The success of tissue engineering applications can potentially be dramatically improved with the addition of adjuncts that increase the proliferation and differentiation of progenitor or stem cells. Platelet-rich plasma (PRP) has recently emerged as a potential biologic tool to treat acute and chronic tendon disorders. The regenerative potential of PRP is based on the release of growth factors that occurs with platelet rupture. Its autologous nature gives it a significant advantage in tissue engineering applications. To test whether PRP may be useful specifically for cartilage regeneration, a cell culture experiment was devised in which mesenchymal stem cells (MSCs) were grown in control media or media enhanced with inactivated, buffered PRP. Proliferation 7 days after PRP treatment was increased: 1.041 versus 0.199 for the control media cells ( p < 0.001). The messenger RNA (mRNA) level of the osteogenic marker RUNX2 was 52.84 versus 26.88 for the control group ( p < 0.005). Likewise the mRNA level of the chondrogenic markers Sox-9 and aggrecan was 29.74 versus 2.29 for the control group ( p < 0.001) and 21.04 versus 1.93 ( p < 0.001), respectively. These results confirm that PRP enhances MSC proliferation and suggest that PRP causes chondrogenic differentiation of MSC in vitro.

State-space models (SSMs) are an important modeling framework for analyzing ecological time series. These hierarchical models are commonly used to model population dynamics, animal movement, and capture-recapture data, and are now increasingly being used to model other ecological processes. SSMs are popular because they are flexible and they model the natural variation in ecological processes separately from observation error. Their flexibility allows 1 This article has been accepted for publication and undergone full peer review but has not been through the copyediting, typesetting, pagination and proofreading process, which may lead to differences between this version and the Version of Record. Please cite this article as

Abstract. More diverse crop rotations have been promoted for their potential to remediate the range of ecosystem services compromised by biologically simplified grain-based agroecosystems, including increasing soil organic carbon (SOC). We hypothesized that functional diversity offers a more predictive means of characterizing the impact of crop rotations on SOC concentrations than species diversity per se. Furthermore, we hypothesized that functional diversity can either increase or decrease SOC depending on its associated carbon (C) input to soil. We compiled a database of 27 cropping system sites and 169 cropping systems, recorded the species and functional diversity of crop rotations, SOC concentrations (g C kg/soil), nitrogen (N) fertilizer applications (kg NÁha ). We categorized crop rotations into three broad categories: grain-only rotations, grain rotations with cover crops, and grain rotations with perennial crops. We divided the grain-only rotations into two sub-categories: cereal-only rotations and those that included both cereals and a legume grain. We compared changes in SOC and C input using mean effect sizes and 95% bootstrapped confidence intervals. Cover cropped and perennial cropped rotations, relative to grain-only rotations, increased C input by 42% and 23% and SOC concentrations by 6.3% and 12.5%, respectively. Within grain-only rotations, cereal + legume grain rotations decreased total C input (À16%), root C input (À12%), and SOC (À5.3%) relative to cereal-only rotations. We found no effect of species diversity on SOC within grain-only rotations. N fertilizer rates mediated the effect of functional diversity on SOC within grain-only crop rotations: at low N fertilizer rates (≤75 kg NÁha ), the decrease in SOC with cereal + legume grain rotations was less than at high N fertilizer rates. Our results show that increasing the functional diversity of crop rotations is more likely to increase SOC concentrations if it is accompanied by an increase in C input. Functionally diverse perennial and cover cropped rotations increased both C input and SOC concentrations, potentially by exploiting niches in time that would otherwise be unproductive, that is, increasing the "perenniality" of crop rotations.

Relationships between soil fractions (their mass or carbon (C)) and soil organic carbon (SOC) have been used to develop central ideas in SOC research. However, few attempts have been made to quantify the relationship between SOC and all soil fractions, despite the potential of such an effort to address SOC stabilization processes. We identified 41 published studies that used diverse management techniques to cause a change in SOC concentration and disrupted soil into macroaggregates (> 250 µm), free microaggregates (53-250 µm) and free silt + clay (< 53 µm), subsequently disrupting macroaggregates into constituent fractions (coarse particulate organic matter [cPOM] > 250 µm, occluded microaggregates, and occluded silt + clay). We used linear hierarchical models to quantify relationships between mass, C concentration and total C of fractions and SOC. Soil mass redistribution toward macroaggregates was associated with SOC accumulation, however total microaggregate mass (free + occluded) did not increase with macroaggregate mass, as would be expected given de novo microaggregate formation within macroaggregates. Instead, high SOC soils exhibited a greater percent of total microaggregates occluded in macroaggregates. Occlusion in macroaggregates was also associated with increased C concentrations of microaggregates (35% higher, SE = 3.2) and silt + clay (30% higher, SE = 3.9) relative to their free counterparts. Taken together, these relationships suggest reduced macroaggregate turnover promotes SOC accumulation via the stabilization of C into occluded fractions. Rates of SOC increase with silt + clay C concentrations failed to increase with mean site-level SOC concentration, indicating of the studied soils (median SOC concentration = 14 g kg -1 ; max 68), SOC accumulation appears unlikely to be limited by C storage capacity in the silt + clay fraction. For each unit SOC gain, macroaggregates accounted for 83% (95% CI = 74, 91),