Roles of Mechanosensitive Channel Piezo1 in Wound Healing and Scar Formation.

The ability to heal one's wounds is perhaps one of the most fundamental and critical of physiologic processes. This coordinated and closely regulated sequential biological process involves a variety of migratory and resident cells. The activation, modulation, balance, and control of these functions depend upon soluble mediators that activate cells and modulate their diverse functions. Recent advances have identified mechanotransduction as functionally integral in many different cell types and physiologic processes. The mechanically sensitive ion channel Pieoz1 is expressed on platelets, neutrophils, macrophages, endothelial cells, keratinocytes, and fibroblasts, all of which are principally involved in wound healing. On a cellular level, there have been great advances in our understanding of the functional role of Piezo1 mechanotransduction in cutaneous wounding. The blocking of Piezo1 has recently been shown to reduce scarring in vivo and yet, thus far, a comprehensive understanding of the roles that Piezo1 plays in in vivo wound healing remains lacking. Recognizing the ever-present and critical importance of optimal and reparative wound healing, and with the availability of new physical mechanomodulating devices, the time is ripe for gaining deeper insights into optimizing wound healing. In this review, we describe the current knowledge of Piezo1 related to wound healing.

The periodontal ligament, temperature-sensitive ion channels TRPV1-4, and the mechanosensitive ion channels Piezo1 and 2: A Nobel connection.

Teeth are subject to a variety of mechanical forces and vectors. The periodontal ligament (PDL), fibrous tissue that connects the cementum of the tooth to the bony socket, plays a decisive role in transmitting force to alveolar bone via Sharpey fibers, transforming and converting these forces into biological signals. This interaction effects significant osteoblastic and osteoclastic responses via autocrine proliferative and paracrine responses. Recent discoveries of receptors for temperature and touch by the Nobel laureates David Julius and Ardem Patapoutian, respectively have a profound impact on orthodontics. Transient receptor vanilloid channel 1 (TRPV1), initially described as a receptor for temperature, has been proposed to participate in the sensing of force. TRPV4, another ion channel receptor, perceives tensile forces as well as thermal and chemical stimuli. Piezo1 and 2, the classic receptors for touch, in addition to the aforementioned receptors, have similarly been described on PDL-derived cells. In this text, we review the role of the temperature-sensitive ion channels and mechanosensitive ion channels on their biological function and influence in orthodontic treatment.

Minimal Scar Formation After Orthopaedic Skin Incisions Along Main Folding Lines.

BACKGROUND: Patients, particularly those who are young, often develop noticeable orthopaedic scars. In order to achieve minimal scarring, surgeons should attempt to place incisions in skinfolds or skin creases. METHODS: Optimal incision lines can be determined from the direction of stretch marks (striae distensae), which develop perpendicular to lines of tension or main folding lines. A composite diagram of photographs of 213 individuals with striae distensae was created and compared with 276 images of incisions and scars derived from the Internet. RESULTS: Classically described Langer cleavage lines often run counter to real tension lines and poorly predict the optimal direction for skin incisions. CONCLUSIONS: Whenever possible, main folding lines should be utilized as a guide in planning surgical incisions for young patients as well as for correction of problem scars.

Injection of SVF combined with HBO2 improves viability of unfavorably designed flaps.

