CD44 and RHAMM Are Microenvironmental Sensors with Dual Metastasis Promoter and Suppressor Functions.

The progression of primary tumors to metastases remains a significant roadblock to the treatment of most cancers. Emerging evidence has identified genes that specifically affect metastasis and are potential therapeutic targets for managing tumor progression. However, these genes can have dual tumor promoter and suppressor functions that are contextual in manifestation, and that complicate their development as targeted therapies. CD44 and RHAMM/HMMR are examples of multifunctional proteins that can either promote or suppress metastases, as demonstrated in experimental models. These two proteins can be viewed as microenvironmental sensors and this minireview addresses the known mechanistic underpinnings that may determine their metastasis suppressor versus promoter functions. Leveraging this mechanistic knowledge for CD44, RHAMM, and other multifunctional proteins is predicted to improve the precision of therapeutic targeting to achieve more effective management of metastasis.

RHAMM regulates MMTV-PyMT-induced lung metastasis by connecting STING-dependent DNA damage sensing to interferon/STAT1 pro-apoptosis signaling.

BACKGROUND: RHAMM is a multifunctional protein that is upregulated in breast tumors, and the presence of strongly RHAMM+ve cancer cell subsets associates with elevated risk of peripheral metastasis. Experimentally, RHAMM impacts cell cycle progression and cell migration. However, the RHAMM functions that contribute to breast cancer metastasis are poorly understood. METHODS: We interrogated the metastatic functions of RHAMM using a loss-of-function approach by crossing the MMTV-PyMT mouse model of breast cancer susceptibility with Rhamm-/- mice. In vitro analyses of known RHAMM functions were performed using primary tumor cell cultures and MMTV-PyMT cell lines. Somatic mutations were identified using a mouse genotyping array. RNA-seq was performed to identify transcriptome changes resulting from Rhamm-loss, and SiRNA and CRISPR/Cas9 gene editing was used to establish cause and effect of survival mechanisms in vitro. RESULTS: Rhamm-loss does not alter initiation or growth of MMTV-PyMT-induced primary tumors but unexpectedly increases lung metastasis. Increased metastatic propensity with Rhamm-loss is not associated with obvious alterations in proliferation, epithelial plasticity, migration, invasion or genomic stability. SNV analyses identify positive selection of Rhamm-/- primary tumor clones that are enriched in lung metastases. Rhamm-/- tumor clones are characterized by an increased ability to survive with ROS-mediated DNA damage, which associates with blunted expression of interferon pathway and target genes, particularly those implicated in DNA damage-resistance. Mechanistic analyses show that ablating RHAMM expression in breast tumor cells by siRNA knockdown or CRISPR-Cas9 gene editing blunts interferon signaling activation by STING agonists and reduces STING agonist-induced apoptosis. The metastasis-specific effect of RHAMM expression-loss is linked to microenvironmental factors unique to tumor-bearing lung tissue, notably high ROS and TGFB levels. These factors promote STING-induced apoptosis of RHAMM+ve tumor cells to a significantly greater extent than RHAMM-ve comparators. As predicted by these results, colony size of Wildtype lung metastases is inversely related to RHAMM expression. CONCLUSION: RHAMM expression-loss blunts STING-IFN signaling, which offers growth advantages under specific microenvironmental conditions of lung tissue. These results provide mechanistic insight into factors controlling clonal survival/expansion of metastatic colonies and has translational potential for RHAMM expression as a marker of sensitivity to interferon therapy.

Receptor for hyaluronan-mediated motility (RHAMM) defines an invasive niche associated with tumor progression and predicts poor outcomes in breast cancer patients.

