Loss of functional β-cell mass is a hallmark of Type 1 and Type 2 Diabetes. Macrophages play an integral role in the maintenance or destruction of pancreatic β-cells. The effect of the macrophage β-cell interaction is dependent on the activation state of the macrophage. Macrophages can be activated across a spectrum, from pro-inflammatory to anti-inflammatory and tissue remodeling. The factors secreted by these differentially activated macrophages and their effect on β-cells define the effect on functional β-cell mass. In this review, the spectrum of macrophage activation is discussed, as are the positive and negative effects on β-cell survival, expansion, and function as well as the defined factors released from macrophages that impinge on functional β-cell mass.

Background: Over 400 million people are diabetic. Type 1 and type 2 diabetes are characterized by decreased functional β-cell mass and, consequently, decreased glucose-stimulated insulin secretion. A potential intervention is transplantation of β-cell containing islets from cadaveric donors. A major impediment to greater application of this treatment is the scarcity of transplant-ready β-cells. Therefore, inducing β-cell proliferation ex vivo could be used to expand functional β-cell mass prior to transplantation. Various molecular pathways are sufficient to induce proliferation of young β-cells; however, aged β-cells are refractory to these proliferative signals. Given that the majority of cadaveric donors fit an aged demographic, defining the mechanisms that impede aged β-cell proliferation is imperative. Results:We demonstrate that aged rat (5-month-old) β-cells are refractory to mitogenic stimuli that otherwise induce young rat (5-week-old) β-cell proliferation. We hypothesized that this change in proliferative capacity could be due to differences in cyclin-dependent kinase inhibitor expression. We measured levels of p16 INK4a , p15 INK4b , p18 INK4c , p19 INK4d , p21 CIP1 , p27 KIP1 and p57 KIP2 by immunofluorescence analysis. Our data demonstrates an age-dependent increase of p27 KIP1 in rat β-cells by immunofluorescence and was validated by increased p27 KIP1 protein levels by western blot analysis. Interestingly, HDAC1, which modulates the p27 KIP1 promoter acetylation state, is downregulated in aged rat islets. These data demonstrate increased p27 KIP1 protein levels at 5 months of age, which may be due to decreased HDAC1 mediated repression of p27 KIP1 expression. Significance: As the majority of transplant-ready β-cells come from aged donors, it is imperative that we understand why aged β-cells are refractory to mitogenic stimuli. Our findings demonstrate that increased p27 KIP1 expression occurs early in β-cell aging, which corresponds with impaired β-cell proliferation. Furthermore, the correlation between HDAC1 and p27 levels suggests that pathways that activate HDAC1 in aged β-cells could be leveraged to decrease p27 KIP1 levels and enhance β-cell proliferation.

An increasing number of cancer subtypes are treated with front‐line immunotherapy. However, approaches to overcome primary and acquired resistance remain limited. Preclinical mouse models are often used to investigate resistance mechanisms, novel drug combinations, and delivery methods; yet most of these models lack the genetic diversity and mutational patterns observed in human tumors. Here we describe a series of 13 C57BL/6J melanoma cell lines to address this gap in the field. The Ohio State University‐Moffitt Melanoma Exposed to Radiation (OSUMMER) cell lines are derived from mice expressing endogenous, melanocyte‐specific, and clinically relevant Nras driver mutations (Q61R, Q61K, or Q61L). Exposure of these animals to a single, non‐burning dose of ultraviolet B accelerates the onset of spontaneous melanomas with mutational patterns akin to human disease. Furthermore, in vivo irradiation selects against potent tumor antigens, which could prevent the outgrowth of syngeneic cell transfers. Each OSUMMER cell line possesses distinct in vitro growth properties, trametinib sensitivity, mutational signatures, and predicted antigenicity. Analysis of OSUMMER allografts shows a correlation between strong, predicted antigenicity and poor tumor outgrowth. These data suggest that the OSUMMER lines will be a valuable tool for modeling the heterogeneous responses of human melanomas to targeted and immune‐based therapies.

An increasing number of cancer subtypes are treated with front-line immunotherapy. However, approaches to overcome primary and acquired resistance remain limited. Pre-clinical mouse models are often used to investigate resistance mechanisms, novel drug combinations, and delivery methods; yet most of these models lack the genetic diversity and mutational patterns observed in human tumors. Here we describe a series of thirteen C57BL/6J melanoma cell lines to address this gap in the field. The Ohio State University-Moffitt Melanoma Exposed to Radiation (OSUMMER) cell lines are derived from mice expressing endogenous, melanocyte-specific, and clinically relevant Nras driver mutations (Q61R, Q61K, or Q61L). Exposure of these animals to a single, non-burning dose of ultraviolet B accelerates the onset of spontaneous melanomas with mutational patterns akin to human disease. Furthermore, in vivo irradiation selects against potent tumor antigens, which could prevent the outgrowth of syngeneic cell transfers. Each OSUMMER cell line possesses distinct in vitro growth properties, trametinib sensitivity, mutational signatures, and predicted antigenicity. Analysis of OSUMMER allografts shows a correlation between strong, predicted antigenicity and poor tumor outgrowth. These data suggest that the OSUMMER lines will be a valuable tool for modeling the heterogeneous responses of human melanomas to targeted and immune-based therapies.