Growth Factor-based Therapies Research Articles

Differentiation of adipose-derived stem cells to chondrocytes using electrospraying

An important challenge in the fabrication of tissue engineered constructs for regenerative medical applications is the development of processes capable of delivering cells and biomaterials to specific locations in a consistent manner. Electrospraying live cells has been introduced in recent years as a cell seeding method, but its effect on phenotype nor genotype has not been explored. A promising candidate for the cellular component of these constructs are human adipose-derived stem cells (hASCs), which are multipotent stem cells that can be differentiated into fat, bone, and cartilage cells. They can be easily and safely obtained from adipose tissue, regardless of the age and sex of the donor. Moreover, these cells can be maintained and expanded in culture for long periods of time without losing their differentiation capacity. In this study, hASCs directly incorporated into a polymer solution were electrosprayed, inducing differentiation into chondrocytes, without the addition of any exogenous factors. Multiple studies have demonstrated the effects of exposing hASCs to biomolecules—such as soluble growth factors, chemokines, and morphogens—to induce chondrogenesis. Transforming growth factors (e.g., TGF-β) and bone morphogenetic proteins are particularly known to play essential roles in the induction of chondrogenesis. Although growth factors have great therapeutic potential for cell-based cartilage regeneration, these growth factor-based therapies have presented several clinical complications, including high dose requirements, low half-life, protein instability, higher costs, and adverse effects in vivo. The present data suggests that electrospraying has great potential as hASCs-based therapy for cartilage regeneration.

Toward Developing Immunocompetent Diabetic Foot Ulcer-on-a-Chip Models for Drug Testing.

Bioengineering of skin has been significantly explored, ranging from the use of traditional cell culture systems to the most recent organ-on-a-chip (OoC) technology that permits skin modeling on physiological scales among other benefits. This article presents key considerations for developing physiologically relevant immunocompetent diabetic foot ulcer (DFU) models. Diabetic foot ulceration affects hundreds of millions of individuals globally, especially the elderly, and constitutes a major socioeconomic burden. When DFUs are not treated and managed in a timely manner, 15-50% of patients tend to undergo partial or complete amputation of the affected limb. Consequently, at least 40% of such patients die within 5 years postamputation. Currently, therapeutic strategies are actively sought and developed. However, present-day preclinical platforms (animals and in vitro models) are not robust enough to provide reliable data for clinical trials. Insights from published works on immunocompetent skin-on-a-chip models and bioengineering considerations, presented in this article, can inform researchers on how to develop robust OoC models for testing topical therapies such as growth factor-based therapies for DFUs. We propose that immunocompetent DFU-on-a-chip models should be bioengineered using diseased cells derived from individuals; in particular, the pathophysiological contribution of macrophages in diabetic wound healing, along with the typical fibroblasts and keratinocytes, needs to be recapitulated. The ideal model should consist of the following components: diseased cells embedded in reproducible scaffolds, which permit endogenous "diseased" extracellular matrix deposition, and the integration of the derived immunocompetent DFU model onto a microfluidic platform. The proposed DFU platforms will eventually facilitate reliable and robust drug testing of wound healing therapeutics, coupled with reduced clinical trial failure rates. Impact statement Current animal and cell-based systems are not physiologically relevant enough to retrieve reliable results for clinical translation of diabetic foot ulcer (DFU) therapies. Organ-on-a-chip (OoC) technology offers desirable features that could finally enable the vision of modeling DFU for pathophysiological studies and drug testing at a microscale. This article brings together the significant recent findings relevant to developing a minimally functional immunocompetent DFU-on-a-chip model, as wound healing cannot occur without a proper functioning immune response. It looks feasible in the future to recapitulate the stagnant inflammation in DFU (thought to impede wound healing) using OoC, diseased cells, and an endogenously produced extracellular matrix.

Basic and Therapeutic Aspects of Angiogenesis Updated.