Breast cancer invasion and metastasis result from a complex interplay between tumor cells and the tumor microenvironment (TME). Key oncogenic changes in the TME include aberrant synthesis, processing, and signaling of hyaluronan (HA). Hyaluronan-mediated motility receptor (RHAMM, CD168; HMMR) is an HA receptor enabling tumor cells to sense and respond to this aberrant TME during breast cancer progression. Previous studies have associated RHAMM expression with breast tumor progression; however, cause and effect mechanisms are incompletely established. Focused gene expression analysis of an internal breast cancer patient cohort confirmed that increased RHAMM expression correlates with aggressive clinicopathological features. To probe mechanisms, we developed a novel 27-gene RHAMM-related signature (RRS) by intersecting differentially expressed genes in lymph node (LN)-positive patient cases with the transcriptome of a RHAMM-dependent model of cell transformation, which we validated in an independent cohort. We demonstrate that the RRS predicts for poor survival and is enriched for cell cycle and TME-interaction pathways. Further analyses using CRISPR/Cas9-generated RHAMM-/- breast cancer cells provided direct evidence that RHAMM promotes invasion in vitro and in vivo. Immunohistochemistry studies highlighted heterogeneous RHAMM protein expression, and spatial transcriptomics associated the RRS with RHAMM-high microanatomic foci. We conclude that RHAMM upregulation leads to the formation of 'invasive niches', which are enriched in RRS-related pathways that drive invasion and could be targeted to limit invasive progression and improve patient outcomes. © 2023 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

Hyaluronan Functions in Wound Repair That Are Captured to Fuel Breast Cancer Progression.

Signaling from an actively remodeling extracellular matrix (ECM) has emerged as a critical factor in regulating both the repair of tissue injuries and the progression of diseases such as metastatic cancer. Hyaluronan (HA) is a major component of the ECM that normally functions in tissue injury to sequentially promote then suppress inflammation and fibrosis, a duality in which is featured, and regulated in, wound repair. These essential response-to-injury functions of HA in the microenvironment are hijacked by tumor cells for invasion and avoidance of immune detection. In this review, we first discuss the numerous size-dependent functions of HA and emphasize the multifunctional nature of two of its receptors (CD44 and RHAMM) in regulating the signaling duality of HA in excisional wound healing. This is followed by a discussion of how HA metabolism is de-regulated in malignant progression and how targeting HA might be used to better manage breast cancer progression.

RHAMM Is a Multifunctional Protein That Regulates Cancer Progression.

The functional complexity of higher organisms is not easily accounted for by the size of their genomes. Rather, complexity appears to be generated by transcriptional, translational, and post-translational mechanisms and tissue organization that produces a context-dependent response of cells to specific stimuli. One property of gene products that likely increases the ability of cells to respond to stimuli with complexity is the multifunctionality of expressed proteins. Receptor for hyaluronan-mediated motility (RHAMM) is an example of a multifunctional protein that controls differential responses of cells in response-to-injury contexts. Here, we trace its evolution into a sensor-transducer of tissue injury signals in higher organisms through the detection of hyaluronan (HA) that accumulates in injured microenvironments. Our goal is to highlight the domain and isoform structures that generate RHAMM's function complexity and model approaches for targeting its key functions to control cancer progression.

Cell-specific expression of the transcriptional regulator RHAMM provides a timing mechanism that controls appropriate wound re-epithelialization.

Prevention of aberrant cutaneous wound repair and appropriate regeneration of an intact and functional integument require the coordinated timing of fibroblast and keratinocyte migration. Here, we identified a mechanism whereby opposing cell-specific motogenic functions of a multifunctional intracellular and extracellular protein, the receptor for hyaluronan-mediated motility (RHAMM), coordinates fibroblast and keratinocyte migration speed and ensures appropriate timing of excisional wound closure. We found that, unlike in WT mice, in Rhamm-null mice, keratinocyte migration initiates prematurely in the excisional wounds, resulting in wounds that have re-surfaced before the formation of normal granulation tissue, leading to a defective epidermal architecture. We also noted aberrant keratinocyte and fibroblast migration in the Rhamm-null mice, indicating that RHAMM suppresses keratinocyte motility but increases fibroblast motility. This cell context-dependent effect resulted from cell-specific regulation of extracellular signal-regulated kinase 1/2 (ERK1/2) activation and expression of a RHAMM target gene encoding matrix metalloprotease 9 (MMP-9). In fibroblasts, RHAMM promoted ERK1/2 activation and MMP-9 expression, whereas in keratinocytes, RHAMM suppressed these activities. In keratinocytes, loss of RHAMM function or expression promoted epidermal growth factor receptor-regulated MMP-9 expression via ERK1/2, which resulted in cleavage of the ectodomain of the RHAMM partner protein CD44 and thereby increased keratinocyte motility. These results identify RHAMM as a key factor that integrates the timing of wound repair by controlling cell migration.

