A Methylome and Transcriptome Analysis of Normal Human Scar Cells Reveals a Role for FOXF2 in Scar Maintenance.

Scars are maintained for life and increase in size during periods of growth such as puberty. Epigenetic changes in fibroblasts after injury may underpin the maintenance and growth of scars. In this study, we combined methylome and transcriptome data from normotrophic mature scar and contralateral uninjured normal skin fibroblasts to identify potential regulators of scar maintenance. In total, 219 significantly differentially expressed and 1,199 significantly differentially methylated promoters were identified, of which there were 12 genes both significantly differentially methylated and expressed. Of these, the two transcription factors, FOXF2 and MKX, were selected for further analysis. Immunocytochemistry and qPCR suggested that FOXF2 but not MKX had elevated expression in scar fibroblasts. Using RNA sequencing, FOXF2 knockdown was shown to significantly reduce the expression of extracellular matrix‒related genes, whereas MKX did not appear to affect similar pathways. Finally, FOXF2 knockdown was also shown to significantly decrease collagen I production in scar and keloid fibroblasts. This study provides insights into the maintenance of normotrophic scar, suggesting that FOXF2 is an important regulator of this process. Targeting genes responsible for maintenance of scar phenotype may ameliorate scar appearance and improve patient outcomes in the future.

Secreted Factors from Keloid Keratinocytes Modulate Collagen Deposition by Fibroblasts from Normal and Fibrotic Tissue: A Pilot Study.

Interactions between keratinocytes and fibroblasts in the skin layers are crucial in normal tissue development, wound healing, and scarring. This study has investigated the role of keloid keratinocytes in regulating collagen production by primary fibroblasts in vitro. Keloid cells were obtained from removed patients' tissue whereas normal skin cells were discarded tissue obtained from elective surgery procedures. Fibroblasts and keratinocytes were isolated, cultured, and a transwell co-culture system were used to investigate the effect of keratinocytes on collagen production using a 'scar-in-a-jar' model. Keloid fibroblasts produced significantly more collagen than normal skin fibroblasts in monoculture at the RNA, secreted protein, and stable fibrillar protein level. When keloid keratinocytes were added to normal skin fibroblasts, expression of collagen was significantly upregulated in most samples, but when added to keloid fibroblasts, collagen I production was significantly reduced. Interestingly, keloid keratinocytes appear to decrease collagen production by keloid fibroblasts. This suggests that signaling in both keratinocytes and fibroblasts is disrupted in keloid pathology.

Verapamil is Less Effective than Triamcinolone for Prevention of Keloid Scar Recurrence After Excision in a Randomized Controlled Trial.

A double-blind randomized controlled trial with a paired split-scar design compared verapamil, an L-type Ca2+ channel antagonist, and triamcinolone for prevention of keloid recurrence after excision. Ca2+ channel blocking activity of verapamil in keloid cells was explored. One keloid was excised per subject and each wound half randomized to receive intralesional injections of triamcinolone (10 mg/ml) or verapamil (2.5 mg/ml) at monthly intervals (4 doses). Interim analysis was performed after 14 subjects were completed. Survival analysis demonstrated significantly higher keloid recurrence with verapamil compared to triamcinolone 12 months post-surgery (log-rank test, p = 0.01) and higher overall risk of recurrence with verapamil (hazard ratio 8.44, 95% CI 1.62-44.05). The study was terminated early according to the stopping guideline (p < 0.05). Verapamil is safe but not as effective as triamcinolone in preventing keloid recurrence after excision. Further study is necessary to determine if clinical response to verapamil is linked to modulation of intracellular Ca2+.

TRAIL+ NK cells control CD4+ T cell responses during chronic viral infection to limit autoimmunity.