All organisms growing beyond the oxygen diffusion limit critically depend on a functional vasculature for survival. Yet blood vessels are far more than passive, uniform conduits for oxygen and nutrient supply. A remarkable organotypic heterogeneity is brought about by tissue-specific differentiated endothelial cells (lining the blood vessels' lumen) and allows blood vessels to deal with organ-specific demands for homeostasis. On the flip side, when blood vessels go awry, they promote life-threatening diseases characterized by endothelial cells inappropriately adopting an angiogenic state (eg, tumor vascularization) or becoming dysfunctional (eg, diabetic microvasculopathies), calling respectively for antiangiogenic therapies and proangiogenic/vascular regenerative strategies. In solid tumors, despite initial enthusiasm, growth factor-based (mostly anti-VEGF [vascular endothelial growth factor]) antiangiogenic therapies do not sufficiently live up to the expectations in terms of efficiency and patient survival, in part, due to intrinsic and acquired therapy resistance. Tumors cunningly deploy alternative growth factors than the ones targeted by the antiangiogenic therapies to reinstigate angiogenesis or revert to other ways of securing blood flow, independently of the targeted growth factors. In trying to alleviate tissue ischemia and to repair dysfunctional or damaged endothelium, local in-tissue administration of (genes encoding) proangiogenic factors or endothelial (stem) cells harnessing regenerative potential have been explored. Notwithstanding evaluation in clinical trials, these approaches are often hampered by dosing issues and limited half-life or local retention of the administered agents. Here, without intending to provide an all-encompassing historical overview, we focus on some recent advances in understanding endothelial cell behavior in health and disease and identify novel molecular players and concepts that could eventually be considered for therapeutic targeting.

Combined Administration of ASCs and BMP-12 Promotes an M2 Macrophage Phenotype and Enhances Tendon Healing.

Outcomes after intrasynovial tendon repair are highly variable. An intense inflammatory cascade followed by a delayed healing response can cause adhesion formation and repair-site failure that severely impair the function of repaired digits. No effective remedies exist to fully address these issues. Cell- and growth factor-based therapies have been shown to modulate inflammation and improve cell proliferation and matrix synthesis and therefore are promising treatment approaches for intrasynovial tendon repair. (1) Can autologous adipose-derived mesenchymal stromal cells (ASCs) and recombinant bone morphogenetic protein-12 (rBMP-12) be effectively delivered to an intrasynovial flexor tendon repair without adverse effects? (2) Do autologous ASCs modulate the inflammatory response after intrasynovial tendon injury and repair? (3) Does the combined application of autologous ASCs and rBMP-12 modulate the proliferative and remodeling responses after intrasynovial tendon injury and repair? Sixteen 1- to 2-year-old female canines were used in this study. Autologous ASC sheets, with and without rBMP-12, were applied to the surface of sutured flexor tendons. Fourteen days after repair, the effects of treatment were determined using quantitative PCR (six per group) for the expression of genes related to macrophage phenotype or inflammation (IL-4, CD163, VEGF, NOS2, IL-1B, and IFNG), cell proliferation (CCND1), and tendon formation (SCX, TNMD, COL1A1 and COL3A1). Proteomics analysis (four per group) was performed to examine changes in tendon protein abundances. CD146 immunostaining and hematoxylin and eosin staining (four per group) were used to detect tendon stem or progenitor cells and to semiquantitatively evaluate cellularity at the tendon repair; analyses were done blinded to group. Gross inspection and cell tracing showed that autologous ASCs and rBMP-12 were delivered to the flexor tendon repair site without the deleterious effects of adhesion and repair-site gap formation. Quantitative assessment of gene and protein expression showed effects of treatment: ASC-sheet treatment modulated the postrepair inflammatory response and facilitated healing by increasing regenerative M2 macrophages (M2 marker CD204, twofold of normal, p = 0.030), inflammatory inhibitor (prostaglandin reductase 1 [PTRG1], 1.6-fold of normal, p = 0.026), and proteins involved in tendon formation (periostin [POSTN], 1.9-fold of normal, p = 0.035). Consistently, semiquantitative and qualitative evaluations of repaired tissue showed that ASC-sheet treatment reduced mononuclear cell infiltration (12% less than nontreated tendons, p = 0.021) and introduced CD146+ stem or progenitor cells to the repair site. The combined administration of ASCs and rBMP-12 further stimulated M2 macrophages by increasing IL-4 (116-fold of normal, p = 0.002) and led to the increase of M2 effector matrix metalloproteinase-12 involved in matrix remodeling (twofold of normal, p = 0.016) and reduction of a negative regulator of angiogenesis and cell migration (StAR-related lipid transfer domain protein13 [STARD13]; 84% of normal, p = 0.000), thus facilitating the proliferative stage of tendon repair. ASCs and BMP-12 accelerated the progression of healing in the proliferative stage of tendon repair. The effects of ASCs and BMP-12 on tendon functional recovery should be evaluated in future studies. The cell sheet approach is an effective, biocompatible, and surgeon-friendly approach for cell and growth factor delivery during tendon repair. Combined application of ASCs and BMP-12 may accelerate intrasynovial tendon healing while suppressing the adverse inflammatory response.