Persistent myopathy despite release of partial obstruction: in vivo reversal of dysfunction and transcriptional responses using rapamycin.

Current and potential medical therapy for obstruction-induced myopathic bladder dysfunction (from benign prostatic hyperplasia or posterior urethral valves) focuses on symptoms. The persistent tissue pathology and dysfunction after release of obstruction is often deemed irreversible without any systematic therapeutic approaches. As rapamycin can attenuate bladder smooth muscle hypertrophy and dysfunction during the genesis of partial obstruction in vivo, we tested whether rapamycin could improve persistent function after release of obstruction (de-obstruction or REL). Female Sprague-Dawley rat bladders were partially obstructed (PBO) by suturing around both the urethra and a para-urethral steel rod, then removing the rod. One day prior to release of obstruction (preREL), voiding parameters and residual urine volume of preREL+future rapa, preREL+future veh groups were recorded. Release of obstruction (REL) was performed by suture removal following 6 weeks of PBO. For 4 more weeks after the de-obstruction, REL animals were randomized to rapamycin (REL+rapa) or vehicle (REL+veh). PBO for 6 weeks were used as positive controls. In shams, the urethra was exposed, but no suture tied. Voiding parameters and residual urine volume were measured prior to sacrifice of sham and REL+veh or REL+rapa, and PBO. Rapamycin efficacy was tested by pair-wise comparison of changes in individual voiding data from preREL+future veh or preREL+future rapa versus REL+veh or REL+rapa, respectively, as well as by comparisons of REL+veh to REL+rapa groups. Bladders were weighed and processed for a high-throughput QPCR array, and histopathology. Bladder/body mass ratios with PBO increased significantly and remained higher in the release phase in REL+veh animals. REL+rapa versus REL+veh improved residual volumes and micturition fractions toward sham levels. Three genes encoding extracellular proteins, BMP2, SOD3, and IGFBP7, correlated with functional improvement by Pearson's correlations. The promoters of these genes showed enrichment for several motifs including circadian E-boxes. While obstruction and REL augmented CLOCK and NPAS2 expression above sham levels, rapamycin treatment during release significantly blocked their expression. This experimental design of pharmaco-intervention during the de-obstruction phase revealed a novel pathway dysregulated during the clinically relevant treatment phase of obstructive bladder myopathy.

Creating a Favorable Microenvironment for Fat Grafting in a Novel Model of Radiation-Induced Mammary Fat Pad Fibrosis.

