Immobilized epidermal growth factor stimulates persistent, directed keratinocyte migration via activation of PLCγ1

Self-assembled nanoparticles of hybrid elastin-like and Oncostatin M polymers for improved wound healing

Oncostatin M (OSM) is a pleiotropic cytokine that can significantly enhance wound healing. Here, we report on the use of nanoparticles (NPs) formulated from a genetically engineered A200_hOSM protein polymer, which combines an elastin-like recombinamer (A200) with human OSM (hOSM) in the same molecule, aiming at enhancing wound healing processes. A200_hOSM NPs were obtained by self-assembly and evaluated for their bioactivity in human keratinocytes and fibroblasts. The NPs demonstrated superior efficacy in promoting cell proliferation in a dose-dependent manner, exhibiting nearly threefold greater proliferation at 48 and 72 h, compared to cells treated with commercial hOSM. Moreover, the NPs stimulated cell migration and collagen production through activation of JAK/STAT3 signaling. They also promoted the production of IL-6 and IL-8, pro-inflammatory cytokines with a critical role for wound healing. Promotion of keratinocyte proliferation and differentiation were further validated in non-commercial 3D skin equivalents. The A200_hOSM NPs revealed potential in accelerating wound healing, evidenced by reduced wound size and a thicker epidermal layer. This system represents a significant advancement in the field of bioinspired biomaterials by improving cytokine bioavailability, allowing for localized therapy and offering a cost-effective strategy for employing hOSM in wound healing management.

Growth factors IGF-1 and KGF and adipose-derived stem cells promote migration and viability of primary human keratinocytes in an in vitro wound model

Introduction

In the field of plastic surgery, epidermal transplantation is a potential treatment for chronic wounds that results in only minor donor site morbidity. Improving the regenerative capacities of epidermal grafts or single-cell suspensions and therefore accelerating healing processes would be of significant interest.

Methods

In the present study, we analyzed the effects of growth factors and adipose-derived stem cells (ADSCs) on keratinocyte properties. For optimum translation into the clinical setting, primary human keratinocytes and patient-matched ADSCs were isolated and used in an in vitro wound model.

Results

The keratinocyte migration and viability increased after treatment with the growth factors insulin-like growth factor 1 (IGF-1) and keratinocyte growth factor (KGF). A similar effect was observed with the use of a concentrated ADSC-conditioned medium (ADSC-CM). It was further possible to isolate the keratinocytes in a xenogen-free medium, which is essential for clinical translation. Importantly, a patient-dependent influence on the effects of the growth factors and ADSC-CM was observed.

Discussion

This study provides potential for the improvement of epidermal transplantation in the treatment of chronic wounds using xenogen-free isolated and cultivated keratinocytes, growth factors, and ADSC. Translating these results into clinical application may help accelerate wound healing and shorten the time until patients can return to everyday life.

Epidermal Growth Factor Intralesional Delivery in Chronic Wounds: The Pioneer and Standalone Technique for Reversing Wound Chronicity and Promoting Sustainable Healing

The early expectations about growth factors' (GFs') discovery as an undisputed therapeutic solution for chronic wounds progressively eclipsed when they failed to accelerate acute wound closure and restore the healing trajectory of stagnant ulcers. Critical knowledge about chronic wound biology and GF pharmacology was a conundrum at that time. Diabetes undermines keratinocytes' and fibroblasts' physiology, impairing skin healing abilities. Diabetic ulcers, as other chronic wounds, are characterized by hyperinflammation, unbalanced proteolytic activity, catabolism, and free radical cytotoxicity. This hostile scenario for the chemical stability, integrity, and functionality of GFs led to the conclusion that topical administration may jeopardize GFs' clinical effectiveness. Epidermal growth factor (EGF) has a proximal position in tissues homeostasis by activating survival and mitogenic pathways from embryonic life to adulthood. Seminal experiments disclosed unprecedented pharmacological bounties of parenterally administered EGF. Accordingly, the experience accumulated for more than 20 years of EGF intralesional infiltration of diabetic wound bottoms and edges has translated into sustained healing responses, such as low recurrences and amputation rates. This delivery route, in addition to being safe and tolerated, has shown to restore a variety of circulating biochemical markers ordinarily disturbed in diabetic conditions. EGF infiltration triggers a cascade of local fibroblast reactions, supporting its molecular integrity, prolonged mean residence time, and ultimately eliciting its receptor trafficking and nuclear translocation. The intralesional delivery route seems to warrant that EGF reaches wound fibroblasts' epigenetic core, mitigating the consequences of metabolic memory imprinting.

Cellular context alters EGF-induced ERK dynamics and reveals potential crosstalk with GDF-15

Cellular signaling dynamics are sensitive to differences in ligand identity, levels, and temporal patterns. These signaling patterns are also impacted by the larger context that the cell experiences (i.e., stimuli such as media formulation or substrate stiffness that are constant in an experiment exploring a particular variable but may differ between independent experiments which explore that variable) although the reason for different dynamics is not always obvious. Here, we compared extracellular-regulated kinase (ERK) signaling in response to epidermal growth factor treatment of human mammary epithelial cells cultures in either well culture or a microfluidic device. Using a single-cell ERK kinase translocation reporter, we observed extended ERK activation in well culture and only transient activity in microfluidic culture. The activity in microfluidic culture resembled that of the control condition, suggesting that shear stress led to the early activity and a loss of autocrine factors dampened extended signaling. Through experimental analysis we identified growth differentiation factor-15 as a candidate factor that led to extended ERK activation through a protein kinase C-α/β dependent pathway. Our results demonstrate that context impacts ERK dynamics and that comparison of distinct contexts can be used to elucidate new aspects of the cell signaling network.