PURPOSE: Soft-tissue reconstruction is complicated by ischemia and reperfusion injury. Animal trials have documented the independent healing benefits of hyperbaric oxygen preconditioning (HBOP) and stem cell delivery in cutaneous flaps. We explored the role of HBOP and stem cell delivery in flap preconditioning and survival. METHODS: We designed a randomized controlled trial to assess the effects of hyperbaric oxygen preconditioning and stromal vascular fraction (SVF) delivery on flap survival. Of the first 24 guinea pigs, six received neither HBOP nor injections, and six underwent HBOP without injections. Of the remaining 12 animals, six received SVF or saline injections in the absence of HBOP. The final six animals received autologous SVF injections or saline injections followed by four HBOP treatments. To enhance clinical relevance, a group of 6 animals underwent HBOP prior to SVF or saline injections. Thereafter, an unfavorably designed cutaneous flap was elevated and assessed via study-blinded observer, as well as by quantification of TUNEL-positive cells. RESULTS: Distal necrosis of the tissue flap was more extensive in the no-intervention group (45% of flap). Flaps treated with HBOP only and those treated with SVF injections demonstrated only 38.2% and 27.1% distal necrosis. The most significant difference occurred in the combination HBOP and SVF group, where distal necrosis was only 21.1% of the flap (p ≤ 0.05). SVF delivery immediately prior to flap elevation further minimized distal necrosis of the flap to 15.6%. These findings were mirrored by the TUNEL assay. CONCLUSIONS: Combining HBOP and SVF improves flap viability.

Preclinical assessment of safety and efficacy of intravenous delivery of autologous adipose-derived regenerative cells (ADRCs) in the treatment of severe thermal burns using a porcine model.

OBJECTIVE: A number of studies have reported that application of autologous adipose-derived cell populations leads to improved outcome in different preclinical models of thermal burn injury. However, these studies were limited to assessment of relatively small injuries amounting to only ∼2% of total body surface area (TBSA) in which the complications associated with large burns (e.g.: systemic inflammation and the need for fluid resuscitation) are absent. In anticipation of translating this approach to a clinical trial in which these complications would be present we applied a preclinical model that more closely resembles a patient with large thermal burn injury requiring skin grafting. Thus, the present study used a porcine model to investigate safety and efficacy of intravenous delivery of ADRCs in the treatment of a complex burn injury comprising ∼20% TBSA and including both moderately deep (44%) partial and full thickness burns, and the injury associated with skin graft harvest. METHODS: Two pairs of full thickness and partial thickness burns involving in total ∼20% TBSA were created on the back of Yorkshire pigs (n=15). Three days post-burn, full thickness wounds were excised and grafted with a 3:1 meshed autologous split thickness skin graft (STSG). Partial thickness wounds were not treated other than with dressings. Animals were then randomized to receive intravenous delivery of ADRCs (n=8) or vehicle control (n=7). Safety was assessed by monitoring systemic parameters (blood gases, hematology, and clinical chemistry) throughout the course of the study. Wound healing for both types of burn wound and for the skin graft donor sites was followed for 18days using wound imaging, histology, and trans-epidermal water loss (TEWL; skin barrier function assessment). RESULTS: No serious adverse events related to ADRC infusion were noted in any of the animals. Delivery of ADRCs appeared to be safe with none of the systemic safety parameters worsened compared to the control group. TEWL and histological analyses revealed that ADRC treatment was associated with significantly accelerated healing of skin graft (27.1% vs. 1.1% on Day 5 post-grafting), donor site (52.8% vs. 33.1% on Day 5 post-excision) and partial thickness burn (81.8% vs. 59.8% on Day 18 post-treatment). Data also suggested that ADRC treatment improved parameters associated with skin graft elasticity. CONCLUSIONS: This study demonstrated that intravenous delivery of autologous ADRCs appears to be a safe and feasible approach to the treatment of large burns and supports the use of ADRCs as an adjunct therapy to skin grafting in patients with severe burns.

Interleukin-6 Serum Levels Correlate With Severity of Burn Injury but Not With Gender.

