Abstract
Incorporation of 1,25(OH)2 vitamin D3 (vitD3) into tissue-engineered scaffolds could aid the healing of critical-sized bone defects. We hypothesize that shorter applications of vitD3 lead to more osteogenic differentiation of mesenchymal stem cells (MSCs) than a sustained application. To test this, release from a scaffold was mimicked by exposing MSCs to exactly controlled vitD3 regimens. Human adipose stem cells (hASCs) were seeded onto calcium phosphate particles, cultured for 20 days, and treated with 124 ng vitD3, either provided during 30 min before seeding ([200 nM]), during the first two days ([100 nM]), or during 20 days ([10 nM]). Alternatively, hASCs were treated for two days with 6.2 ng vitD3 ([10 nM]). hASCs attached to the calcium phosphate particles and were viable (~75%). Cell number was not affected by the various vitD3 applications. VitD3 (124 ng) applied over 20 days increased cellular alkaline phosphatase activity at Days 7 and 20, reduced expression of the early osteogenic marker RUNX2 at Day 20, and strongly upregulated expression of the vitD3 inactivating enzyme CYP24. VitD3 (124 ng) also reduced RUNX2 and increased CYP24 applied at [100 nM] for two days, but not at [200 nM] for 30 min. These results show that 20-day application of vitD3 has more effect on hASCs than the same total amount applied in a shorter time span.
Highlights
Bone defects can occur as a consequence of birth defects, injury, cancer, or inflammation
2.1. Human adipose stem cells (hASCs) Attached to BCP Particles and Survived, in the Presence and Absence of Vitamin D3 2.1. hASCs Attached to BCP Particles and Survived, in the Presence and Absence of Vitamin D3
We evaluated which vitamin D3 (vitD3) application (Short, Burst, or Sustained) to hASCs seeded on BCP particles, leads to optimal osteogenic differentiation of hASCs in cell culture
Summary
Bone defects can occur as a consequence of birth defects, injury, cancer, or inflammation. The “golden standard” for critical size bone defects is the use of autologous bone grafts [1]. Autologous bone is generally still considered the “gold standard” since it provides both an osteogenic and osteoconductive environment, due to the presence of live cells and the cocktail of growth factors present in the matrix [2]. This method suffers from two major drawbacks: donor site morbidity and lack of available tissue [3]. These drawbacks could be overcome by alternative approaches for bone reconstruction, such as methods employing principles of bone tissue engineering
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