Intermittent parathyroid hormone (1-34) supplementation of bone marrow stromal cell cultures may inhibit hypertrophy, but at the expense of chondrogenesis.

Background: Bone marrow stromal cells (BMSC) have promise in cartilage tissue engineering, but for their potential to be fully realised, the propensity to undergo hypertrophy must be mitigated. The literature contains diverging reports on the effect of parathyroid hormone (PTH) on BMSC differentiation. Cartilage tissue models can be heterogeneous, confounding efforts to improve media formulations.

Methods: Herein, we use a novel microwell platform (the Microwell-mesh) to manufacture hundreds of small-diameter homogeneous micro-pellets and use this high-resolution assay to quantify the influence of constant or intermittent PTH(1-34) medium supplementation on BMSC chondrogenesis and hypertrophy. Micro-pellets were manufactured from 5000 BMSC each and cultured in standard chondrogenic media supplemented with (1) no PTH, (2) intermittent PTH, or (3) constant PTH.

Results: Relative to control chondrogenic cultures, BMSC micro-pellets exposed to intermittent PTH had reduced hypertrophic gene expression following 1 week of culture, but this was accompanied by a loss in chondrogenesis by the second week of culture. Constant PTH treatment was detrimental to chondrogenic culture.

Conclusions: This study provides further clarity on the role of PTH on chondrogenic differentiation in vitro and suggests that while PTH may mitigate BMSC hypertrophy, it does so at the expense of chondrogenesis.