-1 and YM-1. These data demonstrate that multiple subpopulations of pro- and anti-inflammatory cells respond to APAP-induced injury, and that these cells originate from distinct hematopoietic reservoirs.