Eylem Seç
Regulation of transforming growth factor-beta family members in wound repair
Başlık:
Regulation of transforming growth factor-beta family members in wound repair
Yazar:
Martin, Gail E. M., author.
ISBN:
9780355978148
Yazar Ek Girişi:
Fiziksel Tanımlama:
1 electronic resource (276 pages)
Genel Not:
Source: Dissertation Abstracts International, Volume: 76-08C.
Özet:
Transforming Growth Factor-beta (TGF-beta) isoforms are multifunctional cytokines that manage the response to tissue injury. TGF-beta is chemotactic for inflammatory cells, regulates angiogenesis, re-epithelialisation, and extracellular matrix production and turnover, and its pro-fibrotic effects promote scar formation. TGF-beta is secreted as a biologically inactive, latent complex, and release of the active molecule from its latent precursor is a key step in regulating TGF-beta activity. A number of mechanisms of latent TGF-beta activation have been identified- in cell culture models in vitro. However, the mechanisms by which this occurs in wound repair and scarring, are poorly understood. Therapeutic intervention to manipulate TGF-beta family member activation at the wound site represents a strategy to improve the quality of wound repair and reduce scar formation and fibrosis. During wound repair, two large peaks of TGF-beta activation occur; immediately following wounding and 5 days later, at the time of wound closure. It is our hypothesis that the first peak is associated with degranulation of activated platelets, during blood coagulation and formation of the fibrin clot, to re-establish haemostasis. The second peak .may be associated with epidermal-dermal cell interaction in the re-epithelialised wound. Based on this hypothesis, I used cell models to examine latent TGF-beta activation in vitro. Using the plasminogen activator inhibitor-1/luciferase (PAUL) bioassay for active and latent TGF-beta, I have shown that thrombin-stimulated platelets released and activated latent TGF-beta1 in a time-dependent manner. The time course of activation was delayed compared to platelet degranulation, indicating that TGF-beta release and activation are independent events. The mechanism of activation did not appear to be classical latent TGF-beta activation by proteases or thrombospondin-1, but involved a furin-like proprotein convertase. Part of the activated TGF-beta1 is then bound to a molecule in the platelet releasate, in a cation (probably Mg2+)-dependent fashion, forming a biologically inactive complex. Multiphoton confocal microscopy and analysis of platelet lysates revealed that resting and activated platelets contained some TGF-beta1 in the active form, suggesting intracellular activation, or, alternatively, uptake following release and activation. It is well established that co-culture of certain cell types, e.g. endothelial and smooth muscle cells, facilitates latent TGF-beta activation. I therefore examined the activation of latent TGF-beta in vitro using co-cultures of primary human dermal fibroblasts and primary human dermal keratinocytes or the keratinocyte cell line, HaCaT and A431 epidermoid carcinoma cells, as model systems for TGF-beta regulation in wound repair. All the co-cultures activated latent TGF-beta and activation depended on the ratio of cell types in the co-culture, with a ratio of 1:1 being optimal. While in the majority of experiments no significant amounts of TGF-beta-like activity were generated in the homotypic cultures, UV-A irradiation appeared to induce low level induction of TGF-P-like activity in fibroblast cultures. Isoform analysis revealed that 68-88% of the TGF-beta-like activity in the co-cultures was due to activin, a TGF-beta superfamily member. Activin has not been measured previously in the PAUL bioassay. The residual activity appears to be due to a mixture of TGF-beta1, -beta2 and -beta3. Increased levels of TGF-beta-like activity could be measured by plating the TGF-P responsive cells used for the bioassay together with the co-cultures (triple cultures). Potential requirement for heterotypic cell-to-cell contact for latent TGF-beta activation was achieved by establishing co-cultures with and without well inserts. Cell-to-cell contact was not essential for latent TGF-beta activation in co-cultures using primary keratinocytes, although it was required to achieve maximal activation. By contrast, co-cultures using HaCaT keratinocytes and fibroblasts showed an absolute requirement for direct cell-to-cell contact in order to generate TGF-beta-like activity. While activin may be secreted from the cells in an active form, the generation of the residual TGF-P activity in above co-cultures required protein interaction with the integrin betavbeta6. Thus, I have (at least partially) characterised the time course, TGF-beta isoforms, and mechanisms that most likely are involved in the two major peaks of TGF-beta activation occurring in dermal wound repair. Once the mechanisms of latent TGF-beta activation are fully elucidated in these models, it might be possible to select new therapeutic targets and strategies to influence the speed and quality of wound repair and scarring.
Notlar:
School code: 1543
Tüzel Kişi Ek Girişi:
Mevcut:*
Yer Numarası | Demirbaş Numarası | Shelf Location | Lokasyon / Statüsü / İade Tarihi |
---|---|---|---|
XX(683850.1) | 683850-1001 | Proquest E-Tez Koleksiyonu | Arıyor... |
On Order
Liste seç
Bunu varsayılan liste yap.
Öğeler başarıyla eklendi
Öğeler eklenirken hata oldu. Lütfen tekrar deneyiniz.
:
Select An Item
Data usage warning: You will receive one text message for each title you selected.
Standard text messaging rates apply.