Chronic liver damage leads to the onset of fibrogenesis. Rodent models for liver fibrosis have been widely used, but are less suitable for screening purposes. Therefore the aim of our study was to design a novel model for liver fibrosis in zebrafish embryos, suitable for high throughput screening. Furthermore, we evaluated the efficacy of mesenchymal stromal cells (MSCs) to inhibit the fibrotic process and thereby the applicability of this model to evaluate therapeutic responses. Zebrafish embryos were exposed to TAA or CCL4 and mRNA levels of fibrosis-related genes (Collagen-1α1, Hand-2, and Acta-2) and tissue damage-related genes (TGF-β and SDF-1a, SDF-1b) were determined, while Sirius-red staining was used to estimate collagen deposition. Three days after start of TAA exposure, MSCs were injected after which the fibrotic response was determined. In contrast to CCL4, TAA resulted in an upregulation of the fibrosis-related genes, increased extracellular matrix deposition and decreased liver sizes suggesting the onset of fibrosis. The applicability of this model to evaluate therapeutic responses was shown by local treatment with MSCs which resulted in decreased expression of the fibrosis-related RNA markers. In conclusion, TAA induces liver fibrosis in zebrafish embryos, thereby providing a promising model for future mechanistic and therapeutic studies.

Evidence to define target ranges for tacrolimus (Tac) and mycophenolic acid (MPA) exposure after the first year of kidney transplantation is limited. We investigated the association of measurements at 1 year and repeated measurements of real‐world Tac‐trough levels (C₀) and abbreviated area under the curve from zero to 12 hours (AUC_0‐12h) of Tac and MPA with biopsy‐proven acute rejection (BPAR) between years 1 and 3 post‐transplant in 968 kidney transplant recipients (KTRs). Thirty‐five (3.6%) out of 968 KTRs experienced BPAR. Both Tac‐AUC_0‐12h (hazard ratio (HR): 0.39, 95% confidence interval (CI): 0.30–0.50, P < 0.001), Tac‐C₀ (HR: 0.46, 95% CI: 0.38–0.57, P < 0.001) and MPA‐AUC_0‐12h at 1 year (HR: 0.80, 95% CI: 0.68–0.94, P = 0.006), as well as repeated measurements of Tac‐C₀ (HR: 0.70, 95% credibility interval (CrI): 0.61–0.82, P < 0.001), and of MPA‐AUC_0‐12h (HR: 0.75, 95% CrI: 0.62–0.93, P < 0.001) were associated with BPAR. In our population, the recommended target range for Tac‐AUC_0‐12h at 1 year would be 75–95 ng*hour/mL and a Tac‐C₀ 5–7 ng/mL. The Tac‐AUC_0‐12h predicted BPAR better than Tac‐C₀ and identified KTRs with over‐ or underexposure despite supposedly adequate Tac‐C₀. We did not find evidence to recommend another target than the consensus range of 30–60 mg*hour/L for MPA‐AUC_0‐12h after the first year of transplantation. To our knowledge, this is a first study on the simultaneous exposure of Tac and MPA at year 1 and subsequent BPAR up to year 3, which may help define the therapeutic target window for the longer term.

Chronic liver injury leads to the accumulation of myofibroblasts resulting in increased collagen deposition and hepatic fibrogenesis. Treatments specifically targeting fibrogenesis are not yet available. Mesenchymal stromal cells (MSCs) are fibroblast‐like stromal (stem) cells, which stimulate tissue regeneration and modulate immune responses. In the present study we assessed whether liver fibrosis and cirrhosis can be reversed by treatment with MSCs or fibroblasts concomitant to partial hepatectomy (pHx)‐induced liver regeneration. After carbon tetrachloride‐induced fibrosis and cirrhosis, mice underwent a pHx and received either systemically or locally MSCs in one of the two remaining fibrotic/cirrhotic liver lobes. Eight days after treatment, liver fibrogenesis was evaluated by Sirius‐red staining for collagen deposition. A significant reduction of collagen content in the locally treated lobes of the regenerated fibrotic and cirrhotic livers was observed in mice that received high dose MSCs. In the non‐MSC‐treated counterpart liver lobes no changes in collagen deposition were observed. Local fibroblast administration or intravenous administration of MSCs did not ameliorate fibrosis. To conclude, local administration of MSCs after pHx, in contrast to fibroblasts, results in a dose‐dependent on‐site reduction of collagen deposition in mouse models for liver fibrosis and cirrhosis.

In recent years, mesenchymal stromal cells [MSCs] emerged as a promising therapeutic option for various diseases, due to their immunomodulatory properties. We previously observed that intraperitoneally injected MSCs in experimental colitis form spherical shaped aggregates. Therefore, we aggregated MSCs in vitro into spheroids and injected them intraluminally in mice with established colitis, to investigate whether these MSC spheroids could alleviate the colitis. We injected 0.5 x 10 ⁶ MSCs in spheroids, 2.0 x 10 ⁶ MSCs in spheroids, or phosphate-buffered saline [PBS] as a treatment control, via an enema in mice with established dextran sulphate sodium [DSS]-induced colitis. Body weight was measured daily and disease activity score was determined at sacrifice. Endoscopy was performed to evaluate mucosal healing. After sacrifice, both systemic and local inflammatory responses were evaluated. Intraluminally injected MSC spheroids alleviated DSS-induced colitis, resulting in significantly less body weight loss and lower disease activity score at sacrifice when a high dose of MSC spheroids was administered. However, the percentage of mucosal lesions in the distal colon and endoscopy scores were not significantly lower after treatment with 2.0 x 10 ⁶ MSCs in spheroids compared with PBS-treated mice. Systemic inflammation marker serum amyloid A [SAA] was significantly reduced after treatment with 2.0 x 10 ⁶ MSCs in spheroids. In addition, local cytokine levels of IFN-ɣ, TNF-α, IL-6, and IL-17a, as well as numbers of macrophages and neutrophils, showed a clear decrease—though not always significant—after intraluminal injection of the MSC spheroids. Intraluminally injected MSC spheroids at least partially attenuate experimental colitis, with fewer phagocytes and proinflammmatory cytokines, when a high dose of MSCs in spheroids was administered.