Cutaneous innervation in impaired diabetic wound healing

Type 2 diabetes is associated with several potential comorbidities, among them impaired wound healing, chronic ulcerations, and the requirement for lower extremity amputation. Disease-associated abnormal cellular responses, infection, immunological and microvascular dysfunction, and peripheral neuropathy are implicated in the pathogenesis of the wound healing impairment and the diabetic foot ulcer. The skin houses a dense network of sensory nerve afferents and nerve-derived modulators, which communicate with epidermal keratinocytes and dermal fibroblasts bidirectionally to effect normal wound healing after trauma. However, the mechanisms through which cutaneous innervation modulates wound healing are poorly understood, especially in humans. Better understanding of these mechanisms may provide the basis for targeted treatments for chronic diabetic wounds. This review provides an overview of wound healing pathophysiology with a focus on neural involvement in normal and diabetic wound healing, as well as future therapeutic perspectives to address the unmet needs of diabetic patients with chronic wounds.

Immobilization of Growth Factors for Cell Therapy Manufacturing

Cell therapy products exhibit great therapeutic potential but come with a deterring price tag partly caused by their costly manufacturing processes. The development of strategies that lead to cost-effective cell production is key to expand the reach of cell therapies. Growth factors are critical culture media components required for the maintenance and differentiation of cells in culture and are widely employed in cell therapy manufacturing. However, they are expensive, and their common use in soluble form is often associated with decreased stability and bioactivity. Immobilization has emerged as a possible strategy to optimize growth factor use in cell culture. To date, several immobilization techniques have been reported for attaching growth factors onto a variety of biomaterials, but these have been focused on tissue engineering. This review briefly summarizes the current landscape of cell therapy manufacturing, before describing the types of chemistry that can be used to immobilize growth factors for cell culture. Emphasis is placed to identify strategies that could reduce growth factor usage and enhance bioactivity. Finally, we describe a case study for stem cell factor.

Leader cell PLCγ1 activation during keratinocyte collective migration is induced by EGFR localization and clustering

Re-epithelialization is a critical step in wound healing and results from the collective migration of keratinocytes. Previous work demonstrated that immobilized, but not soluble, epidermal growth factor (EGF) resulted in leader cell-specific activation of phospholipase C gamma 1 (PLCγ1) in HaCaT keratinocytes, and that this PLCγ1 activation was necessary to drive persistent cell migration. To determine the mechanism responsible for wound edge-localized PLCγ1 activation, we examined differences in cell area, cell-cell interactions, and EGF receptor (EGFR) localization between wound edge and bulk cells treated with vehicle, soluble EGF, or immobilized EGF. Our results support a multistep mechanism where EGFR translocation from the lateral membrane to the basolateral/basal membrane allows clustering in response to immobilized EGF. This analysis of factors regulating PLCγ1 activation is a crucial step toward developing therapies or wound dressings capable of modulating this signal and, consequently, cell migration.

Phospholipase Cγ1 is required for normal irritant contact dermatitis responses and sebaceous gland homeostasis

Differentiation and proliferation of keratinocyte are controlled by various signalling pathways. The epidermal growth factor receptor (EGFR) is known to be an important regulator of multiple epidermal functions. Inhibition of EGFR signalling disturbs keratinocyte proliferation, differentiation and migration. Previous studies have revealed that one of the EGFR downstream signalling molecules, phospholipase Cγ1 (PLCγ1), regulates differentiation, proliferation and migration of keratinocytes in in vitro cell culture system. However, the role of PLCγ1 in the regulation of keratinocyte functions in animal epidermis remains unexplored. In this study, we generated keratinocyte-specific PLCγ1 knockout (KO) mice (PLCγ1 cKO mice). Contrary to our expectations, loss of PLCγ1 did not affect differentiation, proliferation and migration of interfollicular keratinocytes. We further examined the role of PLCγ1 in irritant contact dermatitis (ICD), in which epidermal cells play a pivotal role. Upon irritant stimulation, PLCγ1 cKO mice showed exaggerated ICD responses. Further study revealed that epidermal loss of PLCγ1 induced sebaceous gland hyperplasia, indicating that PLCγ1 regulates homeostasis of one of the epidermal appendages. Taken together, our results indicate that, although PLCγ1 is dispensable in interfollicular keratinocyte for normal differentiation, proliferation and migration, it is required for normal ICD responses. Our results also indicate that PLCγ1 regulates homeostasis of sebaceous glands.

Engineering Approaches to Study Cellular Decision Making

In their native environment, cells are immersed in a complex milieu of biochemical and biophysical cues. These cues may include growth factors, the extracellular matrix, cell-cell contacts, stiffness, and topography, and they are responsible for regulating cellular behaviors such as adhesion, proliferation, migration, apoptosis, and differentiation. The decision-making process used to convert these extracellular inputs into actions is highly complex and sensitive to changes both in the type of individual cue (e.g., growth factor dose/level, timing) and in how these individual cues are combined (e.g., homotypic/heterotypic combinations). In this review, we highlight recent advances in the development of engineering-based approaches to study the cellular decision-making process. Specifically, we discuss the use of biomaterial platforms that enable controlled and tailored delivery of individual and combined cues, as well as the application of computational modeling to analyses of the complex cellular decision-making networks.