BACKGROUND: Radiofibrosis of breast tissue compromises breast reconstruction by interfering with tissue viability and healing. Autologous fat transfer may reduce radiotherapy-related tissue injury, but graft survival is compromised by the fibrotic microenvironment. Elevated expression of receptor for hyaluronan-mediated motility (RHAMM; also known as hyaluronan-mediated motility receptor, or HMMR) in wounds decreases adipogenesis and increases fibrosis. The authors therefore developed RHAMM peptide mimetics to block RHAMM profibrotic signaling following radiation. They propose that this blocking peptide will decrease radiofibrosis and establish a microenvironment favoring adipose-derived stem cell survival using a rat mammary fat pad model. METHODS: Rat mammary fat pads underwent a one-time radiation dose of 26 Gy. Irradiated (n = 10) and nonirradiated (n = 10) fat pads received a single intramammary injection of a sham injection or peptide NPI-110. Skin changes were examined clinically. Mammary fat pad tissue was processed for fibrotic and adipogenic markers using quantitative polymerase chain reaction and immunohistochemical analysis. RESULTS: Clinical assessments and molecular analysis confirmed radiation-induced acute skin changes and radiation-induced fibrosis in rat mammary fat pads. Peptide treatment reduced fibrosis, as detected by polarized microscopy of picrosirius red staining, increased collagen ratio of 3:1, reduced expression of collagen-1 crosslinking enzymes lysyl-oxidase, transglutaminase 2, and transforming growth factor ß1 protein, and increased adiponectin, an antifibrotic adipokine. RHAMM was expressed in stromal cell subsets and was downregulated by the RHAMM peptide mimetic. CONCLUSION: Results from this study predict that blocking RHAMM function in stromal cell subsets can provide a postradiotherapy microenvironment more suitable for fat grafting and breast reconstruction.

Dissecting the Dual Nature of Hyaluronan in the Tumor Microenvironment.

Hyaluronan (HA) is a glycosaminoglycan with a simple structure but diverse and often opposing functions. The biological activities of this polysaccharide depend on its molecular weight and the identity of interacting receptors. HA is initially synthesized as high molecular-weight (HMW) polymers, which maintain homeostasis and restrain cell proliferation and migration in normal tissues. These HMW-HA functions are mediated by constitutively expressed receptors including CD44, LYVE-1, and STABILIN2. During normal processes such as tissue remodeling and wound healing, HMW-HA is fragmented into low molecular weight polymers (LMW-HA) by hyaluronidases and free radicals, which promote inflammation, immune cell recruitment and the epithelial cell migration. These functions are mediated by RHAMM and TLR2,4, which coordinate signaling with CD44 and other HA receptors. Tumor cells hijack the normally tightly regulated HA production/fragmentation associated with wound repair/remodeling, and these HA functions participate in driving and maintaining malignant progression. However, elevated HMW-HA production in the absence of fragmentation is linked to cancer resistance. The controlled production of HA polymer sizes and their functions are predicted to be key to dissecting the role of microenvironment in permitting or restraining the oncogenic potential of tissues. This review focuses on the dual nature of HA in cancer initiation vs. resistance, and the therapeutic potential of HA for chemo-prevention and as a target for cancer management.

A truncated RHAMM protein for discovering novel therapeutic peptides.

The receptor for hyaluronan mediated motility (RHAMM, gene name HMMR) belongs to a group of proteins that bind to hyaluronan (HA), a high-molecular weight anionic polysaccharide that has pro-angiogenic and inflammatory properties when fragmented. We propose to use a chemically synthesized, truncated version of the protein (706-767), 7 kDa RHAMM, as a target receptor in the screening of novel peptide-based therapeutic agents. Chemical synthesis by Fmoc-based solid-phase peptide synthesis, and optimization using pseudoprolines, results in RHAMM protein of higher purity and yield than synthesis by recombinant protein production. 7 kDa RHAMM was evaluated for its secondary structure, ability to bind the native ligand, HA, and its bioactivity. This 62-amino acid polypeptide replicates the HA binding properties of both native and recombinant RHAMM protein. Furthermore, tubulin-derived HA peptide analogues that bind to recombinant RHAMM and were previously reported to compete with HA for interactions with RHAMM, bind with a similar affinity and specificity to the 7 kDa RHAMM. Therefore, in terms of its key binding properties, the 7 kDa RHAMM mini-protein is a suitable replacement for the full-length recombinant protein.

Spatial statistical tools for genome-wide mutation cluster detection under a microarray probe sampling system.