Natural killer (NK) cells have been reported to control adaptive immune responses that occur in lymphoid organs at the early stages of immune challenge. The physiological purpose of such regulatory activity remains unclear, because it generally does not confer a survival advantage. We found that NK cells specifically eliminated activated CD4(+) T cells in the salivary gland during chronic murine cytomegalovirus (MCMV) infection. This was dependent on TNF-related apoptosis inducing ligand (TRAIL) expression by NK cells. Although NK cell-mediated deletion of CD4(+) T cells prolonged the chronicity of infection, it also constrained viral-induced autoimmunity. In the absence of this activity, chronic infection was associated with a Sjogren's-like syndrome characterized by focal lymphocytic infiltration into the glands, production of autoantibodies, and reduced saliva and tear secretion. Thus, NK cells are an important homeostatic control that balances the efficacy of adaptive immune responses with the risk of developing autoimmunity.

Regulator of G-protein signaling 5 controls blood pressure homeostasis and vessel wall remodeling.

RATIONALE: Regulator of G-protein signaling 5 (RGS5) modulates G-protein-coupled receptor signaling and is prominently expressed in arterial smooth muscle cells. Our group first reported that RGS5 is important in vascular remodeling during tumor angiogenesis. We hypothesized that RGS5 may play an important role in vessel wall remodeling and blood pressure regulation. OBJECTIVE: To demonstrate that RGS5 has a unique and nonredundant role in the pathogenesis of hypertension and to identify crucial RGS5-regulated signaling pathways. METHODS AND RESULTS: We observed that arterial RGS5 expression is downregulated with chronically elevated blood pressure after angiotensin II infusion. Using a knockout mouse model, radiotelemetry, and pharmacological inhibition, we subsequently showed that loss of RGS5 results in profound hypertension. RGS5 signaling is linked to the renin-angiotensin system and directly controls vascular resistance, vessel contractility, and remodeling. RGS5 deficiency aggravates pathophysiological features of hypertension, such as medial hypertrophy and fibrosis. Moreover, we demonstrate that protein kinase C, mitogen-activated protein kinase/extracellular signal-regulated kinase, and Rho kinase signaling pathways are major effectors of RGS5-mediated hypertension. CONCLUSIONS: Loss of RGS5 results in hypertension. Loss of RGS5 signaling also correlates with hyper-responsiveness to vasoconstrictors and vascular stiffening. This establishes a significant, distinct, and causal role of RGS5 in vascular homeostasis. RGS5 modulates signaling through the angiotensin II receptor 1 and major Gαq-coupled downstream pathways, including Rho kinase. So far, activation of RhoA/Rho kinase has not been associated with RGS molecules. Thus, RGS5 is a crucial regulator of blood pressure homeostasis with significant clinical implications for vascular pathologies, such as hypertension.

Regulator of G protein signaling 5: a new player in vascular remodeling.

Regulators of G protein signaling (RGS) proteins are important modulators of G protein-coupled receptors and, therefore, critical for cardiovascular functions. One family member, RGS5, has recently been identified as a key regulator of vascular remodeling and pericyte maturation in tumors. Here, we discuss a potential role for RGS5 and its relatives, RGS2 and 4, within the cardiovascular system. Insights into RGS5 signaling are likely to be highly significant for vascular pathologies such as hypertension, atherosclerosis, and angiogenesis.

Modulation of g protein signaling normalizes tumor vessels.

G protein-coupled biological processes are important for an ever-increasing number of human diseases and require fine-tuning through accessory molecules such as the regulators of G protein signaling (RGS). RGS5, a marker for tumor-resident pericytes, was recently established as playing a pivotal role in vascular maturation and vessel remodeling during carcinogenesis. Remarkably, tumors arising in a RGS5-deficient background display vessels with normalized morphology and an overall improved blood flow. Furthermore, these morphologic changes also lead to dramatic improvements in lymphocyte access to tumors and success of antitumor immunotherapy. Here, we consider the implications of these findings, and how they contribute to enhancing our understanding of remodeling angiogenic vessels as means for improving anticancer therapies.

Modulation of the "blood-tumor" barrier improves immunotherapy.