A computational model for investigating the effects of changes in bioavailability of insulin-like growth factor-1 on the homeostasis of the intervertebral disc

Insulin-like growth factor-1 (IGF-1) is well-known for upregulating cell proliferation and biosynthesis of the extracellular matrix in the intervertebral disc (IVD). Pathological conditions, such as obesity or chronic kidney disease cause IGF-1 deficiency in plasma. How this deficiency impacts disc homeostasis remains unknown. Pro-anabolic approaches for the treatment of disc degeneration based on enhancing IGF-1 bioavailability to tissue-cells are considered, but knowledge of their effectiveness in enhancing cellular anabolism of a degenerated disc is limited.In this study, we developed a computational model for disc homeostasis specifically addressing the role of IGF-1 in modulating both extracellular matrix biosynthesis and cellularity in the IVD. This model was applied to investigate how changes in IGF-1 bioavailability, namely deficiency or enhancement of growth factor, affect disc health.In this study, it was found that IGF-1 deficiency mainly affects the biosynthesis of ECM components, especially in the most external regions of the IVD such as the cartilage endplates and the outer portion of annulus fibrosus. Also, a total of three approaches for increasing IGF-1 bioavailability as a therapy for degenerated IVDs were investigated. It was found that all these strategies are only beneficial to those disc regions receiving sufficient nutritional supply (i.e., the outmost IVD regions), while they exacerbate tissue degradation in malnourished regions (i.e., inner portion of the disc). This suggests that pro-anabolic growth factor-based therapies are limited in that their success strongly depends on an adequate nutritional supply to the IVD tissue, which is not guaranteed in degenerated discs.

Hierarchy of cellular decisions in collective behavior: Implications for wound healing.

Collective processes such as wound re-epithelialization result from the integration of individual cellular decisions. To determine which individual cell behaviors represent the most promising targets to engineer re-epithelialization, we examined collective and individual responses of HaCaT keratinocytes seeded upon polyacrylamide gels of three stiffnesses (1, 30, and 100 kPa) and treated with a range of epidermal growth factor (EGF) doses. Wound closure was found to increase with substrate stiffness, but was responsive to EGF treatment only above a stiffness threshold. Individual cell behaviors were used to create a partial least squares regression model to predict the hierarchy of factors driving wound closure. Unexpectedly, cell area and persistence were found to have the strongest correlation to the observed differences in wound closure. Meanwhile, the model predicted a relatively weak correlation between wound closure with proliferation, and the unexpectedly minor input from proliferation was successfully tested with inhibition by aphidicolin. Combined, these results suggest that the poor clinical results for growth factor-based therapies for chronic wounds may result from a disconnect between the individual cellular behaviors targeted in these approaches and the resulting collective response. Additionally, the stiffness-dependency of EGF sensitivity suggests that therapies matched to microenvironmental characteristics will be more efficacious.

Combination Growth Factor Therapy via Electrostatically Assembled Wound Dressings Improves Diabetic Ulcer Healing In Vivo.

Chronic skin ulcerations are a common complication of diabetes mellitus, affecting up to one in four diabetic individuals. Despite the prevalence of these wounds, current pharmacologic options for treating them remain limited. Growth factor-based therapies have displayed a mixed ability to drive successful healing, which may be due to nonoptimal delivery strategies. Here, a method for coating commercially available nylon dressings using the layer-by-layer process is described to enable both sustained release and independent control over the release kinetics of vascular endothelial growth factor 165 and platelet-derived growth factor BB. It is shown that the use of strategically spaced diffusion barriers formed spontaneously by disulfide bonds enables independent control over the release rates of incorporated growth factors, and that in vivo these dressings improve several aspects of wound healing in db/db mice.

Advanced Strategies for Articular Cartilage Defect Repair.

