Understanding the role of growth factors in modulating stem cell tenogenesis

Current treatments for tendon injuries often fail to fully restore joint biomechanics leading to the recurrence of symptoms, and thus resulting in a significant health problem with a relevant social impact worldwide. Cell-based approaches involving the use of stem cells might enable tailoring a successful tendon regeneration outcome. As growth factors (GFs) powerfully regulate the cell biological response, their exogenous addition can further stimulate stem cells into the tenogenic lineage, which might eventually depend on stem cells source. In the present study we investigate the tenogenic differentiation potential of human- amniotic fluid stem cells (hAFSCs) and adipose-derived stem cells (hASCs) with several GFs associated to tendon development and healing; namely, EGF, bFGF, PDGF-BB and TGF-β1. Stem cells response to biochemical stimuli was studied by screening of tendon-related genes (collagen type I, III, decorin, tenascin C and scleraxis) and proteins found in tendon extracellular matrix (ECM) (Collagen I, III, and Tenascin C). Despite the fact that GFs did not seem to influence the synthesis of tendon ECM proteins, EGF and bFGF influenced the expression of tendon-related genes in hAFSCs, while EGF and PDGF-BB stimulated the genetic expression in hASCs. Overall results on cellular alignment morphology, immunolocalization and PCR analysis indicated that both stem cell source can be biochemically induced towards tenogenic commitment, validating the potential of hASCs and hAFSCs for tendon regeneration strategies.Authors thank the Portuguese Foundation for Science and Technology (FCT) for the research project BIBS (PTDC/CVT/102972/2008) and for the post-doc fellowship grant: SFRH/BPD/86775/2012. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript

Elastogenic Protein Expression of a Highly Elastic Murine Spinal Ligament: The Ligamentum Flavum

Spinal ligaments, such as the ligamentum flavum (LF), are prone to degeneration and iatrogenic injury that can lead to back pain and nerve dysfunction. Repair and regeneration strategies for these tissues are lacking, perhaps due to limited understanding of spinal ligament formation, the elaboration of its elastic fibers, maturation and homeostasis. Using immunohistochemistry and histology, we investigated murine LF elastogenesis and tissue formation from embryonic to mature postnatal stages. We characterized the spatiotemporal distribution of the key elastogenic proteins tropoelastin, fibrillin-1, fibulin-4 and lysyl oxidase. We found that elastogenesis begins in utero with the microfibril constituent fibrillin-1 staining intensely just before birth. Elastic fibers were first detected histologically at postnatal day (P) 7, the earliest stage at which tropoelastin and fibulin-4 stained intensely. From P7 to P28, elastic fibers grew in diameter and became straighter along the axis. The growth of elastic fibers coincided with intense staining of tropoelastin and fibulin-4 staining, possibly supporting a chaperone role for fibulin-4. These expression patterns correlated with reported skeletal and behavioral changes during murine development. This immunohistochemical characterization of elastogenesis of the LF will be useful for future studies investigating mechanisms for elastogenesis and developing new strategies for treatment or regeneration of spinal ligaments and other highly elastic tissues

Transforming growth factor beta signaling: The master sculptor of fingers

Transforming growth factor beta (TGF?) constitutes a large and evolutionarily conserved superfamily of secreted factors that play essential roles in embryonic development, cancer, tissue regeneration, and human degenerative pathology. Studies of this signaling cascade in the regulation of cellular and tissue changes in the three-dimensional context of a developing embryo have notably advanced in the understanding of the action mechanism of these growth factors. In this review, we address the role of TGF? signaling in the developing limb, focusing on its essential function in the morphogenesis of the autopod. As we discuss in this work, modern mouse genetic experiments together with more classical embryological approaches in chick embryos, provided very valuable information concerning the role of TGF? and Activin family members in the morphogenesis of the digits of tetrapods, including the formation of phalanxes, digital tendons, and interphalangeal joints. We emphasize the importance of the Activin and TGF? proteins as digit inducing factors and their critical interaction with the BMP signaling to sculpt the hand and foot morphology