Blood vessels inside tumors are crucial for cancer survival and progression but equally contribute to the tumor's intrinsic resistance to therapy. Abnormal blood flow in the local tumor environment acts as a physiological barrier to the delivery of chemotherapeutic agents. Furthermore, tumor vasculature can also act as a barrier for immune cell migration into the tumor parenchyma. Much has been made of anti-angiogenic therapies that specifically inhibit vessel growth. However, recent findings demonstrate that the chaotic architecture of tumor blood vessels can be reversed which in turn normalizes blood flow and physical parameters in the tumor environment. Importantly, vessel normalization also improves lymphocyte migration into tumor tissue and immune destruction. Identification of regulator of G protein signaling 5 (RGS5) as a key modulator of the vascular barrier in tumor progression and regression has brought new insights into the molecular basis of vessel normalization and opens new therapeutic opportunities.

Vascular normalization in Rgs5-deficient tumours promotes immune destruction.

The vasculature of solid tumours is morphologically aberrant and characterized by dilated and fragile vessels, intensive vessel sprouting and loss of hierarchical architecture. Constant vessel remodelling leads to spontaneous haemorrhages and increased interstitial fluid pressure in the tumour environment. Tumour-related angiogenesis supports tumour growth and is also a major obstacle for successful immune therapy as it prevents migration of immune effector cells into established tumour parenchyma. The molecular mechanisms for these angiogenic alterations are largely unknown. Here we identify regulator of G-protein signalling 5 (Rgs5) as a master gene responsible for the abnormal tumour vascular morphology in mice. Loss of Rgs5 results in pericyte maturation, vascular normalization and consequent marked reductions in tumour hypoxia and vessel leakiness. These vascular and intratumoral changes enhance influx of immune effector cells into tumour parenchyma and markedly prolong survival of tumour-bearing mice. This is the first demonstration, to our knowledge, of reduced tumour angiogenesis and improved immune therapeutic outcome on loss of a vascular gene function and establishes a previously unrecognized role of G-protein signalling in tumour angiogenesis.

NK gene complex haplotype variability and host resistance alleles to murine cytomegalovirus in wild mouse populations.

The NK gene complex (NKC) on mouse chromosome 6 encodes receptors that are expressed on NK cells, such as Ly49H, and is involved in regulating NK cell control of virus infections, such as murine cytomegalovirus (MCMV). In the present study, we investigated the level of allelic heterogeneity in NKC loci in populations of outbred wild mice. This work revealed extensive levels of heterogeneity within two wild mouse populations. Analysis of MCMV replication in a population of specific pathogen-free outbred wild mice revealed that low viral titres, which are normally associated with the Cmv1(r) allele of the Cmv1 host resistance locus, were not prevalent in the mice tested. Hence, NKC-mediated resistance associated with Cmv1(r)/Ly49H-like effects was rare in this population. Overall, these data indicate that the NKC region is highly polymorphic and thus it is very likely that it confers on mice sufficient variability to cope with infection by a range of pathogens.

A novel checkpoint in the Bcl-2-regulated apoptotic pathway revealed by murine cytomegalovirus infection of dendritic cells.

Infection with murine cytomegalovirus (MCMV) has contributed to understanding many aspects of human infection and, additionally, has provided important insight to understanding complex cellular responses. Dendritic cells (DCs) are a major target for MCMV infection. Here, we analyze the effects of MCMV infection on DC viability, and show that infected DCs become resistant to apoptosis induced by growth factor deprivation. The precise contribution of changes in the expression of Bcl-2 family proteins has been assessed and a new checkpoint in the apoptotic pathway identified. Despite their resistance to apoptosis, MCMV-infected DCs showed Bax to be tightly associated with mitochondria and, together with Bak, forming high molecular weight oligomers, changes normally associated with apoptotic cell death. Exposure of a constitutively occluded Bax NH2-terminal epitope was blocked after infection. These results suggest that MCMV has evolved a novel strategy for inhibiting apoptosis and provide evidence that apoptosis can be regulated after translocation, integration, and oligomerization of Bax at the mitochondrial membrane.