Mutation cluster analysis is critical for understanding certain mutational mechanisms relevant to genetic disease, diversity, and evolution. Yet, whole genome sequencing for detection of mutation clusters is prohibitive with high cost for most organisms and population surveys. Single nucleotide polymorphism (SNP) genotyping arrays, like the Mouse Diversity Genotyping Array, offer an alternative low-cost, screening for mutations at hundreds of thousands of loci across the genome using experimental designs that permit capture of de novo mutations in any tissue. Formal statistical tools for genome-wide detection of mutation clusters under a microarray probe sampling system are yet to be established. A challenge in the development of statistical methods is that microarray detection of mutation clusters is constrained to select SNP loci captured by probes on the array. This paper develops a Monte Carlo framework for cluster testing and assesses test statistics for capturing potential deviations from spatial randomness which are motivated by, and incorporate, the array design. While null distributions of the test statistics are established under spatial randomness via the homogeneous Poisson process, power performance of the test statistics is evaluated under postulated types of Neyman-Scott clustering processes through Monte Carlo simulation. A new statistic is developed and recommended as a screening tool for mutation cluster detection. The statistic is demonstrated to be excellent in terms of its robustness and power performance, and useful for cluster analysis in settings of missing data. The test statistic can also be generalized to any one dimensional system where every site is observed, such as DNA sequencing data. The paper illustrates how the informal graphical tools for detecting clusters may be misleading. The statistic is used for finding clusters of putative SNP differences in a mixture of different mouse genetic backgrounds and clusters of de novo SNP differences arising between tissues with development and carcinogenesis.

Hyaluronan Isolation from Mouse Mammary Gland.

The glycosaminoglycan hyaluronan (HA) is a key component of the extracellular matrix. The molecular weight of HA is heterogeneous and can reach from several million to several hundred daltons. The effect of HA on cell behavior is size dependent; fragmented HA acts as a danger signal, stimulates cell migration and proliferation and is proinflammatory, native high molecular weight HA suppresses inflammation. Therefore, it is important to analyze HA size distribution when studying the role of HA in tissue homeostasis and pathology. This protocol describes isolation of HA from mouse mammary glands but can also be applied to other tissues. The quality of the isolated HA is sufficient to analyze size distribution by gel electrophoresis ( Calabro et al., 2000 ).

Mouse Mammary Gland Whole Mount Preparation and Analysis.

The mammary gland undergoes extensive remodeling during pregnancy and is also subject to neoplastic processes both of which result in histological changes of the gland epithelial structure. Since the mammary tree is a complex three-dimensional structure a method is needed that provides an overview of the entire gland. Whole mounts provide this information, are inexpensive and do not require specialized equipment. This protocol describes mammary gland isolation, whole mount preparation and analysis. Mammary gland tissue, which is removed postmortem, is stained with Carmine Alum, a nuclear stain, allowing detection of epithelial structures embedded in the adipose tissue of the mammary fat pad. Stained mammary glands are imaged by light microscopy or embedded and sectioned for histological examination. Image analysis software such as Image J can be used to quantify extensity of branching complexity, epithelial structure remodeling or hyperplastic changes.

Hyaluronan modulates growth factor induced mammary gland branching in a size dependent manner.

Mammary gland morphogenesis begins during fetal development but expansion of the mammary tree occurs postnatally in response to hormones, growth factors and extracellular matrix. Hyaluronan (HA) is an extracellular matrix polysaccharide that has been shown to modulate growth factor-induced branching in culture. Neither the physiological relevance of HA to mammary gland morphogenesis nor the role that HA receptors play in these responses are currently well understood. We show that HA synthase (HAS2) is expressed in both ductal epithelia and stromal cells but HA primarily accumulates in the stroma. HA accumulation and expression of the HA receptors CD44 and RHAMM are highest during gestation when gland remodeling, lateral branch infilling and lobulo-alveoli formation is active. Molecular weight analyses show that approximately 98% of HA at all stages of morphogenesis is >300kDa. Low levels of 7-114kDa HA fragments are also detected and in particular the accumulation of 7-21kDa HA fragments are significantly higher during gestation than other morphogenetic stages (p<0.05). Using these in vivo results as a guide, in culture analyses of mammary epithelial cell lines (EpH4 and NMuMG) were performed to determine the roles of high molecular weight, 7-21kDa (10kDa MWavg) and HA receptors in EGF-induced branching morphogenesis. Results of these assays show that while HA synthesis is required for branching and 10kDa HA fragments strongly stimulate branching, the activity of HA decreases with increasing molecular weight and 500kDa HA strongly inhibits this morphogenetic process. The response to 10kDa HA requires RHAMM function and genetic deletion of RHAMM transiently blunts lateral branching in vivo. Collectively, these results reveal distinct roles for HA polymer size in modulating growth factor induced mammary gland branching and implicates these polymers in both the expansion and sculpting of the mammary tree during gestation.

