https://www.cell.com/cell/pdf/S0092-8674(01)00622-5.pdf

The Novel Zinc Finger-Containing Transcription Factor Osterix Is Required for Osteoblast Differentiation and Bone Formation

We report a strategy to create photodegradable poly(ethylene glycol)-based hydrogels through rapid polymerization of cytocompatible macromers for remote manipulation of gel properties in situ. Postgelation control of the gel properties was demonstrated to introduce temporal changes, creation of arbitrarily shaped features, and on-demand pendant functionality release. Channels photodegraded within a hydrogel containing encapsulated cells allow cell migration. Temporal variation of the biochemical gel composition was used to influence chondrogenic differentiation of encapsulated stem cells. Photodegradable gels that allow real-time manipulation of material properties or chemistry provide dynamic environments with the scope to answer fundamental questions about material regulation of live cell function and may affect an array of applications from design of drug delivery vehicles to tissue engineering systems.

/pdf/photodegradable-hydrogels-for-dynamic-tuning-of-physical-and-wui78edso7.pdf

Photodegradable Hydrogels for Dynamic Tuning of Physical and Chemical Properties

Chondrogenesis is the earliest phase of skeletal development, involving mesenchymal cell recruitment and migration, condensation of progenitors, and chondrocyte differentiation, and maturation and resulting in the formation of cartilage and bone during endochondral ossification. This process is controlled exquisitely by cellular interactions with the surrounding matrix, growth and differentiation factors, and other environmental factors that initiate or suppress cellular signaling pathways and transcription of specific genes in a temporal-spatial manner. Vertebrate limb development is controlled by interacting patterning systems involving prominently the fibroblast growth factor (FGF), bone morphogenetic protein (BMP), and hedgehog pathways. Both positive and negative signaling kinases and transcription factors, such as Sox9 and Runx2, and interactions among them determine whether the differentiated chondrocytes remain within cartilage elements in articular joints or undergo hypertrophic maturation prior to ossification. The latter process requires extracellular matrix remodeling and vascularization controlled by mechanisms that are not understood completely. Recent work has revealed novel roles for mediators such as GADD45beta, transcription factors of the Dlx, bHLH, leucine zipper, and AP-1 families, and the Wnt/beta-catenin pathway that interact at different stages during chondrogenesis.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/jcb.20652

The control of chondrogenesis.

There is considerable interest in the biology and therapeutic potential of adult stem cells from bone marrow stroma, variously referred to as mesenchymal stem cells or marrow stromal cells (MSCs). Human MSCs can expand rapidly in culture, but the rate of expansion and the yields of multipotential progenitors are inversely related to the plating density and incubation time of each passage. We have defined conditions for optimizing the yields of cultures enriched for early progenitors. Also, we developed a simple method for assessing the quality of the cultures by phase-contrast microscopy and image analysis or by forward light scatter in a flow cytometer. The cells expanded most rapidly on day 4 after plating, with a minimum average doubling time of about 10 hours for cells initially plated at 10 or 50 cells/cm(2). After plating the cells at 1 to 1000 cells/cm(2), the cultures underwent a time-dependent transition from early progenitors, defined as thin, spindle-shaped cells (RS-1A), to wider, spindle-shaped cells (RS-1B), and to still wider, spindle-shaped cells (RS-1C). Assays for adipogenesis demonstrated that the adipogenic potential of cultures was directly related to their ability to generate single-cell-derived colonies and their enrichment for RS-1A cells. In contrast, cultures enriched for RS-1B cells showed the greatest potential to differentiate into cartilage in a serum-free system. The results indicate that, when preparing cultures of human MSCs, it is necessary to compromise between conditions that provide the highest overall yields and those that provide the highest content of early progenitor cells.

https://stemcellsjournals.onlinelibrary.wiley.com/doi/pdf/10.1634/stemcells.20-6-530

Expansion of human adult stem cells from bone marrow stroma: conditions that maximize the yields of early progenitors and evaluate their quality

A three-dimensional nanofibrous scaffold for cartilage tissue engineering using human mesenchymal stem cells.

https://www.oarsijournal.com/article/S1063-4584(99)90306-0/pdf

A.M. DeLise

Papers

Cellular interactions and signaling in cartilage development.