Articular cartilage is a unique tissue owing to its ability to withstand repetitive compressive stress throughout an individual’s lifetime. However, its major limitation is the inability to heal even the most minor injuries. There still remains an inherent lack of strategies that stimulate hyaline-like articular cartilage growth with appropriate functional properties. Recent scientific advances in tissue engineering have made significant steps towards development of constructs for articular cartilage repair. In particular, research has shown the potential of biomaterial physico-chemical properties significantly influencing the proliferation, differentiation and matrix deposition by progenitor cells. Accordingly, this highlights the potential of using such properties to direct the lineage towards which such cells follow. Moreover, the use of soluble growth factors to enhance the bioactivity and regenerative capacity of biomaterials has recently been adopted by researchers in the field of tissue engineering. In addition, gene therapy is a growing area that has found noteworthy use in tissue engineering partly due to the potential to overcome some drawbacks associated with current growth factor delivery systems. In this context, such advanced strategies in biomaterial science, cell-based and growth factor-based therapies that have been employed in the restoration and repair of damaged articular cartilage will be the focus of this review article.

Mononuclear phagocyte system in kidney disease and repair

The mononuclear phagocyte system is comprised of circulating monocytes, tissue macrophages and dendritic cells (DCs) that play key roles in tissue homeostasis, immune surveillance, and immune and non-immune-mediated tissue injury and repair. This review summarizes the various subsets within this system that exhibit significant functional and phenotypic diversity that can adapt to their surrounding microenvironments during inflammation and in response to colony-stimulating factor (CSF)-1. The current understanding of the co-ordination of monocyte infiltration into the homeostatic and diseased kidney through adhesion molecules, chemokines and chemokine receptors, and cytokines are described. Furthermore, the significant confusion and controversy associated with monocyte differentiation into renal macrophages and DCs following infiltration into the kidney, the considerable functional and phenotypic overlap between both tissue populations and their respective roles in immune and non-immune-mediated renal is also discussed. Understanding the factors that control the activation and recruitment of cells from the mononuclear phagocyte system during renal injury may offer an avenue for the development of new cellular and growth factor-based therapies in combination with existing therapies as an alternative treatment option for patients with renal disease.

Cardiac Progenitor Cells as Target of Cell and Growth Factor-Based Therapies for Myocardial Regeneration

It has been recently established that the adult heart harbors a reservoir of myocardial stem/progenitor cells. The regenerative potential of the heart is, however, insufficient to fully restore the functional myocardium after damage, motivating the use of cell- and growth factor-based replacement strategies. In this review, we summarize the progress that has been made in this field and discuss its actual contribution to the stimulation of endogenous mechanisms of myocardial repair/regeneration. Particular emphasis has been paid to paracrine secretion occurring in host tissues as the major mechanism involved in the beneficial outcomes of cell transplantation into the injured myocardium. The advantages of using cell therapy over single and combined growth factor administration have been also extensively discussed.

Growth Factor–Extracellular Matrix Interactions Regulate Wound Repair

Wound healing is a process made up of several phases, including hemostasis/inflammation, proliferation, and scar formation/remodeling. An array of growth factors is produced during each of these phases that helps direct the repair process. Most of the information we have about the biological actions of growth factors are from studies examining a growth factor in isolation. However, growth factors are known to interact with the extracellular matrix (ECM), and these associations influence cell behavior. Details about these interactions within the complex and continuously changing wound environment are not well understood and are likely to be very important during repair. Several types of growth factor/ECM interactions have been described that could impact wound healing. The ECM can interact directly with growth factors, offering protection from degradation and controlling bioactivity of the growth factor. Portions of the ECM can bind to growth factor receptors, and cell-ECM binding can influence growth factor receptor signaling. Growth factors can also control production and degradation of the ECM; therefore, the relationship between growth factors and ECM is bidirectional. New information about the relationship between growth factors and ECM could be used to optimize growth factor-based therapies or lead to the development of novel treatment strategies for wound care. Growth factor-ECM interactions likely have a strong impact on the rate and quality of healing. A better understanding of the relationship between these classes of molecules and how it can be exploited to enhance healing is needed.

Epidermal growth factor receptor inhibits colitis-associated cancer in mice

Inflammatory bowel disease (IBD) is a chronic illness caused by complex interactions between genetic and environmental factors that propagate inflammation and damage to the gastrointestinal epithelium. This state of chronic inflammation increases the risk for development of colitis-associated cancer in IBD patients. Thus, the development of targeted therapeutics that can disrupt the cycle of inflammation and epithelial injury is highly attractive. However, such biological therapies, including those targeting epidermal growth factor receptor pathways, pose a risk of increasing cancer rates. Using two mouse models of colitis-associated cancer, we found that epidermal growth factor receptor inactivation accelerated the incidence and progression of colorectal tumors. By modulating inflammation and epithelial regeneration, epidermal growth factor receptor optimized the response to chronic inflammation and limited subsequent tumorigenesis. These findings provide important insights into the pathogenesis of colitis-associated cancer and suggest that epidermal growth factor-based therapies for IBD may reduce long-term cancer risk.