Gender-specific differences in the outcome of patients with burn injury have been recognized in the past with female patients being at a higher risk of mortality. We hypothesized that early post-burn interleukin-6 (IL-6) cytokine levels may contribute to the different gender-specific outcome. We retrospectively examined 94 burned patients who were treated in the Burn Intensive Care Unit at the University Hospital Aachen. Age, gender, presence of inhalation injury, depth, TBSA, and clinical outcome were documented. Serum samples for IL-6 analysis were collected within 24 hours posttrauma. The relationship between IL-6 levels, gender, survival, and abbreviated burn severity index score was investigated. Male patients (64.9%; n = 61) presented a higher median TBSA (26%) than female patients (20%). The mortality rate of male patients (27.9%; n = 17) and female patients (21.2%; n = 7) was similar. Deceased patients had significant higher TBSA (P = 0.0005) and IL-6 levels (P = 0.0007) than burn survivors. A moderate correlation between IL-6 levels and abbreviated burn severity index score was observed (r = 0.554; P < 0.0001). While TBSA showed a significant influence on IL-6 levels (P = 0.0003), gender did not (P = 0.7395) and inhalation injury indicated a minor influence (P = 0.0780). Only TBSA and age presented a significant influence on mortality (P = 0.0028 and P = 0.0031, respectively). All patients with burn trauma were characterized by elevated IL-6 levels with higher TBSA values resulting in more pronounced levels. Deceased patients had higher initial IL-6 serum levels reflecting higher TBSA and severity. In contrast to other defined trauma mechanisms, gender had no significant influence on postburn IL-6 serum levels and mortality in our patient population.

Healing Time Correlates With the Quality of Scaring: Results From a Prospective Randomized Control Donor Site Trial.

BACKGROUND: Scar formation remains a potential problem after surgery or trauma. Factors influencing scar tissue have been recognized, most notably healing time and wound depth. OBJECTIVE: To examine the association between healing time and the quality of scar tissue formation. MATERIALS AND METHODS: Scarring was assessed at 3 and 12 months after treatment in an RCT of 219 patients and consecutive 438 split-thickness skin graft donor sites. The primary end point of the study was healing time and the quality of scar tissue, which was scored by a validated scar scale evaluating scar height, surface, and color. RESULTS: The mean time of wound healing was 15.8 days, with a mean scar score of 6.89 at 3 months and 4.66 at 12 months. There was a significant (p < .000001) and linear correlation between healing time and scar quality. Of particular note, at 12 months, all subparameters of the score demonstrated worsening with prolonged time to heal. CONCLUSION: The authors could objectively demonstrate that epithelialization time is an important factor influencing scar quality. In contrast to previous assumptions, this correlation follows linearly. It is reasonable then to assume that treatment strategies expediting healing will also improve scar outcome.

Autologous adipose-derived regenerative cell therapy modulates development of hypertrophic scarring in a red Duroc porcine model.

BACKGROUND: Effective prevention and treatment of hypertrophic scars (HTSs), a common consequence of deep-partial thickness injury, remain a significant clinical challenge. Previous studies from our group have shown that autologous adipose-derived regenerative cells (ADRCs) represent a promising approach to improve wound healing and, thereby, impact HTS development. The purpose of this study was to assess the influence of local delivery of ADRCs immediately following deep-partial thickness cutaneous injury on HTS development in the red Duroc (RD) porcine model. METHODS: Bilateral pairs of deep-partial thickness excisional wounds (2 mm depth; 58 cm2 area) were created using an electric dermatome on RD pigs (n = 12). Autologous ADRCs were isolated from the inguinal fat pad and then sprayed directly onto the wound at a dose of 0.25 × 106 viable cells/cm2. The paired contralateral wound received vehicle control. Wound healing and development of HTS were assessed over 6 months using digital imaging, quantitative measurement of skin hardness and pigmentation, and histology. RESULTS: Data showed that ADRC treatment led to reduced scar hyperpigmentation compared to control (p < 0.05). Using the Durometer, at 2 and 6 months post-injury, skin hardness was 10-20% lower in ADRCs-treated wounds compared to control vehicle (p < 0.05). A similar trend was observed with the skin fibrometer. ADRC treatment promoted more normal collagen organization, improvement in the number of rete ridges (p < 0.01), longer elastic fiber length (p < 0.01), and reduced hypervascularity (blood vessel density; p < 0.05). ADRC treatment was associated with modulation of IL-6 expression within the wound/scar with upregulation 2 weeks after injury (wound healing phase) and downregulation at 2 months (early scarring phase) post-treatment compared to control CONCLUSIONS: These findings support the potential therapeutic value of autologous ADRC administration for reduction of HTS development following deep-partial cutaneous injury.

