Thermally labile components of aqueous humor potently induce osteogenic potential in adipose-derived mesenchymal stem cells

Abstract

Adipose-derived mesenchymal stem cells (ASCs) hold promise for use in cell-based therapies. Their intrinsic anti-inflammatory properties are potentially useful for treatments of inflammatory conditions such as uveitis, while their ability to differentiate along multiple cell lineages suggests use in regenerating damaged or degenerated tissue. However, how ASCs will respond to the intraocular environment is poorly studied. We have recently reported that aqueous humor (AH), the fluid that nourishes the anterior segment of the eye, potently increases alkaline phosphatase (ALP) activity of ASCs, indicating osteogenic differentiation. Here, we expand on our previous findings to better define the nature of this response. To this end, we cultured ASCs in the presence of 0, 5, 10, and 20% AH and assayed them for ALP activity. We found ALP activity correlates with increasing AH concentrations from 5 to 20%, and that longer treatments result in increased ALP activity. By using serum free media and pretreating AH with dextran-coated charcoal, we found that serum and charcoal-adsorbable AH components augment but are not required for this response. Further, by heat-treating the AH, we established that thermally labile components are required for the osteogenic response. Finally, we showed myocilin, a protein present in AH, could induce ALP activity in ASCs. However, this was to a lesser extent than untreated 5% AH, and myocilin could only partially rescue the effect after heat treatment, documenting there were additional thermally labile constituents of AH involved in the osteogenic response. Our work adds to the understanding of the induction of ALP in ASCs following exposure to AH, providing important insight in how ASCs will be influenced by the ocular environment. In conclusion, increased osteogenic potential upon exposure to AH represents a potential challenge to developing ASC cell-based therapies directed at the eye.

Adipose Stem Cells in Modern-Day Ophthalmology

“…Further studies are required to understand the potential effects of aqueous humor and in vivo myocilin proteins to induce the osteogenesis of ADSCs. This could be of utmost importance to prevent the possible calcification of anterior chamber structures post-intracameral injection [130]. Further research is also needed to establish the exact mechanisms of optic neuroprotection and other postulated mechanisms of facial nerve regeneration via MSCs [131].…”

Cell Therapy Applications for Retinal Vascular Diseases: Diabetic Retinopathy and Retinal Vein Occlusion

“…This transformation of MSCs may be triggered by exposure to factors in the eye, such as aqueous humor. 38 In addition, some host factors, such as diabetes, might affect the efficacy of MSCs. Bone marrow-derived MSCs from diabetic mouse was noted with reduced migration and adhesion.…”