Identification of a novel FcγRIII receptor that is up-regulated in fetal wound healing

Skin tissue engineering: wound healing based on stem-cell-based therapeutic strategies

Normal wound healing is a dynamic and complex multiple phase process involving coordinated interactions between growth factors, cytokines, chemokines, and various cells. Any failure in these phases may lead wounds to become chronic and have abnormal scar formation. Chronic wounds affect patients' quality of life, since they require repetitive treatments and incur considerable medical costs. Thus, much effort has been focused on developing novel therapeutic approaches for wound treatment. Stem-cell-based therapeutic strategies have been proposed to treat these wounds. They have shown considerable potential for improving the rate and quality of wound healing and regenerating the skin. However, there are many challenges for using stem cells in skin regeneration. In this review, we present some sets of the data published on using embryonic stem cells, induced pluripotent stem cells, and adult stem cells in healing wounds. Additionally, we will discuss the different angles whereby these cells can contribute to their unique features and show the current drawbacks.

Scarless integumentary wound healing in the mammalian fetus: molecular basis and therapeutic implications

Adult mammals respond to injury of their skin/integument by forming scar tissue. Scar is useful in rapidly sealing an injured area, but can also lead to significant morbidity. Mammals in fetal life retain the ability to heal integumentary wounds regeneratively, without scar. The critical molecular mechanisms governing this remarkable phenomenon have been a subject of great interest, in the hopes that these could be dissected and recapitulated in the healing adult wound, with the goal of inducing scarless healing in injured patients. Multiple lines of investigation spanning decades have implicated a number of factors in distinguishing scarless from fibrotic wound healing, including most prominently transforming growth factor-β and interleukin-10, among others. Therapeutic interventions to try to mitigate scarring in adult wounds have been developed out of these studies, and have reached the level of clinical trials in humans, although as yet no FDA-approved treatment exists. More recent expressomic studies have revealed many more genes that are differentially expressed in scarlessly healing fetal wounds compared with adult, and microRNAs have also been identified as participating in the fetal wound healing response. These represent an even greater range of potential therapeutics (or targets for therapy) to translate the promise of scarless fetal wound healing to the injured adult patient.

Evidence for gene recombination in FCGR3 gene variants

BACKGROUND AND OBJECTIVES

The genes encoding the Fcgamma receptors (FcgammaR) IIIa and IIIb (FCGR3A and FCGR3B) are clustered on chromosome 1 band q23-24 and exhibit allelic polymorphism. We investigated the molecular basis of additional new FCGR3 genomic variation.

MATERIALS AND METHODS

A segment shared by FCGR3A and FCGR3B containing the polymorphic nucleotide positions 141, 147, 227, 266, and 277 in exon 3 was cloned and sequenced from genomic DNA of 30 donors and 3 bacterial artificial chromosome (BAC) clones. A mixture consisting of isolated FCGR3B*2- and FCGR3A- plasmids was cloned and sequenced as well. Additionally, nucleotide databases were screened for clones with variant FCGR3 sequences.

RESULTS

A total of 12 FCGR3 variants defined by the polymorphic positions were detected in whole blood genomic DNA from 23 of 24 FCGR3B*2 and/or FCGR3B*3 positive donors, the DNA from two of three BAC clones and in the DNA mixture of isolated FCGR3B*2- and FCGR3A- plasmids.

CONCLUSION

Nucleotide exchanges of the variants were non-random and resulted from two alternative nucleotides present in one of the polymorphic position of the basic FCGR3 forms. Polymerase chain reaction (PCR) artefacts cannot be excluded as origin of new variants, but there is strong evidence that at least two variants are the result of a somatic recombination.

Receptor-mediated endocytosis of immune complexes in rat liver sinusoidal endothelial cells is mediated by FcgammaRIIb2

Liver sinusoidal endothelial cells (LSECs) display a number of receptors for efficient uptake of potentially injurious molecules. The receptors for the Fc portion of immunoglobulin G (IgG) antibodies (FcgammaRs) regulate a number of physiological and pathophysiological events. We used reverse transcription polymerase chain reaction (RT-PCR) and Western blotting to determine the expression of different types of FcgammaRs in LSECs. Biochemical approaches and immunofluorescence microscopy were used to characterize the FcgammaR-mediated endocytosis of immune complexes (ICs). FcgammaRIIb2 was identified as the main receptor for the efficient uptake of ICs in LSECs. The receptor was shown to use the clathrin pathway for IC uptake; however, the association with lipid rafts may slow the rate of its internalization. Moreover, despite trafficking through lysosomal integral membrane protein-II (LIMP-II)-containing compartments, the receptor was not degraded. Finally, it was shown that the receptor recycles to the cell surface both with and without IC.

CONCLUSION

FcgammaRIIb2 is the main receptor for endocytosis of ICs in rat LSECs. Internalized ICs are degraded with slow kinetics, and IC internalization is not linked to receptor downregulation. After internalization, the receptor recycles to the cell surface both with and without ICs. Thus, FcgammaRIIb2 in rat LSECs is used as both a recycling receptor and a receptor for efficient IC clearance.