Staged Repair of an Aortic Pseudoaneurysm Secondary to Delayed Methylmethacrylate Plate Migration.

Methylmethacrylate is a prosthetic material commonly used for the reconstruction of large chest wall defects. We present the first reported case of delayed methylmethacrylate plate migration, which resulted in an aortic pseudoaneurysm with aortopulmonary fistula. Treatment management, including staged repair combining endovascular and open approaches, is also discussed.

The Use of Dehydrated Human Amnion/Chorion Membranes in the Treatment of Burns and Complex Wounds: Current and Future Applications.

Historically, biologic materials found in nature have been used for a wide variety of medicinal purposes, although their widespread use may be limited due to challenges in obtaining and properly preparing the material for safe clinical use. Amniotic membrane has long been recognized to possess unique properties favorable for healing. Dehydrated human amnion/chorion membrane allografts are commercially available for use in multiple sizes and configurations applicable for a variety of clinical settings and presentations. The purpose of this article is to review the therapeutic properties of amniotic membrane.

Development of a combined radiation and full thickness burn injury minipig model to study the effects of uncultured adipose-derived regenerative cell therapy in wound healing.

PURPOSE: To develop an approach that models the cutaneous healing that occurs in a patient with full thickness thermal burn injury complicated by total body radiation exposure sufficient to induce sub-lethal prodromal symptoms. An assessment of the effects of an autologous cell therapy on wound healing on thermal burn injury with concomitant radiation exposure was used to validate the utility of the model. METHODS: Göttingen minipigs were subjected to a 1.2 Gy total body irradiation by exposure to a 6 MV X-ray linear accelerator followed by ∼10 cm2 full thickness burns (pre-heated brass block with calibrated spring). Three days after injury, wounds were excised to the underlying fascia and each animal was randomized to receive treatment with autologous adipose-derived regenerative cells (ADRC) delivered by local or intravenous injection, or vehicle control. Blood counts were used to assess radiation-induced marrow suppression. All animals were followed using digital imaging to assess wound healing. Full-thickness biopsies were obtained at 7, 14, 21 and 30 days' post-treatment. RESULTS: Compared to animals receiving burn injury alone, significant transient neutropenia and thrombocytopenia were observed in irradiated subjects with average neutrophil nadir of 0.79 × 103/µl (day 15) and platelet nadir of 60 × 103/µl (day 12). Wound closure through a combination of contraction and epithelialization from the wound edges occurred over a period of approximately 28 days' post excision and treatment. Re-epithelialization was accelerated in wounds treated with ADRC (mean 3.5-fold increase at 2 weeks post-treatment relative to control). This acceleration was accompanied by an average 67% increase in blood vessel density and 30% increase in matrix (collagen) deposition. Similar results were observed when ADRC were injected either directly into the wound or by intravenous administration. CONCLUSIONS: Although preliminary, this study provides a reproducible minipig model of thermal burn injury complicated by myelosuppressive total body irradiation that utilizes standardized procedures to evaluate novel countermeasures for potential use following attack by an improvised nuclear device.

Current Concepts in Tissue Engineering: Skin and Wound.