Stem cell- and growth factor-based regenerative therapies for avascular necrosis of the femoral head

Avascular necrosis (AVN) of the femoral head is a debilitating disease of multifactorial genesis, predominately affects young patients, and often leads to the development of secondary osteoarthritis. The evolving field of regenerative medicine offers promising treatment strategies using cells, biomaterial scaffolds, and bioactive factors, which might improve clinical outcome. Early stages of AVN with preserved structural integrity of the subchondral plate are accessible to retrograde surgical procedures, such as core decompression to reduce the intraosseous pressure and to induce bone remodeling. The additive application of concentrated bone marrow aspirates, ex vivo expanded mesenchymal stem cells, and osteogenic or angiogenic growth factors (or both) holds great potential to improve bone regeneration. In contrast, advanced stages of AVN with collapsed subchondral bone require an osteochondral reconstruction to preserve the physiological joint function. Analogously to strategies for osteochondral reconstruction in the knee, anterograde surgical techniques, such as osteochondral transplantation (mosaicplasty), matrix-based autologous chondrocyte implantation, or the use of acellular scaffolds alone, might preserve joint function and reduce the need for hip replacement. This review summarizes recent experimental accomplishments and initial clinical findings in the field of regenerative medicine which apply cells, growth factors, and matrices to address the clinical problem of AVN.

Platelet-Rich Plasma

Several injectable substances have been studied for the treatment of tendinitis of the hand, wrist, and elbow, including corticosteroids, botulinum toxin, autologous blood, and platelet-rich plasma (PRP). 1 Faro F. Wolf J.M. Lateral epicondylitis: review and current concepts. J Hand Surg. 2007; 32A: 1271-1279 Google Scholar , 2 Mishra A. Pavelko T. Treatment of chronic elbow tendinosis with buffered platelet-rich plasma. Am J Sports Med. 2006; 34: 1774-1778 Crossref PubMed Scopus (628) Google Scholar , 3 Peerbooms J.C. Sluimer J. Bruijn D.J. Gosens T. Positive effect of an autologous platelet concentrate in lateral epicondylitis in a double-blind randomized controlled trial: platelet-rich plasma versus corticosteroid injection with a 1-year follow-up. Am J Sports Med. 2010; 38: 255-262 Crossref PubMed Scopus (523) Google Scholar , 4 Szabo R.M. Steroid injection for lateral epicondylitis. J Hand Surg. 2009; 34A: 326-330 Google Scholar , 5 Creaney L. Wallace A. Curtis M. Connell D. Growth factor-based therapies provide additional benefit beyond physical therapy in resistant elbow tendinopathy: a prospective, single-blind, randomised trial of autologous blood injections versus platelet-rich plasma injections. Br J Sports Med. 2011; 45: 966-971 Crossref PubMed Scopus (212) Google Scholar , 6 Thanasas C. Papadimitriou G. Charalambidis C. Paraskevopoulos I. Papanikolaou A. Platelet-rich plasma versus autologous whole blood for the treatment of chronic lateral elbow epicondylitis: a randomized controlled clinical trial. Am J Sports Med. 2011; 39: 2130-2134 Crossref PubMed Scopus (262) Google Scholar , 7 Wolf J.M. Ozer K. Scott F. Gordon M.J. Williams A.E. Comparison of autologous blood, corticosteroid, and saline injection in the treatment of lateral epicondylitis: a prospective, randomized, controlled multicenter study. J Hand Surg. 2011; 36A: 1269-1272 Google Scholar , 8 Gosens T. Peerbooms J.C. van Laar W. den Oudsten B.L. Ongoing positive effect of platelet-rich plasma versus corticosteroid injection in lateral epicondylitis: a double-blind randomized controlled trial with 2-year follow-up. Am J Sports Med. 2011; 39: 1200-1208 Crossref PubMed Scopus (387) Google Scholar Whereas empiric data suggest a beneficial effect of many treatments for tendinitis, defined roles for these various injections remain unclear. For several years, orthopedic surgeons have used PRP to treat conditions such as tendinitis about the knee, hip, and shoulder 9 Hall M.P. Band P.A. Meislin R.J. Jazrawi L.M. Cardone D.A. Platelet-rich plasma: current concepts and application in sports medicine. J Am Acad Orthop Surg. 2009; 17: 602-608 Crossref PubMed Scopus (273) Google Scholar , 10 Sampson S. Gerhardt M. Mandelbaum B. Platelet rich plasma injection grafts for musculoskeletal injuries: a review. Curr Rev Musculoskelet Med. 2008; 1: 165-174 Crossref PubMed Scopus (4) Google Scholar , 11 Mishra A. Harmon K. Woodall J. Vieira A. Sports medicine applications of platelet rich plasma. Curr Pharm Biotechnol. 2011 July 8; (Epub ahead of print) Google Scholar ; however, data are inconclusive as to its precise mechanism of action as well as whether it demonstrates lasting benefit. We review the composition and preparation of PRP and list several of the available kits for its preparation. Journal CME QuestionsJournal of Hand SurgeryVol. 37Issue 3Preview Full-Text PDF

