Growth Factors and Their Receptors in the Anterior Chamber

Abstract

The involvement of growth factors such as epidermal growth factor (EGF) in regenerative processes of corneal endothelium and lens epithelium has recently been suggested. However, knowledge on the presence of growth factors in anterior chamber fluid (ACF) is still very restricted. Although we have previously shown that EGF is undetectable in the ACF of normal eyes undergoing cataract surgery even by the use of high-sensitivity assays, this does not exclude the possible presence of other, EGF-like proteins in ACF such as transforming growth factor α (TGF-α). In the present study, we have hence determined in ACF samples of 70 human eyes the concentrations of both EGF and TGF-α. As assays served ELISA techniques and RIA. In none of all the samples investigated could detectable amounts of EGF, i.e. above 0.2 pg/ml (detection limit of the assay), be found, confirming earlier results. Interestingly, however, also no TGF-α could be detected in ACF. If present at all, the level of any TGF-α concentration in ACF was hence below the detection limit, i.e. less than 20 pg/ml. Based on the results of this study, it seems therefore that under physiological conditions there is no measurable presence of free EGF or TGF-α in human ACF. Existing receptors in the structures of the anterior segment must hence have ample binding capacity which could explain the effect of externally applied growth factors. The physiological and clinical importance of this result is briefly outlined.

Regional Differences in Tyrosine Kinase Receptor Signaling Components Determine Differential Growth Patterns in the Human Lens

“…6 Traces of EGF have been found in the human lens 7,8 and in the aqueous humor of patients undergoing intraocular surgery, 9 although not all investigators have detected the ligand. 10 The presence of EGFR mRNA and protein have been reported in human lens epithelial cells (HLECs) 8,11 and the developing chick lens (Ireland M, et al IOVS 2002;43:ARVO E-Abstract 2347), but the pattern of its distribution over the entire epithelium has not been elucidated.…”

ErbBs in Lens Cell Fibrosis and Secondary Cataract

“…The resulting paracrine and/or autocrine signaling could be especially important to epithelial cells in the avascular lens, given the reported lack of ErbB ligands in the aqueous humor. 58 – 61 ErbB1 and/or ErbB4 have been reported to bind to more than 10 distinct polypeptide growth factors. 26 , 37 Instead of pursuing the many individual ErbB ligand candidates, we developed an assay to detect overall ErbB-stimulating activity in DCDML-conditioned medium.…”

The M100: Face categorization begins within 100 ms of stimulus presentation

“…However, HCECs are arrested at the G 1 phase of the cell cycle in vivo [6-8]. Factors involved in this cell-cycle arrest include the relative lack of positive mitogenic stimulation in vivo [9,10], potential negative regulation by transforming growth factor-beta2 (TGF-beta2) in the aqueous humor [11-13], maintenance of the monolayer in a contact-inhibited state [14], and an age-dependent negative regulation [15-17]. Therefore, promoting HCECs from the G 1 phase into the S phase is the most critical step in enhancing HCEC proliferation.…”