BACKGROUND: Pure regenerative healing with little to no donor morbidity remains an elusive goal for both surgeon and patient. The ability to engineer and promote the development of like tissue holds so much promise, and efforts in this direction are slowly but steadily advancing. METHODS: Products selected and reviewed reflect historical precedence and importance and focus on current clinically available products in use. Emerging technologies we anticipate will further expand our therapeutic options are introduced. The topic of tissue engineering is incredibly broad in scope, and as such the authors have focused their review on that of constructs specifically designed for skin and wound healing. A review of pertinent and current clinically related literature is included. RESULTS: Products such as biosynthetics, biologics, cellular promoting factors, and commercially available matrices can be routinely found in most modern health care centers. Although to date no complete regenerative or direct identical soft-tissue replacement exists, currently available commercial components have proven beneficial in augmenting and improving some types of wound healing scenarios. Cost, directed specificity, biocompatibility, and bioburden tolerance are just some of the impending challenges to adoption. CONCLUSIONS: Quality of life and in fact the ability to sustain life is dependent on our most complex and remarkable organ, skin. Although pure regenerative healing and engineered soft-tissue constructs elude us, surgeons and health care providers are slowly gaining comfort and experience with concepts and strategies to improve the healing of wounds.

Adipose-Derived Regenerative Cell Therapy for Burn Wound Healing: A Comparison of Two Delivery Methods.

Objective: The use of noncultured autologous stromal vascular fraction or clinical grade adipose-derived regenerative cells (ADRCs) is a promising strategy to promote wound healing and tissue repair. Nevertheless, issues regarding the optimal mode of administration remain unclear. The purpose of this study was to compare the effects of local injection and topical spray delivery of ADRCs in a porcine model of thermal burns. Approach: Full-thickness thermal burns were created on the dorsum of 10 Gottingen minipigs. Two days following injury, wounds underwent fascial excision and were randomized to receive control vehicle or freshly isolated autologous ADRCs delivered by either multiple injections into or surrounding the wound bed, or by spray onto the wound surface (0.25 × 106 viable cells/cm2). Healing was evaluated by planimetry, histopathology, and immunohistochemistry at day 7, 12, 16, 21, and 28 posttreatment. Results:In vitro analysis demonstrated that there was no substantial loss of cell number or viability attributable to the spray procedure. Planimetric assessment revealed that delivery of ADRCs by either local injection or topical spray increased wound reepithelialization relative to control at day 14. No significant difference in wound reepithelialization was observed between both delivery approaches. In addition, on day 7 posttreatment, blood vessel density was greater in wounds receiving local or topical spray ADRCs than in the wounds treated with vehicle control. Histopathologic analysis suggests that ADRC treatment may modulate the inflammatory response by reducing neutrophil infiltration at day 7 and 12 posttreatment, irrespective of the route of administration. Conclusions: These data demonstrate that local injection and spray delivery of ADRCs modulate inflammation and improve wound angiogenesis and epithelialization. Importantly, both delivery routes exhibited similar effects on wound healing. Given the greater ease-of-use associated with topical spray delivery, these data support the use of a spray system for autologous ADRC delivery.

Description of a Simple Method of Stoma Protection During Prone Positioning.

Surgeries conducted with the patient in the prone position are frequent and can be lengthy. Abdominal stomas and su- prapubic catheters require protection for the complete duration of the procedure to avoid complications such as stomal ischemia, bleeding, or mucocutaneous separation. Standard protection strategies such as pillows and wedges can eas- ily fail. In the course of managing several patients who had sustained ostomy complications following surgery in a prone position, a simple method of stoma protection was devised. Instead of discarding the foam headrest typically used dur- ing induction by anesthesia staff, this device is placed with its central recess over the stoma and secured to the patient's abdominal wall with gentle tape just before turning the patient into a prone position. This method, used in more than 80 patients, has been found to effectively relieve pressure, and no complications have been observed. The foam shape also enables unobstructed drainage of fluids, facilitating collection and preventing leakage and contamination of the surgical field. Because the device is widely used by anesthesia, it is readily available and does not add any extra cost.

Uncultured adipose-derived regenerative cells (ADRCs) seeded in collagen scaffold improves dermal regeneration, enhancing early vascularization and structural organization following thermal burns.