Growth factor-based therapies provide additional benefit beyond physical therapy in resistant elbow tendinopathy: a prospective, single-blind, randomised trial of autologous blood injections versus platelet-rich plasma injections

BackgroundGrowth factor technologies are increasingly used to enhance healing in musculoskeletal injuries, particularly in sports medicine. Two such products; platelet-rich plasma (PRP) and autologous blood, have a growing body of...

Recent advances in dermal wound healing: biomedical device approaches

Successful repair of wounds and tissues remains a major healthcare and biomedical challenge in the 21st Century. In particular, chronic wounds often lead to loss of functional ability, increased pain and decreased quality of life, and can be a burden on carers and health-system resources. Advanced healing therapies employing biological dressings, skin substitutes, growth factor-based therapies and synthetic acellular matrices, all of which aim to correct irregular and dysfunctional cellular pathways present in chronic wounds, are becoming more popular. This review focuses on recent advances in biologically inspired devices for wound healing and includes a commentary on the challenges facing the regulatory governance of such products.

Stem cells: comprehensive treatments for amyotrophic lateral sclerosis in conjunction with growth factor delivery

Amyotrophic lateral sclerosis (ALS) is characterized by loss of both upper and lower motor neurons. ALS progression is complex and likely due to cellular dysfunction at multiple levels, including mitochondrial dysfunction, glutamate excitotoxicity, oxidative stress, axonal dysfunction, reactive astrocytosis, and mutant superoxide dismutase expression, therefore, treatment must provide neuronal protection from multiple insults. A significant amount of ALS research focuses on growth factor-based therapies. Growth factors including insulin-like growth factor-I, vascular endothelial growth factor, brain-derived neurotrophic factor, and glial-derived neurotrophic factor exhibit robust neuroprotective effects on motor neurons in ALS models. Issues concerning growth factor delivery, stability and unwanted side effects slow the transfer of these treatments to human ALS patients. Stem cells represent a new therapeutic approach offering both cellular replacement and trophic support for the existing population. Combination therapy consisting of stem cells expressing beneficial growth factors may provide a comprehensive treatment for ALS.

Skeletal Muscle Development and Regeneration

In the late stages of muscle development, a unique cell population emerges that is a key player in postnatal muscle growth and muscle regeneration. The location of these cells next to the muscle fibers triggers their designation as satellite cells. During the healing of injured muscle tissue, satellite cells are capable of forming completely new muscle fibers or restoring damaged muscle fibers. A major problem in muscle healing is the formation of dysfunctional scar tissue, which leads to incomplete functional recovery. Therefore, the identification of factors that improve the process of muscle healing and reduce the formation of scar tissue is of great interest. Because satellite cells possess the capability of self-renewal, a unique feature of stem cells, they play a central role in the search for therapies to improve muscle healing. Growth factor-based and (satellite) cell-based therapies are being investigated to treat minor muscle injuries and intrinsic muscle defects. Major muscle injury that involves the loss of muscle tissue requires the use of scaffolds with or without (satellite) cells. Scaffolds are also being developed to generate muscle tissue in vitro. These approaches aim to restore the structure and function of the injured muscle without dysfunctional scarring.