Uropathogenic E. coli (UPEC) Infection Induces Proliferation through Enhancer of Zeste Homologue 2 (EZH2).

UNLABELLED: Host-pathogen interactions can induce epigenetic changes in the host directly, as well as indirectly through secreted factors. Previously, uropathogenic Escherichia coli (UPEC) was shown to increase DNA methyltransferase activity and expression, which was associated with methylation-dependent alterations in the urothelial expression of CDKN2A. Here, we showed that paracrine factors from infected cells alter expression of another epigenetic writer, EZH2, coordinate with proliferation. Urothelial cells were inoculated with UPEC, UPEC derivatives, or vehicle (mock infection) at low moi, washed, then maintained in media with Gentamycin. Urothelial conditioned media (CM) and extracellular vesicles (EV) were isolated after the inoculations and used to treat naïve urothelial cells. EZH2 increased with UPEC infection, inoculation-induced CM, and inoculation-induced EV vs. parallel stimulation derived from mock-inoculated urothelial cells. We found that infection also increased proliferation at one day post-infection, which was blocked by the EZH2 inhibitor UNC1999. Inhibition of demethylation at H3K27me3 had the opposite effect and augmented proliferation. CONCLUSION: Uropathogen-induced paracrine factors act epigenetically by altering expression of EZH2, which plays a key role in early host cell proliferative responses to infection.

Uncovering the dual role of RHAMM as an HA receptor and a regulator of CD44 expression in RHAMM-expressing mesenchymal progenitor cells.

The interaction of hyaluronan (HA) with mesenchymal progenitor cells impacts trafficking and fate after tissue colonization during wound repair and these events contribute to diseases such as cancer. How this interaction occurs is poorly understood. Using 10T½ cells as a mesenchymal progenitor model and fluorescent (F-HA) or gold-labeled HA (G-HA) polymers, we studied the role of two HA receptors, RHAMM and CD44, in HA binding and uptake in non-adherent and adherent mesenchymal progenitor (10T½) cells to mimic aspects of cell trafficking and tissue colonization. We show that fluorescent labeled HA (F-HA) binding/uptake was high in non-adherent cells but dropped over time as cells became increasingly adherent. Non-adherent cells displayed both CD44 and RHAMM but only function-blocking anti-RHAMM and not anti-CD44 antibodies significantly reduced F-HA binding/uptake. Adherent cells, which also expressed CD44 and RHAMM, primarily utilized CD44 to bind to F-HA since anti-CD44 but not anti-RHAMM antibodies blocked F-HA uptake. RHAMM overexpression in adherent 10T½ cells led to increased F-HA uptake but this increased binding remained CD44 dependent. Further studies showed that RHAMM-transfection increased CD44 mRNA and protein expression while blocking RHAMM function reduced expression. Collectively, these results suggest that cellular microenvironments in which these receptors function as HA binding proteins differ significantly, and that RHAMM plays at least two roles in F-HA binding by acting as an HA receptor in non-attached cells and by regulating CD44 expression and display in attached cells. Our findings demonstrate adhesion-dependent mechanisms governing HA binding/ uptake that may impact development of new mesenchymal cell-based therapies.