OBJECTIVE: Advances in tissue engineering have yielded a range of both natural and synthetic skin substitutes for burn wound healing application. Long-term viability of tissue-engineered skin substitutes requires the formation and maturation of neo-vessels to optimize survival and biointegration after implantation. A number of studies have demonstrated the capacity of Adipose Derived Regenerative Cells (ADRCs) to promote angiogenesis and modulate inflammation. On this basis, it was hypothesized that adding ADRCs to a collagen-based matrix (CBM) (i.e. Integra) would enhance formation and maturation of well-organized wound tissue in the setting of acute thermal burns. The purpose of this study was to evaluate whether seeding uncultured ADRCs onto CBM would improve matrix properties and enhance healing of the grafted wound. METHODS: Full thickness thermal burns were created on the backs of 8 Gottingen mini-swine. Two days post-injury wounds underwent fascial excision and animals were randomized to receive either Integra seeded with either uncultured ADRCs or control vehicle. Wound healing assessment was performed by digital wound imaging, histopathological and immunohistochemical analyses. RESULTS: In vitro analysis demonstrated that freshly isolated ADRCs adhered and propagated on the CBM. Histological scoring revealed accelerated maturation of wound bed tissue in wounds receiving ADRCs-loaded CBM compared to vehicle-loaded CBM. This was associated with a significant increase in depth of the wound bed tissue and collagen deposition (p<0.05). Blood vessel density in the wound bed was 50% to 69.6% greater in wounds receiving ADRCs-loaded CBM compared to vehicle-loaded CBM (p=0.05) at day 14 and 21. In addition, ADRCs delivered with CBM showed increased blood vessel lumen area and blood vessel maturation at day 21(p=0.05). Interestingly, vascularity and overall cellularity within the CBM were 50% and 45% greater in animals receiving ADRC loaded scaffolds compared to CBM alone (p<0.05). CONCLUSIONS: These data demonstrate that seeding uncultured ADRCs onto CBM dermal substitute enhances wound angiogenesis, blood vessel maturation and matrix remodeling.

Reliability of photographic analysis of wound epithelialization assessed in human skin graft donor sites and epidermolysis bullosa wounds.

BACKGROUND: In many clinical trials on cutaneous healing, wound closure is the primary endpoint and single most important outcome parameter, making precise assessment of this time point one of utmost importance. The assessment of wound closure can be performed either by subjective clinical inspection or with a variety of methodologies anticipated to provide more objective data. The aim of this study was to examine intra- and interrater variability of blinded photographic analysis of wound closure of human partial thickness wounds, as well as the reliability of remote photographic analysis of wounds with that of direct clinical assessment. METHODS: Two plastic surgeons, a dermatologist, and a maxillofacial surgeon constituted our rater panel. High-resolution images of patient wounds derived from two randomized controlled clinical trials (EU Clinical Trials Register numbers EudraCT 2009-017418-56 (registered 12 January 2010) and EudraCT 2010-019945-24 (registered 13 July 2010)) were individually assessed by the blinded, experienced study raters. The reliability of photographic image analysis was tested using intraclass and interclass correlation. The validity of photographic image analysis was correlated with clinical assessments of documented time to heal from the study centers' files. RESULTS: The results demonstrated that the mean intraclass correlation coefficient of all four examiners was excellent (r = 0.79; 95% confidence interval (CI), 0.61, 1.00)). The interrater correlation coefficient was good (r = 0.67; 95% CI, 0.57, 1.00)) and therefore acceptable. The agreement between remote visual assessment and clinical assessment at the time of healing was good (r = 0.64; 95% CI, 0.52, 0.76)) with an overall difference of about 1 day. CONCLUSIONS: Remote photographic analysis of cutaneous wounds is a feasible instrument in clinical open-label studies to evaluate time to wound closure. We found that it was a reliable method of measuring wound closure that correlated satisfactorily with clinical judgment, bolstering the potential relevance in the current era of evolving application and dependency in the field of telemedicine. TRIAL REGISTRATION: EU Clinical Trials Register EudraCT numbers 2009-017418-56 (date of registration: 12 January 2010) and 2010-019945-24 (date of registration: 13 July 2010).