Sustained release and osteogenic potential of heparan sulfate-doped fibrin glue scaffolds within a rat cranial model

This paper explores the potential therapeutic role of the naturally occurring sugar heparan sulfate (HS) for the augmentation of bone repair. Scaffolds comprising fibrin glue loaded with 5 microg of embryonically derived HS were assessed, firstly as a release-reservoir, and secondly as a scaffold to stimulate bone regeneration in a critical size rat cranial defect. We show HS-loaded scaffolds have a uniform distribution of HS, which was readily released with a typical burst phase, quickly followed by a prolonged delivery lasting several days. Importantly, the released HS contributed to improved wound healing over a 3-month period as determined by microcomputed tomography (microCT) scanning, histology, histomorphometry, and PCR for osteogenic markers. In all cases, only minimal healing was observed after 1 and 3 months in the absence of HS. In contrast, marked healing was observed by 3 months following HS treatment, with nearly full closure of the defect site. PCR analysis showed significant increases in the gene expression of the osteogenic markers Runx2, alkaline phosphatase, and osteopontin in the heparin sulfate group compared with controls. These results further emphasize the important role HS plays in augmenting wound healing, and its successful delivery in a hydrogel provides a novel alternative to autologous bone graft and growth factor-based therapies.

Nerve Verve

Rookie athletes sometimes fall short of fans' expectations; likewise, nerve growth factors haven't fulfilled their promise of preventing neurodegeneration. But the molecules might have broken out of their slump. An extra dose of one such protein slows neurodegeneration and extends life in mice with Lou Gehrig's disease, according to a new study. The research rekindles hope for nerve growth factor-based therapies. Patients with amyotrophic lateral sclerosis (ALS; also called Lou Gehrig's disease, after the baseball star debilitated by it) lose motor neurons, suffer from tremors and paralysis, and eventually die from the affliction. ALS and its neurodegenerative cousins Parkinson's, Alzheimer's, and Huntington's diseases all raze nerves but act in different areas of the brain and spinal cord. Determining the reason that ALS-afflicted neurons die might lead to treatments for the disorder and reveal general principles of neurodegeneration. For almost 2 decades, researchers have been examining whether proteins that stimulate nerve growth could slow neurodegeneration. The handful of attempts to alleviate human ALS by injecting the proteins failed, however. "Most biotech and pharmaceutical companies have given up on nerve growth factors [to treat ALS]," says neuroscientist Jeffrey Deitch of Drexel University in Philadelphia, Pennsylvania. But Sun and colleagues never surrendered. Several years ago, the researchers discovered that hepatocyte growth factor (HGF), a protein that nurtures liver cells, also fosters neuron growth in culture. They wondered if this protein might waylay the neuronal damage associated with ALS. The team tested this idea on mice that mimic the disorder. These animals carry a mutation commonly found in ALS patients, which alters superoxide dismutase (SOD1), an enzyme that protects cells from oxidative stress (see "The Two Faces of Oxygen" ). The researchers engineered the mutant mice to produce extra HGF in neurons. At 8 months of age, the rodents retained twice as many motor neurons as did ALS mice without auxiliary HGF. The difference translated into better living: The supplemented animals had 15% more time before paralysis hit and lived 12% longer. To understand how HGF protected the mice, the researchers looked for physiological differences between treated and untreated animals. Extra HGF didn't prevent SOD1 aggregates in the spinal cord, a pathology that appears early in ALS. But the protein lowered the concentrations of a cell suicide-inducing enzyme that neurons manufacture midway through ALS progression; it also quashed production of an enzyme that manufactures destructive oxygen-containing molecules. Furthermore, HGF treatment elevated the amount of a protein that sucks neurotransmitters into cells, which usually drops late in the disease. According to co-author Hiroshi Funakoshi, a molecular neurobiologist at Osaka University in Japan, the results suggest that HGF intervenes after the early stage of ALS. The study hints that nerve growth factors might hold therapeutic potential after all, says Deitch. The previous tests on ALS patients might have failed because the proteins didn't reach the motor neurons, he adds. Resolving that problem, perhaps by using an engineered virus that delivers proteins directly to target cells, might put nerve growth factors back in the lineup against neurodegenerative disease. --Mary Beckman; suggested by Joy Goto W. Sun, H. Funakoshi, and T. Nakamura, Overexpression of HGF retards disease progression and prolongs life span in a transgenic mouse model of ALS. J. Neurosci. 22 , 6537-6548 (2002). [Abstract] [Full text]