Identification, design and synthesis of tubulin-derived peptides as novel hyaluronan mimetic ligands for the receptor for hyaluronan-mediated motility (RHAMM/HMMR).

Fragments of the extracellular matrix component hyaluronan (HA) promote tissue inflammation, fibrosis and tumor progression. HA fragments act through HA receptors including CD44, LYVE1, TLR2, 4 and the receptor for hyaluronan mediated motility (RHAMM/HMMR). RHAMM is a multifunctional protein with both intracellular and extracellular roles in cell motility and proliferation. Extracellular RHAMM binds directly to HA fragments while intracellular RHAMM binds directly to ERK1 and tubulin. Both HA and regions of tubulin (s-tubulin) are anionic and bind to basic amino acid-rich regions in partner proteins, such as in HA and tubulin binding regions of RHAMM. We used this as a rationale for developing bioinformatics and SPR (surface plasmon resonance) based screening to identify high affinity anionic RHAMM peptide ligands. A library of 12-mer peptides was prepared based on the carboxyl terminal tail sequence of s-tubulin isoforms and assayed for their ability to bind to the HA/tubulin binding region of recombinant RHAMM using SPR. This approach resulted in the isolation of three 12-mer peptides with nanomolar affinity for RHAMM. These peptides bound selectively to RHAMM but not to CD44 or TLR2,4 and blocked RHAMM:HA interactions. Furthermore, fluorescein-peptide uptake by PC3MLN4 prostate cancer cells was blocked by RHAMM mAb but not by CD44 mAb. These peptides also reduced the ability of prostate cancer cells to degrade collagen type I. The selectivity of these novel HA peptide mimics for RHAMM suggest their potential for development as HA mimetic imaging and therapeutic agents for HA-promoted disease.

Hyaluronan-phosphatidylethanolamine polymers form pericellular coats on keratinocytes and promote basal keratinocyte proliferation.

Aged keratinocytes have diminished proliferative capacity and hyaluronan (HA) cell coats, which are losses that contribute to atrophic skin characterized by reduced barrier and repair functions. We formulated HA-phospholipid (phosphatidylethanolamine, HA-PE) polymers that form pericellular coats around cultured dermal fibroblasts independently of CD44 or RHAMM display. We investigated the ability of these HA-PE polymers to penetrate into aged mouse skin and restore epidermal function in vivo. Topically applied Alexa(647)-HA-PE penetrated into the epidermis and dermis, where it associated with both keratinocytes and fibroblasts. In contrast, Alexa(647)-HA was largely retained in the outer cornified layer of the epidermis and quantification of fluorescence confirmed that significantly more Alexa(647)-HA-PE penetrated into and was retained within the epidermis than Alexa(647)-HA. Multiple topical applications of HA-PE to shaved mouse skin significantly stimulated basal keratinocyte proliferation and epidermal thickness compared to HA or vehicle cream alone. HA-PE had no detectable effect on keratinocyte differentiation and did not promote local or systemic inflammation. These effects of HA-PE polymers are similar to those reported for endogenous epidermal HA in youthful skin and show that topical application of HA-PE polymers can restore some of the impaired functions of aged epidermis.

Hyaluronan and RHAMM in wound repair and the "cancerization" of stromal tissues.

Tumors and wounds share many similarities including loss of tissue architecture, cell polarity and cell differentiation, aberrant extracellular matrix (ECM) remodeling (Ballard et al., 2006) increased inflammation, angiogenesis, and elevated cell migration and proliferation. Whereas these changes are transient in repairing wounds, tumors do not regain tissue architecture but rather their continued progression is fueled in part by loss of normal tissue structure. As a result tumors are often described as wounds that do not heal. The ECM component hyaluronan (HA) and its receptor RHAMM have both been implicated in wound repair and tumor progression. This review highlights the similarities and differences in their roles during these processes and proposes that RHAMM-regulated wound repair functions may contribute to "cancerization" of the tumor microenvironment.