Reduction of diabetic foot ulcer healing times through use of advanced treatment modalities.

Diabetic wounds are a major health care problem associated with delayed healing and high amputation rates. This review systematically evaluated newer wound care therapies for the treatment of diabetic wounds. More recent means of approaching diabetic foot ulcers include various dressings, off-loading shoes, and bioengineered skin constructs and growth factors. Electrical stimulation, phototherapy, electromagnetic fields, and shockwave therapy have been further proposed as potential treatments. A brief overview of these treatments is presented using peer-reviewed evidenced-based literature. A review of the literature demonstrated that treatment of diabetic wounds has focused on either prevention of the wounds in the form of off-loading shoes or adequate protective dressings or on direct treatment of wounds with bioengineered skin constructs, growth factors, or medical devices that accelerate wound healing. The authors' conclusion, following extensive literature review, is that although excellent national and international guidelines exist regarding suggested approaches to the treatment of the diabetic foot ulcer, there is no definitive or universal consensus on the choice of specific treatment modalities. The importance of optimizing comorbidities and the disease state, hemodynamics, local and peripheral skin and wound care, and metabolic challenges while reducing biological and bacterial burden and minimizing trauma remain the primary approach, followed by choice of the most appropriate treatment material or product.

The direction of optimal skin incisions derived from striae distensae.

BACKGROUND: In an effort to achieve inconspicuous scars, plastic surgeons try to place their incisions in established creases and folds of skin. Although well established in the face and abdomen, these folding lines are often disputable on other parts of the body. Striae distensae always develop perpendicular to lines of tension, and their direction can be used to determine optimal incision lines. METHODS: The authors examined photographs of 213 individuals with striae, and a composite diagram was created. This composite along with descriptions of Langer lines, Pinkus main folding lines, and Kraissl lines were compared with a clinical scar revision database and 276 images of incisions and scars from the Internet. RESULTS: Pinkus described the main folding lines in 1927 and Kraissl in 1951 recommended that incision lines be placed perpendicular to the direction of underlying muscles. Both references bear some similarities to what we noted in our composites. In comparison, Langer lines, although of historical interest, poorly predicted the direction of optimal skin incisions. CONCLUSIONS: The optimal direction for surgical skin incisions should take into strong consideration patterns defined by nature's striae distensae, which always develop perpendicular to skin tension lines. Main folding lines can be used as guides when addressing or refining problem scars and similarly facilitate surgical planning of elective incisions, which may prevent problem scar formation for our patients.

Stiff muscle fibers in calf muscles of patients with cerebral palsy lead to high passive muscle stiffness.

Cerebral palsy (CP), caused by an injury to the developing brain, can lead to alterations in muscle function. Subsequently, increased muscle stiffness and decreased joint range of motion are often seen in patients with CP. We examined mechanical and biochemical properties of the gastrocnemius and soleus muscles, which are involved in equinus muscle contracture. Passive mechanical testing of single muscle fibers from gastrocnemius and soleus muscle of patients with CP undergoing surgery for equinus deformity showed a significant increase in fiber stiffness (p<0.01). Bundles of fibers that included their surrounding connective tissues showed no stiffness difference (p=0.28).). When in vivo sarcomere lengths were measured and fiber and bundle stiffness compared at these lengths, both fibers and bundles of patients with CP were predicted to be much stiffer in vivo compared to typically developing (TD) individuals. Interestingly, differences in fiber and bundle stiffness were not explained by typical biochemical measures such as titin molecular weight (a giant protein thought to impact fiber stiffness) or collagen content (a proxy for extracellular matrix amount). We suggest that the passive mechanical properties of fibers and bundles are thus poorly understood.